Kinetics of Electron-transfer Reactions Involving Ethylenediaminetetra- acetatochromate(II) Ions as Reductants. I. Reactions with Some Isothiocyanatoammine Complexes of Chromium(III)

Abstract

Abstract Kinetics of electron-transfer reactions of ethylenediaminetetraacetatochromate(II) ions with some isothiocyanatoammine complexes of chromium (III), Cr(NCS)n(NH3)6−n(3−n)+(n=0, 1,4 and 6) have been studied. The former ions are present in the forms of both CrII(H2O)edta2− and CrII(H2O)Hedta−, but the reaction of CrII(H2O)Hedta− with Cr(NCS)n(NH3)6−n(3−n)+ is not significant in the pH range from 3.6 to 5.3. Second-order rate constants (l mol−1sec−1) of the reactions between CrII(H2O)edta2− and Cr(NCS)n(NH3)6−n(3−n)+ at ionic strength 1.0 and 25°C are <10−2 Cr(NH3)63+, 0.2 for CrNCS(NH3)52+, 2.3 for Cr(NCS)4(NH3)2−, and 28.2 for Cr(NCS)63−.