Aminocarboxylate Complexes Research Articles

Hydrogen Peroxide Bleaching of Amaranth Catalysed by Nickel(II) Nitrilotriacetic Acid

The complex of NiII with nitrilotriacetic acid (NTA) (but not other aminocarboxylate complexes) autocatalyses the hydrogen peroxide bleaching of amaranth, although the reaction is inhibited by the absence of light or presence of alcohol, suggesting a radical-based mechanism.

Hydrogen Peroxide Bleaching of Amaranth Catalysed by Nickel(II) Nitrilotriacetic Acid

The complex of NiII with nitrilotriacetic acid (NTA) (but not other aminocarboxylate complexes) autocatalyses the hydrogen peroxide bleaching of amaranth, although the reaction is inhibited by the absence of light or presence of alcohol, suggesting a radical-based mechanism.

Asymmetry of inner-sphere reorganization energy for heterogeneous electron transfer

The approach to the calculation of the activation energy of electrochemical charge transfer is considered for systems characterized by asymmetry of inner-sphere reorganization (i.e. by the difference in inner-sphere reorganization energies for direct and reverse reactions). Model calculations are carried out and the region of parameters is evaluated for which the effect is pronounced. A quantum-chemical analysis of inner-sphere reorganization is presented for four cobalt and chromium chelate aminocarboxylate complexes and the corresponding contribution to activation energy is discussed in connection with the difference in rate constants.

Linear free energy relationships and the chemical speciation of amino-carboxylate ligand complexes

ABSTRACTFormation constants for H+, Ba2+, Sr2+, Mg2+, Ca2+, Mn2+, Fe2+, Cd2+, Co2+, Zn2+, Pb2+, Ni2+, La3+, Pr3+, Nd3+, Sm3+, Gd3+, Eu3+, Y3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Yb3+, and Lu3+ with N-methyliminodiacetate(MIDA2-), L-2-(Carboxymethyl)iminodiacetate (CIDA3-), Iminodisuccinate(IDSA4-), and N-carboxymethyliminodisuccinate (MAIDSA5-) complexes are reported either from laboratory determinations using pH potentiometry, or from a detailed literature survey, or from the use of such constants in linear free energy relationships to compute the unpublished constants. The ligands studied form a homologous series of general formula HN—(CH2—C02−)n shown as the four ligands in Figure 1 in which the number of electron donor sites varies from 3 to 6. Such constants are of use in the computer simulation of the chemical speciation of multi-metal, multi-ligand complex systems such as those encountered in detergent scenarios in the environment.

Direct determination of stability constants of lanthanide ion chelates by laser-excited europium(III) luminescence spectroscopy: application to cyclic and acyclic aminocarboxylate complexes

Excitation spectroscopy of the 7 F 0 → 5 D 0 transition of Eu 3+ in the visible has been used to quantitate the complexation of this ion to various chelating carboxylate ligands including 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate (dota). Two methods were employed. The first involves the measurement of conditional stability constants at constant low pH values where hydrogen ions compete with Eu 3+ for the ligand. The second method involves measurement of the concentration of the Eu 3+ –ligand complex as a function of pH in the low pH region. The data are then fitted by an equation which accounts for the multiple equilibria involved (ligand and complex protonation) with the stability constant being a parameter to be fit. For [Eu(dota)] - a log K value of 26.21 ± 0.10 was obtained which falls among a wide range of reported values. The values for the remaining ligands are in excellent accord with literature values. The log K values for complexes of dota were obtained for the entire Ln 3+ ion series by a metal ion competition method. This ligand discriminates effectively against the larger members of this series.

Ligand Structural Effects on the Electrochemistry of Chromium(III) Amino Carboxylate Complexes.

