Polyoxometalates Comprising Noble Metals and Metal Cluster Units Thereof
20230044129 · 2023-02-09
Inventors
- Ali S. Mougharbel (Bremen, DE)
- Helge Jaensch (Grimbergen, BE)
- Ananthu Rajan (Bremen, DE)
- Saurav Bhattacharya (Bremen, DE)
- Ulrich Kortz (Bremen, DE)
Cpc classification
C01G41/006
CHEMISTRY; METALLURGY
C01G55/002
CHEMISTRY; METALLURGY
C01P2002/76
CHEMISTRY; METALLURGY
Y02E60/36
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
B01J27/188
PERFORMING OPERATIONS; TRANSPORTING
C07F17/02
CHEMISTRY; METALLURGY
C01G5/006
CHEMISTRY; METALLURGY
C01P2002/77
CHEMISTRY; METALLURGY
C01P2002/88
CHEMISTRY; METALLURGY
International classification
C07F17/02
CHEMISTRY; METALLURGY
Abstract
The invention relates to polyoxometalates represented by the formula (A.sub.n)m.sup.+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m− or solvates thereof, corresponding supported polyoxometalates, and processes for their preparation, as well as corresponding metal cluster units, optionally in the form of a dispersion in a liquid carrier medium or immobilized on a solid support, and processes for their preparation, as well as their use in conversion of organic substrate.
Claims
1. Polyoxometalate represented by the formula
(A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m− or solvates thereof, wherein each A independently represents a cation, n is the number of cations, each M is independently selected from the group consisting of Pd, Pt, Rh, Ir, Ag and Au, each X is independently selected from the group consisting of P, As, Se and Te, each R is independently selected from the group consisting of monovalent anions, each R′ is independently selected from the group consisting of organometallic ligands, s is a number from 2 to 12, y is a number from 0 to 24, q is a number from 0 to 24, z is a number selected from 0 or 1, t is a number selected from 0 or 1, r is a number selected from 0, 1 or 2, and m is a number representing the total positive charge m+ of n cations A and the corresponding negative charge m− of the polyanion [(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].
2. The polyoxometalate according to claim 1, wherein X.sub.8W.sub.48+rO.sub.184+4r forms a {X.sub.8W.sub.48+rO.sub.184+4r} unit and wherein the {X.sub.8W.sub.48+rO.sub.184+4r} unit has a central cavity, with the proviso that, if r is 0, the {X.sub.8W.sub.48O.sub.184} unit is a cyclic fragment consisting of 4 X.sub.2W.sub.12-based units, wherein each X.sub.2W.sub.12-based unit is bonded to two adjacent X.sub.2W.sub.12-based units via 4 O atoms, wherein each of said 4 O atoms is bonded to a different W atom of each X.sub.2W.sub.12-based unit and wherein every two X.sub.2W.sub.12-based units are linked to each other by 2 of said 4 O atoms, wherein in the {X.sub.8W.sub.48O.sub.184} unit each X is linked to 6 different W via a 1 O atom bridge, respectively, and wherein each X is bonded to 4 O and each W is bonded to 6 O, in particular wherein the {X.sub.8W.sub.48O.sub.184} unit is represented by the following formula 1 wherein each O is presented in small Black dots, each W is presented in dark Gray spheres and each X is presented in light Gray sphere, with the proviso that, if r is 1, the {X.sub.8W.sub.48+1O.sub.184+4} unit comprises the {X.sub.8W.sub.48O.sub.184} unit and the one extra tungsten atom occupies one of the vacant sites in the cavity of the {X.sub.8W.sub.48O.sub.184} unit, or with the proviso that, if r is 2, the {X.sub.8W.sub.48+2O.sub.184+8} unit comprises the {X.sub.8W.sub.48O.sub.184} unit and the two extra tungsten atoms occupy two of the vacant sites in the cavity of the {X.sub.8W.sub.48O.sub.184} unit.
3. The polyoxometalate according to claim 1, wherein all M are Ir, Rh, Pd or Pt or wherein M is a mixture of Pd and Pt, and X is P or As, wherein s is 2, 4 or 6, r is 0 or 1, and z is 0.
4. The polyoxometalate according to claim 1, wherein t is 1, and R′ is selected from the group of arenes.
5. The polyoxometalate according to claim 1, wherein each R is independently selected from the group consisting of F, Cl, Br, I, CN, N.sub.3, CP, FHF, SH, SCN, NCS, SeCN, CNO, NCO and OCN and wherein, each A is independently selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Hf, Re, Os, Ir, Pt, Au, Hg, lanthanide metal, actinide metal, Al, Ga, In, Tl, Sn, Pb, Sb, Bi, phosphonium, ammonium, guanidinium, tetraalkylammonium, protonated aliphatic amines, protonated aromatic amines or combinations thereof.
6. The polyoxometalate according to claim 1, represented by the formula
(A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−.wH.sub.2O wherein w represents the number of attracted water molecules per polyanion [(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)], and ranges from 1 to 180.
7. The polyoxometalate according to claim 1, wherein the polyoxometalate is in the form of a solution-stable polyanion.
8. Process for the preparation of the polyoxometalate of claim 1, said process comprising: (a) reacting at least one source of M and at least one source of {X.sub.8W.sub.48+rO.sub.184+4r} and optionally at least one source of R and/or R′ to form a salt of the polyanion [(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184′4r)].sup.m− or a solvate thereof, (b) optionally adding at least one salt of A to the reaction mixture of step (a) to form a polyoxometalate (A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m− or a solvate thereof, and (c) recovering the polyoxometalate or solvate thereof.
9. The process according to claim 8, wherein the at least one source of {X.sub.8W.sub.48+rO.sub.184+4r} is an X.sub.2W.sub.12-based species, an X.sub.4W.sub.24-based species, an X.sub.8W.sub.48-based species, or a combination thereof, wherein the X.sub.2W.sub.12-based species and/or the X.sub.4W.sub.24-based species form an X.sub.8W.sub.48-based species in situ.
10. Supported polyoxometalate comprising the polyoxometalate according to claim 1, on a solid support.
11. (canceled)
12. Metal cluster unit of the formula
(A′.sub.n′).sup.m+[M.sup.0.sub.s(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m′−, wherein each A′ independently represents a cation, n′ is the number of cations, each M.sup.0 is independently selected from the group consisting of Pd.sup.0, Pt.sup.0, Rh.sup.0, Ir.sup.0, Ag.sup.0, and Au.sup.0, each X is independently selected from the group consisting of P, As, Se and Te, s is a number from 2 to 12, r is 0, 1 or 2, and m′ is a number representing the total positive charge m′+ of n′ cations A′ and the corresponding negative charge m′− of the metal cluster unit anion [M.sup.0.sub.s(X.sub.8W.sub.48+rO.sub.184+4r)].
13. The metal cluster unit according to claim 12, wherein all X are the same and are P or As; all M.sup.0 are the same and all M.sup.0 are Pd.sup.0 or Pt.sup.0 or Rh.sup.0 or Ir.sup.0, or wherein all M are selected from mixtures of Pd.sup.0 and Pt.sup.0; s is 2, 4, 6, 8 or 12 and r is 0 or 1.
14. The metal cluster unit according to claim 12, wherein the metal cluster unit is in the form of particles.
15. The metal cluster unit according to claim 12, wherein the metal cluster unit is dispersed in a liquid carrier medium thereby forming a dispersion of metal cluster unit in said liquid carrier medium.
16. The metal cluster unit according to claim 12, wherein the metal cluster unit is immobilized on a solid support thereby forming supported metal cluster unit.
17-20. (canceled)
Description
BRIEF DESCRIPTION OF THE FIGS. 1-31
[0111]
[0112]
[0113]
[0114]
[0115]
[0116]
[0117]
[0118]
[0119]
[0120]
[0121]
[0122]
[0123]
[0124]
[0125]
[0126]
[0127]
[0128]
[0129]
[0130]
[0131]
[0132]
[0133]
[0134]
[0135]
[0136]
[0137]
DETAILED DESCRIPTION
[0138] According to one embodiment, the POMs of the present invention are represented by the formula
(A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.y(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−
or solvates thereof, wherein [0139] each A independently represents a cation, preferably each A is independently selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Hf, Re, Os, Ir, Pt, Au, Hg, lanthanide metal, actinide metal, Al, Ga, In, Tl, Sn, Pb, Sb, Bi, phosphonium, ammonium, guanidinium, tetraalkylammonium, protonated aliphatic amines, protonated aromatic amines or combinations thereof; more preferably from the group consisting of Li, K, Na and combinations thereof, [0140] n is the number of cations, [0141] each M is independently selected from the group consisting of Pd, Pt, Rh, Ir, Ag and Au, preferably Pd, Pt, Rh, and Ir, more preferably Pd, Pt and Rh, most preferably Pd and Pt, in particular Pd, [0142] each X is independently selected from the group consisting of P, As, Se and Te, preferably P and As, more preferably As.sup.V and P.sup.V, in particular P, preferably P.sup.V, [0143] each R is independently selected from the group consisting of monovalent anions, [0144] each R′ is independently selected from the group consisting of organometallic ligands, preferably arenes, more preferably benzene (Bz), p-cymene, cyclopentadiene (Cp), or pentamethylcyclopentadiene (Cp*), in particular cyclopentadiene (Cp) or pentamethylcyclopentadiene (Cp*), such as pentamethylcyclopentadiene (Cp*), [0145] s is a number from 2 to 12, in particular s is 2, 4, 6, 8, 10 or 12; preferably s is 2, 4, 6, 8 or 12; more preferably s is 2, 4, 6 or 12; most preferably s is 2, 4 or 6, [0146] y is a number from 0 to 24, in particular y is 0, 2, 4, 6, 8, 10, 12 or 24, preferably y is 0, 2, 4, 6, 8 or 12; more preferably y is 0, 2, 4, 6 or 8; more preferably wherein y is 0, 2, 4 or 8, most preferably y is 0, [0147] t is a number selected from 0 or 1, [0148] r is a number selected from 0, 1 or 2, preferably r is 0 or 1, more preferably r is 0, and [0149] m is a number representing the total positive charge m+ of n cations A and the corresponding negative charge m− of the polyanion [(MR′.sub.t).sub.sO.sub.y(X.sub.8W.sub.48+rO.sub.184+4r)].
[0150] According to a second embodiment, the POMs of the present invention are represented by the formula
(A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−
or solvates thereof, wherein [0151] the A, n, m, M, R′, X, s, y, t and r are the same as defined above, [0152] each R is independently selected from the group consisting of monovalent anions, preferably each R is independently selected from the group consisting of F, Cl, Br, I, CN, N.sub.3, CP, bifluoride (FHF), SH, SCN, NCS, SeCN, CNO, NCO and OCN, more preferably F, Cl, Br, I, CN, and N.sub.3, more preferably Cl, Br, I and N.sub.3, most preferably Cl, Br and I, in particular R is Cl, and [0153] z is a number selected from 0 or 1, in particular z is 1, in particular z is 0.
[0154] According to a third embodiment, the POMs of the present invention are represented by the formula
(A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−
or solvates thereof, wherein [0155] A, n, m, M, R′, X, R, s, y, t, r and z are the same as defined above, and [0156] q is a number from 0 to 24, preferably q is 0 to 18, more preferably q is 0 to 12; more preferably q is 0 to 10; most preferably q is 0 to 8, in particular q is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or 24, more particularly q is 0, 1, 2, 3, 4, 5, 6, 7, 8 or 12; even more particularly q is 0, 2, 4, 5, 6, 7 or 8; for instance q is 2 or 4.
[0157] In one preferred variant of the first, second or third embodiments, X.sub.8W.sub.48+rO.sub.184+4r preferably forms a {X.sub.8W.sub.48+rO.sub.184+4r} unit having a central cavity, wherein the {X.sub.8W.sub.48+rO.sub.184+4r} unit is a {X.sub.8W.sub.48O.sub.184} unit for r being 0, a {X.sub.8W.sub.48+1O.sub.184+4} unit for r being 1 and a {X.sub.8W.sub.48+2O.sub.184+8} unit for r being 2. Preferably, the {X.sub.8W.sub.48O.sub.184} unit is represented by the following formula 1
wherein each O is presented in small Black dots, each W is presented in dark Gray spheres and each X is presented in light Gray sphere. The {X.sub.8W.sub.48O.sub.184} unit is a wheel-shaped unit, in particular a cyclic fragment consisting of 4 X.sub.2W.sub.12-based units, in particular 4 X.sub.2W.sub.12O.sub.44 units, wherein each X.sub.2W.sub.12-based unit (X.sub.2W.sub.12O.sub.44 unit) is bonded to two adjacent X.sub.2W.sub.12-based units (X.sub.2W.sub.12O.sub.44 units) via 4 O atoms, wherein each of said 4 O atoms is bonded to a different W atom of each X.sub.2W.sub.12-based unit (X.sub.2W.sub.12O.sub.44 unit) and wherein every two X.sub.2W.sub.12-based units (X.sub.2W.sub.12O.sub.44 units) are linked to each other by 2 of said 4 O atoms, wherein in the {X.sub.8W.sub.48O.sub.184} unit each X is linked to 6 different W via a 1 O atom bridge, respectively, and wherein each X is bonded to 4 O and each W is bonded to 6 O. In the {X.sub.8W.sub.48O184} unit, 16 W atoms are directed towards the central cavity, each of said 16 W atoms is bonded to a different O atom, wherein these 16 O atoms are directed further towards the central cavity such that the outer boundaries of the central cavity are designated by said 16 O atoms, which 16 O atoms are denoted the 16 inner O atoms in the context of the present invention. Preferably at least one of the M atoms is bonded to the 16 inner O atoms, wherein each of the 16 inner O atoms is bonded to no more than one of the M atoms; more preferably at least one of the M atoms is bonded to two of the 16 inner O atoms; more preferably at least one of the M atoms is bonded to two adjacent O atoms of the 16 inner O atoms, most preferably at least one of the M atoms is bonded to two adjacent O atoms of the 16 inner O atoms, wherein each two adjacent O atoms of the 16 inner O atoms can be assigned to a different, i.e., adjacent, X.sub.2W.sub.12-based unit (X.sub.2W.sub.12O.sub.44 unit). More preferably, in case s is 8 or less than 8, all of the M atoms are bonded to the 16 inner O atoms, wherein each of the 16 inner O atoms is bonded to no more than one of the M atoms; more preferably each of the M atoms is bonded to two of the 16 inner O atoms; more preferably each of the M atoms is bonded to two adjacent O atoms of the 16 inner O atoms, most preferably each of the M atoms is bonded to two adjacent O atoms of the 16 inner O atoms, wherein each two adjacent O atoms of the 16 inner O atoms can be assigned to a different, i.e., adjacent, X.sub.2W.sub.12-based unit (X.sub.2W.sub.12O.sub.44 unit). More preferably, in case s is greater than 8, 8 of the M atoms are bonded to the 16 inner O atoms, wherein each of the 16 inner O atoms is bonded to no more than one of the M atoms; more preferably each of said 8 M atoms is bonded to two of the 16 inner O atoms; more preferably each of said 8 M atoms is bonded to two adjacent O atoms of the 16 inner O atoms, most preferably each of said 8 M atoms is bonded to two adjacent O atoms of the 16 inner O atoms, wherein each two adjacent O atoms of the 16 inner O atoms can be assigned to a different, i.e., adjacent, X.sub.2W.sub.12-based unit (X.sub.2W.sub.12O.sub.44 unit). In case r is 1 or 2, preferably the one or two extra tungsten atoms are in the form of WO.sub.4, in particular WO.sub.4.sup.2− groups, preferably occupying respectively one or two of the vacant sites in the cavity of the {X.sub.8W.sub.48O.sub.184} unit as defined above. For instance, if four positions are occupied by noble metals, these one or two extra tungsten atoms are crystallographically disordered over the remaining positions, preferably over the four remaining positions of the overall 8 preferred positions.
[0158] In a preferred embodiment, r is 0.
[0159] In a second preferred variant of the first, second or third embodiments or of the preferred variant of said embodiments, all M are the same; preferably wherein all M are the same, and are selected from Pd, Pt, Rh, and Ir, more preferably Pd, Pt and Rh, most preferably Pd and Pt, in particular Pd. In the alternative, all M are selected from mixtures of Pd and Pt.
[0160] In a third preferred variant of the first, second or third embodiments or of the first or second preferred variant of said embodiments, the {X.sub.8.sup.W.sub.48+rO.sub.184+4r} unit, in particular the {X.sub.8W.sub.48O.sub.184} unit, has a central cavity and all M atoms are located in said central cavity and at least some of the M atoms are bonded to O atoms of the {X.sub.8W.sub.48+rO.sub.184+4r} unit, in particular the {X.sub.8W.sub.48O.sub.184} unit, wherein said O atoms of the {X.sub.8W.sub.48+rO.sub.184+4r} unit, in particular the {X.sub.8W.sub.48O.sub.184}, are directed towards the central cavity, more preferably said O atoms of the {X.sub.8W.sub.48+rO.sub.184+4r} unit, in particular the {X.sub.8W.sub.48O.sub.184} unit, are the 16 inner O atoms. In this variant, in case z is 1, it is further preferred that R is located in the center of the central cavity and R is coordinated to at least one of the M atoms. In this variant, in case z is 0, it is further possible that the center of the central cavity may be occupied by a hydroxide anion OH.sup.− being formed by one of the y O atoms and one of the q H atoms and said hydroxide anion OH.sup.− is coordinated to at least one of the M atoms.
[0161] In a preferred embodiment, the central cavity has a diameter of 6 to 16 Å, more preferably 8 to 14 Å, in particular around 12 Å.
[0162] In a preferred embodiment, in the {X.sub.8W.sub.48+rO.sub.184+4r} unit all of the 184+4r O have an oxidation state of −2, all of the 48+r W have an oxidation state of +6 and all of the 8 X have an oxidation state of +5, in particular X is selected from the group consisting of P.sup.V and As.sup.V, preferably P.sup.V. Preferably, the {X.sub.8W.sub.48O.sub.184} unit has a negative charge of −40, the {X.sub.8W.sub.48+1O.sub.184+4} unit has a negative charge of −42 and the {X.sub.8W.sub.48+2O.sub.184+8} unit has a negative charge of −44.
[0163] In a preferred embodiment, the noble metal-containing POMs are based on noble metal centers M wherein each M has a d.sup.6, d.sup.8 or d.sup.10 valence electron configuration. Based on the d.sup.6, d.sup.8 or d.sup.10 valence electron configuration, the oxidation state of the respective M can be identified, so that M is Rh.sup.III, Ir.sup.III, Pd.sup.IV or Pt.sup.IV, Rh.sup.I, Ir.sup.I, Pd.sup.II, Pt.sup.II, Ag.sup.III or Au.sup.III, and Ag.sup.I or Au.sup.I, respectively. Hence the requirement for M having a d.sup.6, d.sup.8 or d.sup.10 valence electron configuration is synonymous to M being selected from the group consisting of Rh.sup.III, Ir.sup.III, Pd.sup.IV or Pt.sup.IV, Rh.sup.I, Ir.sup.I, Pd.sup.II, Pt.sup.II, Ag.sup.III or Au.sup.II, and Ag.sup.I or Au.sup.I, respectively. In a more preferred embodiment, the noble metal-containing POMs are based on square planar noble metal centers M wherein each M has a d.sup.6, d.sup.8 or d.sup.10 valence electron configuration.
[0164] In the POMs according to the present invention, in which t is 1, each R′ is independently selected from the group consisting of organometallic ligands, preferably arenes, more preferably benzene (Bz), p-cymene, cyclopentadiene (Cp), or pentamethylcyclopentadiene (Cp*), in particular cyclopentadiene (Cp) or pentamethylcyclopentadiene (Cp*), such as pentamethylcyclopentadiene (Cp*), most preferably each R′ is bonded to one or more M in the form of an organometallic bond, preferably in the form of at least one M-arene organometallic bond, more preferably in the form of at least one M-benzene (M-Bz), M-p-cymene, M-cyclopentadiene (M-Cp), or M-pentamethylcyclopentadiene (M-Cp*) organometallic bond, in particular in the form of M-cyclopentadiene (M-Cp) or M-pentamethylcyclopentadiene (M-Cp*) organometallic bond, such as in the form of M-pentamethylcyclopentadiene (M-Cp*) organometallic bond. In an especially preferred embodiment, all R′ are the same. Without wishing to be bound by any theory, the organometallic ligand R′ when being attached to the metal M increases its reactivity towards the POM. In most cases, it has been noted that for M being Rh and Ir, only complexes with Rh.sup.III and Ir.sup.III lead to the formation of the POMs as shown above. In case of using organometallic Rh.sup.I and Ir.sup.I complexes, in some cases, they tend to be oxidized under the typical reaction conditions leading to the formation of the inorganic Rh and Ir, in particular Rh.sub.4P.sub.8W.sub.48 and Ir.sub.2P.sub.8W.sub.48, derivatives.
[0165] In a preferred embodiment, z is 0. In case the {X.sub.8W.sub.48+rO.sub.184+4r} unit, in particular in the {X.sub.8W.sub.48O.sub.184} unit, has a central cavity, in this embodiment, the only atoms being located in the central cavity and having a negative oxidation state are one or more oxygen atom, preferably originating from the y O atoms.
[0166] In a preferred embodiment, y is 0. In another preferred embodiment, in which y is at least 1, i.e., y is a number from 1 to 24, in particular y is 2, 4, 6, 8, 10, 12 or 24, preferably y is 2, 4, 6, 8 or 12; more preferably y is 2, 4, 6 or 8; more preferably wherein y is 2, 4, or 8, most preferably y is 4 or 8, the y O atoms are located within the polyanion. In this case, the y O atoms may be bonded to the M atoms, wherein each of said O atoms may be bonded to one or more of the M atoms, in particular any of the y O atoms may be bonded to 1, 2, 3, 4, 5 or 6 different M atoms, preferably to 1, 2, 3 or 4 different M atoms, more preferably to 1, 2 or 4 different M atoms, most preferably to 4 different M atoms, in particular to 2 M atoms. Additionally or alternatively to being bonded to one or more of the M atoms, in case q is at least 1, any of the y O atoms may be bonded to any of the q H atoms with the proviso that none of the y O atoms is covalently bonded to more than one of the q H atoms.
[0167] In the POMs of the present invention, the cation A can be a Group 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 and 16 metal cation or an organic cation. Preferably, each A is independently selected from the group consisting of cations of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Hf, Re, Os, Ir, Pt, Au, Hg, lanthanide metal, actinide metal, Al, Ga, In, Tl, Sn, Pb, Sb, Bi, phosphonium, ammonium, guanidinium, tetraalkylammonium, protonated aliphatic amines, protonated aromatic amines or combinations thereof. More preferably, A is selected from lithium, potassium, sodium cations and combinations thereof.
[0168] The number n of cations is dependent on the nature of cation(s) A, namely its/their valence, and the negative charge m of the polyanion which has to be balanced. In any case, the overall charge of all cations A is equal to the charge of the polyanion. In turn, the charge m of the polyanion is dependent on the nature and oxidation state of the metals M and W, the nature and oxidation state of the heteroatoms X, optionally the nature and oxidation state of R′ and the number of oxygen atoms y and protons q and the presence or absence of the monovalent anion R. Thus, m depends on the oxidation state of the atoms present in the polyanion, e.g., it follows from the oxidation states of O (−2), H (+1), X (preferably +5 for As.sup.V or P.sup.V), M (normally ranging from +1 to +4 such as +4 for Pd.sup.VI or Pt.sup.VI, such as +3 for Rh.sup.III, Ir.sup.III, Ag.sup.III or Au.sup.III, such as +2 for Pd.sup.II or Pt.sup.II, such as +1 for Rh.sup.I, Ag.sup.I or Au.sup.I), R (normally +1), and W (normally +6). In some embodiments, m ranges from 1 to 48, preferably 8 to 40, more preferably 12 to 36, most preferably 16 to 34, in particular 16, 32, 34, 36. In particular, m is 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38. In a preferred embodiment, m is 16, 28, 32, 34, 36, 40, 42 or 44. Thus, n can generally range from 1 to 48, preferably 8 to 40, more preferably 12 to 36, most preferably 16 to 34. In particular, n ranges from 6 to 34 and more particularly is 6, 9, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30 or 32. In a preferred embodiment, n is 16, 28, 32, 34 or 36.
