NCN trianionic pincer complexes as catalysts for olefin polymerization and isomerization

Abstract

A catalyst comprising a NCN pincer ligand group VI complex is capable of being used as an olefin polymerization or isomerization catalyst that does not require an expensive cocatalyst. The complex has the NCN pincer ligand in a trianionic form with the group VI in the +3 oxidation state or the +4 oxidation state and complexed to an anionic hydrocarbon group, or the complex has the NCN pincer ligand in a dianionic form with the group VI in the +2 oxidation state. The complex is capable of initiating the polymerization of alkenes without an added activator. The presence of a water scavenger and activator or cocatalyst, such as triisobutylaluminum, increases the catalytic activity. The complex is capable of selectively isomerizing 1-alkenes to cis/trans 2-alkenes.

Claims

1. A catalyst, comprising a NCN pincer ligand group VI metal complex, wherein the NCN pincer ligand is in the dianionic form or trianionic form having the structures: ##STR00011## wherein the group VI metal is in the +2 oxidation state or +4 oxidation state where the NCN pincer ligand with N and C are nitrogen and carbon anion sites of the NCN pincer ligand and HN is a neutral site and metal ion form a pair of five-member rings or a pair of six-member rings in the complexes and where R is 2,6-bis-(i-propyl)phenyl, 3,5-bis-(methyl)phenyl, 3,5-bis-(trifluoromethyl) phenyl, 3,5-bis-(i-propyl)phenyl, mesytyl, or tri-i-propylsilyl and R is a normal alkyl group or a phenyl group, and wherein the NCN pincer ligand in the triprotonated form is: ##STR00012## where R is 2,6-bis-(i-propyl)phenyl, 3,5-bis-(methyl)phenyl, 3,5-bis-(trifluoromethyl) phenyl, 3,5-bis-(i-propyl)phenyl, mesytyl, or tri-i-propylsilyl and where L is tetrahydrofuran (THF).

2. The catalyst of claim 1, wherein the group VI metal is Cr, Mo or W.

3. The catalyst of claim 1, wherein the NCN pincer ligand complexed group VI metal alkyl is ##STR00013##

4. The catalyst of claim 1, wherein the NCN pincer ligand complexed group VI metal is ##STR00014##

5. The catalyst of claim 1, wherein the trianionic NCN pincer ligand group VI metal alkyl complex is soluble in an organic solvent.

6. A method for the preparation of a polyolefin, comprising: providing a NCN pincer ligand group VI metal complex according to claim 1; providing one or more olefin monomers; and contacting the complex with the monomers, wherein the complex initiates the polymerization of the olefin.

7. The method of claim 6, further comprising providing triisobutylaluminum (TIBA).

8. The method of claim 6, wherein the NCN pincer ligand group VI metal complex has the structure: ##STR00015##

9. The method of claim 6, wherein the NCN pincer ligand group VI metal complex has the structure: ##STR00016##

10. The method of claim 6, wherein the olefin is ethylene, propylene, or butadiene.

11. A method for isomerizing -olefins, comprising: providing a NCN pincer ligand group VI metal complex according to claim 1; providing one or more -olefins; and contacting the complex with the -olefins, wherein the complex catalyzes the isomerization of the -olefins to internal olefins.

12. The method of claim 11, wherein the NCN pincer ligand group VI metal complex has the structure: ##STR00017##

13. The method of claim 11, wherein the NCN pincer ligand group VI metal complex has the structure: ##STR00018##

14. The method of claim 11, wherein the NCN pincer ligand group VI metal Complex has the structure: ##STR00019##

15. The method of claim 11, wherein the -olefin is a 4 to 20 carbon having at least one vinyl group and at least one methylene unit adjacent to the vinyl group.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a reaction scheme for the preparation of 7 and 8 according to embodiments of the invention.

(2) FIG. 2 is a .sup.1H NMR spectrum of [2,6-.sup.iPrNCN]CrMe(THF) (7) in benzene-d.sub.6 according to an embodiment of the invention.

(3) FIG. 3 shows an IR spectrum of [2,6-.sup.iPrNCN]CrMe(THF) (7) according to an embodiment of the invention.

(4) FIG. 4 shows an UV-Vis spectrum of [2,6-.sup.iPrNCN]CrMe(THF) (7) in pentane according to an embodiment of the invention.

(5) FIG. 5 is the molecular structure of [2,6-.sup.iPrNCN]CrMe(THF) (7) according to an embodiment of the invention as determined by X-ray crystallography shown with ellipsoid presented at the 50% probability level and hydrogens removed for clarity.

