The self-stabilizing, tetrameric cyanoborylene [(cAAC)B(CN)] (, cAAC = 1-(2,6-diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidin-2-ylidene) and its diborene relative, [(cAAC)(CN)B[double bond, length as m-dash]B(CN)(cAAC)] (), both react with disulfides and diselenides to yield the corresponding cAAC-supported cyanoboron bis(chalcogenides). Furthermore, reactions of or with elemental sulfur and selenium in various stoichiometries provided access to a variety of cAAC-stabilized cyanoboron-chalcogen heterocycles, including a unique dithiaborirane, a diboraselenirane, 1,3-dichalcogena-2,4-diboretanes, 1,3,4-trichalcogena-2,5-diborolanes and a rare six-membered 1,2,4,5-tetrathia-3,6-diborinane. Stepwise addition reactions and solution stability studies provided insights into the mechanism of these reactions and the subtle differences in reactivity observed between and .
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http://dx.doi.org/10.1039/c7sc04789d | DOI Listing |
J Am Chem Soc
November 2022
Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
The stepwise reduction of a doubly cyclic alkyl(amino)carbene (CAAC)-stabilized 2,3-bis(dibromoboryl)naphthalene enables the isolation of the corresponding mono- and bis(boryl) radicals (one- and two-electron reduction), a 2π-aromatic 1,2-diborete (four-electron reduction), which shows biradical character in the solid-state EPR spectrum, and its cyclic bis(alkylidene)diboron dianion (six-electron reduction). The X-ray crystallographic analysis of the diborete shows a highly strained and twisted four-membered ring with a formal -diborene motif featuring a very elongated B-B double bond. Calculations based on DFT and multireference approaches reveal that the diborete possesses an open-shell singlet biradicaloid ground state, which is slightly energetically preferred to its EPR-active triplet-state congener.
View Article and Find Full Text PDFPhys Chem Chem Phys
June 2022
State Key Laboratory of Physical Chemistry of Solid Surfaces, Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P. R. China.
The activation of thermodynamically stable and kinetically inert dinitrogen (N) has been a great challenge due to the significant strength of the triple bond. Recently, in an experimental study on N activation by boron species, a highly reactive two-coordinated borylene broke through the limitations of traditional strategies of N activation by metal species. Still, studies on metal-free N activation remain underdeveloped.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
August 2020
Department of Chemistry, Brown University, Providence, RI, 02912, USA.
Multiple bonds between boron and transition metals are known in many borylene (:BR) complexes via metal d →BR back-donation, despite the electron deficiency of boron. An electron-precise metal-boron triple bond was first observed in BiB O [Bi≡B-B≡O] in which both boron atoms can be viewed as sp-hybridized and the [B-BO] fragment is isoelectronic to a carbyne (CR). To search for the first electron-precise transition-metal-boron triple-bond species, we have produced IrB O and ReB O and investigated them by photoelectron spectroscopy and quantum-chemical calculations.
View Article and Find Full Text PDFChem Sci
February 2018
Institut für Anorganische Chemie , Julius-Maximilians-Universität Würzburg, Am Hubland , 97074 Würzburg , Germany . Email:
The self-stabilizing, tetrameric cyanoborylene [(cAAC)B(CN)] (, cAAC = 1-(2,6-diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidin-2-ylidene) and its diborene relative, [(cAAC)(CN)B[double bond, length as m-dash]B(CN)(cAAC)] (), both react with disulfides and diselenides to yield the corresponding cAAC-supported cyanoboron bis(chalcogenides). Furthermore, reactions of or with elemental sulfur and selenium in various stoichiometries provided access to a variety of cAAC-stabilized cyanoboron-chalcogen heterocycles, including a unique dithiaborirane, a diboraselenirane, 1,3-dichalcogena-2,4-diboretanes, 1,3,4-trichalcogena-2,5-diborolanes and a rare six-membered 1,2,4,5-tetrathia-3,6-diborinane. Stepwise addition reactions and solution stability studies provided insights into the mechanism of these reactions and the subtle differences in reactivity observed between and .
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