Several quaternary onium difluorosilicates 3, R(2)(1)R(2)SiF(2)(-) Q(+) (Q = R(3)(3)R(4)N(+), R(3)(3)R(4)P(+)), have been prepared by reaction of a trisubstitued silane I, R(2)(1)R(2)SiH, and an onium hydrogendifluoride 2, Q(+) HF2-, in benzene. The products 3 are isolated in very good yields (92-98%) and purity (> 99%).