COUPLING NITROSYLS AS THE 1ST STEP IN THE REDUCTION OF NO ON METAL-SURFACES - THE SPECIAL ROLE OF RHODIUM

The adsorption of NO and its coupling to yield N2O2 on Rh(100), Pd(100 ) and Pt(100) surfaces is analyzed using extended Huckel calculations. It appears that the Blyholder model is a valid description of the che misorption of NO on Rh(100). There is substantial weakening of the NO bond on this surface. However, in the case of Pd(100) and Pt(100), the N-O overlap population increases upon chemisorption. For some of the geometries studied, the results indicate that for rhodium surfaces the coupled product has significant N-N double bond character, best descr ibed by the 6pi electron system, hyponitrite. For rhodium surfaces the dimerization of chemisorbed NO seems to be a viable initial step in t he NO reduction mechanism.