XPS study of rhodium carbonyls adsorbed on planar aluminas: formation of geminal dicarbonyl species

Journal Article · Wed Aug 05 00:00:00 EDT 1987 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00250a007· OSTI ID:6182047

Frederick, B G; Apai, G; Rhodin, T N

The rhodium geminal dicarbonyl species has been observed to form from the evaporation of Rh/sub 4/(CO)/sub 12/ onto cooled planar aluminas under ultrahigh vacuum (UHV) conditions. The Rh 3d core level binding energies, Rh:(CO) stoichiometric ratio, and CO bonding site of the geminal dicarbonyl have been determined with X-ray photoelectron spectroscopy (XPS, ESCA). Comparisons are made with Rh/sub 2/(CO)/sub 4/Cl/sub 2/, Rh/sub 4/(CO)/sub 12/, and Rh/sub 6/(CO)/sub 16/ evaporated on amorphous and crystalline carbon supports at low temperatures. The instability of these rhodium carbonyls under UHV at room temperature is demonstrated; therefore, their low-temperature data permit us to correct previously reported values for Rh 3d binding energies of rhodium complexes impregnated on powder catalysts and recommend, in some cases, the species responsible for the previously reported binding energies. They identify the Rh 3d/sub 5/2/ binding energy of the geminal dicarbonyl as 310.2 eV, indicating that the electron density on the rhodium atom is comparable to Rh/sup 3 +/ compounds despite its assigned formal charge of Rh/sup 1 +/. Reversible changes in Rh core level binding energies following repetitive treatments of vacuum and 1 atm CO exposure at room temperature indicate dispersive effect of rhodium and further demonstrate that the planar aluminas behave similarly to conventional powder alumina catalyst systems.

• Research Organization: Cornell Univ., Ithaca
• OSTI ID: 6182047
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 109:16; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ADSORPTION
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
BINDING ENERGY
CARBONYLS
CHALCOGENIDES
COMPLEXES
DATA
ELECTROMAGNETIC RADIATION
ELECTRON SPECTROSCOPY
ENERGY
EXPERIMENTAL DATA
INFORMATION
IONIZING RADIATIONS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PHOTOELECTRON SPECTROSCOPY
RADIATIONS
RHODIUM COMPLEXES
SORPTION
SORPTIVE PROPERTIES
SPECTROSCOPY
SURFACE PROPERTIES
TRANSITION ELEMENT COMPLEXES
X RADIATION