The aqueous electrochemical behavior of 10 Cr(III) complexes with potentially tri- and hexadentate amino carboxylate ligands is reported and is shown to depend on the composition and spatial arrangement of the donor atom set. Complexes with two amine and four carboxylate donors (N(2)O(4)) and two amine, one aquo, and three carboxylate donors (N(2)O(3)O') in which the N atoms are coordinated cis to one another undergo chemically and electrochemically reversible reduction at ca. -1.4 and ca. -1.2 V vs SCE, respectively. However, complexes with a trans-N(2)O(4) donor atom set, as exemplified by Cr(MIDA)(2)(-) (MIDA(2)(-) = N-methyliminodiacetate), undergo quasi-reversible Cr(III/II) reduction at ca. -1.4 V that is followed by a sequence of reactions which establishes an electrochemical square scheme. The chemical reactions in the scheme involve displacement of a bound carboxylate group following reduction to Cr(II) and its reattachment after reoxidation to Cr(III). This mechanistic sequence is analyzed by digital simulation, and values of formal potentials, transfer coefficients, and chemical and electrochemical rate constants are reported for Cr(MIDA)(2)(-) and its N-ethyl homolog. The difference in electrochemical behavior between cis- and trans-N(2)O(4) complexes is attributed to differences in the Jahn-Teller distortions experienced by these structures upon reduction to Cr(II). It is proposed that simultaneous N-Cr-N bond elongation, which is possible only for trans species, leads to greater strain in the facially coordinated N-alkyliminodiacetate ligand and thus increases the barrier to electron transfer and facilitates Cr-carboxylate bond cleavage after reduction.

THE COORDINATION OF AMINOPHOSPHONATES TO CHROMIUM(III)

Abstract Attempts to induce coordination of the amine group in aminophosphonate complexes of chromium(III) were unsuccessful. However, N-phosphonomethylglycine forms a stable complex in which the amine, the carboxylate, and one phosphonate oxygen are coordinated. A similarly coordinated complex of N,N-diphosphonomethylglycine is unstable and reverts to an isomer in which the amine group is free. Several potential reasons for the failure of the amine group to coordinate in aminophosphonates in contrast to analogous aminocarboxylate complexes were explored. Steric factors appear unimportant. Contributing factors are (1) there is a driving force for the transfer of a proton from a phosphonate oxygen to the amine, establishing a preference for oxygen coordination; (2) coordination of the phosphonate end of an aminophosphonate appears to lower the basicity of the amine group much more than carboxylate coordination in an aminocarboxylate; (3) in an aminophosphonate the nitrogen lone pair orbitals lie lower in e...

A half-century of lanthanide aminopolycarboxylates

The evolution in our understanding of the structural features of the lanthanide aminocarboxylate complexes is reviewed with emphasis on thermodynamic, nuclear magnetic resonance, luminescence and kinetic data. Comparison with the azacarboxylate complexes is also included.

The relationship of log Ks of Sm‐153‐aminophosphonate and aminocarboxylate complexes with skeletal uptake in rats

The relationship of log K_s of S_m‐153‐aminophosphonate and aminocarboxylate complexes with skeletal uptake in rats

ChemInform Abstract: Formation and Decomposition of Iron‐Carbon σ‐Bonds in the Reaction of Iron(II)‐Poly(amino carboxylate) Complexes with CO‐ 2 Free Radicals. A Pulse Radiolysis Study

ChemInform Abstract: Formation and Decomposition of Iron‐Carbon σ‐Bonds in the Reaction of Iron(II)‐Poly(amino carboxylate) Complexes with CO‐ 2 Free Radicals. A Pulse Radiolysis Study

Formation and decomposition of iron-carbon .sigma.-bonds in the reaction of iron(II)-poly(amino carboxylate) complexes with CO2-free radicals. A pulse radiolysis study

Etude en solutions aqueuses a pH neutre. Des complexes a liaisons metal-C sont formes comme intermediaires instables. Constantes de stabilite des complexes. Cinetique de formation et de decomposition

Kinetic study of acid dechelation of some vanadium(V)–aminocarboxylate complexes in aqueous solution

Kinetic studies of the acid hydrolysis of vanadium(V) complexes of ethylenediaminetetra-acetic acid (H4edta), ethylenediamine-N,N′-diacetic acid (H2edda), and nitrilotriacetic acid (H3nta) have been carried out by stopped-flow spectrophotometry in aqueous solution (I= 3 mol dm–3, NaClO4). The observed first-order (with respect to chelate) rate constant increases as a hyperbolic-type function with H+ concentration. Discussion of the differences in reactivity of the chelates indicates that the dissociation of the chelate complexes would proceed by a pre-equilibrium step leading to the formation of an intermediate for which the ketonic oxygen of one carboxylate group of the chelate is protonated. This first step is followed by rupture of a metal–oxygen bond, rupture of a metal–nitrogen bond, and then by complete cleavage of the multidentate ligand.

