The reaction of O=VX(3), where X is Cl or (OPr)-Pr-i, with the hydroxyl-terminated silica surface gives the well-defined surface complexes =SiOVOX(2). These complexes have been characterized by V-51 magic angle spinning and C-13 cross polarization magic angle spinning NMR spectroscopy and infrared spectroscopy. The surface complexes undergo clean ligand replacement reactions with alcohols, similar to the reactions of analogous molecular vanadium complexes and relevant to the understanding of mechanisms in catalysis.