Mono‐ and Di‐Mesoionic Carbene‐Boranes: Synthesis, Structures and Utility as Reducing Agents

Mesoionic carbenes (MIC) of the 1,2,3-triazol-5-ylidene type are currently popular ligands in organometallic chemistry. Their use main group chemistry has been rather limited. In this contribution we present mono- and di-MIC-boranes with MICs based on triazolylidenes. The synthesis involves in-situ deprotonation corresponding triazolium salts their reaction boranes to form desired compounds. Whereas route worked well for all derived from 1,4-regioisomer triazoles, methlyene-bridged bi-triazolium salt a 1,5-substiuted triazole, observed unexpected decomposition formation triazole-borane new N−B bond. All compounds were characterized via multinuclear NMR spectroscopy, mass spectrometry, single crystal X-ray diffraction. Furthermore, MIC-boranes used as reducing agents reduction C=O aldehydes alcohols.