Reductions of phosphine oxides and sulfides by perchlorosilanes: evidence for the involvement of donor-stabilized dichlorosilylene

Hexachlorodisilane reduces phosphine oxides and sulfides to the corresponding phosphines with opposite stereoselectivities. Through quantum mechanical calculations, a new mechanistic picture is reported that explains these stereoselectivities. Phosphine oxides are shown to react via conventional phosphorane intermediates, but phosphine sulfides follow a dramatically different mechanism involving donor-stabilized SiCl(2).