Spektrophotometrische Untersuchung des Systems MoO4 2−-o-Methylbenzamidoxim in wäßrig-alkoholischer Lösung

The complexation of MoO₄ ^2? with oMB was investigated spectrophotometrically. The ligand number was determined graphically. A complex 1∶3 was formed. Its formation constant is lgK ₃=5.1±0.09.     

Komplexe des m-Methylbenzamidoxims mit Co(II) und Ni(II)

The complex formation of Co²⁺ and Ni²⁺ with m-methyl benzamide oxime was studied spectrophotometrically in 60% methanol. The complexes [Co(mMB)₂] and [Ni(mMB)₂] appear in alkaline solution. The formation constants are lgK=4.15±±0.04 for [Co(mMB)₂] and lgK=4.08±0.04 for [Ni(mMB)₂] at 25°. The decadic molar extinction coefficients are ε=5000 for [Co(mMB)₂] and ε=560 for [Ni(mMB)₂], resp.     

Copolymerization of vinyl chloride with sulphur dioxide—I molecular association between vinyl chloride and sulphur dioxide

The formation of VC-SO₂ and VC-(SO₂)₂ complexes in liquid mixtures of vinyl chloride (VC) and sulphur dioxide has been shown by (a) the freezing point composition diagram and (b) chemical shifts in the PMR spectrum of VC over the complete composition range. It is postulated that SO₂ can associate with the CC bond and the Cl atom. These complexes may be involved in the copolymerization and influence the composition and stereochemistry of the product. PMR spectra of VC-SO₂-ethane(E) mixtures with [SO₂] ? [E] ? [VC] gave K_v = 2·0 ± 0·5, 1·5 ± 0·1 and 1·1 ± 0·3 at 232·6, 272·6 and 301·3 K with ΔH_f⁰H_f = ?6·6 ± 1·4 kJ mol^?1 for the VC -(SO₂)₂ complex. The chemical shift of the trans β-proton was twice that of the other two protons. indicating that SO₂ adopts an asymmetric orientation to the double bond.     

The inclusion of diflunisal by γ-cyclodextrin and permethylatedβ-cyclodextrin. A UV-visible and19F nuclear magnetic resonance spectroscopic study

The complexation of the diflunisal anion (DF) by γ-cyclodextrin (γCD) and permethylatedβ-cyclodextrin (βPCD) in aqueous solution at pH 7.00 at 298.2 K, has been studied by UV-visible and¹⁹F NMR spectroscopy. The formation of 1∶1 and 1∶2 γCD inclusion complexes proceeds through the two equilibria: (K1) $${\text{DF + }}\gamma {\text{CD}} \rightleftharpoons {\text{DF}} \cdot \gamma {\text{CD}}$$ (K2) $${\text{DF}} \cdot \gamma {\text{CD + }}\gamma {\text{CD }} \rightleftharpoons {\text{ DF}} \cdot {\text{(}}\gamma {\text{CD)}}_{\text{2}} {\text{ }}$$ characterised byK ₁=(5.5±0.2)×10⁴ dm³ mol^?1 andK ₂=(2.3±0.2)×10⁴ dm³ mol^?1 derived from UV-visible spectrophotometric data. The analogous βPCD complexes are characterised byK ₁=(6.86±0.02)×10⁴ dm³ mol^?1 andK ₂=(8.75±2.7)×10¹ dm³ mol^?1. The variation of the¹⁹F chemical shift of DF on inclusion is consistent with the formation of 1∶1 and 1∶2 complexes also. Comparisons with related systems are made.     

The cationic polymerization of fluoral—III. Thermodynamics of polymerization in solution

The equilibrium between fluoral in dichloromethane solution and live condensed liquid polyfluoral has been investigated between 22 and 43°C. Equilibrium monomer concentrations gave: ΔH_ac°(298 K) = -50-8 ± 2·3 kJ mol^?1 and ΔS_sc° (298 K) = -142·7 ± 7·4 J K^-1 mol^-1. With the aid of calibration and monomer vaporization data, thermodynamic values for the polymerization of liquid monomer to liquid polymer were also calculated: ΔH_tc° (298 K) = -47 ± 3 kJ mol^-1 and ΔS_1e° (298 K) = -97 ± 10 J K^-1 mol^-1.     