[0169] Generally, A is acting as counterion of the POM and is positioned outside of the polyanion. However, it is also possible that some of the cations A are located within the polyanion. In case the {X.sub.8W.sub.48+rO.sub.184+4r} unit, in particular the {X.sub.8W.sub.48O.sub.184} unit, has a central cavity, it is also possible that some of the cations A are located within the central cavity. Any cation A being located within the polyanion is not selected from the group of noble metals.
[0170] If one or multiple protons are present as counterion(s) in a preferred embodiment, said one or multiple protons q are generally located within the polyanion. In one alternative, said one or multiple protons are acting as counterion(s) of the POM and may be positioned outside or inside the polyanion. In another alternative, said one or multiple protons are located within the polyanion and covalently bonded to oxygen atom(s) of the polyanion with the proviso that no more than one proton is bonded per oxygen. Thus, in case the q H atoms are covalently bonded to O atoms, the q H atoms are covalently bonded to the y O atoms with the proviso that none of the y O atoms is covalently bonded to more than one of the q H atoms, or the q H atoms are covalently bonded to the O atoms of the {X.sub.8W.sub.48+rO.sub.184+4r} unit with the proviso that none of the O atoms of the {X.sub.8W.sub.48+rO.sub.184+4r} unit is covalently bonded to more than one of the q H atoms, or combinations thereof.
[0171] Generally, q is ranging from 0 to 24. In particular, q is 0 or 4. In a preferred embodiment q is 0, i.e. no group H is present. In another embodiment q is 0 to 22, preferably q is 0 to 18, more preferably q is 0 to 12; more preferably q is 0 to 10; most preferably q is 0 to 8, in particular q is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or 24, more particularly q is 0, 1, 2, 6, 4, 5, 6, 7, 8 or 12; even more particularly q is 0, 2, 4, 5, 6, 7 or 8; for example q is 2 or 4. In another embodiment q is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16. In a preferred embodiment of the present invention the q protons are bonded to oxygen atoms of the polyanion. In a particular embodiment each of said protons is bonded to a different oxygen atom of the polyanion. Thus, in this specific preferred embodiment the POM is best represented by the formulae
(A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.(y−q)(OH).sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−, e.g.,
(A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.(y−q)(OH).sub.q(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−, such as
(A.sub.n).sup.m+[(MR′.sub.t).sub.s(OH).sub.q(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−, or
(A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yR.sub.z(X.sub.8W.sub.48+rO.sub.(184+4r−q)(OH).sub.q)].sup.m−, e.g.,
(A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.y(X.sub.8W.sub.48+rO.sub.(184+4r−q)(OH).sub.q)].sup.m−, such as
(A.sub.n).sup.m+[(MR′.sub.t).sub.s(X.sub.8W.sub.48+rO.sub.(184+4r−q)(OH).sub.q)].sup.m−,
or solvates thereof, wherein A, n, m, M, R′, X, R, t, s, y, q, z and r are the same as defined above.
[0172] Thus, in a preferred embodiment, the invention relates to a POM (A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−, wherein r is 0 and X is P.
[0173] Thus, in a preferred embodiment, the invention relates to a POM (A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−, wherein r is 0, X is P and z is 0.
[0174] Thus, in a preferred embodiment, the invention relates to a POM (A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−, wherein r is 0, X is P and s is 2 or 4.
[0175] Thus, in a preferred embodiment, the invention relates to a POM (A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−, wherein r is 0, X is P, y is 0 and z is 0.
[0176] Thus, in a preferred embodiment, the invention relates to a POM (A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−, wherein r is 0, M is Pd.
[0177] Thus, in a preferred embodiment, the invention relates to a POM (A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−, wherein r is 0, M is Pd, z is 0, s is 4 and X is P.
[0178] Thus, in a preferred embodiment, the invention relates to a POM (A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−, wherein r is 0, M is Pt.
[0179] Thus, in a preferred embodiment, the invention relates to a POM (A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−, wherein r is 0, M is Pt, z is 0, s is 2 and X is P.
[0180] Thus, in a preferred embodiment, the invention relates to a POM (A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−, wherein r is 0, M is Ir.
[0181] Thus, in a preferred embodiment, the invention relates to a POM (A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−, wherein r is 0, M is Ir, z is 0, s is 2 and X is P.
[0182] Thus, in a preferred embodiment, the invention relates to a POM (A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−, wherein r is 0, M is Rh.
[0183] Thus, in a preferred embodiment, the invention relates to a POM (A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−, wherein r is 0, M is Rh, z is 0, s is 4 and X is P.
[0184] Suitable examples of POMs according to the invention are represented by the formulae
(A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−, e.g.,
(A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.q(X.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[(MR′.sub.t).sub.sH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[(MR′.sub.t).sub.sH.sub.q(X.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[(MR′.sub.t).sub.s(X.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[(MR′.sub.t).sub.2O.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.m−, such as
(A.sub.n).sup.m+[(MR′.sub.t).sub.2O.sub.yH.sub.q(X.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[(MR′.sub.t).sub.2H.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[(MR′.sub.t).sub.2O.sub.yR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[(MR′.sub.t).sub.2H.sub.q(X.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[(MR′.sub.t).sub.2(X.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[(MR′.sub.t).sub.4O.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.m−, such as
(A.sub.n).sup.m+[(MR′.sub.t).sub.4O.sub.yH.sub.q(X.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[(MR′.sub.t).sub.4H.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[(MR′.sub.t).sub.4O.sub.yR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[(MR′.sub.t).sub.4H.sub.q(X.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[(MR′.sub.t).sub.4(X.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[M.sub.6O.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.m−, such as
(A.sub.n).sup.m+[M.sub.6O.sub.yH.sub.q(X.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[M.sub.6H.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[M.sub.6O.sub.yR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[M.sub.6H.sub.q(X.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[M.sub.6(X.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−, such as
(A.sub.n).sup.m+[(PdCp*).sub.sO.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−, like
(A.sub.n).sup.m+[(PdCp*).sub.2O.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[(PdCp*).sub.4O.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[(PdCp*).sub.6O.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[Pt.sub.sO.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sub.m−, like
(A.sub.n).sup.m+[Pt.sub.2O.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[Pt.sub.4O.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[Pt.sub.6O.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[Ir.sub.sO.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−, like
(A.sub.n).sup.m+[Ir.sub.2O.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[Ir.sub.4O.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[Ir.sub.6O.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[(RhCp*).sub.sO.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−, like
(A.sub.n).sup.m+[(RhCp*).sub.2O.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[(RhCp*).sub.4O.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.m+[(RhCp*).sub.6O.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−,
(A.sub.n).sup.28+[M.sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.28−, such as
(A.sub.28).sup.28+[M.sub.sR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.28−,
(A.sub.14).sup.28+[M.sub.sR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.28−,
(A.sub.n).sup.28+[M.sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.28−,
(A.sub.n).sup.28+[M.sub.4O.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.28−,
(A.sub.n).sup.30+[M.sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.30−, such as
(A.sub.30).sup.30+[M.sub.sR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.30−,
(A.sub.15).sup.30+[M.sub.sR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.30−,
(A.sub.n).sup.30+[M.sub.sO.sub.yH.sub.qR.sub.z(P.sub.8W.sub.48O.sub.184)].sup.30−,
(A.sub.n).sup.30+[M.sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.30−,
(A.sub.n).sup.32+[M.sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.32−, such as
(A.sub.32).sup.32+[M.sub.sR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.32−,
(A.sub.16).sup.32+[M.sub.sR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.32−,
(A.sub.n).sup.32+[M.sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.32−,
(A.sub.n).sup.32+[M.sub.4O.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.32−,
(A.sub.n).sup.32+[M.sub.2O.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.32−,
(A.sub.n).sup.34+[M.sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.34−, such as
(A.sub.34).sup.34+[M.sub.sR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.34−,
(A.sub.17).sup.34+[M.sub.sR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.34−,
(A.sub.n).sup.34+[M.sub.sO.sub.yH.sub.qR.sub.z(P.sub.8W.sub.48O.sub.184)].sup.34−,
(A.sub.n).sup.34+[M.sub.2O.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.34−,
(A.sub.n).sup.36+[M.sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.36−, such as
(A.sub.36).sup.36+[M.sub.sR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.36−,
(A.sub.18).sup.36+[M.sub.sR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.36−,
(A.sub.n).sup.36+[M.sub.sO.sub.yH.sub.qR.sub.z(P.sub.8W.sub.48O.sub.184)].sup.36−,
(A.sub.n).sup.36+[M.sub.2O.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.36−.
[0185] The invention also includes solvates of the present POMs. A solvate is an association of solvent molecules with a POM. Preferably, water is associated with the POMs and thus, the POMs according to the invention can in particular be represented by the formulae
(A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−.wH.sub.2O, e.g.
(A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.q(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[(MR′.sub.t).sub.sH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.(y−q)(OH).sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−.wH.sub.2O, and
(A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yR.sub.z(X.sub.8W.sub.48+rO.sub.(184+4r−q)(OH).sub.q)].sup.m−.wH.sub.2O,
wherein [0186] A, n, m, M, X, R, R′, s, y, r, t and z are the same as defined above, and [0187] w represents the number of attracted water molecules per polyanion [M.sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)] and mostly depends on the type of cations A. In some embodiments w is an integer that ranges from 1 to 180, preferably from 20 to 160, more preferably from 50 to 150, most preferably from 80 to 140.
[0188] The w H.sub.2O molecules are positioned outside of the polyanion. However, it is also possible that some of the w H.sub.2O molecules are located within the polyanion. In case the {X.sub.8W.sub.48+rO.sub.184+4r} unit has a central cavity, it is also possible that some of the w H.sub.2O molecules are located within the central cavity.
[0189] Suitable examples of the POM solvates according to the invention are represented by the formulae
(A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−.wH.sub.2O, e.g.,
(A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.q(X.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[(MR′.sub.t).sub.sH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[(MR′.sub.t).sub.sH.sub.q(X.sub.8W.sub.48 O.sub.184)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[(MR′.sub.t).sub.s(X.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[(MR′.sub.t).sub.2O.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O, such as
(A.sub.n).sup.m+[(MR′.sub.t).sub.2O.sub.yH.sub.q(X.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[(MR′.sub.t).sub.2H.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[(MR′.sub.t).sub.2O.sub.yR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[(MR′.sub.t).sub.2H.sub.q(X.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[(MR′.sub.t).sub.2(X.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[M.sub.4O.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−.wH.sub.2O, such as
(A.sub.n).sup.m+[M.sub.4O.sub.yH.sub.q(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[M.sub.4H.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[M.sub.4O.sub.yR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[M.sub.4H.sub.q(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[M.sub.4(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[(MR′.sub.t).sub.6O.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O, such as
(A.sub.n).sup.m+[(MR′.sub.t).sub.6O.sub.yH.sub.q(X.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[(MR′.sub.t).sub.6H.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[(MR′.sub.t).sub.6O.sub.yR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[(MR′.sub.t).sub.6H.sub.q(X.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[(MR′.sub.t).sub.6(X.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[(MCp*).sub.sO.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O, such as
(A.sub.n).sup.m+[(PdCp*).sub.sO.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O, like
(A.sub.n).sup.m+[(PdCp*).sub.2O.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[(PdCp*).sub.4O.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[(PdCp*).sub.6O.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[Pt.sub.sO.sub.yH.sub.q(P.sub.8W.sub.49O.sub.188)].sup.m−.wH.sub.2O, like
(A.sub.n).sup.m+[Pt.sub.2O.sub.yH.sub.q(P.sub.8W.sub.49O.sub.188)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[Pt.sub.4O.sub.yH.sub.q(P.sub.8W.sub.49O.sub.188)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[Pt.sub.6O.sub.yH.sub.q(P.sub.8W.sub.49O.sub.188)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[Ir.sub.sO.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O, like
(A.sub.n).sup.m+[Ir.sub.2O.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[Ir.sub.4O.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[Ir.sub.6O.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[Rh.sub.sO.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O, like
(A.sub.n).sup.m+[Rh.sub.2O.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[Rh.sub.4O.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O,
(A.sub.n).sup.m+[Rh.sub.6O.sub.yH.sub.q(P.sub.8W.sub.48O.sub.184)].sup.m−.wH.sub.2O,
(A.sub.n).sup.28+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.28−.wH.sub.2O, such as
(A.sub.28).sup.28+[(MR′.sub.t).sub.sR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.28−.wH.sub.2O,
(A.sub.14).sup.28+[(MR′.sub.t).sub.sR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.28−.wH.sub.2O,
(A.sub.n).sup.28+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(P.sub.8W.sub.48O.sub.184)].sup.28−.wH.sub.2O,
(A.sub.n).sup.28+[(MR′.sub.t).sub.4O.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.28−.wH.sub.2O,
(A.sub.n).sup.30+[M.sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.30−.wH.sub.2O, such as
(A.sub.30).sup.30+[M.sub.sR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.30−.wH.sub.2O,
(A.sub.15).sup.30+[M.sub.sR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.30−.wH.sub.2O,
(A.sub.n).sup.30+[M.sub.sO.sub.yH.sub.qR.sub.z(P.sub.8W.sub.48O.sub.184)].sup.30−.wH.sub.2O,
(A.sub.n).sup.30+[M.sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.30−.wH.sub.2O,
(A.sub.n).sup.32+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.32−.wH.sub.2O, such as
(A.sub.32).sup.32+[(MR′.sub.t).sub.sR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.32−.wH.sub.2O,
(A.sub.16).sup.32+[(MR′.sub.t).sub.sR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.32−.wH.sub.2O,
(A.sub.n).sup.32+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(P.sub.8W.sub.48O.sub.184)].sup.32−.wH.sub.2O,
(A.sub.n).sup.32+[(MR′.sub.t).sub.4O.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.32−.wH.sub.2O,
(A.sub.n).sup.32+[(MR′.sub.t).sub.2O.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.32−.wH.sub.2O,
(A.sub.n).sup.34+[M.sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.34−.wH.sub.2O, such as
(A.sub.34).sup.34+[M.sub.sR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.34−.wH.sub.2O,
(A.sub.17).sup.34+[M.sub.sR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.34−.wH.sub.2O,
(A.sub.n).sup.34+[M.sub.sO.sub.yH.sub.qR.sub.z(P.sub.8W.sub.48O.sub.184)].sup.34−.wH.sub.2O,
(A.sub.n).sup.34+[M.sub.2O.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.34−.wH.sub.2O,
(A.sub.n).sup.36+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.36−.wH.sub.2O, such as
(A.sub.36).sup.36+[(MR′.sub.t).sub.sR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.36−.wH.sub.2O,
(A.sub.18).sup.36+[(MR′.sub.t).sub.sR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.36−.wH.sub.2O,
(A.sub.n).sup.36+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(P.sub.8W.sub.48O.sub.184)].sup.36−.wH.sub.2O,
(A.sub.n).sup.36+[(MR′.sub.t).sub.2O.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.36−.wH.sub.2O.
[0190] In an especially preferred embodiment, the POMs provided by the present invention are in the form of a solution-stable polyanion. The POMs of the present invention can also be in the form crystals, e.g. in the form of primary and/or secondary particles. In an especially preferred embodiment, the POMs provided by the present invention are mainly in the form of primary particles (i.e. non-agglomerated primary particles), that is at least 90 wt % of the POMs are in the form of primary particles, preferably at least 95 wt %, more preferably at least 99 wt %, in particular substantially all the POMs particles are in the form of primary particles.
[0191] In a preferred embodiment, w water molecules, if present at all, are not coordinated to protons and/or A cations, while some water molecules may also coordinate to the M cations and/or optional organometallic ligands. In a preferred embodiment, a proportion of the water molecules is not directly attached to the POM framework (A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m− by coordination but rather indirectly by hydrogen-bonding as water of crystallization. Thus, in a preferred embodiment, the attracted w water molecules, if present at all, are coordinated to A cations and/or possibly exhibit weak interactions by hydrogen bonding to protons of the POM and/or the attracted water molecules, if present at all, are water of crystallization and/or are coordinated to M cations and/or optional organometallic ligands.
[0192] In the POMs of the present invention, the guest atoms M may theoretically be replaced or removed without destroying the structural framework of the {X.sub.8W.sub.48+rO.sub.184+4r} unit. However, the present inventors observed that the guest atoms M remain attached to the {X.sub.8W.sub.48+rO.sub.184+4r} unit under a variety of conditions, e.g., in aqueous solution at pH values of 1 to 10, preferably 1 to 8, or in the solid state at temperatures of up to 500° C., preferably 400° C.
[0193] The diameter of the present POMs primary particles has been found to be about 2 nm determined by single-crystal X-ray diffraction analysis.
[0194] Specific examples of structures of specific POMs of the present invention are also illustrated in
[0195] In comparison to most known TMSPs (transition metal-substituted POMs), the present POMs are characterized in that at least a significant proportion of the metal atom positions of the POM is occupied by noble metal atoms selected from Rh, Ir, Pd, Pt, Ag, Au, and mixtures thereof. This is surprising as noble-metal-containing POMs are notoriously difficult to prepare. Firstly, 4d and 5d transition metals, like noble metals, are generally less reactive than 3d transition metals. Secondly, late transition metals, like noble metals, are generally less oxophilic than early transition metals. The latter aspect is already evident from the respective assignment of the chemical elements in question within the Pearson acid-base concept (also known as HSAB concept). Negatively charged oxygen forms hard bases, whereas the noble metals as late 4d and 5d transition metals constitute soft acids when being positively charged. In contrast, positively charged early transition metals, in particular early 3d transition metals, are hard acids and, thus, react faster and form stronger bonds with the hard base oxygen, i.e., are highly oxophilic as opposed to noble metals. For this reason many, if not most, of the known TMSPs contain early transition metals, in particular early 3d transition metals, contrary to the present POMs.
[0196] Furthermore, in contrast to commonly used noble metal catalysts, including the few known noble metal containing POMs/TMSPs, the present POMs are further characterized in that they show a unique combination of (i) exceptionally high catalytic activity and the (ii) ability of being regenerated very efficiently maintaining most, if not all, of their catalytic activity, which is believed to be associated with the absence of any significant degree of loss or sintering of the expensive noble metals in the regeneration step. While the inventors do not wish to be bound by any particular theory, it is believed that the {X.sub.8W.sub.48+rO.sub.184+4r} unit, in particular the {X.sub.8W.sub.48O.sub.184} unit, forms a highly stable and robust shell unit, which accommodates and, thus, protects the noble metal species. The present inventors believe that the {X.sub.8W.sub.48+rO.sub.184+4r} unit, in particular the {X.sub.8W.sub.48O.sub.184} unit, provides a fine balance between shielding the expensive noble metal species in the regeneration step without preventing sufficient access for the substrates to the catalytically active noble metals in the catalytic process step, i.e., the {X.sub.8W.sub.48+rO.sub.184+4r} unit, in particular the {X.sub.8W.sub.48O.sub.184} unit, provides sufficient shielding for the noble metal species to prevent loss and/or sintering in the regeneration step but not so much shielding that the noble metal species would be deprived of their catalytic activity. In fact, the present inventors observed exceptionally high catalytic activities for the present POMs. Without wishing to be bound by any theory, it is believed that the exceptionally high catalytic activity resides in the unique structure of the present POMs as (i) the shell function of the {X.sub.8W.sub.48+rO.sub.184+4r} unit, in particular the {X.sub.8W.sub.48O.sub.184} unit, may provide specific template effects for certain substrates enhancing the catalytic process activity, (ii) careful selection of the noble metal species allows for fine-tuning the desired catalytic activity and (iii) the noble metal atoms being arranged in a well-defined, highly ordered, centrally located and easily accessible structural formation provides for a highly efficient use of most, if not all, of the expensive noble metal centers in the catalytic process. The {X.sub.8W.sub.48+rO.sub.184+4r} unit, in particular the {X.sub.8W.sub.48O.sub.184} unit, imparts not only the unique catalytic activity and regeneratability to the noble metal species, but is also (i) composed of rather inexpensive atom species, (ii) easily accessible by synthesis and (iii) highly stable inter alia allowing for the present POMs to be activated under various conditions (iv) without decomposition, let alone formation of any toxic degradation products.
[0197] In another embodiment, the POMs may be further calcined at a temperature not exceeding the transformation temperature of the POM, i.e. the temperature at which the POMs have been proven to be stable (usually at least 800° C. for the present POMs according to their corresponding TGA). Thus, in a preferred embodiment the POMs of the present invention are thermally stable up to temperatures of at least 800° C. For the calcination, common equipment may be used, that is commercially available. Calcination of the POMs may be conducted under an oxygen containing gas such as air, under vacuum, under hydrogen or under an inert gas such as argon or nitrogen, more preferably under inert gas, most preferably under nitrogen. Calcination may help to activate a POM pre-catalyst by forming active sites. Upon heating, POM salts loose water molecules (of water of crystallization) before they start to transform/decompose, e.g. by oxidation. TGA can be used to study the weight loss of the POM salts, and Differential Scanning Calorimetry (DSC) indicates whether each step is endo- or exothermic. Such measurements may be carried out e.g. under nitrogen gas, air, oxygen or hydrogen.
[0198] In many cases, however, and in particular if the POM is used as a catalyst or pre-catalyst under reductive conditions, drying of the POM without calcination may be sufficient.
[0199] The invention is further directed to a process for preparing POMs according to the invention.
[0200] A process for preparing POMs according to the present invention comprises: [0201] (a) reacting at least one source of M and at least one source of {X.sub.8W.sub.48+rO.sub.184+4r} and optionally at least one source of R and/or R′ to form a salt of the polyanion [(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)] or a solvate thereof, [0202] (b) optionally adding at least one salt of A to the reaction mixture of step (a) to form a polyoxometalate (A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m− or a solvate thereof, and [0203] (c) recovering the polyoxometalate or solvate thereof [0204] wherein A, n, m, M, X, R, R′, s, y, q, r, t and z are the same as defined above.
[0205] In step (a) of said process at least one source of {X.sub.8W.sub.48+rO.sub.184+4r} is used, especially one source of {X.sub.8W.sub.48+rO.sub.184+4r}. Generally, in a preferred embodiment of the present invention, the at least one source of {X.sub.8W.sub.48+rO.sub.184+4r} is an X.sub.2W.sub.12-based species, an X.sub.4W.sub.24-based species, an X.sub.8W.sub.48-based species, or a combination thereof, wherein the X.sub.2W.sub.12-based species and/or the X.sub.4W.sub.24-based species form an X.sub.8W.sub.48-based species in situ. In a preferred embodiment, the X.sub.2W.sub.12-based species forms an X.sub.8W.sub.48-based species in situ by intermediately forming an X.sub.4W.sub.24-based species. In case r is 1 or 2, preferably the one or two extra tungsten atoms are formed by decomposition of the at least one source of {X.sub.8W.sub.48+rO.sub.184+4r}, in particular by decomposition of the X.sub.2W.sub.12-based species, the X.sub.4W.sub.24-based species, or the X.sub.8W.sub.48-based species, preferably by decomposition of the X.sub.4W.sub.24-based species.
[0206] In a preferred embodiment, the at least one source of {X.sub.8W.sub.48+rO.sub.184+4r} is a X.sub.8W.sub.48-based species, in particular a water-soluble [X.sub.8W.sub.48O.sub.184].sup.40− salt, preferably a [X.sub.8W.sub.48O.sub.184].sup.40− salt of lithium, sodium, potassium, hydrogen or a combination thereof, more preferably a [X.sub.8W.sub.48O.sub.184].sup.40− salt of lithium, potassium, hydrogen or a combination thereof, in particular a [X.sub.8W.sub.48O.sub.184].sup.40− salt of a combination of lithium, potassium and hydrogen. In a preferred embodiment, the at least one source of {X.sub.8W.sub.48+rO.sub.184+4r} is K.sub.28Li.sub.5H.sub.7[X.sub.8W.sub.48O.sub.184] as prepared according to Constant (see, e.g., Inorg. Chem. 1985, 24, 4610-4614; Inorg. Synth. 1990, 27, 110).
