Ethoxysilanes are of growing interest in the fields of immobilized catalysts and chromatography. In spite of this, the reactions of ethoxysilanes with silica surfaces are still not fully explored. This contribution demonstrates that besides the reaction temperature and the degree of dryness of the silica surface, the solvent plays a crucial role during the silanization step: Optimal surface coverage can. for example, be obtained either without solvent or with hydrocarbons likeiso-octane or pentane under mild reaction conditions. Hereby,13C and29Si solid-state NMR spectroscopy serves as a powerful analytical method. The modified silica can be successfully applied for the purification of bifunctional phosphines and their carbonylnickel complexes.