Abstract: | A potentially pentadentate hydrazone ligand, N′‐[1‐(pyrazin‐2‐yl)ethylidene]nicotinohydrazide (HL), was prepared from the condensation reaction of nicotinohydrazide and acetylpyrazine. Reactions of HL with MnCl2, Mn(CH3COO)2 and Cd(CH3COO)2 afforded three metal complexes, namely dichlorido{N′‐[1‐(pyrazin‐2‐yl‐κN1)ethylidene]nicotinohydrazide‐κ2N′,O}manganese(II), [MnCl2(C12H11N5O)], (I), bis{N′‐[1‐(pyrazin‐2‐yl‐κN1)ethylidene]nicotinohydrazidato‐κ2N′,O]manganese(II), [Mn(C12H10N5O)2], (II), and poly[[(acetato‐κ2O,O′){μ3‐N′‐[1‐(pyrazin‐2‐yl‐κ2N1:N4)ethylidene]nicotinohydrazidato‐κ3N′,O:N1}cadmium(II)] chloroform disolvate], {[Cd(C12H10N5O)(CH3COO)]·2CHCl3}n, (III), respectively. Complex (I) has a mononuclear structure, the MnII centre adopting a distorted square‐pyramidal coordination. Complex (II) also has a mononuclear structure, with the MnII centre occupying a special position (C2 symmetry) and adopting a distorted octahedral coordination environment, which is defined by two O atoms and four N atoms from two N′‐[1‐(pyrazin‐2‐yl)ethylidene]nicotinohydrazidate (L−) ligands related via a crystallographic twofold axis. Complex (III) features a unique three‐dimensional network with rectangular channels, and the L− ligand also serves as a counter‐anion. The coordination geometry of the CdII centre is pentagonal bipyramidal. This study demonstrates that HL, which can act as either a neutral or a mono‐anionic ligand, is useful in the construction of interesting metal–organic compounds. |