M. Dickson, N. Dixit, D. Roundhill
Oct 1, 1983
Citations
0
Influential Citations
8
Citations
Journal
Inorganic Chemistry
Abstract
Hexarhodium hexadecacarbonyl, Rh/sub 6/(CO)/sub 16/, will cocatalyze a reaction with molecular oxygen involving the conversion both of carbon monoxide to carbon dioxide and of triphenylphosphine (PPh/sub 3/) to triphenylphosphine oxide (OPPh/sub 3/). Solution infrared spectroscopy in the carbonyl region in benzene solvent shows that the catalytic cycle passes through the red Rh/sub 2/(CO)/sub 2/-(PPh/sub 3/)/sub 4/(C/sub 6/H/sub 6/)/sub 2/, the yellow Rh/sub 2/(CO)/sub 6/(PPh/sub 3/)/sub 2/, and the red Rh/sub 4/(CO)/sub 10/(PPh/sub 3/)/sub 2/. Final return to Rh/sub 6/(CO)/sub 16/ does not occur under the ambient temperature and pressure conditions used but can be achieved by elevating these conditions. Addition of carbon dioxide to a mixture of Rh/sub 6/(CO)/sub 16/, CO, and PPh/sub 3/ in the presence of added /sup 18/OH/sub 2/ shows that the rhodium compounds will catalyze oxygen exchange between carbon dioxide and the oxygen atom of water. A pathway for equilibration of oxygen isotope in the catalyzed conversion of coordinated carbonyl to carbon dioxide via metallocarboxylate intermediates is proposed. The equilibration of oxygen isotope from water into carbon dioxide catalyzed by rhodium carbonyl clusters is suggested to proceed via hydroxyrhodium intermediates. 3 figures, 3 tables