Polymorphism in an Aqua‐Bridged, Dinuclear 2‐Nitrobenzoate Complex of Cobalt(II)

Three polymorphs of a dinuclear, aqua‐bridged cobalt complex with the composition [Co2(μ‐OH2)(C5H5N)4(μ‐O2CC6H4‐2‐NO2)2(O2CC6H4‐2‐NO2)2] are identified and the crystal structures are determined by X‐ray crystallography. Selective crystallisation of the polymorphs can be achieved by controlling the reaction conditions as well as the crystallisation processes. The reaction of cobalt(II) acetate tetrahydrate with 2‐nitrobenzoic acid followed by treatment with excesspyridine leads to a mononuclear complex with the composition [Co(H2O)2(C5H5N)2(O2CC6H4‐2‐NO2)2]. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)