Metal Complexes with Macrocyclic Ligands, XVIII. A study of steric effects in the Co2+‐, Ni2+‐ and Cu2+‐complexes with 1‐(2‐aminoethyl)‐ and 1‐(2‐dimethylaminoethyl)‐4,8,11‐trimethyl‐1,4,8,11‐tetraazacyclotetradecane
- 2 November 1983
- journal article
- research article
- Published by Wiley in Helvetica Chimica Acta
- Vol. 66 (7) , 2086-2092
- https://doi.org/10.1002/hlca.19830660719
Abstract
The two macrocycles 1‐(2‐aminoethyl)‐ and 1‐[2‐(dimethylamino)ethyl]‐4, 8, 11‐trimethyl‐1, 4, 8, 11‐tetraazacyclotetradecane, 1 and 2, respectively, and their metal complexes with Co2+, Ni2+ and Cu2+ were prepared. The different spectral properties of the complexes with these two ligands can be rationalized by assuming that, in the case of 1, the amino group of the pendant arm is axially coordinated to the metal ion giving a pentacoordinate structure, whereas the dimethylamino group of 2 cannot bind because of sterical hindrance. This is also corroborated by the observation that the complexes of 2 react with unidentate ligands such as N and SCN− to give ternary species MLX+, whereas those of 1 do not. This indicates that the complexes of 1 have no free coordination site, their coordination sphere being completely saturated by the five N‐atoms of the macrocycle, whereas the complexes of 2 having a vacant site still can add an unidentate ligand.Keywords
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