Preparation and characterization of new organic-inorganic hybrid materials incorporating phosphorus centres

Abstract

The reaction of p-bromo(triisopropyloxysilyl)benzene 2 with magnesium led to stable THF solutions of the corresponding Grignard reagent. The reaction of this latter with PCl3 or PhPCl2 allowed the preparation of phosphines 4 and 5 respectively. LiAlH4 reduction of 4 afforded phosphine 6. Compounds 4 and 6 have been transformed into phosphorus derivatives including BH3, W(CO)5, platinum and palladium complexes, all of them bearing three hydrolysable groups. Hydrolysis and condensation of these phosphorus derivatives in the presence of an acid catalyst result in the formation of new hybrid organic-inorganic silica gels incorporating phosphorus centres. Solid state 13C, 29Si, 31P NMR spectroscopies were used to evaluate the integrity of the organic moiety and to determine the degrees of hydrolysis and condensation in the network materials. It was shown that during the sol-gel process there is no alteration around the phosphorus centre. The xerogels are amorphous microporous materials with specific surface areas lying between less than 10m2g1 and 800m2g1 depending on the experimental conditions. In contrast with these results, complete cleavage of the SiC bonds was observed during the hydrolysis and polycondensation of the tris-(triisopropyloxysilylmethyl)phosphine 7 and of tris(trihydrosilylmethyl)phosphine 8.