Involvement of a Binuclear Species with the Re-C(O)O-Re Moiety in CO2 Reduction Catalyzed by Tricarbonyl Rhenium(I) Complexes with Diimine Ligands: Strikingly Slow Formation of the Re-Re an
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- 作者：Yukiko Hayashi ; Shouichi Kita ; Bruce S. Brunschwig ; and Etsuko Fujita
- 刊名：Journal of the American Chemical Society
- 出版年：2003
- 出版时间：October 1, 2003
- 年：2003
- 卷：125
- 期：39
- 页码：11976 - 11987
- 全文大小：205K
- 年卷期：v.125,no.39(October 1, 2003)
- ISSN：1520-5126
文摘
Excited-state properties of fac-[Re(dmb)(CO)3(CH3CN)]PF6, [Re(dmb)(CO)3]2 (where dmb = 4,4'-dimethyl-2,2'-bipyridine), and other tricarbonyl rhenium(I) complexes were investigated by transient FTIRand UV-vis spectroscopy in CH3CN or THF. The one-electron reduced monomer, Re(dmb)(CO)3S (S =CH3CN or THF), can be prepared either by reductive quenching of the excited states of fac-[Re(dmb)(CO)3(CH3CN)]PF6 or by homolysis of [Re(dmb)(CO)3]2. In the reduced monomer's ground state, the oddelectron resides on the dmb ligand rather than on the metal center. Re(dmb)(CO)3S dimerizes slowly inTHF, kd = 40 ± 5 M-1 s-1. This rate constant is much smaller than those of other organometallic radicalswhich are typically 109 M-1 s-1. The slower rate suggests that the equilibrium between the ligand-centeredand metal-centered radicals is very unfavorable (K 
10-4). The reaction of Re(dmb)(CO)3S with CO2 isslow and competes with the dimerization. Photolysis of [Re(dmb)(CO)3]2 in the presence of CO2 producesCO with a 25-50% yield based on [Re]. A CO2 bridged dimer, (CO)3(dmb)Re-CO(O)-Re(dmb)(CO)3 isidentified as an intermediate. Both [Re(dmb)(CO)3]2(OCO2) and Re(dmb)(CO)3(OC(O)OH) are detectedas oxidation products; however, the previously reported formato-rhenium species is not detected.
10-4). The reaction of Re(dmb)(CO)3S with CO2 isslow and competes with the dimerization. Photolysis of [Re(dmb)(CO)3]2 in the presence of CO2 producesCO with a 25-50% yield based on [Re]. A CO2 bridged dimer, (CO)3(dmb)Re-CO(O)-Re(dmb)(CO)3 isidentified as an intermediate. Both [Re(dmb)(CO)3]2(OCO2) and Re(dmb)(CO)3(OC(O)OH) are detectedas oxidation products; however, the previously reported formato-rhenium species is not detected.