Mononuclear discrete complexes and coordination polymers based on metal(ii) chelidonate complexes with aromatic N,N-chelating ligands

Abstract

The versatile coordination chemistry of the anion chelidonate (chelidonic acid, H₂chel, 4-oxo-4H-pyran-2,6-dicarboxylic acid) allowed for the synthesis of different mixed-ligand complexes with the N,N′-chelating ligands 2,2′-bipyridine and 1,10-phenanthroline. We describe here the synthesis and structural characterization of a series of compounds that illustrate the structural diversity of which 4-oxo-4H-pyran-2,6-dicarboxylate ligands are capable: the 2D coordination polymer [Cu(chel)(bipy)] (1), the 1D coordination polymer [Zn(chel)(bipy)(OH₂)]·1/2H₂O (2), the discrete neutral mononuclear compounds [Zn(chel)(phen)(OH₂)₂] (3) and [M(chel)(phen)(OH₂)₃]·nH₂O, M = Zn and n = 1 (4), M = Ni and n = 2 (5), and the discrete mononuclear cationic complex [Zn(OH₂)₂(phen)₂]chel·3.3H₂O (6). The effects of the weak interactions on the crystal packing were also analyzed. The thermal behaviour of the hydrated compounds was investigated. The study of the magnetic properties of 1 revealed weak antiferromagnetic coupling between the copper(II) centres.