Synthesis, characterization and crystal structure of a dioxomolybdenum(VI) complex with a N,O type bidentate Schiff base ligand as a catalyst for homogeneous oxidation of olefins

The synthesis of a Mo(VI) Schiff base complex, cis-[MoO2{(4,6-bis(tert-butyl)-2-{(benzyl)iminomethyl}phenolate)2}], cis-[MoO2(L)2] where L = 4,6-bis(tert-butyl)-2-{(benzyl)iminomethyl}phenol, derived from benzylamine and 3,5-di-tert-butylsalycilaldehyde is reported. Full characterization of this complex was accomplished with elemental analyses, spectroscopic studies (NMR, IR and electronic) and X-ray structure analysis. This complex was tested as a catalyst for the homogeneous oxidation of olefins. The Mo(VI) complex is catalytically active for the epoxidation of aliphatic substrates at 80 °C, yielding the epoxide as the sole product in yields up to 100% and turnover numbers up to 5000. Under the optimized conditions styrene was oxidized in an 81% conversion to produce styrene oxide, benzaldehyde, and acetophenone.

Graphical abstractA new complex of molybdenum with 4,6-bis(tert-butyl)-2-{(benzyl)iminomethyl}phenol ligand has been synthesized and characterized using elemental analyses, spectroscopic studies (NMR, IR and electronic) and X-ray structure analysis. The cis-[MoO2(L)2] complex, in combination with tert-butyl hydrogen peroxide (TBHP), shows efficient catalytic activity for the homogeneous epoxidation of various aliphatic olefins at 80 °C, yielding epoxide as the sole product in up to 100% conversion and with a turnover number of up to 5000.Figure optionsDownload full-size imageDownload as PowerPoint slide