HETEROCYCLIC SELENOPHOSPHITES AND METHOD FOR THE PREPARATION THEREOF

Abstract

Novel heterocyclic selenophosphites, method for preparation thereof and use thereof as ligand unit for preparing ligands for use in complexes.

Claims

1. Compound of a heterocyclic selenophosphite having a general structure (I) ##STR00016## where R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8 and R.sup.9 are each independently selected from: H, (C.sub.1-C.sub.12)-alkyl, O(C.sub.1-C.sub.12)-alkyl, (C.sub.6-C.sub.20)-aryl, O(C.sub.6-C.sub.20)-aryl, -halogen, COO(C.sub.1-C.sub.12)-alkyl, CONH(C.sub.1-C.sub.12)-alkyl, CO(C.sub.1-C.sub.12)-alkyl, CO(C.sub.6-C.sub.20)-aryl, COOH, SO.sub.3H, CN, N[(C.sub.1-C.sub.12)-alkyl].sub.2, wherein the alkyl and aryl groups are each independently unsubstituted or substituted, wherein the respective substituted (C.sub.1-C.sub.12)-alkyl group and substituted (C.sub.6-C.sub.20)-aryl group has at least one substituent and the at least one substituent is each independently selected from (C.sub.3-C.sub.12)-cycloalkyl, (C.sub.3-C.sub.12)-heterocycloalkyl, (C.sub.6-C.sub.20)-aryl, fluorine, chlorine, cyano, formyl, acyl or alkoxycarbonyl, and where R.sup.1 is independently selected from OH and -Hal, and -Hal is selected from fluorine, chlorine, bromine, iodine, and wherein optionally the compound of structure (I) is present in a mixture with a rearrangement product of structure (I).

2. Compound according to claim 1, characterized in that the heterocyclic selenophosphite of the general structure (I) is present as a compound of structure (Ia) in a mixture with a compound of structure (Ia*), ##STR00017## where R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8 and R.sup.9 in structures (Ia) and (Ia*) are each independently selected from: H, (C.sub.1-C.sub.12)-alkyl, O(C.sub.1-C.sub.12)-alkyl, (C.sub.6-C.sub.20)-aryl, O(C.sub.6-C.sub.20)-aryl, -halogen, COO(C.sub.1-C.sub.12)-alkyl, CONH(C.sub.1-C.sub.2)-alkyl, CO(C.sub.1-C.sub.2)-alkyl, CO(C.sub.6-C.sub.20)-aryl: COOH, SO.sub.3H, CN, N[(C.sub.1-C.sub.12)-alkyl].sub.2, wherein the alkyl and aryl groups are each independently unsubstituted or substituted, wherein the respective substituted (C.sub.1-C.sub.12)-alkyl group and substituted (C.sub.6-C.sub.20)-aryl group has at least one substituent and the at least one substituent is each independently selected from (C.sub.3-C.sub.12)-cycloalkyl, (C.sub.3-C.sub.12)-heterocycloalkyl, (C.sub.6-C.sub.20)-aryl, fluorine, chlorine, cyano, formyl, acyl or alkoxycarbonyl.

3. Compound according to claim 1, characterized in that the heterocyclic selenophosphite of the general structure (I) is present as a compound of structure (Ib), ##STR00018## where R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8 and R.sup.9 in structure (Ib) are each independently selected from: H, (C.sub.1-C.sub.12)-alkyl, O(C.sub.1-C.sub.12)-alkyl, (C.sub.6-C.sub.20)-aryl, O(C.sub.1-C.sub.12)-aryl, -halogen, COO(C.sub.1-C.sub.12)-alkyl, CONH(C.sub.1-C.sub.12)-alkyl, CO(C.sub.1-C.sub.12)-alkyl, CO(C.sub.6-C.sub.20)-aryl, COOH, SO.sub.3H, CN, N[(C.sub.1-C.sub.12)-alkyl].sub.2, wherein the alkyl and aryl groups are each independently unsubstituted or substituted, wherein the respective substituted (C.sub.1-C.sub.12)-alkyl group and substituted (C.sub.6-C.sub.20)-aryl group has at least one substituent and the at least one substituent is each independently selected from (C.sub.3-C.sub.12)-cycloalkyl, (C.sub.3-C.sub.12)-heterocycloalkyl, (C.sub.6-C.sub.20)-aryl, fluorine, chlorine, cyano, formyl, acyl or alkoxycarbonyl, and wherein -Hal is selected from fluorine, chlorine, bromine, iodine.

