Vanadium(V) Arylimido Alkylidene N-Heterocyclic Carbene Alkyl and Perhalophenoxy Alkylidenes for the Cis, Syndiospecific Ring Opening Metathesis Polymerization of Norbornene

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Vanadium(V) arylimido alkylidene N -heterocyclic carbene (NHC) alkyl complexes of the type, V(N-2,6-R 2 C 6 H 3 )(CHSiMe 3 )(CH 2 SiMe 3 )(NHC), [R = Me ( 1a – c ), Cl ( 2a, b ); NHC = 1,3-bis(2,6-dimethylphenyl)imidazol-2-ylidene (IXy, a ), 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IDipp, b ), 1,3-bis(cyclohexyl)imidazol-2-ylidene (ICy, c )], and the perhalophenoxy substituted alkylidenes, V(N-2,6-Cl 2 C 6 H 3 )(CHSiMe 3 )(OC 6 X 5 )(IXy) [X = F ( 3 ), Cl ( 4 )], have been prepared. The catalytic activities in the ring opening metathesis polymerization (ROMP) of norbornene (NBE) by 1a – c and 2a, b increased by addition of C 6 X 5 OH (1.0 equiv). The perhalophenoxides 3 and 4 exhibited superior activities with turnover frequencies (TOFs) up to 208 s –1 . The resultant polymers possessed high molecular weights ( M n up to 9.56 × 10 5 ) with cis -syndiotactic stereoregularity up to 98%.