Clathrochelates based on 1,2- and 1,3-diaminoalkanes

Generally, the two main template strategies exploited are sides + caps and caps + sides [5], of which the first is used more extensively. Thus the cage-like systems L824 and L825 (Eq. 4.1) are isolated in 40-90% yield by reaction of ethane-1,2-diamine complexes containing these metals with formaldehyde and ammonia or nitromethane [6-11]. 

Several reports on X-ray diffraction studies of cobalt(III) complexes of L824 and L825 are available [12-17]. 

In particular, [Co(L828)] + is likely to arise from the crossed-Cannizzaro reaction (Eq. 4.4) [8]. 

the role of cobalt(III) as template is associated with control of the behaviour of iminium ion by the activation of an imine to nucleophilic attack as a result of its coordination to the central ion [3]. 

The high regiospecificity of the template encapsulation reaction should be noted. Eleven molecules (three en, six HCHO, and two NH3 or two CH5NO2) participate in the formation of the chelate rings of the final macrocyclic product. In the absence of a matrix a cage-like molecule is believed to be formed in 0.1% yield at best [10], Moreover, if a chiral octahedral (Table 4-1) ethane-1,2-diamine 

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