Ethylenediamine complexes macrocyclic ligands from

The earliest example (1) of a synthetic macrocyclic ligand containing an imine linkage was derived from the mixed Schiff base-aldol condensation of acetone with nickel(II) ethylenediamine complexes. In 1964 Curry and Busch reported the iron(II)-templated condensation of 2,6-diacetylpyridine with triethylenetetramine to give iron(III) complexes of the macrocycle (4). This was followed by the observation that the selfcondensation of o-aminobenzaldehyde gave, in the presence of nickel(II) ions, complexes of the macrocyclic ligands (2,3). In all of these examples no macrocycle was obtained in the absence of a metal ion. 

Other complexes with tetraaza macrocycles have been prepared by reaction of [Au(en)2]Cl3, ethylenediamine, or nitroethane and formaldehyde, although with nitroethane an acyclic ligand was also obtained (293).1715,1716 A gold(III) complex with a hexaaza macrocycle (1,8-dimethyl-1,3,6,8,10,13-hexaazacyclotetradecane) has been obtained by a transmetallation reaction from the nickel compound [NiL]2+ by reaction with [AuC14], 1717 The chemistry of tetraazamacrocycles in aqueous solution has been reported.1718... 

The effect of increased alkylation on the stabilities of complexes can be seen readily from the following series of copper complexes containing four ammonias, two ethylenediamines, one 2,3,2-tet, and finally q clam as ligands (6). All complexes are analogous in that four nitrogens are coordinated to the Cu(II) ion, but the effect of increased alkylation on the heat of reaction is seen to be considerable and the macrocyclic effect, which in this case involves 4.7 kcal per mole in going from 2,3,2-tet to cyclam, is seen to largely due to creased alkylation. ""... 

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