Soyeb Pathan

Synthesis and Crystal Structure of an Oxovanadium(IV) Complex with a Pyrazolone Ligand and Its Use as a Heterogeneous Catalyst for the Oxidation of Styrene under Mild Conditions

1-Phenyl-3-methyl-4-touloyl-5-pyrazolone (ligand) was synthesized and used to prepare an oxovanadium(IV) complex. The complex was characterized by single-crystal X-ray analysis and various spectroscopic techniques. The single-crystal X-ray analysis of the complex shows that the ligands are coordinated in a syn configuration to each other and create a distorted octahedral environment around the metal ion. A heterogeneous catalyst comprising an oxovanadium(IV) complex and hydrous zirconia was synthesized, characterized by various physicochemical techniques, and successfully used for the solvent-free oxidation of styrene. The influence of the reaction parameters (percent loading, molar ratio of the substrate to H(2)O(2), amount of catalyst, and reaction time) was studied. The catalyst was reused three times without any significant loss in the catalytic activity.

Keggin-type cesium salt of first series transition metal-substituted phosphomolybdates: one-pot easy synthesis, structural, and spectral analysis

The Keggin-type cesium salt of transition metal-substituted phosphomolybdates, Cs5[PCo(H2O)Mo11O39] · 6H2O (1) and Cs5[PMn(H2O)Mo11O39] · 6H2O (2), were synthesized from commercially available H3PMo12O40. The compounds were characterized by thermal, structural, and spectroscopic techniques. X-ray structural analysis reveals that, in these isostructural disordered compounds, the transition metal (Co/Mn) and Mo atoms are distributed over 12 positions. The presence of Co/Mn atoms was confirmed by powder XRD, FT-IR, DR-UV-Vis, ESR, and 31P NMR studies.

Keggin type transition metal substituted phosphomolybdates: heterogeneous catalysts for selective aerobic oxidation of alcohols and alkenes under solvent free condition

Environmentally benign oxidation of alcohols and alkenes over transition metal substituted phosphomolybdates with molecular oxygen as an oxidant and TBHP as an initiator was carried out. The influence of different parameters on the conversion as well as the selectivity was investigated. All the catalysts showed good catalytic activity with excellent selectivity for the desired products as well as a higher TON. The system not only catalyzes the reaction but also avoids the use of organic solvents as it was carried out under solvent free conditions. Moreover, the catalysts could be recovered and reused four times without a significant loss in their activity and selectivity. A probable reaction mechanism was also proposed for the oxidation of alcohols and alkenes.

Heck coupling catalyzed by Pd exchanged supported 12-tunstophosphoric acid—an efficient ligand free, low Pd-loading heterogeneous catalyst

A stable, efficient ligand free, low Pd-loading heterogeneous catalyst comprising Palladium and supported 12-tunstophosphoric acid was synthesized and characterized by various physico-chemical techniques. The catalytic performance of this Pd-exchanged supported 12-tunstophosphoric acid was evaluated for the Heck coupling of olefins with halobenzene. A catalytic activity for recycled catalyst was also evaluated under optimized conditions. The results demonstrated that the catalyst was truly heterogeneous, stable and very active under the present reaction conditions, and could be reused up to three cycles without any significant leaching.

Keggin-type lacunary and transition metal substituted polyoxometalates as heterogeneous catalysts: A recent progress

ABSTRACT In this article we discussed synthesis and catalytic applications of heterogeneous catalysts based on lacunary polyoxometalates (LPOMs) and transition metal substituted polyoxometalates (TMSPOMs), however exclusively the focus has been given to the mono LPOMs and mono-TMSPOMs. As the field of supported LPOMs/TMSPOMs is upcoming important field, some aspects about choice of support as well as methods of supporting have also been described. We also include a few of our new research results in order to understand the effect of support and active species as well as choice of organic transformation.

