Half-Sandwich Ruthenium(II) Complexes as Catalysts for Stereoselective Carbene-Carbene Coupling Reactions
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- 作者：Walter Baratta ; Alessandro Del Zotto ; and Pierluigi Rigo
- 刊名：Organometallics
- 出版年：1999
- 出版时间：November 22, 1999
- 年：1999
- 卷：18
- 期：24
- 页码：5091 - 5096
- 全文大小：132K
- 年卷期：v.18,no.24(November 22, 1999)
- ISSN：1520-6041
文摘
Cyclopentadienyl complexes of general formula [RuX(
5-ligand)(PR3)2] have been foundto catalyze the stereoselective decomposition of ethyl diazoacetate (EDA) to form diethylmaleate (DEM) in 95-99% purity with less than 1 mol % of catalyst, at temperaturesdepending on the bulkiness of the phosphine and the 5-ligand as well as the nature of theanionic ligand X. A detailed study of the reaction between [RuCl(5-C5H5)(PPh3)2] and EDAsuggests that dissociation of one PPh3 is a key step of the catalytic process, which proceedsvia the intermediate [RuCl(5-C5H5)(=CHCO2Et)(PPh3)]. Although this electrophilic carbenewas not detected in the reaction mixture, it was independently prepared in solution at lowtemperature starting from [Ru(2-O2CMe)(5-C5H5)(PPh3). The acetate reacts with EDA at-40 
C to form the cyclic ester [Ru{CH(CO2Et)OC(Me) O}(5-C5H5)(PPh3), which on treatmentwith Me2SiCl2 gives the metal carbene postulated in the catalytic cycle. The stoichiometricreaction of the latter compound with EDA selectively affords the olefin derivative [RuCl(5-C5H5)(2-DEM)(PPh3)], which was also detected in the catalytic cycle. The new complexes[RuCl(5-C5H5)(PR3)2] (PR3 = PPh2(2-MeC6H4), PPh2Cy, P(3-MeC6H4)3), bearing phosphinesbulkier than PPh3, have been prepared in high yield starting from ruthenium trichloridehydrate, cyclopentadiene, and phosphine in refluxing ethanol.
5-ligand)(PR3)2] have been foundto catalyze the stereoselective decomposition of ethyl diazoacetate (EDA) to form diethylmaleate (DEM) in 95-99% purity with less than 1 mol % of catalyst, at temperaturesdepending on the bulkiness of the phosphine and the 5-ligand as well as the nature of theanionic ligand X. A detailed study of the reaction between [RuCl(5-C5H5)(PPh3)2] and EDAsuggests that dissociation of one PPh3 is a key step of the catalytic process, which proceedsvia the intermediate [RuCl(5-C5H5)(=CHCO2Et)(PPh3)]. Although this electrophilic carbenewas not detected in the reaction mixture, it was independently prepared in solution at lowtemperature starting from [Ru(2-O2CMe)(5-C5H5)(PPh3). The acetate reacts with EDA at-40 C to form the cyclic ester 5-C5H5)(PPh3),5-C5H5)(2-DEM)(PPh3)], which was also detected in the catalytic cycle. The new complexes[RuCl(5-C5H5)(PR3)2] (PR3 = PPh2(2-MeC6H4), PPh2Cy, P(3-MeC6H4)3), bearing phosphinesbulkier than PPh3, have been prepared in high yield starting from ruthenium trichloridehydrate, cyclopentadiene, and phosphine in refluxing ethanol.