4. Compound according to claim 1, characterized in that the heterocyclic selenophosphite of the general structure (I) is selected from at least one compound of structure (Ic), (Ic*), wherein optionally the compounds of structures (Ic) and (Ic*) are present as a mixture ##STR00019## where R.sup.2, R.sup.4, R.sup.7, and R.sup.9 in structures (Ic) and (Ic*) are each independently selected from: (C.sub.1-C.sub.12)-alkyl, O(C.sub.1-C.sub.12)-alkyl, (C.sub.6-C.sub.2)aryl, O(C.sub.6-C.sub.20)-aryl, -halogen, COO(C.sub.1-C.sub.12)-alkyl, CONH(C.sub.1-C.sub.12)-alkyl, CO(C.sub.1-C.sub.12)-alkyl, CO(C.sub.6-C.sub.20)-aryl, COOH, SO.sub.3H, CN, N[(C.sub.1-C.sub.12)-alkyl].sub.2, wherein the alkyl and aryl groups are each independently unsubstituted or substituted, wherein the respective substituted (C.sub.1-C.sub.12)-alkyl group and substituted (C.sub.6-C.sub.20)-aryl group has at least one substituent and the at least one substituent is each independently selected from (C.sub.3-C.sub.12)-cycloalkyl, (C.sub.3-C.sub.12)-heterocycloalkyl, (C.sub.6-C.sub.20)-aryl, fluorine, chlorine, cyano, formyl, acyl or alkoxycarbonyl.

5. Compound according to claim 1, characterized in that the heterocyclic selenophosphite of the general structure (I) is selected from at least one compound of structure (Id), ##STR00020## where R.sup.2, R.sup.4, R.sup.7 and R.sup.9 in structure (Id) are each independently selected from: (C.sub.1-C.sub.12)-alkyl, O(C.sub.1-C.sub.12)-alkyl, (C.sub.6-C.sub.2)-aryl, O(C.sub.6-C.sub.20)-aryl, -halogen, COO(C.sub.1-C.sub.12)-alkyl, CONH(C.sub.1-C.sub.12)-alkyl, CO(C.sub.1-C.sub.12)-alkyl, CO(C.sub.6-C.sub.20)-aryl, COOH, SO.sub.3H, CN, N[(C.sub.1-C.sub.12)-alkyl].sub.2, wherein the alkyl and aryl groups are each independently unsubstituted or substituted, wherein the respective substituted (C.sub.1-C.sub.12)-alkyl group and substituted (C.sub.6-C.sub.20)-aryl group has at least one substituent and the at least one substituent is each independently selected from (C.sub.3-C.sub.12)-cycloalkyl, (C.sub.3-C.sub.12)-heterocycloalkyl, (C.sub.6-C.sub.20)-aryl, fluorine, chlorine, cyano, formyl, acyl or alkoxycarbonyl, where -Hal is selected from fluorine, chlorine, bromine, iodine.

