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Chemistry. 2018 May 1. doi: 10.1002/chem.201801620. [Epub ahead of print]

B-Heterocyclic Carbene Arising from Charge Shift: A Computational Verification.

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Key Laboratory of Macromolecular Science of Shaanxi Province, School of Chemistry & Chemical Engineering, Shaanxi Normal University, Xi'an, 710062, P.R. China.
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, P.R. China.
Department of Chemistry, Western Michigan University, Kalamazoo, MI, 49008, USA.


1-Borabicyclo[1.1.0]but-2(3)-ene (1BB) is a singlet biradical with two single electrons that can form an ionic resonance structure through a charge shift. The ionic resonance structure is a B-heterocyclic carbene (BHC), which can act as a carbene, Lewis base, or L- and Z-type ligand, to give adducts and complexes. Through a range of quantum methods, four types of stable compounds (A-D) derived from 1BB have been designed. These compounds retain the unique features of 1BB. As a consequence, the structures, stability, and Wiberg bond indices of the Lewis adducts of A-D with Lewis acids (BePh2 , BH3 , AlH3 , AlCl3 , C5 BH5 , and C13 BH9 ) and CuI , AgI , and AuI complexes have been investigated. Results show that A-D can indeed react as carbenes. Interestingly, compounds A-D, as L-type ligands, can attach to BePh2 , BH3 , AlH3 , AlCl3 , C5 BH5 , C13 BH9 , and CuCl and form compounds with planar tetracoordinate carbon (ptC), whereas Z-type ligands A-D can bind to AgCl and AuCl to provide complexes with planar tetracoordinate boron (ptB). In addition, the binuclear complexes of ClX(1BB)CuCl (X=Ag, Au) have been studied and A-D behave as both L- and Z-type ligands, in which these complexes contain both ptC and ptB. Thus, a novel method for designing compounds with ptC and ptB is presented. These rationally designed compounds involve the elements of carbene, ptC, ptB, and L- and Z-type ligands, and are expected to be unique and useful in experimental chemistry once they are synthesized.


Lewis acids; ab initio calculations; boron; carbenes; heterocycles


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