Dioxidomolybdenum(VI) complexes chelated with N4-(3-methoxyphenyl)thiosemicarbazone as molybdenum(IV) precursors in oxygen atom transfer process and oxidation of styrene. (1st October 2019)

• Record Type: Journal Article
• Authors: Asha, T.M.; Sithambaresan, M.; Prathapachandra Kurup, M.R.
• Is Part Of: Polyhedron. Volume 171(2019)
• Page Start: 530
• Page End: 541
• Publication Date: 2019-10-01
• Subjects: Dioxidomolybdenum(VI) complex -- Oxo transfer property -- Catalytic proficiency -- Styrene -- Hirshfeld surface analysis; Chemistry, Inorganic -- Periodicals; Chimie inorganique -- Périodiques; Organometaalverbindingen; Anorganische chemie; 546.05
• DOI: 10.1016/j.poly.2019.08.006
• Languages: English
• ISSNs: 0277-5387

Abstract

Graphical abstract: Four new dioxidomolybdenum(VI) complexes of a new thiosemicarbazone were synthesized and characterized. Complexes exhibited oxygen atom transfer towards PPh3 and acts as efficient catalyst for the oxidation of styrene. Abstract: Four new mononuclear dioxidomolybdenum(VI) complexes of the type [MoO2 LD] (where D = methanol (1 ), ethanol (2 ), propanol (3 ) and [MoO2 LD]2 ·D (where D = 4-picoline (4 )) have been synthesized by the reaction of [MoO2 (acac)2 ] with the thiosemicarbazone (H2 L) derived from 3-ethoxy-2-hydroxybenzaldehyde and N 4 -(3-methoxyphenyl)thiosemicarbazone in presence of donor solvents like methanol, ethanol, propanol and 4-picoline. Crystal and molecular structures of the complexes were determined by single crystal X-ray diffraction analysis. All the complexes portrayed similar mononuclear structures where the thiosemicarbazone is bonded to molybdenum(VI) ion as a binegative tridendate agent. The molybdenum(VI) centre in complexes1 –4 is six coordinate by the thiosemicarbazone, two oxido groups and an oxygen or nitrogen atom from the donor solvent molecules. The complexes1 –4 exhibit oxygen atom transfer to PPh3 in acetonitrile medium in presence of NN bidendate donors to form complexes of the form [Mo (IV) OL(NN)] (where NN = 2-2′ bipyridine (5 ) or 1, 10 phenanthroline (6 )). The complexes were further characterized by elemental analysis, spectroscopic methods (IR, UV–Vis and 1 H NMR) and thermogravimetric analysis. The electrochemical behaviour of these complexes have been investigated for an insight into the redox behaviour of the molybdenum(VI) centres in these complexes. Hirshfeld surface analysis was successfully employed for exploring the coordination geometries and various non-covalent interactions present in their crystal structures. Furthermore, the catalytic abilities of1 –4 were tested for the oxidation of styrene using aqueous H2 O2 as oxidant and NaHCO3 as co-catalyst. The reaction condition for all-out catalytic proficiency of the catalysts1 –4 were examined by studying the effect of various parameters such as the amount of catalyst, H2 O2, co-catalyst (NaHCO3 ) and solvent (CH3 CN) as well as temperature of the reaction. Almost 97–98% product selectivity was attained for the oxidation of styrene to styrene oxide.