Crystal structure of tris-µ-[2,5-di(2-pyridyl)-3,4-diazahexa-2,4-diene]-dicobalt(II) di[aquotrichlorozincate(II)] tetrachlorozincate(II) tetrahydrate: a helical binuclear cobalt(II) cation

Abstract

Crystals of the title compound are monoclinic, space group P2₁/n, a= 11·47(2), b= 26·88(4), c= 19·89(3)Å, β= 98·57(8)°, Z= 4. The structure was solved by direct methods from diffractometer data, and refined to R 0·082 for 1489 unique observed reflexions. The cation possesses approximately D₃ symmetry; the two cobalt atoms are linked by a helical arrangement of the three quadridentate ligands so that there are three Co–N–N–Co bridges, with Co ⋯ Co 3·81 Å. The ligands are twisted about their N–N bonds, probably a result of intraligand methyl–methyl repulsions. Each cobalt atom is co-ordinated by a trigonal prism of six nitrogen atoms, which has been twisted by 17·5° from octahedral geometry.