Synthesis and structure of 1,4-diphenyl-3-methyl-1,2,3-triazol-5-ylidene palladium complexes and application in catalytic hydroarylation of alkynes

Abstract

An abnormal or mesoionic N-heterocyclic carbene (NHC), namely 1,4-diphenyl-3-methyl-1,2,3-triazol-5-ylidene (Tz), formed from 1,4-diphenyl-3-methyl-1,2,3-triazolium iodide and silver oxide, gave the corresponding silver carbene complex. The transmetalation reaction of the silver carbene complex with PdCl₂(CH₃CN)₂ gave a trans mononuclear complex, [(Tz)₂PdCl₂]. Reaction of the silver carbene complex with Pd(OAc)₂ gave an acetate-bridged binuclear complex in which the palladium had undergone a C−H insertion at the ortho position of the phenyl group attached to the triazole nitrogen (1-position). The structures of these two complexes were established by single-crystal XRD data and spectroscopic data. The acetate complex was used as a catalyst for the stereoselective hydroarylation of alkynes.