(6) FIG. 6 is a .sup.1H NMR spectrum of [2,6-.sup.iPrNCN]Cr(THF).sub.2 (8) in benzene-d.sub.6 according to an embodiment of the invention.

(7) FIG. 7 shows an IR spectrum of [2,6-.sup.iPrNCN]Cr(THF).sub.2 (8) according to an embodiment of the invention.

(8) FIG. 8 shows an UV-Vis spectrum of [2,6-.sup.iPrNCN]Cr(THF).sub.2 (8) in pentane according to an embodiment of the invention.

(9) FIG. 9 is a .sup.1H NMR spectrum of [2,6-.sup.iPrNCN]Cr(THF).sub.3 (9) in benzene-d.sub.6 according to an embodiment of the invention.

(10) FIG. 10 shows an IR spectrum of [2,6-.sup.iPrNCN]Cr(THF).sub.3 (9) according to an embodiment of the invention.

(11) FIG. 11 shows an UV-Vis spectrum of [2,6-.sup.iPrNCN]Cr(THF).sub.3 (9) in benzene according to an embodiment of the invention.

(12) FIG. 12 is a composite of .sup.1H NMR spectra in d.sub.6-benzene of solutions of isomerizing 1-hexene solutions containing [2,6-.sup.iPrNCN]CrMe(THF) (7) at 2 (top), 4, 8, 12, and 24 (bottom) hours according to an embodiment of the invention.

(13) FIG. 13 is a .sup.13C NMR spectrum obtained in d.sub.6-benzene for the reaction products from 1-hexene in the presence of 7 after 24 hrs at 85 C., according to an embodiment of the invention.

DETAILED DISCLOSURE

(14) Embodiments of the invention are directed to trianionic NCN pincer ligated group IV or group VI metal hydrocarbon complexes or dianionic NCN pincer ligand derived group IV or group VI metal complexes of the generalized structures:

(15) ##STR00005##
where M(IV) is a group VI metal (Cr, Mo, or W) or a group IV metal (Ti, Zr, or Hf), R is an alkyl group or phenyl group, where the alkyl group can be methyl, ethyl, propyl, butyl, pentyl, or higher normal alkyl group and the NCN ligand and metal ion form a pair of five-member rings or a pair of six-member rings in the trianionic complexes or a single eight-member ring or ten-member ring in the dianionic complexes.

(16) The triprotonated NCN pincer ligands are:

(17) ##STR00006##
where R is 2,6-bis-(i-propyl)phenyl, 3,5-bis-(methyl)phenyl, 3,5-bis-(trifluoromethyl)phenyl, 3,5-bis-(i-propyl)phenyl, mesytyl, or tri-i-propylsilyl. All carbons positions not shown to have a H substituent can be independently substituted, for example, with alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl t-butyl, or larger alkyl groups or any other substituent in a manner that does not inhibit formation of the metal complex, as can be appreciated by those skilled in the art. In the complexes according to embodiments of the invention, the trianionic forms of the ligands are:

(18) ##STR00007##
where R is defined as above and all carbons positions not shown with a negative charge or a hydrogen substituent can be independently substituted, for example, with alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl t-butyl, or larger normal alkyl groups or any other substituent in a manner that does not inhibit formation of the metal complex. The dianionic form can be protonated on one of the nitrogen atoms or the central carbon atom.

(19) Using an NCN pincer ligand, a Cr(IV) trianionic pincer ligand complex, for example, the complex:

(20) ##STR00008##
having the trianionic NCN pincer ligand from 1 where R is 2,6-bis-(i-propyl)phenyl, can be prepared and isolated. In like manner to the Cr complex having two five-member rings from 1, complexes from 2, and 3 can be formed. Furthermore, in like manner, Cr complexes having six-membered rings can be formed starting with 4, 5, and 6. Depending upon the NCN pincer ligand and the substituents on the ligand, the complex can be soluble, for example, in an aliphatic or aromatic hydrocarbon, an ether, or another organic solvents.

(21) In another embodiment of the invention, a Cr(II) dianionic pincer ligand complex, for example the complex:

(22) ##STR00009##
having the dianionic NCN pincer ligand from 1 where R is 2,6-bis-(i-propyl)phenyl, can be prepared and isolated. Depending upon the NCN pincer ligand and the substituents on the ligand, the complex is soluble, for example, in an aliphatic or aromatic hydrocarbon, an ether, or another organic solvent.

