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Acidity Constants of the Thienyl- and Phenyl-Pyridines and Stability Constants of the Corresponding Copper (II) 1:1 Complexes

✍ Scribed by Helmut Sigel; Hans Wynberg; T. J. van Bergen; Klaus Kahmann

Publisher
John Wiley and Sons
Year
1972
Tongue
German
Weight
254 KB
Volume
55
Category
Article
ISSN
0018-019X

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✦ Synopsis

Abstract

The acidity constants of the six thienyl‐ and the three phenyl‐pyridines, and the stability constants of the corresponding Cu^2+^ 1:1 complexes were determined in aqueous solution (I = 0.1, NaCIO~4~; 25°). The basicity of the pyridyl group is increased by a shift of a thienyl or phenyl group in the order 2 < 3 < 4 and the influence of the 2′‐thienyl group is greater than that of the 3′‐thienyl group. The stability of the Cu^2+^ 1:1 complexes formed with 3‐ and 4‐substituted pyridines is only dependent on their basicity, as is commonly observed for structurally related ligands and their complexes. Due to steric hindrance the complexes of the 2‐substituted derivatives are less stable by about 1.5 log units. There is no evidence that the aromatic bonded sulfur of 2‐(2′‐thienyl)‐pyridine participates in complex formation with Cu^2+^, in opposition to an earlier claim [1].

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