A μ-AsO₄-Bridging Hexadecanuclear Ni-Substituted Polyoxotungstate

Area of Science:

• Inorganic Chemistry
• Materials Science
• Nanotechnology

Background:

• Silicotungstates are versatile polyoxometalates with diverse structures and applications.
• Nickel-substituted polyoxometalates are of interest for catalysis and electrochemistry.
• The synthesis of complex, multi-metal polyoxometalate structures remains a challenge.

Purpose of the Study:

• To synthesize and characterize a novel hexadecanuclear nickel-substituted silicotungstate.
• To investigate the unique structural features of the polyoxoanion, particularly the AsO4 bridging unit.
• To explore the electrochemical and catalytic oxidation properties of the new compound.

Main Methods:

• Synthesis involving trivacant Keggin [A-α-SiW9O34]10- units, Ni2+ cations, and sodium arsenate.
• Characterization using IR spectrometry, elemental analysis, thermogravimetric analysis (TGA), and powder X-ray diffraction (PXRD).
• Electrochemical and catalytic oxidation studies.

Main Results:

• A novel hexadecanuclear Ni-substituted silicotungstate, Na21H10[(AsO4){Ni8(OH)6(H2O)2(CO3)2(A-α-SiW9O34)2}2]·60H2O, was successfully synthesized.
• The structure contains a unique polyoxoanion with a novel AsO4-bridging cluster, linking four Keggin fragments through multiple Ni centers.
• The tetrahedral AsO4 unit acts as an exclusive μ2-bridging ligand, a previously unseen coordination mode in polyoxometalate chemistry.
• Preliminary investigations into its electrochemical and catalytic oxidation properties were conducted.

Conclusions:

• The successful synthesis of this complex silicotungstate demonstrates new possibilities in constructing intricate polyoxometalate architectures.
• The unprecedented AsO4 bridging motif opens new avenues for designing functional inorganic materials.
• The compound shows potential for applications in electrocatalysis and oxidation reactions.