Configurational effects in the reaction of cobalt(I) Schiff-base complexes with alkyl bromides
Abstract
Electrogenerated diasteroisomeric cobalt(I) chelate complexes of quadridentate Schiff bases derived from substituted ethylenediamines and salicylaldehyde react with PrnBr, BunBr, and ButBr at different rates. The difference in the second-order rate constant can be attributed to the various distortions of the cobalt(I) complex in different configurations. The rate-limiting step is independent of the formation of the cobalt–carbon bond and it is proposed that the reaction occurs via an inner-sphere alkyl-bridged electron transfer, with a [CoI(chelate)]–⋯ R+⋯ X– transition state. The reaction is sensitive to purely stereochemical perturbations of the co-ordination sphere of the metal atom.