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An Isolable NHC-Stabilized Silylene Radical Cation: Synthesis and Structural Characterization

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posted on 28.03.2012, 00:00 by Hiroaki Tanaka, Masaaki Ichinohe, Akira Sekiguchi
The silyl-substituted silylene–NHC complex bis­(tri-tert-butylsilyl)­silylene–(1,3,4,5-tetramethylimidazol-2-ylidene) [(tBu3Si)2Si:←NHCMe, 2] was synthesized and isolated as air- and moisture-sensitive orange crystals by reductive debromination of the dibromosilane (tBu3Si)2SiBr2 (1) with 2.0 equiv of KC8 in the presence of NHCMe. In addition, the silylene–NHC complex 2 cleanly underwent one-electron oxidation with 1.0 equiv of Ph3C+·Ar4B (Ar4B = tetrakis­[4-(tert-butyldimethylsilyl)-2,3,5,6-tetrafluorophenyl]­borate) in benzene to afford the NHC-stabilized silylene radical cation [(tBu3Si)2Si←NHCMe]•+·Ar4B (3). The radical cation 3 was isolated as air- and moisture-sensitive yellow crystals and structurally characterized by X-ray crystallography and electron paramagnetic resonance spectroscopy, which showed that 3 has a planar structure with a π-radical nature.