From copper(II) carboxylate to copper(II) 4-pyridylsulfonate coordination polymers as a consequence of the copper(II)-assisted oxidative cleavage of the 4,4′-dipyridyldisulfide ligand

Abstract

Five coordination polymers 1 {[Cu₄(HCO₂)₆(OH)₂(4dpds)₂]·2CH₂Cl₂}_n, 2 {[Cu₄(CH₃CO₂)₆(OH)₂(4dpds)₂]}_n, 3 {[Cu(4dpds)₂(H₂O)₂](4pySO₃)₂·2H₂O}_n, 4 {[Cu(4pySO₃)₂(4dpds)₂]·2H₂O}_n and 5 {[Cu(4pySO₃)₂(dmso)₂]·2H₂O}_n (where 4dpds = 4,4′-dipyridyldisulfide, 4pySO₃ = 4-pyridylsulfonate) have been obtained during a study into the reactivity of basic copper(II) salts (formate and acetate) with 4,4′-dipyridyldisulfide (4dpds). The coordination polymers 1 and 2 consist of a repeated rhomboid structure in which analogous Cu₄(RCO₂)₆(OH)₂ cores are joined by two 4,4′-dipyridyldisulfide bridging ligands to generate two different chain topologies: planar ribbon in 1 and ruffled ribbon in 2. 4-Pyridylsulfonate ions appear as ligands or counterions in the coordination polymers 3, 4 and 5 due to oxidative cleavage of the 4,4′-dipyridyldisulfide under mild conditions. The coordination polymer 3 has been isolated repeatedly in several direct reactions of the copper(II) carboxylates with 4,4′-dipyridyldisulfide. However, the coordination polymers 4 and 5 have been obtained from 1 and 2, respectively, by recrystallization from DMF and DMSO. In compound 4, as in 3, the 4,4′-dipyridyldisulfide has only been partially oxidized to 4-pyridylsulfonate and a proportion of these units remain in the structure as disulfide. However, in 5 the oxidation is complete. The structural analysis of these coordination polymers reveals that, in all cases, weak interactions such as classical and non-classical hydrogen bonds, as well as CH⋯π, S⋯π and S⋯O interactions, join the polymeric chains to generate three-dimensional networks.