High-Nuclear Ni-Substituted Poly(polyoxometalate) Containing an Anderson-like {Cs₇} Cluster

Area of Science:

• Inorganic Chemistry
• Materials Science
• Catalysis

Background:

• Polyoxometalates (POMs) are versatile inorganic clusters with diverse structures and applications.
• Developing novel POM architectures with unique structural motifs and enhanced functionalities is an active area of research.
• Alkali metal clusters within POMs are rare, presenting opportunities for new chemical properties.

Purpose of the Study:

• To synthesize and characterize a novel high-nuclear nickel-substituted polyoxometalate (poly(POM)).
• To investigate the unique structural features of the polyoxoanion, particularly the encapsulated cesium cluster.
• To evaluate the catalytic performance of the synthesized poly(POM) in the Knoevenagel condensation reaction.

Main Methods:

• Single-crystal X-ray diffraction for structural characterization.
• Elemental analysis to confirm composition.
• Catalytic testing of the Knoevenagel condensation reaction with various aldehydes and malononitrile.

Main Results:

• Successful synthesis and structural elucidation of a novel Ni-substituted poly(POM), [H2N(CH3)2]2Na18Cs2H13[(Cs7(H2O)6)@{(PO4)-@(Ni4(OH)3(WO4))3@(B-α-PW9O34)3}2]·30H2O (1).
• The polyoxoanion features a unique sandwich structure with a Cs7(H2O)6 cluster core, presenting an Anderson-like arrangement and the first classical POM configuration based on an alkali metal cluster.
• Compound 1 demonstrated good catalytic activity in the Knoevenagel condensation, yielding various products in excellent yields.

Conclusions:

• A novel and complex Ni-substituted poly(POM) with an unprecedented Cs7 cluster core has been successfully synthesized and characterized.
• The unique structural features of this poly(POM) open new avenues in POM chemistry and design.
• The demonstrated catalytic activity highlights the potential of this novel material in organic synthesis, specifically for Knoevenagel condensation.