An efficient synthetic route to stable bis(carbene)borylenes [(L1)(L2)BH].

Two-electron reduction of bis(carbene) boronium salts allows for the preparation of unsymmetrically substituted nucleophilic boron derivatives of type (L1)(L2)BH, which are characterized by X-ray crystallography. A single electron reduction of the same starting materials leads to the corresponding boron-centered radical cations (L1)(L2)BH.+, X--. [ABSTRACT FROM AUTHOR]