A tetranuclear Pr–W heterometal cluster-imbedded antimotungstate for the catalytic synthesis of benzimidazoles

Abstract

A novel organic–inorganic Pr–W heterometal cluster-imbedded antimotungstate, [(CH₃)₂NH₂]₄Na_20.5{[(OAc)Pr₄W₆O₁₂(tar)₃](SbW₉O₃₃)₄(H₂O)₁₀}Cl_0.5·ca. 40.3H₂O (Pr-1), was synthesized via a one-step in situ assembly strategy. Pr-1 features a distinctive tetranuclear Pr-based organic–inorganic hybrid structure stabilized by polycarboxylic acid ligands, which efficiently regulate the hydrolysis of Pr³⁺ to facilitate the assembly of Pr–W heterometallic clusters. Notably, this structure includes abundant Lewis acid sites from Pr³⁺, making it highly promising for catalytic applications. Pr-1 has been successfully demonstrated as an environmentally friendly, heterogeneous catalyst in synthesizing benzimidazoles from o-phenylenediamines and benzaldehydes. The high catalytic activity, excellent structural stability, and recyclability over five cycles highlight the potential of Pr-1 as an efficient and sustainable catalyst for N-containing heterocyclic organic synthesis.