[0207] In a preferred embodiment, the at least one source of {X.sub.8W.sub.48+rO.sub.184+4r} is a X.sub.4W.sub.24-based species, in particular a water-soluble [X.sub.4W.sub.24O.sub.94].sup.24− salt, preferably a [X.sub.4W.sub.24O.sub.94].sup.24− salt of lithium, sodium, potassium, hydrogen or a combination thereof, more preferably a [X.sub.4W.sub.24O.sub.94].sup.24− salt of lithium, potassium, hydrogen or a combination thereof, in particular a [X.sub.4W.sub.24O.sub.94].sup.24− salt of a combination of lithium, potassium and hydrogen.
[0208] In a preferred embodiment, the at least one source of {X.sub.8W.sub.48+rO.sub.184+4r} is a X.sub.2W.sub.12-based species, in particular a water-soluble [X.sub.2W.sub.12O.sub.48].sup.14− salt, preferably a [X.sub.2W.sub.12O.sub.48].sup.14− salt of lithium, sodium, potassium, hydrogen or a combination thereof, more preferably a [X.sub.2W.sub.12O.sub.48].sup.14− salt of lithium, potassium, hydrogen or a combination thereof, in particular a [X.sub.2W.sub.12O.sub.48].sup.14− salt of a combination of lithium, potassium and hydrogen. In a preferred embodiment, the at least one source of {X.sub.8W.sub.48+rO.sub.184+4r} is a X.sub.2W.sub.12-based species being a water-soluble [X.sub.2W.sub.12O.sub.48].sup.14− salt in situ generated from a [X.sub.2W.sub.18O.sub.62].sup.6− salt, in particular a [X.sub.2W.sub.18O.sub.62].sup.6− salt of lithium, sodium, potassium, hydrogen or a combination thereof.
[0209] In another embodiment, the at least one source of {X.sub.8W.sub.48+rO.sub.184+4r} is a combination of at least one source of W, in particular at least one source of W.sup.VI, at least one source of O, in particular at least one source of O.sup.−II, at least one source of X, in particular at least one source of X.sup.V, preferably at least one source of P.sup.V or As.sup.V, more preferably at least one source of P.sup.V, wherein the conditions in step (a) are such that the {X.sub.8W.sub.48+rO.sub.184+4r} unit is formed.
[0210] In step (a) of said process at least one source of M is used, especially one source of M. Generally, in a preferred embodiment of the present invention as source for the noble metal M atoms can be used Pd.sup.II salts such as palladium chloride (PdCl.sub.2), palladium nitrate (Pd(NO.sub.3).sub.2), palladium acetate (Pd(CH.sub.3COO).sub.2) and palladium sulphate (PdSO.sub.4); Pt.sup.II salts such as potassium tetrachloroplatinate (K.sub.2PtCl.sub.4) and platinum chloride (PtCl.sub.2); Rh.sup.I salts such as [(C.sub.6H.sub.5).sub.3P].sub.2RhCl(CO) and [Rh(CO).sub.2Cl].sub.2, Rh.sup.III salts such as rhodium chloride (RhCl.sub.3), or Rh compounds such as rhodocene ([Rh(Cp).sub.2]), pentamethylcyclopentadienyl rhodium chloride ([Rh(Cp*)Cl.sub.2].sub.2), benzene rhodium chloride ([Rh(Bz)Cl.sub.2].sub.2), p-cymene rhodium chloride ([Rh(p-cymene)Cl.sub.2].sub.2), and rhodium(II) acetate (C.sub.8H.sub.12O.sub.8Rh.sub.2); Ir.sup.I salts such as [(C.sub.6H.sub.5).sub.3P].sub.2IrCl(CO), Ir.sup.III salts such as iridium chloride (IrCl.sub.3), or Ir compounds such as pentamethylcyclopentadienyl iridium chloride ([Ir(Cp*)Cl.sub.2].sub.2), benzene iridium chloride ([Ir(Bz)Cl.sub.2].sub.2), and p-cymene iridium chloride ([Ir(p-cymene)Cl.sub.2].sub.2); Au.sup.III salts such as gold chloride (AuCl.sub.3), or Au sources such as gold hydroxide (Au(OH).sub.3) and chloroauric acid (HAuCl.sub.4.aq); and Ag.sup.III salts preferably generated with oxidizing reagents from Ag.sup.I salts such as silver nitrate (AgNO.sub.3), silver fluoride (AgF) and silver chloride (AgCl). More preferably, the Pd source is PdCl.sub.2 or Pd(CH.sub.3COO).sub.2; the Pt source is K.sub.2PtCl.sub.4; the Rh source is RhCl.sub.3 or [Rh(Cp*)Cl.sub.2].sub.2; and the Ir source is IrCl.sub.3 or [Ir(Cp*)Cl.sub.2].sub.2. In a preferred embodiment the organometallic ligand R′, if present, is introduced in step (a) as a complex with metal M, i.e., the at least one source of M and the at least one source of R′ are the same.
[0211] In step (a) of said process optionally at least one source of R is used, especially one source of R. Generally, in a preferred embodiment of the present invention, salts of the monovalent anions selected from the group consisting of F, Cl, Br, I, CN, N.sub.3, CP, FHF, SH, SCN, NCS, SeCN, CNO, NCO and OCN, more preferably F, Cl, Br, I, CN, and N.sub.3, more preferably Cl, Br, I and N.sub.3, most preferably Cl, Br and I, in particular Cl. Preferably the following cations may be used in the salts: Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Hf, Re, Os, Ir, Pt, Au, Hg, lanthanide metal, actinide metal, Al, Ga, In, Tl, Sn, Pb, Sb, Bi, phosphonium, ammonium, guanidinium, tetraalkylammonium, protonated aliphatic amines, protonated aromatic amines or combinations thereof. More preferably lithium, potassium or sodium, in particular NaCl, LiCl, NaBr, KBr and NaI may be used.
[0212] In a preferred embodiment, step (a) of said process is carried out in an aqueous solution. In a preferred embodiment, minor amounts of organic solvent, such as, 40 to 0.01 vol % based on the total volume of the reaction mixture, preferably 30 to 0.05 vol %, 20 to 0.1 vol %, 10 to 0.2 vol %, 5 to 0.5 vol % or 3 to 1 vol %, may be added to the aqueous solution. In particular, if any of the starting materials has only a low solubility in water it is possible to dissolve the respective starting material in a small volume of organic solvent and then adding this solution to an aqueous solution of the remaining starting materials or vice versa. Examples of suitable organic solvents include, but are not limited to acetonitrile, acetone, toluene, DMF, DMSO, ethanol, methanol, n-butanol, sec-butanol, isobutanol and mixtures thereof. It is also possible to use emulsifying agents to allow the reagents of step (a) of said process to undergo a reaction.
[0213] Furthermore, in a preferred embodiment of the present invention, in step (a) of said process, the concentration of the noble metal ions originating from the at least one source of M ranges from 0.001 to 1 mole/l, preferably from 0.002 to 0.5 mole/l, more preferably from 0.005 to 0.1 mole/l, the concentration of the X.sub.8W.sub.48-based species originating from the sources of {X.sub.8W.sub.48+rO.sub.184+4r} ranges from 0.0001 to 0.1 mole/l, preferably 0.0003 to 0.05 mole/l, more preferably 0.0005 to 0.01 mole/l, optionally the concentration of the R′-containing starting material ranges from 0.001 to 5 mole/l, preferably 0.002 to 0.5 mole/l, more preferably 0.005 to 0.1 mole/l and optionally the concentration of the R-containing starting material ranges from 0.001 to 1 mole/l, preferably 0.002 to 0.5 mole/l, more preferably 0.005 to 0.1 mole/l.
[0214] Furthermore, in a preferred embodiment, the pH of the aqueous solution in step (a) of said process ranges from 1 to 10, preferably from 1.5 to 9 and more preferably from 2 to 8. Most preferably, the pH is from about 3 to about 7, for instance from about 3.5 to about 6.5. Generally, in a preferred embodiment of the present invention a buffer solution can be used for maintaining the pH value in a certain range.
[0215] In a preferred embodiment of the present invention the buffer is a phosphate or acetate buffer or a mixture thereof and preferably said phosphate or acetate buffer is derived from H.sub.3PO.sub.4, NaH.sub.2PO.sub.4, Na.sub.2HPO.sub.4, Na.sub.3PO.sub.4, KH.sub.2PO.sub.4, K.sub.2HPO.sub.4, K.sub.3PO.sub.4, NaKHPO.sub.4, NaK.sub.2PO.sub.4, Na.sub.2KPO.sub.4, Na(CH.sub.3CO.sub.2), K(CH.sub.3CO.sub.2), Mg(CH.sub.3CO.sub.2).sub.2, Ca(CH.sub.3CO.sub.2).sub.2, CH.sub.3CO.sub.2H or mixtures thereof, preferably H.sub.3PO.sub.4, NaH.sub.2PO.sub.4, Na.sub.2HPO.sub.4, Na.sub.3PO.sub.4, Na(CH.sub.3CO.sub.2), K(CH.sub.3CO.sub.2), CH.sub.3CO.sub.2H or mixtures thereof, and most preferably NaH.sub.2PO.sub.4, Na.sub.2HPO.sub.4, Na(CH.sub.3CO.sub.2), Li(CH.sub.3CO.sub.2) or mixtures thereof, in particular NaH.sub.2PO.sub.4, Na(CH.sub.3CO.sub.2) or mixtures thereof. It is more preferred to have either a phosphate or an acetate buffer, whereas it is less preferred to have a mixture of phosphate and acetate buffer. In a preferred embodiment of the present invention said phosphate buffer is preferably derived from NaH.sub.2PO.sub.4, whereas said acetate buffer is preferably derived from Li(CH.sub.3CO.sub.2), Na(CH.sub.3CO.sub.2) or mixtures thereof. In a very preferred embodiment of the present invention the buffer is an acetate buffer and is preferably derived from Li(CH.sub.3CO.sub.2), Na(CH.sub.3CO.sub.2) or mixtures thereof.
[0216] Generally, in an embodiment of the present invention, additional base or acid solution can be used for adjusting the pH to a certain value. It is particularly preferred to use aqueous sodium hydroxide or H.sub.2SO.sub.4 solution having a concentration of 1 M. In another embodiment, the concentration of the aqueous base or acid solution (preferably aqueous sodium hydroxide or H.sub.2SO.sub.4 solution) is from 0.1 to 12 M, preferably 0.2 to 8 M, more preferably from 0.5 to 6 M, most preferably about 1 M. Generally, in a very preferred embodiment of the present invention additional acid solution can be used for adjusting the pH to a certain pH value. It is particularly preferred to use aqueous H.sub.2SO.sub.4 solution having a concentration of 0.1 M. In another embodiment, the concentration of the acid solution (preferably aqueous H.sub.2SO.sub.4 solution) is from 0.1 to 12 M, preferably 0.2 to 8 M, more preferably from 0.5 to 6 M, most preferably about 1 M.
[0217] In the context of the present invention the pH of the aqueous solution in step (a) of said process refers to the pH as measured at the end of the reaction. In the preferred embodiment where e.g. an aqueous sodium hydroxide solution is used for adjusting the pH-value, the pH is measured after the adjustment at the end of the reaction. pH values are at 20° C., and are determined to an accuracy of ±0.05 in accordance with the IUPAC Recommendations 2002 (R. P. Buck et al., Pure Appl. Chem., Vol. 74, No. 11, pp. 2169-2200, 2002).
[0218] A suitable and commercially available instrument for pH measurement is the Mettler Toledo FE20 pH meter. The pH calibration is carried out as 2-point calibration using a pH=4.01 standard buffer solution and a pH=7.00 standard buffer solution. The resolutions are: 0.01 pH; 1 mV; and 0.1° C. The limits of error are: ±0.01 pH; ±1 mV; and ±0.5° C.
[0219] A very preferred embodiment of the present invention is said process, wherein in step (a) the at least one source of M and at least one source of {X.sub.8W.sub.48+rO.sub.184+4r} and optionally at least one source of R and/or R′ are dissolved in a solution of acetate buffer derived from lithium or sodium acetate, preferably an 0.5 to 1.5 M acetate buffer derived from lithium or sodium acetate, in particular a 0.75 to 1.25 M acetate buffer derived from lithium or sodium acetate, and most preferred a 1.0 M acetate buffer derived from lithium or sodium acetate.
[0220] In step (a) of the process of the present invention, further additives may be used. In one embodiment H.sub.2O.sub.2 (preferably 30 wt % in water) is added. Without wishing to be bound by any theory, it is believed that the H.sub.2O.sub.2 (re)oxidizes the metal species to desired oxidation state. In one embodiment propylene oxide is added. Without wishing to be bound by any theory, it is believed that the propylene oxide facilitates the formation of oxygen bridges.
[0221] In a preferred embodiment, in step (a) of the process of the present invention, a perchlorate salt is added as a further additive, preferably lithium or sodium perchlorate or mixtures thereof, in particular lithium perchlorate. Preferably the perchlorate salt is added as a 1 M solution in water. Without wishing to be bound by any theory, it is believed that the perchlorate facilitates solubility.
[0222] Any of the above additives may be used individually or in combination as well as in combination with other additives commonly used in the art.
[0223] In step (a) of the process of the present invention, the reaction mixture is typically heated to a temperature of from 20° C. to 100° C., preferably from 50° C. to 90° C., preferably from 60° C. to 85° C., preferably from 60° C. to 80° C., and most preferably about 75° C.
[0224] In step (a) of the process of the present invention, the reaction mixture is typically heated for about 10 min to about 4 h, more preferably for about 30 min to 2 h, most preferably for about 90 min. Further, it is preferred that the reaction mixture is stirred during step (a).
[0225] With regard to the present invention the term crude mixture relates to an unpurified mixture after a reaction step and is thereby used synonymously with reaction mixture of the preceding reaction step.
[0226] In a preferred embodiment of the process of the present invention, between step (a) and (b), the crude mixture is filtered. Preferably, the crude mixture is filtered immediately after the end of step (a), i.e. immediately after the stirring is turned off, and is then optionally cooled. Alternatively, if applicable the heated crude mixture is cooled first, preferably to room temperature, and subsequently filtered. The purpose of this filtration is to remove solid impurities after step (a). Thus, the product of step (a) remains in the filtrate.
[0227] In a preferred embodiment, in case cation A is not present in the crude mixture or filtrate already, or the concentration of A in the crude mixture or filtrate should be increased, in step (b) of the process, a salt of the cation A can be added to the reaction mixture of step (a) of the process or to its corresponding filtrates to form (A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−. Preferably, the salt of A is added as a solid or in the form of an aqueous solution. The counterions of A can be selected from the group consisting of any stable, non-reducing, water-soluble anion, e.g., halides, nitrate, sulfate, acetate, phosphate. Preferably, the acetate or phosphate salt is used. However, the addition of extra cations A in step (b) of the process is not necessary if the desired cations are already present during step (a) of the process, for example, as a component of the buffer preferably used as solvent in step (a) of the process or a component of any of the sources of {X.sub.8W.sub.48+rO.sub.184+4r}, M or optionally R and/or R′ including, for example, palladium and platinum cations themselves. Preferably, all desired cations are already present during step (a) of the process, so that optional addition of extra cations is not necessary.
[0228] In step (c) of the process of the present invention, the POMs according to the invention or solvates thereof, formed in step (a) or (b) of said process, are recovered. For example, isolation of the POMs or solvates thereof can be effected by common techniques including bulk precipitation or crystallization. In a preferred embodiment of the present invention the POMs are isolated as crystalline or amorphous solids, preferably as crystalline solids. Crystallization or precipitation can be effected by common techniques such as evaporation or partial evaporation of the solvent, cooling, change of solvent, solvents or solvent mixtures, addition of crystallization seeds, etc. In a preferred embodiment the addition of cation A in step (b) of the process can induce crystallization or precipitation of the desired POM (A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−, wherein fractional crystallization is preferable. In a preferred embodiment, fractional crystallization might be accomplished by the slow addition of a specific amount of cation A to the reaction mixture of step (a) of the process or to its corresponding filtrates which might be beneficial for product purity and yield.
[0229] A preferred embodiment of the present invention is such a process wherein water is used as solvent and the at least one source of M is a water-soluble salt of Ir, Rh, Pt or Pd, preferably selected from K.sub.2PtCl.sub.4, PtCl.sub.2, Pd(CH.sub.3COO).sub.2, PdCl.sub.2, Pd(NO.sub.3).sub.2, PdSO.sub.4, IrCl.sub.3, or RhCl.sub.3; and the at least one source of {X.sub.8W.sub.48+rO.sub.184+4r} is K.sub.28Li.sub.5H.sub.7P.sub.8W.sub.48O.sub.184 or K.sub.16Li.sub.2H.sub.6P.sub.4W.sub.24O.sub.94.
[0230] A preferred embodiment of the present invention is such a process wherein water is used as solvent and the at least one source of M is a water-soluble salt of Ir, Rh, Pt or Pd, preferably selected from the group Cp*-containing organometallic complexes of Ir, Rh, Pt or Pd, such as [Ir(Cp*)Cl.sub.2].sub.2 or [Rh(Cp*)Cl.sub.2].sub.2; and the at least one source of {X.sub.8W.sub.48+rO.sub.184+4r} is K.sub.28Li.sub.5H.sub.7P.sub.8W.sub.48O.sub.184 or K.sub.16Li.sub.2H.sub.6P.sub.4W.sub.24O.sub.94.
[0231] A preferred embodiment of the present invention is such a process wherein water is used as solvent containing 1 M lithium or sodium acetate and the at least one source of M is a water-soluble salt of Ir, Rh, Pt or Pd selected from K.sub.2PtCl.sub.4, Pd(CH.sub.3COO).sub.2, IrCl.sub.3, or RhCl.sub.3; and the at least one source of {X.sub.8W.sub.48+rO.sub.184+4r} is K.sub.28Li.sub.5H.sub.7P.sub.8W.sub.48O.sub.184 or K.sub.16Li.sub.2H.sub.6P.sub.4W.sub.24O.sub.94.
[0232] A preferred embodiment of the present invention is such a process wherein water is used as solvent containing 1 M lithium or sodium acetate and the at least one source of M is a water-soluble salt of Ir, Rh, Pt or Pd selected from the group Cp*-containing organometallic complexes of Ir, Rh, Pt or Pd, such as [Ir(Cp*)Cl.sub.2].sub.2 or [Rh(Cp*)Cl.sub.2].sub.2; and the at least one source of {X.sub.8W.sub.48+rO.sub.184+4r} is K.sub.28Li.sub.5H.sub.7P.sub.8W.sub.48O.sub.184 or K.sub.16Li.sub.2H.sub.6P.sub.4W.sub.24O.sub.94.
[0233] A most preferred embodiment of the present invention is a process wherein in step (a) at least one source of M is used and all M are the same, preferably wherein all M are Pd, preferably wherein all M are Pt, preferably wherein all M are Rh, preferably wherein all M are Ir. Another most preferred embodiment of the present invention is a process wherein in step (a) at least one source of M is used and M is a mixture of Pd and Pt.
[0234] According to one embodiment, the present POMs can be immobilized on a solid support. The present invention thus also relates to supported POMs comprising the POMs of the present invention or prepared by the process of the present invention on a solid support. Suitable supports include but are not limited to materials having a high surface area and/or a pore size which is sufficient to allow the POMs to be loaded, e.g., polymers, graphite, carbon nanotubes, electrode surfaces, aluminum oxide and aerogels of aluminum oxide and magnesium oxide, titanium oxide, zirconium oxide, cerium oxide, silicon dioxide, silicates, active carbon, mesoporous materials, like mesoporous silica, such as SBA-15 and MCM-41, zeolites, aluminophosphates (ALPOs), silicoaluminophosphates (SAPOs), metal organic frameworks (MOFs), zeolitic imidazolate frameworks (ZIFs), periodic mesoporous organosilicas (PMOs), and mixtures thereof and modified compounds thereof Preferred supports are, for instance, mesoporous silica, more preferably SBA-15 or MCM-41, most preferably SBA-15. A variety of such solid supports is commercially available or can be prepared by common techniques. Furthermore, there are various common techniques to modify or functionalize solid supports, for example with regard to the size and shape of the surface or the atoms or groups available for bonding on the surface.
[0235] In a preferred embodiment of the present invention the immobilization of the POMs to the surface of the solid support is accomplished by means of adsorption, including physisorption and chemisorption, preferably physisorption. The adsorption is based on interactions between the POMs and the surface of the solid support such as van-der-Waals interactions, hydrogen-bonding interactions, ionic interactions, etc.
[0236] In a preferred embodiment the negatively charged polyanions [(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)] are adsorbed predominantly based on ionic interactions. Therefore, a solid support bearing positively charged groups is preferably used, in particular a solid support bearing groups that can be positively charged by protonation. A variety of such solid supports is commercially available or can be prepared by common techniques. In one embodiment the solid support is functionalized with positively charged groups, preferably groups that are positively charged by protonation, and the negatively charged polyanion [(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)] is linked to said positively charged groups by electrostatic interactions. In a preferred embodiment the solid support, preferably mesoporous silica, more preferably SBA-15 or MCM-41, most preferably SBA-15, is functionalized with moieties bearing positively charged groups, preferably tetrahydrocarbyl ammonium groups, more preferably groups that can be positively charged by protonation, most preferably mono-functionalized amino groups —NH.sub.2. Preferably said groups are attached to the surface of the solid support by covalent bonds, preferably via a linker that comprises one or more, preferably one, of said groups, preferably an alkyl, aryl, alkenyl, alkynyl, hetero-alkyl, hetero-cycloalkyl, hetero-alkenyl, hetero-cycloalkenyl, hetero-alkynyl, hetero-aryl or cycloalkyl linker, more preferably an alkyl, aryl, hetero-alkyl or hetero-aryl linker, more preferably an alkyl linker, most preferably a methylene, ethylene, n-propylene, n-butylene, n-pentylene, n-hexylene linker, in particular a n-propylene linker. Preferably said linkers are bonded to any suitable functional group present on the surface of the solid support, such as to hydroxyl groups. Preferably said linkers are bonded to said functional groups present on the surface of the solid support either directly or via another group or atom, most preferably via another group or atom, preferably a silicon-based group, most preferably a silicon atom. In a most preferred embodiment of the present invention the POMs are supported on (3-aminopropyl)triethoxysilane (apts)-modified SBA-15.
[0237] In the supported POMs of the present invention, the POMs that are immobilized on the solid support are in the form of primary and/or secondary particles. In an especially preferred embodiment, the immobilized POMs particles are mainly in the form of primary particles (i.e. non-agglomerated primary particles), that is at least 90 wt % of the immobilized POMs particles are in the form of primary particles, preferably at least 95 wt %, more preferably at least 99 wt %, in particular substantially all the immobilized POMs particles are in the form of primary particles.
[0238] The invention is further directed to processes for preparing supported POMs according to the invention. Solid supports used in the context of this invention are as defined above. In a preferred embodiment of the present invention the surface of the solid supports is modified with positively charged groups, more preferably groups that can be positively charged by protonation. Those charged solid supports can be prepared by techniques well established in the art, for example by surface modification of a mesoporous silica, such as SBA-15, with a suitable reagent bearing a positively charged group or a group that can be positively charged by protonation, such as 3-aminopropyltriethoxysilane (apts), is conducted by heating, preferably under reflux, under inert gas atmosphere, such as argon or nitrogen, in an inert solvent with a suitable boiling point, such as hexane, heptane or toluene, for a suitable time, such as 4-8 hours, and finally the modified solid support is isolated, preferably by filtration, purified, preferably by washing, and dried, preferably under vacuum by heating, most preferably under vacuum by heating at about 100° C.
[0239] The optionally treated support may be further calcined at a temperature of 500° C. to 800° C. For the calcination, common equipment may be used, that is commercially available. Calcination of the optionally treated support may for instance be conducted under an oxygen containing gas such as air, under vacuum, under hydrogen or under an inert gas such as argon or nitrogen, more preferably under inert gas, most preferably under nitrogen.
