Silicon version of enamines: Amino-substituted disilenes by the reactions of the disilyne RSitriple bond; length of mdashSiR (R = SiiPr[CH(SiMe3)2]2) with amines

The reaction of 1,1,4,4-tetrakis[bis(trimethylsilyl)methyl]-1,4-diisopropyltetrasila-2-yne 1 with secondary or primary amines produced amino-substituted disilenes R(R2′N)Sidouble bond; length as m-dashSiHR 2a–d (R = SiiPr[CH(SiMe3)2]2, R2′Ndouble bond; length as m-dashEt2N (2a), (CH2CH2)2N (2b), tBu(H)N (2c), and Ph2N (2d)). Spectroscopic and X-ray crystallographic analyses of 2 showed that 2a–c have a nearly coplanar arrangement of the Sidouble bond; length as m-dashSi double bond and the amino group, giving π-conjugation between the Sidouble bond; length as m-dashSi double bond and the lone pair on the nitrogen atom, whereas 2d has a nearly perpendicular arrangement precluding such conjugation. Theoretical calculations indicate that π-conjugation between the π-orbital of the Sidouble bond; length as m-dashSi double bond and the lone pair on the nitrogen atom is markedly influenced by the torsional angle between the Sidouble bond; length as m-dashSi double-bond plane and the amino-group plane.