Thermochemistry of inorganic sulfur compounds III. The standard molar enthalpy of formation at 298.15 K of US1.992 (β-uranium disulfide) by fluorine bomb calorimetry

A thoroughly analyzed specimen of β-uranium disulfide of composition US_1.992±0.002 has been studied by fluorine-bomb calorimetry. The standard molar energy of combustion: Δ_cU_m^o(US_1.992, cr, β, 298.15 K) = ?(4092.5±7.5) kJ·mol^?1 has been determined on the basis of the reaction: US_1.992(cr, β) + 8.976F₂(g) = UF₆(cr) + 1.992F₆(g). The standard molar enthalpy of formation: Δ_fH_m^o(US_1.992, cr, β, 298.15 K) = ?(519.7±8.0) kJ·mol^?1 was derived, and from that result Δ_fH_m^o(US₂, cr, 298.15 K) = ?(521±8) kJ·mol^?1 is estimated.     

Radiochemische Bestimmung der Beständigkeitskonstanten des Komplexes aus Triphenyltetrazoliumchlorid und Antimon(V) in stark salzsaurer Lösung

It is possible to extract Sb(V), even in traces, nearly completely from 6M HCl by 2,3,5-Triphenyltetrazoliumchloride (TTC). The molar ratio of the ion associate in the organic phase is found to be 1∶1. Graphic evaluation of radiometric measurements using¹²⁵Sb as tracer give the following results: extraction constant K_ex=1.65·10⁴, distribution constant K_D=19.95, stability constant of the ion associate β=0.83·10³.     

L'extraction des lanthanides et des actinides par les oxydes d'alkylphosphine : L'extraction del'acide nitrique par quelques dioxydes de diphosphine

The distribution of nitric acid between an aqueous phase of constant or variable ionic strength and a benzene solution of diphosphine dioxide can be explained by the following reactions H⁺_a+ NO_3^-a+ DiPO₀ ? D1PO·HNO₃₀ H⁺_a+ NO_3^-a+ DiPO·HNO₃₀ ? DiPO·2 HNO₃₀ At constant ionic strength, the stability constants K₁″ were determined for the complexes 1,1-DiPO·HNO₃ (98 ± 01 (M)^-1), 1,4-DiPO·HNO₃(44±3 (M)_-1) and 1,5-DiPO·HNO₃ (51 ± 1 (M)^-1). The constants K₁₁″ for the complexes 1,1-DiPO·2 HNO₃ and 1,5-DiPO.2 HNO₃ are respectively 035±001 (M)^-1 and 62 ±0.05 (M)^-1 at 25°. With an aqueous phase of variable ionic strength, values of K₁'=54±7 (M)^-2 for 1,5-D1PO.HNO₃ and K_II'=65 ± 04 (M)^-2 for 1,5-DiPO·2 HN0₃ were obtained     

Phase equilibria and thermodynamics of the double oxide phase Cu3TiO4

Phase equilibria in the system CuCu₂OTiO₂ were investigated in the temperature range of 1160–1270 K by means of thermogravimetry and measurements of the oxygen partial pressure. The tie lines on the isothermal phase diagram run from the phase Cu₃TiO₄ to CuO, Cu₂O, and TiO₂. The existence of Cu₃TiO₅ and Cu₂TiO₃ could not be confirmed in this temperature range. The phase “Cu₃TiO₄” is only stable above about 1140 K and its composition fluctuates between about Cu₃TiO_4.3 and Cu₃TiO_3.9. The formation of Cu₃TiO_4.3 according to the reaction 1.6 CuO + 0.7 Cu₂O + TiO₂ = Cu₃TiO_4.3 is endothermic: (1160 < T < 1270 K) ΔH° = (7600 ± 450 J-mole^?1; ΔS° = (6.7 ± 0.4) J·K^?1·mole^?1. The standard Gibbs free energy, enthalpy, and entropy of formation of Cu₃TiO_4.3 at 1200 K are ΔG°_f = ?101.39 kJ, ΔH°_f = ?1115.84 kJ, and S°_f = 466.76 J·K^?1. Rather similar values were found for Cu₃TiO_3.9.     

