Hydrogenation of carbon dioxide to formate bya-diimine RuII,RhIII,IrIIIcomplexes as catalyst precursors

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Elsevier B.V
The conversion of CO2into valuable chemicals has been of major interest because it is cheap and readilyavailable. The concept of reducing CO2pollutionviaits utilization into valuable products has inspired usto synthesise novel 4,4'-((1Z)-butane-2,3-diylidenebis(azanylylidene))dibenzoic acid (L) metal com-plexes {[(L)RuII](C1), [(L)RhIII](C2), [(L]IrIII(C3)} complexes for catalytic hydrogenation of CO2. Thea-diimine metal complexes (C1eC3) were characterised using several analytical techniques, including:NMR spectroscopy and single crystal X-ray crystallography. In a mixture of THF/H2O and a base, all threecatalyst precursors were able to hydrogenate CO2cleanly to formate as a product. However, the bestcombination of catalyst precursor and a base wasC1and DBU that selectively produced formate at amoderate temperature of 120 C and at 60 bar. The best productivity under these conditions is TOF of 35h 1within 2 h and a TON of 322. This work is significant because it provides a one-step synthesis forformate from CO2usinga-diimine-based complexes which can be synthesised in a one-step reaction. Thedensity functional theory calculations onC1supports that RueH is the active species in the process ofCO2hydrogenation to formate with the insertion of the CO2to RueH being the rate determining step.
An article published by Elsevier B.V and also available at https://doi.org/10.1016/j.jorganchem.2019.120892
CO2hydrogenation, Homogeneous catalysis, a-diimine complexes, Mechanistic studies, DFT calculations
N. Makuve et al. / Journal of Organometallic Chemistry 899 (2019) 120892, Hydrogenation of carbon dioxide to formate bya-diimine RuII,RhIII,IrIIIcomplexes as catalyst precursors, doi.org/10.1016/j.jorganchem.2019.1208920022