The multinuclear cobaloxime complexes-based catalysts for direct synthesis of cyclic carbonate from of epichlorohydrin using carbon dioxide: Synthesis and characterization

•The three type of cobaloximes have been synthesized and characterized.•The cobaloximes were used for insertion of carbon dioxide into epoxides.•4-(Dimethylamino)pyridine (DMAP) was used as a co-catalyst.•Organodicobaloxime displayed the highest catalytic efficiency.•Good activity and selectivity were obtained with epichlorohydrin.

The novel examples of dicobaloxime [(dmgH)2ClCo-(4,4′-bpy)-CoCl(dmgH)2] (1), organodicobaloxime [(dmgH)2PhCH2Co-(4,4′-bpy)-CoCH2Ph(dmgH)2] (2), and the intramolecular hydrogen (O–H⋯O) bridges were replaced Cu(II) containing multinuclear cobaloxime complexes [{dmgCu(NN)}2ClCo-(4,4′-bpy)-CoCl{dmgCu(N—N)}2](ClO4)4 (3–9) were synthesized, characterized and used in direct synthesis cyclic carbonates from carbon dioxide and various epoxides. The dicobaloxime complex (1) was used as precursors for building the intramolecular hydrogen (O–H⋯O) bridges replaced Cu(II) ions containing complexes (3–9). All of compounds have been characterized by 1H and 13C NMR spectra, FT-IR spectra, UV–Vis spectra, elemental analysis, melting point measurements, LC-MS spectra, molar conductivity measurements, and magnetic susceptibility techniques. Among the nine metal complexes, complex (2) (bearing cobalt–carbon bound) displayed the higher catalytic efficient than other complexes (1 and 3–9) under the same catalytic conditions. The intramolecular hydrogen (O–H⋯O) bridges were replaced Cu(II) containing complexes (3–9) that bear the dimethyl glyoximate ligands and linked ligands exhibited much lower catalytic efficiencies as compared with complexes (1) and (2).

Graphical abstractIn this paper, cobaloximes and mixed-metal, Cu–cobaloximes, were synthesized, characterized and used in direct synthesis of cyclic carbonates from CO2 and epoxides. All compounds have been characterized by 1H and 13C spectra, FT-IR spectra, UV–Vis spectra, elemental analysis, melting point measurements, LC-MS spectra, molar conductivity measurements, and magnetic susceptibility techniques.Figure optionsDownload full-size imageDownload as PowerPoint slide