Indenyl-Nickel Complexes Bearing a Pendant, Hemilabile Olefin Ligand: Preparation, Characterization, and Catalytic Activities
作者:Daniel Gareau、Christine Sui-Seng、Laurent F. Groux、François Brisse、Davit Zargarian
DOI:10.1021/om050285u
日期:2005.8.1
The reaction of (PPh3)(2)NiCl2 with Li[Ind boolean AND CH=CH2] gave the neutral complexes (eta:eta(0)-Ind boolean AND CH=CH2)Ni(PPh3)Cl (Ind = indenyl; boolean AND = (CH2)(2), 1a; Si(Me)(2)CH2, 1b), which were subjected to Cl- abstraction to give the corresponding cationic complexes [(eta:eta(2)-Ind boolean AND CH= CH2)Ni(PPh3)](+) (boolean AND = (CH2)(2), 2a; Si(Me)(2)CH2, 2b). The bis(phosphine) derivatives [(eta:eta(0)-Ind-CH2CH2CH=CH2)Ni(PPh3)(2)](+) (3a) and [(eta(3)-allyl)Ni(PPh3)(2)](+) (4) formed gradually from room-temperature solutions of 2a and 2b, respectively, even in the absence of added PPh3. On the other hand, [(eta:eta(0)-Ind-SiMe2CH2CH=CH2)Ni(PPh3)(2)](+) (3b) was detected only when PPh3 was added to a CD2Cl2 solution of 2b. The lability of the vinyl moiety in 2 allows these complexes to act as single-component precatalysts for the polymerization and hydrosilylation of styrene; the latter reaction requires little or no induction period with the hydrosilanes PhRSiH2 (R= Ph, Me, H) and proceeds with up to 1000 catalytic turnovers. Compounds 1a, 1b, 2a, 3a, and 4 have been characterized by NMR and single-crystal X-ray diffraction studies, whereas 2b and 3b were identified by NMR spectroscopy. Structural information gleaned from both solid-state and solution data provide important information on the Ni-olefin bonding in 2a and 2b and indicate that the Ni-Ind interactions in these complexes are affected by the significant trans influence of the chelating olefin moiety.