Synthesis and Structure of a Mixed-Ligand Dinuclear Ruthenium Trihydrido Complex Supported by Cn* and Cp* Ligands (Cn* = 1,4,7-Trimethyl-1,4,7-triazacyclononane, Cp* = η⁵‑C₅Me₅): Enhancement of Reactivity toward CO₂ by Introduction of the Cn* Ligand

The novel mixed-ligand diruthenium trihydrido complex Cn*Ru­(μ-H)3RuCp* (2; Cn* = 1,4,7-trimethyl-1,4,7-triazacyclononane, Cp* = η5-C5Me5) was synthesized, and its structure was determined by an X-ray diffraction study. Density functional theory (DFT) calculations for 2 revealed that the electron density at the Cn*-ligated ruthenium atom is higher than that at the Cp*-ligated ruthenium atom. Whereas the unmixed Cp*,Cp*-ligated Cp*Ru­(μ-H)4RuCp* (5) exhibited no reactivity toward CO2 at 20 atm, the mixed-ligand complex 2 reacted with CO2 smoothly at atmospheric pressure and afforded the bis­(μ-formato) complex Cn*Ru­(μ-η1:η1-O2CH)2(μ-H)­RuCp* (4) quantitatively.本研究合成了新型混合配体双核钌三氢化物配合物Cn*Ru(μ-H)3RuCp*（2；其中Cn*为1,4,7-三甲基-1,4,7-三氮杂环壬烷，Cp*为η⁵-五甲基环戊二烯基），并通过X射线衍射研究确定了其晶体结构。对配合物2开展的密度泛函理论（Density Functional Theory, DFT）计算显示，与Cn*配位的钌原子的电子密度高于与Cp*配位的钌原子。未混合配体的双Cp*配位配合物Cp*Ru(μ-H)4RuCp*（5）在20 atm压力下对二氧化碳（CO₂）无反应活性，而该混合配体配合物2可在常压下与CO₂顺利反应，并定量生成双(μ-甲酸根)配合物Cn*Ru(μ-η1:η1-O2CH)2(μ-H)RuCp*（4）。