A crystalline carbene–silylene adduct 1,2-C6H4[N(R)]2C-Si[N(R)]2C6H4-1,2 (R = CH2But); synthesis, structure and bonding in model compounds†

The red–brown, crystalline carbene–silylene adduct, 1,2-C6H4[N(R)]2C-Si[N(R)]2C6H4-1,2 (R = CH2But) 4, was obtained from its factors, the carbene 3 and silylene 1, or from Ni{C[N(R)]2C6H4-1,2}2 and 1; the X-ray structure of 4 shows a long C–Si bond [2.162(5) Å] and NMR spectral data indicate significant C+–Si– bond polarity, features consistent with DFT calculations at the B3LYP/6-311+G** level on [(CH)2(NH)2]C–Si[(NH)2(CH)2], (H2N)2C–Si(NH2)2 or even [(CH)2(NH)2]C–SiH2 and (H2N)2C–SiH2, but not H2CSi(NH2)2 or H2CSi[(NH)2(CH)2].