Insertion of Nitriles into a Gold(III)/Carbene Bond: A Direct and Powerful Entry to Imino-Substituted Carbenes

Abstract

Strikingly, very little is known so far about gold(III) carbenes. They have been proposed as key intermediates in a few reactions but remain chemical curiosities. Taking into account the enhanced electrophilicity of cationic Au(III) carbene complexes, we were intrigued by their reactivity with nitriles. Thus, we discovered a simple and efficient entry to imino-substituted carbenes. The transient (N^C^C)Au(III)←:CH(dmp)+ carbene readily reacts with acetonitrile, benzonitrile and diisopropyl cyanamide, affording stable and isolable Au(III) carbene complexes. Here, the imino group acts either as a strongly π-donating or a spectator substituent. Ligand exchange at Au(III) or protodeauration/deprotonation provides access to the corresponding free species which display dual imino-carbene / nitrile-ylide reactivity, as substantiated by stoichiometric and catalytic dimerization, O–H insertion and [3+2] cycloaddition reactions.