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.