Role of B(C6F5)3 in activating the nickel-methyl complex (η5-C5H5)Ni(CH3)(PPh3) to initiate the vinyl polymerization of norbornene

✍ Scribed by Takeo Yamamoto; Chie Shikada; Shojiro Kaita; Tardif Olivier; Yooichiroh Maruyama; Yasuo Wakatsuki

• Publisher: Elsevier Science
• Year: 2009
• Tongue: English
• Weight: 506 KB
• Volume: 300
• Category: Article
• ISSN: 1381-1169
• DOI: 10.1016/j.molcata.2008.11.037

✦ Synopsis

The Ni-methyl complex ( 5 -C 5 H 5 )Ni(CH 3 )(PPh 3 ) (1) reacted with B(C 6 F 5 ) 3 to give an unstable contact ion-pair complex with a -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 [( 5 -C 5 H 5 )Ni(PPh 3 ) 2 ][B(CH 3 )(C 6 F 5 ) 3 ] which was structurally characterized. Spontaneous decomposition of the contact ion-pair complex yielded ( 5 -C 5 H 5 )Ni(C 6 F 5 )(PPh 3 ) which is very stable and does not show any reactions with norbornene with or without added B(C 6 F 5 ) 3 . 19 F NMR study showed that the polynorbornene obtained by the catalysis of 1/B(C 6 F 5 ) 3 system has the C 6 F 5 end-group. A series of reactions, which includes CH 3 /C 6 F 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.