Kinetics of aquation of chloro- and thiocyanato-chromium(III) complexes in mixed aqueous solvents

Abstract

Rate constants are reported for spontaneous thermal aquation of the complexes [Cr(NH₃)₅Cl]²⁺, cis-[Cr(en)₂Cl₂]⁺(en = ethylenediamine), trans-[Cr(OH₂)₄Cl₂]⁺, and [Cr(NCS)₆]^3– in a range of solvents, including methanol–, ethanol–, acetone–, dioxan–, and t-butyl alcohol–water binary mixtures. These results, and previously published results on similar chromium (III) complexes, are discussed in terms of the Grunwald–Winstein treatment of solvolyses in mixed aqueous solvents. Although this empirical approach can usefully be employed in discussing the aquation of chlorochromium(III) complexes, its extension to thiocyanatochromium(III) complexes does not seem profitable.