乙二胺四亚甲基四苯次瞵酸的合成及其与Cu^(2+)、Zn^(2+)、Ni^(2+)、Cd^(2+)、Co^(2+)络合常数测定

THE STABILITY OF Zn^2+ Cu^2+ Ni^2+ Cd^2+ Co^2+ COMPLEXES WITH ETHYLENEDIAMINE TETRA ( METHYLENEPHENYL PHOSPHINIC ) ACID

本文合成S.O.Grim提出的、以乙二胺为主体骨架的有机磷多合配位休——乙二胺四亚甲基四苯次瞵酸(Ethylenediaminetetra(methylenephenylphosPhinic)Acid),简称EDTPPI。实验方法利用pH滴定,并用计算机处理数据,利用非线性最小二乘法——步长加速法,测定了EDTPPI的加质子常数,及与Cu^(2+)、Zn^(2+)、Ni^(2+)、Cd^(2+)、Co^(2+)的络合常数。

The coordination chemistry of ethylenediamine tetraacelic acid, EDTA, has been expensively investigated. It is highly effective for many cations over a definite pH range. The problem of selectivity and the complex formation in strongly acidic and strongly alkaline media remained unresolved. Considerable interest has been demonstrated in the synthesis and complexing properties of organophosphorus analogues of aminocaiboxylic acids in which the carboxyls have been partly 01 completely replaced by organophosphorus acid groupings. It has been shown that the replacement of acetate groups by methylenephosphonate groups significantly alters the specificity of the chelating agent. Aminocarboxylic Acid Aminomethylenephosphosphonic Acid The phosphonate ion is almost tetrahedral (a distorted tetrahedron) with a threefold symmetry axis. The carboxylate group is planar. The difference in valence angles and bond lengths make it easier for the aminomethylene-phosphonate moiety to form five membered ring than the aminocarboxylate moiety. π-Bonding between the oxygen and phosphorus atoms is weaker than between the oxygen and carbon atoms in the carboxyl group. Thus 1he polarizability of theP-O bonds in the phosphoryl group is greater than that of the C-O bonds in the carboxyl group, the basicity of the amino-group in aminomethylenephosphonic acids is greater than in aminocarboxylic 41 acids. Studies of the deprotonation of polyaminopolymethylenephosphonic acids show that the protons dissociate from the - PO3H2 groups at low pH. With increasing pH, the protons dissociate from the - PO3H- groups. Finally, in the alkaline region, the protons dissociate from the betaine nitrogen atoms. The combination of highly basic nitrogen atoms and polydentate salt leads to their depronation over a wide pH range, which extends the pH range over which complexes can exist. In this paper we study the synthesis and chelating properties of the phosphinic acid analogue of ethylenediamineteraacetic acid, EDTA, where the carboxylic acids have been replaced by - PO2HC6H5 groups. H2NCH2CH2NH2 +4CH2O + 4C8H5P(O)(OH)H [{C6H5(OH)(O)PCH2}2NCH2]2+4H2O EDTPPI An adaption of the Mannich reaction was used to produce ethylenediamine tetra (methylene phenyl phosphinic) acid. The reaction is simple and powder straightforward. The product is a white crystalline powder which melts at 243- 245℃ with decomposition. Anal, calcd. for C30H36O8N2P4: C 53.26; H 5.36; N 4.14. Found; C 53.19; H 5.38; N 4.14. The protonation constants of EDTPPI and its successive stability constanis of Zn2+ , Cu2+ , Ni2+ , Cd2+ Co2+ complexes have been determined at constant ionic strength of 0.1 M KC1. Its nitrogen basicity and metal chelating tendencies are less than, that of EDTA. However, no other phosphinic acid analogues of EDTA have been reported. A novel method is proposed for the calculation of the successive stability constants of this system.