Pyridine- and Imidazole-Phosphinimine Bidentate Ligand Complexes: Considerations for Ethylene Oligomerization Catalysts
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- 作者：Liam P. Spencer ; Ramadan Altwer ; Pingrong Wei ; Lucio Gelmini ; James Gauld ; and Douglas W. Stephan
- 刊名：Organometallics
- 出版年：2003
- 出版时间：September 15, 2003
- 年：2003
- 卷：22
- 期：19
- 页码：3841 - 3854
- 全文大小：284K
- 年卷期：v.22,no.19(September 15, 2003)
- ISSN：1520-6041
文摘
The series of 2-substituted diphenylphosphine pyridines 1-5 were synthesized andsubsequently oxidized with silyl or aryl azides to give the series of pyridine-phosphinimineligands 2-(Me3SiNPPh2)C5H4N (9), 2-(2,6-Me2C6H3NPPh2)C5H4N (10), 2-(2,6-i-Pr2C6H3NPPh2)C5H4N (11), 2-(2,6-Me2C6H3NPPh2)-6-MeC5H4N (12), 2-(2,6-i-Pr2C6H3NPPh2)-6-MeC5H4N (13), 2-(2,6-Me2C6H3NPPh2)-6-BnC5H4N (14), 2-(2,6-i-Pr2C6H3NPPh2)-6-BnC5H4N(15), 2-(2,6-Me2C6H3NPPh2)-6-SiMe3C5H4N (16), 2-(2,6-i-Pr2C6H3NPPh2)-6-SiMe3C5H4N (17),2-(2,6-Me2C6H3NPPh2)-6-PhC5H4N (18), and 2-(2,6-i-Pr2C6H3NPPh2)-6-PhC5H4N (19). Attempts to oxidize the fluorinated phosphine 2-P(C6F5)2-6-PhC5H3N (6) were unsuccessful.The ligand 9 reacted with PdCl2(PhCN)2 to the give the square-planar, diamagnetic compound(L)PdCl2 (20; L = 9), while the remaining ligands were used to prepare (L)NiBr2 and (L)FeCl2 complexes 21-30 and 31-40 (L = 10-19), respectively. In these complexes the P atomsbecome part of the chelate backbone. In addition, the pyridine-phosphinimines 2-(Ph3P=NCH2)(C5H4N) (44), 2-(Ph3PNCH2)-6-Me(C5H3N) (45), and 2-(Ph3PNCH2)-6-Ph(C5H3N) (46)were also prepared from the reaction of 2-azidomethyl-pyridines with PPh3. In a similarfashion the complexes (L)PdCl2 (47, 48; L = 44, 45), (L)NiBr2 (49-51; L = 44-46), (L)FeCl2(52, 53), and (L)CoCl2 (54, 55; L = 44, 45) were prepared. In addition, the imidazole-phosphines 1-Me-2-(PPh2)C3H2N2 (58), 1-Me-2-(PPh2)-4,5-Ph2C3N2 (59), and 1-Me-2-(PPh2)C7H6N2 (60) were prepared and oxidized to give the imidazole-phosphinimines 1-Me-2-(2,6-Me2C6H3N=PPh2)C3H2N2 (61), 1-Me-2-(2,6-i-Pr2C6H3N=PPh2)C3H2N2 (62), 1-Me-2-(2,6-Me2C6H3N=PPh2)-4,5-Ph2C3N2 (63), 1-Me-2-(2,6-i-Pr2C6H3N=PPh2)-4,5-Ph2C3N2 (64), 1-Me-2-(2,6-Me2C6H3N=PPh2)C7H6N2 (65), 1-Me-2-(2,6-i-Pr2C6H3N=PPh2)C7H6N2 (66) and 1-Me-2-(2,6-i-Pr2C6H3N=PPh2)-4-(t-Bu)C3HN2 (67). Subsequent complexation afforded the species(L)PdCl2 (68; L = 61), (L)NiBr2 (69-75; L = 61-67), and (L)FeCl2 (76-82; L = 61-67).Preliminary screening for activity as catalyst precursors for ethylene polymerization indicatedthat ethylene oligomerization may be occurring. In the case of complexes 30, 40, 74, and 82activation with Et2AlCl(ClC6H5) at 35 
C under 300 psi of ethylene effected modest catalyticdimerization of ethylene to mainly C4 alkenes. DFT computations suggested that inclusionof P into the ligand results in diminished electrophilicity at the metal and thus a weakenedethylene-metal interaction, accounting for the modest catalytic activity. X-ray structuredeterminations were obtained for 2, 20, 26, 27, 35, 37, 40, 49-51, 54, 68, 79, and 82.
C under 300 psi of ethylene effected modest catalyticdimerization of ethylene to mainly C4 alkenes. DFT computations suggested that inclusionof P into the ligand results in diminished electrophilicity at the metal and thus a weakenedethylene-metal interaction, accounting for the modest catalytic activity. X-ray structuredeterminations were obtained for 2, 20, 26, 27, 35, 37, 40, 49-51, 54, 68, 79, and 82.