The kinetics of the outer-sphere oxidation of Cr (NN) 3Z+ ions (NN= 2, 2'-bipyridine, 1, lO- phenanthroline, and their substituted derivatives) by tris (che1ating ligand) complexes of Co (II1) were studied. The second-order rate constants increase with the driving force of the reaction. The rate constants for Co (en)?+ at 23 f 2" C increase from 2.2 (10.3) X lo3 M-'sl for Cr (bpy) 32+ to 1.1 (f0. 2) X lo5 MI sI for Cr (4, 7-Mez-phen) 32+ and agree very well with ...