The cobalt(II) salt of the azo dye Orange G.

Crystallizing the cobalt(II) salt of the azo dye Orange G from water was found to give the solvent-separated ion-pair species hexa-aqua-cobalt(II) 7-oxo-8-(2-phenyl-hydrazin-1-ylidene)-7,8-dihydro-naphthalene-1,3-disulfonate tetra-hydrate, Co(H(2)O)(6)·4H(2)O. The asymmetric unit of the cobalt(II) salt contains three independent octa-hedral Co(OH(2))(6) cations, three azo anions, all with similar configurations, and 12 uncoordinated water mol-ecules. The structure is closely related to that of one of the known magnesium analogues. Both structures have Z' = 3, feature nearly planar azo anions [maximum displacement of azo-N atoms from the plane of the phenyl ring = 0.058 (7) Å] in their hydrazone tautomeric form, form layer structures with hydro-philic and hydro-phobic layers alternating along the b-axis direction, and are stabilized by an extensive network of hydrogen bonds..