Complexes of cis-dioxomolybdenum(VI) and oxovanadium(IV) with a tridentate ONS donor ligand: Synthesis, spectroscopic properties, X-ray crystal structure and catalytic activity

• Synthesis of new cis-dioxomolybdenum(VI) and oxovanadium(IV) complexes with a tridentate ONS-donor ligand.
• Spectral and electrochemical characterization of the synthesized compounds.
• X-ray crystal structure for one of the complexes as a typical example.
• Reactivity of some complexes as catalytic oxidants for alcohols.

New cis-dioxomolybdenum(VI) and oxovanadium(IV) complexes of the Schiff base, derived from S-methyl dithiocarbazate and 2,3-dihydroxybenzaldehyde (H2dhsm), have been synthesized. The complexes of the type cis-[MoO2(dhsm)] (1a), cis-[MoO2(dhsm)(D)] (1b–1d) [D = neutral monodentate ligand; EtOH, pyridine (py) or imidazole (imz)], [VO(dhsm)(NN)] (2a, 2b) [NN = 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen)] and [VO(dhsm)] (2c) have been isolated, characterized by 1H NMR, IR, UV–Vis and EPR spectral studies and investigated by cyclic voltammetry. The X-ray crystal structure of cis-[MoO2(dhsm)(EtOH)] (1b) has been determined and shows that the complex has a distorted octahedral geometry in which the H2dhsm behaves as a dianionic ONS tridentate ligand coordinating via phenoxide oxygen, hydrazinic nitrogen and thiolate sulfur. The oxomolybdenum(IV) complex [MoO(dhsm)] (1e) has obtained from dioxomolybdenum(VI) complex (1b) by oxo abstraction with PPh3. The reactivity of the complexes toward catalytic oxidation of alcohols in the presence of H2O2 and t-BuOOH as co-oxidants under solvent free conditions is reported.

Cis-dioxomolybdenum(VI) and oxovanadium(VI) complexes with the Schiff base ligand, H2dhsm have been prepared and characterized by spectroscopic and electrochemical studies. The X-ray structure of cis-[MoO2(dhsm)(EtOH)] (shown below) indicates that the (dhsm)2− behaves as a dianionic ONS tridentate ligand. Some of the complexes act as catalysts toward alcohol oxidations in the presence of H2O2 or t-BuOOH.Figure optionsDownload as PowerPoint slide