Synthesis and Structural Characterization of a Stable Dimeric Boron(II) Dication

Abstract

A number of boronium ions with the general formula [R2BL2]+ (where L is a donor, such as an amine), some borenium [R2BL]+, and even borinium [R2B]+ ions have been synthesized and structurally characterized.[1] In all these compounds, boron has a formal oxidation state of +III. In addition to the academic interest in the bonding properties in these species, some of them have found application as catalysts in polymerization[2] or Diels-Alder reactions.[3] Boronium cations are also efficient initiators for the dehydrogenation of ammonia-borane.[4] The boron atom of the boronium ions is more or less tetrahedrally coordinated by the two substituents R (for example, amido groups) and two donor ligands L (such as pyridine). In contrast, uncoordinated borinium species, such as the (dimethylamido)(2,2,6,6-tetramethylpiperidino)boron cation,[5] feature an almost linear NBN unit