Bimetallic ruthenium(II) complexes bearing a bis(pyrazolylimidazolylpyridine) ligand bridged by a rotatable single C–C bond or methylene linker were synthesized, structurally characterized, and exhibited diverse catalytic activities for the transfer hydrogenation (TH) reactions of ketones in refluxing isopropyl alcohol. Both the unprotected NH functionality and bridging methylene moiety demonstrated an acceleration effect on such TH reactions. Combination of the NH and CH₂ skeleton functionalities into the bimetallic Ru(II)–NNN complexes remarkably enhanced the catalytic activities of the complex catalysts. Density functional theory calculations have suggested that the difference in the catalytic activities of these Ru(II)–NNN complexes is attributed to the inherent nucleophilic character of the coordinative nitrogen atoms in the bis(NNN) ligand, and the metal–metal interaction resulted from the number of net natural bond orbital charges on these nitrogen atoms.

中文翻译：

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N–H和CH ₂协同骨架对双金属Ru（II）–NNN配合物催化活性的影响：实验和理论研究

合成了带有双（吡唑并咪唑并吡啶）配体的双金属钌（II）配合物，该配体由可旋转的单个CC键或亚甲基连接基桥接，并进行了结构表征，并对酮在回流的异丙醇中的转移加氢（TH）反应具有多种催化活性。 。未保护的NH官能团和桥连的亚甲基部分都显示出对此类TH反应的促进作用。NH和CH _2的组合Ru（II）-NNN双金属配合物的骨架功能显着增强了配合物催化剂的催化活性。密度泛函理论计算表明，这些Ru（II）–NNN配合物催化活性的差异归因于bis（NNN）配体中配位氮原子的固有亲核特性，并且金属与金属之间的相互作用是由这些氮原子上的净自然键轨道电荷的数量。