Solubility measurements of the uranyl oxide hydrate phases metaschoepite,compreignacite, Na–compreignacite,becquerelite, and clarkeite

The mobility of uranium under oxidizing conditions can only be modeled if the thermodynamic stabilities of the secondary uranyl minerals are known. Toward this end, we synthesized metaschoepite (UO₃(H₂O)₂), becquerelite (Ca(UO₂)₆O₄(OH)₆(H₂O)₈), compreignacite (K₂(UO₂)₆O₄(OH)₆(H₂O)₇), sodium compreignacite (Na₂(UO₂)₆O₄(OH)₆(H₂O)₇), and clarkeite (Na(UO₂)O(OH)) and performed solubility measurements from both undersaturation and supersaturation under controlled-pH conditions. The solubility measurements rigorously constrain the values of the solubility products for these synthetic phases, and consequently the standard-state Gibbs free energies of formation of the phases. The calculated lg solubility product values (lg K_sp), with associated 1σ uncertainties, for metaschoepite, becquerelite, compreignacite, sodium compreignacite, and clarkeite are (5.6 ?0.2/+0.1), (40.5 ?1.4/+0.2), (35.8 ?0.5/+0.3), (39.4 ?1.1/+0.7), and (9.4 ?0.9/+0.6), respectively. The standard-state Gibbs free energies of formation, with their 2σ uncertainties, for these same phases are (?1632.2 ± 7.4) kJ · mol^?1, (?10305.6 ± 26.5) kJ · mol^?1, (?10107.3 ± 21.8) kJ · mol^?1, (?10045.6 ±24.5) kJ · mol^?1, and (?1635.1 ± 23.4) kJ · mol^?1, respectively. Combining our data with previously measured standard-state enthalpies of formation for metaschoepite, becquerelite, sodium compreignacite, and clarkeite yields calculated standard-state entropies of formation, with associated 2σ uncertainties, of (?532.5 ± 8.1) J · mol^?1 · K^?1, (?3634.5 ± 29.7) J · mol^?1 · K^?1, ( ?2987.6 ± 28.5) J · mol^?1 · K^?1, and (?300.5 ± 23.9) J · mol^?1 · K^?1, respectively. The measurements and associated calculated thermodynamic properties from this study not only describe the stability and solubility at T = 298 K, but also can be used in predictions of uranium mobility through extrapolation of these properties to temperatures and pressures of geologic and environmental interest.     

Cation-Induced dimerization of nickel(II), platinum(II), and palladium(II) meso-tetra(benzo-15-crown-5)porphyrinates

Cation-induced dimerization of nickel(II), platinum(II), and palladium(II) meso-tetra(benzo-15-crown-5)porphyrinates (Ni(II)TCP, Pd(II)TCP, and Pt(II)TCP) on treatment with potassium thiocyanate in a chloroform-methanol solution has been studied by electronic absorption spectroscopy. The formation of [{MTCP}₂(K⁺)₄](SCN^?)₄ in solution induces a hypsochromic shift of the Soret band and a bathochromic shift of the β-band with respect to their positions in the spectrum of MTCP. The equilibrium constants (K) for the 2MTCP + 4K⁺ = [{MTCP}₂(K⁺)₄] processes at 20°C are determined to be as follows: log K _Ni(II)TCP = 27.31 ± 1.67, logK _Pd(II)TCP = 27.16 ± 1.43, and logK _Pt(II)TCP = 26.15 ± 1.56.     

