cis-Dioxo-molybdenum(VI) Schiff base complexes: Synthesis, crystal structure and catalytic performance for homogeneous oxidation of olefins

The synthesis of two Mo(VI) tetradentate Schiff base complexes derived from 2,2′-dimethylpropylenediamine and aromatic aldehydes, (MoO2{hnaphnptn} (1) and MoO2{salnptn(3-OMe)2} (2)) is reported. Full characterization of these complexes was accomplished with elemental analyses, spectroscopic studies (1H NMR, IR, and UV–Vis) and X-ray structure analysis. X-ray crystallography studies reveal that these complexes adopt a distorted octahedral six-coordinate configuration formed by tetradentate Schiff base ligand and two binding oxygen atoms. Catalytic performance of the prepared molybdenum complexes for oxidation of different olefins with tert-butyl hydroperoxide was evaluated. These complexes were found to be an efficient and selective catalyst for the homogeneous oxidation of various olefins. MoO2{salnptn(3-OMe)2} with a methoxy groups on the salicylidene ring of the ligand promote the effectiveness of the catalyst.

Graphical abstractTwo Mo(VI) tetradentate Schiff base complexes (MoO2{hnaphnptn} (1) and MoO2{salnptn(3-OMe)2} (2)) have been synthesized and characterized. X-ray crystallography studies reveal that these complexes adopt a distorted octahedral six-coordinate configuration formed by tetradentate Schiff base ligand and two binding oxygen atoms. These complexes catalyzed efficiently the epoxidation of olefins using TBHP, with excellent selectivity in desired reaction times.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Synthesis and crystal structure of two dioxo-Mo(VI) complexes. ► Catalytic oxidation of different olefins using the above complexes as catalyst. ► Excellent selectivity for epoxide formation was observed.