Synthesis and Coordination of a Bisphosphine-[NHC-borane] Compound: A Ligand Framework for Bimetallic Structure Featuring a Boron-Bridging Moiety

We report herein the synthesis of a bisphosphine-[NHC-BH₃] compound and its coordination toward gold. The ligand is shown to support a bimetallic structure bisphosphine-[NHC-BH₃]­(AuCl)₂. The abstraction of one chloride from the gold metal center triggers the activation of a BH₃ fragment, leading to the reductive elimination of H₂ and the formation of a dicationic Au₄²⁺ complex featuring Au centers at the +0.5 oxidation state, via a (μ-H)­Au₂ intermediate, characterized in situ at 183 K. The reactivity of Au₄ with thiophenol led to the reoxidation of the gold metal centers to a (μ-S­(Ph))­Au₂ complex. In the different complexes, borane fragment was shown to bridge the Au₂ core via weak interaction with [BH], [BCl], and [BH₂] moieties.