ETUDE THEORIQUE DE LA STRUCTURE ET LA DELOCALISATION DE CHARGE DES HALOSILICONATES R-O-Si(CH3)3X

Abstract

: Structures of pentavalent halosiliconates R-O-Si(CH 3 ) 3 X - (X = F - ; Cl - ; Br - ) and (R = CH 3 -; CH 3 -CH 2 -; - CH(CH 3 ) 2 ; -CH=CH 2 ; C 6 H 5 -) are investigated using density functional theory (DFT) calculations at B3LYP/6-31G(d) level to understand the structure bonding characteristics and the delocalization of electron density. Our results indicate that pentavalent fluorosiliconates R-O-Si(CH 3 ) 3 F - are stable intermediates for all substitutions with a trigonal bipyramidal geometry. The substituents prefer the axial position and the loss of alkoxy group is detected via the electronic charge transfer. In the case of X = Cl - ; Br - , the intermediates adopt a structure in which the alkoxy group is nearly double bonding with silicon atom. The loss of Cl - and Br - detected by their negative charge (-0.941) and distance of 3.89 Å from the silicon center. Moreover, the halotrimethylsilyloxyfurane structures (X-TMSOF) are also