Catalytic CO2 Hydrogenation to Formate by a Ruthenium Pincer Complex

This paper reports the hydrogenation of carbon dioxide to formate catalyzed by the Ru pincer complex Ru(PNN)CO(H) (PNN = 6-(di-tert-butylphosphinomethylene)-2-(N,N-diethylaminomethyl)-1,6-dihydropyridine). Stoichiometric studies are presented that support the feasibility of the individual steps in a proposed catalytic cycle for this transformation. The influence of base and solvent on catalyst performance is explored. Overall, under optimized conditions (using diglyme as the solvent and potassium carbonate as the base) up to 23,000 turnovers of formate and a turnover frequency of up to 2,200 h(-1) can be achieved.