Spectrophotometric and potentiometric study of the cobalt(II)-thiocyanate system in aqueous medium

The cobalt(II)—thiocyanate system was spectrophotometrically studied at 2.0 M ionic strength (NaClO₄) and 25°C. The following formation constants were obtained: β₁ = 6.9 M^?, β₂ = 28.9 M^?2, β₃ = 12.1 M^?3 and β₄ = 1.30 M^?4. Three wavelengths were considered, 515, 590 and 615 nm, and the molar absorptivities of each species were calculated. Linear relationships were obtained for $\text{ε}$ vs $\text{n}$ and α_i. There is strong evidence that the tetrahedral [Co(SCN)₄]^2? is virtually the only species absorbing at 590 and 615 nm. An indirect potentiometric method led to comparable equilibrium constants. The cadmium(II)—thiocyanate formation constants used in the indirect method, under the same conditions, were found to be β₁ = 21.51 ± 0.09 M^?1, β₂ = 123 ± 1 M^?2, β₃ = 130 ± 3 M^?3 and β₄ = 173 ± 1.2 M^?4, in good agreement with earlier literature data.     

Gleichgewichte der Protonenaddition an 1, 1-Bis-(4′, 4″-dimethylaminophenyl)-äthylen in Methanol und in Dimethylsulfoxid

The first and second proton addition equilibrium constants of 1,1-bis-(4′, 4″-dimethylaminophenyl)-ethylene ( 1 ) have been measured by the spectrophotometric method in methanol and in dimethylsulfoxide. Defined as acid dissociation constants of the mono- and diprotonated adduct they are: K₁ (CH₃OH) = 8.3 (± 0.9) · 10^?6M, K₂ (CH₃OH) = 1.22 (± 0.06) · 10^?4M, K₁ (DMSO) = 2.3 (± 0.9) · 10^?3M, K₂ (DMSO) ≥ 1M. The evaluation of the electronic and the NMR. spectra demonstrates that the equilibrium of the two monoprotonated tautomers 2 (methyl-carbenium ion) and 3 (ammonium ion) is, in methanol to about 96% on the side of the ammonium ion (tautomeric equilibrium constant K₂₃ = [3]/[2] ? 23). The tautomer 2 cannot be detected in dimethylsulfoxide. The possible causes of these solvent effects are discussed.     

Studies of solid-state ion-selective electrodes prepared from semiconducting organic radical-ion salts

The primary redox reactions for solid-state ion-selective electrodes prepared from electronically semiconducting salts of 7,7,8,8-tetracyanoquinodimethane (tcnq) can be identified by considering the redox properties of their constituent ions or molecules. Three different processes involving the couples, Mⁿ⁺/M⁰, 2tcnq^o/(tcnq^-)₂ and (tcnq^-)₂/2tcnq^2- are possible depending on salt composition. Ionic product values determined by potentiometric and atomic absorption methods are in excellent agreement for several such salts; K_s(K₂tcnq₂)=5.8±1.2·10^-11(pot.), 1.7±1·10^-11 (a.a.s.); K_s(Cdtcnq₂) = 3.0±0.5·10^-9 (pot.), 2.9±0.3·10^-9(a.a.s.); K_s(Pbtcnq₂) = 1.3±0.3·10^-10 (pot.), 0.96±0.2·10^-10(a.a.s.); and indicate that the lower activity limit for electrode response is controlled by the solubility of the sensor material itself. Comparisons of predicted and observed standard electrode potentials provide quantitative support for an ion-exchange mechanism of interference. The behaviour of electrodes prepared from Cu₂tcnq₂ (copper(I)) and Cutcnq₂ (copper(II)) is explained on the basis of an interference mechanism and considerations of solid-state equilibria.     

