SURFACE CARBONYL SPECIES OF COPPER SUPPORTED ON DEALUMINATED Y-ZEOLITE

Well defined surface carbonyls of Cu-I with unusually narrow (nu(1/2) < 5 cm(-1)) IR carbonyl bands are formed during the interaction of CO with copper supported on highly dealuminated Y zeolite. A Cu-I monocar bonyl with an IR band at 2159 cm(-1) forms, with additional CO, a dica rbonyl with well resolved IR bands at 2179 and 2153 cm(-1). Isotopic e xchange experiments combined with corresponding force field calculatio ns reveal the C-2v structure of the dicarbonyl and a correlation of th e integrated carbonyl intensities shows the mutual conversion of mono- and di-carbonyl at the same Cu-I site. The reversible equilibrium betw een the two species is dependent on both the temperature and the CO pr essure, with a formation energy of the Cu-I(CO)(2) of 37 kJ mol(-1). T he bond angle between the carbonyl groups in the dicarbonyl is estimat ed to be 113 degrees. Using a controlled hydration, several aquacarbon yls could be observed dependent on the water content. An aquacarbonyl species with a carbonyl band at 2141 cm(-1) is observed when the first doses of water are added. It is transformed, with more water, into sp ecies with IR bands at 2136, 2129 and, finally, 2123 cm(-1), which con tain probably more than one water and/or hydroxy ligand coordinated to the Cu-I.