[0240] The POMs according to the present invention or prepared by the process of the present invention can be immobilized on the surface of the solid support by contacting said POMs with the solid support. The present invention therefore also relates to a process for the preparation of supported POMs, comprising the step of contacting the POMs provided by the present invention or prepared according to the present invention with the solid support, thereby immobilizing at least part of the POMs onto the support; and optionally isolating the resulting supported POMs.
[0241] Said contacting may be conducted employing common techniques in the art, such as blending both the solid support and the POM in the solid form. In a preferred embodiment the POM is mixed with a suitable solvent, preferably water or an aqueous solvent, and the solid support is added to this mixture. In a more preferred embodiment the solid support is mixed with a suitable solvent, preferably water or an aqueous solvent, and the POM is added to this mixture. In case a solid support with groups that can be positively charged by protonation is used, the mixture is preferably acidified, for instance by addition of H.sub.2SO.sub.4, HNO.sub.3 or HCl, most preferably by addition of H.sub.2SO.sub.4 or HNO.sub.3, so that the pH value of the mixture ranges from 0.1 to 6, preferably from 1 to 4 and more preferably from 1.5 to 3, most preferably about 2. The mixture comprising POM, solid support and solvent is preferably stirred, typically for 1 min to 24 h, more preferably for 30 min to 15 h, more preferably for 1 h to 12 h, most preferably for 6 h to 10 h, in particular about 8 h. While stirring, the mixture may be at a temperature of from 20° C. to 100° C., preferably from 20° C. to 80° C., preferably from 20° C. to 60° C., preferably from 20° C. to 40° C., and most preferably about 25° C. Afterwards, the supported POM can be kept in the solvent as suspension or can be isolated. Isolation of the supported POM from the solvent may be performed by any suitable method in the art, such as by filtration, evaporation of the solvent, centrifugation or decantation, preferably by filtration or removal of the solvent in vacuum, more preferably by filtration. The isolated supported POMs may then be washed with a suitable solvent, preferably water or an aqueous solvent, and dried. Supported POMs may be dried in an oven at a temperature of e.g. about 100° C.
[0242] In another embodiment, the supported POMs may be further calcined at a temperature not exceeding the transformation temperature of the POM, i.e. the temperature at which the POMs have been proven to be stable (usually at least 800° C. for the present POMs according to their corresponding TGA). Thus, in a preferred embodiment the POMs of the present invention are thermally stable up to temperatures of at least 800° C. For the calcination, common equipment may be used, that is commercially available. Calcination of the supported POMs may for instance be conducted under an oxygen containing gas such as air, under vacuum, under hydrogen or under an inert gas such as argon or nitrogen, more preferably under inert gas, most preferably under nitrogen.
[0243] In many cases, however, and in particular if the supported POM is used as a catalyst or pre-catalyst under reductive conditions, drying of the supported POM without calcination may be sufficient.
[0244] In supported POMs, the POM loading levels on the solid support may be up to 30 wt % or even more but are preferably up to 10 wt %, for instance up to 5 wt % or even up to 2 wt %. Accordingly, the POM loading level on the solid support is typically 0.01 to 30 wt %, particularly 0.05 to 20 wt %, more particularly 0.1 to 10 wt %, often 0.2-6 wt %, more often 0.3-5 wt %, and most often 0.5-2 wt %. POM loading levels on the solid support can be determined by elemental analysis such as Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analysis, for instance using a Varian Vista MPX.
[0245] According to one embodiment, the present invention also relates to a metal cluster of the formula
(A′.sub.n′).sup.m′+[M.sup.0.sub.s(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m′−
wherein; [0246] each A′ independently represents a cation, preferably each A′ is independently selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Hf, Re, Os, Ir, Pt, Au, Hg, lanthanide metal, actinide metal, Al, Ga, In, Tl, Sn, Pb, Sb, Bi, phosphonium, ammonium, guanidinium, tetraalkylammonium, protonated aliphatic amines, protonated aromatic amines or combinations thereof; more preferably from the group consisting of Li, K, Na and combinations thereof [0247] n′ is the number of cations, [0248] each M.sup.0 is independently selected from the group consisting of Pd.sup.0, Pt.sup.0, Rh.sup.0, Ir.sup.0, Ag.sup.0, and Au.sup.0, preferably Pd.sup.0, Pt.sup.0, Rh.sup.0, Ir.sup.0, and Au.sup.0, more preferably Pd.sup.0, Pt.sup.0, Ir.sup.0, and Rh.sup.0, most preferably Pd.sup.0 and Pt.sup.0, in particular Pd.sup.0, [0249] each X is independently selected from the group consisting of P, As, Se and Te, preferably P and As, preferably As.sup.V and P.sup.V, in particular P, preferably P.sup.V, [0250] s is a number from 2 to 12, in particulars is 2, 4, 6, 8, 10 or 12; preferably s is 2, 4, 6, 8 or 12; more preferably s is 2, 4, 6 or 12; most preferably s is 2, 4 or 6, [0251] r is a number selected from 0, 1 or 2, preferably r is 0 or 1, more preferably r is 0, and [0252] m′ is a number representing the total positive charge m′+ of n′ cations A′ and the corresponding negative charge m′− of the metal cluster unit anion [M.sup.0.sub.s(X.sub.8W.sub.48+rO.sub.184+4r)].
[0253] In a preferred embodiment, X.sub.8W.sub.48O.sub.184 preferably forms a {X.sub.8W.sub.48+rO.sub.184+4r}′ unit, preferably the {X.sub.8W.sub.48+rO.sub.184+4r}′ unit has a central cavity, wherein the {X.sub.8W.sub.48+rO.sub.184+4r}′ unit is a {X.sub.8W.sub.48O.sub.184}′ unit for r being 0, a {X.sub.8W.sub.48+1O.sub.184+4}′ unit for r being 1 and a {X.sub.8W.sub.48+2O.sub.184+8}′ unit for r being 2. Preferably, wherein r is 0 and X.sub.8W.sub.48O.sub.184 forms a {X.sub.8W.sub.48O.sub.184}′ unit, the {X.sub.8W.sub.48O.sub.184}′ unit in the metal cluster (A′.sub.n′).sup.m′+[M.sup.0.sub.s(X.sub.8W.sub.48O.sub.184)].sup.m′− is represented by the following formula 1
wherein each O is presented in small Black dots, each W is presented in dark Gray spheres and each X is presented in light Gray sphere. The {X.sub.8W.sub.48O.sub.184}′ unit is a cyclic fragment consisting of 4 X.sub.2W.sub.12-based units, in particular 4 X.sub.2W.sub.12O.sub.44 units, wherein each X.sub.2W.sub.12-based unit (X.sub.2W.sub.12O.sub.44 unit) is bonded to two adjacent X.sub.2W.sub.12-based units (X.sub.2W.sub.12O.sub.44 units) via 4 O atoms, wherein each of said 4 O atoms is bonded to a different W atom of each X.sub.2W.sub.12-based unit (X.sub.2W.sub.12O.sub.44 unit) and wherein every two X.sub.2W.sub.12-based units (X.sub.2W.sub.12O.sub.44 units) are linked to each other by 2 of said 4 O atoms, wherein in the {X.sub.8W.sub.48O.sub.184}′ unit each X is linked to 6 different W via a 1 O atom bridge, respectively, and wherein each X is bonded to 4 O and each W is bonded to 6 O. In the {X.sub.8W.sub.48O.sub.184}′ unit, 16 W atoms are directed towards the central cavity, each of said 16 W atoms is bonded to a different O atom, wherein these 16 O atoms are directed further towards the central cavity such that the outer boundaries of the central cavity are designated by said 16 O atoms, which 16 O atoms are denoted the 16 inner O atoms in the context of the present invention. In case r is 1 or 2, preferably the one or two extra tungsten atoms occupy respectively one or two of the vacant sites in the cavity of the {X.sub.8W.sub.48O.sub.184}′ unit as defined above.
[0254] In a preferred embodiment, r is 0.
[0255] In a preferred embodiment, all M.sup.0 in the metal cluster (A′.sub.n′).sup.m′+[M.sup.0.sub.s(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m′− are the same; preferably wherein all M.sup.0 are the same and are selected from Pd.sup.0, Pt.sup.0, Rh.sup.0, and Ir.sup.0, more preferably Pd.sup.0, Pt.sup.0 and Rh.sup.0, most preferably Pd.sup.0 and Pt.sup.0, in particular Pd.sup.0. In the alternative, all M are selected from mixtures of Pd.sup.0 and Pt.sup.0.
[0256] In a preferred embodiment, the {X.sub.8W.sub.48+rO.sub.184+4r}′ unit, in particular in the {X.sub.8W.sub.48O.sub.184}′ unit, in the metal cluster (A′.sub.n′).sup.m′+[M.sup.0.sub.s(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m′− has a central cavity and all M.sup.0 atoms are located in said central cavity.
[0257] In a preferred embodiment, the central cavity in the {X.sub.8W.sub.48+rO.sub.184+4r}′ unit, in particular in the {X.sub.8W.sub.48O.sub.184}′ unit, in the metal cluster (A′.sub.n′).sup.m′+[M.sup.0.sub.s(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m′− has a diameter of 6 to 14 Å, more preferably 8 to 12 Å, in particular around 10 Å.
[0258] In a preferred embodiment, in the {X.sub.8W.sub.48+rO.sub.184+4r}′ unit, in particular in the {X.sub.8W.sub.48O.sub.184}′ unit, all of the 184+4r O have an oxidation state of −2, all of the 48+r W have an oxidation state of +6, +5 or +4 and all of the 8 X have an oxidation state of +5, in particular X is selected from the group consisting of P.sup.V and As.sup.V, preferably P.sup.V. Preferably, in case r is 0, the {X.sub.8W.sub.48O.sub.184}′ unit has a negative charge of −10 to −40. In case not all of the 48 W have an oxidation state of +6 in the {X.sub.8W.sub.48O.sub.184}′ unit the W have an oxidation state of +5 or +4 may be oxidized to have an oxidation state of +6 upon air oxidation under standard conditions (273.15 K (0° C., 32° F.) and 10.sup.5 Pa (1 bar)). In case all of the 48 W have an oxidation state of +6 in the {X.sub.8W.sub.48O.sub.184}′ unit, the {X.sub.8W.sub.48O.sub.184}′ unit in the metal cluster (A′.sub.n′).sup.m′+[M.sup.0.sub.s(X.sub.8W.sub.48O.sub.184)].sup.m′− is identical to the preferred {X.sub.8W.sub.48O.sub.184} unit in the POM (A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.m−, wherein all of the 184 O have an oxidation state of −2, all of the 48 W have an oxidation state of +6 and all of the 8 X have an oxidation state of +5. In case not all of the 48 W have an oxidation state of +6 in the {X.sub.8W.sub.48O.sub.184}′ unit, the {X.sub.8W.sub.48O.sub.184}′ unit in the metal cluster (A′.sub.n′).sup.m′+[M.sup.0.sub.s(X.sub.8W.sub.48O.sub.184)].sup.m′− may be converted into the preferred {X.sub.8W.sub.48O.sub.184} unit in the POM (A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48O.sub.184)].sup.m−, wherein all of the 184 O have an oxidation state of −2, all of the 48 W have an oxidation state of +6 and all of the 8 X have an oxidation state of +5, upon air oxidation under standard conditions (273.15 K (0° C., 32° F.) and 10.sup.5 Pa (1 bar)).
[0259] In the metal clusters of the present invention, the cation A′ can be a Group 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 and 16 metal cation or an organic cation. Preferably, each A′ is independently selected from the group consisting of cations of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Hf, Re, Os, Ir, Pt, Au, Hg, lanthanide metal, actinide metal, Al, Ga, In, Tl, Sn, Pb, Sb, Bi, phosphonium, ammonium, guanidinium, tetraalkylammonium, protonated aliphatic amines, protonated aromatic amines or combinations thereof. More preferably, A′ is selected from lithium, potassium, sodium cations and combinations thereof.
[0260] The number n of cations is dependent on the nature of cation(s) A′, namely its/their valence, and the negative charge m′ of the polyanion which has to be balanced. In any case, the overall charge of all cations A′ is equal to the charge of the metal cluster unit anion [M.sup.0.sub.s(X.sub.8W.sub.48+1O.sub.184+4)]. In turn, the charge m of the metal cluster unit anion [M.sup.0.sub.s(X.sub.8W.sub.48+1O.sub.184+4)] is dependent on the nature and oxidation state of the W atoms, and the nature and oxidation state of the heteroatoms X. Thus, m depends on the oxidation state of the atoms present in the polyanion, e.g., it follows from the oxidation states of O (−2), X (preferably +5 for As.sup.V or P.sup.V), M.sup.0 (0) and W (normally +6, and +5 or +4 for some W atoms). In some embodiments, m′ ranges from 1 to 44, preferably 8 to 40, more preferably 12 to 40, most preferably 16 to 40, in particular 16, 32, 34, 36, or 40. In particular, m′ is 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42 or 44. In a preferred embodiment, m′ is 16, 28, 32, 34, 36 or 38. Thus, n′ can generally range from 1 to 40, preferably 8 to 40, more preferably 12 to 40, most preferably 16 to 40. In particular, n′ ranges from 6 to 40 and more particularly is 6, 9, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32 or 40. In a preferred embodiment, n′ is 16, 28, 32, 34, 36 or 40.
[0261] Generally, A′ is acting as counterion of the metal cluster and is positioned outside of the metal cluster unit anion [M.sup.0.sub.s(X.sub.8W.sub.48+1O.sub.184+4)]. However, it is also possible that some of the cations A′ are located within the metal cluster unit anion [M.sup.0.sub.s(X.sub.8W.sub.48+1O.sub.184+4)]. In case the {X.sub.8W.sub.48+1O.sub.184+4}′ unit has a central cavity, it is also possible that some of the cations A′ are located within the central cavity. Any cation A′ being located within the metal cluster unit anion [M.sup.0.sub.s(X.sub.8W.sub.48+1O.sub.184+4)] is not selected from the group of noble metals.
[0262] Thus, in a preferred embodiment, the invention relates to a metal cluster (A′.sub.n′).sup.m′+[M.sup.0.sub.s(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m′−, wherein r is 0 and X is P.
[0263] Thus, in a preferred embodiment, the invention relates to a metal cluster (A′.sub.n′).sup.m′+[M.sup.0.sub.s(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m′−, wherein r is 0, X is P and s is 2 or 4.
[0264] Thus, in a preferred embodiment, the invention relates to a metal cluster (A′.sub.n′).sup.m′+[M.sup.0.sub.s(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m′−, wherein r is 0, X is P and M is Pd.
[0265] Thus, in a preferred embodiment, the invention relates to a metal cluster (A′.sub.n′).sup.m′+[M.sup.0.sub.s(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m′−, wherein r is 0, M is Pd, s is 4 and X is P.
[0266] Thus, in a preferred embodiment, the invention relates to a metal cluster (A′.sub.n′).sup.m′+[M.sup.0.sub.s(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m′−, wherein r is 0, and M is Pt.
[0267] Thus, in a preferred embodiment, the invention relates to a metal cluster (A′.sub.n′).sup.m′+[M.sup.0.sub.s(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m′−, wherein r is 0, M is Pt, s is 2 and X is P.
[0268] Thus, in a preferred embodiment, the invention relates to a metal cluster (A′.sub.n′).sup.m′+[M.sup.0.sub.s(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m′−, wherein r is 0, and M is Ir.
[0269] Thus, in a preferred embodiment, the invention relates to a metal cluster (A′.sub.n′).sup.m′+[M.sup.0.sub.s(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m′−, wherein r is 0, M is Ir, s is 2 and X is P.
[0270] Thus, in a preferred embodiment, the invention relates to a metal cluster (A′.sub.n′).sup.m′+[M.sup.0.sub.s(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m′−, wherein r is 0, and M is Rh.
[0271] Thus, in a preferred embodiment, the invention relates to a metal cluster (A′.sub.n′).sup.m′+[M.sup.0.sub.s(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m′−, wherein r is 0, and M is Rh, s is 4 and X is P.
[0272] Suitable examples of metal cluster (A′.sub.n′).sup.m′+[M.sup.0.sub.s(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m′−, according to the invention are represented by the formulae
(A′.sub.n′).sup.m′+[M.sup.0.sub.s(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m′−, e.g.,
(A′.sub.n′).sup.m′+[M.sup.0.sub.s(P.sub.8W.sub.48O.sub.184)].sup.m′−, such as
(A′.sub.n′).sup.m′+[Pd.sup.0.sub.s(P.sub.8W.sub.48O.sub.184)].sup.m′−, like
(A′.sub.n′).sup.m′+[Pd.sup.0.sub.2(P.sub.8W.sub.48O.sub.184)].sup.m′−,
(A′.sub.n′).sup.m′+[Pd.sup.0.sub.4(P.sub.8W.sub.48O.sub.184)].sup.m′−,
(A′.sub.n′).sup.m′+[Pd.sup.0.sub.6(P.sub.8W.sub.48O.sub.184)].sup.m′−,
(A′.sub.n′).sup.m′+[Pd.sup.0.sub.8(P.sub.8W.sub.48O.sub.184)].sup.m′−,
(A′.sub.n′).sup.m′+[Pt.sup.0.sub.s(P.sub.8W.sub.48O.sub.184)].sup.m′−, like
(A′.sub.n′).sup.m′+[Pt.sup.0.sub.2(P.sub.8W.sub.48O.sub.184)].sup.m′−,
(A′.sub.n′).sup.m′+[Pt.sup.0.sub.4(P.sub.8W.sub.48O.sub.184)].sup.m′−,
(A′.sub.n′).sup.m′+[Pt.sup.0.sub.6(P.sub.8W.sub.48O.sub.184)].sup.m′−,
(A′.sub.n′).sup.m′+[Pt.sup.0.sub.8(P.sub.8W.sub.48O.sub.184)].sup.m′−,
(A′.sub.n′).sup.m′+[Ir.sup.0.sub.s(P.sub.8W.sub.48O.sub.184)].sup.m′−, like
(A′.sub.n′).sup.m′+[Ir.sup.0.sub.2(P.sub.8W.sub.48O.sub.184)].sup.m′−,
(A′.sub.n′).sup.m′+[Ir.sup.0.sub.4(P.sub.8W.sub.48O.sub.184)].sup.m′−,
(A′.sub.n′).sup.m′+[Ir.sup.0.sub.6(P.sub.8W.sub.48O.sub.184)].sup.m′−,
(A′.sub.n′).sup.m′+[Ir.sup.0.sub.8(P.sub.8W.sub.48O.sub.184)].sup.m′−,
(A′.sub.n′).sup.m′+[Rh.sup.0.sub.s(P.sub.8W.sub.48O.sub.184)].sup.m′−, like
(A′.sub.n′).sup.m′+[Rh.sup.0.sub.2(P.sub.8W.sub.48O.sub.184)].sup.m′−,
(A′.sub.n′).sup.m′+[Rh.sup.0.sub.4(P.sub.8W.sub.48O.sub.184)].sup.m′−,
(A′.sub.n′).sup.m′+[Rh.sup.0.sub.6(P.sub.8W.sub.48O.sub.184)].sup.m′−,
(A′.sub.n′).sup.m′+[Rh.sup.0.sub.8(P.sub.8W.sub.48O.sub.184)].sup.m′−,
(A′.sub.n′).sup.m′+[M.sup.0.sub.s(As.sub.8W.sub.48O.sub.184)].sup.m′−, such as
(A′.sub.n′).sup.m′+[Pd.sup.0.sub.s(As.sub.8W.sub.48O.sub.184)].sup.m′−,
(A′.sub.n′).sup.m′+[Pt.sup.0.sub.s(As.sub.8W.sub.48O.sub.184)].sup.m′−,
(A′.sub.n′).sup.m′+[Ir.sup.0.sub.s(As.sub.8W.sub.48O.sub.184)].sup.m′−,
(A′.sub.n′).sup.m′+[Rh.sup.0.sub.s(As.sub.8W.sub.48O.sub.184)].sup.m′−,
(A′.sub.n′).sup.40+[M.sup.0.sub.s(X.sub.8W.sub.48O.sub.184)].sup.40−, such as
(A′.sub.n′).sup.40+[M.sup.0.sub.s(P.sub.8W.sub.48O.sub.184)].sup.40−,
(A′.sub.n′).sup.40+[Pd.sup.0.sub.s(X.sub.8W.sub.48O.sub.184)].sup.40−,
(A′.sub.n′).sup.40+[Pt.sup.0.sub.s(X.sub.8W.sub.49O.sub.184)].sup.40−,
(A′.sub.n′).sup.40+[Ir.sup.0.sub.s(X.sub.8W.sub.48O.sub.184)].sup.40−,
(A′.sub.n′).sup.40+[Rh.sup.0.sub.s(X.sub.8W.sub.48O.sub.184)].sup.40−,
(A′.sub.40).sup.40+[M.sup.0.sub.s(X.sub.8W.sub.48O.sub.184)].sup.40−, like
(A′.sub.40).sup.40+[Pd.sup.0.sub.s(X.sub.8W.sub.48O.sub.184)].sup.40−,
(A′.sub.40).sup.40+[Pt.sup.0.sub.s(X.sub.8W.sub.48O.sub.184)].sup.40−,
(A′.sub.40).sup.40+[Ir.sup.0.sub.s(X.sub.8W.sub.48O.sub.184)].sup.40−,
(A′.sub.40).sup.40+[Rh.sup.0.sub.s(X.sub.8W.sub.48O.sub.184)].sup.40−,
(A′.sub.20).sup.40+[M.sup.0.sub.s(X.sub.8W.sub.48O.sub.184)].sup.40−, like
(A′.sub.20).sup.40+[Pd.sup.0.sub.s(X.sub.8W.sub.48O.sub.184)].sup.40−,
(A′.sub.20).sup.40+[Pt.sup.0.sub.s(X.sub.8W.sub.48O.sub.184)].sup.40−,
(A′.sub.20).sup.40+[Ir.sup.0.sub.s(X.sub.8W.sub.48O.sub.184)].sup.40−,
(A′.sub.20).sup.40+[Rh.sup.0.sub.s(X.sub.8W.sub.48O.sub.184)].sup.40−,
(A′.sub.n′).sup.38+[M.sup.0.sub.s(X.sub.8W.sub.48O.sub.184)].sup.38−,
(A′.sub.n′).sup.36+[M.sup.0.sub.s(X.sub.8W.sub.48O.sub.184)].sup.36−,
(Li.sub.n′).sup.m′+[M.sup.0.sub.s(X.sub.8W.sub.48O.sub.184)].sup.m′−,
(Na.sub.n′).sup.m′+[M.sup.0.sub.s(X.sub.8W.sub.48O.sub.184)].sup.m′−,
(K.sub.n′).sup.m′+[M.sup.0.sub.s(X.sub.8W.sub.48O.sub.184)].sup.m′−.
[0273] The metal clusters of the present invention are in the form of primary and/or secondary particles. In an especially preferred embodiment, the metal clusters provided by the present invention are mainly in the form of primary particles (i.e., non-agglomerated primary particles), that is at least 90 wt % of the metal clusters are in the form of primary particles, preferably at least 95 wt %, more preferably at least 99 wt %, in particular substantially all the metal clusters are in the form of primary particles. This includes metal clusters dispersed in liquid carrier media. The metal clusters of the present invention preferably have a primary particle size of about 1.5-2.5 nm, for instance about 2.0 nm on average.
[0274] In the metal clusters of the present invention, the guest atoms M.sup.0 may theoretically be replaced or removed without destroying the structural framework of the {X.sub.8W.sub.48+rO.sub.184+4r}′ unit. However, the present inventors observed that guest atoms M.sup.0 remain attached to the {X.sub.8W.sub.48+rO.sub.184+4r}′ unit under a variety of conditions, e.g., in aqueous solution at pH values of 1 to 10, preferably 1 to 8, or in the solid state at temperatures up 500° C., preferably 400° C.
[0275] In a further embodiment, the metal clusters are dispersed in a liquid carrier medium, thereby forming a dispersion of metal clusters. In one embodiment of the present invention the liquid carrier medium is an organic solvent, optionally combined with one or more dispersing agents. The organic solvent is preferably capable of dissolving the POMs used as starting material for the preparation of the metal clusters, for instance liquid n-alkanes, e.g., hexane or heptane.
