Hexanuclear nickel-substituted silicotungstate as heterogeneous catalyst for construction of benzimidazoles

The development of heterogeneous catalysts is very important for the chemical industry. [Ni0.5(en)] [Ni6(μ3-OH)3(en)3(H2O)6(B-α-SiW9O34)]·3.5H2O (Ni6en, en = ethylenediamine) is one of the representatives of those semi-open Ni6-cluster based polyoxometalates that could be easily synthesized and shows potential catalytic activity in heterogeneous catalytic system. In this work, Ni6en exhibited high stability and excellent catalytic activity in the condensation reaction of aldehydes and o-phenylenediamines at room temperature. A range of benzimidazole compounds could be isolated in good to excellent yields. Furthermore, this heterogeneous catalytic system could be scaled up to gram reaction, and Ni6en could be reused 5 times with no significant decrease in activity, showing its potential application prospect.