Kinetics of dissociation of magnesium aminocarboxylate complexes

The kinetics of dissociation of magnesium aminocarboxylate complexes of the EDTA type have been examined and the results used to determine the rate constants for formation of the complexes and to find the rate-determining steps in the mechanism. The results indicate that loss of the first water molecule from the hydration sheath of the magnesium ion and formation of the first metal-ligand bond is the rate-determining step.

Aminosulphonic acid complexes of cobalt(III). Preparation and base hydrolysis of cis-chlorobis(1,2-diaminoethane)-amino-alkylsulphonatecobalt(III) chlorides and a comparison with the hydrolysis behaviour of analogous aminoalkylcarboxylate complexes

The aminosulphonic acid complexes cis[Co(en) 2{NH 2(CH 2) nSO − 3}Cl]Cl (n = 1, 2), have been prepared and their hydrolysis in basic solution have been investigated. The aminomethylsulphonate complex (k 2 = 2053 ± 50 dm 3 mol −1 s −, ΔH ≠ = 99 ± 2 kJ mol −, ΔS ≠ = 151 ± 8 J K − mol − at 298.2 K) is 200-fold more reactive towards base hydrolysis than analogous complexes containing unsubstituted alkylamine or aminocarboxyclic acid ligands, a result which has been interpreted in terms of the relative ease of formation of the aminomethylsulphonate conjugate base complex. The sulphonate groups in both cases are ineffective in competing with water for the vacant coordination site in the five coordinate conjugate base intermediate [Co(en) 2{NH(CH 2) nSO − 3}] −. This situation contrasts with that of the carboxylate group in the analogous glycinate complex which in base hydrolysis at pH > 10 yields a product mixture 46% of which is the chelated glycinate complex [Co(en) 2NH 2CH 2CO 2] 2+. Competition by carboxylate is negligible in the longer chain aminocarboxylate complexes.

ChemInform Abstract: STUDY OF THE MECHANISM OF DECOMPLEXATION OF SOME VANADIUM(V), MOLYBDENUM(VI), AND TUNGSTEN(VI) AMINOCARBOXYLATE COMPLEXES

Chemischer InformationsdienstVolume 10, Issue 24 Organoelement Compounds ChemInform Abstract: STUDY OF THE MECHANISM OF DECOMPLEXATION OF SOME VANADIUM(V), MOLYBDENUM(VI), AND TUNGSTEN(VI) AMINOCARBOXYLATE COMPLEXES K. ZARE, K. ZARESearch for more papers by this authorJ. LAGRANGE, J. LAGRANGESearch for more papers by this authorP. LAGRANGE, P. LAGRANGESearch for more papers by this author K. ZARE, K. ZARESearch for more papers by this authorJ. LAGRANGE, J. LAGRANGESearch for more papers by this authorP. LAGRANGE, P. LAGRANGESearch for more papers by this author First published: June 12, 1979 https://doi.org/10.1002/chin.197924290AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume10, Issue24June 12, 1979 RelatedInformation

Study of the mechanism of decomplexation of some vanadium(V), molybdenum(VI), and tungsten(VI) aminocarboxylate complexes

Study of the mechanism of decomplexation of some vanadium(V), molybdenum(VI), and tungsten(VI) aminocarboxylate complexes

Determination and comparison of stability constants of vanadium(V), molybdenum(VI), and tungsten(VI) aminocarboxylate complexes

The solution structure and equilibria of vanadium(V), molybdenum(VI), and tungsten(VI) complexes formed by ethylenediaminetetra-acetic (H4edta), ethylenediamine-NN′-diacetic (H2edda), nitrilotriacetic (H3nta), and iminodiacetic (H2ida) acids have been investigated potentiometrically and spectrophotometrically. If Yn– represents the fully dissociated ligand anion, all the 1 : 1 complexes have the formula [VO2Y](n–1)–, [MoO3Y]n–, and [WO3Y]n–. A 1 : 2 vanadium(V)-ida, a 2 : 1 molybdenum(VI)- or tungsten(VI)–edta and two protonated 1 : 1 vanadium(V)–edta chelate complexes are also formed. The formation constants of the 1 : 1 complexes increase with the number of chelate rings for the same metal and decrease from VV to MoVI and WVI for a given ligand. The oxometal ions have a greater affinity for the nitrogen of the amine function than for the acetate oxygen.

