Rhodium dicarbonyl sites on alumina surfaces. 1. Preparation and characterization of a model system
A high surface area alumina readily chemisorbs the Rh carbonyl compound Rh/sub 2/(CO)/sub 4/Cl/sub 2/ from alkane solvents at room temperature. Samples prepared in this manner containing ca. 1 wt % Rh have been characterized by transmission electron microscopy, transmission infrared spectroscopy, solid state /sup 13/C NMR with magic-angle spinning, and low-temperature ESR. The exchange of Rh-/sup 12/CO surface complexes with gas-phase /sup 13/CO has also been studied. These data indicate such preparations afford dispersed Al-O-Rh(CO)/sub 2/ surface complexes which form dative bonds with neighboring surface hydroxyl or oxo groups, but do not vibrationally or electronically interact with each other. In this way the Rh(CO)/sub 2/ species on this model system are viewed as truly isolated. A model is also proposed for the Rh(CO)/sub 2/ sites which form when alumina-supported Rh salts are reduced in H/sub 2/ and then exposed to CO. By this model those materials also contain roughly square-planar Al-O-Rh(CO)/sub 2/ species, but here they are clustered in aggregates near a minority of paramagnetic Rh sites. The latter serve to enhance the relaxation rates of /sup 13/CO coordinated to the diamagnetic Rh/sup 1 +/ sites in NMR experiments.
- Research Organization:
- Exxon Corporate Research Science Labs., Annandale, NJ
- OSTI ID:
- 5456866
- Journal Information:
- J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 90:15; ISSN JPCHA
- Country of Publication:
- United States
- Language:
- English
Similar Records
XPS study of rhodium carbonyls adsorbed on planar aluminas: formation of geminal dicarbonyl species
Characterization of the adsorbed state of isoprene on alumina and copper-alumina catalysts by sup 13 C NMR and in situ diffuse reflectance infrared spectroscopy
Related Subjects
400201* -- Chemical & Physicochemical Properties
ABSORPTION SPECTROSCOPY
ADSORPTION
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CARBON 13
CARBON COMPOUNDS
CARBON ISOTOPES
CARBON MONOXIDE
CARBON OXIDES
CARBONYLS
CHALCOGENIDES
CHEMICAL PREPARATION
CHEMICAL REACTIONS
DATA
ELECTRON MICROSCOPY
ELECTRON SPIN RESONANCE
ELEMENTS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
EXPERIMENTAL DATA
INFORMATION
INFRARED SPECTRA
ISOTOPE EFFECTS
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
METALS
MICROSCOPY
NUCLEAR MAGNETIC RESONANCE
NUCLEI
NUMERICAL DATA
OXIDES
OXYGEN 18
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
PLATINUM METALS
RESONANCE
RHODIUM
SORPTION
SPECTRA
SPECTROSCOPY
STABLE ISOTOPES
SYNTHESIS
TRANSITION ELEMENTS
TRANSMISSION ELECTRON MICROSCOPY