[0276] The dispersing agent (or surfactant) is added to the liquid carrier medium to prevent agglomeration of the primary particles of metal cluster. Preferably, the dispersing agent is present during formation of the primary particles of metal cluster. An example of a surfactant useful as dispersing agent is citric acid or citrate. The dispersing agent preferably forms micelles, each micelle containing one primary particle of metal cluster thereby separating the primary particles from each other and preventing agglomeration thereof.
[0277] In another further embodiment, the metal clusters can be immobilized on a solid support thereby forming supported metal clusters. Suitable supports include but are not limited to materials having a high surface area and/or a pore size which is sufficient to allow the metal clusters to be loaded, e.g., polymers, graphite, carbon nanotubes, electrode surfaces, aluminum oxide and aerogels of aluminum oxide and magnesium oxide, titanium oxide, zirconium oxide, cerium oxide, silicon dioxide, silicates, active carbon, mesoporous materials, like mesoporous silica, such as SBA-15 and MCM-41, zeolites, aluminophosphates (ALPOs), silicoaluminophosphates (SAPOs), metal organic frameworks (MOFs), zeolitic imidazolate frameworks (ZIFs), periodic mesoporous organosilicas (PMOs), and mixtures thereof and modified compounds thereof. Preferred supports are, for instance, mesoporous silica, more preferably SBA-15 or MCM-41, most preferably SBA-15.
[0278] A variety of such solid supports is commercially available or can be prepared by common techniques. Furthermore, there are various common techniques to modify or functionalize solid supports, for example with regard to the size and shape of the surface or the atoms or groups available for bonding on the surface. In a preferred embodiment of the present invention the immobilization of the metal clusters to the surface of the solid support is accomplished by means of adsorption, including physisorption and chemisorption, preferably physisorption. The adsorption is based on interactions between the metal clusters and the surface of the solid support, such as van-der-Waals interactions.
[0279] In the supported metal clusters of the present invention, the metal clusters that are immobilized on the solid support are in the form of primary and/or secondary particles. In an especially preferred embodiment, the immobilized metal cluster particles are mainly in the form of primary particles (i.e., non-agglomerated primary particles), that is at least 90 wt % of the immobilized metal cluster particles are in the form of primary particles, preferably at least 95 wt %, more preferably at least 99 wt %, in particular substantially all the immobilized metal cluster particles are in the form of primary particles.
[0280] In the supported metal clusters of the present invention, the metal cluster loading levels on the solid support may be up to 30 wt % or even more, but are preferably up to 10 wt %, for instance up to 5 wt % or even up to 2 wt %. Accordingly, the metal cluster loading level on the solid support is typically of 0.01 to 30 wt %, particularly 0.05 to 20 wt %, more particularly 0.1 to 10 wt %, often 0.2-6 wt %, more often 0.3-5 wt %, and most often 0.5-2 wt %. Metal cluster loading levels on the solid support can be determined by elemental analysis such as Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analysis, for instance using a Varian Vista MPX.
[0281] The invention is further directed to processes for preparing metal clusters according to the invention.
[0282] Among the preferred processes for preparing any one of the metal clusters of the present invention is a process for the preparation of a dispersion of said metal clusters dispersed in liquid carrier media. Said process comprises: [0283] (a) dissolving any one of the POMs provided by the present invention or prepared according to the present invention in a liquid carrier medium, [0284] (b) optionally providing additive means to prevent agglomeration of the metal clusters to be prepared, preferably adding compounds capable of preventing agglomeration of metal clusters to be prepared, more preferably adding surfactants to enable micelle formation, and [0285] (c) subjecting the dissolved POM to chemical or electrochemical reducing conditions sufficient to at least partially reduce said POM into corresponding metal clusters.
[0286] In a preferred embodiment in step (a), the liquid carrier medium capable of dissolving the POM used for the preparation of the metal clusters is an organic solvent, such as liquid n-alkanes, e.g., hexane or heptane.
[0287] In a preferred embodiment in step (b), classical capping groups such as diverse types of inorganic and organic anions, such as carboxylates, e.g., citrate, may be used to prevent agglomeration of the metal clusters to be prepared.
[0288] In a preferred embodiment in step (c), the chemical reducing conditions comprise the use of a reducing agent selected from organic and inorganic materials which are oxidizable by Pd.sup.II and Pd.sup.IV, Pt.sup.II and Pt.sup.IV, Rh.sup.I and Rh.sup.III, Ir.sup.I and Ir.sup.III, Ag.sup.I and Ag.sup.III and Au.sup.I and Au.sup.III. Such a chemical reduction can for example be effected by using borohydrides, aluminohydrides, hydrazine, CO or hydrogen, preferably hydrogen, more preferably hydrogen at elevated temperature and pressure, preferably by using hydrogen. In the alternative, the POM in step (c) is reduced electrochemically using a common electrochemical cell.
[0289] The metal clusters of the present invention can be immobilized on the surface of a solid support. The present invention therefore also relates to processes for the preparation of supported metal clusters according to the present invention. A first process for the preparation of supported metal clusters comprises contacting the dispersion of metal clusters provided by the present invention or prepared according to the present invention with a solid support, thereby immobilizing at least part of the dispersed metal clusters onto the support; and optionally isolating the supported metal clusters.
[0290] In a preferred embodiment, the solid support is added to the dispersion of metal clusters. The resulting mixture is preferably stirred, typically for 1 min to 24 h, more preferably for 30 min to 15 h, more preferably for 1 h to 12 h, most preferably for 6 h to 10 h, in particular about 8 h. While stirring, preferably the mixture is heated to a temperature of from 20° C. to 100° C., preferably from 20° C. to 80° C., preferably from 20° C. to 60° C. preferably from 20° C. to 40° C., and most preferably about 25° C. Afterwards, the supported metal clusters are preferably isolated. Isolation of the supported metal clusters from the solvent may be performed by any suitable method in the art, such as by filtration, evaporation of the solvent, centrifugation or decantation, preferably by filtration or removal of the solvent in vacuum, more preferably by filtration. The isolated supported metal clusters may then be washed with a suitable solvent, preferably water or an aqueous solvent, and dried, for instance by heating under vacuum.
[0291] Another suitable process for the preparation of supported metal clusters according to the present invention comprises: subjecting supported POM provided by the present invention or prepared according to the present invention to chemical or electrochemical reducing conditions sufficient to at least partially reduce said POM into corresponding metal clusters; and optionally isolating the supported metal clusters.
[0292] In a preferred embodiment, the chemical reducing conditions comprise the use of a reducing agent selected from organic and inorganic materials which are oxidizable by Pd.sup.II and Pd.sup.IV, Pt.sup.II and Pt.sup.IV, Rh.sup.I and Rh.sup.III, Ir.sup.I and Ir.sup.III, Ag.sup.I and Ag.sup.III, and Au.sup.I and Au.sup.III. Such a chemical reduction can for example be effected by using borohydrides, aluminohydrides, hydrazine, CO or hydrogen, preferably hydrogen, more preferably hydrogen at elevated temperature and pressure. In the alternative, the POM is reduced electrochemically using a common electrochemical cell.
[0293] The invention is also directed to the use of optionally supported POMs provided by the present invention or prepared according to the present invention and/or optionally supported or dispersed metal clusters provided by the present invention or prepared according to the present invention, for catalyzing homogeneous and heterogeneous conversion of organic substrates.
[0294] In a preferred embodiment, conversion may refer to homogeneous or heterogeneous reduction and/or hydroprocessing and/or hydrocracking and/or (hydro)desulfurization and/or oxidation of organic substrate.
[0295] In a preferred embodiment the process for the homogeneous or heterogeneous conversion of organic substrate comprises contacting said organic substrate with the optionally supported POMs provided by the present invention or prepared according to the present invention and/or optionally supported or dispersed metal clusters provided by the present invention or prepared according to the present invention.
[0296] Since the M metal atoms are not fully sterically shielded by the polyanion framework, various noble metal coordination sites are easily accessible to the organic substrate and therefore high catalytic activities are achieved. Further, the thermal stability of the optionally supported POMs of the present invention permits their use under a variety of reaction conditions.
[0297] It is contemplated that the optionally supported POMs of the present invention can be activated by any process described herein or any process known in the art, preferably by increasing the accessibility to their noble metal atoms M. Thus, it might be possible that the optionally supported POMs are reductively converted into metal cluster-like structures or even into metal clusters under the conversion reaction conditions and it might be possible that said metal cluster-like structures or said metal clusters are in fact the catalytically active species. Nevertheless, the optionally supported POMs of the present invention give excellent results in homogeneous and heterogeneous conversion of organic substrates, regardless of the specific nature of the actually catalytically active species.
[0298] Another useful aspect of this invention is that the optionally supported POMs and optionally supported or dispersed metal clusters of the present invention can be recycled and used multiple times for the conversion of organic molecules, i.e., without significant loss of the expensive noble metals. While the inventors do not wish to be bound by any particular theory, it is believed that the {X.sub.8W.sub.48O.sub.184} unit and the {X.sub.8W.sub.48O.sub.184}′ unit forms a highly stable and robust shell unit, which accommodates and, thus, protects the noble metal species. The present inventors believe that the {X.sub.8W.sub.48+rO.sub.184+4r} unit, in particular the {X.sub.8W.sub.48O.sub.184}, unit and the {X.sub.8W.sub.48+rO.sub.184+4r}′ unit, in particular the {X.sub.8W.sub.48O.sub.184}′ unit, provide a fine balance between shielding the expensive noble metal species in the regeneration step without preventing sufficient access for the substrates to the catalytically active noble metals in the catalytic process step, i.e., the {X.sub.8W.sub.48+rO.sub.184+4r} unit, in particular the {X.sub.8W.sub.48O.sub.184}, unit and the {X.sub.8W.sub.48+rO.sub.184+4r} unit, in particular the {X.sub.8W.sub.48O.sub.184}′ unit, provide sufficient shielding for the noble metal species to prevent sintering in the regeneration step but not so much shielding that the noble metal species would be deprived of the catalytic activity. The underlying considerations set forth in more detail hereinabove in the context of the optionally supported POMs apply equally to the optionally supported or dispersed metal clusters of the present invention.
[0299] In a preferred embodiment this invention thus also relates to a process for converting organic substrates comprising the steps: [0300] (a) contacting a first organic substrate with one or more optionally supported POMs and/or one or more supported metal clusters, [0301] (b) recovering the one or more optionally supported POMs and/or one or more supported metal clusters; [0302] (c) contacting the one or more optionally supported POMs and/or one or more supported metal clusters with a solvent at a temperature of 50° C. or more, and/or hydrogen stripping the one or more optionally supported POMs and/or the one or more supported metal clusters at elevated temperature, and/or calcining the one or more optionally supported POMs and/or the one or more supported metal clusters at elevated temperature under an oxygen containing gas, e.g. air, or under an inert gas, e.g. nitrogen or argon, to obtain a recycled one or more optionally supported POMs and/or one or more supported metal clusters; [0303] (d) contacting the recycled one or more optionally supported POMs and/or one or more supported metal clusters with a second organic substrate which may be the same as or different from the first organic substrate; and [0304] (e) optionally repeating steps (b) to (d).
[0305] The contacting of organic substrate with optionally supported POM and/or supported metal cluster in step (a) may, e.g., be carried out in a continuously stirred tank reactor (CSTR), a fixed bed reactor, a fluidized bed reactor or a moving bed reactor.
[0306] Thus, e.g., the optionally supported POMs and/or supported metal clusters of the present invention can be collected after a conversion reaction, washed with a polar or non-polar solvent such as acetone and then dried under heat (typically 50° C. or more, alternately 75° C. or more, alternately 100° C. or more, alternately 125° C. or more) for 30 minutes to 48 hours, typically for 1 to 24 hours, more typically for 2 to 10 hours, more typically for 3 to 5 hours.
[0307] Alternatively to or in addition to the washing, the optionally supported POMs and/or supported metal clusters may be subjected to hydrogen stripping at elevated temperature. Preferably, the hydrogen stripping is carried out at a temperature of 50° C. or higher, more preferably at a temperature of 75° C. or higher and most preferably at a temperature of 100° C. or higher.
[0308] Alternatively to or in addition to the washing and/or hydrogen stripping, the optionally supported POMs and/or supported metal clusters may be calcined at elevated temperature under an oxygen containing gas, e.g., air, or under an inert gas, e.g., nitrogen or argon. Preferably, the calcination is carried out at a temperature in the range from 75° C. to 150° C., such as from 90° C. to 120° C. or from 120° C. to 150° C.
[0309] The washing and/or hydrogen stripping and/or calcining has/have the effect of regenerating the optionally supported POMs and/or supported metal clusters for recycling.
[0310] The recycled optionally supported POMs and/or supported metal clusters of the present invention may be used on fresh organic molecules, or on recycled organic molecules from a recycle stream.
[0311] It is preferred to use supported POMs and/or supported metal clusters of the present invention as catalysts with regard to recovery and recycling of the catalyst in the conversion processes described herein. Advantageously, the supported POMs and/or supported metal clusters of the present invention may be recycled and used again under the same or different reaction conditions. Typically the supported POMs and/or supported metal clusters are recycled at least 1 time, preferably at least 4 times, preferably at least 8 times, preferably at least 12 times, preferably at least 100 times.
[0312] Thus, this invention also relates to a process for converting organic substrates which process comprises contacting a first organic substrate with one or more supported POMs and/or supported metal clusters of the present invention, thereafter recovering the supported POMs and/or supported metal clusters of the present invention, contacting the supported POMs and/or supported metal clusters of the present invention with a solvent (such as acetone) at a temperature of 50° C. or more, and/or hydrogen stripping the supported POMs and/or supported metal clusters at elevated temperature, and/or calcining the supported POMs and/or supported metal clusters to obtain recycled supported POMs and/or supported metal clusters of the present invention, thereafter contacting the recycled supported POMs and/or supported metal clusters of the present invention with a second organic substrate, which may be the same as or different from the first organic substrate, this process may be repeated many times, preferably at least 4 times, preferably at least 8 times, preferably at least 12 times, preferably at least 100 times.
[0313] Due to the definite stoichiometry of POMs, the optionally supported POMs of the present invention can also be used as a precursor for mixed metal-oxide catalysts.
[0314] Metal clusters of the present invention, optionally supported or dispersed in a liquid carrier medium, can be described as nanocatalysts of M at the atomic or molecular level, i.e., particles of M having an average diameter of about 1.5-2.5 nm, for instance about 2.0 nm, obtained by reduction of the POMs. In the case of the preferred embodiment, wherein all M are the same, nanocatalysts with at least one noble atom species are obtained. In another embodiment in which at least one or more M are different among each other, nanocatalysts with more than one noble atom species, such as 2 to 6 noble atom species, preferably 2, 3 or 4, more preferably 2 or 3, most preferably 2, are obtained. Thus, the bottom-up approach of the present invention allows for the preparation of noble metal-rich customized nanocatalysts of very well defined size and shape, in which two or more than two metal species can be selected individually from groups that contain or consist of the noble metal elements Rh, Ir, Pd, Pt, Ag, and Au.
[0315] The obtained metal clusters can be used for a wide range of catalytic applications such as in fuel cells, for detection of organic substrates, selective hydrogenation, reforming, hydrocracking, hydrogenolysis and oligomerization. Besides immobilizing the present POMs on a matrix surface and subsequently reducing them, the deposition of the POMs on a surface matrix and their reduction can also be carried out simultaneously.
[0316] In addition, e.g., the POMs according to the invention can be used to produce modified electrodes by electrochemical deposition of the POM on an electrode surface such as a glassy carbon (GC) electrode surface. The obtained deposits contain predominantly M.sup.0 such as Rh.sup.0, Ir.sup.0, Pd.sup.0, Pt.sup.0, Ag.sup.0, Au.sup.0, and preferably mixtures thereof with very small amounts Mχ.sup.+ such as Pd.sup.II and Pd.sup.IV, Pt.sup.II and Pt.sup.IV, Rh.sup.I and Rh.sup.III, Ir.sup.I and Ir.sup.III, Ag.sup.I and Ag.sup.III and Au.sup.I and Au.sup.III and mixtures thereof, preferably Pd.sup.II, Pt.sup.II, Rh.sup.I, Ir.sup.I, Ag.sup.I, and Au.sup.I. In a preferred embodiment, the obtained deposits provide improved electrochemical behaviors like improved kinetics of electrocatalytic processes compared to a film deposited using a conventional precursor of M. For example, electrodes modified with a deposit of the present POMs can be used for the electrochemical reduction of organic substrates. It has been found that such modified electrodes show a very small overpotential and a remarkably high shelf life.
EXAMPLES
[0317] The invention is further illustrated by the following examples.
Example 1a
Synthesis of K.SUB.20.Li.SUB.8.[Rh.SUB.4.P.SUB.8.W.SUB.48.O.SUB.184.].86H.SUB.2.O
[0318] RhCl.sub.3 (0.02 g, 0.063 mmol) and K.sub.28Li.sub.5H.sub.7P.sub.8W.sub.48O.sub.184.92H.sub.2O (0.1 g, 0.0068 mmol (for preparation see, e.g., Inorg. Chem. 1985, 24, 4610-4614; Inorg. Synth. 1990, 27, 110)) were dissolved in a mixture of 1 M lithium acetate solution (5 mL, pH 7.0) and 0.5 ml ethanol. While stirring, 200 μl of a 1 M lithium perchlorate solution were added. The solution was heated in a water bath to 80° C. for 60 min during which the solution turned dark green; without wishing to be bound by any theory the observed colour change could be due to the in situ formation of Rhodium (II) acetate dimer. Finally, 0.5 ml of 30% H.sub.2O.sub.2 were added dropwise and the solution was stirred for an additional 60 min at 80° C. The final orange-yellow solution was allowed to cool to room temperature and left for crystallization in an open vial. Orange octahedral crystals started to form after approximately 2 to 3 days, which were collected by filtration and air-dried after one week. Yield: 0.04 g (40% based on W). This product was analyzed by XRD, IR, elemental analysis, TGA and .sup.31P NMR and was identified as {Rh.sub.4[P.sub.8W.sub.48O.sub.184]}.sup.28− polyanion (“Rh.sub.4P.sub.8W.sub.48”), isolated as hydrated salt K.sub.20Li.sub.8[Rh.sub.4P.sub.8W.sub.48O.sub.184].86H.sub.2O (“K.sub.20Li.sub.8—Rh.sub.4P.sub.8W.sub.48”). The product was found to be identical to the product of the below experiment 1b.
Example 1b
Synthesis of K.SUB.20.Li.SUB.8.[Rh.SUB.4.P.SUB.8.W.SUB.48.O.SUB.184.].86H.SUB.2.O
[0319] RhCl.sub.3 (0.02 g, 0.063 mmol) was dissolved in 0.5 ml H.sub.2O. The initial pH of this solution was around 1.5 and was adjusted to 13.2 with 150 μl of 6 m NaOH solution. (Solution A). K.sub.28Li.sub.5H.sub.7P.sub.8W.sub.48O.sub.184.92H.sub.2O (0.1 g, 0.0068 mmol (for preparation see, e.g., Inorg. Chem. 1985, 24, 4610-4614; Inorg. Synth. 1990, 27, 110)) was dissolved in a mixture of 1 M lithium acetate solution (5 mL, pH 4.0) and 200 μl of a 1 M lithium perchlorate solution (Solution B). The solutions A and B were then mixed and heated in a water bath at 80° C. for 60 min. The final orange solution was allowed to cool to room temperature and left for crystallization in an open vial. Orange octahedral crystals started to form after approximately 2 to 3 days, which were collected by filtration and air-dried after one week. Yield: 0.037 g (37% based on W). This product was analyzed by XRD, IR, elemental analysis, TGA and .sup.31P NMR and was identified as {Rh.sub.4[P.sub.8W.sub.48O.sub.184]}.sup.28− polyanion (“Rh.sub.4P.sub.8W.sub.48”), isolated as hydrated salt K.sub.20Li.sub.8[Rh.sub.4P.sub.8W.sub.48O.sub.184].86H.sub.2O (“K.sub.20Li.sub.8—Rh.sub.4P.sub.8W.sub.48”). The product was found to be identical to the product of the above experiment 1a.
Example 2
Analysis of “K.SUB.20.Li.SUB.8.—Rh.SUB.4.P.SUB.8.W.SUB.48.”
[0320] The IR spectrum with 4 cm.sup.−1 resolution was recorded on a Nicolet Avatar 370 FT-IR spectrophotometer on KBr pellet sample (peak intensities: w=weak; m=medium; s=strong). The characteristic region of the polyanion is the fingerprint region or the region between 1000-400 cm.sup.−1 due to metal-oxygen stretching and bending vibrations: 1636 (s), 1618 (s), 1384 (w), 1138 (s), 1087(s), 1019 (m), 931 (s), 920 (s), 810 (s), 686 (s), 573 (w), 528 (w), 464 (w). The FT-IR spectrum is shown in
[0321] Elemental analysis for “K.sub.20Li.sub.8—Rh.sub.4P.sub.8W.sub.48” calculated (found): K 5.25(5.1), Li 0.37(0.41), Rh 2.77(2.46), P 1.67(1.68), W 59.4(58.64).
[0322] Thermogravimetric analysis (TGA) was performed on a SDT Q 600 device from TA Instruments with 10-30 mg samples in 100 μL alumina pans, under a 100 mL/min N.sub.2 flow with a heating rate of 5° C./min between 20° C. and 800° C. (
Example 3
Single Crystal X-Ray Diffraction (XRD) Data and Analysis of “K.SUB.20.Li.SUB.8.—Rh.SUB.4.P.SUB.8.W.SUB.48.”
[0323] Besides IR, elemental analysis and TGA the product was also characterized by single-crystal XRD. The crystal was mounted in Hampton cryoloop at 100 K using light oil for data collection. Indexing and data collection were carried on a Bruker Kappa X8 APEX II CCD single crystal diffractometer with κ geometry and Mo Kα radiation (λ=0.71073 {acute over (Å)}). The SHELX software package (Bruker) was used to solve and refine the structure. An empirical absorption correction was applied using the SADABS program as disclosed in G. M. Sheldrick, SADABS, Program for empirical X-ray absorption correction, Bruker-Nonius: Madison, Wis. (1990). The structure was solved by direct method and refined by the full-matrix least squares method (Σw(|F.sub.o|.sup.2−|F.sub.c|.sup.2).sup.2) with anisotropic thermal parameters for all heavy atoms included in the model. The H atoms were not located. Also, it was not possible to locate all lithium and potassium counter cations by XRD, due to crystallographic disorder. The exact number of counter cations and crystal water in the POM were thus based on elemental analysis and TGA. Compound “K.sub.20Li.sub.8—Rh.sub.4P.sub.8W.sub.48” crystallizes in the tetragonal space group I4/m. Crystallographic data are detailed in Table 1.
TABLE-US-00001 TABLE 1 Crystal data for “K.sub.20Li.sub.8-Rh.sub.4P.sub.8W.sub.48” Empirical formula K.sub.20Li.sub.8Rh.sub.4P.sub.8W.sub.48O.sub.184•86H.sub.2O Formula weight, g/mol 14814 Crystal system Tetragonal Space group I4/m a, Å 25.6138 (9) b, Å 25.6138 (9) c, Å 21.6978 (8) α, ° 90 β, ° 90 γ, ° 90 Volume, Å.sup.3 14235.2 (11) Z 4 D.sub.calc, g/cm.sup.3 3.077 Absorption coefficient, mm.sup.−1 19.773 F (000) 11400.0 Theta range for data collection, ° 1.124 to 25.999 Completeness to Θ.sub.max % 99.9% Index ranges −28 <= h <= 31, −31 <= k <= 31, −26 <= l <= 26 Reflections collected 58225 Independent reflections 7189 R (int) 0.1081 Absorption correction Semi-empirical from equivalents Data/restraints/parameters 8182/0/194 Goodness-of-fit on F.sup.2 1.015 R.sub.1.sup.[a], wR.sub.2.sup.[b] (I > 2σ(I)) R.sub.1 = 0.0567, wR.sub.2 = 0.1880 R.sub.1.sup.[a], wR.sub.2.sup.[b] (all data) R.sub.1 = 0.0922, wR.sub.2 = 0.2308 .sup.[a]R.sub.1 = Σ | |F.sub.o| − |F.sub.c| | / Σ |F.sub.o|. .sup.[b]wR.sub.2 = [Σw(F.sub.o.sup.2 − F.sub.c.sup.2).sup.2/ Σw(F.sub.o.sup.2).sup.2].sup.1/2
Example 4
Structure of the “Rh.SUB.4.P.SUB.8.W.SUB.48.” Polyanion
[0324] The structure of the “Rh.sub.4P.sub.8W.sub.48” polyanion is displayed in
Example 5
.SUP.31.P NMR Spectrum of “K.SUB.20.Li.SUB.8.—Rh.SUB.4.P.SUB.8.W.SUB.48.”
