Electrochemical Kinetic Study of [Cp*Rh] Complexes Supported by Bis(2-pyridyl)methane Ligands
Electrochemical Kinetic Study of [Cp*Rh] Complexes Supported by Bis(2-pyridyl)methane Ligands
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双(2-吡啶基)甲烷配体支持的[Cp*Rh]配合物的电化学动力学研究
DOI：
10.1021/acs.organomet.0c00747
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发表时间：
2021
期刊：
影响因子：
2.8
通讯作者：
Blakemore, James D.
中科院分区：
文献类型：
--
作者：
Hopkins Leseberg, Julie A.;Lionetti, Davide;Day, Victor W.;Blakemore, James D.
金属有机配合物的氧化还原反应在分子电化学和电催化研究中普遍存在。然而，与这些反应中的各个基本步骤相关的动力学参数的详细知识通常具有挑战性，限制了对可用于构建新催化循环的反应性途径的理解。在这里，模型[Cp*Rh]配合物的氧化还原过程的动力学已被探索取代的双（2-吡啶基）甲烷（dipyridylmethane，dpma）配体。补充以前的工作与[Cp*Rh]配合物轴承2，2 ′-联吡啶配体，我们发现，在这些物种的氧化还原化学的强烈影响破坏环间共轭dpma配体框架。特别是，[Cp*Rh]络合物在桥连亚甲基位置具有不同取代基的κ2-dpma配体在从Rh（II）还原为Rh（I）时经历独特的电化学-化学（EC）过程，如通过循环伏安法观察到的;瞬时电生成的Rh（I）物质经历配体重排，导致dpma平台上的一个吡啶基序的面η 2配位。一类含二甲基（Me ~ 2dpma）-、二苄基（Bn ~ 2dpma）-、甲基、甲基芘基-的[Cp ~*Rh]配合物的研究（MePyrdpma）-和bis（甲基芘基）（Pyr 2dpma）-取代的dpma配体揭示了与涉及配体重排的EC过程相关的一级速率常数的一致趋势，提供了对关键过程的动力学洞察，该关键过程能够通过取代的DPMA型配体稳定低价铑。
Redox-induced reactions of organometallic complexes are ubiquitous in molecular electrochemistry and electrocatalysis research. However, a detailed knowledge of the kinetic parameters associated with individual elementary steps in these reactions is often challenging to obtain, limiting an understanding of the reactivity pathways that can be used to construct new catalytic cycles. Here, the kinetics of redox processes in model [Cp*Rh] complexes have been explored with substituted bis(2-pyridyl)methane (dipyridylmethane, dpma) ligands. Complementing prior work with [Cp*Rh] complexes bearing 2,2′-bipyridyl ligands, we find that the redox chemistry in these species is strongly affected by the disrupted inter-ring conjugation of dpma ligand frameworks. In particular, [Cp*Rh] complexes bearing κ2-dpma ligands with varying substitution at the bridging methylene position undergo a unique electrochemical–chemical (EC) process upon reduction from Rh(II) to Rh(I) as observed by cyclic voltammetry; transient electrogenerated Rh(I) species undergo a ligand rearrangement that results in facial η2coordination of one pyridine motif on the dpma platform. Studies of a family of [Cp*Rh] complexes bearing dimethyl (Me2dpma)-, dibenzyl (Bn2dpma)-, methyl,methylpyrenyl- (MePyrdpma)-, and bis(methylpyrenyl) (Pyr2dpma)-substituted dpma ligands reveal a uniform trend in the first-order rate constants associated with this EC process involving ligand rearrangement, providing kinetic insight into a key process that enables the stabilization of low-valent rhodium by substituted dpma-type ligands.