Cs Salt of Undecatungstophospho(aqua) Cuprate(II): Microwave Synthesis, Characterization, Catalytic and Kinetic Study for Epoxidation of cis‐Cyclooctene with TBHP

Abstract

The present paper describes a facile microwave route for the synthesis of Cesium salt of mono‐copper substituted phosphotungstate, Cs5[PW11Cu(H2O)O39].4H2O, from H3PW12O40, CuCl2 and CsCl, its characterization and catalytic activity towards solvent‐free, selective epoxidation of cis‐cyclooctene using TBHP as the oxidant. In order to confirm the superiority of the microwave technique, the said complex was also synthesized by reflux method and the same studies were carried out. The present complex is found to be sustainable as well as recyclable without any change in % conversion as well as % selectivity towards epoxide. A detailed kinetic study showed an overall second order dependence of the reaction with respect to cyclooctene and TBHP.

Chiral Phosphotungstate Functionalized with (S)-1-Phenylethylamine: Synthesis, Characterization, and Asymmetric Epoxidation of Styrene

“…The 1 H NMR spectrum of PW 11 Cu-S-PEA (Figure 3c) shows a downfield shift with a broad peak at 7.37 ppm of an aromatic proton of S-PEA and a peak at 1.419 ppm of a methyl group proton. This confirms the formation of a N→Cu dative bond, which results in a decrease in the electron 52 indicating the presence of PW 11 in the synthesized complex. In addition, it also shows peaks at 48 and 50°2θ, conforming the presence of copper(II).…”

“…(i) Synthesis of PW 11 Cu: PW 11 Cu was synthesized by the one-pot method reported previously by our group. 52 A total of 2.88 g (1 mmol) of 12-tungstophosphoric acid was dissolved in a minimum amount of water, its pH was adjusted to 4.8 using saturated sodium hydroxide, and the solution was heated to 90 °C for 1 h. A total of 0.17 g (1 mmol) of copper chloride dissolved in water was slowly added to the hot solution, and then the mixture was refluxed for 1.5 h, followed by filtration. Solid cesium chloride (0.5 g) was immediately added, and the resulting greenish-blue precipitates were filtered, dried at room temperature, and designated as PW 11 Cu.…”

Epoxidation of cyclohexene with H2O2 over efficient water‐tolerant heterogeneous catalysts composed of mono‐substituted phosphotungstic acid on co‐functionalized SBA‐15

“…31 P‐MAS NMR spectroscopy was performed to further identify if there is any change in the environment around the phosphorus moiety. The 31 P‐MAS NMR for H 3 PW 12 O 40 exhibited a chemical shift at −15.62 ppm, while that of Co‐POM displayed a chemical shift at −14.01 ppm (Figure a, inset), indicating one W atom had been substituted by one transition metal atom . As seen in Figure (b), SBA‐15 showed anti‐symmetric and symmetric stretching vibration bands located at 1100 (ν as Si‐O‐Si), 810 (ν s Si‐O‐Si) and 460 (δ Si‐O‐Si) cm −1 .…”

Flexible oxidation of styrene using TBHP over zirconia supported mono-copper substituted phosphotungstate

“…46 The This is further conrmed by sharp peaks at 48 degrees 2q attributed to Cu(II). 39 The absence of crystalline peaks in case of PW 11 Cu/ZrO 2 indicates complete dispersion of PW 11 Cu on to the support.…”

“…Thus, FT-IR and FT-Raman conrm that PW 11 Cu remains intact even aer impregnation on to the support.X-band liquid nitrogen temperature ESR spectra of unsupported PW 11 Cu, ZrO 2 and PW 11 Cu/ZrO 2 are presented in Fig.5. PW 11 Cu gives a four line hyperne spectrum with g ¼ 2.0883 and g ¼ 2.4031, typically found in Cu(II) complexes 39. PW 11 Cu/ ZrO 2 retains the hyperne spectrum of PW 11 Cu, indicating that copper remains in 2+ oxidation state and the environment around Cu(II) stays intact even aer impregnation on to the support.…”