6. Method for preparing at least one heterocyclic selenophosphite of the general structure (I) ##STR00021## where R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8 and R.sup.9 are each independently selected from: H, (C.sub.1-C.sub.12)-alkyl, O(C.sub.1-C.sub.12)-alkyl, (C.sub.6-C.sub.20)-aryl, O(C.sub.6-C.sub.20)-aryl, -halogen, COO(C.sub.1-C.sub.12)-alkyl, CONH(C.sub.1-C.sub.12)-alkyl, CO(C.sub.1-C.sub.12)-alkyl, CO(C.sub.6-C.sub.20)-aryl, COOH, SO.sub.3H, CN, N[(C.sub.1-C.sub.12)-alkyl].sub.2, wherein the alkyl and aryl groups are each independently unsubstituted or substituted, wherein the respective substituted (C.sub.1-C.sub.12)-alkyl group and substituted (C.sub.3-C.sub.20)-aryl group has at least one substituent and the at least one substituent is each independently selected from (C.sub.3-C.sub.12)-cycloalkyl, (C.sub.3-C.sub.12)-heterocycloalkyl, (C.sub.6-C.sub.20)-aryl, fluorine, chlorine, cyano, formyl, acyl or alkoxycarbonyl, and where R.sup.1 is independently selected from OH and -Hal, where -Hal is selected from fluorine, chlorine, bromine, iodine, optionally in a mixture with a rearrangement product of the compound of the structure (I), comprising at least the method step of (i) reacting a selenodiaryl of the general structure (II) ##STR00022## where R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8 and R.sup.7 in structure (II) are each independently selected from: H, (C.sub.1-C.sub.12)-alkyl, O(C.sub.1-C.sub.12)-alkyl, (C.sub.6-C.sub.20)-aryl, O(C.sub.6-C.sub.20)-aryl, -halogen, COO(C.sub.1-C.sub.12)-alkyl, CONH(C.sub.1-C.sub.12)-alkyl, CO(C.sub.1-C.sub.12)-alkyl, CO(C.sub.6-C.sub.20)-aryl, COOH, SO.sub.3H, CN, N[(C.sub.1-C.sub.12)-alkyl].sub.2, wherein the alkyl and aryl groups are each independently unsubstituted or substituted, wherein the respective substituted (C.sub.1-C.sub.12)-alkyl group and substituted (C.sub.6-C.sub.20)-aryl group has at least one substituent and the at least one substituent is each independently selected from (C.sub.3-C.sub.12)-cycloalkyl, (C.sub.3-C.sub.12)-heterocycloalkyl, (C.sub.6-C.sub.20)-aryl, fluorine, chlorine, cyano, formyl, acyl or alkoxycarbonyl, (ii) with P(Hal).sub.3 of formula (III), where -Hal is selected from fluorine, chlorine, bromine, iodine, (iii) and obtaining at least one heterocyclic selenophosphite of the general structure (I), optionally in a mixture with a rearrangement product of the compound of the structure (I).

7. Method according to claim 6, characterized in that the heterocyclic selenophosphite of the general structure (I) is obtained as a compound of structure (Ia) in a mixture with a compound of structure (Ia*), ##STR00023## where R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8 and R.sup.9 in structure (la) and (Ia*) are each independently selected from: H, (C.sub.1-C.sub.12)-alkyl, O(C.sub.1-C.sub.12)-alkyl, (C.sub.6-C.sub.20)-aryl, O(C.sub.6-C.sub.20)-aryl, -halogen, COO(C.sub.1-C.sub.12)-alkyl, CONH(C.sub.1-C.sub.12)-alkyl, CO(C.sub.1-C.sub.12)-alkyl, CO(C.sub.6-C.sub.20)-aryl, COOH, SO.sub.3H, CN, N[(C.sub.1-C.sub.12)-alkyl].sub.2, wherein the alkyl and aryl groups are each independently unsubstituted or substituted, wherein the respective substituted (C.sub.1-C.sub.12)-alkyl group and substituted (C.sub.6-C.sub.20)-aryl group has at least one substituent and the at least one substituent is each independently selected from (C.sub.3-C.sub.12)-cycloalkyl, (C.sub.3-C.sub.12)-heterocycloalkyl, (C.sub.6-C.sub.20)-aryl, fluorine, chlorine, cyano, formyl, acyl or alkoxycarbonyl.

8. Method according to claim 6, wherein (i) the reaction is carried out in the presence of an amine, in particular an alkylamine such as triethylamine.

9. Method according to claim 6, characterized in that the selenodiaryl of the general structure (II) is reacted with P(Hal).sub.3 of formula (III) in a molar ratio of from 10:1 to 1:10, preferably in a ratio of from 1.2:1 to 1:1.2.

10. Method according to claim 6, characterized in that P(Hal).sub.3 of formula (III) is PCl.sub.3 or PBr.sub.3.

11. Method according to claim 6, wherein (i) the reaction is carried out from 15 to 30 C., particularly 5 to 5 C.

12. Method according to claim 6, wherein (i) the reaction is carried out in an aprotic solvent, the solvent in particular being selected from a) organic aromatic halogenated solvents or hydrocarbons, or b) ethers, THF, esters or ketones.

13. Use of a heterocyclic selenophosphite according to claim 1 for preparing ligands, particularly as ligand unit for preparing phosphite ligands.

14. Use according to claim 13 wherein preparing ligands comprises preparing a ligand unit for preparing phosphite ligands.

