Second-sphere coordination in non-spherical anion binding: Synthesis, characterization and X-ray structure of cis-diazidobis(ethylenediamine)cobalt(III) 2-chloro,5-nitrobenzenesulphonate monohydrate

Dark red coloured single crystals of [ cis-Co(en) ₂(N ₃) ₂] C ₆H ₃ClNO ₅S·H ₂O were obtained by slowly mixing the separately dissolved cis-diazidobis(ethylenediamine)cobalt(III) nitrate with sodium 2-chloro,5-nitrobenzenesulphonate in aqueous medium in 1:1 molar ratio. The complex salt was characterized by elemental analyses, spectroscopic studies (IR, UV/visible, ¹H and ¹³C NMR) and solubility measurements. The compound crystallizes in the triclinic space group P1¯ with a = 7.8128(2), b = 8.3219(2), c = 17.4526(2) Å, α = 95.224(1), β = 95.759(1), γ = 116.636(2)°, V = 997.36(5) Å ³, Z = 2. Single crystal X-ray structure determination revealed an ionic structure consisting of [ cis-Co(en) ₂(N ₃) ₂] ⁺, [C ₆H ₃ClNO ₅S] ^- and one lattice water molecule. In the complex cation [ cis-Co(en) ₂(N ₃) ₂] ⁺, the cobalt(III) is bonded to six nitrogen atoms, originating from two ethylenediamine ligands, and two azide groups showing an octahedral geometry around cobalt(III). Supramolecular hydrogen-bonding networks involving second-sphere coordination like [NHen+⋯Xanion-] and NHen+⋯Owater besides electrostatic forces of attraction have been observed to stabilize crystal lattice. This is the first crystal structure of a salt containing 2-chloro,5-nitrobenzenesulphonate anion and cis-diazidobis(ethylenediamine)cobalt(III) cation.