Synthesis and characterisation of new Schiff base metal complexes and their use as catalysts for olefin cyclopropanation

New transition metal complexes of CoII, CuII, NiII and VIVO with the Schiff base, HL, 3-acetylcoumarin-N(4)-phenylthiosemicarbazone have been prepared. Characterisation of the HL ligand and its complexes is also reported. Mass spectra and NMR assignments for the ligand, using COSY, NOESY homonuclear and HMQC and HMBC heteronuclear correlation techniques were carried out. Electronic and magnetic moments of the complexes indicate that the geometries of the metal centres are either distorted octahedral, square pyramidal, square planar or tetrahedral. The structures are consistent with the IR, UV–Vis, ESR, as well as conductivity and magnetic moments measurements. Cyclopropanation reactions of unactivated olefins by ethyldiazoacetate (EDA) in the presence of LCuIICl as catalyst proceed with excellent TON (up to 9625).

Graphical abstractNew transition metal complexes with the Schiff base 3-acetylcoumarin-N(4)-phenylthiosemicarbazone, HL, have been prepared. Cyclopropanation reactions of unactivated olefins by ethyldiazoacetate (EDA) in the presence of the copper complex, LCuIICl, as catalyst proceed with excellent TON (up to 9625).Figure optionsDownload full-size imageDownload as PowerPoint slide