Chemical Bond Activation on Surface Sites Generated Photochemically from RhI(CO)₂Species

The activation of chemical bonds in molecules on photochemically produced Rh I sites is reviewed in this article. The focus is primarily on the Rh I (CO) species generated during the ultraviolet photolysis of the well-known Rh I (CO) 2 species supported on an aluminum oxide surface (designated Rh I (CO) 2 /Al 2 O 3 ). The Rh I (CO) 2 surface species is the heterogeneous analogue of the homogeneous phase CpRh(CO) 2 and Cp*Rh(CO) 2 (Cp* = η 5 -C 5 (CH 3 ) 5; Cp = η 5 -C 5 H 5 ) known for its ability to activate the C−H bond in alkanes during ultraviolet irradiation. Here we review some of the key studies that have led to the molecular understanding of the activation of the Rh I (CO) 2 /Al 2 O 3 species by photochemical methods. Relevant examples of the homogeneous-phase bond activation studies utilizing a rhodium center will be discussed as well as theoretical studies that have provided valuable information regarding the active nature of the photoproduced Rh site. This will be followed by a review of recent photochemical studies of surface-bound Rh I (CO) 2 . The coordinatively unsaturated Rh I (CO) species produced photochemically can activate the C−H bond in C 6 H 12 and CH 4, the H−H bond in H 2, the O O bond in O 2, and the C O bond in CO 2 .