Second sphere coordination in fluoroanion binding: Synthesis, spectroscopic and X-ray structural study of [Co(phen)_2CO_3](Pfbz)·6H2O

摘要

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, multinudear NMR) and solubility product measurement. The complex salt crystallizes in the monoclinic crystal system with space group P2_1 having the cell dimensions a = 13.377(3) A, b= 17.204(3)A, c=15.408(3)A, β = 108.11(3)°, V = 3370.1(12)A~3 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.