Synthesis and Structural Characterization of [Na2M(C5O5)2(H2O)2]·4H2O (M = NiII, CuII)

In this work, the anionic building blocks [M(C5O5)2(H2O2)2]2- (M = Ni, Cu) are synthesized easily, and their structures are unique and interesting in the coordination chemistry of croconate ligand (C5O52-) with the first transition metal. The [M(C5O5)2(H2O2)2]2- moieties act as a dianionic template, and sodium acts as interconnecting cations to build up a three-dimensional framework.