15. Use of a heterocyclic selenophosphite produced according to claim 6 for preparing ligands.

16. Use according to claim 15 wherein preparing ligands comprises preparing a ligand unit for preparing phosphite ligands.

Description

GENERAL METHODS

[0055] Solvents and Reagents

[0056] All reactions with moisture- and/or oxygen-sensitive substances were carried out in baked-out apparatuses under an argon atmosphere. Solvents for extraction and column chromatography were used at the following purities: dichloromethane (99.9%, Walter, Cat. No. BIE 073107033) ethyl acetate (99.5%, Walter, Cat. No. BIE 003917025) and n-hexane (95%, Walter (Baker). Cat. No. 8669),

[0057] n-heptane (95%, Walter (Baker), Cat. No. 8662). Other solvents for extraction and column chromatography were of technical quality and were used without further purification unless otherwise stated. Dry solvents (abs.) were purified using a Pure Solv MD-7 System and stored under an argon atmosphere. Benzyl bromide was freshly distilled (17 mbar/82 C.) prior to use. Deuterated solvents were distilled from the drying agents specified: dichloromethane-d.sub.2 (phosphorus pentoxide), toluene-ds (1. KOH; 2, sodium). Chemicals used for the syntheses were supplied by Sigma Aldrich, Alfa Aesar. Acros Organics, Avantor Performance Materials B. V., Merck KGaA and ABCR GmbH & Co. KG. These were used without further purification unless otherwise stated.

[0058] Filtration: Filtrations for the removal of resulting solids were carried out using a G4 frit (pore width: 10-16 m).

[0059] Analysis

[0060] IR spectroscopy: IR spectra were recorded with a Nicolet 6700 FT-IR spectrometer from Thermo Electron. The substances were measured by ATR methods.

[0061] .sup.1H-NMR spectroscopy. .sup.1H-NMR spectra were recorded with a model AV300 (300 MHz) and with the model Fourier 300 (300 MHz) from Bruker. Chemical shifts are stated in units on the 6-scale. The residual proton signals of the solvent (dichloromethane-d.sub.2: =5.32 ppm, toluene-ds: =7.09; 7.00; 6.98; 2.09 ppm) served as standard.

[0062] .sup.13-NMR spectroscopy: .sup.13C-NMR spectra were recorded with models AV 300 (75 MHz) and Fourier 300 (75 MHz) from Bruker. The signal of the solvent (dichloromethane-d.sub.2: =54.0 ppm, toluene-d.sub.6: =137.9; 129.2; 128.3; 125.5; 20.4 ppm) served as internal standard wherein the chemical shifts were taken from the broadband .sup.1H-decoupled spectra.

[0063] .sup.77Se-NMR spectroscopy: .sup.77Se-NMR spectra were recorded with an AV 300 (57 MHz) from Bruker. The spectra were measured in broadband .sup.1H-decoupled mode. The chemical shifts are reported in ppm.

[0064] Mass spectrometry: EI mass spectra were recorded on a Finnigan MAT 95-XP instrument from Thermo Electron and ESI-TOF mass spectra with a model 6210 Time-of-Flight LC/MS from Agilent.

[0065] X-Ray Crystal Structure Analysis of the Compound of Structure Id (2c)

[0066] Data were collected by a Bruker Kappa APEX II Duo diffractometer. The structure was solved by direct methods (SHELXS-97: G. M. Sheldrick, Acta Cryst, 2008, A64, 112-122.) and refined with full matrix by the method of least squares against F.sup.2 (SHELXL-2014: G. M. Sheldrick, Acta Cryst 2015, C71, 3-8.)

[0067] General Procedure

[0068] 8.2 mmol of the particular phenol are dissolved in the appropriate solvent (8.2 m). The reaction mixture is heated, and 4.9 mmol of selenium dioxide are added while stirring. The solvent is distilled under reduced pressure (temperature <70 C.). A frit is prepared with 2.5 cm of silica gel (at the bottom) and 2.5 cm of zeolite (at the top). The distillation residue is taken up in the eluent and applied to the filtration column. Cyclohexane:ethyl acetate (95:5) is used to wash the product off the frit and collect it in fractions. The fractions containing the product are combined and freed of the eluent by distillation. The fractions obtained are recrystallized from 95:5 cyclohexane:ethyl acetate. For this purpose, the solid residue is dissolved at 50 C., and insoluble residues are filtered off using a glass frit. The selenodiaryl (II) reaction product crystallizes out of the saturated solution at room temperature overnight. The resulting crystals are washed once again with cold cyclohexane.

