Transition-Metal-Mediated Cleavage of Fluoro-Silanes under Mild Conditions

摘要

Si-F bond cleavage of fluoro-silanes was achieved by transition-metal complexes under mild and neutral conditions. The Iridium-hydride complex [Ir(H)(CO)(PPh3)(3)] was found to readily break the Si-F bond of the diphosphine- difluorosilane {(o-Ph2P)C6H4}(2)Si(F)(2) to afford a silyl complex [{[o-(iPh(2)P)C6H4](2)(F)Si}Ir(CO)(PPh3)] and HF. Density functional theory calculations disclose a reaction mechanism in which a hypervalent silicon species with a dative IrSi interaction plays a crucial role. The IrSi interaction changes the character of the H on the Ir from hydridic to protic, and makes the F on Si more anionic, leading to the formation of H+F- interaction. Then the Si-F and Ir-H bonds are readily broken to afford the silyl complex and HF through sigma-bond metathesis. Furthermore, the analogous rhodium complex [Rh(H)(CO)(PPh3)(3)] was found to promote the cleavage of the Si-F bond of the triphosphine-monofluorosilane {(o-Ph2P)C6H4}(3)Si(F) even at ambient temperature.