Time-Resolved Ftir Study of the Interaction of Cr(CO)6 with Alpha-Cr2O3

The interaction of Cr(CO)6 with polycrystalline alpha-Cr2O3 has been studied by the use of FTIR spectroscopy. Comparison with previous results for the Cr(CO)6/gamma-Al2O3 system shows that the metal carbonyl is adsorbed via O-bonding between a CO ligand and Cr3+ ions coordinatively unsaturated at the surface of the alpha-Cr2O3 support (which act as Lewis acid centres). Time-resolved spectra show that the original surface adduct undergoes partial decarbonylation. Subcarbonyl species thus formed remain anchored to the oxide support. This behaviour contrasts with that found for the Cr(CO)6/gamma-Al2O3 system where no decarbonylation was observed under similar experimental conditions. It is proposed that the high decarbonylating activity of alpha-Cr2O3 could be related to a possible formation of metal-metal bonds between Cr3+ ions at the oxide surface and chromium atoms of the metal carbonyl.