Ratio-Controlled Precursors of Anderson–Evans Polyoxometalates: Synthesis, Structural Transformation, and Magnetic and Catalytic Properties of a Series of Triol Ligand-Decorated {M₂Mo₆} Clusters (M = Cu²⁺, Co²⁺, Ni²⁺, Zn²⁺)

Abstract

A series of triol ligand [CHC(CHOH)] covalently decorated polyoxometalates (POMs), which could be ascribed to the primary complexes with structural formulas {M[MoO(CHC(CHO))]} (M = Cu, Co, Ni, Zn), have been synthesized in organic solvents. Single-crystal X-ray structural analysis reveals that the synthesized polyanionic clusters are comprised of three {Mo} units and two divalent transition-metal ions connecting to each other in an alternating style, where all {Mo} blocks were covalently decorated by two triol ligands in the trans conformation. The 1/3 molar ratio of M/Mo in the prepared complexes was higher than those ratios in typical Anderson-Evans, Wells-Dawson, and Keggin POMs. With a decrease in the M/Mo molar ratio of a Mo-contained reactant to 1/6 and/or the addition of acetic acid to the reaction solution, the primary complexes acting as precursors transformed continuously into the corresponding triol-ligand-decorated Anderson-Evans POMs. Detailed investigations were conducted by using different isopolymolybdates in various solvent environments, and several Anderson-Evans POMs in different triol-ligand-decorated fashions were obtained from the primary complexes. In addition, we also realized the transformation between the Anderson-Evans clusters in different decoration fashions by simply controlling the acidity in solution. Magnetic measurement showed a general property, but the catalytic experiments demonstrated that Co- and Zn -containing POMs displayed a higher efficiency for the selective oxidation of thioanisole to sulfoxide.

Selective Photooxidation of Amines and Sulfides Triggered by a Superoxide Radical Using a Novel Visible-Light-Responsive Metal–Organic Framework

“…Beyond molecular oxygen, hydrogen peroxide (H 2 O 2 ) has been demonstrated to be an effective oxidant for the catalytic oxygenation of sulfides and it is a benign chemical to the environment. − However, to the best of our knowledge, the use of it in the photocatalytic system of MOFs for the oxidation of sulfides has not been investigated so far. After removal of molecular oxygen by three freeze–pump–thaw cycles, the oxidation of sulfide by H 2 O 2 was first investigated under N 2 atmosphere.…”

Direct Syntheses of Nanocages and Frameworks Based on Anderson-Type Polyoxometalates via One-Pot Reactions

“…Another interesting discovery was that all of the double-sided tris-functionalized Anderson clusters prepared by this “one-pot” protocol were δ/δ isomers, including that with nickel­(II) and copper­(II) heteroatoms. To the best of our knowledge, tris-functionalized Anderson polyoxomolybdates with divalent heteroatoms are usually χ isomers; only a few examples of a single-sided δ isomer or a double-sided χ/δ isomer were reported recently, , while the double-sided δ/δ isomer was never obtained via the literature method. It can be assumed that the χ isomers were kinetically controlled products, while the higher-symmetric δ isomers were thermodynamically controlled products.…”

Copper(ii)-containing tungstotellurates(vi): syntheses, structures and their catalytic performances in selective oxidation of thioethers

“…In recent years, some polyoxometalates (POMs) were used as effective catalysts for the oxidation of thioethers using H 2 O 2 as oxidant. [6][7][8] In those reported procedures, low conversion of thioethers and the service life and reusability of the POM catalysts also need to be further improved. Consequently, based on the above reported results and our previous work on the oxidation of sulphides, 9 We believe that more attractive catalytic systems can be developed along this line to further increase the utility of these thioethers oxidation reactions by using some new stable and recyclable POM catalysts.…”