Department of Chemistry, The University of Iowa, E331 Chemistry Building, Iowa City, Iowa 52242, United States.
Department of Chemistry, Colgate University, 13 Oak Drive, Hamilton, New York 13346, United States.
Inorg Chem. 2020 Aug 3;59(15):10845-10853. doi: 10.1021/acs.inorgchem.0c01353. Epub 2020 Jul 8.
Metal-ligand cooperativity (MLC) relies on chemically reactive ligands to assist metals with small-molecule binding and activation, and it has facilitated unprecedented examples of catalysis with metal complexes. Despite growing interest in combining ligand-centered chemical and redox reactions for chemical transformations, there are few studies demonstrating how chemically engaging redox active ligands in MLC affects their electrochemical properties when bound to metals. Here we report stepwise changes in the redox activity of model Ru complexes as zero, one, and two BH molecules undergo MLC binding with a triaryl noninnocent NS ligand derived from -phenylenediamine (). A similar series of Ru complexes with a diaryl NS ligand with ethylene substituted in place of phenylene () is also described to evaluate the influence of the -phenylenediamine subunit on redox activity and MLC. Cyclic voltammetry (CV) studies and density functional theory (DFT) calculations show that MLC attenuates ligand-centered redox activity in both series of complexes, but electron transfer is still achieved when only one of the two redox-active sites on the ligands is chemically engaged. The results demonstrate how incorporating more than one multifunctional reactive site could be an effective strategy for maintaining redox noninnocence in ligands that are also chemically reactive and competent for MLC.
金属-配体协同作用（MLC）依赖于具有反应活性的配体来协助金属与小分子结合和活化，它促进了金属配合物催化的前所未有的例子。尽管人们对结合配体中心的化学反应和氧化还原反应来进行化学转化越来越感兴趣，但很少有研究表明，当与金属结合时，在 MLC 中化学结合氧化还原活性配体如何影响它们的电化学性质。在这里，我们报告了模型 Ru 配合物的氧化还原活性的逐步变化，因为零、一个和两个 BH 分子经历了与三芳基非中性 NS 配体的 MLC 结合，该配体源自 -苯二胺（）。还描述了一系列具有乙烯取代亚苯基的二芳基 NS 配体的类似 Ru 配合物（），以评估 -苯二胺亚基对氧化还原活性和 MLC 的影响。循环伏安法（CV）研究和密度泛函理论（DFT）计算表明，MLC 减弱了两个系列配合物中配体中心的氧化还原活性，但当配体上仅一个两个氧化还原活性位点发生化学结合时，仍能实现电子转移。结果表明，在也是具有反应性和适合 MLC 的配体中，结合多个多功能反应位点如何成为保持氧化还原非中性的有效策略。
