J . A m . Chem. Soc. 1985, 107, 491 1-4915 magnitude greater then K 2.2. For Ru(111)-Co(III), we found log Kpy3.3= 12.4, which is a g u t seven orders of magnitude greater than Kpy3s2.In the case of CoTPP in CH2C12solution,I2 log K l for pyridine binding increase from 2.90 for CoI'TPP to 12.7 for Co'I'TPP. Thus for pyridine binding the oxidation of Ru(I1) has a large effect on the Lewis acidity of Co(I1) and has little effect on Co(III), a t least when compared to Co"'TPP. For I-MeIm binding a t Co(III), on the other hand, conversion of Ru(I1) to Ru(II1) allows the formation of the bis I-MeIm adduct. W e strongly suspect that the effects manifested by the Co(I1) center upon oxidation of Ru(I1) are electrostatic in origin, probably mediated by the bridging chloride. The Ru-C1 bond distance is not expected to shorten drastically upon oxidation (
