Complex Formation of Monomeric Phosphorus Oxoacids with Sodium Ion in Donnan Exclusion Chromatography

Abstract

A method for evaluation of stability constants of very unstable and labile complexes has been proposed by the use of Donnan exclusion chromatography. The stability constants of sodium complexes of monomeric phosphorus oxoacids have been evaluated to be log β₁ = -0.04 for phosphinate, log β₁ = 0.86 and log β₂ = 0.24 for hydrogen orthophosphate and log β₁ = 0.61 and log β₂ = 0.16 for phosphonate, respectively, at I = 1.00 (CH₃)₄NCl, t = 25.0° ± 0.1°C.     

Application of Ion-Exclusion Chromatography to the Study of Equilibria of Anionic Complexes

Abstract

An ion-exclusion chromatographic method for the determination of a stability constant of an anionic metal complex has been devised. The stability constants (1og β₁) of magnesium diphosphate and magnesium triphosphate complexes at 1=0.1 and 15°C were evaluated to be 5.06 and 5.89 in sodium chloride solution.     

POLAROGRAPHIC INVESTIGATION OF THE SYSTEMS ARSENIC(III)-TARTARIC ACID AND ARSENIC(III)-1,2-DIAMINO-CYCLOHEXANE-N,N,N′,N′-TETRAACETIC ACID (DCTA)

Abstract

The reactions between As(III), tartaric acid (H₂T)and DCTA were investigated polarographically. The conditional stability constants of As(III)-complexes at a given pH-value and variable ligand concentration were calculated from the change of the limiting currents. The optimum conditions for calculating stability constants from the current were also discussed. It was found that DCTA (H₄L)formed the complex [As(OH)₂HL]^2- whose overall formation constant was lgβ111=(20.67 ±0.09)atμ=0.1 and t°- (25.0±0.2)°C, whereas the complex between As(III) and H₂T was [As(OH)₂T]^? with an overall stability constant 1gβ 101= 6.62 ±0.14 at μ=0.1 and t°= (25 ± 0.2)°C.     

Differential Pulse Voltammetric Study of Complexes of Rare Earth Ion(Eu3+) with Glutarate and 1,2-Diminopropane

Abstract

The mixed complexes of Eu (III) with glutarate (Gluta) and 1,2-diaminopropane (DMPA) have been studied at 25°C, μ=0.12(NaClO₄) by differential pulse voltammetry(DPV). The reduction process in each case appears to be quasi-reversible and diffusion-controlled. The stability constants have been measured by Schaap and McMasters′ method. The stability constants of three mixed complexes formed are logβ₁₁=7. 414 for [Eu(Gluta) (DMPA)]⁺, logβ₂₁ = 8. 506 for [Eu(Gluta)₂ (DMPA)]^? and logβ₁₂ = 9. 984 for [Eu(Gluta) (DMPA)₂]⁺.     

Nonaqueous Liquid-Liquid Extraction. Extraction of Zinc from Methanol-Water Solution of Chloride by Trioctylphosph1Ne Oxide in Decaline

Abstract

The distribution of zinc was studied between the decaline phase having tri-n-octylphosphine oxide (TOPO) and the methanol-water phase (4:1 in molar ratio) having chloride ion, and the stability constants of zinc with chloride in the methanolic solution were calculated from the extraction experiments (K₁ = 2.4 × 10³, K₂ = 1.9 × 10²at 298°K).     

EQUILIBRIA INVOLVING COBALT(II) HALIDES AND PHOSPHINE OXIDES I. A SPECTROPHOTOMETRIC STUDY OF THE COBALT(II) CHLORIDE — TRIPHENYLPHOSPHINE OXIDE SYSTEM IN ACETONE MEDIUM

Abstract

The CoCl₂-triphenylphosphine oxide system was studied in anhydrous acetone medium, at 25.00 · 0.05 ° C, by spectrophotometry. It was found that the system comprises at least three complex species, whose over-all stability constants are: β₁ = (1.40 · 0.10) · 10⁴ M^?1, β₂ = (6.77 · 0.95) · 10⁶ M^?2, β₃ = (1.77 · 0.40) · 10⁹ M^?3. The composition of the system as well as the values of the stability constants of the complex species are in a marked disagreement with the literature data. The compatibility between the experimental data and the results obtained in the present work was confirmed by different methods.     

