Silicon version of enamines: Amino-substituted disilenes by the reactions of the disilyne RSi [tbnd]SiR (R = Si iPr[CH(SiMe 3) 2] 2) with amines

Abstract

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 SiHR 2a– d (R = Si i Pr[CH(SiMe 3) 2] 2, R 2′N Et 2N ( 2a), (CH 2CH 2) 2N ( 2b), t Bu(H)N ( 2c), and Ph 2N ( 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 π-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 π-conjugation between the π-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.