Stability Constants of Some Macrocyclic Complexes of Ag(I) and Cu(II) in Mixed Solvents by Potentiometry

Stability constants of complexes of Ag(I) and Cu(II) perchlorates and nitrates with some macrocyclic compounds in 90 and 75% (v/v) DMSO+water and 75% (v/v) DMF+water media have been determined by potentiometry. Silver and copper wires, and Coated Wire Ion Selective Electrodes (CWISE) were used as indicator electrodes. It was observed that complexation is stronger when the salt is present as a perchlorate than when it is as a nitrate. For both cations the stability constant values in 75% (v/v) DMF+water were somewhat higher than in 75% (v/v) DMSO. The macrocyclic effect due to cyclization of linear amine tosylates has been observed. Competitive potentiometry has been utilized to compare some of the results.     

Mössbauer Spectroscopic Determination of Stability Constants of Fluorostannate(II) Complexes

Stability constants of fluorostannate(II) complexes were determined Mössbauer spectroscopically by rapid freezing technique. The observed isomer shift values suggested that these complexes were hydrogen bonded in perchloric acid solutions.     

Determination of Stability Constants for Complexes of Ni(II) with Adenine and Guanine from Catalytic Linear Scan Voltammetric Currents

The catalytic effects of adenine and guanine on the reduction of Ni(II) at the hanging mercury drop electrode were used to study the formation of complexes in the bulk of aqueous solutions at 25 °C and ionic strength 0.2 M. Complexation data were obtained from an analysis of the kinetic (catalytic) pure limiting currents, according to a method proposed previously. Values of 3.70 and 3.17 were determined for the logarithms of the stability constants corresponding to the formation of 1 : 1 complexes between Ni(II) – aquo ion and the neutral form of adenine and guanine, respectively.     

Mixed Ligand Complexes of Ni(II) with Arylidene- Anthranilic Acids and Some Lewis Bases

Some binary and ternary complexes of Ni(II) with arylideneanthranilic acids and Lewis bases have been prepared and characterized by elemental analyses, IR spectra and X-ray powder diffraction. On the basis of the IR spectra it was found that the Schiff bases used act as monobasic bidentate ligands except for the ortho-hydroxy derivative which acts as a dibasic tridentate ligand. From X-ray analysis it is concluded that the binary Ni(II) chelates are isostructural, and the ternary Ni(II) complexes are also isostructural.     

Prediction of Stability Constants for Cr(III) and Cr(II) Complexes

Regression analysis was used to derive equations for estimaing thermodynamic stability constants for complexes of Cr²⁺ (log^° ₁[Cr²⁺L] = 0.53log^° _n [H _n L]) and Cr³⁺ (log^° ₁[Cr³⁺L] = 0.88log^° _n [H _n L]) from the known protonation constants of H _n L ligands and for determining stability constants of Cr²⁺ and Cr³⁺ complexes from the available stability constants of Cu²⁺ complexes (log^° ₁[Cr²⁺L] = 0.76log^° ₁[Cu²⁺L] and log^° ₁[Cr²⁺L] = 0.60log^° ₁[Cr³⁺L], respectively). Parameters of the Panteleon–Ecka equation for calculating stability constants of Cr²⁺ complexes ( = 0.57) and Cr³⁺ complexes ( = 0.69) with two and three bidentate ligands were also determined. The ratio of logarithmic stability constants for complexes with the same metals but with different metal ionic charges was found to be approximately equal to the ratio of charges on the central ions. The stability constant of Cr(II) sulfate complex was calculated.     

Determination of Stability Constants of Metal(II)-Methionine and Metal(II)-Methionine-Cysteine (Binary and Mixed) Complexes with a Paper Ionophoretic Technique

A mixed complexation reaction of methionine and cysteine with copper(II) and cobalt(II) has been studied in solution phase using the paper electrophoretic technique at ionic strength 0.1 M and a temperature of 35°C. The binary equilibria copper(II)-methionine and cobalt(II)-methionine have also been studied, since this is prerequisite for the investigation of mixed complexes. The stability constants of copper(II)-methionine-cysteine and cobalt(II)-methionine-cysteine mixed complexes were found to be 2.80 ± 0.07 and 2.44 ± 0.11 (logarithm of stability constant values), respectively. This article was submitted by the authors in English.     

