Reaction of Heavy Transition Metal Cluster complexes-A Kinetic Approach

本项目计划研究重过渡元素氧桥双核配合物氧化还原反应动力学，特别关注氧化桥上与氧化还原过程相关的质子化。有人建议用铼配合物进行研究，因为它们比其他元素具有多种氧化态。以三（2-吡啶基甲基）胺及其类似物为配体，制备了不同氧化态（III，IV）和（IV，IV）的新型二（mu-氧）铼配合物，并对其氧化还原行为进行了电化学研究。对它们在水介质中氧化还原反应的动力学研究有助于了解氧化桥上质子化对还原速率的作用。然而，在电化学研究中被证明是研究质子化效应较好的溶剂乙腈介质中进行的研究存在一些副反应，没有提供预期的信息。随后，我们对相关单核氧(V)配合物的质子偶联氧化还原反应进行了电化学和动力学研究，其中包括本研究制备和结构表征的新配合物反式-[Re(O)(OH)（乙二胺）2]^<2+>和反式-[Re(O)2（咪唑）4]^+，并发现了水和乙腈溶液中氧化还原反应的必要动力学信息。在后一种溶剂中，通过加入不同pK_a值的质子供体，研究了质子偶联氧化还原行为。对钌二聚体[Ru2(mu-O)(mu-CH3COO)2(bpy)2(Meim)2]^<2+>（bpy = 2,2′-联吡啶，Meim = 1-甲基咪唑）的还原动力学进行了进一步的研究，得到了氧化桥质子化作用的一些初步结果。

This project was planned to study kinetics of redox reactions of oxobridged dinuclear complexes of heavy transition elements with special attention to the protonation at the oxide bridge associated with the redox processes. It was proposed to study with rhenium complexes, since they would take variety of oxidation states than any other elements. We have prepared number of new rhenium di (mu-oxo) complexes with different oxidation states, (III,IV) and (IV,IV), with ligands such as tris (2-pyridylmethyl) amine and its analogs, and studied their redox behavior electrochemically. Kinetic study of their redox reactions in aqueous media helped to understand the role of protonation at the oxide bridge on the reduction rate. However, the study in acetonitrile medium, which was proved to be a better solvent to study the protonation effect in electrochemical study, was suffered from some side reactions and did not provide expected information. Subsequently, we studied electrochemical and kinetic studies of proton-coupled redox reactions of related mononuclear oxorhenium (V) complexes which involve new complexes such as trans-[Re(O)(OH)(ethylenediamine)2]^<2+> and trans-[Re(O)2(imidazole)4]^+ prepared and structurally characterized in this study, and found necessary kinetic information on the redox reactions in aqueous and acetonitrile solution. In the latter solvent, proton-coupled redox behavior was studied by adding proton-donors with various pK_a values. Further kinetic study of the reduction of a ruthenium dimer, [Ru2(mu-O)(mu-CH3COO)2(bpy)2(Meim)2]^<2+>(bpy = 2,2'-bipyridine, Meim = 1-methylimidazole) gave some preliminary results on the effect of the protonation at the oxide bridge.