Optically active co-ordination compounds. Part XII. Some mixed complexes of L-amino-acids and ethylenediamine with cobalt(III)

Abstract

Novel features in preparative studies of complexes of the type [Co en₂(AB)]ⁿ⁺ are described, where AB is an L-α-amino-acid. Where AB is L-serine, L-glutamate, L-alanine, or L-threonine, the initial product disproportionates readily to a mixture of trisethylenediaminecobalt(III) ion, and trisaminoacidatocobalt(III). The stereoselectivity of formation of the latter complex of L-threonine is discussed. The complex [Co en₂(glycinate)]²⁺ has been made from glycylglycine by the rapid formation and slow hydrolysis of the glycylglycinatobisethylenediaminecobalt(III) ion. The resolved L-glycinatobisethylenediaminecobalt(III) ion reacts with formaldehyde or acetaldehyde under Knoevenagel conditions to form the L-[(serinato)bisethylenediaminecobalt(III)] ion or the L-[(threoninato)bisethylenediaminecobalt(III)] ion.