Three phenanthroline–metal complexes with topologically similar but geometrically different conformations

Abstract

The structures of three related complexes of general formulaM(pds)(nab)2[pdsis the peroxodisulfate anion andnabis an nitrogen-containing aromatic base],viz. bis(2,9-dimethyl-1,10-phenanthroline-κ2N,N′)(peroxodisulfato-κ2O,O′)cadmium, [Cd(S2O8)(C14H12N2)2], (V), bis(3,4,7,8-tetramethy-1,10-phenanthroline-κ2N,N′)(peroxodisulfato-κ2O,O′)zinc, [Zn(S2O8)(C16H16N2)2], (VI), and bis(3,4,7,8-tetramethy-1,10-phenanthroline-κ2N,N′)(peroxodisulfato-κ2O,O′)cadmium, [Cd(S2O8)(C16H16N2)2], (VII), present the same topological coordination, with three chelating ligands in anMN4O2polyhedron. The main difference resides in the fact that the first two complexes are bisected by a crystallographic twofold axis, thus providing a symmetrical environment to the cation, while in the third one this symmetry is disrupted into a clearly unsymmetrical disposition, probably by way of an unusually strong intramolecular C—H...O hydrogen bond. The situation is compared with similar interactions in the literature. The structure of (V) is based on a redetermination in the correct space groupC2/cof the structure originally described in theCcspace group [Harveyet al.(2001).Aust. J. Chem.54, 307–311; Marsh (2004).Acta Cryst.B60, 252–253].