Synthesis of Ni metal particles by reaction between bis(cyclooctadiene)nickel(0) and sol-gel SiO2 modified with Si-H groups.

Ni-silica composites have been prepared by reacting the zerovalent nickel c omplex bis(cyclooctadiene)nickel(0), Ni(cod)(2), with triethoxysilane, meth yltriethoxysilane, and tetraethoxysilane mixtures engaged in the gelling pr ocess. Nickel particles have been produced within the silica matrix at low temperature. Samples were prepared, changing the ratio between the silica p recursors, the metal load, and the synthesis conditions. XRD, FTIR, TGA and N-2 adsorption data suggest the mechanism for the production of nickel par ticles is based on hydrosilylation of the Si-H moiety of triethoxysilane an d Ni(0)-coordinated olefin, ensuring extreme dispersion of the reduced meta l. The effect of thermal treatment on the silica matrix and metal dispersio n has been studied; in case of triethoxysilane-derived matrices, the averag e size of the Ni particles is slightly modified by the pyrolysis process, c arried out under argon up to 1000 degreesC. The features of the silica matr ix are affected by the Ni dispersion, which changes the Si-O-Si bonding pop ulation, the surface area, the porosity and the pyrolysis behavior of the s ilsesquioxane gel.