Second sphere coordination in fluoroanion binding: Synthesis, spectroscopic and X-ray structural study of [Co(phen)2CO3](Pfbz)·6H2O

To explore the anion receptor potential of [Co(phen)2(CO)3]+ for the pentafluorobenzoate ion, [Co(phen)2(CO)3](Pfbz)·6H2O (where phen = 1,10-phenanthroline and Pfbz = pentafluorobenzoate) was synthesized by reacting appropriate salts in aqueous medium. A detailed packing analysis has been undertaken to delineate the role of second sphere C–H⋯F interactions amid other heteroatom interactions. The complex salt has been characterized by elemental analyses, spectroscopic studies (IR, UV/Vis, multinuclear NMR) and solubility product measurement. The complex salt crystallizes in the monoclinic crystal system with space group P21/n having the cell dimensions a = 13.377(3) Å, b = 17.204(3) Å, c = 15.408(3) Å, β = 108.11(3)°, V = 3370.1(12) Å3 and Z = 4. Single crystal X-ray structure determination revealed ionic structure consisting of complex cation, [Co(phen)2(CO)3]+, Pfbz anion and six lattice water molecules. In the crystal lattice, discrete ions [Co(phen)2CO3]+ are forming rectangular voids in which the Pfbz anions are entrapped. Crystal lattice is stabilized by electrostatic forces of attraction and hydrogen bonding interactions, i.e. O–H⋯O, C–H⋯O, and C–H⋯F, involving second sphere coordination besides π⋯π interactions.

Graphical abstractAnion receptor potential of [Co(phen)2(CO)3]+ for the pentafluorobenzoate ion has been explored by isolating and characterizing [Co(phen)2(CO)3](Pfbz)·6H2O (where Pfbz = pentafluorobenzoate). Detailed packing analyses reveal that the role of second sphere C–H⋯F interactions is important amid other heteroatom interactions such as O–H⋯O and C–H⋯O and π⋯π for lattice stabilization.Figure optionsDownload full-size imageDownload as PowerPoint slide