Solvent extraction of microamounts of cesium into nitrobenzene by using potassium and rubidium dicarbollylcobaltates in the presence of benzo-15-crown-5

Extraction of microamounts of cesium by nitrobenzene solutions of potassium dicarbollylcobaltate (K⁺B⁻) and rubidium dicarbollylcobaltate (Rb⁺B⁻) in the presence of benzo-15-crown-5 (B15C5, L) has been investigated. The equilibrium data have been explained assuming that the complexes ML⁺ and ML₂⁺ (M⁺ = K⁺, Rb⁺, Cs⁺) are present in the organic phase. The stability constants of the species ML⁺ and ML₂⁺ (M⁺ = K⁺, Rb⁺) in nitrobenzene saturated with water have been determined.     

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⁺.     

Radon and progeny alpha-particle energy analysis using nuclear track methodology

Extraction of microamounts of cesium by nitrobenzene solutions of sodium, ammonium and thallium dicarbollylcobaltates (M⁺B⁻; M⁺ = Na⁺, NH₄⁺, Tl⁺) in the presence of benzo-15-crown-5 (B15C5, L) has been investigated. The equilibrium data have been explained assuming that the complexes ML⁺ and ML₂⁺ (M⁺ = Na⁺, NH₄⁺, Tl⁺; L = B15C5) are present in the organic phase. The stability constants of the complex species ML⁺ and ML₂⁺ in nitrobenzene saturated with water have been determined.     

Stabilities in Polar Nonaqueous Solvents and Transfer Activity Coefficients from Water to Nonaqueous Solvents of 19-Crown-6-Alkali Metal Ion Complexes

Formation constants of 1 : 1 19-crown-6(19C6) complexes with alkali metal ions weredetermined conductometrically at 25 °Cin acetonitrile(AN), propylene carbonate (PC), methanol, DMF, andDMSO. 19C6 always forms the most stable complex withK⁺. The selectivity order of 19C6 forheavy alkali metal ions isK⁺ > Rb⁺ > Cs⁺.The selectivity for Na⁺ varies withthe solvent; that for Li⁺ is the second lowest(AN, DMSO) or the lowest (PC). Transfer activity coefficients(^SH _{2 O}) of19C6 from water to the nonaqueous solvents (S) weremeasured at 25 °C. The contributions of a methylenegroup and an ether oxygen atom to thelog ^SH _{2 O}value of a crown ether wereobtained. The ^SH _{2 O}values of the 19C6–alkali metal ion complexes(^SH _{2 O} (ML⁺)) werecalculated, M⁺ and L denoting an alkali metal ionand a crown ether, respectively. For AN, PC, andCH₃OH, although the M⁺ ion is more stronglysolvated by water than by AN, PC, or CH₃OH, thelog ^SH _{2 O} (ML⁺) islarger than the correspondinglog ^SH _{2 O} (L)expect for the case of M⁺ = Li⁺.The higher lipophilicity of the19C6 complex ion is attributed to an enforcement ofthe hydrogen-bonded structure of water for the complexion caused by the greatly decreased hydrogen bondingbetween ether oxygen atoms and water uponcomplexation. For DMF and DMSO, thelog ^SH _{2 O} (ML⁺) is also greater thanthe correspondinglog ^SH _{2 O} (L).It was concluded from thisfinding that the unexpectedly lowest stability of the19C6 complex ion in water is due to the hydrogenbonding between 19C6 and water. The stabilities and thelog ^SH _{2 O}of 19C6–alkali metal ion complexes were compared with those of 18C6complexes.     

Thermodynamic study of complexation reactions between 1,7,10,16 Tetra oxa 4,13 diaza cyclo octa decane (Kryptofix22) and Ni<Superscript>2+</Superscript>, Cd<Superscript>2+</Superscript> and Ag<Superscript>+</Superscript> metal cations in some pure and binary mixed non-aqueous solvents using conductometry

The complexation reactions between Ni²⁺, Cd²⁺ and Ag⁺ metal cations with the macrocyclic ligand Kryptofix22 (K22), in pure acetonitrile (AN), ethylacetate (EtOAc), methanol (MeOH) and their binary mixtures have been studied at different temperatures using conductometric method. The obtained results show that in most solvent systems, the stoichiometry of the complexes formed between the macrocyclic ligand and the metal cations is 1: 1 [ML], but in some of the solvent systems, a 1: 2 [ML₂] complex and also [M₂L], [M₂L₂] and [M₂L₃] complexes are formed in solutions. The stability constans of the 1: 1 complexes were obtained using a computer program GENPLOT. A non-liner behavior was observed for changes of logK_f of the 1: 1 complexes versus the composition of AN–EtOAc binary solutions. The stability order of the 1: 1 complexes at 25°C in the binary solvent solution of AN–EtOAc (mol % AN = 50) was found to be: (K22.Ag)⁺ > (K22.Ni)²⁺ > (K22.Cd)²⁺. The obtained values of thermodynamic quantities (ΔH_c⁰,ΔS_c⁰) show that in most of the AN–EtOAc binary solvent solutions, the 1:1 complexation reactions are enthropy stabilized, but from the enthalpy view point, depending on the nature and composition of mixed solvents they are exothermic or athermic.     

