Synthesis of coordination compounds with 4′-(carboxymethoxy)-[1,1′-biphenyl]-4-carboxylate ligand and their catalytic activities towards the Knoevenagel condensation and cyanosilylation reactions

Abstract

Eight new transition-based coordination compounds were hydrothermally fabricated using metal chlorides (M = Co(II), Ni(II), Mn(II), Zn(II) and Cd(II)) with main ligand 4′-(carboxymethoxy)-[1,1′-biphenyl]-4-carboxylic acid (H2cbca) as well as coligands (phen: 1,10-phenanthroline; 2,2′-bipy: 2,2′-bipyridine; 4,4′-bipy: 4,4′-bipyridine or dpe: 1,2-di(4-pyridyl)ethane). The successful synthesis obtained one 0D dimer, three 1D and four 2D coordination polymers, were formulated as [Cd(μ3-cbca)(H2O)]n (1), [Zn(μ-cbca)(phen)]n (2), [Mn(μ3-cbca)(phen)(H2O)]n (3), [Cd(μ3-cbca)(2,2′-bipy)]n (4), [Co(µ-cbca)(μ-4,4′-bipy)(H2O)2]n (5), [Co(μ3-cbca)2(μ-dpe)0.5(H2O)]n (6), [Ni2(cbca)2(μ-dpe)(H2O)8] (7), and [Zn(μ3-cbca)(μ-dpe)0.5(H2O)]n (8). Comprehensive characterisations were performed through standard methods. Topological types and catalytic performance of these compounds were researched. Especially, polymer 2 serves as a stable, highly effective, and recyclable heterogeneous catalyst for the Knoevenagel condensation and cyanosilylation of benzaldehydes, giving a high condensation product yields (up to 100 %) under optimized conditions. Various reaction parameters, substrate scope, and catalyst recycling were also studied. The present work explores the application of H2cbca as the flexible dicarboxylate linker for the preparation of functional coordination polymers.

Keywords

• Coordination polymers
• Crystal structures
• Catalysis
• Knoevenagel condensation
• Cyanosilylation