(23) During studies on the preparation of Cr(II) dianionic pincer ligand complexes and Cr(IV) dianionic pincer ligand complex a new Cr(III) dianionic pincer ligand complex, according to an embodiment of the invention, incorporating the trianionic NCN pincer ligand from 1 where R is 2,6-bis-(i-propyl)phenyl, has been isolated. The Cr(III) complex is of the structure:

(24) ##STR00010##

(25) In another embodiment of the invention, the trianionic NCN pincer ligated metal alkyl complex and/or the dianionic NCN pincer ligand derived metal complex comprises a catalyst for the polymerization of alkenes. The catalysts do not require an expensive activator to initiate the polymerization. Instead, a compound, such as triisobutylaluminum (TIBA), is added, which removes spurious water and activates the system.

(26) In another embodiment of the invention, the trianionic NCN pincer ligated metal alkyl complex and/or the dianionic NCN pincer ligand derived metal complex comprises an isomerization catalyst for the transformation of an a-olefin to an internal olefin. The a-olefin is any olefin containing at least one vinyl group having an adjacent methylene unit, for example, a 4 to 20 carbon olefin with one or more vinyl groups. The olefin can be straight chained or branched. The complex isomerizes a 1-alkene to cis/trans 2-alkene with a relatively high selectivity. Little conversion of the 2-alkene occurs to form a 3-alkene or more internal alkene.

Methods and Materials

(27) General Considerations

(28) Unless specified otherwise, all manipulations were performed under an inert atmosphere using standard Schlenk or glovebox techniques. Pentane, hexanes, toluene, diethyl ether, and tetrahydrofuran were dried using a GlassContour drying column. C.sub.6D.sub.6 and toluene-d.sub.3 (Cambridge Isotopes) were dried over sodium-benzophenone ketyl, distilled or vacuum transferred and stored over 4 molecular sieves. Anhydrous CrCl.sub.2, 1-hexene, 1-octene, and styrene oxide were purchased from Sigma-Aldrich and used as received. CrMeCl.sub.2(THF).sub.3 and {[2,6.sup.iPrNCHN]Li.sub.2}.sub.2.sup.2 were prepared according to a literature procedure. Triisobutylaluminum (25 wt. % in toluene) was purchased from Sigma-Aldrich and used as received. Ethylene (Matheson Purity 99.995%) was purchased from Matheson and used as received. Gas chromatography was performed on a Varian CP-3800 gas chromatograph using an intermediate polarity column. NMR spectra were obtained on Varian Gemini 300 MHz, Varian VXR 300 MHz, Varian Mercury 300 MHz, Varian Mercury Broad Band 300 MHz, Varian INOVA 500 MHz, or Varian INOVA2 500 MHz spectrometers. Chemical shifts are reported in (ppm). For .sup.1H and .sup.13C NMR spectra, the residual solvent peak was referenced as an internal reference. Variable temperature NMR experiments were performed in toluene-d.sub.8. Infrared spectra were obtained on a Thermo scientific Nicolet 6700 FT-IR. Spectra of solids were measured as KBr discs. UV-visible spectra were recorded on a Cary 50 with scan software version 3.00(182). Gas chromatography was performed on a Varian CP-3800 gas chromatograph using an intermediate polarity column. EPR measurements were conducted using a Bruker Elexsys-500 Spectrometer at the X-band microwave frequency 9.4 GHz at 20 K. The microwave frequency was measured with a built-in digital counter and the magnetic field was calibrated using 2,2-diphenyl-1-picrylhydrazyl (DPPH; g=2.0037). The temperature was controlled using an Oxford Instruments cryostat, to accuracy within 0.1 K. Modulation amplitude and microwave power were optimized for high signal-to-noise ratio and narrow peaks. Mass spectrometry was performed at the in-house facility of the Department of Chemistry at the University of Florida. Accurate mass was determined by the electrospray ionization time-of-flight mass spectrometric (ESI-TOF) method in methanol. Combustion analyses were performed at Complete Analysis Laboratory Inc., Parsippany, N.J.

(29) Synthesis of [2,6-.sup.iPrNCN]CrMe(THF) (7)

