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Komplexone XXVI. Über die Koordinationstendenz von N‐substituierten Iminodiessigsäuren
Author(s) -
Schwarzenbach G.,
Anderegg G.,
Schneider W.,
Senn H.
Publication year - 1955
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19550380509
Subject(s) - chemistry , iminodiacetic acid , metal , chelation , sulfide , medicinal chemistry , sulfur , nitrogen , inorganic chemistry , nitrogen atom , oxygen , ring (chemistry) , group (periodic table) , stereochemistry , organic chemistry
Substituted iminodiacetic acids of the general formula RN(CH 2 ‐COOH) 2 have been synthesized and their coordination tendency with 12 different metal cations investigated. The groups R of the 13 different complexing agents are tabulated on page 1147–1148 of this paper. Most of them carry donor atoms in such a position, that a third chelate ring may be formed when the anion of the iminodiacetic acid combines with the metal. It could be proved that the oxygen, the sulfur and the nitrogen atom of aliphatically bound HO, CH 3 O, HS, CH 3 S, (−) S, NH 2 , (−) OOC, H 2 NCO are actually coordinated in this manner, raising thereby the stability of the metal complex considerably. The carbonamide group coordinates probably by its oxygen atom rather than by its nitrogen atom. The negatively charged mercaptide sulfur is a very powerful donor for the heavy metals and there is a linear relation between the logarithm of the solubility product of the metal sulfide and the logarithm of the stability constant of the metal complex of (−) SCH 2 CH 2 N(CH 2 COO (−) ) 2 . The trimethylammonium group in of course lowers the complex stability, its effect however is much less important than expected. Also the cyano group in NCCH 2 ‐N(CH 2 ‐COO (−) ) 2 weakens the metal binding much less than the addition of the proton to the nitrogen of the iminodiacetate group.