Potentiometric study of the protonation and binary complexation equilibria between the hydrogen ion,copper(II) ion and zinc(II) ion and the picolinate ion in dioxane-water mixtures

Protonation constants of picolinic acid and stability constants of Cu(II) and Zn(II) picolinate complexes were determined potentiometrically in 50% (v/v) dioxane-water solution at 25°C and 0.2 M KNO₃. The values obtained for the constants were: protonation constants for picolinate ion: logβ₁ = 5.36±0.01 and logβ₂ = 6.80±0.04; stability constants for copper(II) complexes: logβ_1.1 = 7.766±0.001 and logβ_1.2 = 16.826±0.007; stability constants for the Zn(II) complexes: logβ_1.1 = 6.10±0.05, logβ_1.2 = 11.47±0.03 and logβ_1.3 = 15.77±0.08. No protonated nor hydroxo-complex was detected in the metal ion-picolinate systems.     

O-(2-Thiazolylazo)-4-Chlorophenol Complexes and Their Utility as Metallo-Chromic Indicators for Nickel(II) Ion

Abstract

The stability constants of the complexes formed between o-(2-thiazoiylazo)-4-chlorophenol (TACL) and bivalent metal ions obtained spectrophotometrically were: logK_MnR = 2.86, logK_CoR = 5.37, logK_NiR = 6.12, logK_{NiR 2} = 5.44, logK_CuR = 8.39, logK_ZnR = 4.54, logK_{ZnR 2} = 4.43 and logK_CuR = 5.65, (20°c, μ = 0.1, 10% v/v aqueous dioxane). These values coincided well with the Irving-Williams order.

The acid dissociation constants of analogous new dyestuffs synthesized in our Laboratory, o-(2-thiazolylazo)-phenol, o-(2-thiazolylazo)-4-bromophenol and o-(2-thiazoly-lazo)-4- iodophenol were 7.36, 7.35, and 7.25, respectively (20°C, μ = 0.1, 10% v/v aqueous dioxane).

TACL was found to be applicable as a metallochromic indicator for the titration of nickel(II) in weakly acidic media using EDTA as a titrant. No heating was required.     

SOLUTION STUDY AND CRYSTAL STRUCTURE OF A PENTACOORDINATE ZINC(II) COMPLEX WITH N,N″-bis-(2-HYDROXYBENZYL)-DIETHYLENETRIAMINE

Abstract

The stability constants of Zn(II) complexes with N,N″-bis-(2-hydroxybenzyl)-diethylenetri-amine(H₂L) were determined by potentiometric pH titration at 25°C and at 0.1 M KNO₃ ionic strength. A neutral complex ZnL was synthesized. In addition to IR, and ¹H NMR spectra, its structure was established by single crystal X-ray diffraction. The crystal is orthorhombic, of space group Pbca, with cell constants a = 17.865(4), b = 20.079(4), c = 9.598(2)Å, z = 8 and D_c = 1.461 g°Cm^?3. The structure was solved and refined to R = 0.049 (R_w = 0.054). The coordination geometry around the zinc ion is trigonal-bipyramidal with a large distortion, exhibiting two nonequivalent phenolates.     

The Influence of the Steric Effect of the Substituents on the Phosphorus Acids Dissociation

Abstract

The dissociation processes of a series of phosphoric, phosphonic, and phosphinic acids have been studied by the modified method of potentiometry in water and water-ethanol media at 25°C. The influence of substituents on the acidic properties of these compounds has been investigated. As a measure of the substituents steric effects the R_s constants, calculated on the basis of frontal steric model (1), nave been used. A good linear relationship between pKa values in different media has been found. For all series of acids a linear relationship between pKa values and R_s constants of substituents at phosphorus has also been established. In the case of dialkylphosphates in water, for example, such a relationship is expressed by equation:

pKa = (-0.717 ± 0.028)-(0.556 ± 0.009) R_s

N = 7, R = 0.9932, S_o = 0.011

pKa value rises with the increase of the steric effect of the substituents at phosphorus which may be conditioned by the steric hindrance to the anion solvatation.     

EQUILIBRIUM STUDIES OF THE REACTION BETWEEN TETRACHLOROPALLADIUM(II) ANION AND SULFOXIDES. THE FORMATION OF THE MONO-S-SULFOXIDE COMPLEXES

Abstract

The equilibrium coefficient, K₁, for the reaction [PdCl₄]^2- + RR′ SO ? [Pd(RR′ SO)Cl]^? + Cl^?, has been determined for dimethylsulfoxide, tetramethylensulfoxide, and phenylmethylsulfoxide and found to be 67, 46 and 8.8 respectively at 25°C, ü= 1.0 in 95:5 methanol-water. Values for the equilibrium constants for the dimethylsulfoxide complex are also reported at other ionic strengths. The equilibrium constants for the second stage, [Pd(Me₂SO)Cl₃]- + Me₂SO)?-[Pd(Me₂SO)₂Cl₂] + Cl^?, has been determined for dimethylsulfoxide only, K₂=2.5 × 10^?2 at 25°C (μ not controlled). The causes of the mutual destabilisation of two dimethylsulfoxides are discussed.     