[0325] “K.sub.20Li.sub.8—Rh.sub.4P.sub.8W.sub.48” crystals were dissolved in D.sub.2O. .sup.31P NMR spectrum was recorded at 20° C. on a 400 MHz JEOL ECX instrument, using 5 mm tube with resonance frequency 161.6 MHz. The chemical shift is reported with respect to the reference 85 wt % H.sub.3PO.sub.4. The .sup.31P NMR spectrum is shown in
Example 6
Synthesis of K.SUB.20.Li.SUB.5.H.SUB.7.[Pd.SUB.4.P.SUB.8.W.SUB.48.O.SUB.184.].81H.SUB.2.O
[0326] Pd(CH.sub.3COO).sub.2 (0.013 g, 0.057 mmol) and K.sub.28Li.sub.5H.sub.7P.sub.8W.sub.48O.sub.184.92H.sub.2O (0.050 g, 0.0034 mmol (for preparation see, e.g., Inorg. Chem. 1985, 24, 4610-4614; Inorg. Synth. 1990, 27, 110)) were dissolved in 1 M lithium acetate solution (5 mL, pH 3.0). While stirring, 100 μl of a 1 M lithium perchlorate solution were added and the solution was heated in a water bath to 70° C. for 60 min. Then the solution was allowed to cool to room temperature, filtered, and the filtrate left for crystallization in an open vial. Yellow octahedral crystals were obtained after approximately 3 weeks, which were collected by filtration and air-dried. Yield: 0.03 g (60% based on W). This product was analyzed by XRD, IR, elemental analysis, TGA and .sup.31P NMR and was identified as {Pd.sub.4[P.sub.8W.sub.48O.sub.184]}.sup.32− polyanion (“Pd.sub.4P.sub.8W.sub.48”), isolated as hydrated salt K.sub.20Li.sub.5H.sub.7[Pd.sub.4P.sub.8W.sub.48O.sub.184].81H.sub.2O (“K.sub.20Li.sub.5H.sub.7—Pd.sub.4P.sub.8W.sub.48”).
Example 7
Analysis of “K.SUB.20.Li.SUB.5.H.SUB.7.—Pd.SUB.4.P.SUB.8.W.SUB.48.”
[0327] The IR spectrum with 4 cm.sup.−1 resolution was recorded on a Nicolet Avatar 370 FT-IR spectrophotometer on KBr pellet sample (peak intensities: w=weak; m=medium; s=strong). The characteristic region of the polyanion is the fingerprint region or the region between 1000-400 cm-1 due to metal-oxygen stretching and bending vibrations: 1635 (s), 1618 (s), 1539 (w), 1418 (w), 1384 (w), 1137 (s), 1084(s), 1016 (m), 928 (s), 809 (s), 691 (s), 574 (w), 529 (w), 461 (w). The FT-IR spectrum is shown in
[0328] Elemental analysis for “K.sub.20Li.sub.5H.sub.7—Pd.sub.4P.sub.8W.sub.48” calculated (found): K 4.52(4.4), Li 0.43(0.42), Pd 2.90(2.82), P 1.7(1.75), W 60.52(61.05).
[0329] Thermogravimetric analysis (TGA) was performed on a SDT Q 600 device from TA Instruments with 10-30 mg samples in 100 μL alumina pans, under a 100 mL/min N.sub.2 flow with a heating rate of 5° C./min between 20° C. and 800° C. (
Example 8
Single Crystal X-Ray Diffraction (XRD) Data and Analysis of “K.SUB.20.Li.SUB.5.H.SUB.7.—Pd.SUB.4.P.SUB.8.W.SUB.48.”
[0330] Besides IR, elemental analysis and TGA the product was also characterized by single-crystal XRD. The crystal was mounted in Hampton cryoloop at 100 K using light oil for data collection. Indexing and data collection were carried on a Bruker Kappa X8 APEX II CCD single crystal diffractometer with κ geometry and Mo Kα radiation (λ=0.71073 {acute over (Å)}). The SHELX software package (Bruker) was used to solve and refine the structure. An empirical absorption correction was applied using the SADABS program as disclosed in G. M. Sheldrick, SADABS, Program for empirical X-ray absorption correction, Bruker-Nonius: Madison, Wis. (1990). The structure was solved by direct method and refined by the full-matrix least squares method (Σw(|F.sub.o|.sup.2−|F.sub.c|.sup.2).sup.2) with anisotropic thermal parameters for all heavy atoms included in the model. The H atoms were not located. Also, it was not possible to locate all lithium and potassium counter cations by XRD, due to crystallographic disorder. The exact number of counter cations and crystal water in the POM were thus based on elemental analysis and TGA. Compound “K.sub.20Li.sub.5H.sub.7—Pd.sub.4P.sub.8W.sub.48” crystallizes in the tetragonal space group Immm. Crystallographic data are detailed in Table 2.
TABLE-US-00002 TABLE 2 Crystal data for “K.sub.20Li.sub.5H.sub.7-Pd.sub.4P.sub.8W.sub.48” Empirical formula K.sub.20Li.sub.5H.sub.7Pd.sub.4P.sub.8W.sub.48O.sub.184•81H.sub.2O Formula weight, g/mol 13198 (anhydrous); 14656 (hydrate) Crystal system Tetragonal Space group Immm a, Å 16.2553 (6) b, Å 25.7909 (8) c, Å 37.1090 (12) α, ° 90 β, ° 90 γ, ° 90 Volume, Å.sup.3 15557.5 (9) Z 2 D.sub.calc, g/cm.sup.3 2.958 Absorption coefficient, mm.sup.−1 18.491 F (000) 11992.0 Theta range for data collection, ° 1.481 to 25.996 Completeness to Θ.sub.max % 99.3% Index ranges −20 <= h <= 20, −31 <= k <= 29, −45 <= l <= 45 Reflections collected 53073 Independent reflections 8182 R (int) 0.0875 Absorption correction Semi-empirical from equivalents Data/restraints/parameters 8182/0/228 Goodness-of-fit on F.sup.2 1.211 R.sub.1.sup.[a], wR.sub.2.sup.[b] (I > 2σ(I)) R.sub.1 = 0.0841, wR.sub.2 = 0.2432 R.sub.1.sup.[a], wR.sub.2.sup.[b] (all data) R.sub.1 = 0.1148, wR.sub.2 = 0.2621 .sup.[a]R.sub.1 = Σ | |F.sub.o| − |F.sub.c| | / Σ |F.sub.o|. .sup.[b]wR.sub.2 = [Σw(F.sub.o.sup.2 − F.sub.c.sup.2).sup.2/ Σw(F.sub.o.sup.2).sup.2].sup.1/2
Example 9
Structure of the “Pd.SUB.4.P.SUB.8.W.SUB.48.” Polyanion
[0331] The structure of the “Pd.sub.4P.sub.8W.sub.48” polyanion is displayed in
Example 10
.SUP.31.P NMR Spectrum of “K.SUB.20.Li.SUB.5.H.SUB.7.—Pd.SUB.4.P.SUB.8.W.SUB.48.”
[0332] “K.sub.20Li.sub.5H.sub.7—Pd.sub.4P.sub.8W.sub.48” crystals were dissolved in D.sub.2O. .sup.31P NMR spectrum was recorded at 20° C. on a 400 MHz JEOL ECX instrument, using 5 mm tube with resonance frequency 161.6 MHz. The chemical shift is reported with respect to the reference 85 wt % H.sub.3PO.sub.4. The .sup.31P NMR spectrum is shown in
Example 11
Synthesis of K.SUB.22.Li.SUB.10.H.SUB.2.[Ir.SUB.2.P.SUB.8.W.SUB.48.O.SUB.184.].129H.SUB.2.O
[0333] IrCl.sub.3 (0.032 g, 0.079 mmol) and K.sub.28Li.sub.5H.sub.7P.sub.8W.sub.48O.sub.184.92H.sub.2O (0.1 g, 0.0068 mmol (for preparation see, e. g. , Inorg. Chem. 1985, 24, 4610-4614; Inorg. Synth. 1990, 27, 110)) were dissolved in a mixture of 1 M lithium acetate solution (5 mL, pH 3.0), 200 μl of a 1 M lithium perchlorate solution and 25 μl propylene oxide. The solution was heated in a water bath to 80° C. for 30 min, then 0.5 ml of 30% H.sub.2O.sub.2 were added dropwise and the solution was stirred for an additional 30 min at 80° C. The final brown solution was allowed to cool to room temperature and left for crystallization in an open vial. Brown octahedral crystals formed after approximately 2 to 3 days, which were collected by filtration and air-dried after one week. Yield: 0.03 g (30% based on W). This product was analyzed by XRD, IR, elemental analysis, TGA and .sup.31P NMR and was identified as {Ir.sub.2[P.sub.8W.sub.48O.sub.184]}.sup.34− polyanion (“Ir.sub.2P.sub.8W.sub.48”), isolated as hydrated salt K.sub.22Li.sub.10H.sub.2[Ir.sub.2P.sub.8W.sub.48O.sub.184].129H.sub.2O (“K.sub.22Li.sub.10H.sub.2—Ir.sub.2P.sub.8W.sub.48”).
Example 12
Analysis of “K.SUB.22.Li.SUB.10.H.SUB.2.—Ir.SUB.2.P.SUB.8.W.SUB.48.”
[0334] The IR spectrum with 4 cm.sup.−1 resolution was recorded on a Nicolet Avatar 370 FT-IR spectrophotometer on KBr pellet sample (peak intensities: w=weak; m=medium; s=strong). The characteristic region of the polyanion is the fingerprint region or the region between 1000-400 cm-1 due to metal-oxygen stretching and bending vibrations: 1623 (s), 1384 (w), 1140 (s), 1088 (s), 1021 (m), 982(s), 932 (s), 919 (s), 814 (s), 693 (s), 572 (w), 528 (w), 464 (w). The FT-IR spectrum is shown in
[0335] Elemental analysis for “K.sub.22Li.sub.10H.sub.2—Ir.sub.2P.sub.8W.sub.48” calculated (found): K 5.67(5.67), Li 0.46(0.44), Ir 2.50(1.94), P 1.64(1.71), W 58.29(59.92).
[0336] Thermogravimetric analysis (TGA) was performed on a SDT Q 600 device from TA Instruments with 10-30 mg samples in 100 μL alumina pans, under a 100 mL/min N.sub.2 flow with a heating rate of 5° C./min between 20° C. and 800° C. (
Example 13
Single Crystal X-Ray Diffraction (XRD) Data and Analysis of “K.SUB.22.Li.SUB.10.H.SUB.2.—Ir.SUB.2.P.SUB.8.W.SUB.48.”
[0337] Besides IR, elemental analysis and TGA the product was also characterized by single-crystal XRD. The crystal was mounted in Hampton cryoloop at 100 K using light oil for data collection. Indexing and data collection were carried on a Bruker Kappa X8 APEX II CCD single crystal diffractometer with κ geometry and Mo Kα radiation (λ=0.71073 {acute over (Å)}). The SHELX software package (Bruker) was used to solve and refine the structure. An empirical absorption correction was applied using the SADABS program as disclosed in G. M. Sheldrick, SADABS, Program for empirical X-ray absorption correction, Bruker-Nonius: Madison, Wis. (1990). The structure was solved by direct method and refined by the full-matrix least squares method (Σw(|F.sub.o|.sup.2−|F.sub.c|.sup.2).sup.2) with anisotropic thermal parameters for all heavy atoms included in the model. The H atoms were not located. Also, it was not possible to locate all lithium and potassium counter cations by XRD, due to crystallographic disorder. The exact number of counter cations and crystal water in the POM were thus based on elemental analysis and TGA. Compound “K.sub.22Li.sub.10H.sub.2—Ir.sub.2P.sub.8W.sub.48” crystallizes in the tetragonal space group I4/m. Crystallographic data are detailed in Table 3.
TABLE-US-00003 TABLE 3 Crystal data for “K.sub.22Li.sub.10H.sub.2-Ir.sub.2P.sub.8W.sub.48” Empirical formula K.sub.22Li.sub.10H.sub.2[Ir.sub.2P.sub.8W.sub.48O.sub.184]•129H.sub.2O Formula weight, g/mol 15656 Crystal system Tetragonal Space group I4/m a, Å 25.298 (2) b, Å 25.298 (2) c, Å 21.6394 (16) α, ° 90 β, ° 90 γ, ° 90 Volume, Å.sup.3 13849 (2) Z 4 D.sub.calc, g/cm.sup.3 3.148 Absorption coefficient, mm.sup.−1 21.104 F (000) 11308.0 Theta range for data collection, ° 1.138 to 26.496 Completeness to Θ.sub.max % 99.6% Index ranges −31 <= h <= 31, −31 <= k <= 31, −22 <= l <= 27 Reflections collected 179129 Independent reflections 7352 R (int) 0.1167 Absorption correction Semi-empirical from equivalents Data/restraints/parameters 7352/0/332 Goodness-of-fit on F.sup.2 1.054 R.sub.1.sup.[a], wR.sub.2.sup.[b] (I > 2σ(I)) R.sub.1 = 0.0696, wR.sub.2 = 0.2158 R.sub.1.sup.[a], wR.sub.2.sup.[b] (all data) R.sub.1 = 0.1189, wR.sub.2 = 0.2808 .sup.[a]R.sub.1 = Σ | |F.sub.o| − |F.sub.c| | / Σ |F.sub.o|. .sup.[b]wR.sub.2 = [Σw(F.sub.o.sup.2 − F.sub.c.sup.2).sup.2/ Σw(F.sub.o.sup.2).sup.2].sup.1/2
Example 14
Structure of the “Ir.SUB.2.P.SUB.8.W.SUB.48.” Polyanion
[0338] The structure of the “Ir.sub.2P.sub.8W.sub.48” polyanion is displayed in
Example 15
.SUP.31.P NMR Spectrum of “K.SUB.22.Li.SUB.10.H.SUB.2.—Ir.SUB.2.P.SUB.8.W.SUB.48.”
[0339] “K.sub.22Li.sub.10H.sub.2—Ir.sub.2P.sub.8W.sub.48” crystals were dissolved in D.sub.2O. .sup.31P NMR spectrum was recorded at 20° C. on a 400 MHz JEOL ECX instrument, using 5 mm tube with resonance frequency 161.6 MHz. The chemical shift is reported with respect to the reference 85 wt % H.sub.3PO.sub.4. The .sup.31P NMR spectrum is shown in
Example 16
Synthesis of K.SUB.29.Li.SUB.2.H.SUB.5.[Pt.SUB.2.P.SUB.8.W.SUB.48.O.SUB.184.].91H.SUB.2.O
[0340] K.sub.2PtCl.sub.4 (0.028 g, 0.067 mmol) and K.sub.28Li.sub.5H.sub.7P.sub.8W.sub.48O.sub.184.92H.sub.2O (0.05 g, 0.0034 mmol (for preparation see, e.g., Inorg. Chem. 1985, 24, 4610-4614; Inorg. Synth. 1990, 27, 110)) was dissolved in a mixture of 1 M lithium acetate solution (5 mL, pH 3.0) and 500 μl of a 1 M lithium perchlorate solution. The solution was then heated in a water bath at 80° C. for 60 min. The final orange solution was allowed to cool to room temperature and left for crystallization in an open vial. Orange octahedral crystals started to form after approximately 2 to 3 days, which were collected by filtration and air-dried after two weeks. Yield: 0.027 g (55% based on W). This product was analyzed by XRD, IR, elemental analysis, TGA and .sup.31P NMR and was identified as {Pt.sub.2[P.sub.8W.sub.48O.sub.184]}.sup.36− polyanion (“Pt.sub.2P.sub.8W.sub.48”), isolated as hydrated salt K.sub.29Li.sub.2H.sub.5[Pt.sub.2P.sub.8W.sub.48O.sub.184].91H.sub.2O (“K.sub.29Li.sub.2H.sub.5—Pt.sub.2P.sub.8W.sub.48”).
Example 17
Analysis of “K.SUB.29.Li.SUB.2.H.SUB.5.—Pt.SUB.2.P.SUB.8.W.SUB.48.”
[0341] The IR spectrum with 4 cm.sup.−1 resolution was recorded on a Nicolet Avatar 370 FT-IR spectrophotometer on KBr pellet sample (peak intensities: w=weak; m=medium; s=strong). The characteristic region of the polyanion is the fingerprint region or the region between 1000-400 cm-1 due to metal—oxygen stretching and bending vibrations: 1627 (s), 1140 (s), 1087(s), 1018 (m), 979 (w), 933 (s), 918 (s), 819 (s), 693 (s), 574 (w), 533 (w), 461 (w). The FT-IR spectrum is shown in
[0342] Elemental analysis for “K.sub.29Li.sub.2H.sub.5—Pt.sub.2P.sub.8W.sub.48” calculated (found): K 7.4 (7.1), Li 0.09 (0.7), Pt 2.56 (1.86), P 1.77 (1.63), W 58.2 (59.2).
[0343] Thermogravimetric analysis (TGA) was performed on a SDT Q 600 device from TA Instruments with 10-30 mg samples in 100 μL alumina pans, under a 100 mL/min N.sub.2 flow with a heating rate of 5° C./min between 20° C. and 800° C. (
Example 18
Single Crystal X-Ray Diffraction (XRD) Data and Analysis of “K.SUB.29.Li.SUB.2.H.SUB.5.—Pt.SUB.2.P.SUB.8.W.SUB.48.”
[0344] Besides IR, elemental analysis and TGA the product was also characterized by single-crystal XRD. The crystal was mounted in Hampton cryoloop at 100 K using light oil for data collection. Indexing and data collection were carried on a Bruker Kappa X8 APEX II CCD single crystal diffractometer with κ geometry and Mo Kα radiation (λ=0.71073 {acute over (Å)}). The SHELX software package (Bruker) was used to solve and refine the structure. An empirical absorption correction was applied using the SADABS program as disclosed in G. M. Sheldrick, SADABS, Program for empirical X-ray absorption correction, Bruker-Nonius: Madison, Wis. (1990). The structure was solved by direct method and refined by the full-matrix least squares method (Σw(|F.sub.o|.sup.2−|F.sub.c|.sup.2).sup.2) with anisotropic thermal parameters for all heavy atoms included in the model. The H atoms were not located. Also, it was not possible to locate all lithium and potassium counter cations by XRD, due to crystallographic disorder. The exact number of counter cations and crystal water in the POM were thus based on elemental analysis and TGA. Compound “K.sub.29Li.sub.2H.sub.5—Pt.sub.2P.sub.8W.sub.48” crystallizes in the tetragonal space group I4/m. Crystallographic data are detailed in Table 4.
TABLE-US-00004 TABLE 4 Crystal data for “K.sub.29Li.sub.2H.sub.5-Pt.sub.2P.sub.8W.sub.48” Empirical formula K.sub.29Li.sub.2H.sub.5[Pt.sub.2P.sub.8W.sub.48O.sub.184]•91H.sub.2O Formula weight, g/mol 15192 Crystal system Tetragonal Space group I4/m a, Å 25.488 (2) b, Å 25.488 (2) c, Å 21.7089 (16) α, ° 90 β, ° 90 γ, ° 90 Volume, Å.sup.3 14103 (2) Z 4 D.sub.calc, g/cm.sup.3 3.407 Absorption coefficient, mm.sup.−1 20.921 F (000) 12640.0 Theta range for data collection, ° 1.130 to 25.995 Completeness to Θ.sub.max % 99.8% Index ranges −31 <= h <= 31, −31 <= k <= 24, −26 <= l <= 26 Reflections collected 42847 Independent reflections 7125 R (int) 0.0594 Absorption correction Semi-empirical from equivalents Data/restraints/parameters 7125/0/223 Goodness-of-fit on F.sup.2 1.134 R.sub.1.sup.[a], wR.sub.2.sup.[b] (I > 2σ(I)) R.sub.1 = 0.0506, wR.sub.2 = 0.1617 R.sub.1.sup.[a], wR.sub.2.sup.[b] (all data) R.sub.1 = 0.0747, wR.sub.2 = 0.1960 .sup.[a]R.sub.1 = Σ | |F.sub.o| − |F.sub.c| | / Σ |F.sub.o|. .sup.[b]wR.sub.2 = [Σw(F.sub.o.sup.2 − F.sub.c.sup.2).sup.2/ Σw(F.sub.o.sup.2).sup.2].sup.1/2
Example 19
Structure of the “Pt.SUB.2.P.SUB.8.W.SUB.48.” Polyanion
[0345] The structure of the “Pt.sub.2P.sub.8W.sub.48” polyanion is displayed in
Example 20
.SUP.31.P NMR Spectrum of “K.SUB.29.Li.SUB.2.H.SUB.5.—Pt.SUB.2.P.SUB.8.W.SUB.48.”
[0346] “K.sub.29Li.sub.2H.sub.5—Pt.sub.2P.sub.8W.sub.48” crystals were dissolved in D.sub.2O. .sup.31P NMR spectrum was recorded at 20° C. on a 400 MHz JEOL ECX instrument, using 5 mm tube with resonance frequency 161.6 MHz. The chemical shift is reported with respect to the reference 85 wt % H.sub.3PO.sub.4. The .sup.31P NMR spectrum is shown in
Example 21
Synthesis of Supported POMs (“K.SUB.20.Li.SUB.8.—Rh.SUB.4.P.SUB.8.W.SUB.48.”, “K.SUB.20.Li.SUB.5.H.SUB.7.—Pd.SUB.4.P.SUB.8.W.SUB.48.”, “K.SUB.22.Li.SUB.10.H.SUB.2.—Ir.SUB.2.P.SUB.8.W.SUB.48.” and “K.SUB.29.Li.SUB.2.H.SUB.5.—Pt.SUB.2.P.SUB.8.W.SUB.48.”)
Synthesis of Mesoporous Silica Support SBA-15
[0347] 8.0 g of Pluronic® P-123 gel (Sigma-Aldrich) were added to 40 mL of 2 M HCl and 208 mL H.sub.2O. This mixture was stirred for 2 hours in a water bath at 35° C. until it was completely dissolved. Then 18 mL of tetraethylorthosilicate (TEOS) was added dropwise, and the mixture was kept under stirring for 4 hours. Afterwards, the mixture was heated in an oven at 95° C. for 3 days. The white precipitate was collected by filtration, washed and air-dried. Finally, the product was calcined by heating the as-synthesized material to 550° C. at a rate of 1-2° C./min and kept at 550° C. for 6 hours to remove the templates.
Synthesis of Modified SBA-15-apts
[0348] 1.61 mL of 3-aminopropyltriethoxysilane (apts) was added to 3 g of SBA-15, prepared according to the synthesis described above, in 90 mL toluene. This mixture was refluxed for 5 hours and then filtered at room temperature. The obtained modified SBA-15-apts was heated at 100° C. for 5 hours.
Preparation of POMs Supported on SBA-15-apts (“Supported POMs”, i.e., Supported “K.sub.20Li.sub.8—Rh.sub.4P.sub.8W.sub.48”, Supported “K.sub.20Li.sub.5H.sub.7—Pd.sub.4P.sub.8W.sub.48”, Supported “K.sub.22Li.sub.10H.sub.2—Ir.sub.2P.sub.8W.sub.48” and Supported “K.sub.29Li.sub.2H.sub.5—Pt.sub.2P.sub.8W.sub.48”)
[0349] The respective POM (“K.sub.20Li.sub.8—Rh.sub.4P.sub.8W.sub.48”, “K.sub.20Li.sub.5H.sub.7—Pd.sub.4P.sub.8W.sub.48”, “K.sub.22Li.sub.10H.sub.2—Ir.sub.2P.sub.8W.sub.48” or “K.sub.29Li.sub.2H.sub.5—Pt.sub.2P.sub.8W.sub.48”) was dissolved in water (0.056 mmol/L), resulting in a colored solution. While stirring, SBA-15-apts was slowly added to the solution of the POM so that the respective amounts of the POM and SBA-15-apts were 5 wt % and 95 wt %, respectively. The mixture was kept under stirring for 24 hours at 40° C., filtered and then washed three times with water. The filtrate was colorless, indicating that the respective POM was quantitatively loaded on the SBA-15-apts support, resulting in a supported POM loading level on the solid support of about 5 wt %. The supported product was then collected and air-dried.
