Supramolecular approach to metal-support interactions: Reactivity of silica-supported bis(allyl)rhodium(III) and the influence of surface hydroxyl groups

The structure and stoichiometric reactivity of a surface organometallic fragment, bis(allyl)rhodium(III) on silica, has been studied in order to identify concepts of molecular chemistry which can be applied to mechanisms of heterogeneous catalysis. The reactions with electrophiles and Lewis bases are examined. The similarity of the 'supramolecular' surface chemistry to molecular chemistry was limited since the surface hydroxyl groups of silica were found to participate. A hydroxyl group in the coordination sphere of rhodium is a source of electrophilic protons, and neighbouring hydroxyl groups facilitate surface mobility of grafted organometallic fragments.