Implication of oxidant activation on olefin epoxidation catalysed by Molybdenum catalysts with aroylhydrazonato ligands: Experimental and theoretical studies

Dinuclear and mononuclear molybdenum(VI) complexes with aroylhydrazonato ligands were studied as catalysts for cyclooctene and oct-1-ene epoxidation. Different isomers of the OH and NH2 functionalised aroylhydrazones led to four specific [MoO2L] units showing different catalytic activity. Three oxidants have been investigated: tert-butylhydroperoxide (TBHP) in water or in decane, and hydrogen peroxide (H2O2). Catalytic processes with TBHP in decane provided outstanding results in the case of cyclooctene epoxidation: TOF2.5 min > 9000 with 0.25 mol % [Mo] loading. DFT calculations confirmed the relationship between the ligand nature and reactivity with TBHP and H2O2 as oxidant agents. In the case of TBHP as oxidant, calculations considered the solvent in which the oxidant is delivered to the olefin. A plausible mechanism with H2O2 has been proposed after considering various pathways.

Automated summary

The study investigated the catalytic activity of dinuclear and mononuclear molybdenum(VI) complexes with aroylhydrazonato ligands in the epoxidation of cyclooctene and oct-1-ene. Different isomers of aroylhydrazones led to specific [MoO2L] units with varying catalytic activity, with TBHP in decane providing outstanding results for cyclooctene epoxidation. DFT calculations confirmed the relationship between ligand nature and reactivity with oxidant agents TBHP and H2O2, proposing a plausible mechanism with H2O2 after considering various pathways.