Example 22
Activation of Supported POM and Preparation of Supported POM-Derived Metal Cluster Units (Supported “K.SUB.20.Li.SUB.8.—Rh.SUB.4.P.SUB.8.W.SUB.48.”-Derived Metal Cluster Unit, Supported “K.SUB.20.Li.SUB.5.H.SUB.7.—Pd.SUB.4.P.SUB.8.W.SUB.48.”-Derived Metal Cluster Unit, Supported “K.SUB.22.Li.SUB.10.H.SUB.2.—Ir.SUB.2.P.SUB.8.W.SUB.48.”-Derived Metal Cluster Unit and Supported “K.SUB.29.Li.SUB.2.H.SUB.5.—Pt.SUB.2.P.SUB.8.W.SUB.48.”-Derived Metal Cluster Unit)
[0350] The supported POMs prepared according to example 21 were activated or transformed into the corresponding supported metal cluster units.
[0351] In a first example 22a, supported POMs prepared according to example 21 were activated by air calcination at 300° C. for 3 hours. In a second example 22b, supported POMs prepared according to example 21 were converted into corresponding supported POM-derived metal cluster units by H.sub.2 reduction at 300° C., 50 bar for 24 hours. In a third example 22c, supported POMs prepared according to example 21 were treated by the same method of example 22b, but followed with air calcination at 550° C. for 4.5 hours. In a fourth example 22d, supported POMs prepared according to example 21 were converted into corresponding supported POM-derived metal cluster units by a chemical reduction conducted by suspending 100 mg of supported POM in 15 mL of water followed by the addition of about 0.25 mL of hydrazine hydrate. The resulting solution was stirred for 12 hours, filtered, dried and then air calcined at 300° C. for 3 hours.
[0352] Without being bound by any theory, it is believed that calcination and optional hydrogenation or chemical reduction helps to activate the POMs by forming active sites.
Example 23
Activation of Supported POM and Preparation of Supported POM-Derived Metal Cluster Units (Supported “K.SUB.20.Li.SUB.8.—Rh.SUB.4.P.SUB.8.W.SUB.48.”-Derived Metal Cluster Unit, Supported “K.SUB.20.Li.SUB.5.H.SUB.7.—Pd.SUB.4.P.SUB.8.W.SUB.48.”-Derived Metal Cluster Unit, Supported “K.SUB.22.Li.SUB.10.H.SUB.2.—Ir.SUB.2.P.SUB.8.W.SUB.48.”-Derived Metal Cluster Unit and Supported “K.SUB.29.Li.SUB.2.H.SUB.5.—Pt.SUB.2.P.SUB.8.W.SUB.48.”-Derived Metal Cluster Unit)
[0353] The supported POMs prepared according to example 21 were activated by air calcination and then transformed into the corresponding supported “supported POM-derived metal cluster units by H.sub.2 reduction.
[0354] In a first example 23a, supported POMs prepared according to example 21 were activated by air calcination at 150° C. for 1 hour. In a second example 23b, supported POMs prepared according to example 21 were activated by air calcination at 200° C. for 1 hour. In a third example 23c, supported POMs prepared according to example 21 were activated by air calcination at 300° C. for 30 minutes. In a fourth example 23d, supported POMs prepared according to example 21 were activated by air calcination at 550° C. for 30 minutes.
[0355] The activated supported POMs of examples 23a, 23b, 23c and 23d were converted into corresponding supported POM-derived metal cluster units by H.sub.2 reduction at 240° C. and 60 bar under stirring at 1500 rpm for 1-2 minutes. The H.sub.2 reduction was conducted in-situ prior to the further use of the supported POM-derived metal cluster units in order to provide fresh supported POM-derived metal cluster units.
[0356] Without being bound by any theory, it is believed that calcination and hydrogenation helps to activate the POMs by forming active sites.
Example 24
Synthesis of K.SUB.16.Li.SUB.10.H.SUB.6.[(Rh-Cp*).SUB.4.P.SUB.8.W.SUB.48.(H.SUB.2.O).SUB.4.O.SUB.184.].79H.SUB.2.O
[0357] (RhCp*Cl.sub.2).sub.2 (C.sub.20H.sub.30Cl.sub.4Rh.sub.2, 0.009 g, 0.014 mmol) and K.sub.28Li.sub.5H.sub.7P.sub.8W.sub.48O.sub.184.92H.sub.2O (0.1 g, 0.0068 mmol (for preparation see, e.g., Inorg. Chem. 1985, 24, 4610-4614; Inorg. Synth. 1990, 27, 110)) were dissolved in 1 M lithium acetate solution (5 mL, pH 6.0). While stirring, 250 μl of a 1 M lithium perchlorate solution were added. The solution was heated in a water bath at 75° C. for 30 min. The resulting clear orange solution was allowed to cool to room temperature and left for crystallization in an open vial. Orange crystals formed after approximately 2 to 3 days, which were collected by filtration and air-dried. Yield: 75 mg (70% based on W). This product was analyzed by XRD, IR, TGA, .sup.31P and .sup.13C NMR and was identified as {(Rh-Cp*).sub.4[P.sub.8W.sub.48O.sub.184]}.sup.32− polyanion (“(RhCp*).sub.4P.sub.8W.sub.48”), isolated as hydrated salt K.sub.16Li.sub.10H.sub.6[(Rh-Cp*).sub.4P.sub.8W.sub.48(H.sub.2O).sub.4O.sub.184].79H.sub.2O (“K.sub.16Li.sub.10H.sub.6—(RhCp*).sub.4P.sub.8W.sub.48”).
Example 25
Analysis of “K.SUB.16.Li.SUB.10.H.SUB.6.—(RhCp*).SUB.4.P.SUB.8.W.SUB.48.”
[0358] The IR spectrum with 4 cm.sup.−1 resolution was recorded on a Nicolet Avatar 370 FT-IR spectrophotometer on KBr pellet sample (peak intensities: w=weak; m=medium; s=strong). The characteristic region of the polyanion is the fingerprint region or the region between 1000-400 cm.sup.−1 due to metal-oxygen stretching and bending vibrations: 2922 (w), 2854 (w), 1616 (s), 1383 (w), 1134 (s), 1080 (s), 987 (m), 925 (s), 804 (s), 677 (s), 569 (w), 516 (w), 461 (w). The FT-IR spectrum is shown in
[0359] Thermogravimetric analysis (TGA) was performed on a SDT Q 600 device from TA Instruments with 10-30 mg samples in 100 μL alumina pans, under a 100 mL/min N.sub.2 flow with a heating rate of 3-5° C./min between 20° C. and 800° C. (
Example 26
Single Crystal X-Ray Diffraction (XRD) Data and Analysis of “K.SUB.16.Li.SUB.10.H.SUB.6.—(RhCp*).SUB.4.P.SUB.8.W.SUB.48.”
[0360] The product was also characterized by single-crystal XRD. The crystal was mounted in a Hampton cryoloop at 100 K using light oil for data collection. Indexing and data collection were carried on a Bruker Kappa X8 APEX II CCD single crystal diffractometer with κ geometry and Mo Kα radiation (λ=0.71073 {acute over (Å)}). The SHELX software package (Bruker) was used to solve and refine the structure. An empirical absorption correction was applied using the SADABS program as disclosed in G. M. Sheldrick, SADABS, Program for empirical X-ray absorption correction, Bruker-Nonius: Madison, Wis. (1990). The structure was solved by direct method and refined by the full-matrix least squares method (Σw(|F.sub.o|.sup.2−|F.sub.c|.sup.2).sup.2) with anisotropic thermal parameters for all heavy atoms included in the model. The H atoms were not located. Also, it was not possible to locate all counter cations by XRD, due to crystallographic disorder. Compound “K.sub.16Li.sub.10H.sub.6—(RhCp*).sub.4P.sub.8W.sub.48” crystallizes in the triclinic space group P-1.
[0361] Crystallographic data are detailed in Table 5.
TABLE-US-00005 TABLE 5 Crystal data for “K.sub.16Li.sub.10H.sub.6-(RhCp*).sub.4P.sub.8W.sub.48” Empirical formula K.sub.16Li.sub.10H.sub.6(Rh-CP*).sub.4 P.sub.8W.sub.48(H.sub.2O).sub.4O.sub.184•79H.sub.2O Formula weight, g/mol — Crystal system Triclinic Space group P-1 a, Å 19.9112 (17) b, Å 22.6883 (19) c, Å 37.535 (3) α, ° 80.624 (3) β, ° 76.490 (2) γ, ° 83.367 (3) Volume, Å.sup.3 16214 (2) Z 2 D.sub.calc, g/cm.sup.3 3.908 Absorption coefficient, mm.sup.−1 26.106 F (000) 16344 Theta range for data collection, ° 1.347 to 25.027 Completeness to Θ.sub.max % 100% Index ranges −23 <= h <= 23, −27 <= k <= 27, −44 <= l <= 44 Reflections collected 327569 Independent reflections 57250 R (int) 0.2132 Absorption correction Semi-empirical from equivalents Data/restraints/parameters 57250/48/1677 Goodness-of-fit on F.sup.2 1.053 R.sub.1.sup.[a], wR.sub.2.sup.[b] (I > 2σ(I)) R.sub.1 = 0.0863, wR.sub.2 = 0.2225 R.sub.1.sup.[a], wR.sub.2.sup.[b] (all data) R.sub.1 = 0.1582, wR.sub.2 = 0.2723 .sup.[a]R.sub.1 = Σ | |F.sub.o| − |F.sub.c| | / Σ |F.sub.o|. .sup.[b]wR.sub.2 = [Σw(F.sub.o.sup.2 − F.sub.c.sup.2).sup.2/ Σw(F.sub.o.sup.2).sup.2].sup.1/2
Example 27
Structure of the “(RhCp*).SUB.4.P.SUB.8.W.SUB.48.” Polyanion
[0362] The structure of the “(RhCp*).sub.4P.sub.8W.sub.48” polyanion is displayed in
Example 28
.SUP.31.P NMR Spectrum of “K.SUB.16.Li.SUB.10.H.SUB.6.—(RhCp*).SUB.4.P.SUB.8.W.SUB.48.”
[0363] “K.sub.16Li.sub.10H.sub.6—(RhCp*).sub.4P.sub.8W.sub.48” crystals were dissolved in D.sub.2O. .sup.31P NMR spectrum was recorded at 20° C. on a 400 MHz JEOL ECX instrument, using 5 mm tube with resonance frequency 161.9 MHz. The chemical shift is reported with respect to the reference 85 wt % H.sub.3PO.sub.4. The .sup.31P NMR spectrum is shown in
Example 29
.SUP.13.C NMR Spectrum of “K.SUB.16.Li.SUB.10.H.SUB.6.—(RhCp*).SUB.4.P.SUB.8.W.SUB.48.”
[0364] “K.sub.16Li.sub.10H.sub.6—(RhCp*).sub.4P.sub.8W.sub.48” crystals were dissolved in D.sub.2O. .sup.13C NMR spectrum was recorded at 20° C. on a 400 MHz JEOL ECX instrument, using 5 mm tube with resonance frequency 100.71 MHz. The chemical shift is reported with respect to the reference Si(CH.sub.3).sub.4. The .sup.13C NMR spectrum is shown in
Example 30
Synthesis of K.SUB.n1.Li.SUB.n2.H.SUB.n3.[(Rh-Cp*).SUB.4.P.SUB.8.W.SUB.49.(H.SUB.2.O).SUB.4.O.SUB.188.].wH.SUB.2.O
[0365] (RhCp*Cl.sub.2).sub.2 (C.sub.20H.sub.30Cl.sub.4Rh.sub.2 (0.009 g, 0.014 mmol) and K.sub.16Li.sub.2H.sub.6P.sub.4W.sub.24O.sub.94.33H.sub.2O (0.05 g, 0.0068 mmol) were dissolved in a mixture of 1 M sodium acetate solution (3 mL, pH 6.0). While stirring, 250 μl of a 1 M lithium perchlorate solution were added. The solution was heated in a water bath at 60° C. for 30 min, centrifuged to remove the turbidity and left for crystallization. The resulting orange solution was allowed to cool to room temperature and left for crystallization in an open vial. Orange-yellow needles formed after approximately 2 to 3 days, which were collected by filtration and air-dried after one week. This product was analyzed by XRD and IR and was identified as {(Rh-Cp*).sub.4[P.sub.8W.sub.49O.sub.188]}.sup.30− polyanion (“(RhCp*).sub.4P.sub.8W.sub.49”), isolated as hydrated salt K.sub.n1Li.sub.n2H.sub.n3[(Rh-Cp*).sub.4P.sub.8W.sub.49(H.sub.2O).sub.4O.sub.188].wH.sub.2O (“A.sub.30-(RhCp*).sub.4P.sub.8W.sub.49”). The exact counter cation composition and amount of water molecules were not identified.
Example 31
Analysis of “A.SUB.30.-(RhCp*).SUB.4.P.SUB.8.W.SUB.49.”
[0366] The IR spectrum with 4 cm.sup.−1 resolution was recorded on a Nicolet Avatar 370 FT-IR spectrophotometer on KBr pellet sample (peak intensities: w=weak; m=medium; s=strong). The characteristic region of the polyanion is the fingerprint region or the region between 1000-400 cm.sup.−1 due to metal-oxygen stretching and bending vibrations: 2923 (w), 2853 (w), 1633 (s), 1569 (m), 1413 (w), 1134 (s), 1084 (s), 1015 (m), 977 (w), 921 (s), 806 (s), 689 (s), 575 (w), 534 (w), 460 (w). The FT-IR spectrum is shown in
Example 32
Single Crystal X-Ray Diffraction (XRD) Data and Analysis of “A.SUB.n.-(RhCp*).SUB.4.P.SUB.8.W.SUB.49.”
[0367] The product was also characterized by single-crystal XRD. The crystal was mounted in a Hampton cryoloop at 100 K using light oil for data collection. Indexing and data collection were carried on a Bruker Kappa X8 APEX II CCD single crystal diffractometer with κ geometry and Mo Kα radiation (λ=0.71073 {acute over (Å)}). The SHELX software package (Bruker) was used to solve and refine the structure. An empirical absorption correction was applied using the SADABS program as disclosed in G. M. Sheldrick, SADABS, Program for empirical X-ray absorption correction, Bruker-Nonius: Madison, Wis. (1990). The structure was solved by direct method and refined by the full-matrix least squares method (Σw(|F.sub.o|.sup.2−|F.sub.c|.sup.2).sup.2) with anisotropic thermal parameters for all heavy atoms included in the model. The H atoms were not located. Also, it was not possible to locate all counter cations by XRD, due to crystallographic disorder. Compound “A.sub.30-(RhCp*).sub.4P.sub.8W.sub.49” crystallizes in the monoclinic space group P 21/n. Crystallographic data are detailed in Table 6.
TABLE-US-00006 TABLE 6 Crystal data for “A.sub.30-(RhCp*).sub.4P.sub.8W.sub.49” Empirical formula K.sub.n1Li.sub.n2H.sub.n3(Rh-Cp*).sub.4 P.sub.8W.sub.49(H.sub.2O).sub.4•wH.sub.2O Formula weight, g/mol — Crystal system Monoclinic Space group P 21/n a, Å 24.696 (2) b, Å 29.818 (3) c, Å 47.445 (4) α, ° 90 β, ° 96.989 (3) γ, ° 90 Volume, Å.sup.3 34678 (5) Z 4 D.sub.calc, g/cm.sup.3 4.961 Absorption coefficient, mm.sup.−1 39.677 F (000) 43200 Theta range for data collection, ° 1.366 to 26.466 Completeness to Θ.sub.max % 100% Index ranges −30 <= h <= 30, −37 <= k <= 37, −59 <= l <= 59 Reflections collected 603974 Independent reflections 71303 R (int) 0.2345 Absorption correction Semi-empirical from equivalents Data/restraints/parameters 71303/0/1577 Goodness-of-fit on F.sup.2 1.095 R.sub.1.sup.[a], wR.sub.2.sup.[b] (I > 2σ(I)) R.sub.1 = 0.1047, wR.sub.2 = 0.2413 R.sub.1.sup.[a], wR.sub.2.sup.[b] (all data) R.sub.1 = 0.1963, wR.sub.2 = 0.2998 .sup.[a]R.sub.1 = Σ | |F.sub.o| − |F.sub.c| | / Σ |F.sub.o|. .sup.[b]wR.sub.2 = [Σw(F.sub.o.sup.2 − F.sub.c.sup.2).sup.2/ Σw(F.sub.o.sup.2).sup.2].sup.1/2
Example 33
Structure of the “(RhCp*).SUB.4.P.SUB.8.W.SUB.49.” Polyanion
[0368] The structure of the “(RhCp*).sub.4P.sub.8W.sub.49” polyanion can be described as a wheel-shaped {P.sub.8W.sub.48O.sub.184} unit encapsulating four pentamethylcyclopentadienyl rhodium (RhCp*) units located slightly outside the cavity due to the steric effect of the pentamethylcyclopentadiene, similarly to the structure disclosed in
Example 34
Synthesis of K.SUB.16.Li.SUB.10.H.SUB.6.[(Ir-Cp*).SUB.4.P.SUB.8.W.SUB.48.(H.SUB.2.O).SUB.4.O.SUB.184.].101H.SUB.2.O
[0369] (IrCp*Cl.sub.2).sub.2 (C.sub.20H.sub.30Cl.sub.4Ir.sub.2, 0.011 g, 0.014 mmol) and K.sub.28Li.sub.5H.sub.7P.sub.8W.sub.48O.sub.184.92H.sub.2O (0.10 g, 0.0034 mmol (for preparation see, e.g., Inorg. Chem. 1985, 24, 4610-4614; Inorg. Synth. 1990, 27, 110)) were dissolved in a mixture of 1 M sodium acetate solution (3 mL, pH 4.0). While stirring, 250 μl of a 1 M lithium perchlorate solution were added. The solution was heated in a water bath at 75-80° C. for 30 min, centrifuged to remove the turbidity and left for crystallization. The resulting orange solution was allowed to cool to room temperature and left for crystallization in an open vial. Orange-yellow needles formed after approximately 2 to 3 days, which were collected by filtration and air-dried after three days. Yield: 60 mg (56% based on W). This product was analyzed by XRD, IR, elemental analysis, TGA, .sup.31P NMR and .sup.13C NMR and was identified as {(Ir-Cp*).sub.4[P.sub.8W.sub.48O.sub.184]}.sup.32− polyanion (“(IrCp*).sub.4P.sub.8W.sub.48”), isolated as hydrated salt K.sub.16Li.sub.10H.sub.6[(Ir-Cp*).sub.4P.sub.8W.sub.48(H.sub.2O).sub.4O.sub.184].wH.sub.2O (“K.sub.16Li.sub.10H.sub.6—(IrCp*).sub.4P.sub.8W.sub.48”).
Example 35
Analysis of “K.SUB.16.Li.SUB.10.H.SUB.6.—(IrCp*).SUB.4.P.SUB.8.W.SUB.48.”
[0370] The IR spectrum with 4 cm.sup.−1 resolution was recorded on a Nicolet Avatar 370 FT-IR spectrophotometer on KBr pellet sample (peak intensities: w=weak; m=medium; s=strong). The characteristic region of the polyanion is the fingerprint region or the region between 1000-400 cm.sup.−1 due to metal-oxygen stretching and bending vibrations: 2924 (w), 1626 (s), 1384 (w), 1136 (s), 1086 (s), 1020 (m), 928 (s), 808 (s), 688 (s), 573 (w), 532 (w), 463 (w). The FT-IR spectrum is shown in
[0371] Elemental analysis for “K.sub.16Li.sub.10H.sub.6—(IrCp*).sub.4P.sub.8W.sub.48” calculated (found): K 3.92(3.90), Li 0.44 (0.45), Ir 4.83 (4.82), P 1.56 (1.61), W 55.43 (55.82).
[0372] Thermogravimetric analysis (TGA) was performed on a SDT Q 600 device from TA Instruments with 10-30 mg samples in 100 μL alumina pans, under a 100 mL/min N.sub.2 flow with a heating rate of 5° C./min between 20° C. and 800° C. (
Example 36
Single Crystal X-Ray Diffraction (XRD) Data and Analysis of “K.SUB.16.Li.SUB.10.H.SUB.6.—(IrCp*).SUB.4.P.SUB.8.W.SUB.48.”
[0373] The product was also characterized by single-crystal XRD. The crystal was mounted in a Hampton cryoloop at 100 K using light oil for data collection. Indexing and data collection were carried on a Bruker Kappa X8 APEX II CCD single crystal diffractometer with κ geometry and Mo Kα radiation (λ=0.71073 {acute over (Å)}). The SHELX software package (Bruker) was used to solve and refine the structure. An empirical absorption correction was applied using the SADABS program as disclosed in G. M. Sheldrick, SADABS, Program for empirical X-ray absorption correction, Bruker-Nonius: Madison, Wis. (1990). The structure was solved by direct method and refined by the full-matrix least squares method (Σw(|F.sub.o|.sup.2−|F.sub.c|.sup.2).sup.2) with anisotropic thermal parameters for all heavy atoms included in the model. The H atoms were not located. Also, it was not possible to locate all counter cations by XRD, due to crystallographic disorder. Compound “K.sub.16Li.sub.10H.sub.6—(IrCp*).sub.4P.sub.8W.sub.48” crystallizes in the triclinic space group P-1. Crystallographic data are detailed in Table 7.
TABLE-US-00007 TABLE 7 Crystal data for “K.sub.16Li.sub.10H.sub.6-(IrCp*).sub.4P.sub.8W.sub.48” Empirical formula K.sub.16Li.sub.10H.sub.6(Ir-Cp*).sub.4 P.sub.8W.sub.48(H.sub.2O).sub.4O.sub.184•wH.sub.2O Formula weight, g/mol — Crystal system Triclinic Space group P-1 a, Å 23.3584 (19) b, Å 28.210 (2) c, Å 29.917 (2) α, ° 68.540 (2) β, ° 89.697 (3) γ, ° 69.867 (2) Volume, Å.sup.3 17061 (2) Z 2 D.sub.calc, g/cm.sup.3 4.582 Absorption coefficient, mm.sup.−1 32.326 F (000) 20096 Theta range for data collection, ° 1.386 to 27.609 Completeness to Θ.sub.max % 99.9% Index ranges −30 <= h <= 30, −36 <= k <= 36, −38 <= l <= 38 Reflections collected 325517 Independent reflections 78692 R (int) 0.1749 Absorption correction Semi-empirical from equivalents Data/restraints/parameters 78692/0/1540 Goodness-of-fit on F.sup.2 1.038 R.sub.1.sup.[a], wR.sub.2.sup.[b] (I > 2σ(I)) R.sub.1 = 0.0966, wR.sub.2 = 0.2462 R.sub.1.sup.[a], wR.sub.2.sup.[b] (all data) R.sub.1 = 0.1986, wR.sub.2 = 0.3175 .sup.[a]R.sub.1 = Σ | |F.sub.o| − |F.sub.c| | / Σ |F.sub.o|. .sup.[b]wR.sub.2 = [Σw(F.sub.o.sup.2 − F.sub.c.sup.2).sup.2/ Σw(F.sub.o.sup.2).sup.2].sup.1/2
Example 37
Structure of the “(IrCp*).SUB.4.P.SUB.8.W.SUB.48.” Polyanion
[0374] The structure of the “(IrCp*).sub.4P.sub.8W.sub.48” polyanion is displayed in
Example 38
.SUP.31.P NMR Spectrum of “K.SUB.16.Li.SUB.10.H.SUB.6.—(IrCp*).SUB.4.P.SUB.8.W.SUB.48.”
