Manganese complexes with triazenido ligands encapsulated in NaY zeolite as heterogeneous catalysts

Two different methods were described for the preparation of manganese complexes with triazenido derivative ligands encapsulated in NaY zeolite. The catalytic behaviour of the heterogeneous catalysts was evaluated for styrene and cyclohexanol oxidation reactions. Encapsulation was achieved by two methods: (i) ion-exchange from an ethanol solution containing both bis(p-tolyl)triazenido ligand and manganese ions, with the ligand: Mn 3:1 molar ratio (Method A) and (ii) the flexible ligand method (Method B). The heterogeneous catalysts were characterized by FTIR spectroscopy, X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD) and chemical analyses. The results show that both preparation methods lead to effective encapsulation of the Mn{bis(p-tolyl)triazenido} (1:1) complex in the NaY zeolite framework. The heterogeneous catalysts show activity in oxidation of styrene and cyclohexanol with tert-butyl hydroperoxide (tBuOOH) as an oxygen source. The catalysts are chemo-selective in cyclohexanol oxidation, whereas in styrene oxidation reaction leads to styrene oxide and benzaldehyde.

Graphical abstractMn{bis(p-tolyl)triazenido} complex was encapsulated in NaY by flexible ligand and in situ methods. The catalytic behaviour of the heterogeneous catalysts was evaluated in styrene and cyclohexanol oxidation reactions and is active in these reactions. The acidic nature of NaY zeolite plays also a role on styrene oxidation.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Mn complex was encapsulated in NaY by flexible ligand and in situ methods. ► Mn ions is in situ coordinated with bis(p-tolyl)triazenido ligand in NaY. ► Both heterogeneous catalysts are active in oxidation reactions. ► The acidic nature of NaY zeolite plays a role on styrene oxidation.