Theory predicts anchimeric assistance in olefin polymerization with imidovanadium(V) model catalysts

Gradient-corrected levels of density functional theory have been used to compute the barriers for insertion of ethylene into a V-C bond of V(NR)Me-3 (R = H, tBu, C(CF3)(3), C6H5, p-C6H4OMe, p-C6H4O2, o,p- C6H3(NO2)(2), o-C6H4(COMe)). For the dinitroaryl derivative a notable lowering of the insertion barrier is predicted (to 18.5 kcal/mol) due to stabilization of the transition state by intramolecular chelate formation of the o-nitro group with the metal center, suggesting that experimentally accessible analogues should be active polymerization catalysts.