On the presence or absence of geminal Si ... N interactions (alpha-effect) in pentafluorophenylsilyl compounds with SiCN, SiNN and SiON backbones

Woski M, Berger R, Mitzel NW. On the presence or absence of geminal Si .. N interactions (alpha-effect) in pentafluorophenylsilyl compounds with SiCN, SiNN and SiON backbones. DALTON TRANSACTIONS. 2008;(41):5652-5658.The silanes C6F5SiF2CH2NMe2 (1), C6F5SiF2N(SiMe3)NMe2 (2) and C6F5SiF2ONMe2 (3) with pentafluorophenyl substituents and geminal N atoms have been prepared by the reaction of C6F5SiF3 with LiCH2NMe2, LiN(SiMe3) NMe2 and LiONMe2, respectively. The compounds have been characterised by spectroscopic methods and crystal structure determination. Comparison of measured and calculated IR spectra has provided insight into the conformational composition of the vapour of 3. Whereas 2 and 3 show interactions between the geminal Si and N atoms, 1 does not. Further analysis of the bonding situation has been undertaken by quantum chemical calculations of the rotation and bending potentials of the C6F5SiF2-X-NMe2 units