Tantalum(V) or niobium(V) catalyzed oxidation of sulfides with 30% hydrogen peroxide

Hepta-Zr-Incorporated Polyoxometalate Assembly

Driven by the synergistic-directing effect of the lacunary fragments, [B-α-GeW₉O₃₄]^10- and [B-α-GeW₁₁O₃₉]^8-, an unprecedented hepta-Zr-substituted polyoxometalate (POM) assembly K₂Na₆H₁₀(Hpy)₃[SbZr₇O₆(OH)₄(B-α-GeW₉O₃₄)₂(B-α-GeW₁₁O₃₉)₂]·28H₂O (1) was made under hydrothermal condition and structurally characterized. Of which, a unique hepta-Zr cluster, [SbZr₇O₆(OH)₄]¹⁵⁺ core, was built by two trilacunary [B-α-GeW₉O₃₄]^10- fragments and two monolacunary [B-α-GeW₁₁O₃₉]^8- fragments and further arranged in a mode of a vertical cross and formed a pseudo-tetrahedron geometry. Compound 1 features the first Zr₇-cluster-substituted POM. Moreover, 1 is an effective heterogeneous catalyst for the catalytic oxidation of sulfides into the corresponding sulfones with H₂O₂, manifesting distinguished conversion, excellent yield, and desired recyclability.

Synthesis and nano-Pd catalyzed chemoselective oxidation of symmetrical and unsymmetrical sulfides

A highly chemoselective, efficient and nano-Pd catalyzed protocol for the rapid construction of sulfoxides and sulfones via the oxidation of symmetrical and unsymmetrical sulfides using H2O2 as an oxidant has been developed, respectively. The ready availability of starting materials, easy recovery and reutilization of the catalyst, wide substrate scope, and high yields make this protocol an attractive alternative. The process also involves the metal-free and microwave-promoted synthesis of symmetrical diarylsulfides, and FeCl3-mediated preparation of symmetrical diaryldisulfides through the reaction of arenediazonium tetrafluoroborates with Na2S·9H2O as a sulfur source. In addition, unsymmetrical sulfides were generated via the K2CO3-mediated reaction of arenediazonium tetrafluoroborates with symmetrical disulfides.

Fe3O4@BNPs@SiO2–SO3H as a highly chemoselective heterogeneous magnetic nanocatalyst for the oxidation of sulfides to sulfoxides or sulfones

To achieve green chemistry goals and also to reduce the cost of catalysts as well as to avoid producing toxic wastes and show the importance of separation and recycling of catalysts from the reaction medium, in this work, we describe the preparation and characterization of magnetic acidic boehmite nanoparticles as a heterogeneous catalyst, which is called Fe₃O₄@BNPs@SiO₂–SO₃H. This catalyst works efficiently in the selective oxidation of sulfides to sulfoxides or sulfones in the presence of H₂O₂ as a green oxidant. It can easily be separated from the reaction medium by using an external magnet and it was recycled 6 times without loss of magnetic catalytic properties.

To achieve the green chemistry goals and importance of separation and recycling of catalyst from the reaction medium, Fe₃O₄@BNPs@SiO₂–SO₃H is introduced as a novel heterogeneous nanocatalyst for the oxidation of sulfides to sulfoxides or sulfones.

Polymer immobilized tantalum(v)–amino acid complexes as selective and recyclable heterogeneous catalysts for oxidation of olefins and sulfides with aqueous H2O2

Polymer supported peroxotantalate based heterogeneous catalysts served as highly efficient, selective and recyclable catalysts for alkene epoxidation and sulfide oxidation with green oxidant aqueous H₂O₂ under mild reaction conditions.

Alkaline niobates ANbO3 (A = Li, Na, K) as heterogeneous catalysts for dipropyl sulfide oxidation

Alkaline ANbO₃ (A = Li, Na, K) niobates with perovskite type structure were prepared by sol gel method, extensively characterized and evaluated as heterogeneous catalysts for selective oxidation of dipropyl sulfide to its corresponding sulfoxide.

Dirhodium(II)-Catalyzed Sulfide Oxygenations: Catalyst Removal by Coprecipitation with Sulfoxides

The dirhodium(II) carboxylate complex Rh2(esp)2 (esp = α,α,α',α'-tetramethyl-1,3-benzenedipropanoate) was shown to catalyze the sulfoxidation of organic sulfides using tert-butyl hydroperoxide as the oxidant. Due to the unique structure of Rh2(esp)2 and its stable Rh2(II,II) catalyst resting state, the rhodium catalyst is able to precipitate as a Rh2(esp)2-sulfoxide complex following the reaction which makes separation of the catalyst from the products very convenient. The precipitated Rh2(esp)2-sulfoxide complexes could be reused to catalyze sulfide oxygenation reactions without considerable loss of activity. Mechanistic studies suggest that the axial ligands fine-tune the redox potential of the dirhodium(II,II) compounds and determine the predominant catalyst species in the oxidation reaction.

Generating active and non-selective oxidizing species by previous treatment of niobium-doped mesoporous silica with hydrogen peroxide

Active catalysts for oxidation of non-selective organic compounds were produced by doping silica with niobium followed by treatment with hydrogen peroxide.

Peroxoniobium(v)-catalyzed selective oxidation of sulfides with hydrogen peroxide in water: a sustainable approach

Facile and selective transformation of thioethers to the corresponding sulfoxides or sulfones with 30% H₂O₂ has been achieved in an aqueous medium by using peroxoniobium(v) complexes as reusable catalysts.

Niobium(V) chloride catalyzed oxidation of dithioacetals with 30% hydrogen peroxide: a concise preparation of bissulfonylmethylene compounds

The oxidation of dithioacetals with 16 eq of 30% hydrogen peroxide in the presence of 10 mol% niobium(V) chloride at room temperature provides bissulfonylmethylenes in high yields.

Enhancement of epoxidation efficiencies for Ta-SBA15 catalysts. The influence of modification with -EMe3 (E = Si, Ge, Sn) groups

Site-isolated Ta(V) centers were introduced onto the surface of a mesoporous SBA-15 support via the thermolytic molecular precursor method. After thermal treatment under oxygen, the resulting Si-OH and Ta-OH sites of TaSBA15-O(2)were modified with a series of trimethyl group 14 species, Me(3)E-, by treatment with Me(3)E-NMe(2) (E = Si, Ge, Sn) reagents. The resulting surface-modified catalysts (Me(3)E)(cap)TaSBA15 exhibit a significantly increased rate of cyclohexene epoxidation with H(2)O(2) as an oxidant, and provided a decreased amount of allylic oxidation products with respect to the unmodified material, TaSBA15-O(2). The rate of nonproductive H(2)O(2) decomposition, as monitored via (1)H NMR spectroscopy, significantly decreased after the surface modification. The structure of the TaSBA15 catalysts and potential Ta(V) epoxidation intermediates (formed upon treatment of Ta(V) materials with H(2)O(2)) were probed using UV-visible absorbance and diffuse-reflectance UV-visible spectroscopy. A Ta(V)(η(2)-O(2)) intermediate species is proposed for the TaSBA15-O(2), (Me(3)Si)(cap)TaSBA15, and (Me(3)Ge)(cap)TaSBA15 catalysts, while intermediate species for the (Me(3)Sn)(cap)TaSBA15 catalysts could not be characterized.