Physical Organic Chemistry of Transition Metal Carbene Complexes. 23.1 Kinetic and Thermodynamic Acidities of Cationic Benzothienyl- and Selenylcarbene Complexes of Rhenium in Aqueous Aceto
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- 作者：Claude F. Bernasconi and Mark L. Ragains
- 刊名：Journal of the American Chemical Society
- 出版年：2001
- 出版时间：December 5, 2001
- 年：2001
- 卷：123
- 期：48
- 页码：11890 - 11898
- 全文大小：145K
- 年卷期：v.123,no.48(December 5, 2001)
- ISSN：1520-5126
文摘
The pKa values of a cationic selenyl- (5H+) and a benzothienylcarbene complex (6H+) and rateconstants for the reversible deprotonation of these complexes by water, carboxylate ions, primary aliphaticamines, secondary alicyclic amines (5H+ only), and OH- (5H+ only) were determined in 50% MeCN-50%water (v/v) at 25 
C. In comparison with neutral Fischer-type carbene complexes such as 1H, the cationiccomplexes 5H+ and 6H+ are much more acidic, and the intrinsic barriers to proton transfer are substantiallyhigher. This paper discusses a variety of factors that contribute to these differences, with the most importantones being that 5H+ and 6H+ are cationic, which makes the C5H5(NO)(PPh3)Re moiety a stronger 
-acceptorthan the (CO)5M moieties, coupled with the fact that the deprotonated forms of 5H+ and 6H+ are aromaticmolecules.
C. In comparison with neutral Fischer-type carbene complexes such as 1H, the cationiccomplexes 5H+ and 6H+ are much more acidic, and the intrinsic barriers to proton transfer are substantiallyhigher. This paper discusses a variety of factors that contribute to these differences, with the most importantones being that 5H+ and 6H+ are cationic, which makes the C5H5(NO)(PPh3)Re moiety a stronger -acceptorthan the (CO)5M moieties, coupled with the fact that the deprotonated forms of 5H+ and 6H+ are aromaticmolecules.