Second sphere coordination in anion binding: Synthesis, spectroscopic and X-ray structural study of [Co(phen)3]2[Hg(SCN)4]3·3H2O

The complex salt [Co(phen)3]2[Hg(SCN)4]3·3H2O was synthesized by mixing the separately dissolved tris(1,10-phenanthroline)cobalt(III) chloride, mercury(II) chloride and ammonium thiocyanate in aqueous medium in 2:3:12 molar ratio. The newly synthesized complex salt was characterized by elemental analyses, spectroscopic studies (IR, 1H, 13C and 59Co NMR). Single-crystal X-ray structure determination of [Co(phen)3]2[Hg(SCN)4]3·3H2O revealed that the complex salt crystallizes in the monoclinic crystal system with space group P21/n where a = 12.0150(4), b = 20.1916(5), c = 36.1151(9) Å, β = 94.408(2)°, V = 8735.7(4) Å3, Z = 4. The asymmetric unit consists of two complex cations, three anions and three lattice water molecules. Crystal lattice is stabilized by hydrogen bonding interactions of type C-H…O, C-H…N through second sphere coordination and O-H…O interactions besides the electrostatic forces of attraction. The structural studies suggest that [Co(phen)3]3+ is a potential anion receptor for the [Hg(SCN)4]2− ion.