The low-temperature (5 to 310 K) heat capacity and thermodynamic functions of cesium fluoroxysulfate (CsSO4F) and the standard potential at 298.15 K for the half-reaction: SO4F−(aq) + 2H+(aq) + 2e− = HSO4−(aq) + HF(aq)

The low-temperature (5 to 310 K) heat capacity of cesium fluoroxysulfate, CsSO₄F, has been measured by adiabatic calorimetry. At T = 298.15 K, the heat capacity C_p^o(T) and standard entropy S^o(T) are (163.46±0.82) and (201.89±1.01) J · K^?1 · mol^?1, respectively. Based on an earlier measurement of the standard enthalpy of formation ΔH_f^o the Gibbs energy of formation ΔG_f^o(CsSO₄F, c, 298.15 K) is calculated to be ?(877.6±1.6) kJ · mol^?1. For the half-reaction: SO₄F^?(aq)+2H⁺(aq)+2e^? = HSO₄^?(aq)+HF(aq), the standard electrode potential E at 298.15 K, is (2.47±0.01) V.     

Stable free-radical complexing reagents in applications of electron spin resonance to the determination of metals

Metals can be determined by electron spin resonance (e.s.r.) by using stable free radicals in which the molecules include complexing groups. Such reagents form complexes with metal ions which retain the properties of the free radicals producing the e.s.r. signal. The complexes formed can be separated from the excess of reagent and the metal concentrations measured from the signal intensity. This approach markedly expands the potential of e.s.r. as an analytical technique, because it is not limited to paramagnetic metals. The relatively high sensitivity of free radical determination by the e.s.r. method is an additional advantage. The properties of the spin-labelled β-diketone, 4-acetoacetyl-2,2,5,5-tetramethyl-3-imidazoline-1-oxyl, are described. Dissociation constants are reported for the enol form (pK_a^T = 6.56 ± 0.02) and for the protonated (at the imidazolyl nitrogen) form (pK_a^T = 1.91 ± 0.02), as well as partition constants for the hexane—water (log k_D(C₆H₁₄) = 0.96 ± 0.02) and chloroform—water (log K_D(CHCl₃) = 3.36 ± 0.04) systems. The reagent extracts Cu, Pb, Cd, Hg and Er readily; in the presence of caproic acid iron(III) is also extracted. Copper is extracted as a CuA₂, complex (log K_D = 2.5 ± 0.5; log K_ex = -2.80 ± 0.13; log β₂ = 14.3 ± 1.5). CuA₂ does not give an e.s.r. signal. Iron is extracted as a mixed complex with β-diketone and caproic acid. An extraction—e.s.r. method is reported for the determination of mercury with a detection limit of 2 × 10^-7 M.     

Stable free-radical complexing reagents in applications of electron spin resonance to the determination of metals: Part 2. Spin-labelled iminooxime [1]

Possibilities for the determination of metals by means of the intensity of the e.s.r. signal of the chelate-fonning reagent, spin-labelled iminomonoxime — 4-oximinomethyl-2,2,5,5-tetramethyl-3-imidazoline-1-oxyl, have been studied. The dissociation constant of the oxime group (pK^T_a = 9.36 ± 0.08) and the reagent partition constant in the chloroform—water system (log K_D = 0.80 ± 0.11) are reported. The reagent extracts copper, cobalt and nickel into chloroform. Copper is extracted as its CuA₂, chelate (log K_D = 0.91 ± 0.03; log K_ex = -3.35 ± 0.09; log β₂, = 15.8 ± 0.2). Several properties of the spin-labelled and conventional oximes are compared. It is confirmed that a radical-containing substituent produces a strong electron-acceptor effect. Unusual extractive and e.s.r.- spectroscopic behaviour of cobalt is indicated; an adduct of the spin-labelled chelate with atmospheric oxygen seems to be formed. Methods for the determination of cobalt and nickel based on the extraction with spin-labelled oxime into chloroform and subsequent separation of the excess of reagent on a chromatographic column are described. The detection limits are 3 × 10^-7 M for cobalt and 10^-6 M for nickel.     

