Polydentate ligand construction: a re-examination of an intramolecular condensation reaction

Abstract

The intramolecular condensation reaction of coordinated aminoacetaldehyde and 1,4,7,10-tetraazadecane (trien) has been reinvestigated. The structure of the product, an imine-containing cobalt(III) complex, has been corrected, and this, together with the isolation and characterisation of carbinolamine intermediates, has allowed a modified mechanism to be proposed for the reaction. The isolated carbinolamines result from condensation of the aldehyde with the most acidic coordinated amine (trans to the chloride ligand). The carbinolamines are unable to dehydrate to form an imine product until after they have undergone a rearrangement of the coordination sphere to a geometry that will allow a planar imine to form.