Ring-Opening Metathesis Polymerization of Cyclic Olefins by (Arylimido)vanadium(V)-Alkylidenes: Highly Active, Thermally Robust Cis Specific Polymerization.

Abstract

Ring-opening metathesis polymerization (ROMP) of various cyclic olefins especially using three (arylimido)vanadium(V)-alkylidene catalysts, V(CHSiMe3)(N-2,6-Cl2C6H3) (OC6F5) (PMe3)2 (3), V(CHSiMe3) (NR)[OC(CF3)3](PMe3)2 [R = Ph (6), 2,6-Cl2C6H3 (7)] have been explored. Complex 3 exhibited the highest catalytic activity (ex. TOF = 603 000 h(-1), 168 s(-1)) for ROMP of norbornene (NBE) among a series of (imido)vanadium(V)-alkylidenes, and the cis-specific living ROMPs of NBE proceeded with remarkable activities (TOF = 125 000-157 000 h(-1) at 25 °C) by the fluorinated alkoxo analogues (6, 7). The activities by 6, 7 increased at high temperature (50 and 80 °C) and/or upon addition of PMe3 without decrease in the cis selectivity (98%). The ROMPs in the presence of 1-hexene by 3, 7 proceeded without significant decrease in the activities, and the Mn values could be controlled by degree of chain transfer (cross metathesis). These dichlorophenylimido analogues (3, 7) were effective for ROMPs of various norbornene derivatives; ROMP of cyclooctene took place by 3, and the activity increased at high temperature (50, 80 °C).