Kinetics and mechanism of acid-induced homolysis of the metal—carbon bond in organocobalt(III) chelates with a tridentate ligand

Kinetics of acid-induced decomposition of the complexes [RCo(7-Me- salen)(en)] + 1 (I), where R = Me, Et and n-Bu, and related equilibria involving protons have been studied. The complexes lose reversibly the diamine ligand at pH of ca. 5–6 to give [RCo(7-Me-salen)(HP42 O) 2 + (II). At much lower pH the latter species undergo fast reversible protonation at the phenolate oxygen to afford [RCo(7-Me-salenH)(H 2 O 2 ] 2+ (III). Both the organometallic intermediates II and III decompose homolytically, the latter being by a factor of 8–400 as reactive as the former. Kinetic data suggest the splitting of the CoC bond to be a rate-limiting step.