Adsorption of Organo-Rhodium Species on Metal-Oxide Surfaces: Theoretical Aspects
Abstract:
Trisallyl rhodium reacts with hydroxylated Titanium Oxide and Aluminum Oxide surfaces to produce oxide-bound bisallylrhodium which, upon addition if Hydrogen, forms oxide-bound allylrhodium hydride species. The nature of the rhodium-oxygen bonding and the role of the inorganic support are analyzed via extended Huckel ban d calculations on two-dimensional slabs of metal oxideand organo-rhodium adsorbates. Side by side with this analysis we looked at discrete molecular analogues of the surface specied. One-, two-oxygen- bound Rhally2 and one-, two and three-oxygen-bound Rhally H models were examined. There are great similarities between the isolated models and the supported interactions. Crucial to the role of the oxide support is its partial reduction, through defect structures, and resonances between support and adsorbate energy levels. The oxide support not only serves to immobilize the organometallic adsorbate, but might also act as an electron reservoir or electron sink, depending upon the electronic requirements of the adsorbed complexes. Keywords Catalysts Catalysis.