Highly dispersed nickel and palladium nanoparticle silica aerogels:: sol-gel processing of tethered metal complexes and application as catalysts in the Mizoroki-Heck reaction

Highly dispersed Ni and Pd silica aerogels were prepared through sol - gel processes. They have been synthesized by tethering the metal to the silica matrix with the use of the complexing silanes AEAPTS [N-(aminoethyl) aminopropyl] trimethoxysilane or TRIAMIN [ N-(( aminoethyl) aminoethyl) aminopropyl] trimethoxysilane. The gels were dried with scCO(2) to afford the aerogels. High metal dispersion and small particle sizes were observed through HRTEM and XRD measurements. The organic groups were removed by oxidation and/or pyrolysis. The Pd reduced aerogels containing 15 - 17% of palladium are good recoverable catalysts in the Mizoroki - Heck reaction.