Synthesis and characterization of a homogeneous and silica supported homoleptic cationic tungsten(vi) methyl complex: application in olefin metathesis

Abstract

A method for the synthesis of a homogeneous cationic tungsten(VI)pentamethyl complex [(WMe₅)⁺(C₆F₅)₃BMe⁻] from neutral tungstenhexamethyl (WMe₆) and a silica supported cationic tungstentetramethyl complex [(Si–O–)WMe₄⁺ (C₆F₅)₃BMe⁻] from a neutral silica supported tungstenpentamethyl complex [(Si–O–)WMe₅] is described. In both cases a direct demethylation using the B(C₆F₅)₃ reagent was used. The aforesaid complexes were characterized by liquid or solid state NMR spectroscopy. Interestingly, the homogeneous cationic complex [(WMe₅)⁺(C₆F₅)₃BMe⁻] shows moderate activity whereas the supported cationic complex [(Si–O–)WMe₄⁺(C₆F₅)₃BMe⁻] exhibits good activity in olefin metathesis reactions.