Olefin Metathesis and Stereoselective Ring-Opening Metathesis Polymerization with Neutral and Cationic Molybdenum(VI) Imido and Tungsten(VI) Oxo Alkylidene Complexes Containing N-Chelating N-Heterocyclic Carbenes

Abstract

Neutral and cationic molybdenum(VI) imido and tungsten(VI) oxo alkylidene complexes containing an N-chelating N-heterocyclic carbene, W2) have been prepared. Catalysts Mo2, Mo4, W1, and W2 were characterized by single-crystal X-ray analysis. Catalysts Mo4 and W2 were benchmarked in homo-, cross-, ring-closing metathesis (RCM) as well as in ringopening cross-metathesis (ROCM) reactions. In the ring-opening metathesis polymerization (ROMP) of endo,exo-2,3dicarbomethoxynorborn-5-ene (DCMNBE), methyl-N-(S)-(−)-α-methylbenzyl-2-azabicyclo[2.2.1]hept-5-ene-3-carboxylate, exo-N-(R)-(+)-α-methylbenzyl-5-norbornene-2,3-dicarboximide, and 2,3-bis((menthyloxy)carbonyl)norbornadiene Mo4 and W2 offered access to trans-isotactic and cis-syndiotactic polymers, respectively.