Masaaki Ichinohe

Reactivity of the Disilyne RSi≡SiR (R = SiiPr[CH(SiMe3)2]2) toward Silylcyanide: Two Pathways To Form the Bis-Adduct [RSiSiR(CNSiMe3)2] with Some Silaketenimine Character and a 1,4-Diaza-2,3-disilabenzene Analogue

The reaction of 1,1,4,4-tetrakis[bis(trimethylsilyl)methyl]-1,4-diisopropyltetrasila-2-yne 1 with trimethylsilylcyanide produced the bis-adduct [RSiSiR(CNSiMe(3))(2)] (R = Si(i)Pr[CH(SiMe(3))(2)](2)) 2 and a 1,4-diaza-2,3-disilabenzene analogue 3, which were characterized by spectroscopic data as well as X-ray crystallography (for 2). These two products were produced by different isomers of trimethylsilylcyanide reacting with the disilyne; bis-adduct 2 was formed from the isocyanide form, and compound 3 was produced from the cyanide form followed by cyclization. The bis-adduct 2 is shown on the basis of X-ray crystallography structural data and theoretical studies to exhibit some bis(silaketenimine) character with zwitterionic contributions. The dl-form of dicyano compound 4 was preferentially produced by the reaction of 2 with methanol.

Addition of Amines and Hydroborane to the Disilyne RSi≡SiR (R = SiiPr[CH(SiMe3)2]2) Giving Amino- and Boryl-Substituted Disilenes

The reaction of 1,1,4,4-tetrakis[bis(trimethylsilyl)methyl]-1,4-diisopropyltetrasila-2-yne 1 with diethylamine or diphenylamine produced the corresponding amino-substituted disilenes R(R(2)N)Si=SiHR 2a, b (R = Si(i)Pr[CH(SiMe(3))(2)](2), R = Et (2a), Ph (2b)). The reaction of 1 with 9-borabicyclo[3.3.1]nonane afforded the boryl-substituted disilene R(R(2)B)Si=SiHR 3 (R(2)B = 9-borabicyclo[3.3.1]nonan-9-yl). Spectroscopic and X-ray crystallographic analyses of 2a, b, and 3 showed that 2a and 3 have a coplanar arrangement of the Si=Si double bond and amino or boryl groups, giving pi-conjugation between the Si=Si double bond and the lone pair on the nitrogen atom or vacant 2p orbital on the boron atom, whereas 2b exhibits no such conjugation.

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

The silyl-substituted silylene-NHC complex bis(tri-tert-butylsilyl)silylene-(1,3,4,5-tetramethylimidazol-2-ylidene) [((t)Bu(3)Si)(2)Si:←NHC(Me), 2] was synthesized and isolated as air- and moisture-sensitive orange crystals by reductive debromination of the dibromosilane ((t)Bu(3)Si)(2)SiBr(2) (1) with 2.0 equiv of KC(8) in the presence of NHC(Me). In addition, the silylene-NHC complex 2 cleanly underwent one-electron oxidation with 1.0 equiv of Ph(3)C(+)·Ar(4)B(-) (Ar(4)B(-) = tetrakis[4-(tert-butyldimethylsilyl)-2,3,5,6-tetrafluorophenyl]borate) in benzene to afford the NHC-stabilized silylene radical cation [((t)Bu(3)Si)(2)Si←NHC(Me)](•+)·Ar(4)B(-) (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.