A new inorganic–organic hybrid material comprising Keggin-type mono manganese-substituted phospho... more 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.
Keggin type Cobalt and Manganese substituted phosphotungstates were synthesized and characterized... more Keggin type Cobalt and Manganese substituted phosphotungstates were synthesized and characterized by various physicochemical techniques. They were efficiently used for liquid phase non-solvent oxidation of styrene under mild reaction conditions. It was found that the catalytic systems are efficient in achieving higher conversions with high turn over numbers (TONs) and are selective towards benzaldehyde (BA). The complexes behaved as homogeneous catalysts under present oxidation conditions and were efficiently regenerated after a simple workup and reused up to two cycles.
The Keggin-type Cs salt of a mono Mn(II)-substituted phosphotungstate (Cs5[PMnW11O39]) was synthe... more The Keggin-type Cs salt of a mono Mn(II)-substituted phosphotungstate (Cs5[PMnW11O39]) was synthesized from H3PW12O40, MnCl2 and CsCl. The complex was characterized in solution as well as in the solid state by spectroscopic, magnetic and electrochemical techniques. The complex crystallized in tetragonal phase. X-ray structural analysis shows two types of disorder in which the Mn and W atoms are distributed over the 12 positions, and the Mn atom could not be distinguished from the 11 W atoms distributed equally over the 12 addenda atoms in the Keggin structure. The catalytic activity of the complex was evaluated for non-aqueous oxidation of styrene using molecular oxygen. The complex gave >99.0% selectivity towards benzaldehyde and could be reused.
Zirconia supported dodecaphosphotungstate and undecaphosphotungstate were successfully used as he... more Zirconia supported dodecaphosphotungstate and undecaphosphotungstate were successfully used as heterogeneous catalysts for the liquid-phase solvent-free oxidation of styrene. A detailed kinetic study was carried out in order to study the effect of removal of one addenda atom from the parent Keggin unit. The supported catalysts were also systematically characterized by various physicochemical techniques to show that the Keggin unit remains intact even after supporting on the support. Thermal studies also indicate that the supported catalysts are stable up to 450 °C. Maximum conversion with a single selective product was obtained after 30 h for the undecaphosphotungstate and after 20 h for dodecaphosphotungstate. The rate constants as well as the activation energy for the reaction were determined. From the values of activation energy derived from the Arrhenius plot, different thermodynamic parameters such as enthalpy and Gibbs free energy were also calculated. From the above studies, supported dodecaphosphotungstate was found to be more active as compared to undecaphosphotungstate.
A new inorganic–organic hybrid material comprising Keggin-type mono manganese-substituted phospho... more 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.
Keggin-type mono Co(II)-substituted phosphotungstate was synthesized from 12-tungstophosphoric ac... more 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.
A new inorganic–organic hybrid material comprising Keggin-type mono manganese-substituted phospho... more 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.
Keggin type Cobalt and Manganese substituted phosphotungstates were synthesized and characterized... more Keggin type Cobalt and Manganese substituted phosphotungstates were synthesized and characterized by various physicochemical techniques. They were efficiently used for liquid phase non-solvent oxidation of styrene under mild reaction conditions. It was found that the catalytic systems are efficient in achieving higher conversions with high turn over numbers (TONs) and are selective towards benzaldehyde (BA). The complexes behaved as homogeneous catalysts under present oxidation conditions and were efficiently regenerated after a simple workup and reused up to two cycles.
The Keggin-type Cs salt of a mono Mn(II)-substituted phosphotungstate (Cs5[PMnW11O39]) was synthe... more The Keggin-type Cs salt of a mono Mn(II)-substituted phosphotungstate (Cs5[PMnW11O39]) was synthesized from H3PW12O40, MnCl2 and CsCl. The complex was characterized in solution as well as in the solid state by spectroscopic, magnetic and electrochemical techniques. The complex crystallized in tetragonal phase. X-ray structural analysis shows two types of disorder in which the Mn and W atoms are distributed over the 12 positions, and the Mn atom could not be distinguished from the 11 W atoms distributed equally over the 12 addenda atoms in the Keggin structure. The catalytic activity of the complex was evaluated for non-aqueous oxidation of styrene using molecular oxygen. The complex gave >99.0% selectivity towards benzaldehyde and could be reused.
Zirconia supported dodecaphosphotungstate and undecaphosphotungstate were successfully used as he... more Zirconia supported dodecaphosphotungstate and undecaphosphotungstate were successfully used as heterogeneous catalysts for the liquid-phase solvent-free oxidation of styrene. A detailed kinetic study was carried out in order to study the effect of removal of one addenda atom from the parent Keggin unit. The supported catalysts were also systematically characterized by various physicochemical techniques to show that the Keggin unit remains intact even after supporting on the support. Thermal studies also indicate that the supported catalysts are stable up to 450 °C. Maximum conversion with a single selective product was obtained after 30 h for the undecaphosphotungstate and after 20 h for dodecaphosphotungstate. The rate constants as well as the activation energy for the reaction were determined. From the values of activation energy derived from the Arrhenius plot, different thermodynamic parameters such as enthalpy and Gibbs free energy were also calculated. From the above studies, supported dodecaphosphotungstate was found to be more active as compared to undecaphosphotungstate.
A new inorganic–organic hybrid material comprising Keggin-type mono manganese-substituted phospho... more 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.
Keggin-type mono Co(II)-substituted phosphotungstate was synthesized from 12-tungstophosphoric ac... more 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.
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