Influence of Ion Pairing on Styrene Hydrogenation Using a Cationic η6-Arene β-Diketiminato−Ruthenium Complex

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• 作者：Aitor Moreno ; Paul S. Pregosin ; Gbor Laurenczy ; Andrew D. Phillips ; Paul J. Dyson
• 刊名：Organometallics
• 出版年：2009
• 出版时间：November 23, 2009
• 年：2009
• 卷：28
• 期：22
• 页码：6432-6441
• 全文大小：1015K
• 年卷期：v.28,no.22(November 23, 2009)
• ISSN：1520-6041

文摘

A series of salts composed of the coordinatively unsaturated ruthenium β-diketiminato cation [(η⁶-C₆H₆)Ru((ArNCMe)₂CH)]⁺ (Ar = 2,6-dimethylphenyl) and different anions, i.e., OTf⁻ (1), BF₄⁻ (2), PF₆⁻ (3), BPh₄⁻ (4), and BArF⁻ (B((3,5-CF₃)₂C₆H₃)₄⁻) (5), have been prepared and characterized. The solid state structures of 1, 2, and 5 have also been established using single-crystal X-ray diffraction. Both solution and solid state data reveal the presence of anion−cation interactions, the extent of which depends on the nature of the anion, which have been further rationalized via computed charge density profiles using DFT energy optimized models. The catalytic activity of 1−5 in the hydrogenation of styrene was found to be highly dependent on the nature of the counteranion, as inferred from investigations based on high-pressure solution NMR, pulsed gradient spin−echo (PGSE) NMR diffusion, and Overhauser NMR spectroscopy. A good correlation between catalytic activity and the extent and nature of ion pairing was found, and the structure of the active catalytic species is proposed.