Spectrophotometric Determination of Dissociation Constants of Thiovioluric Acid and the Stability Constant of its Fe(II) Complex

Spectrophotometric studies of Fe(II)-thiovioluric acid system indicates the presence of a 1:2 complex in the pH range 4.0–6.5. The apparent equilibrium constant (K′₁) has been determined by general absorbance-extinction concentration scheme. The first and second dissociation constants of the acid have been studied at an ionic strength of 0.1 M while the third dissociation constant has been determined at I = 1 M. The effects of sudden pH change and buffer compositions on the dissociations have also been investigated. The stability constant of the complex has been calculated from the apparent equilibrium constant at ionic strength of 0.1 M. The stability constant works out to be 15.67 at pH 5.5.     

Concentration and Thermodynamic Stability Constants of Magnesium(II) and Calcium(II) Tartrate Complexes in Aqueous Solutions

The formation of calcium and magnesium tartrate complexes was studied by potentiometric titration at ionic strengths of 0.1 and 0.3 (in the presence of tetraethylammonium chloride) at a temperature of 298.15 K. The composition and the stability constants of the complexes formed in the system were determined. The known stability constants were used to optimize the conditions of calorimetric determination of the heats of formation of calcium and magnesium tartrates in an aqueous solution.     

HPLC法测定某些高铼酸盐易变配位化合物的稳定常数

根据用柠檬酸盐作流动相时,ReO_4~-在PRP-S柱上保留时间出现异常现象,本文提出用HPLC法测定高铼酸根与柠檬酸、酒石酸和草酸形成的易变配位化合物的稳定常数,在水溶液中分别为123、35.6和45.1。     

Complexes of Cu(II), Ni(II), Co(II), and Ag(I) Metals with 1,4-Bis(3-Phenyl Triazenil) Benzene

Moscow University Chemistry Bulletin - New complexes of Cu(II), Ni(II), Co(II) and Ag(I) with 1,4-bis(3-phenyl triazenyl) benzene are obtained. Using the methods of IR, EPR, electron spectroscopy,...     

Reactivity of potassium tetracyanomercurate with Ag(I), Ni(II) And Co(II)

Potentiometric and conductometric studies on the reactions between K(2)Hg(CN)(4) and Ag(I), Ni(II), Co(II) are reported. The possibility of determination of these metal ions has been evaluated and some titration data are reported.     

Complexes of sterically-hindered diaminophosphinothiolate ligands with Rh(I), Ni(II) and Pd(II)

Two new sterically demanding diaminophosphinothiolate ligands (HL¹ and HL²) have been prepared and the X-ray crystal structure of the Li salt of HL² has been determined. The complex [Pd(L¹)₂] was fully characterized, but in contrast to other phosphinothiolates, complexes with the M(L)₃ stoichiometry could not be prepared. Reaction of LH¹ with Ni(II) led to cleavage of the arythiolate group and isolation of a thiolate bridged dimer, confirmed by an X-ray crystal structure. The Rh(I) complexes [Rh(nbd)L] (L = L¹, L²) were characterized including an X-ray structure.     

Potentiometric and UV-Visible Spectrophotometric Studies of the Stability of Thorium(IV) Complexes with (o-Hydroxyphenyl) Mono- and Di-Methylenephosphonic Acids

Protometric studies were performed in aqueous solutions at 25^C and 0.1 ,mol.dm⁻³ ionic strength (NaClO₄) to determine the complexing abilities of eight (o-hydroxy-phenyl) mono- and di-methylenephosphonic acids (differently substituted by chromophoric or auxochromic groups) towards thorium(IV). The number, the nature of the species present in solution, their overall stability constants over a broad acidity range and their individual electronic spectra, as resolved by computation, have been determined by potentiometry and UV-visible spectrophotometry.The formation of 1:1 species, partially protonated MLH_x and totally deprotonated [ML], as well as hydroxo species -- mononuclear ML(OH)_x and dinuclear M₂L(OH) _x is reported with thorium(IV). The results show that the complexing power, which is not very different in the lanthanide series, is much higher for thorium(IV). The ratio Th⁴⁺/Eu³⁺ reaches eight log₁₀ units with some of the ligands.     