(30) As indicated in FIG. 1, CrMeCl.sub.2(THF).sub.3 (1.000 g, 2.84 mmol) was added to a solution of {[2,6-.sup.iPrNCHN]Li.sub.2}.sub.2 (1.333 g, 1.42 mmol) in diethyl ether (50 mL) with stirring at 80 C. The reaction was warmed to ambient temperature and stirred for 1 hour. The solution was filtered and the filtrate was evaporated under vacuum to produce a dark solid. Pentane was added (50 mL) and the resulting slurry was filtered. Again, the filtrate was evaporated under vacuum to remove volatiles. The resulting purple-red oil was dissolved in minimal pentane and cooled to 35 C. to yield a purple precipitate. The product was isolated and purified by filtering the solution and washing with cold pentanes. X-ray quality single crystals were obtained by dissolving 2 in minimal diethyl ether and cooling to 35 C. Yield (185 mg, 10%). .sup.1H NMR (300 MHz, C.sub.6D.sub.6) (ppm): 25.53 (bs, .sub.1/2=360 Hz), 10.33 (bs, .sub.1/2=90 Hz), 4.23 (bs, .sub.1/2=300 Hz), 0.75 (bs, .sub.1/2=300 Hz), 7.23 (bs, .sub.1/2=165 Hz), as shown in FIG. 2, .sub.eff=2.68.sub.B. Anal. Calcd. for C.sub.37H.sub.52CrN.sub.2O: C, 74.96; H, 8.84; N, 4.73. Found: C, 74.92; H, 8.96; N, 4.72. An IR spectrum is shown in FIG. 3 and an UV-Visible is shown in FIG. 4. X-ray quality single crystals were obtained by dissolving 7 in minimal diethyl ether and cooling to 35 C.

(31) X-Ray Analysis of 7

(32) Data were collected at 100 K on a Bruker DUO system equipped with an APEX II area detector and a graphite monochromator utilizing MoK.sub. radiation (=0.71073 ). Cell parameters were refined using up to 9999 reflections. A hemisphere of data was collected using the co-scan method (0.5 frame width). Absorption corrections by integration were applied based on measured indexed crystal faces.

(33) The structure was solved by the Direct Methods in SHELXTL6, and refined using full-matrix least squares. The non-H atoms were treated anisotropically, whereas the hydrogen atoms were calculated in ideal positions and were riding on their respective carbon atoms. A CH.sub.2CH.sub.2 group of the coordinated THF ligand is disordered and refined in two parts with their site occupation factors dependently refined. A total of 366 parameters were refined in the final cycle of refinement using 5016 reflections with I>2(I) to yield R.sub.1 and wR.sub.2 of 4.40% and 10.49%, respectively. Refinement was done using F.sup.2. The molecular structure is shown in FIG. 5. Tables 1 through 4, below, give the data determined by the X-ray Diffraction Analysis.

(34) Synthesis of [2,6-.sup.iPrNHCN]Cr(THF).sub.2 (8)

(35) As indicated in FIG. 1, compound 8 was also isolated from the reaction mixture described above. The filtrate from the 7 precipitate was collected and the purple 7 precipitate was again dissolved in a minimal amount of pentane cooling to 35 C. and that precipitate was filtered and the second filtrate combined with the first filtrate. In like manner, a third filtrate was combined with the first and second filtrates that contained only 8 as product. Yield (220 mg, 12%). .sup.1H NMR (300 MHz, C.sub.6D.sub.6) (ppm): 21.71 (bs, .sub.1/2=330 Hz), 7.96 (bs, .sub.1/2=150 Hz), 6.42 (bs, .sub.1/2=330 Hz), 3.54 (bs, .sub.1/2=685 Hz), 6.88 (bs, .sub.1/2=240 Hz), as shown in FIG. 6. .sub.eff=4.42 .sub.B. Anal. Calcd. for C.sub.40H.sub.58CrN.sub.2O.sub.2: C, 73.81; H, 8.98; N, 4.30. Found: C, 73.72; H, 8.85; N, 4.27. An IR spectrum is shown in FIG. 7 and an UV-Visible is shown in FIG. 8.

(36) Alternatively, synthesis of 8 was carried out by adding anhydrous CrCl.sub.2 (524 mg, 4.268 mmol) to a solution of {[2,6-.sup.iPrNCHN]Li.sub.2}.sub.2 (2.00 g, 2.13 mmol) in THF (50 mL) with stirring at 80 C. The reaction mixture was warmed to ambient temperature, stirred for 1 hour, and vacuum applied to remove volatiles resulting in a solid. The solid was dissolved in pentane (50 mL), the solution was filtered, and the filtrate was evaporated under vacuum. The resulting purple-red oil was dissolved in a minimal quantity of ether and cooled to 35 C. to yield 8 as a purple precipitate. Yield (287 mg, 10%). .sup.1H NMR (300 MHz, C.sub.6D.sub.6) (ppm): 21.71 (bs, .sub.1/2=330 Hz), 7.96 (bs, .sub.1/2=150 Hz), 6.42 (bs, .sub.1/2=330 Hz), 3.54 (bs, .sub.1/2=685 Hz), 6.88 (bs, .sub.1/2=240 Hz). .sub.eff=4.42 .sub.B. Anal. Calcd. for C.sub.40H.sub.58CrN.sub.2O.sub.2: C, 73.81; H, 8.98; N, 4.30. Found: C, 73.72; H, 8.85; N, 4.27.