The structure of 1,3-dichloropropyne as determined by gas electron diffraction and comparison with microwave data

The structure of 1,3-dichloropropyne has been studied by gas electron diffraction. The resulting parameters r_a have been converted into r_α^o distances. A geometrical structure has been fitted to these internuclear distances. Thus the following parameters (r_α^o) have been determined: r(C₁-Cl₁) = 1.629 (10) A, r(C₁C₂) = 1.201 (13) Å, r(C₃-Cl₂) = 1.791 (6) A, ∠(C₂-C₃-Cl₂) = 111.1° (1.0°), ∠(H-C₃-H) = 98.8° (3.1°), ∠(C₂-C₃-H) = 108.7° (3.2°). ∠(Cl₁-C₁C₂) = 176.6° (1.1°), ∠(C₁C₂-C₃) = 182.7° (1.4°). Inconsistencies have been detected between our results and the rotational constants reported by Günther and Zeil. Discussion of the problem including rotational constants of the first excited vibrational state leads to the conclusion that the observed discrepancies are due to temperature effects.     

Complexation of neptunium(V) by salicylate,phthalate and citrate ligands in a pH 7.5 phosphate buffered system

Conditional stability constants, enthalpies and entropies of complexation at pH 7.5 and ionic strength 0.1 have been determined for neptunium(V) complexes of phosphate, salicylate, phthalate and citrate. Phosphate forms a complex with log β = 2.36 ± 0.42 at 25°C, ΔH°_c = ? 69.9 kJ/mole and ΔS°_c = ? 188 J/mole-K. At pH 7.5 salicylate does not form a complex with neptunium(V) due to the low charge density of the NpO₂⁺ ion and incomplete ionization of the salicylate ion. Phthalate forms a complex with log β = 3.43 ± 0.33 at 25°C, ΔH°_c = 33.5 kJ/mole and ΔS°_c = 182 J/mole-K. Citrate forms a complex with log β = 4.84 ± 0.72 at 25°C, ΔH°_c = 14.0 kJ/mole and ΔS°_c = 140 J/mole-K. In all cases, only 1:1 complexes were identified.     

AN EQUILIBRIUM AND RATE STUDY OF THE INTERACTION OF AQUEOUS CHROMIUM(III) ION WITH ADENINE

Abstract

Potentiometric titration data obtained at 50° for aqueous solutions containing aquochromium(III) ions and adenine were analyzed to yield values for the acid dissociation constants of adenine and the formation constants of 1:1 and 1:2 mononuclear complexes. There is also evidence for a 2:2 dimer for which elemental analysis data suggest a structure of the form (HL=neutral adenine): [(H₂ O)₂ (HL)Cr-μ(OH)₃ -Cr(HL)(H₂ O)₂]³⁺. The kinetic studies indicate that the 1:1 complex is formed in excess adenine with a half-time of about two hours at pH=4.4 and 60°. The proposed mechanism involves an outer-sphere associative intermediate of appreciable stability (K_A ～ 200) followed by rate-determining substitution of adenine for ligand water to produce the 1:1 complex. A much slower subsequent reaction yields the dimer as the final stable product. The formation of the 1:1 complex is an equilibration and both forward and reverse rate constants were determined. The pH dependence data indicate that the reactive species in the system are HL, Cr(H₂ O) ₅OH²⁺, and Cr(H₂ O)₄ (OH)₂ ⁺.     

Protolytic properties and complexation with copper(II) ions of some azo derivatives of β-arylaminopropionic acids

The azo coupling reaction of N-(2-carboxyethyl)anthranilic acid and N,N,N′,N′-tetrabis(2-carboxyethyl)-1,3-phenylenediamine with diazosulfanilic acid yielded the complexones sodium 4-N-(2-carboxyethyl)amino-5-carboxyazobenzene-4′-sulfonate (I) and 2,4-N,N,N′,N′-tetrabis(2-carboxyethyl)diaminoazobenzene-4′-sulfonic acid (II), respectively. The acidity constants of I and II (20°C, μ = 0.1M KCl) were determined to be as follows: for I, pK ₀₀ = 1.29 ± 0.13, pK ₀ = 2.92 ± 0.07, pK ₁ = 3.92 ± 0.05, pK ₂ = 5.16 ± 0.03; for II, pK ₀₀ = 2.35 ± 0.06, pK ₀ = 2.81 ± 0.09, pK ₁ = 3.21 ± 0.11, pK ₂ = 3.81 ± 0.09, pK ₃ = 4.34 ± 0.04, pK ₄ = 5.03 ± 0.06, pK ₅ = 6.67 ± 0.07. The electronic absorption spectra of I and II were measured, and acid-base equilibrium scheme for I and II in aqueous solutions were suggested. The complexation constants of I and II with copper(II) ions were determined to be logK _CuQ^I= 5.47 ± 0.06 and logK _CuQ^II= 5.72 ± 0.13 (20°C, μ = 0.1 M KCl).     

