Second sphere interaction in fluoroanion binding: Synthesis, spectroscopic and X-ray structural study of trans-dichlorobis (ethylenediamine) cobalt(III) terafluoroborate

Trans-dichlorobis(ethylenediamine) cobalt(III) terafluoroborate was synthesised and detailed packing analysis was undertaken to delineate the topological complimentarily of [trans-Co(en)(2)Cl-2](+) and BF4- ions by second sphere coordination. The complex was completely characterised by elemental analyses, solubility product measurement and spectroscopic studies (IR, UV-Vis, multinuclear NMR). In the crystal lattice, discrete ions [trans-Co(en)(2)Cl-2](+) and BF4- are arranged in A-B-A-B pattern (in both a and c directions of the lattice) forming columns of anions and cations. Crystal lattice is stabilized by electrostatic forces of attraction and hydrogen bonding interactions, i.e. N-H center dot center dot center dot F- and N-H center dot center dot center dot Cl involving second sphere coordination. It appears that the topological features of [trans-Co(en)(2)Cl-2](+) are conducive for generating second sphere interactions. This strategy may be used as a viable method for the capture of other fluoroanions. (c) 2008 Elsevier B.V. All rights reserved.