(37) Synthesis of [2,6-.sup.iPrNCN]Cr(THF).sub.3 (9)

(38) CrMeCl.sub.2(THF).sub.3 (1.000 g, 2.84 mmol) was added to a solution of {[2,6-.sup.iPrNCHN]Li.sub.2}.sub.2 (1.333 g, 1.42 mmol) in tetrahydrofuran (50 mL) with stirring at 80 C. The reaction was warmed to room temperature and stirred for 1 h and then all volatiles were removed under vacuum. Nonvolatile products were dissolved in pentane (50 mL) and filtered to collect an orange solid, which was evaporated under vacuum to remove all volatiles. The solid was dissolved in benzene (25 mL) and the solution was filtered, reduced under vacuum, and added to a stirring solution of pentane (50 mL) to precipitate 9 as a black crystalline solid. Yield (1.291 g, 63.0%). .sup.1H NMR (300 MHz, C.sub.6D.sub.6) (ppm): 5.84 (bs, .sub.1/2=270 Hz), 1.95 (br s, .sub.1/2=420 Hz), 5.01 (bs, .sub.1/2=390 Hz), as shown in FIG. 9. .sub.eff=3.99 .sub.B. Anal. Calcd. for C.sub.44H.sub.62CrN.sub.2O.sub.3: C, 73.50; H, 8.69; N, 3.90. Found: C, 73.39; H, 8.51; N, 4.02. An IR spectrum is shown in FIG. 10 and an UV-Visible is shown in FIG. 11

(39) TABLE-US-00001 TABLE 1 Crystal data, structure solution and refinement for 7. identification code Mcg3 empirical formula C.sub.37H.sub.52CrN.sub.2O formula weight 592.81 T (K) 100 (2) () 0.71073 crystal system Monoclinic space group C2/c a () 34.092 (4) b () 11.7102 (14) c () 17.247 (2) (deg) 90 (deg) 104.138 (2) (deg) 90 V (.sup.3) 6676.7 (14) Z 8 .sub.calcd(Mg mm.sup.3) 1.179 crystal size (mm.sup.3) 0.38 0.19 0.03 abs coeff (mm.sup.1) 0.373 F(000) 2560 range for data collection 1.84 to 27.50 limiting indices 44 h 44, 15 k 15, 22 l 22 no. of reflns collcd 52816 no. of ind reflns (R.sub.int) 7675 (0.0958) Completeness to = 27.50 100.0% absorption corr Numerical refinement method Full-matrix least-squares on F.sup.2 data/restraints/parameters 7675/0/366 R1,.sup.a wR2.sup.b [I > 2(I)] 0.0440, 0.1049 [5016] R1,.sup.a wR2.sup.b (all data) 0.0818, 0.1166 GOF.sup.c on F.sup.2 0.969 largest diff. peak and hole 0.542 and 0.610 e .Math. .sup.3 .sup.aR1 = (||F.sub.o| |F.sub.c||)/|F.sub.o|. .sup.bwR2 = ((w(F.sub.o.sup.2 F.sub.c.sup.2).sup.2)/(w(F.sub.o.sup.2).sup.2)).sup.1/2. .sup.cGOF = ( w(F.sub.o.sup.2 F.sub.c.sup.2).sup.2/(n p)).sup.1/2 where n is the number of data and p is the number of parameters refined.