[0069] The structural formula shows the main product of the general structure II obtained in each reaction.

[0070] Bis(3,5-dimethyl-2-hydroxyphenyl)selenium (II)

##STR00010##

[0071] The reaction is conducted according to the general procedure in a screw-top test tube. For this purpose, 1.00 g (8.2 mmol, 1.0 equiv.) of 2,4-dimethylphenol and 0.54 g (4.9 mmol, 0.6 equiv.) of selenium dioxide are dissolved in 1 mL of pyridine and heated. The product is obtained as a colourless crystalline solid.

[0072] .sup.1H-NMR (400 MHz, CDCl.sub.3): (ppm)=7.12 (s, 2H, 6-H), 6.91 (s, 2H, 4-H), 5.97 (s, 2H. OH), 2.23 (s, 6H, 3-CH.sub.3) 2.23 (s, 6H, 5-CH.sub.3); .sup.13C-NMR (100 MHz, CDCl.sub.3): (ppm)=151.7 (C-2), 133.2 (C-3), 133.1 (C-5), 130.4 (C-4), 124.2 (C6), 114.9 (C-1), 20.3 (5-CH.sub.3), 16.5 (3-CH.sub.3). .sup.77Se-NMR (76 MHz, CDCl.sub.3): (ppm)=163.36 ppm.

[0073] Bis(3-tert-butyl-5-methyl-2-hydroxyphenyl)selenium (II)

##STR00011##

[0074] The reaction is conducted according to the general procedure in a screw-top test tube. Here 1.32 g (8.0 mmol, 1.0 equiv.)

of 2-tert-butyl-4-methylphenol and 0.54 g (4.9 mmol, 0.6 equiv.) of selenium dioxide are dissolved in 1 mL of pyridine and heated.

[0075] .sup.1H-NMR (300 MHz, CDCl.sub.3): (ppm)=7.15 (s, 2H, 6-H), 7.05 (s, 2H, 4-H), 5.07 (s, 2H, OH), 2.21 (s, 6H, 5-CH.sub.3), 2.21 (s, 18H, 3-C(CH.sub.3).sub.3; .sup.13C-NMR (75 MHz, CDCl.sub.3):

[0076] (ppm)=152.1, 136.4, 133.4, 120.1, 129.5, 117.2, 35.1, 29.6, 20.8.

[0077] 3,35,5-Tetra-tert-butylbiphenyl-2,2-diol (II)

##STR00012##

[0078] The reaction is conducted according to the general procedure in a screw-top test tube. Here 1.67 g (8.2 mmol, 1.0 equiv.)

of 2,4-di-tert-butylphenol and 0.55 g (4.9 mmol, 0.6 equiv.) of selenium dioxide are dissolved in 1 mL of pyridine and heated.

[0079] .sup.1H-NMR (400 MHz, CDCl.sub.3): (ppm)=7.31 (d, J=2.4 Hz, 2H), 7.29 (d, J=2.4), 6.29 (s, 2H), 1.42 (s, 18H), 1.24 (s, 18H); .sup.13C-NMR (75 MHz, CDCl.sub.3): (ppm)=151.7, 143.5, 135.8, 129.8, 125.6, 117.2, 35.4, 34.4, 31.6, 29.7.

Preparation of a Seleno-Heterocyclic Monophosphite of Structure I

Synthesis of 2,4,8,10-Tetramethyldibenzo[d,g][1,3,6,2]dioxaselenophosphocin-6-ol Ic (2a) and 2,4,8,10-tetramethyldibenzo[d,g][1,3,6,2]dioxaselenophosphocin-6-oxide Ic* (2b) and 6-choloro-2,4,6,10-tetramethyldibenzo[d,g][1,3,6,2]dioxaselenophosphocin Id (2c)