ChemInform Abstract: KINETICS OF REPLACEMENT OF AMINOCARBOXYLATES BY MACROCYCLIC POLYAMINES IN COPPER(II) COMPLEXES

The rate constants have been determined for the reaction of macrocyclic polyamine ligands and their protonated forms with [Cu(ida)], [Cu(nta)]–, [Cu(hedta)]–, and [Cu(edta)]2–[ida = iminodiacetate, nta = nitrilotriacetate, hedta =N-(2-hydroxyethyl)ethylenediamine-NN′N′-triacetate, and edta = ethylenediaminetetra-acetate]. The macrocyclic ligands include 1,4,7,10-tetra-azacyclotridecane, 1,4,8,12-tetra-azacyclopentadecane, and 1,4,7,10,13- penta-azacyclopentadecane. These ligand-displacement reactions demonstrate the effects of protonation of macrocyclic polyamines having different ring sizes and denticities. The formation of the macrocyclic complex from [Cu(ida)] or [Cu(nta)] occurs as fast as (or sometimes even faster) from Cu2+(aq), despite the fact that the former reactions require the replacement of strongly co-ordinated aminocarboxylate ligands. The reaction rates for the unprotonated or protonated macrocycles are inversely dependent on the stability constants of the aminocarboxylate complexes, suggesting that the rate-determining step is rupture of the ida segment of an aminocarboxylate from copper. Compared with the same replacement reactions with corresponding linear polyamines, the rate constants are consistently 103—104 times smaller, indicating a close parallel in the two reaction mechanisms.

Kinetics of replacement of aminocarboxylates by macrocyclic polyamines in copper(II) complexes

The rate constants have been determined for the reaction of macrocyclic polyamine ligands and their protonated forms with [Cu(ida)], [Cu(nta)]–, [Cu(hedta)]–, and [Cu(edta)]2–[ida = iminodiacetate, nta = nitrilotriacetate, hedta =N-(2-hydroxyethyl)ethylenediamine-NN′N′-triacetate, and edta = ethylenediaminetetra-acetate]. The macrocyclic ligands include 1,4,7,10-tetra-azacyclotridecane, 1,4,8,12-tetra-azacyclopentadecane, and 1,4,7,10,13- penta-azacyclopentadecane. These ligand-displacement reactions demonstrate the effects of protonation of macrocyclic polyamines having different ring sizes and denticities. The formation of the macrocyclic complex from [Cu(ida)] or [Cu(nta)] occurs as fast as (or sometimes even faster) from Cu2+(aq), despite the fact that the former reactions require the replacement of strongly co-ordinated aminocarboxylate ligands. The reaction rates for the unprotonated or protonated macrocycles are inversely dependent on the stability constants of the aminocarboxylate complexes, suggesting that the rate-determining step is rupture of the ida segment of an aminocarboxylate from copper. Compared with the same replacement reactions with corresponding linear polyamines, the rate constants are consistently 103—104 times smaller, indicating a close parallel in the two reaction mechanisms.

Structure and stability of carboxylate complexes. Part XIII. Crystal and molecular structure of aquobis(NN′-dimethylglycinato)copper(II) dihydrate

The crystal and molecular structure of the title compound (orthorhombic, a= 7·05 ± 0·01, b= 31·7 ± 0·05, c= 6·51 ± 0·01 Å, space group P212121 visual data, 1111 independent reflections) has been determined by three-dimensional X-ray methods and refined by least squares to R 0·12. The copper atom is five-co-ordinate; a square-based pyramid with the ligand water molecule at the apex (mean Cu–N 2·05, Cu–O 1·97; Cu–OH2 2·28 Å) and the basal ligands in the trans-configuration. The structural relationship between this and similar simple copper aminocarboxylate complexes is discussed.