Anion binding through second sphere coordination: Synthesis, characterization and X-ray structures of cationic carbonato bis(1,10-phenanthroline)cobalt(III) complex with sulphur oxoanions

In an effort to utilize the cationic cobalt(III) complex, [carbonato bis(1,10-phenanthroline)cobalt(III)]+ as an binding agent (anion receptor) for the sulphur oxoanions (S2O32-,S4O62-,S2O82-), three complex salts of composition [Co(phen)2CO3] [Co(phen)2(S2O3)]·5·5H2O (1), [Co(phen)2CO3]2S4O6·7H2O (2) and [Co(phen)2CO3]2 S2O8·4H2O (3) were synthesized and characterized by UV/Visible, IR, NMR and conductance measurements. The molecular structure of complex salts 1–3 were determined by single crystal X-ray crystallography which revealed the presence of discrete ions and lattice water molecules in the solid state. A strong network of hydrogen bond interactions through the weak second sphere interactions (C–H···O) and strong interactions of type O–H…O (water) besides the electrostatic interactions play a very important role in stabilizing the crystal lattice. The solubility product measurements, X-ray structure analyses and formation of these salts suggest that cation, [Co(phen)2CO3]+ present in [Co(phen)2CO3]Cl·5H2O may be used as an anion receptor for the sulphur oxoanions S2O32-,S4O62- and S2O82- ions.