Alcohol-Assisted Hydrogenation of Carbon Monoxide to Methanol Using Molecular Manganese Catalysts

Akash Kaithal; Christophe Werlé; Walter Leitner

doi:10.1021/jacsau.0c00091

Alcohol-Assisted Hydrogenation of Carbon Monoxide to Methanol Using Molecular Manganese Catalysts

JACS Au. 2021 Jan 25;1(2):130-136. doi: 10.1021/jacsau.0c00091. eCollection 2021 Feb 22.

Authors

Akash Kaithal¹, Christophe Werlé^{1

2}, Walter Leitner^{1

3}

Affiliations

¹ Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany.
² Ruhr University Bochum, Universitätsstrasse 150, 44801 Bochum, Germany.
³ Institut für Technische und Makromolekulare Chemie, RWTH Aachen University, Worringer Weg 2, 52074 Aachen, Germany.

Abstract

Alcohol-assisted hydrogenation of carbon monoxide (CO) to methanol was achieved using homogeneous molecular complexes. The molecular manganese complex [Mn(CO)₂Br[HN(C₂H₄P ⁱ Pr₂)₂]] ([HN(C₂H₄P ⁱ Pr₂)₂] = MACHO- ⁱ Pr) revealed the best performance, reaching up to turnover number = 4023 and turnover frequency 857 h^-1 in EtOH/toluene as solvent under optimized conditions (T = 150 °C, p(CO/H₂) = 5/50 bar, t = 8-12 h). Control experiments affirmed that the reaction proceeds via formate ester as the intermediate, whereby a catalytic amount of base was found to be sufficient to mediate its formation from CO and the alcohol in situ. Selectivity for methanol formation reached >99% with no accumulation of the formate ester. The reaction was demonstrated to work with methanol as the alcohol component, resulting in a reactive system that allows catalytic "breeding" of methanol without any coreagents.