BASE HYDROLYSIS AND AQUATION OF TRANS-METHYL-SUBSTITUTED ACIDOPENTA-AMMINECOBALT(III) COMPLEXES

Base hydrolysis and aquation of trans-[Co(NH3)(4)(NH2CH3)X](2+) (where X = Cl, Br and NO3) complexes are reported. Both types of reactions a re four to eight times faster than the corresponding reactions for [Co (NH3)(5)X](2+) complexes. The positive activation entropies of the bas e hydrolysis for all the studied trans-[Co(NH3)(4) (NH2CH3)X](2+) ions and the stereochemistry of the hydroxo products are indicative of a d issociative conjugate base, Dcb, mechanism. The steric course of the b ase hydrolysis differs significantly from that of the parent penta-amm ines. For the aquation reactions, the activation enthalpies of the tr ans-methylamine and penta-ammine complexes are similar, while the acti vation entropies are more positive (or less negative) for the former. These results are interpreted in terms of an I-d mechanism.