Vibrational spectroscopy studies of cobalt and rhodium carbonyls covalently anchored to inorganic oxides

Abstract

Laser Raman, FTIR and photoacoustic/FTIR spectroscopies have been used to study cobalt and rhodium carbonyls immobilized on derivatized inorganic oxide surfaces. Differences in the CO stretching bands of Co 2(CO) 8 covalently attached to phosphinated alumina, phosphinated magnesia, aminated silica gel, aminated magnesium oxide and dicyclohexyl phosphinated silica gel indicate that the structures and the CO stretching bands of covalently attached cobalt carbonyl species are dependent on both the complexing ligands and the supports employed in the synthesis thereof. The CO stretching bands of [RhCl(CO) 2] 2 covalently attached to inorganic oxides functionalized with different lengths and coverages of anchoring ligands indicate that long flexible ligands favor the maintenance of a dinuclear rhodium structure, while short stiff ligands favor the conversion to a mononuclear rhodium carbonyl compound on the surface of the inorganic oxide. Interactions between the attached phosphine or amine compound and the oxide surfaces were reflected in shifts of the characteristic vibrational bands of these compounds.