title: Reductive Insertion of Elemental Chalcogens into Boron-Boron Multiple Bonds.
abstract: The syntheses of sulfur- and selenium-bridged cyclic compounds containing boron stabilized by N-heterocyclic carbenes (NHCs) have been achieved by the reductive insertion of elemental chalcogens into boron-boron multiple bonds. The three pairs of bonding electrons between the boron atoms in the triply bonded diboryne enabled six-electron reduction reactions, resulting in the formation of [2.2.1]-bicyclic systems wherein bridgehead boron atoms are spanned by three chalcogen bridges. A similar reaction using a diborene (boron-boron double bond) resulted in the reductive transfer of both pairs of bonding electrons to three sulfur atoms, yielding a NHC-stabilized trisulfidodiborolane. The demonstration of these six- and four-electron reductions lends support to the presence of three and two pairs of bonding electrons between the boron atoms of the diboryne and diborene, respectively, a fact that may be useful in future discussions on bond order.
authors.affiliation: Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg (Germany). h.braunschweig@uni-wuerzburg.de.
authors.forename: Holger
authors.initials: H
authors.lastname: Braunschweig
authors.affiliation: Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg (Germany).
authors.forename: Theresa
authors.initials: T
authors.lastname: Dellermann
authors.affiliation: Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg (Germany).
authors.forename: William C
authors.initials: WC
authors.lastname: Ewing
authors.affiliation: Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg (Germany).
authors.forename: Thomas
authors.initials: T
authors.lastname: Kramer
authors.affiliation: Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg (Germany).
authors.forename: Christoph
authors.initials: C
authors.lastname: Schneider
authors.affiliation: Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg (Germany).
authors.forename: Stefan
authors.initials: S
authors.lastname: Ullrich
keywords: bicyclic compounds; bond order; boron; multiple bonds; redox chemistry