Chemistry Reference
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Fig. 7 The Temple of Concordia at Agrigentum. The shape of the pediment provides the simplest
template: the triangle
Fig. 8 Template synthesis of the cobalt(III) sepulchrate complex, [Co
III
(sep)]
3+
.
Step i
complex
formation and oxidation by air;
step ii
Schiff base condensation;
step iii
nucleophilic attack to the
C
¼
N double bond by the deprotonated forms of ammonia
molecules of formaldehyde takes place at the six -NH
2
groups (Fig.
8
, step ii).
Finally, in the presence of base, nucleophilic attacks to the C
N double bonds by the
varying deprotonated forms of the triprotic acid NH
3
occur, which eventually lead to
the formation of the cage (Fig.
8
, step iii). The reaction is unique in that 12 distinct
particles (the metal ion, three en, six HCHO, and two NH
3
) give a well-concerted
sequence of reactions, addressed by the Co
III
template, leading to the formation of an
intrinsically complicated and highly symmetrical molecular system. Inspired by the
solemn, funereal fashion of naming ligands introduced by Lehn (with cryptands and
cryptates), Sargeson christened the octamine cage “sepulchrand” (sep) and its
¼
