H. Miessner et al., SURFACE CARBONYL SPECIES OF COPPER SUPPORTED ON DEALUMINATED Y-ZEOLITE, Journal of the Chemical Society. Faraday transactions, 93(18), 1997, pp. 3417-3422
Citations number
30
Categorie Soggetti
Chemistry Physical","Physics, Atomic, Molecular & Chemical
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.