NITROGEN CHEMISORPTION ON THE COORDINATIVELY UNSATURATED RH SITE ON AL2O3

摘要

The UV (3.8 eV) photolysis of atomically-dispersed Rh-1(CO)(2) species supported on an Al2O3 surface in the presence of N-2 at 175 K caused the replacement of CO by N-2 ligands. Therefore dinitrogen chemisorption effectively probes the coordinatively unsaturated Rh(CO) species generated during photodecomposition of Rh-1(CO)(2)/Al2O3. Two infrared bands, observed at 2234 and 2048 cm(-1), are attributed respectively to nu(N2) and nu(CO) in Rh(N2)(CO), and a band at 2188 cm(-1) is assigned to Rh(N-2)(2) surface species. The assignments are based on frequencies and the relative rates of spectral development for the two N-2-containing species. The Rh(N-2)(2) species on Al2O3 exhibits identical N-N stretching modes to a similar species produced by matrix isolation methods. It is shown that both the Rh-CO bond and the Rh-N-2 bond may be broken by photolysis.