Three-Coordinate Boron(III) and Diboron(II) Dications

Daniel Franz; Tibor Szilvási; Alexander Pöthig; Franziska Deiser; Shigeyoshi Inoue

doi:10.1002/chem.201800609

Three-Coordinate Boron(III) and Diboron(II) Dications

Chemistry. 2018 Mar 20;24(17):4283-4288. doi: 10.1002/chem.201800609. Epub 2018 Mar 1.

Authors

Daniel Franz¹, Tibor Szilvási², Alexander Pöthig¹, Franziska Deiser¹, Shigeyoshi Inoue¹

Affiliations

¹ Department of Chemistry, Catalysis Research Center, Institute of Silicon Chemistry, Technische Universität München, Lichtenbergstr. 4, 85748, Garching bei München, Germany.
² Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI, 53706-1607, USA.

PMID: 29415320
DOI: 10.1002/chem.201800609

Abstract

The enhanced electron-donor properties of the bulky bisimino ligand 1,2-(L^Mes N)₂ -C₂ H₄ (1; L^Mes =1,3-bis(mesityl)-imidazolin-2-ylidene), mesityl=2,4,6-trimethylphenyl) were exploited for the stabilization of elusive electron-deficient and low-coordinate boron dication species. The reaction of 1 with PhBBr₂ or (B(Cl)NMe₂ )₂ afforded a dicationic mononuclear boron(III) complex or a dicationic dinuclear boron(II) complex, respectively (4²⁺ , 6²⁺ ). The bonding situations of 4²⁺ and 6²⁺ were examined by means of single crystal X-ray diffraction analysis, as well as theoretical methods. Significant allocation of positive charge density into the ligand system was diagnosed for both dications. However, the metalloid-centered Lewis acidity of the dications was confirmed via hydride transfer reactions.

Keywords: N-heterocyclic imines; boron; cations; diboron; subvalent compounds.