Harnessing transient CAAC-stabilized mesitylborylenes for chalcogen activation.

Newly synthesized adducts of CAAC-bound mesitylborylene with carbon monoxide (CO) and trimethylphosphine (PMe) are established as efficient precursors for the generation of the dicoordinate borylene [(CAAC)BMes] (CAAC = cyclic(alkyl)(amino)carbene), as demonstrated by their ability to activate elemental chalcogens. Upon thermal or photolytic activation, these precursors readily react with sulfur and selenium, yielding boron chalcogenides characterized by terminal boron-chalcogen double bonds. In contrast, the reaction with tellurium leads to the formation of an unusual diradical ditelluride species with a Te-Te bond. Quantum chemical calculations of its electronic structure indicate an open-shell singlet ground state characterized by significant diradical character. Further investigations into the redox behavior of these boron chalcogenides reveal intriguing transformations, including the redox-induced formation and cleavage of E-E bonds.