Second-sphere coordination in anion binding:: Synthesis and characterization of hexaamminecobalt(III) salts [Co(NH3)6](L)3 • 3H2O and [Co(NH3)6] Cl(L)2, L = (CH3)3C6H2SO3 and X-ray structure determination of [Co(NH3)6]Cl(L)2

The reaction of hexaamminecobalt(III) chloride with sodium salt of mesitylenesulphonic acid in aqueous medium (1:3 molar ratio) leads to formation of two products of hexaamminecobalt(111) salts [Co(NH3)(6)](L)(3)(.)3H(2)O and [Co(NH3)(6)]Cl(L)2, L=(CH3)(3)C6HSO3. These cobalt(111) complexes have been characterized by elemental analyses and spectroscopic techniques (e.g. UV/Visible, IR and NMR). Single crystal X-ray structure determination of title complex salt revealed supramolecular hydrogen bonding network between ionic groups (i.e. oxygen atoms of C9H11SO3- and Cl-) and NH groups of coordinated NH3 molecules, i.e. N-(HO-)-O-... and N-(HCl-)-Cl-... interactions resulting in bilayer formation, the bilayers being anchored by Cl- ions. The formation of definite salts of composition [Co(NH3)(6)](L)(3)(.)3H(2)O and [Co(NH3)(6)]Cl(L)(2) and measurement of solubility products suggests that [Co(NH3)(6)](3+) present in [Co(NH3)(6)]Cl-3 is a promising purely inorganic anion binding agent for the weakly coordinating sulphonate anion. (c) 2005 Published by Elsevier B.V.