Mesoionic Carbene–Boranes

Mesoionic carbenes (MICs), derived from alkylation and deprotonation of triazoles, are shown to form stable complexes with BH₃. The synthesis of triazoles via Huigsen cycloadditions provides considerable structural diversity. Several routes to MIC–boranes are described, and their structures have been characterized by X-ray crystallography. As predicted on the basis of the increased σ-donor capacity of MICs by comparison to NHCs, the MIC–borane adducts are more reactive reducing agents