Discrete spherical hexadecavanadates incorporating a bromide with oxidative bromination activity

Abstract

Two discrete hexadecavanadates, (n-Bu4N)4[V16O38(X)] (X = Cl(-) (1) and X = Br(-) (2)), were synthesized by a reaction of [V10O26](4-) with a template anion resulting in the incorporation of chloride or bromide in the {V16} spherical cluster framework. The reaction of [V10O26](4-) with p-toluenesulfonic acid proceeded under an aerobic environment to give 2 in the presence of an excess amount of bromide anion, which acted as both a template anion and a reducing reagent for the formation of the mixed-valence framework. For the synthesis of cluster 1, additional reductive conditions were required due to the weak reducing ability of the chloride anion. The crystal structures of 1 and 2 were determined using single-crystal X-ray diffraction analysis. Both were found to consist of a discrete [V(V)9V(IV)7O38(X)](4-) framework by the linkage of VO5 pyramidal units. Cyclic voltammetric studies of 1 and 2 in acetonitrile showed a series of stepwise reversible redox processes, which were due to the redox of the spherical polyoxovanadate frameworks. The oxidative bromination reactions of aromatic substrates were also investigated using cluster 2 as a catalyst under aerobic conditions.

Effect of Heterometal‐Functionalization and Template Exchange on the Redox Chemistry of Molecular Vanadium Oxides

“…Similar studies by Hayashi and co-workers [46] on a related [V 16 O 38 X] 4À (= {V 16 X}, with X = Cl -, Br -) showed marked geometric variations between the chloride and bromide species. The cluster size of the chloride analogue is smaller in comparison to the bromide analogue, indicating a stronger interaction between the template and the vanadium atoms.…”

“…Similar observations have been made for related POVs, where synthesis of bromide and chloride analogues was possible, but neither flouride nor iodide analogues could be synthesized. [ 44 , 45 , 46 ]…”

Semimetal-functionalised polyoxovanadates

“…building block exhibited catalytic activity in the oxidative bromination reactions of aromatic substrates under aerobic conditions. 88 The mixed-valent (…”

Functional Enzyme Mimics for Oxidative Halogenation Reactions that Combat Biofilm Formation

“…Organometallic vanadium compounds modeling the structure of the active site of VHPO and peroxo compounds have shown good efficiency and selectivity for different oxidation reactions . Examples are halogenation, decarbonylative halogenation, (enantioselective) sulfoxidation in the absence of halides, epoxidation, hydroxylation of alkenes, and oxidation of primary and secondary alcohols analogous to the native enzyme .…”