Hydrogen Bonding and Solvent Effects on Complexation of Alkali Metal Cations by Lower Rim Calix[4]arene Tetra(O-[N-acetyl-D-phenylglycine methyl ester]) Derivative

Complexation of alkali metal cations with 5,11,17,23-tetra-tert-butyl-26,28,25,27-tetrakis(O-methyl-D-α-phenylglycylcarbonylmethoxy)calix[4]arene (L) was studied by means of spectrophotometric, conductometric and potentiometric titrations at 25 °C. The solvent effect on the binding ability of L was examined by using two solvents with different affinities for hydrogen bonding, viz. methanol and acetonitrile. Despite the presence of intramolecular NH···O=C hydrogen bonds in L, which need to be disrupted to allow metal ion binding, this calix[4]arene amino acid derivative was shown to be an efficient binder for smaller Li⁺ and Na⁺ cations in acetonitrile (lg K _LiL  > 5, lg K _NaL  = 7.66), moderately efficient for K⁺ (lg K _KL  = 4.62), whereas larger Rb⁺ and Cs⁺ did not fit in its hydrophilic cavity. The complex stabilities in methanol were significantly lower (lg K _NaL  =  4.45, lg K _KL  = 2.48). That could be explained by different solvation of the cations and by competition between the cations and methanol molecules (via hydrogen bonds) for amide carbonyl oxygens. The influence of cation solvation on complex stability was most pronounced in the case of Li⁺ for which, contrary to the quite stable LiL ⁺ complex in acetonitrile, no complexation was observed in methanol under the conditions used.     

Synthesis and thermal properties of some lithium β-diketonates

Five new volatile lithium complexes were synthesized by reactions of lithium hydroxide monohydrate (LiOH · H₂O) with β-diketones, namely, dipivaloylmethane (HDpm), hexafluoroacetylacetone (HHfa), trifluoroacetylacetone (HTfa), benzoyltrifluoroacetone (HBtfa), pivaloyltrifluoroacetone (HPta), and valeryltrifluoroacetone (HVta). The complexes obtained were studied by IR and electronic absorption spectroscopy, mass spectrometry, and comprehensive thermal analysis. The temperature dependence of the vapor pressure, which was obtained by the Knudsen effusion method with mass-spectrometric analysis of the vapor phase composition in the 400–450 K range, was used to calculate the standard thermodynamic parameters of the Li(Dpm) sublimation: ΔH°_subl = 45.7 ± 1.7 kcal mol^?1 and ΔS°_subl = 77.9 ± 4.0 cal mol^?1 K^?1.     

Cobaltchelate als Hydrierkatalysatoren. II). Hydridbildung beim [Co(dmgH)2]- und [Co(dpnH)]+ -Komplex

Cobalt Chelates for Hydrogenation Catalysts. II. Hydride Formation with [Co(dmgH)₂] and [Co(dpnH)]⁺ In the presence of benzil as scavanger for the hydridocomplexes [Co(dpnH)]⁺ and [Co(dmgH)₂] the hydride formation in water/n-propanol (50% v/v) becomes the rate determining step, and the ligand hydrogenation is completely suppressed in the case of [Co(dpnH)]⁺, but only partially in the case of [Co(dmgH)₂]. The rate of hydride formation in both cases is 2^nd order with respect to the complex, and the activation parameters ([Co(dmgH)₂]: ΔH^≠ = 48.4 ± 1.0 kJ · mol–¹, ΔS^≠ = ?57.4 ± 3.4J · mol^?1 · K^?1, [Co(dpnH)]⁺: ΔH^≠ = 52.7 = 0.4 kJ · mol^?1, ΔS^≠ = ?59.8 ± 1.2J · mol^?1 · K^?1) indicate a H₂-activation by homolytic splitting for both complexes. Some sources of error and possible causes for the missing activity of [Co(tim)]²⁺ are discussed.