Microwave spectrum and substitutional structure of CH2DF

Forty-two transitions of the microwave spectrum of CH₂DF have been observed in the region between 75 and 450 GHz. The measurement of both a-type and b-type transitions makes possible the analysis of the spectrum and the accurate calculation of the rotational constants (in MHz): = 119 675.0535 ± 0.074, = 24 043.4415 ± 0.072, ? = 22959.3732 °0.072, °j = 0.049371 ±0.00011, °_jk = 0.34268 ±0.0006, 2_k = 3,3774 ± 0.0035, δ _j = 0.002329 ± 0.000045, δ_k = 0.0687 ± 0.036. These constants, in combination with the results of earlier work on the symmetric speci r_s structure calculation based entirely on high-accuracy microwave data. The structural parameters are r_CH = 1.100 Å, r_CF = 1.383 Å, and ∠HCH = 110° 37'.     

THE PHENOMENON OF CONGLOMERATE CRYSTALLIZATION. PART 50. THE CRYSTALLIZATION BEHAVIOR OF [trans-Co(en)2(NO2)2]ClO4 (I), MESO-[Co-trans-Me-(N-Me-ETHYLENEDIAMINE)2-trans-(NO2)2]ClO4 (II), K[trans-Co(β-ALANINATO)2(NO2)2] (III) AND THE ISOLATION AND PARTIAL STRUCTURAL DESCRIPTION OF (H5O2)[trans-Co(β-ALANINATO)2(NO2)2] (IV)

Abstract

[trans-Co(en)₂(NO₂)₂]ClO₄ (I) crystallizes, at 22°C, from a deionized water solution, as a racemate, in space group P$1 (No. 2), with lattice constants: a = 6.581(2)Å, b = 8.274(1) Å, c = 12.660(3)Å, α = 77.28(2)Å, β = 76.58(2)°, γ = 75.20(2)° V = 638.71;ų and d(calc; MW = 370.59,z = 2) = 1.927gcm^?3. A total of 2233 data were collected over the range of 4° ≤ 2θ ≤ 50° of these, 1961 (independent and with I ≤ 3σ(I)) were used in the structural analysis. Data were corrected for absorption (μ = 15.989 cm^?1) and the relative transmission coefficients ranged from 0.6792 to 0.9874. The final R(F) and R≤(F) residuals were, respectively, 0.0738 and 0.0763. Two half cations are located at inversion centers; the anions are in general positions.

meso-[Co-trans-Me-(N-Me-ethylenediamine)₂-trans(NO₂)₂]ClO₄ (II) [(N-Meen) = N-methyl-ethylenediamine] crystallizes at 22°C, from a deionized water solution in space group Pbca (No. 61) with lattice constants: a = 16.882(5) Å, b = 11.990(3) Å, c = 15.017(5) Å; V = 3039.72 ų and d (calc;MW = 398.64, z = 8) = 1.742g cm^?3. A total of 5281 data were collected over the range of 4° ≤ 2θ ≤ 50° of these, 1779 (independent and with I ≤ 2.5σ(I) were used in the structural analysis. Data were corrected for absorption (μ = 13.501 cm^?1 and the transmission coefficients ranged from 0.7956 to 0.9947. The final refinement of the structure (anisotropic thermal parameters for the heavy atoms; idealized hydrogens for the cation) are R(F) = 0.045 and R_w (F) = 0.052). The -NO₂ ligands are trans to one another in the axial direction while the N-methyl groups are trans to one another across the basal plane. The cations are located in general positions and the torsional angles of the en rings are δ(N1-C1-C2-N2 = 52.0°) and δ(N3-C3-C4-C4 = 51.0°), in contrast with those of (I) which are of opposite helical chirality. This compound is one of two trans-Co(III)X₂ cations of which we are aware that, while sitting at a general position of the space group, has two ethytenediamine rings of the same helical chirality.

