Silicon version of enamines: Amino-substituted disilenes by the reactions of the disilyne RSiSiR (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(R-2'N)Si]Si=HR 2a-d (R = (SiPr)-Pr-i[CH (SiMe3)(2)](2), R-2'N=Et2N (2a), (CH2CH2)(2)N (2b), Bu-t(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 Si=Si double bond and the amino group, giving pi-conjugation between the Si=Si double bond and the lone pair on the nitrogen atom, whereas 2d has a nearly perpendicular arrangement precluding such conjugation. Theoretical calculations indicate that pi-conjugation between the pi-orbital of the Si=Si double bond and the lone pair on the nitrogen atom is markedly influenced by the torsional angle between the Si=Si double-bond plane and the amino-group plane. (C) 2010 Elsevier B.V. All rights reserved.