[0080] ##STR00013##

[0081] In a baked-out, 50 mL Schlenk flask under an argon atmosphere, 87.5 L (137 mg, 1.00 mmol, 1.0 eq) of phosphorus trichloride and 322 mg (1.00 mmol, 1.0 eq) of selenodiphenol 1 were dissolved in 15 mL of abs, diethyl ether. The pale yellow solution was cooled to 0 C. and a solution of 277 L (202 mg, 2.00 mmol, 2.0 eq) of triethylamine in 2.5 mL of abs, diethyl ether was added dropwise, whereupon the formation of a colourless precipitate was observed. 4.0 mL of abs, diethyl ether were rinsed in and the mixture stirred for 10 minutes at 0 C. The reaction solution was subsequently heated to RT and stirred for a further 36 hours. The resulting precipitate was filtered off and the solid washed with 5.0 mL of abs, diethyl ether. The solvent was removed under reduced pressure and the crude product was dried under vacuum at 50 C. for three hours. 386 mg (0.999 mmol, 99%) of the title compounds 2a and 2b were obtained as a colourless solid in a ratio of 85:15 (determined by .sup.31P-NMR).

##STR00014##

[0082] If the reaction was carried out in abs, toluene in place of abs, diethyl ether (analogous experimental procedure), 6-chloro-2,4,8,10-tetramethyldibenzo[d,g][1,3,6,2]dioxaseleno phosphocin Id (2c) was obtained. The compound is crystalline and from the crystals of compound 2c obtained, a single crystal structure analysis could be performed.

[0083] Total reaction mixture: IR (ATR): {circumflex over ()} (cm.sup.1)=3205; 2916; 2853; 2730; 2465; 1460; 1423; 1376; 1272; 1191; 1115; 1037; 957; 934; 917; 887; 859; 812; 733; 671; 594; 579; 567; 526; 497; 475.

[0084] Total reaction mixture: .sup.77Se-NMR (57 MHz, toluene-d.sub.8): (ppm)=313.5 ppm (d, J.sub.Se-P=59.7 Hz); 319.3 ppm (d, J=4.38 Hz); 326.0 ppm (d, J.sub.Se-P=50.9 Hz).

[0085] Compounds 2a/2b: .sup.31P-NMR (122 MHz, toluene-d.sub.6): (ppm)=167.0 (J.sub.P-Se=59.5 Hz); 2.45.

[0086] Compounds 2a12b: .sup.1H-coupled .sup.31P-NMR (122 MHz, toluene-d.sub.8): (ppm)=167.0 (J.sub.P-Se=59.5 Hz); 2.41 (d, J.sub.P-H=745 Hz).

[0087] Total reaction mixture: .sup.31P-NMR (122 MHz, toluene-d): (ppm)=197.9 (d. J=12.4 Hz); 167.0; 136.5; 136.0 (d. J=12.4 Hz), 2.45.

[0088] Compounds 2a/2b: ESI-TOF/MS: m/z=369.016 ([M+H].sup.+); 390.998 ([M+Na].sup.+); 759.006 ([2M+Na]).

[0089] For compounds 2a/2b: HR-MS (ESI-TOF): calc. for C.sub.16H.sub.18O.sub.3PSe ([M+H].sup.+): 369.0154. found: 369.0157; calc. for C.sub.16H.sub.17O.sub.3PSeNa ([M+Na].sup.+): 390.99734. found: 390.99808.

[0090] For compounds 2a/2b: C.sub.16H.sub.17O.sub.3PSe (368.01 g/mol).

[0091] For compound 2c: C.sub.16H.sub.16ClO.sub.2PSe (385.97 g/mol).

[0092] Theoretical calculation of compounds 2a/2b:

##STR00015##

[0093] Crystal structure analysis of the compound of structure Id (2c):

[0094] Compound 2c: C.sub.16H.sub.16ClO.sub.2PSe, M=385.67, monoclinic, space group P2.sub.1/c, a=11.9587 (5), b=8.8151 (4), c=15.6401 (7) , =93.4819 (16), V=1645.69 (13) .sup.3, Z=4, .sub.cal.=1.557 g.Math.cm.sup.3, =2.542 mm.sup.1, T=150 (2) K, 26607 measured, 3977 independent reflections (R.sub.int=0.0215), R.sub.1=0.0245 (1>2 (1)), wR.sub.2=0.0691 (all data), 194 parameters. Measurable crystals of compound 2c could be obtained in a solvent mixture of n-heptane/acetonitrile (5:1) at a temperature of 6 C. (refrigerator).