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 complex bis(cyclooctadiene)nickel(0), Ni(cod)(2), with triethoxysilane, methyltriethoxysilane, and tetraethoxysilane mixtures engaged in the gelling process. Nickel particles have been produced within the silica matrix at low temperature. Samples were prepared, changing the ratio between the silica precursors, the metal load, and the synthesis conditions. XRD, FTIR, TGA and N-2 adsorption data suggest the mechanism for the production of nickel particles is based on hydrosilylation of the Si-H moiety of triethoxysilane and Ni(0)-coordinated olefin, ensuring extreme dispersion of the reduced metal. The effect of thermal treatment on the silica matrix and metal dispersion has been studied; in case of triethoxysilane-derived matrices, the average size of the Ni particles is slightly modified by the pyrolysis process, carried out under argon up to 1000 degreesC. The features of the silica matrix are affected by the Ni dispersion, which changes the Si-O-Si bonding population, the surface area, the porosity and the pyrolysis behavior of the silsesquioxane gel.