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

摘要

Ring-opening metathesis polymerization (ROMP) of various cyclic olefins especially using three (arylimido)-vanadium(V)-alkylidene catalysts, V(CHSiMe_3)(N-2,6-Cl_2C_6H_3) (OC_6F_s) (PMe_3)_2 (3), V(CHSiMe_3) (NR)[OC(CF_3)_3](PMe_3)_2 [R = Ph (6), 2,6-Cl_2C_6H_3 (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 ℃) by the fluorinated alkoxo analogues (6, 7). The activities by 6, 7 increased at high temperature (50 and 80 ℃) and/or upon addition of PMe_3 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 M_n 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 ℃).