Fast Substitution Reactions of Pt(II) in Different Ionic Liquids. Reactivity Control by Anionic Components

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• 作者：Peter Illner ; Svetlana Begel ; Simon Kern ; Ralph Puchta ; Rudi van Eldik
• 刊名：Inorganic Chemistry
• 出版年：2009
• 出版时间：January 19, 2009
• 年：2009
• 卷：48
• 期：2
• 页码：588-597
• 全文大小：408K
• 年卷期：v.48,no.2(January 19, 2009)
• ISSN：1520-510X

文摘

The effect of several imidazolium-based ionic liquids on the rate and mechanism of the substitution reaction of [Pt(terpyridine)Cl]⁺ with thiocyanate was investigated as a function of thiocyanate concentration and temperature under pseudo-first-order conditions using stopped-flow and other kinetic techniques. The obtained rate constants and activation parameters showed good agreement with the ion-pair stabilization energies between the anions of the ionic liquids and the cationic Pt(II) complex derived from density-functional theory calculations (RB3LYP/LANL2DZp) and with parameters derived from the linear solvation energy relationship set by the Kamlet-Taft β parameter, which is a measure of a solvent’s hydrogen bonding acceptor ability. In general, the substitution reactions followed an associative mechanism as found for conventional solvents, but the observed rate constants showed a significant dependence on the nature of the anionic component of the ionic liquid used as solvent. The second order rate constant measured in [emim][NTf₂] is 2000 times higher than the one measured in [emim][EtOSO₃]. This difference is much larger than observed for a neutral entering nucleophile studied before.