K[trans-Co(β-alaninato)₂(NO₂)₂] (III) obtained after several batches of crystals of (TV) had separated from the mother liquor (see Syntheses). (III) crystallizes at 22°C, in space group Cc (No. 9) with lattice constants: a = 12.385(6)Å, b=13.109(5)Å, c = 8.290(5)Å, β=115.19° V = 1217.97 ų and d(calc; MW = 366.22, z = 4) = 1.997 g cm^?3. A total of 1238 data were collected over the range of 4° ≤ 2θ 50° of these, 1016 (independent and with I ≤ 2.5σ(I) were used in the structural analysis. Data were corrected for absorption (μ 17.90cm^?1) and the transmission coefficients ranged from 0.5322 to 0.6627. The final R(F) and R_w (F) residuals were, respectively 0.020 and 0.022. Solution of the structure, using the first batch of crystals, proved that the compound isolated was the (H₅O₂)⁺ derivative (see below and Discussion). A later batch of crystals contained (III). We have previously observed the precipitation of hydronium salts, trapped by amine carboxylato salts of cobalt (see Discussion). The anions consist of two six-membered rings formed by the metal and two (O,N)-bound β-alaninato ligands; and, both have chair conformations.

(H₅O₂) [trans-Co(β-alaninato)₂(NO₂)₂] (IV) is the substance that first crystalized from an aqueous solution of (III) (see Experimental). It crystallizes, at 22°C, in space group Cc (No. 9) or C2/c (No. 15) with lattice constants: a=12.389(39)Å, b=13.120(11)Å, c=8.299(9) Å, β=115.09(19)° V=1221.72 ų and d(calc; MW=364.15, z=4) = 1.980 g cm^?3. An incomplete data set of 1592 reflections was collected over the range 4° ≤ 2θ ≤ 50° because the crystal decomposes in air due to rapid loss of water of crystallization, as shown by differential scanning calorimetry. 956 data were independent with I ≤ 2.5°(I) and were used in the structural analysis. Data were not corrected for absorption because of decomposition of the crystal. The final R(F) and R_w (F) residuals were, respectively, 0.14 and 0.16. To the precision of such a data set, the anions are identical with those found in (III); however the cation, which sits at an inversion center, consists of a proton sandwiched between the oxygens of two waters thus forming (H₅O₂)⁺ cations similar to those we have described in the past (see Refs. [15–18]).     

Interactions between oxovanadium (IV), glycylvaline and imidazoles: An aqueous potentiometric and spectroscopic study

Speciation has been determined in aqueous oxovanadium, glycylvaline and imidazoles at 25 ± 1°C and μ = 0.1M NaClO₄ using a combination of potentiometry, and visible and EPR spectroscopy. Results of potentiometric and spectroscopic methods are consistent. Calculations of stability constants have been made using the SCOGS computer program.     

Mononuclear and Dinuclear Cobalt Complexes and its Dioxygen Adduct with a New 24-membered Hexaaza Macrocyclic Ligand

Abstract

Dinucleating 24-membered hexaazadiphenol macrocyclic ligand 3,6,9,17,20,23-hexaaza-29,30-dihydroxy-13,27-dimethyl-tricyclo[23,3,1,1^11,15] triaconta-1(29), 11,13,15(30),25,27-hexaene (L or BDBPH), is prepared by the NaBH₄ reduction of the Schiff base obtained from [2+2] template condensation of 2,6-diformyl-p-cresol with diethylenetriamine. The ligand maintains dinuclear integrity for cobalt (II) while facilitating the formation of bridging phenolate dicobalt cores. Potentiometric equilibrium studies indicate that a variety of protonated, mononuclear and dinuclear cobalt (II) complexes form from p[H] 2 through 11 in aqueous solution. The protonation constants of this ligand and stability constants of the 1:1, 1:2 ligand: cobalt(II) complexes were determined in KCl supporting electrolyte (μ = 0.100 M) at 25°C. The mechanism for the formation of dinuclear dioxygen cobalt(II) complexes is also described. The stability constants of mononuclear and dinuclear cobalt complexes were determined under nitrogen. Preliminary results show that the dinuclear dioxygen cobalt (II) complexes do not catalyze hydroxylation of adamantane in the presence of H₂S as two-electron reductant.     

Molecular structure of carbonyl fluoride as studied by gas electron diffraction and microwave data

The molecular structure of carbonyl fluoride has been determined by electron diffraction. The results have been used in conjunction with the rotational constants reported by Carpenter in a combined structure analysis. The values so obtained are r_z (C=O) = 1.1717 ± 0.0013 Å, r_z (C-F) = 1.3157 ± 0.0005 Å, and ∠_zF-C-F = 107.71 ± 0.08°. These agree with the corresponding parameters estimated by Carpenter from the rotational constants alone. The effective constants, α₃, representing the cubic anharmonicity of bond stretching vibrations have been estimated.