Reaction of Heavy Transition Metal Cluster complexes-A Kinetic Approach

本项目计划研究重过渡元素的氧桥双核配合物的氧化还原反应动力学，特别关注与氧化还原过程相关的氧化物桥上的质子化。有人建议用铼配合物进行研究，因为它们比任何其他元素都具有多种氧化态。我们已经制备了一些新的具有不同氧化态，（III，IV）和（IV，IV），与配体，如三（2-吡啶甲基）胺及其类似物的双（μ-氧代）配合物，并研究了它们的氧化还原行为的电化学。动力学研究它们在水介质中的氧化还原反应有助于理解质子化的氧化物桥上的还原速率的作用。然而，在电化学研究中，乙腈被证明是研究质子化效应的较好溶剂，但在乙腈介质中的研究遭受了一些副反应，没有提供预期的信息。随后，我们研究了相关单核氧合铼（V）配合物的质子偶联氧化还原反应的电化学和动力学研究，其中包括本研究中制备和结构表征的新配合物，如反式-[Re（O）（OH）（乙二胺）2]^<2+>和反式-[Re（O）2（咪唑）4]^+，并发现了水溶液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值的质子给体，研究了质子偶联氧化还原行为。对钌二聚体[Ru 2（mu-O）（mu-CH 3COO）2（bpy）2（Meim）2]^<2+>（bpy = 2，2 '-联吡啶，Meim = 1-甲基咪唑）还原的进一步动力学研究给出了氧化物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.