Stabilities and Transfer Activity Coefficients from Water to Polar Nonaqueous Solvents of Benzo-15-Crown-5- and 15-Crown-5-Alkali Metal Ion Complexes

Stability constants (K_ML) of 1 : 1 benzo-15-crown-5 (B15C5) complexes with alkali metal ions were conductometrically measured in water at 25°C. Transfer activity coefficients of B15C5 and 15-crown-5 (15C5) from water to polar nonaqueous solvents were determined at 25°C. By using these data and the literature values, transfer activity coefficients of the B15C5 and 15C5 complexes with alkali metal ions from water to the polar nonaqueous solvents were calculated to study the solute-solvent interaction of the crown ether complexes. The stability of the B15C5 complex is lower in water than in any other nonaqueous solvent. The K_ML value for B15C5 is always smaller than the corresponding K ML value for 15C5. The interaction of the B15C5 or the 15C5 complex with the solvents depends on the alkali metal ion in the crown cavity. All the B15C5 and 15C5 complexes undergo hydrophobic hydration, which is particularly stronger for the B15C5 complexes with Na⁺ and K⁺. The unexpectedly lowest stability of the B15C5- or the 15C5-alkali metal ion complex in water among all the solvents is caused by the hydrogen bonding between ether oxygen atoms of uncomplexed B15C5 or 15C5 and water.     

Stabilities in Water of Alkali Metal Ion Complexes with Dibenzo-24-crown-8 and Dibenzo-18-crown-6 and Their Transfer Activity Coefficients from Water to Nonaqueous Solvents

Stability constants K _ML for the 1:1 complexes of Na⁺, K⁺, Rb⁺, and Cs⁺ with dibenzo-24-crown-8 (DB24C8) and dibenzo-18-crown-6 (DB18C6) in water have been determined by a capillary electrophoretic technique at 25°C. The K _ML sequence is Na⁺ < K⁺ < Rb⁺ < Cs⁺ for DB24C8 and Na⁺ < K⁺ > Rb⁺ > Cs⁺ for DB18C6. Compared with DB18C6, DB24C8 exhibits higher selectivity for K⁺ over Na⁺, but lower selectivity for K⁺, Rb⁺, and Cs⁺. To evaluate the solvation of the complexes in water, their transfer activity coefficients sH₂O between polar nonaqueous solvents and water have been calculated. The sH₂O values provide the following information: interactions with water of the metal ions and of the crown-ether oxygens are greatly reduced upon complexation and the complexes undergo hydrophobic hydration in water; the character of each alkali metal ion in solvation is more effectively masked by DB24C8 than by DB18C6, because of the larger and more flexible ring structure of DB24C8. Solvent effects on the complex stabilities are discussed on the basis of the sH₂O values.     

Anion dependence of crown ether selectivities for alkali picrates and sulfonates in dioxane and toluene. A synergistic effect

The binding constants,K _N, of sodium and potassium 8-anilinonaphthalene-1-sulfonate (ANS) and of sodium 5-dimethylamino-1-naphthalenesulfonate (DNS) to benzo-18-crown-6 bound to a 2% cross-linked polystyrene network (RN18C6) were measured spectrophotometrically in dioxane and the results compared with those obtained for picrate salts. The network RN18C6 was then used to measure in dioxane and toluene by a competition method the equilibrium constant,K, of the reaction A^–M⁺N+CrA^–M⁺Cr+N.A^–M⁺N denotes the ionic solute (ANS, DNS, methyl orange or picrate salt) bound to the network RN18C6 (N) and A^–M⁺Cr is the solute bound to a soluble ligand Cr, where Cr represents a series of 18-crown-6 and 15-crown-5 compounds. Combining theK _N andK values the formation constants,K _L, of the crown ether complexes of the respective salts were obtained in dioxane. The data show a reversal in the complexation strength of the 18-crown-6 compounds in dioxane when sodium picrate is replaced by sodium ANS. The results were rationalized in terms of a synergistic effect exerted by dioxane, with dioxane forming a 1:1 dioxanate with the crown ion pair complex. This effect is especially strong with ANS and with a rigid planar crown ether like dibenzo-18-crown-6. The binding constants,K _N, of NaANS and NaDNS to RN18C6 in dioxane are nearly three times larger than for sodium picrate, and the same holds for the potassium salts. Differences in anion interactions with the network appear to be a plausible cause for the anion dependence ofK _N.     

