Structure and catalytic activity of metallocomplexes immobilized on supports 4. Heterogenized complexes of Rh(II) in reactions of hydrogenation and hydrogen transfer

Abstract

Acetate, acetonitrile, sulfate, and hexafluoroacetylacetonate binuclear complexes of Rh(II) have been heterogenized on γ-aminopropyl-containing silica gel and on polymers containing 3(5)-methylpyrazole and imidazole groups. Possible paths of surface structure formation have been examined. It has been shown by means of EPR spectrometry, x-ray photoelectron spectroscopy, and electronic spectroscopy that when [Rh2(CO2CCH3)4] is deposited on γ-aminopropylcontaining silica gel and on polymers, the binuclear structure and the degree of oxidation of the metal remain unchanged. Heterogenization of the sulfate, acetonitrile, or hexafluoroacetylacetonate binuclear complexes of Rh(II) takes place with rupture of the Rh-Rh bond and an increase in the degree of oxidation of the central atom. The immobilized complexes manifest activity in allylbenzene hydrogenation and isomerization and also in the reaction of hydrogen transfer from 2-propanol to cyclohexanone. It has been shown that the complexes containing Rh(II) manifest higher activities in these reactions in comparison with the Rh(III) complexes.