Formation of binuclear complexes in the reaction of chromium(II) with hexacyanoferrate(III)

Abstract

The reaction of Cr²⁺ with Fe(CN)₆^3– is rapid at 25°(K > 5 × 10⁶ l. mole^–1 sec.^–1). From the spectra of final solutions two products have been identified both of which are believed to be binuclear complexes. The first [peak at 370 nm. (ε 3090)] is obtained at pH values > 2, and the second [peak at 320 nm. (ε 1980)] at [H⁺] > 1M. The products are more strongly absorbing than the related mononuclear complexes. At intermediate hydrogen-ion concentrations both products are obtained. Because at pH 2 and [H⁺]= 3·0M final spectra do not vary as the temperature is varied (0–25°), it is concluded that outer-sphere reaction paths make no significant contribution. Possible structures for the two binuclear products are considered.