19-Electron Intermediates in the Ligand Substitution of CpW(CO)3 with a Lewis Base
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- 作者：James F. Cahoon ; Matthias F. Kling ; Karma R. Sawyer ; Heinz Frei ; and Charles B. Harris
- 刊名：Journal of the American Chemical Society
- 出版年：2006
- 出版时间：March 15, 2006
- 年：2006
- 卷：128
- 期：10
- 页码：3152 - 3153
- 全文大小：89K
- 年卷期：v.128,no.10(March 15, 2006)
- ISSN：1520-5126
文摘
The photochemical reactions of [CpW(CO)3]2 with the Lewis base P(OMe)3 are examined on the nanosecond and microsecond time scales using step-scan FTIR spectroscopy. Photolysis at 532 nm produces the 17-electron (17e) radicals CpW(CO)3
, which are in equilibrium with the 19-electron (19e) radicals CpW(CO)3P(OMe)3 on the nanosecond time scale. The reactions of the 19e radical are directly observed for the first time; the major reaction pathway is spontaneous loss of a carbonyl to form the 17e species CpW(CO)2P(OMe)3, with a barrier of 7.6 ± 0.3 kcal/mol for this process. The minor reaction pathway (<20%) at this concentration of P(OMe)3 (85 mM) is disproportionation to form the products CpW(CO)3P(OMe)3+ and CpW(CO)3-. On the microsecond time scale, the 17e radicals CpW(CO)2P(OMe)3 dimerize to form the ligand substitution product [CpW(CO)2P(OMe)3]2. These results indicate that the 19e species is a stable intermediate rather than transition state in the ligand substitution reaction, and this type of reactivity is likely to be typical of 17e organometallic radicals which undergo associative substitution mechanisms.
, which are in equilibrium with the 19-electron (19e) radicals CpW(CO)3P(OMe)3 on the nanosecond time scale. The reactions of the 19e radical are directly observed for the first time; the major reaction pathway is spontaneous loss of a carbonyl to form the 17e species CpW(CO)2P(OMe)3, with a barrier of 7.6 ± 0.3 kcal/mol for this process. The minor reaction pathway (<20%) at this concentration of P(OMe)3 (85 mM) is disproportionation to form the products CpW(CO)3P(OMe)3+ and CpW(CO)3-. On the microsecond time scale, the 17e radicals CpW(CO)2P(OMe)3 dimerize to form the ligand substitution product [CpW(CO)2P(OMe)3]2. These results indicate that the 19e species is a stable intermediate rather than transition state in the ligand substitution reaction, and this type of reactivity is likely to be typical of 17e organometallic radicals which undergo associative substitution mechanisms.