(40) TABLE-US-00002 TABLE 2 Atomic coordinates (10.sup.4) and equivalent isotropic displacement parameters (.sup.2 10.sup.3) for 7. U(eq) is defined as one third of the trace of the orthogonalized Uij tensor. Atom X Y Z U(eq) Cr1 6396(1) 5490(1) 5681(1) 14(1) O1 5882(1) 5166(1) 4664(1) 19(1) N1 6314(1) 7096(2) 5714(1) 16(1) N2 6707(1) 4204(2) 5550(1) 16(1) C1 6003(1) 7794(2) 5227(1) 16(1) C2 5676(1) 8164(2) 5525(1) 17(1) C3 5378(1) 8841(2) 5035(1) 23(1) C4 5403(1) 9153(2) 4278(1) 26(1) C5 6030(1) 8100(2) 4446(1) 18(1) C6 5724(1) 8793(2) 3992(1) 23(1) C7 6600(1) 7775(2) 6334(1) 18(1) C8 6971(1) 7064(2) 6631(1) 15(1) C9 7352(1) 7415(2) 7078(1) 17(1) C10 7664(1) 6617(2) 7250(1) 18(1) C11 7611(1) 5498(2) 6976(1) 17(1) C12 7231(1) 5156(2) 6532(1) 15(1) C13 6915(1) 5932(2) 6384(1) 14(1) C14 7108(1) 4032(2) 6128(1) 16(1) C15 6647(1) 3370(2) 4922(1) 15(1) C16 6403(1) 2405(2) 4942(1) 18(1) C17 6343(1) 1626(2) 4311(1) 23(1) C18 6525(1) 1783(2) 3686(1) 24(1) C19 6775(1) 2710(2) 3684(1) 23(1) C20 6845(1) 3519(2) 4298(1) 17(1) C21 5638(1) 7883(2) 6366(1) 21(1) C22 5232(1) 7322(2) 6377(2) 31(1) C23 5697(1) 8948(2) 6899(1) 25(1) C24 6379(1) 7709(2) 4109(1) 21(1) C25 6289(1) 7769(2) 3193(1) 29(1) C26 6773(1) 8367(2) 4462(2) 30(1) C27 6222(1) 2170(2) 5648(1) 22(1) C28 6368(1) 1019(2) 6034(1) 27(1) C29 5759(1) 2198(2) 5410(2) 37(1) C30 7126(1) 4519(2) 4279(1) 19(1) C31 7564(1) 4120(2) 4366(1) 26(1) C32 6987(1) 5220(2) 3513(1) 26(1) C33 6134(1) 4948(2) 6572(1) 22(1) C34 5467(1) 5371(2) 4693(1) 22(1) C35 5258(1) 5793(2) 3874(2) 35(1) C36 5470(2) 5260(9) 3345(4) 24(1) C37 5862(2) 4716(7) 3871(4) 24(1) C36 5476(2) 4915(10) 3329(4) 24(1) C37 5904(2) 4942(8) 3834(4) 24(1)

(41) TABLE-US-00003 TABLE 3 Bond lengths (in ) for 7. Bond Length Cr1N2 1.8870(18) Cr1N1 1.9048(19) Cr1C13 1.953(2) Cr1C33 2.057(2) Cr1O1 2.1878(15) O1C34 1.448(3) O1C37 1.453(7) O1C37 1.476(7) N1C1 1.436(3) N1C7 1.488(3) N2C15 1.436(3) N2C14 1.496(3) C1C2 1.408(3) C1C5 1.418(3) C2C3 1.397(3) C2C21 1.523(3) C3C4 1.378(3) C4C6 1.372(3) C5C6 1.402(3) C5C24 1.517(3) C7C8 1.498(3) C8C13 1.392(3) C8C9 1.400(3) C9C10 1.394(3) C10C11 1.390(3) C11C12 1.394(3) C12C13 1.385(3) C12C14 1.500(3) C15C16 1.409(3) C15C20 1.413(3) C16C17 1.396(3) C16C27 1.517(3) C17C18 1.383(3) C18C19 1.380(3) C19C20 1.397(3) C20C30 1.518(3) C21C23 1.533(3) C21C22 1.535(3) C24C25 1.535(3) C24C26 1.538(3) C27C29 1.532(3) C27C28 1.532(3) C30C32 1.528(3) C30C31 1.537(3) C34C35 1.503(3) C35C36 1.438(8) C35C36 1.684(9) C36C37 1.555(10) C36C37 1.504(10)

