Nonhydrolytic sol-gel routes to layered metal(IV) and silicon phosphonates

Abstract

Three nonhydrolytic routes to methyl and phenylphosphonates have been developed involving the systems: (i) MCl4-RPO(OR)2 or M(OR)4-RPOCl2 (M=Si, Ti); (ii) MCl4-RPOCl2-ether (M=Sn, Ti, Zr); (iii) MCl4-RPOCl2-alcohol (M=Sn, Ti, Zr). It is noteworthy that use of nonhydrolytic conditions opens a route to water-sensitive silicon phosphonates. In most cases the phosphonates were obtained as gels. The poorly crystalline materials obtained after drying were characterised by solid-state NMR spectroscopy and their layered structure could be shown by powder X-ray diffraction. However a higher degree of crystallinity could be obtained under solvothermal conditions, either by the direct alcoholysis of chloride precursors with tert-butanol (2-methylpropan-2-ol), or by a simple postsynthesis treatment in tert-butanol.