In Situ High-Pressure NMR Studies of Co2(CO)6[P(p-CF3C6H4)3]2 in Supercritical Carbon Dioxide: Ligand Substitution,
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- 作者：Michael J. Chen ; Robert J. Klingler ; Jerome W. Rathke ; and Kurt W. Kramarz
- 刊名：Organometallics
- 出版年：2004
- 出版时间：May 24, 2004
- 年：2004
- 卷：23
- 期：11
- 页码：2701 - 2707
- 全文大小：127K
- 年卷期：v.23,no.11(May 24, 2004)
- ISSN：1520-6041
文摘
The dimeric cobalt complex Co2(CO)6[P(p-CF3C6H4)3]2 (1) reacts reversibly with hydrogento produce HCo(CO)3[P(p-CF3C6H4)3] (4). The carbonyl and the phosphine ligands of both 1and 4 are very labile. Compound 1 reacts with CO to give Co2(CO)7[P(p-CF3C6H4)3] (2), andcompound 4 reacts with CO and P(p-CF3C6H4)3 (L) to give HCo(CO)4 (5) and HCo(CO)2[P(p-CF3C6H4)3]2 (6), respectively. The 31P NMR studies show that, in the presence of 1, the linewidth of the 31P resonance of L is temperature dependent, and at constant temperature, itsbroadening is proportional to the square root of the concentration of 1. This broadening isattributed to its exchange reaction with the mononuclear cobalt radical (CO)3LCo
(3), whichis generated by the homolysis of 1. Compound 1 catalyzes the hydroformylation of olefins insupercritical carbon dioxide. In contrast to the unsubstituted Co2(CO)8, the phosphine-modified catalyst system is stable under low CO pressures and the hydroformylation reactionscan be carried out at low pressures. In situ monitoring of 31P and 59Co NMR spectra of thesolution shows that the phosphine-containing hydrido cobalt complexes 4 and 6 are the onlyhydrido cobalt complexes present in detectable concentrations in 1-catalyzed hydroformylation reactions; nevertheless, the possibility that the observed activity for 1 comes primarilyfrom the more active HCo(CO)4, present in concentrations below detectable limits, has notbeen rigorously excluded.
(3), whichis generated by the homolysis of 1. Compound 1 catalyzes the hydroformylation of olefins insupercritical carbon dioxide. In contrast to the unsubstituted Co2(CO)8, the phosphine-modified catalyst system is stable under low CO pressures and the hydroformylation reactionscan be carried out at low pressures. In situ monitoring of 31P and 59Co NMR spectra of thesolution shows that the phosphine-containing hydrido cobalt complexes 4 and 6 are the onlyhydrido cobalt complexes present in detectable concentrations in 1-catalyzed hydroformylation reactions; nevertheless, the possibility that the observed activity for 1 comes primarilyfrom the more active HCo(CO)4, present in concentrations below detectable limits, has notbeen rigorously excluded.© 2004-2018 中国地质图书馆版权所有 京ICP备05064691号 京公网安备11010802017129号 地址：北京市海淀区学院路29号 邮编：100083 电话：办公室：(+86 10)66554848；文献借阅、咨询服务、科技查新：66554700 |