Synthesis and Reduction of Sterically Encumbered Mesoionic Carbene-Stabilized Aryldihaloboranes.

ABSTRACT

Sterically hindered, in situ generated 1,3,4-substituted 1,2,3-triazol-5-ylidene mesoionic carbenes (MICs) were employed to stabilize a number of aryl- and heteroaryldihaloboranes, as well as the first MIC-supported diborane. Reduction of borane adducts of the 1-(2,6-diisopropylphenyl)-3-methyl-4-tert-butyl-1,2,3-triazol-5-ylidene ligand with KC8 in non-coordinating solvents led to intramolecular C-H- and, C-C-activation at an isopropyl residue of the supporting ligand. DFT calculations showed that each of these activation reactions proceeds via a different isomer of a borylene intermediate.