Heterogeneous and homogeneous hydrogenation of styrene and stilbene chromium tricarbonyl complexes

Heterogeneous hydrogenation of the styrene and stilbene chromium tricarbonyl complexes by molecular hydrogen on skeletal nickel and palladium on carbon as catalysts was studied. As compared to styrene and stilbene, their arene chromium tricarbonyl analogs are hydrogenated considerably more slowly, which is related, most likely, to strong adsorption of the π-complexes on the catalyst surface. For the homogeneous hydrogenation of these complexes using a H₂PtCl₆-SnCl₂-LiBr system, styrene and η⁶-styrene chromium tricarbonyl are reduced with a high rate, whereas stilbene and its chromium tricarbonyl complex are hydrogenated very slowly. A possibility of reduction of the unsaturated arene chromium tricarbonyl complexes by sodium borohydride in the presence of cobalt(II) chloride as a catalyst was shown. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 44–47, January, 2007.