Transition metal-mediated thermal and photochemical carbon dioxide conversion

As the output of CO{sub 2} from combustion into the environment continues to rise, the search for practical methods for regenerating organic compounds from CO{sub 2} has assumed increased importance. The development of such processes will be assisted by an improved understanding of the chemistry of metal-carbon dioxide complexes, potential intermediates in metal-catalyzed transformations of CO{sub 2}. The initial stage of this project has focused on the thermal and photochemical reactions of discrete CO{sub 2} complexes, resulting in the elucidation of several new CO{sub 2}-splitting reactions. These studies, in turn, have led to the semiserendipitous discovery of a number of other novel/important transformations, including (1) the catalytic hydrogenation of CO{sub 2} to formic acid by [H{sub 2}Rh(PR{sub 3}){sub 3}L]{sup +} complexes; (2) the CO{sub 2}-mediated [Rh(PR{sub 3}){sub 2}(diene)]{sup +}-catalyzed aerobic oxidation of ethers to esters with co-production of formic acid; and (3) the aerobic oxygenation of electron-rich metal-carbonyls and metal-carbonyl-hydrides, forming metal-CO{sub 2} and metal-formate complexes, respectively