Second sphere coordination in anion binding: Syntheses, characterization and X-ray structures of [trans-Co(en)2(X)2]Y where X=Cl when Y= IO4 or X=N3 when Y=N3

Green coloured single crystals of [trans-Co(en)2Cl2]IO4 I and dark red coloured single crystals of [trans-Co(en)2(N3)2]N3 II were obtained by slowly mixing stoichiometric quantities of the separately dissolved trans-dichlorobis(ethylenediamine)cobalt(III) chloride with sodium metaperiodate or sodium azide in aqueous medium. Elemental analyses, spectroscopic studies (IR, UV/visible, 1H and 13C NMR) and solubility measurements were performed to characterize the complex salts. The compound I crystallizes in the monoclinic space group P21/c with a=6.3970(2), b=16.6790(4), c=12.3730(3) Å, β=99.148(1)°, V=1303.35(6) Å3, Z=4 and II crystallizes in the orthorhombic space group Pbca with a=10.1790(1), b=13.5350(1), c=17.2410(2) Å, V=2375.34(4) Å3, Z=8. Supramolecular hydrogen bonding networks between ionic groups [ NH en + ⋯ X anion − ] by second sphere coordination besides electrostatic forces of attraction have been observed. Compound II represents the first reported structure of a salt containing the cation, [trans-Co(en)2(N3)2]+.