Pragati Shringarpure

Synthesis, structural, and spectral characterization of Keggin-type mono cobalt(II)-substituted phosphotungstate

Keggin-type mono Co(II)-substituted phosphotungstate was synthesized from 12-tungstophosphoric acid and cobalt chloride tetrahydrate. The obtained complex was systematically characterized in solution as well as solid by various physicochemical techniques. A single-crystal X-ray analysis shows that the complex crystallizes in tetragonal system, P42/ncm space group with a = b = 20.9860(5) Å, c = 10.4368(3) Å, and Z = 4. The crystal showed two types of disorders related by center of symmetry. Structural studies did not show the presence of Co, but the incorporation of the metal ion was proved by various spectral techniques. Spectral as well as electrochemical studies confirmed the presence of Co(II) into the lacunary position of the phosphotungstate moiety.

Synthesis, characterisation and catalytic activity of non-crystalline organic–inorganic hybrid material comprising Keggin-type manganese(II)-substituted phosphotungstate and salen

A new inorganic–organic hybrid material comprising Keggin-type mono manganese-substituted phosphotungstate and salen was synthesised. The synthesised hybrid material was systematically characterised by various physicochemical techniques such as elemental analysis, thermal gravimetric analysis, FT-IR, UV–vis, electron spin resonane, 1H NMR, 13C MAS NMR and 31P NMR. The catalytic activity was evaluated for non-solvent liquid phase oxidation of styrene using O2. The novelty of the present work lies in obtaining 42% conversion with 41% selectivity for styrene oxide with O2 under solvent-free mild reaction conditions only in 4 h.

Cobalt Substituted Keggin-Type Phosphotungstate, an Efficient Epoxidation Catalyst: Study on Kinetic Behavior as Well as Reaction Mechanism

Keggin type undecatungstophospho(aqua)cobaltate (II) (Cs-PW11Co) was synthesized by one step easy synthesis method and characterized in solution as well as solid by various spectral techniques. The catalytic activity of the isolated complex was evaluated for epoxidation of cis-cyclooctene under ambient temperature and pressure conditions. A detailed kinetic study was carried out for epoxidation of cyclooctene. The energy of activation was also determined from the Arrhenius plot. In the present study, the catalytic system is homogeneous; even then the catalyst was regenerated and reused. The active cobalt hydroperoxo intermediate was characterized in solution by UV-visible and 31P NMR and based upon this study, a probable reaction mechanism was proposed.