Role Of B(C6f5)(3) In Activating The Nickel-Methyl Complex (Eta(5)-C5h5)Ni(Ch3)(Pph3) To Initiate The Vinyl Polymerization Of Norbornene

The Ni-methyl complex (eta(5)-C5H5)Ni(CH3)(PPh3) (1) reacted with B(C6F5)(3) to give an unstable contact ion-pair complex with a I-L-methyl bridge between the Ni and B atoms. Formation of the B-CH3 bond was confirmed by the reaction of this complex with PPh3 to give [(eta(5)-C5H5)Ni(PPh3)(2)][B(CH3)(C6F5)(3)] which was structurally characterized. Spontaneous decomposition of the contact ion-pair complex yielded (eta(5)-C5H5)Ni(C6F5)(PPh3) which is very stable and does not show any reactions with norbornene with or without added B(C6F5)(3). F-19 NMR study showed that the polynorbornene obtained by the catalysis of 1/B(C6F5)(3) system has the C6F5 end-group. A series of reactions, which includes CH3/C6F5 exchange between the Ni and B centers with concomitant dissociation of PPh3 to accept coordination of a norbornene monomer, is proposed as the route to active species that can initiate vinyl polymerization of norbornene. (C) 2008 Elsevier B.V. All rights reserved.