Imido–hydrido complexes of Mo(iv): catalysis and mechanistic aspects of hydroboration reactions

Abstract

Imido–hydrido complexes (ArN)Mo(H)(Cl)(PMe₃)₃ (1) and (ArN)Mo(H)₂(PMe₃)₃ (2) (Ar = 2,6-diisopropylphenyl) catalyse a variety of hydroboration reactions, including the rare examples of addition of HBCat to nitriles to form bis(borylated) amines RCH₂N(BCat)₂. Stoichiometric reactivity of complexes 1 and 2 with nitriles and HBCat suggest that catalytic reactions proceed via a series of agostic borylamido and borylamino complexes. For complex 1, catalysis starts with addition of nitriles across the Mo–H bond to give (ArN)Mo(Cl)(NCHR)(PMe₃)₂; whereas for complex 2 stoichiometric reactions suggest initial addition of HBCat to form the agostic complex Mo(H)₂(PMe₃)₃(η³-NAr-HBcat) (16).