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

Abstract

Multinuclear Pr-containing antimonotungstate [Pr 4 (H 2 O) 10 W 6 O 13 (mal) 2 (OAc)( B- α - SbW 9 O 33 ) 4 ] 21– ( Pr-1, mal = malate anion, OAc = acetate anion), bridged by organic carboxylic acid, was synthesized through a one-pot assembly reaction and structurally characterized. Pr-1 is composed of four [ B- α - SbW 9 O 33 ] 9– fragments fused together by an organic–inorganic hybrid central [Pr 4 (H 2 O) 10 W 6 O 13 (mal) 2 (OAc)] 15+ cluster core through 24 μ 2 -O atoms. Notably, the central cluster comprises unprecedented decanuclear Pr 4 (H 2 O) 10 W 6 O 13 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. Pr-1 exhibits excellent catalytic activity in the cyclo-condensation reaction involving benzil, aldehyde, and NH 4 OAc. A series of 2,4,5-trisubstituted imidazoles were synthesized in remarkable yields using i PrOH as a green solvent.