Mixed Carboxylate Ligands Bridging Tetra-Pr³⁺-Encapsulated Antimonotungstate: Syntheses, Structure, and Catalytic Activity for Imidazoles Synthesis

Multinuclear Pr-containing antimonotungstate [Pr₄(H₂O)₁₀W₆O₁₃(mal)₂(OAc)(<i>B-</i>α<i>-</i>SbW₉O₃₃)₄]^21- (<b>Pr-1</b>, mal = malate anion, OAc = acetate anion), bridged by organic carboxylic acid, was synthesized through a one-pot assembly reaction and structurally characterized. <b>Pr-1</b> is composed of four [<i>B-</i>α<i>-</i>SbW₉O₃₃]^9- fragments fused together by an organic-inorganic hybrid central [Pr₄(H₂O)₁₀W₆O₁₃(mal)₂(OAc)]¹⁵⁺ cluster core through 24 μ₂-O atoms. Notably, the central cluster comprises unprecedented decanuclear Pr₄(H₂O)₁₀W₆O₁₃ jointly decorated by two types of carboxylic acid ligands. This integration of rare earth-containing antimonotungstate with mixed organic carboxylate ligands is very rare in POMs chemistry. <b>Pr-1</b> exhibits excellent catalytic activity in the cyclo-condensation reaction involving benzil, aldehyde, and NH₄OAc. A series of 2,4,5-trisubstituted imidazoles were synthesized in remarkable yields using <i>ⁱ</i>PrOH as a green solvent.