Bicyclische lithium-t-butylaminofluorsilane, moleküle mit zwei- und vierfachkoordinierten lithium

Abstract

Dimeric lithium-t-butylamino-di-t-butylfluorosilane, [(CMe 3) 2SiFLiNCMe 3] 2, adds one molecule of THF per dimer when crystallized from THF. A bicyclic compound is obtained with fourfold [F 2Li(THF)N] and twofold [NLiN] coordinated lithium. The Si(1)N(1) bond lenght in the six-membered ring has the lenght expected for a ▪bond and is 5.4 pm shorter than the Si(2)N(2) bond of the four-membered ring. The 7Li and the solid state 13C NMR spectra confirm the asymmetry of the molecule. NMR spectra in solution show an equilibration of the H, C, F and Si atoms, a feature which is consistent with fluctuation of Li(1)N(1) and Li(1)N(2) bonds. The THF adduct of lithiated t-butylamino-bis(methyltrimethylsilylamino)-fluorosilane exhibits similar NMR effects.