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The substitution of bis(2,4,6-tripyridyl 1,3,5triazine)iron(II), Fe(TPTZ) 2þ 2 by 2,2 0 ,6,2 00 -terpyridine (terpy) occurs on a time scale of about 6 m. The kinetics of this reaction was followed by stopped-flow spectrophotometry in the pH range of 3.6-5.6 in acetate buffer. The data indicate that the reaction occurs in two consecutive steps: kinetic data for both steps were acquired simultaneously and analyzed independently. The first step is assigned to the reaction between Fe(TPTZ) 2þ 2 and terpy to give Fe(TPTZ)(terpy) 2? , followed by its reaction with another terpy molecule to give the final product, Fe(terpy) 2þ 2 . The rate of the reaction increases with increases in [terpy] and pH. The kinetic and activation parameters determined for both steps suggest that they involve both associative and dissociative paths. The ternary complex Fe(TPTZ)(terpy) 2? has been prepared, and the kinetics of its reaction with terpy suggest that this reaction is identical with the second step of the Fe(TPTZ) 2þ 2 -terpy system, supporting the proposed mechanism.Electronic supplementary material The online version of this article (

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