The Ni-methyl complex (η 5-C 5H 5)Ni(CH 3)(PPh 3) ( 1) reacted with B(C 6F 5) 3 to give an unstable contact ion-pair complex with a μ-methyl bridge between the Ni and B atoms. Formation of the B-CH 3 bond was confirmed by the reaction of this complex with PPh 3 to give [(η 5-C 5H 5)Ni(PPh 3) 2][B(CH 3)(C 6F 5) 3] which was structurally characterized. Spontaneous decomposition of the contact ion-pair complex yielded (η 5-C 5H 5)Ni(C 6F 5)(PPh 3) which is very stable and does not show any reactions with norbornene with or without added B(C 6F 5) 3. 19F NMR study showed that the polynorbornene obtained by the catalysis of 1/B(C 6F 5) 3 system has the C 6F 5 end-group. A series of reactions, which includes CH 3/C 6F 5 exchange between the Ni and B centers with concomitant dissociation of PPh 3 to accept coordination of a norbornene monomer, is proposed as the route to active species that can initiate vinyl polymerization of norbornene.