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Heterogeneous Removal of Water-Soluble Ruthenium Olefin Metathesis Catalyst from Aqueous Media Via Host-Guest Interaction
Published on: August 23, 2018
Diruthenium Catalyst for Hydrogen Production from Aqueous Formic Acid
Sanjeev Kushwaha1, Mahendra Kumar Awasthi1, Amitabha Das2
1Catalysis Group, Department of Chemistry, Indian Institute of Technology Indore, Simrol, Indore 453552, Madhya Pradesh, India.
Abstract:
Diruthenium complexes [{(η6-arene)RuCl}2(μ-κ2:κ2-benztetraimd)]2+ containing the bridging bis-imidazole methane-based ligand {1,4-bis(bis(2-ethyl-5-methyl-1H-imidazol-4-yl)methyl)benzene} (benztetraimd) are synthesized for catalytic formic acid dehydrogenation in water at 90 °C. Catalyst [{(η6-p-cymene)RuCl}2(μ-κ2:κ2-benztetraimd)]2+ [1-Cl] exhibited a remarkably high turnover frequency (1993 h-1 per Ru atom) and long-term stability over 60 days for formic acid dehydrogenation, while the analogous (η6-benzene)diruthenium and mononuclear catalysts displayed low activity with poor long-term stability. Notably, catalyst [1-Cl] also displayed an appreciably high turnover number of 93 200 for the bulk-scale reaction. In addition, the in-depth mass and nuclear magnetic resonance investigations under the catalytic and control experimental conditions revealed the active involvement of several crucial catalytic intermediate species, such as Ru-aqua species [{(η6-p-cymene)Ru(H2O)}2(μ-L)]2+ [1-(OH)], Ru-formato species [{(η6-p-cymene)Ru(HCOO)}2(μ-L)] [1-(HCOO)], and Ru-hydrido species [{(η6-p-cymene)Ru(H)}2(μ-L)] [1-(H)], in the catalytic formic acid dehydrogenation reaction.
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