(42) TABLE-US-00004 TABLE 4 Bond angles (in deg) for 7 Bonds Angle N2Cr1N1 152.00(8) N2Cr1C13 80.56(8) N1Cr1C13 80.64(8) N2Cr1C33 101.71(9) N1Cr1C33 100.82(9) C13Cr1C33 96.34(9) N2Cr1O1 97.41(7) N1Cr1O1 95.75(7) C13Cr1O1 165.78(7) C33Cr1O1 97.85(8) C34O1C37 105.7(3) C34O1C37 110.1(3) C37O1C37 12.3(4) C34O1Cr1 122.80(12) C37O1Cr1 131.5(3) C37O1Cr1 126.1(3) C1N1C7 112.11(17) C1N1Cr1 129.60(14) C7N1Cr1 118.28(13) C15N2C14 110.46(17) C15N2Cr1 130.78(14) C14N2Cr1 118.43(13) C2C1C5 120.76(19) C2C1N1 119.90(19) C5C1N1 119.34(19) C3C2C1 118.5(2) C3C2C21 118.8(2) C1C2C21 122.73(19) C4C3C2 121.3(2) C6C4C3 119.9(2) C6C5C1 117.7(2) C6C5C24 120.5(2) C1C5C24 121.83(19) C4C6C5 121.8(2) N1C7C8 107.39(17) C13C8C9 119.3(2) C13C8C7 112.51(19) C9C8C7 128.2(2) C10C9C8 118.6(2) C11C10C9 122.0(2) C10C11C12 119.0(2) C13C12C11 119.4(2) C13C12C14 111.93(18) C11C12C14 128.6(2) C12C13C8 121.7(2) C12C13Cr1 119.12(16) C8C13Cr1 118.63(16) N2C14C12 107.30(17) C16C15C20 120.9(2) C16C15N2 120.16(19) C20C15N2 118.96(19) C17C16C15 118.7(2) C17C16C27 119.7(2) C15C16C27 121.58(19) C18C17C16 120.8(2) C19C18C17 120.1(2) C18C19C20 121.5(2) C19C20C15 117.9(2) C19C20C30 119.9(2) C15C20C30 122.17(19) C2C21C23 111.42(19) C2C21C22 112.95(19) C23C21C22 109.09(19) C5C24C25 113.63(19) C5C24C26 112.70(19) C25C24C26 108.8(2) C16C27C29 112.0(2) C16C27C28 110.86(19) C29C27C28 109.8(2) C20C30C32 111.73(18) C20C30C31 111.43(19) C32C30C31 109.63(19) O1C34C35 105.44(19) C36C35C34 104.8(3) C36C35C36 11.9(4) C34C35C36 98.7(3) C35C36C37 107.6(5) O1C37C36 103.7(5) C37C36C35 99.4(6) O1C37C36 107.1(5)

(43) Isomerization of 1-hexene using [2,6-.sup.iPrNCN]CrMe(THF) (7)

(44) A mixture of [2,6-.sup.iPrNCN]CrMe(THF) (7) (10 mg, 0.017 mmol), 1-hexene (20.5 L, 0.170 mmol), and benzene-d.sub.6 (0.5 mL) was added to a sealable NMR tube under a nitrogen atmosphere. The reaction mixture was heated in a thermostated oil bath at 80 C. (1 C.) for 72 hours. The reaction progress was monitored by .sup.1H NMR spectroscopy at 48, 60, and 72 hours as indicated in Table 5, below. The reaction mixture was analyzed by .sup.1H NMR spectroscopy to identify and quantify the organic products. In like manner, the isomerization of 1-octene using equivalent molar quantities, 26.5 L of 1-octene, was investigated, with results given in Table 6, below.

(45) Kinetic Measurements: A kinetic study was set up using the above method and the reaction progress was monitored by .sup.1H NMR spectroscopy at 4, 8, 12, 16, 20, 24, 28, 32, and 36 hours. Conversion, as a percent of 1-hexene converted to 2-hexene, was determined by .sup.1H NMR spectroscopy. This procedure was used to measure the isomerization of 1-octene.

(46) Preheating (24 h, 85 C.): The sample setup was as above with the exception that alkene was not added initially. The reaction mixture in a sealable NMR tube was heated in a thermostated oil bath at 85 C. (+1 C.) for 24 hours. After heating, 1-hexene (52 L, 0.422 mmol) was added to the NMR tube under a nitrogen atmosphere and returned to the oil bath. The reaction progress was monitored by .sup.1H NMR spectroscopy at 2, 4, 8, 12, 16, 20, 24, 28, 32, 36 hours, as shown in FIG. 12 A .sup.13C NMR spectrum of the reaction mixture in d.sub.6-benzene after 24 hours is shown in FIG. 13. This procedure was used to measure the isomerization of 1-octene.

(47) TABLE-US-00005 TABLE 5 Isomerization of 1-Hexene using 7 as Precatalyst Reaction Time trans-2-hexene/ trans-3-hexene/ (h) Conversion (%).sup.a cis-2-hexene (%).sup.a cis-3-hexene (%).sup.a 48 90 (5) 95 (2) 5 (2) 60 95 (1) 92 (2) 8 (2) 72 96 (0) 87 (3) 13 (3) .sup.aPercent conversion and product composition measured by .sup.1H NMR (500 MHz).

(48) TABLE-US-00006 TABLE 6 Isomerization of 1-Octene using 7 as Precatalyst Reaction Time trans-2-octene/ trans-3-octene/ (h) Conversion (%).sup.a cis-2-octene (%).sup.a cis-3-octene (%).sup.a 48 90 (3) 88 (2) 12 (2) 60 95 (2) 86 (3) 14 (3) 72 97 (0) 82 (3) 18 (3) .sup.aPercent conversion and product composition measured by .sup.1H NMR (500 MHz).
Ambient Pressure Polymerization/Oligomerization using 7

(49) To a sealed John-Young NMR tube under a nitrogen atmosphere, 7 (10 mg, 0.017 mmol) was added to benzene-d.sub.6 (0.5 mL). The reaction mixture was evacuated, pressurized with 1 atm of ethylene, and then heated to 80 C. using a thermostatic bath. The reaction was allowed to run for 24 hr, after which MeOH was added to quench the reaction. The resulting polymer was isolated by filtration, rinsed, and thoroughly dried prior to weighing to yield 12 mg of polyethylene.

