TEMPERATURE-PROGRAMMED DECOMPOSITION (TPDE) OF [MO(CO)(6)] ON METAL-OXIDE SUPPORTS - A NOVEL TOOL TO ELUCIDATE SURFACE-ACIDITY AND SURFACE-MEDIATED REACTIONS

A novel technique, the temperature programmed decomposition (TPDE) of [Mo(CO)(6)], has been developed to examine surface acid/base propertie s. In particular, the nucleophility of different surface hydroxyl grou ps can be quantified with this method, and it is found that the activa tion energy for decarbonylation of the carbonyl complex correlates wel l with the held strength of the metal cations in the support. Activati on energies are derived from the CO peak maxima in the TPDE spectra by means of the Redhead equation. TPDE is also used to probe surface-med iated reactions of metal carbonyls. The technique enables identificati on of intermediates formed during the thermal decomposition process. C omparison with simulated TPDE spectra provides evidence for cluster fo rmation during decarbonylation. By quantifying the amounts of CO and H -2 generated during the TPDE reaction, the surface concentration of th e adsorbed species and the oxidation state of the central atom can be deduced at any given temperature. (C) 1998 Elsevier Science B.V.