A New Disilene with π-Accepting Groups from the Reaction of Disilyne RSirSiR (R = SiiPr[CH(SiMe3)2]) with Isocyanides

The reaction of 1,1,4,4-tetrakis[bis(trimethylsilyl)methyl] -1,4-diisopropyltetrasila-2-yne (1) with tert-butylisocyanide or tert-octylisocyanide produced the corresponding disilyne-isocyanide adducts [RSiSiR-(CNR')(2)] (R = (SiPr)-Pr-i[CH(SiMe3)(2)](2), R' = Bu-t (2a) or (CMe2CH2Bu)-Bu-t (2b)), which are stable below -30 degrees C and were characterized by spectroscopic data and, in the case of 2a, X-ray crystallography. Upon warming to room temperature, 2 underwent thermal decomposition to produce 1,2-dicyanodisilene R(NC)Si=Si(CN)R (3) and 1,2-dicyanodisilane R(NC)HSiSiH(CN)R (4) via C-N bond cleavage and elimination of an alkane and an alkene. The 1,2-dicyanodisilene derivative 3 was characterized by X-ray crystallography.