(50) High Pressure Polymerization/Oligomerization using 7

(51) Polymerization of Ethylene. Polymerization of ethylene to polyethylene (PE) was carried out for the catalyst loadings as indicated in Table 7, below. A 300 mL pressure reactor (Parr Instruments 4560 Series) was charged with 50 mL of toluene and triisobutylaluminum (TIBA), under nitrogen. The reactor was heated to an internal temperature of 75 C. Mechanical stirring was started, and the reactor was purged with ethylene. A solution of catalyst 7 in 1 mL of toluene was injected by syringe into the reactor, to give the catalyst loading indicated in Table 7. The reactor was pressurized to 20 bar with ethylene. Ethylene pressure was kept constant during the reaction. The reaction was carried out for 15 minutes, after which the reactor was vented and cooled. A known amount of cyclohexane was injected, a sample of the liquid was removed, and the sample was filtered for GC analysis. The polymeric material was collected by filtration, washed with acidified methanol (0.1 M), and dried under vacuum at 80 C. for 2 hours prior to weighing.

(52) TABLE-US-00007 TABLE 7 Ethylene Polymerization by [2,6-.sup.iPrNCN]CrMe(THF) (7) Catalyst Loading Ratio Time PE Activity (mol) TIBA/Cr (hours) (grams) (kg/molCr/h) 10 10 0.5 6.355 1,271 5 10 0.25 5.003 4,002 1 35 0.25 1.755 7,020

(53) The polymerization of ethylene was carried out using various concentrations of the precatalyst and an activator or cocatalyst, to determine appropriate combinations to achieve high activities. Table 8, below, gives various formulations investigated with commonly used expensive cocatalysts for single site catalysis, tris(pentafluorophenyl)borane (FAB) and modified methylaluminoxane (MMAO), and with inexpensive TIBA. The higher activities were observed with TIBA, where the catalyst was employed at a low loading and a relatively low ratio of TIBA to 7 was used. As indicated in Table 8 and Table 7 activities as high as 7,020 kg/molCr/h were achieved at 1 mol 7 and a TIBA/7 ratio of 35. Under similar conditions, the polymerization of ethylene was poor with MMAO and FAB as cocatalyst.

(54) TABLE-US-00008 TABLE 8 Ethylene Polymerization by [2,6-.sup.iPrNCN]CrMe(THF) (7).sup.[a]. 7 Temp Mass PE Activity Cocatalyst (mol) Cocatalyst/7 ( C.) (g) (kg/molCr/h) none 10.sup.[b] N/A 50 0 0 none 10.sup.[b] N/A 75 0 0 MMAO 10.sup.[b] 10 50 0.090 18 MMAO 10.sup.[b] 500 50 0.088 18 FAB 10.sup.[b] 1 50 trace 0 FAB 10.sup.[b] 10 50 trace 0 TIBA 5 10 25 0.473 378 TIBA 5 10 50 1.017 814 TIBA 5 10 75 5.003 4,002 TIBA 5 10 100 3.688 2,950 TIBA 5 1 75 trace 0 TIBA 5 2 75 trace 0 TIBA 5 5 75 0.126 101 TIBA 5 20 75 1.206 965 TIBA 5 50 75 0.632 506 TIBA 5 100 75 0.608 486 TIBA 1 10 75 0 0 TIBA 1 20 75 0.188 472 TIBA 1 30 75 1.002 4,008 TIBA 1 35 75 1.755 7,020 TIBA 1 40 75 1.592 6,368 TIBA 1 45 75 0.791 3,164 TIBA 1 50 75 0.615 2,460 TIBA 5.sup.[e] 10 75 0.981 785 .sup.[a]Unless otherwise stated, reactions were performed in a 300 mL pressure reactor using toluene (50 mL) as solvent for 15 min at 20 bar of ethylene. .sup.[b]t = 30 min. .sup.[e]Pressure = 5 bar of ethylene.

(55) All publications referred to or cited herein are incorporated by reference in their entirety, including all figures and tables, to the extent they are not inconsistent with the explicit teachings of this specification.

(56) It should be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application.