Illner Peter, Begel Svetlana, Kern Simon, Puchta Ralph, van Eldik Rudi
Inorganic Chemistry, Department of Chemistry and Pharmacy, University of Erlangen-Nurnberg, Egerlandstrasse 1, 91058 Erlangen, Germany.
Inorg Chem. 2009 Jan 19;48(2):588-97. doi: 10.1021/ic801561x.
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 beta 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][NTf(2)] is 2000 times higher than the one measured in [emim][EtOSO(3)]. This difference is much larger than observed for a neutral entering nucleophile studied before.
在准一级条件下，使用停流法和其他动力学技术，研究了几种咪唑基离子液体对Pt(三联吡啶)Cl与硫氰酸盐取代反应速率和机理的影响，该影响是硫氰酸盐浓度和温度的函数。所得速率常数和活化参数与基于密度泛函理论计算（RB3LYP/LANL2DZp）得出的离子液体阴离子与阳离子Pt(II)配合物之间的离子对稳定能，以及与由Kamlet-Taftβ参数设定的线性溶剂化能关系得出的参数显示出良好的一致性，Kamlet-Taftβ参数是溶剂氢键受体能力的一种度量。一般来说，取代反应遵循与传统溶剂中发现的缔合机理，但观察到的速率常数对用作溶剂的离子液体阴离子组分的性质有显著依赖性。在[emim][NTf(2)]中测得的二级速率常数比在[emim][EtOSO(3)]中测得的高2000倍。这种差异比之前研究的中性亲核试剂的情况大得多。
