Mechanistic Studies on the Water-Oxidizing Reaction of Homogeneous Manganese-Based Catalysts: Isolation and Characterization of a Suggested Catalytic Intermediate

The synthesis, isolation, and characterization of two high-valent manganese dimers with isomeric ligands are reported. The complexes are synthesized and crystallized from solutions of low-valent precursors exposed to tert-butyl hydroperoxide. The crystal structures display centrosymmetric complexes consisting of Mn2IV,IV(μ-O)2 cores, with one ligand coordinating to each manganese. The ligands coordinate with the diaminoethane backbone, the carboxylate, and one of the two pyridines, while the second pyridine is noncoordinating. The activity of these complexes, under water oxidation conditions, is discussed in light of a proposed mechanism for water oxidation, in which this type of complexes have been suggested as a key intermediate.

本文报道了两种带有异构配体的高价锰二聚体的合成、分离与表征。该类配合物由与叔丁基过氧化氢（tert-butyl hydroperoxide）接触的低价前驱体溶液合成并结晶得到。其晶体结构均为中心对称配合物，具有Mn₂IV,IV(μ-O)₂双核核心，每个锰原子均与一个配体配位。配体通过乙二胺骨架、羧酸根以及两个吡啶中的一个进行配位，另一个吡啶则不参与配位。本文还探讨了这类配合物在水氧化反应条件下的活性，并结合已提出的水氧化反应机制展开讨论——该类配合物曾被认为是水氧化过程中的关键中间体。