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Metal Complexes with Macrocyclic Ligands, VI. The role of substituents on the complexation rate of transition metal ions with several 1,4,7,10-tetraazacyclotridecanes

✍ Scribed by Willi Steinmann; Thomas A. Kaden

Publisher
John Wiley and Sons
Year
1975
Tongue
German
Weight
870 KB
Volume
58
Category
Article
ISSN
0018-019X

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✦ Synopsis

Abstract

12,12‐Dimethyl‐1,4,7,10‐tetraazacyclotridecane (I), 11,13‐dimethyl‐1,4,7,10‐tetraazacyclotridecane (II), 11,11,13‐trimethyl‐1,4,7,10‐tetraazacyclotridecane (III) and 1,4,7,10,12,12‐hexamethyl‐1,4,7,10‐tetraazacyclotridecane (IV) have been synthesized and their properties are described.

While the Ni^2+^ and Cu^2+^ complexes of I–III have square planar geometries, those of IV are pentacoordinate according to their absorption spectra. Similarly, while the Co^2+^ complex of I is octahedral and readily oxygenated, the analogous complex with IV is pentacoordinate and not sensitive to oxygen.

The rate of complexation of these ligands with Cu^2+^ and Ni^2+^ decreases in the order I > II > III ≫ IV, indicating that the number as well as the position of the methyl groups are important. Finally for Cu^2+^ the formation of the thermodynamic stable end product is slown down by methyl substitution in α‐position to the coordinating nitrogen atoms (ligand II and III) so that an intermediate can be observed, whereas with I Cu^2+^ directly forms the end product.

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