Synthesis and characterisation of double-layered octahedral coordination polymers built up from divalent metal ions, mixed carboxylate anions, and ethyl carbazate ligands

A new family of mixed formate–acetate containing coordination polymers of formulae M(HCOO)2–x(CH3COO)x(C3H8N2O2) [M = Mn (1), Co (2), Zn (3) and Cd (4)] and Cd(CH3COO)2(C3H8N2O2) (5) (C3H8N2O2 = ethyl carbazate) are described. The compounds have been crystallised from aqueous solution and characterised using elemental analysis, IR and UV/visible spectroscopy, TGA, NMR and PXRD and the single-crystal structures of 1 and 3 have been determined. These isostructural compounds consist of M2+ ions coordinated by N,O-chelating ethyl carbazate molecules and four bridging acetate or formate anions (some of which are disordered). The resulting coordination polyhedra for the metal atoms are distorted MO5N octahedra. The polyhedral connectivity (via both formate and acetate bridges) generates double layers propagating in (100) with the topology of a square grid for the metal … metal links. Intra-layer NH…O hydrogen bonds help to establish the structures.