关于（二亚胺）铂（II）二甲基配合物的质子化及随后的还原消除反应，来自低温快速扫描和核磁共振测量的机理信息。

Mechanistic information from low-temperature rapid-scan and NMR measurements on the protonation and subsequent reductive elimination reaction of a (diimine)platinum(II) dimethyl complex.

作者信息

Wik Bror J, Ivanovic-Burmazovic Ivana, Tilset Mats, van Eldik Rudi

机构信息

Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, N-0315 Oslo, Norway.

出版信息

Inorg Chem. 2006 May 1;45(9):3613-21. doi: 10.1021/ic0519537.

DOI:10.1021/ic0519537

PMID:16634593

Abstract

A detailed kinetic study of the protonation and subsequent reductive elimination reaction of a (diimine)platinum(II) dimethyl complex was undertaken in dichloromethane over the temperature range of -90 to +10 degrees C by stopped-flow techniques. Time-resolved UV-vis monitoring of the reaction allowed the assessment of the effects of acid concentration, coordinating solvent (MeCN) concentration, temperature, and pressure. The second-order rate constant for the protonation step was determined to be 15200 +/- 400 M(-1) s(-1) at -78 degrees C, and the corresponding activation parameters are DeltaH = 15.2 +/- 0.6 kJ mol(-1) and DeltaS = -85 +/- 3 J mol(-1) K(-1), which are in agreement with the addition of a proton that results in the formation of the platinum(IV) hydrido complex. The kinetics of the second, methane-releasing reaction step do not show an acid dependence, and the MeCN concentration also does not significantly affect the reaction rate. The activation parameters for the second reaction step were found to be DeltaH = 75 +/- 1 kJ mol(-1), DeltaS = +38 +/- 5 J mol(-1) K(-1), and DeltaV = +18 +/- 1 cm(3) mol(-1), strongly suggesting a dissociative character of the rate-determining step for the reductive elimination reaction. The spectroscopic and kinetic observations were correlated with NMR data and assisted the elucidation of the underlying reaction mechanism.

摘要

通过停流技术，在-90至+10℃的温度范围内，于二氯甲烷中对（二亚胺）铂（II）二甲基配合物的质子化及随后的还原消除反应进行了详细的动力学研究。对该反应进行时间分辨紫外-可见监测，从而评估酸浓度、配位溶剂（乙腈）浓度、温度和压力的影响。质子化步骤的二级速率常数在-78℃时测定为15200±400 M⁻¹ s⁻¹，相应的活化参数为ΔH = 15.2±0.6 kJ mol⁻¹和ΔS = -85±3 J mol⁻¹ K⁻¹，这与质子加成导致铂（IV）氢化物配合物形成的情况相符。第二步即释放甲烷的反应步骤的动力学不显示酸依赖性，乙腈浓度也对反应速率没有显著影响。发现第二步反应的活化参数为ΔH = 75±1 kJ mol⁻¹，ΔS = +38±5 J mol⁻¹ K⁻¹，ΔV = +18±1 cm³ mol⁻¹，强烈表明还原消除反应的速率决定步骤具有解离特征。光谱和动力学观察结果与核磁共振数据相关联，并有助于阐明潜在的反应机理。