Theoretical study of pentavalent halosiliconates: structure and charge delocalization

Abstract

This study is performed to detect the pentavalent silicon center in the structure of pentavalent halosiliconate R—O—Si(CH3)3X– and halotrimethylsilyloxyfurane structures (X—TMSOF), (X = F–; Cl–; Br–) and (R = CH3—; CH2—CH3; —CH(CH3)2; —CH=CH2; C6H5—). DFT calculations at the B3LYP/6-31G(d) level are caried out to understand their structures and charge delocalization. These intermediates are obtained by attacking the silicon center in trimethyl-alkoxysilanes and trimethyl-silyloxyfurane with halogen ions X–. The results obtained show that the attack by F– generates more stable structures because of the Si—F bond strong. In the case of Br– and Cl–, the structure of intermediates appears as an interaction between the ions and the silicon center. NBO analysis shows that one of F– lone pairs takes part in the Si—F bond formation. However, the lone pairs of Br– and Cl– do not contribute to generate a real bonding.