Determination of Stability Constants of Cadmium(II) Complexes with Diallyl Disulfide,Dimethyl Disulfide and Diallyl Sulfide Using Differential Pulse Voltammetry

The study of the binding of heavy metal ions by organosulfur compounds of garlic is especially important for the understanding of many biological systems. Cadmium is a non-essential heavy metal known to be one of the most toxic environmental pollutant.Interactions between cadmium and diallyl disulfide (DADS), dimethyl disulfide (DMDS) and diallyl sulfide (DAS) were investigated by differential pulse voltammtery. Determination of the stability constants of cadmium(II) with DADS, DMDS and DAS complexes was based on the DeFord–Hume methodology that calculated from the dependence of the shift of cadmium( II) peak potential upon addition of the ligands DADS, DMDA and DAS separately. The results of this study provide evidence of the formation of 1: 1 and 1: 2 complexes between cadmium(II) and DADS, DMDS and DAS with stability constants (β) in the range of ca. 10^5.8–10^6.2 and 10^9.6–10^10.6 respectively.     

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

The acidity constants of the six thienyl- and the three phenyl-pyridines, and the stability constants of the corresponding Cu²⁺ 1:1 complexes were determined in aqueous solution (I = 0.1, NaCIO₄; 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 Cu²⁺ 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 Cu²⁺, in opposition to an earlier claim [1].     

Complexes of cyclic aminomethylphosphines with Pt(II), Pd(II), Cu(I), and Ag(I) salts

1,3,5-Diazaphosphorinanes and 1,5,3,7-diazadiphosphacyclooctanes form complexes with Pt(II), Pd(II), Cu(I), and Ag(I) salts. Platinum and palladium are coordinated through phosphorous atoms. In the case of 1,3-diphenyl-5-p-toluidenomethyl-1,3,5-diazaphosphorinane complex formation with platinum and palladium is accompanied by formation of a new polydentate ligand, p-tolylbis-(1,3-di-p-tolyl-1,3,5-diazaphosphorinane-5-yl)methylamine, where the metal is also bonded to phosphorus atoms.DeceasedA. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan' Scientific Center, Russian Academy of Sciences, 420083 Kazan'. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 335–342, February, 1992.     

Stability Constants of Some Univalent Cation Complexes of 2,3-Naphtho-15-crown-5 in Nitrobenzene Saturated with Water

The extraction of micro amounts of cesium by nitrobenzene solutions of sodium, potassium and rubidium dicarbollylcobaltates (M⁺B⁻;M⁺=Na⁺,K⁺,Rb⁺) has been investigated in the presence of 2,3-naphtho-15-crown-5 (N15C5, L). The equilibrium data were explained by assuming that ML⁺ and ML₂⁺ complexes (M⁺=Na⁺,K⁺,Rb⁺, Cs⁺; L=N15C5) were present in the organic phase. The stability constants of the complex species ML⁺ and ML₂⁺ have been determined in nitrobenzene saturated with water. It was found that the stability of the complex cation ML⁺ (where M⁺=Na⁺,K⁺,Rb⁺, Cs⁺; L=N15C5) in water-saturated nitrobenzene solutions increases along the series Cs⁺<Rb⁺<K⁺<Na⁺, whereas that of the species ML₂⁺ in the same medium increases in the order Cs⁺<Rb⁺<Na⁺<K⁺.     

Stability Constants of Cu(II) Hydroxypropylenediaminetetraacetates

Equilibrium of complexation between 2-hydroxypropylene-1,3-diamine-N,N,N,N-tetraethanoic acid (H₄L) and u²⁺ ions was studied by potentiometric and spectrophotometric methods. Stability constants of CuL^2– and CuHL^– complexes were determined at 298.15 K and I = 0.5 (KNO₃).