Hydrogenation of CO2 to Formic Acid with a Highly Active Ruthenium Acriphos Complex in DMSO and DMSO/Water. Issue 31 (30th June 2016)

• Record Type: Journal Article
• Authors: Rohmann, Kai; Kothe, Jens; Haenel, Matthias W.; Englert, Ulli; Hölscher, Markus; Leitner, Walter
• Is Part Of: Angewandte Chemie international edition. Volume 55:Issue 31(2016)
• Page Start: 8966
• Page End: 8969
• Publication Date: 2016-06-30
• Subjects: carbon dioxide -- density functional calculations -- hydrogenation -- P ligands -- ruthenium; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201603878
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: The novel [Ru(Acriphos)(PPh3 )(Cl)(PhCO2 )] [1 ; Acriphos=4, 5‐bis(diphenylphosphino)acridine] is an excellent precatalyst for the hydrogenation of CO2 to give formic acid in dimethyl sulfoxide (DMSO) and DMSO/H2 O without the need for amine bases as co‐reagents. Turnover numbers (TONs) of up to 4200 and turn o ver frequencies (TOFs) of up to 260 h −1 were achieved, thus rendering1 one of the most active catalysts for CO2 hydrogenations under additive‐free conditions reported to date. The thermodynamic stabilization of the reaction product by the reaction medium, through hydrogen bonds between formic acid and clusters of solvent or water, were rationalized by DFT calculations. The relatively low final concentration of formic acid obtained experimentally under catalytic conditions (0.33 mol L −1 ) was shown to be limited by product‐dependent catalyst inhibition rather than thermodynamic limits, and could be overcome by addition of small amounts of acetate buffer, thus leading to a maximum concentration of free formic acid of 1.27 mol L −1, which corresponds to optimized values of TON=16×10 3 and TOFavg ≈10 3 h −1 . Abstract : Stable environment : The direct hydrogenation of CO2 into formic acid without the need for amine bases as a product stabilizer is described. Complex1 shows high catalytic productivity and activity. The dimethylsulfoxide (DMSO)/H2 O medium is capable of stabilizing the reaction product thermodynamically, which was rationalized by DFT calculations.