Binding of fluoroanions by a cationic cobalt(III) complex: Syntheses, characterization and single crystal X-ray structure determination of [Co(phen)2CO3]BF4 and [Co(phen)2CO3]PF6·3H2O

In an effort to utilize the cationic cobalt(III) complex as a binding agent for fluoroanions, the reaction of carbonatobis(1,10-phenanthroline)cobalt(III) chloride with sodium tetrafluoroborate and sodium hexafluorophosphate in water (1:1 M ratio) leads to the formation of [Co(phen)2CO3]BF4 (1) and [Co(phen)2CO3]PF6·3H2O (2). These cobalt(III) complex salts have been characterized by elemental analyses, spectroscopic techniques (multinuclear NMR, UV/Visible and FT-IR), solubility product and conductance measurements. X-ray structure determination of these complex salts revealed the presence of ionic structures i.e., one complex cation [Co(phen)2CO3]+ and one BF4- anion in 1 and one complex cation [Co(phen)2CO3]+, one PF6- anion and three water molecules of crystallisation in 2. The packings in both complex salts are stabilized by CH⋯F, CH⋯O(carbonato) hydrogen bonds and anion⋯π interactions beside electrostatic forces of attraction. In addition to these non-covalent interactions, OH⋯O(water) and π–π stacking interactions are also observed in 2. The formation of complex salts of definite composition with tetrafluoroborate and hexafluorophosphate ions suggest that [Co(phen)2CO3]+ may be used as binding agent for weakly coordinating fluoroanions i.e. BF4- and PF6-.