In situ high pressure NMR studies of Co{sub 2}(CO){sub 6}[P(p-CF{sub 3}C{sub 6}H{sub 4}){sub 3}]{sub 2} in supercritical carbon dioxide : ligand substitution, hydrogenation, and hydroformylation reactions.
The dimeric cobalt complex Co{sub 2}(CO){sub 6}[P(p-CF{sub 3}C{sub 6}H{sub 4}){sub 3}]{sub 2} (1) reacts reversibly with hydrogen to produce HCo(CO){sub 3}[P(p-CF{sub 3}C{sub 6}H{sub 4}){sub 3}] (4). The carbonyl and the phosphine ligands of both 1 and 4 are very labile. Compound 1 reacts with CO to give Co{sub 2}(CO){sub 7}[P(p-CF{sub 3}C{sub 6}H{sub 4}){sub 3}] (2), and compound 4 reacts with CO and P(p-CF{sub 3}C{sub 6}H{sub 4}){sub 3} (L) to give HCo(CO){sub 4} (5) and HCo(CO){sub 2}[P(p-CF{sub 3}C{sub 6}H{sub 4}){sub 3}]{sub 2} (6), respectively. The {sup 31}P NMR studies show that, in the presence of 1, the line width of the {sup 31}P resonance of L is temperature dependent, and at constant temperature, its broadening is proportional to the square root of the concentration of 1. This broadening is attributed to its exchange reaction with the mononuclear cobalt radical (CO){sub 3}LCo{sup {sm_bullet}} (3), which is generated by the homolysis of 1. Compound 1 catalyzes the hydroformylation of olefins in supercritical carbon dioxide. In contrast to the unsubstituted Co{sub 2}(CO){sub 8}, the phosphine-modified catalyst system is stable under low CO pressures and the hydroformylation reactions can be carried out at low pressures. In situ monitoring of {sup 31}P and {sup 59}Co NMR spectra of the solution shows that the phosphine-containing hydrido cobalt complexes 4 and 6 are the only hydrido cobalt complexes present in detectable concentrations in 1-catalyzed hydroformylation reactions; nevertheless, the possibility that the observed activity for 1 comes primarily from the more active HCo(CO){sub 4}, present in concentrations below detectable limits, has not been rigorously excluded.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 961431
- Report Number(s):
- ANL/CMT/JA-47705; ORGND7; TRN: US201012%%1494
- Journal Information:
- Organometallics, Vol. 23, Issue 11 ; May 24, 2004; ISSN 0276-7333
- Country of Publication:
- United States
- Language:
- ENGLISH
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