Kinetics of Substitution of Weakly Coordinating Nitrate by Chloride in (5-Cp)Ru(CO)(ER3)ONO2 (ER
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- 作者：Minhton Cao ; Liem V. Do ; Norris W. Hoffman ; Man-Lung Kwan ; Julie K. Little ; J. Michael McGilvray ; Christopher B. Morris ; Bjorn C. Sö ; derberg ; Andrzej Wierzbicki ; Thomas R. Cundari ; Charles H. Lake
- 刊名：Organometallics
- 出版年：2001
- 出版时间：May 28, 2001
- 年：2001
- 卷：20
- 期：11
- 页码：2270 - 2279
- 全文大小：161K
- 年卷期：v.20,no.11(May 28, 2001)
- ISSN：1520-6041
文摘
The d6 complexes of formula (
5-Cp)Ru(CO)(ER3)ONO2, where ER3 = AsPh3, PPh3, P(p-anisyl)3, PPh2(o-anisyl), and P(OPh)3, were prepared by reaction of their chloro analogueswith AgNO3 in CH2Cl2. They underwent moderately slow substitution of the relatively weaklycoordinating nitrate by chloride in dry CH2Cl2 in the presence of excess [N(PPh3)2+]Cl-. Akinetics study showed the reaction to be first order in nitrato complex and independent ofchloride salt concentration under pseudo-first-order conditions. First-order rate constantsfor nitrate metathesis follow the trend P(OPh)3 < PPh3 < P(p-anisyl)3 < AsPh3 
PPh2(o-anisyl), with k1 at 25 
C for the first four in the series from 1.4 to 4.4 × 10-5 s-1. Activationparameters for conversion of (5-Cp)Ru(CO)(AsPh3)ONO2 to its chloride are 
H
= 17(2)kcal/mol and S = -21(5) eu. Even use of a slightly moist solvent increased the rate ofnitrate metathesis by 20-30% without changing the form of the rate law. The complexcontaining PPh2(o-anisyl) was approximately 2 orders of magnitude more reactive (k1 = 4.9× 10-3 s-1). A likely explanation is stabilization of a coordinatively unsaturated intermediateby weak coordination of the potentially chelating o-OMe group. A mechanism entailing rate-limiting conversion of the neutral nitrato complex into a coordinatively unsaturated ion-paired species is consistent with this set of data. Semiempirical calculations (PM3(tm)), whichmodel the structures of complexes in these systems quite well, supported such behavior.X-ray crystal structures were determined for the AsPh3 nitrato and chloro complexes andfor the PPh3 chloro complex.
5-Cp)Ru(CO)(ER3)ONO2, where ER3 = AsPh3, PPh3, P(p-anisyl)3, PPh2(o-anisyl), and P(OPh)3, were prepared by reaction of their chloro analogueswith AgNO3 in CH2Cl2. They underwent moderately slow substitution of the relatively weaklycoordinating nitrate by chloride in dry CH2Cl2 in the presence of excess [N(PPh3)2+]Cl-. Akinetics study showed the reaction to be first order in nitrato complex and independent ofchloride salt concentration under pseudo-first-order conditions. First-order rate constantsfor nitrate metathesis follow the trend P(OPh)3 < PPh3 < P(p-anisyl)3 < AsPh3 PPh2(o-anisyl), with k1 at 25 C for the first four in the series from 1.4 to 4.4 × 10-5 s-1. Activationparameters for conversion of (5-Cp)Ru(CO)(AsPh3)ONO2 to its chloride are H = 17(2)kcal/mol and S = -21(5) eu. Even use of a slightly moist solvent increased the rate ofnitrate metathesis by 20-30% without changing the form of the rate law. The complexcontaining PPh2(o-anisyl) was approximately 2 orders of magnitude more reactive (k1 = 4.9× 10-3 s-1). A likely explanation is stabilization of a coordinatively unsaturated intermediateby weak coordination of the potentially chelating o-OMe group. A mechanism entailing rate-limiting conversion of the neutral nitrato complex into a coordinatively unsaturated ion-paired species is consistent with this set of data. Semiempirical calculations (PM3(tm)), whichmodel the structures of complexes in these systems quite well, supported such behavior.X-ray crystal structures were determined for the AsPh3 nitrato and chloro complexes andfor the PPh3 chloro complex.