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 (S2O3 2-; S4O6 2-; S2O8 2-), 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 Xray 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)2-CO3]Cl.5H2O may be used as an anion receptor for the sulphur oxoanions.