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Trapping of a Borirane Intermediate in the Reductive Coupling of an Arylborane to a Diborene
Alexander Hermann1, Merle Arrowsmith1, Daniel E Trujillo-Gonzalez2
1Institute for Inorganic Chemistry and Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Wüzburg, Am Hubland, 97074 Würzburg, Germany.
Abstract:
The reductive coupling of a N-heterocyclic carbene (NHC)-stabilized aryldibromoborane yields a mixture of trans- and cis-diborenes in which the aryl groups are coplanar with the diborene core. Under dilute reduction conditions two diastereomers of a borirane-borane intermediate are isolated, which upon further reduction give rise to the aforementioned diborene mixture. DFT calculations suggest a mechanism proceeding via nucleophilic attack of a dicoordinate borylene intermediate on the aryl ring and subsequent intramolecular B-B bond formation.
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