Reactivity of N-Heterocyclic Carbenes with [Ru3(CO)12] and [Os3(CO)12]. Influence of Ligand Volume and Electronic Effects
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- 作者：Javier A. Cabeza ; Ignacio del Rí ; o ; Daniel Miguel ; Enrique Pé ; rez-Carreñ ; o ; M. Gabriela Sá ; nchez-Vega
- 刊名：Organometallics
- 出版年：2008
- 出版时间：January 28, 2008
- 年：2008
- 卷：27
- 期：2
- 页码：211 - 217
- 全文大小：326K
- 年卷期：v.27,no.2(January 28, 2008)
- ISSN：1520-6041
文摘
The room-temperature reactions of [Ru3(CO)12] and [Os3(CO)12] with a variety of N-heterocyclic carbenes (NHCs) have been studied. [Ru3(CO)12] reacts easily with N,N′-dimethylimidazol-2-ylidene (Me2Im), more slowly with N-methyloxazol-2-ylidene (MeOx), and very slowly with N,N′-dimesitylimidazol-2-ylidene (Mes2Im) to give the corresponding CO substitution products [Ru3(NHC)(CO)11], but it does not react with the very bulky N,N′-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (Dipph2Im). DFT calculations have shown that [Ru3(Dipph2Im)(CO)11] is a minimum in the corresponding potential energy surface; therefore, the absence of reaction between [Ru3(CO)12] and Dipph2Im has a kinetic origin associated with the large volume of this NHC. [Os3(CO)12] reacts with Me2Im to give [Os3(Me2Im)(CO)11]. However, MeOx is not basic enough and Mes2Im and Dipph2Im are too bulky to react with [Os3(CO)12], which is less reactive than [Ru3(CO)12]. Therefore, the reactions of [Ru3(CO)12] and [Os3(CO)12] with NHCs are strongly influenced by the electronic properties and steric demands of the NHCs and also by the intrinsic reactivity of the metal–carbonyls.