Reactivity of the Disilyne RSiSiR (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(trimethytsilyl)methyl]-1,4-diisopropyttetrasita-2-yne 1 with trimethylsilytcyanide produced the bis-adduct [RSiSiR(CNSiMe3)(2)] (R = (SiPr)-Pr-i[CH(SiMe3)(2)](2)) 2 and a 1,4-diaza-2,3-disitabenzene 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 trimethylsilycyanide 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.