Nitrogen–nitrogen-functionalized N-heterocyclic carbene ruthenium(ii) complexes realized efficient CO2 hydrogenation to formate

Abstract

Three novel Ru(II)–CNN complexes, namely, [RuH(CO)(PPh₃)₂(κ²-N^imN)]Cl₂ (1), [fac-RuH(CO)(PPh₃)(κ³-CN^HN)]Cl (2) and [fac-RuH(CO)(PPh₃)(κ³-CN^MeN)]Cl (3), have been synthesized for efficient CO₂ hydrogenation to formate. Complex 2 bearing a CN^HN ligand exhibits excellent activity and a long catalytic lifetime of 400 h at 170 °C. Notably, the addition of PPh₃ leads to increased activity and gives a high TON of 6.5 × 10⁵ after 400 h.