Direct and indirect CO2 hydrogenation catalyzed by Ir (III), Rh (III), Ru (II), and Os (II) half-sandwich complexes to generate formates and N, N-diethylformamide Journal of CO2 Utilization, 2020 Item

As a contribution to the valorization of carbon dioxide, new N,O-coordinated Ir(III), Rh(III), Ru(II), and Os(II)<br>half-sandwich complexes have been designed, synthesized, and applied as homogeneous pre-catalysts in the<br>experiments for direct and indirect CO2 hydrogenation under basic conditions. The complexes contain a N,Odonor<br>Schiff base ligand derived from N-(β-naphthyl)-2-oxy-1-naphthaldimine that assisted by partitioning the<br>catalysts to the organic layer in biphasic mixtures, enabling catalyst separation. In the presence of DBU, the Os<br>(II) half-sandwich complex N,O-Os(II) (C2) gave a TON of 889 for [DBUH][HCO2] formation under a partial<br>pressure of 60 bar CO2/H2 at 120 °C over 48 h, assisted by heterogeneous side reactions. Complexes N,O-Rh(III)<br>(C3) and N,O-Ir(III) (C4) exhibited great efficiency in the homogeneous hydrogenation of carbon dioxide to<br>afford formate and N,N-diethylformamide in the presence of DBU and diethylamine, respectively. Group 9 halfsandwich<br>complexes eminently qualify as useful in the direct and indirect hydrogenation of CO2 to afford reaction<br>intermediates that can be used to make carbon-neutral fuel.<br>