Synthesis, crystal structure and DFT studies of a new dioxomolybdenum(VI) Schiff base complex as an olefin epoxidation catalyst

A cis-dioxomolybdenum(VI) complex was prepared from Mo(acac)2 and a Schiff base ligand derived from 2-hydroxy-1-naphthaldehyde (Naph) and l-histidine (His) in ethanol and was designated as MoO2(Naph-His). Characterization of MoO2(Naph-His) was carried out by means of elemental analysis, 1H NMR, 13C NMR, FT-IR, UV–Vis and TGA techniques. The crystal structure of MoO2(Naph-His), determined by single-crystal X-ray crystallography, revealed that the coordination of Mo in the complex is a distorted octahedron, formed by a tetradentate Naph-His Schiff base ligand and two binding oxygen atoms. The optimized geometrical parameters obtained by DFT calculations are in good agreement with the single XRD data. It was found that MoO2(Naph-His) successfully catalyzes the epoxidation of cyclooctene, cyclohexene and norbornene with 80–100% conversions and 54–100% selectivities. Based on the obtained results, the heterogeneity and reusability of the catalyst seems promising.

Graphical abstractThe synthesis, characterization, crystal structural and DFT studies of a new Mo complex using Mo(acac)2 and a Schiff base ligand derived from 2-hydroxy-1-naphthaldehyde and l-histidine in ethanol and its usage as an epoxidation catalyst are presented.Figure optionsDownload full-size imageDownload as PowerPoint slide