Closing formaldehyde-ammonia

Closely related to the football ligands are the so-called sepulchrate ligands. One can be formed by the condensation of formaldehyde and ammonia onto the nitrogen atoms of tris(ethylenediamine)cobalt(llI). This results in tris(methylene)amino caps on opposite faces of the coordination octahedron. If the synthesis utilizes one of the (A, A)-enantiomers, the chirality of the complex is retained. Furthermore, the complex may be reduced to the corresponding cobalt(II) cation and reoxidized to co-balt(III) without loss of chirality. This is particularly unusual in that, as we shall see in the following chapter, cobalt(ll) complexes are quite labile in contrast to the stability of cobalt(III) complexes. Once again the extra stability of polydentate complexes is demonstrated. 

Aldimines and ketimines are formed by the reaction of aldehydes and ketones with solutions of primary amines or ammonia, at a hydrogen ion concentration close to the dissociation constant of the amine. With saturated aldehydes (except formaldehyde which shows a more complicated behaviour) and ketones, a well developed wave at about —1-5 V is observed (Fig. 

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