Keggin type mono Ni(II)-substituted phosphomolybdate: a sustainable, homogeneous and reusable catalyst for Suzuki–Miyaura cross-coupling

Keggin type mono Ni(II)-substituted phosphomolybdate was synthesized and characterized by various physico-chemical techniques and used as a catalyst for Suzuki-Miyaura cross-coupling. The influence of different reaction parameters was studied, to get the maximum yield. The novelty of the present work lies in obtaining >97% yield of biphenyl in 14 h under mild reaction conditions. Although the present catalyst is homogeneous, it was regenerated and reused up to two cycles. Results demonstrated that the catalyst was effective and sustainable for cross-coupling of various halobenzenes with phenylboronic acid in aqueous medium.

Keggin-type mono lacunary silicotungstate supported onto zirconia: synthesis, characterization, and esterification reaction

A solid acid catalyst comprising of lacunary silicotungstate and zirconia was synthesized and characterized by physicochemical techniques. Surface morphologies of support and catalyst were studied by scanning electron microscopy. Catalytic properties were evaluated for the esterification of n-butanol with acetic acid. Esterifications of sec-butanol and isobutanol with acetic acid as well as the esterification of n-butanol with different acids such as formic acid and propionic acid were carried out under optimized conditions. Catalytic activities for calcined as well as recycled catalysts were also evaluated for the esterification under optimized condition.

One pot oxidative esterification of benzaldehyde over a supported Cs-salt of mono nickel substituted phosphotungstate

As a cleaner alternative to traditional two steps procedures, the one pot oxidative esterification of benzaldehyde to methyl ester was carried out over a supported Cs salt of mono nickel substituted phosphotungstate (CsPW11Ni). CsPW11Ni was supported on ZrO2 and characterized using various physico-chemical techniques. The influence of reaction parameters, such as molar ratio of substrate to H2O2, amount of catalyst, reaction time, and reaction temperature, on the oxidative esterification reaction was investigated. Moreover, the catalyst could be recovered and reused up to three cycles without significant loss in selectivity. The present heterogeneous catalytic system was found to be efficient not only in terms of activity (63%) but also in selectivity (79%) of the desired product.

Cysteine and N-acetyl cysteine encapsulated mesoporous silica: synthesis, characterization and influence of parameters on in-vitro controlled release

Pro-drug, cysteine loaded mesoporous silica materials with hexagonal (MCM-41) and cubic (MCM-48) geometry were synthesized by incipient wetness and soaking technique. The structure and properties of these synthesized materials were investigated by various physico-chemical techniques such as FT-IR, Nitrogen adsorption-desorption, XRD and TEM. An in-vitro release study of cysteine from these synthesized materials in SBF was carried out under stirring as well as static conditions. Effect of synthesis method as well as effect of geometry of carrier on release profile of drugs was also examined. Based on the obtained results for pro-drug, controlled release of real drug, N-acetyl cysteine was also carried out under optimized conditions. Release results shows that N-acetyl cysteine release was found to be more controlled as compare to that of cysteine from both mesoporous carriers. A study on release mechanism and release kinetics was also carried out using Higuchi model and first order release kinetic model.

Oxidation of Alcohols Catalyzed by Supported Undecamolybdophosphate

Synthesis and stabilization of undecamolybdophosphate (PMo11) as well as its characterization was explained. Also, synthesis and characterization of series of heterogeneous catalysts comprising PMo11 and different supports (ZrO2, Al2O3, MCM-41 and zeolite-Hβ) and their use as heterogeneous catalysts for solvent free oxidation of alcohols with molecular oxygen and TBHP as a radical initiator was described. The influence of different parameters on the conversion as well as the selectivity was investigated on oxidation of benzyl alcohol. Further, oxidation of various alcohols such as cyclopentanol, 1-hexanol and 1-octanol over supported PMo11 was presented under optimized conditions. All the catalysts are found to be efficient especially in achieving higher selective toward desire product and high turnover numbers. Regeneration study showed that the catalysts can be regenerated and reused without any significant loss in the catalytic activity.