Synthese, Crystal Structures, And Characterizations Of Polyoxomatalate Derivatives Based On Hexavacant Dawson Structure And Saturated Keggin Structure

Eight tungstophosphates with wheel-type structure based on hexavacant Dawsonstructure ({P2W₁₂}) have been obtained in aqueous solution by routine synthetic method. Thetransition metal ions (Mn²⁺, Co²⁺, Ni²⁺and W⁶⁺), and carboxyethyltin groups （SnR, R=CH₂CH₂COOH） have been introduced into the skeletons of these polyoxometalate （POM）anions by balancing control. Two organic-inorganic hybrid compounds constructed byKeggin-type polyoxometalates, namely {PM12}（M=W, Mo） and2,2’-biimidazole have beensynthesized under routine synthetic method. All compounds have been characterized by X-raysingle-crystal diffraction, IR spectroscopy, TG analysis, elemental analysis, X-ray powderdiffraction, UV spectroscopy and electrochemical analysis. Their electrocatalytic propertiestoward the reduction of H₂O₂have been investigated by cyclic voltammetry （CV）. At thesame time, some compounds electrocatalytic properties toward the reduction of sodium nitriteand the catalytic oxidation of cyclohexanol to cyclohexanone have been studied.1. Six wheel-type {P₈W₄₈} polyoxometalates have been synthesized by using {P2W₁₂}subunit as a building block, and introducing transition metal ions (Mn²⁺, Co²⁺, Ni²⁺and W⁶⁺)to the hexavacant Dawson structures. The molecular formulas are as follows:Na₂₄[Mn₈（H₂O）₃₂(P₈W₄₈O₁₈₄)]·74H₂O （1）K₄Na₁₆[Co₈（H₂O）₃₂(P₈W₄₈O₁₈₄)]·76H₂O （2）K₄Na₂₀[Ni₈（H₂O）₃₂(P₈W₄₈O₁₈₄)]·72H₂O （3）Na19[Mn₄（H₂O）16Mn₄（H₂O）14(P₈W₄₈O₁₈₄)]·61H₂O （4）K₄Na₁₄[Mn₄（H₂O）₃₂W₃O₉（H₂O）₃(P₈W₄₈O₁₈₄)]·40H₂O （5）K₂Na₁₄[Mn₇（H₂O）₂8Mn3（H₂O）12(P₈W₄₈O₁₈₄)]·41H₂O （6）In compounds1-5, transition metal ions have been filled completely in the inner cavitiesof the wheel-type {P₈W₄₈} POMs. While in compound6, transition metal ions were filledinside and outside of the {P₈W₄₈} anion. In addition, two Mn²⁺were linked together throughone water molecule in compound4. In compound5, four Mn²⁺and three W⁶⁺were filledinside of the wheel-type {P₈W₄₈} anion, which constructed {P8W51} structure.2. One multi（organotin）-decorated wheel-type {P₈W₄₈} polyoxometalates have beenobtained by the reaction of {P2W₁₂} subunit and estertin precursors, and organotin has beenfilled the inner cavity of the {P₈W₄₈} wheel, the molecular formula is:K₄Na₂₄[{Sn（C₃H₄O₂）（H₂O）₂}6(P₈W₄₈O₁₈₄)]·70H₂O （7）3. One new wheel-type {P₈W₄₈} polyoxometalate modified by organometallic and transition metals based on {P2W₁₂} subunit has been synthesized by introducingcarboxyethyltin group and transition metal ions (Mn²⁺) to the {P₈W₄₈} wheel:K₂Na19[{Mn（H₂O）6}6.5{Sn（C₃H₄O₂）（H₂O）₂}(P₈W₄₈O₁₈₄)]·31H₂O （8）4. Two organic-inorganic hybrid compounds have been synthesized by introducing2,2’-biimidazole to the saturated Keggin-type polyoxometalates {PM12}（M=W, Mo）:（H₃（biim）₂）（C₄H₈O₂）₂[PW₁₂O₄₀]·11H₂O （9）（H₃（biim）₂）（C₄H₈O₂）₃[PMo12O₄₀]·3H₂O （10）...