A homogeneous transition metal complex for clean hydrogen production from methanol–water mixtures

• Published in: Nature chemistry Vol. 5; no. 4; pp. 342 - 347
• Main Authors: Rodríguez-Lugo, Rafael E., Trincado, Mónica, Vogt, Matthias, Tewes, Friederike, Santiso-Quinones, Gustavo, Grützmacher, Hansjörg
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.04.2013; Nature Publishing Group
• Subjects: 639/638/406/911; 639/638/77/885; Alcohol; Alcohols; Analytical Chemistry; Aza Compounds - chemistry; Biochemistry; Carbon; Carbon dioxide; Carbon Dioxide - chemistry; Catalysis; Chemistry; Chemistry/Food Science; Dehydrogenase; Electric currents; Gases; Hydrogen; Hydrogen - chemistry; Hydrogen production; Inorganic Chemistry; Ligands; Methanol - chemistry; Models, Molecular; Molecular Structure; Organic Chemistry; Organometallic Compounds - chemical synthesis; Organometallic Compounds - chemistry; Oxidation-Reduction; Phase Transition; Physical Chemistry; Renewable Energy; Ruthenium; Ruthenium - chemistry; Water - chemistry
• ISSN: 1755-4330; 1755-4349
• DOI: 10.1038/nchem.1595

The development of an efficient catalytic process that mimics the enzymatic function of alcohol dehydrogenase is critical for using biomass alcohols for both the production of H 2 as a chemical energy carrier and fine chemicals under waste-free conditions. Dehydrogenation of alcohol–water mixtures into their corresponding acids with molecular hydrogen as the sole by-product from the reaction can be catalysed by a ruthenium complex with a chelating bis(olefin) diazadiene ligand. This complex, [K(dme) 2 ][Ru(H)(trop 2 dad)], stores up to two equivalents of hydrogen intramolecularly, and catalyses the production of H 2 from alcohols in the presence of water and a base under homogeneous conditions. The conversion of a MeOH–H 2 O mixture proceeds selectively to CO 2 /H 2 gas formation under neutral conditions, thereby allowing the use of the entire hydrogen content (12% by weight). Isolation and characterization of the ruthenium complexes from these reactions suggested a mechanistic scenario in which the trop 2 dad ligand behaves as a chemically ‘non-innocent’ co-operative ligand. A ruthenium complex bearing a chemically and redox-non-innocent tetradentate diolefin diazadiene ligand is shown to be an efficient homogeneous catalyst for the conversion of a 1:1 mixture of methanol and water to hydrogen and carbon dioxide. Development of this process is an important step in the production of hydrogen for use as a fuel from biomass.