Ion Association and Solvation in Dichloromethane of Tetrachloro-and Tetrabromoferrates(III) Compared with Simple Halides

Conductivity measurements are reported in dichloromethane for tetraethylammonium and tetraphenylarsonium salts of tetrachloro-and tetrabromoferrate(III) and halide ions (chiefly chloride and bromide). Analysis of the data in terms of the recent Fuoss equation has given the ion-pair association constants. The experimental values are close to the ones calculated from the electrostatic Fuoss-Eigen equation. The solvent acts as an acceptor by way of forming hydrogen-bonds to the simple halide ions and to a much less extent to the ferrates. Solvation of chloro-and bromoferrates(III) seems to be comparable, as deduced from the association constants and NMR paramagnetic line broadening. The phenyl groups of the tetraphenylarsonium ion seem to give π-interaction with the solvent.