[0375] “K.sub.16Li.sub.10H.sub.6—(IrCp*).sub.4P.sub.8W.sub.48” crystals were dissolved in D.sub.2O. .sup.31P NMR spectrum was recorded at 20° C. on a 400 MHz JEOL ECX instrument, using 5 mm tube with resonance frequency 161.9 MHz. The chemical shift is reported with respect to the reference 85 wt % H.sub.3PO.sub.4. The .sup.31P NMR spectrum is shown in
Example 39
.SUP.13.C NMR Spectrum of “K.SUB.16.Li.SUB.10.H.SUB.6.—(IrCp*).SUB.4.P.SUB.8.W.SUB.48.”
[0376] “K.sub.16Li.sub.10H.sub.6—(IrCp*).sub.4P.sub.8W.sub.48” crystals were dissolved in D.sub.2O. .sup.13C NMR spectrum was recorded at 20° C. on a 400 MHz JEOL ECX instrument, using 5 mm tube with resonance frequency 100.71 MHz. The chemical shift is reported with respect to the reference Si(CH.sub.3).sub.4. The .sup.13C NMR spectrum is shown in
[0377] All documents described herein are incorporated by reference herein, including any priority documents and/or testing procedures to the extent they are not inconsistent with this text. As is apparent from the foregoing general description and the specific embodiments, while forms of the invention have been illustrated and described, various modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited thereby. Likewise, the term “comprising” is considered synonymous with the term “including” for purposes of Australian law.
[0378] Additionally or alternately, the invention relates to:
[0379] Embodiment 1: A polyoxometalate represented by the formula
(A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−
or solvates thereof, wherein [0380] each A independently represents a cation, [0381] n is the number of cations, [0382] each M is independently selected from the group consisting of Pd, Pt, Rh, Ir, Ag and Au, [0383] each X is independently selected from the group consisting of P, As, Se and Te, [0384] each R is independently selected from the group consisting of monovalent anions, [0385] each R′ is independently selected from the group consisting of organometallic ligands, [0386] s is a number from 2 to 12, [0387] y is a number from 0 to 24, [0388] q is a number from 0 to 24, [0389] z is a number selected from 0 or 1, [0390] t is a number selected from 0 or 1, [0391] r is 0, 1 or 2, and [0392] m is a number representing the total positive charge m+ of n cations A and the corresponding negative charge m− of the polyanion [(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].
[0393] Embodiment 2: Polyoxometalate according to embodiment 1, wherein X.sub.8W.sub.48+rO.sub.184+4r forms a {X.sub.8W.sub.48+rO.sub.184+4r} unit and wherein the {X.sub.8W.sub.48+rO.sub.184+4r} unit has a central cavity, preferably [0394] with the proviso that, if r is 0, the {X.sub.8W.sub.48O.sub.184} unit is a cyclic fragment consisting of 4 X.sub.2W.sub.12-based units, wherein each X.sub.2W.sub.12-based unit is bonded to two adjacent X.sub.2W.sub.12-based units via 4 O atoms, wherein each of said 4 O atoms is bonded to a different W atom of each X.sub.2W.sub.12-based unit and wherein every two X.sub.2W.sub.12-based units are linked to each other by 2 of said 4 O atoms, wherein in the {X.sub.8W.sub.48O.sub.184} unit each X is linked to 6 different W via a 1 O atom bridge, respectively, and wherein each X is bonded to 4 O and each W is bonded to 6 O, in particular wherein the {X.sub.8W.sub.48O.sub.184} unit is represented by the following formula 1 [0395] wherein each O is presented in small Black dots, each W is presented in dark Gray spheres and each X is presented in light Gray sphere, [0396] with the proviso that, if r is 1, the {X.sub.8W.sub.48+1O.sub.184+4} unit comprises the {X.sub.8W.sub.48O.sub.184} unit and the one extra tungsten atom occupies one of the vacant sites in the cavity of the {X.sub.8W.sub.48O.sub.184} unit, or [0397] with the proviso that, if r is 2, the {X.sub.8W.sub.48+2O.sub.184+8} unit comprises the {X.sub.8W.sub.48O.sub.184} unit and the two extra tungsten atoms occupy two of the vacant sites in the cavity of the {X.sub.8W.sub.48O.sub.184} unit.
[0398] Embodiment 3: Polyoxometalate according to embodiment 1 or 2, wherein all X are the same; preferably wherein all X are P or As, more preferably wherein all X are P.
[0399] Embodiment 4: Polyoxometalate according to any one of the preceding embodiments, wherein each M is independently selected from the group consisting of Pd, Pt, Rh and Ir; preferably wherein all M are the same and all M are Pd or Pt or Rh or Ir, or wherein all M are selected from mixtures of Pd and Pt.
[0400] Embodiment 5: Polyoxometalate according to any one of the preceding embodiments, wherein t is 1, and R′ is selected from the group of arenes, more preferably benzene (Bz), p-cymene, cyclopentadiene (Cp), or pentamethylcyclopentadiene (Cp*), in particular cyclopentadiene (Cp) or pentamethylcyclopentadiene (Cp*), such as pentamethylcyclopentadiene (Cp*), most preferably each R′ is bonded to one or more M in the form of an organometallic bond, preferably in the form of at least one M-arene organometallic bond, more preferably in the form of at least one M-benzene (M-Bz), M-p-cymene, M-cyclopentadiene (M-Cp), or M-pentamethylcyclopentadiene (M-Cp*) organometallic bond, in particular in the form of M-cyclopentadiene (M-Cp) or M-pentamethylcyclopentadiene (M-Cp*) organometallic bond, such as in the form of M-pentamethylcyclopentadiene (M-Cp*) organometallic bond.
[0401] Embodiment 6: Polyoxometalate according to any one of the preceding embodiments, wherein each R is independently selected from the group consisting of F, Cl, Br, I, CN, N.sub.3, CP, FHF, SH, SCN, NCS, SeCN, CNO, NCO and OCN, preferably F, Cl, Br, I, CN, and N.sub.3, more preferably Cl, Br, I and N.sub.3, most preferably Cl, Br and I, in particular Cl.
[0402] Embodiment 7: Polyoxometalate according to any one of the preceding embodiments, wherein s is 2, 4, 6, 8, 10 or 12 and r is 0, 1 or 2; preferably wherein s is 2, 4, 6, 8, 10 or 12 and r is 0 or 1; more preferably wherein s is 2, 4, 6, 8, or 12 and r is 0 or 1; most preferably wherein s is 2, 4 or 6 and r is 0 or 1.
[0403] Embodiment 8: Polyoxometalate according to any one of the preceding embodiments, wherein q is 0 to 18, preferably wherein q is 0 to 12; more preferably wherein q is 0 to 10; most preferably wherein q is 0 to 8, in particular wherein q is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or 24, more particularly wherein q is 0, 1, 2, 3, 4, 5, 6, 7, 8 or 12; even more particularly wherein q is 0, 2, 4, 5, 6, 7 or 8.
[0404] Embodiment 9: Polyoxometalate according to any one of the preceding embodiments, wherein y is 0, 2, 4, 6, 8, 10, 12 or 24, preferably wherein y is 0, 2, 4, 6, 8 or 12; more preferably wherein y is 0, 2, 4, 6 or 8; most preferably wherein y is 0, 2, 4 or 8, in particular y is 0.
[0405] Embodiment 10: Polyoxometalate according to any one of the preceding embodiments, wherein z is 0.
[0406] Embodiment 11: Polyoxometalate according to any one of the preceding embodiments, wherein all M are Ir, Rh, Pd or Pt or wherein M is a mixture of Pd and Pt, and X is P, preferably wherein s is 2, 4 or 6, r is 0 or 1, and z is 0, more preferably wherein s is 2, 4 or 6, r is 0 or 1, and z is 0; in particular all M are Ir, Rh, Pd or Pt and X is P; more particularly wherein s is 4 or 6, r is 0 or 1, and z is 0.
[0407] Embodiment 12: Polyoxometalate according to any one of the preceding embodiments, wherein, each A is independently selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Hf, Re, Os, Ir, Pt, Au, Hg, lanthanide metal, actinide metal, Al, Ga, In, Tl, Sn, Pb, Sb, Bi, phosphonium, ammonium, guanidinium, tetraalkylammonium, protonated aliphatic amines, protonated aromatic amines or combinations thereof; preferably from the group consisting of Li, K, Na and combinations thereof.
[0408] Embodiment 13: Polyoxometalate according to any one of the preceding embodiments, represented by the formula
(A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m−.wH.sub.2O
wherein w represents the number of attracted water molecules per polyanion [(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)], and ranges from 1 to 180, preferably from 20 to 160, more preferably from 50 to 150, most preferably from 80 to 140.
[0409] Embodiment 14: Polyoxometalate according to any one of the preceding embodiments, wherein the polyoxometalate is in the form of a solution-stable polyanion.
[0410] Embodiment 15: Process for the preparation of the polyoxometalate of any one of embodiments 1 to 14, said process comprising: [0411] (a) reacting at least one source of M and at least one source of {X.sub.8W.sub.48+rO.sub.184+4r} and optionally at least one source of R and/or R′ to form a salt of the polyanion [(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)] or a solvate thereof, [0412] (b) optionally adding at least one salt of A to the reaction mixture of step (a) to form a polyoxometalate (A.sub.n).sup.m+[(MR′.sub.t).sub.sO.sub.yH.sub.qR.sub.z(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m− or a solvate thereof, and [0413] (c) recovering the polyoxometalate or solvate thereof.
[0414] Embodiment 16: Process according to embodiment 15, wherein the at least one source of {X.sub.8W.sub.48+rO.sub.184+4r} is an X.sub.2W.sub.12-based species, an X.sub.4W.sub.24-based species, an X.sub.8W.sub.48-based species, or a combination thereof, wherein the X.sub.2W.sub.12-based species and/or the X.sub.4W.sub.24-based species form an X.sub.8W.sub.48-based species in situ.
[0415] Embodiment 17: Process according to embodiment 15 or 16, wherein in step (a) the concentration of the metal ions originating from the source of M ranges from 0.001 to 1 mole/1, the concentration of the X.sub.8W.sub.48-based species originating from the sources of {X.sub.8W.sub.48+rO.sub.184+4r} ranges from 0.0001 to 0.1 mole/l, optionally the concentration of the R-containing starting material ranges from 0.001 to 1 mole/l and optionally the concentration of the R′-containing starting material ranges from 0.001 to 5 mole/l.
[0416] Embodiment 18: Process according to any one of embodiments 15 to 17, wherein in step (a) at least one source of M is used and wherein all M are the same such as all M are Pd or Pt or Ir or Rh or wherein M is a mixture of Pd and Pt.
[0417] Embodiment 19: Process according to any one of embodiments 15 to 18, wherein water, an organic solvent or a combination thereof is used as solvent, preferably water or a combination of water with an organic solvent is used as solvent, in particular water is used as solvent.
[0418] Embodiment 20: Process according to embodiment 19, wherein the solvent contains water and the at least one source of M is a water-soluble salt of Pt.sup.II or Pd.sup.II or Rh.sup.III or Ir.sup.III or Au.sup.III or Ag.sup.III, preferably wherein M is Pt, platinum chloride (PtCl.sub.2) or potassium tetrachloroplatinate (K.sub.2PtCl.sub.4); wherein M is Pd, palladium nitrate (Pd(NO.sub.3).sub.2), palladium sulphate (PdSO.sub.4), palladium chloride (PdCl.sub.2) or palladium acetate (Pd(CH.sub.3COO).sub.2); wherein M is Rh, rhodium chloride (RhCl.sub.3), rhodocene ([Rh(Cp).sub.2]), pentamethylcyclopentadienyl rhodium chloride ([Rh(Cp*)Cl.sub.2].sub.2), benzene rhodium chloride ([Rh(Bz)Cl.sub.2].sub.2), p-cymene rhodium chloride ([Rh(p-cymene)Cl.sub.2].sub.2), rhodium(II) acetate (C.sub.8H.sub.12O.sub.8Rh.sub.2); wherein M is Ir, iridium chloride (IrCl.sub.3), pentamethylcyclopentadienyl iridium chloride ([Ir(Cp*)Cl.sub.2].sub.2), benzene iridium chloride ([Ir(Bz)Cl.sub.2].sub.2), or p-cymene iridium chloride ([Ir(p-cymene)Cl.sub.2].sub.2); wherein M is Au, gold chloride (AuCl.sub.3), gold hydroxide (Au(OH).sub.3) or chloroauric acid (HAuCl.sub.4); wherein M is Ag, Ag.sup.III salts preferably generated with oxidizing agents from Ag.sup.I salts such as silver nitrate (AgNO.sub.3), silver fluoride (AgF) or silver chloride (AgCl); the at least one source of {X.sub.8W.sub.48+rO.sub.184+4r} is a water-soluble [X.sub.4W.sub.24O.sub.94].sup.24− or [X.sub.8W.sub.48O.sub.184].sup.40− salt, preferably a [X.sub.4W.sub.24O.sub.94].sup.24− or [X.sub.8W.sub.48O.sub.184].sup.40− salt of lithium, sodium, potassium, hydrogen or a combination thereof, more preferably a [X.sub.4W.sub.24O.sub.94].sup.24− or [X.sub.8W.sub.48O.sub.184].sup.40− salt of lithium, potassium, hydrogen or a combination thereof, in particular a [X.sub.4W.sub.24O.sub.94].sup.24− or [X.sub.8W.sub.48O.sub.184].sup.40− salt of a combination of lithium, potassium and hydrogen.
[0419] Embodiment 21: Process according to any one of embodiments 15 to 20, wherein step (a) is carried out in an aqueous solution, and the pH of the aqueous solution ranges from 1 to 10, preferably from 2 to 8, and more preferably from 3 to 7.
[0420] Embodiment 22: Process according to embodiment 21, wherein in step (a) the at least one source of M and the at least one source of {X.sub.8W.sub.48+rO.sub.184+4r} are dissolved in a solution of a buffer, preferably a 0.1 to 5.0 M solution of a buffer, in particular a 0.25 to 2.5 M solution of a buffer, and most preferred a 1.0 M solution of a buffer; wherein preferably the buffer is a acetate buffer and most preferably said acetate buffer is derived from lithium acetate or sodium acetate.
[0421] Embodiment 23: Process according to any one of embodiments 15 to 22, wherein in step (a) the reaction mixture is heated to a temperature of from 20° C. to 100° C., preferably from 50° C. to 90° C., more preferably from 60° C. to 80° C.
[0422] Embodiment 24: Supported polyoxometalate comprising polyoxometalate according to any one of embodiments 1 to 14 or prepared according to any one of embodiments 15 to 23, on a solid support.
[0423] Embodiment 25: Supported polyoxometalate according to embodiment 24, wherein the solid support is selected from polymers, graphite, carbon nanotubes, electrode surfaces, aluminum oxide and aerogels of aluminum oxide and magnesium oxide, titanium oxide, zirconium oxide, cerium oxide, silicon dioxide, silicates, active carbon, mesoporous silica, zeolites, aluminophosphates (ALPOs), silicoaluminophosphates (SAPOs), metal organic frameworks (MOFs), zeolitic imidazolate frameworks (ZIFs), periodic mesoporous organosilicas (PMOs), and mixtures thereof.
[0424] Embodiment 26: Process for the preparation of supported polyoxometalate according to embodiment 24 or 25, comprising the step of contacting polyoxometalate according to any one of embodiments 1 to 14 or prepared according to any one of embodiments 15 to 23, with a solid support.
[0425] Embodiment 27: Metal cluster unit of the formula
(A′.sub.n′).sup.m′+[M.sup.0.sub.s(X.sub.8W.sub.48+rO.sub.184+4r)].sup.m′−,
wherein [0426] each A′ independently represents a cation, [0427] n′ is the number of cations, [0428] each M.sup.0 is independently selected from the group consisting of Pd.sup.0, Pt.sup.0, Rh.sup.0, Ir.sup.0, Ag.sup.0, and Au.sup.0, [0429] each X is independently selected from the group consisting of P, As, Se and Te, [0430] s is a number from 2 to 12, [0431] r is 0, 1 or 2, and [0432] m′ is a number representing the total positive charge m′+ of n′ cations A′ and the corresponding negative charge m′− of the metal cluster unit anion [M.sup.0.sub.s(X.sub.8W.sub.48+rO.sub.184+4r)].
[0433] Embodiment 28: Metal cluster unit according to embodiment 27, wherein r is 0 and X.sub.8W.sub.48O.sub.184 forms a {X.sub.8W.sub.48O.sub.184}′ unit, preferably the {X.sub.8W.sub.48O.sub.184}′ unit has a central cavity, more preferably the {X.sub.8W.sub.48O.sub.184}′ unit is a cyclic fragment consisting of 4 X.sub.2W.sub.12-based units, wherein each X.sub.2W.sub.12-based unit is bonded to two adjacent X.sub.2W.sub.12-based units via 4 O atoms, wherein each of said 4 O atoms is bonded to a different W atom of each X.sub.2W.sub.12-based unit and wherein every two X.sub.2W.sub.12-based units are linked to each other by 2 of said 4 O atoms, wherein in the {X.sub.8W.sub.48O.sub.184}′ unit each X is linked to 6 different W via a 1 O atom bridge, respectively, and wherein each X is bonded to 4 O and each W is bonded to 6 O, in particular wherein the {X.sub.8W.sub.48O.sub.184}′ unit is represented by the following formula 1
wherein each O is presented in small Black dots, each W is presented in dark Gray spheres and each X is presented in light Gray sphere.
[0434] Embodiment 29: Metal cluster unit according to embodiment 27 or 28, wherein all X are the same; preferably wherein all X are P or As, more preferably wherein all X are P.
[0435] Embodiment 30: Metal cluster unit according to any one of the embodiments 27 to 29, wherein each M.sup.0 is independently selected from the group consisting of Pd.sup.0, Pt.sup.0, Rh.sup.0 and Ir.sup.0; in particular wherein all M.sup.0 are the same and all M.sup.0 are Pd.sup.0 or Pt.sup.0 or Rh.sup.0 or Ir.sup.0, or wherein all M are selected from mixtures of Pd.sup.0 and Pt.sup.0.
[0436] Embodiment 31: Metal cluster unit according to any one of the embodiments 27 to 30, wherein s is 2, 4, 6, 8, 10 or 12 and r is 0, 1 or 2; preferably wherein s is 2, 4, 6, 8, 10 or 12 and r is 0 or 1; more preferably wherein s is 2, 4, 6, 8 or 12 and r is 0 or 1; most preferably wherein s is 2, 4 or 6 and r is 0 or 1.
[0437] Embodiment 32: Metal cluster unit according to any one of the embodiments 27 to 31, wherein m′ is 40 when r is 0, m′ is 42 when r is 1, and m′ is 44 when r is 2.
[0438] Embodiment 33: Metal cluster unit according to any one of the embodiments 27 to 32, wherein, each A′ is independently selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Hf, Re, Os, Ir, Pt, Au, Hg, lanthanide metal, actinide metal, Al, Ga, In, Tl, Sn, Pb, Sb, Bi, phosphonium, ammonium, guanidinium, tetraalkylammonium, protonated aliphatic amines, protonated aromatic amines or combinations thereof; preferably from the group consisting of Li, K, Na, and combinations thereof.
[0439] Embodiment 34: Metal cluster unit according to any one of the embodiments 27 to 33, wherein the metal cluster unit is in the form of particles, preferably wherein at least 90 wt % of the metal cluster unit particles are in the form of primary particles.
[0440] Embodiment 35: Metal cluster unit according to any one of the embodiments 27 to 34, wherein the metal cluster unit is dispersed in a liquid carrier medium thereby forming a dispersion of metal cluster unit in said liquid carrier medium; and wherein preferably a dispersing agent is present to prevent agglomeration of the primary particles of metal cluster unit, and in particular the dispersing agent forms micelles containing one primary particle of metal cluster unit per micelle.
[0441] Embodiment 36: Metal cluster unit according to any one of the embodiments 27 to 34, wherein the metal cluster unit is immobilized on a solid support thereby forming supported metal cluster unit.
[0442] Embodiment 37: Supported metal cluster unit according to embodiment 36, wherein the solid support is selected from polymers, graphite, carbon nanotubes, electrode surfaces, aluminum oxide and aerogels of aluminum oxide and magnesium oxide, titanium oxide, zirconium oxide, cerium oxide, silicon dioxide, silicates, active carbon, mesoporous silica, zeolites, aluminophosphates (ALPOs), silicoaluminophosphates (SAPOs), metal organic frameworks (MOFs), zeolitic imidazolate frameworks (ZIFs), periodic mesoporous organosilicas (PMOs), and mixtures thereof.
[0443] Embodiment 38: Process for the preparation of the dispersion of metal cluster unit of embodiment 35, said process comprising the steps of [0444] (a) dissolving the polyoxometalate of any one of embodiments 1 to 14 or prepared according to any one of embodiments 15 to 23, in a liquid carrier medium, [0445] (b) optionally providing additive means to prevent agglomeration of the metal cluster unit to be prepared, and [0446] (c) subjecting the dissolved polyoxometalate to chemical or electrochemical reducing conditions sufficient to at least partially reduce said polyoxometalate into corresponding metal cluster unit.
[0447] Embodiment 39: Process for the preparation of the supported metal cluster units of embodiment 36 or 37, comprising the steps of [0448] (a) contacting the dispersion of metal cluster unit of embodiment 35 or prepared according to embodiment 38 with a solid support, thereby immobilizing at least part of the dispersed metal cluster unit onto the support; and [0449] (b) optionally isolating the supported metal cluster unit.
[0450] Embodiment 40: Process for the preparation of the supported metal cluster units of embodiment 36 or 37, comprising the steps of [0451] (a) subjecting the supported polyoxometalate of embodiment 24 or 25 or prepared according to embodiment 26 to chemical or electrochemical reducing conditions sufficient to at least partially reduce said polyoxometalate into corresponding metal cluster unit; and [0452] (b) optionally isolating the supported metal cluster unit.
[0453] Embodiment 41: Process according to any one of embodiments 38 or 40, wherein the chemical reducing conditions comprise the use of a reducing agent selected from organic and inorganic materials which are oxidizable by Pd.sup.II, Pt.sup.II, Rh.sup.I and Rh.sup.III, Ir.sup.I and Ir.sup.III, Ag.sup.I and Ag.sup.III, and Au.sup.I and Au.sup.III.
[0454] Embodiment 42: Process for the homogeneous or heterogeneous conversion of organic substrate comprising contacting said organic substrate with the polyoxometalate of any one of embodiments 1 to 14 or prepared according to any one of embodiments 15 to 23, and/or with the supported polyoxometalate of embodiment 24 or 25 or prepared according to embodiment 26, and/or with the metal cluster unit of any one of embodiments 27 to 34, and/or with the dispersion of metal cluster unit of embodiment 35 or prepared according to embodiment 38 or 41, and/or with the supported metal cluster unit of embodiment 36 or 37 or prepared according to any one of embodiments 39 to 41.
[0455] Embodiment 43: Process according to embodiment 42, comprising: [0456] (a) contacting a first organic substrate with one or more optionally supported polyoxometalates and/or one or more supported metal cluster units, [0457] (b) recovering the one or more optionally supported polyoxometalates and/or the one or more supported metal cluster units; [0458] (c) contacting the one or more optionally supported polyoxometalates and/or the one or more supported metal cluster units with a solvent at a temperature of 50° C. or more, and/or hydrogen stripping the one or more optionally supported polyoxometalates and/or the one or more supported metal cluster units at elevated temperature, and/or calcining the one or more optionally supported polyoxometalates and/or the one or more supported metal cluster units at elevated temperature under an oxygen containing gas, e.g. air, or under an inert gas, e.g. nitrogen or argon, to obtain recycled one or more optionally supported polyoxometalates and/or one or more supported metal cluster units; [0459] (d) contacting the recycled one or more optionally supported polyoxometalates and/or the one or more supported metal cluster units with a second organic substrate which may be the same as or different from the first organic substrate; and [0460] (e) optionally repeating steps (b) to (d).