A complexation study of 15-crown-5 with Co2+ cation in some pure and mixed organic solvents

The stability constant (log K _f) and the thermodynamic parameters (free energies, enthalpies, and entropies) of the complexation of Co²⁺ cation with 15-crown-5 (15C5) in acetonitrile-methanol (AN/MeOH), acetonitrile-nitrobenzene (AN/NB), acetonitrile-dichloromethane (AN/DCM) and acetonitrile-1,2-dichloroethane (AN/DCE) binary solvent solutions were calculated from the experimental conductance data at different temperatures. The complexation behavior of the crown ether used in these media was discussed in view of the estimated parameters. In all solvent systems, 15-crown-5 formed a 1: 1 complex with Co²⁺ cation. The stability order of (Co-15C5)²⁺ complex in the binary mixed solvents at 25°C was found to be: AN/NB > AN/DCM ≈ AN/DCE > AN/MeOH. In most cases, a non-linear relationship was observed for changes of log K _f of (Co-15C5)²⁺ complex versus the composition of the binary mixed solvent systems. The experimental results show that the standard thermodynamic parameters of the complexation process change with the nature and composition of the binary solvent solutions.     

Ion-transfer polarographic study of the distribution of alkali and alkaline-earth metal complexes with 3m-crown-m ether derivatives (m = 6, 8) between water and nitrobenzene phases

Stability constants ( ₁ ^NB ) of the 1:1 cationic complexes of Li⁺ Na⁺, K⁺ Ca²⁺ Sr²⁺ and Ba²⁺ with benzo-18-crown-6 (B18C6), Ca²⁺ and Sr²⁺ with 18C6 and dibenzo-18C6 and Li⁺, Na⁺, Ca²⁺, Sr²⁺ and Ba²⁺ with dibenzo-24-crown-8 in a nitrobenzene (NB) solution saturated with water (w) were determined at 25°C by ion-transfer polarography. From these values, distribution constants (K _D,ML) of the 18C6-derivative complex cations between the w- and NB-phases were evaluated using the thermodynamic relation:K _D,ML =K ₁ ^NB , whereK (mol dm^–3) is an overall equilibrium constant of the processes related to the complexation in the w-phase. The data on the distribution of the 18C6-derivative complex cations between the two phases and the complexation in the NB-phase were examined on the basis of an increase in the number of water molecules hydrated to the species relevant to these processes. The 18C6 derivatives showed higher solubilities in the NB-phase than in the w-phase by complexing with the univalent-metal ions, while, for the divalent-metal ions, the derivatives showed lower solubilities in the NB-phase.     

Extraction of NH4 +, K+, Rb+ and Tl+ into nitrobenzene using cesium dicarbollylcobaltate in the presence of dibenzo-21-crown-7

Summary From extraction experiments and g-activity measurements, the exchange extraction constants corresponding to the general equilibrium M⁺(aq) + CsL⁺(nb) ? ML⁺(nb) + Cs⁺(aq) taking place in the two-phase water-nitrobenzene system (M⁺ = NH, K⁺, Rb⁺, Tl⁺; L = dibenzo-21-crown-7; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Further, the stability constants of the ML⁺ complexes in water saturated nitrobenzene were calculated; they were found to increase in the order Cs⁺<K⁺ = Rb⁺?NH<Tl⁺.     

Extraction-ability and -selectivity of tetra-aza-crown ethers for transition metal cations

In order to investigate the relative effects of the differences between the structures and lipophilicities of 1, 10-dioxa-4, 7, 13, 16-tetra-azacyclo-octadecane (TA-18-crown-6) and the tetrabenzyl derivative of 1,10-dioxa-4, 7, 13, 16-tetra-azacyclo-octadecane (TBTA-18-crown-6) on their extraction-abilities and -selectivities for transition metal cations, constants of the overall extraction (logK _ex) of 1:1 (M:L) complexes, the distribution (K _D) for two diluents (CH₂Cl₂ and CHCl₃) with different dielectric constants have been determined at 25 ± 0.1 °C. The magnitude of logK _ex is largely determined by that of K _D. The equilibrium constants of TA-18-crown-6 have been compared with those of TBTA-18-crown-6. It is found that:(i) logK _ex sequences of TA-18-crown-6 and TBTA-18-crown-6 for transition metals in CH₂Cl₂ lie in order: Fe³⁺ > Cu²⁺ > Mn²⁺ > Co²⁺ > Cd²⁺ > Ni²⁺ > Zn²⁺ and Fe³⁺ > Cu²⁺ > Co²⁺ > Mn²⁺ > Ni²⁺ > Cd²⁺ > Zn²⁺ respectively; (ii) the stability sequences of two types of tetra-aza-crown ethers with the transition metal cations in CHCl₃ are the same as follows: Fe³⁺ > Ni²⁺ > Cu²⁺ > Co²⁺ > Zn²⁺ > Cd²⁺ > Mn²⁺, and (iii) unusual selectivities are observed for transition metal-tetra-aza-crowns, e.g. the high Fe³⁺/M ⁿ⁺ selectivity factors (S_f) of TA-18-crown-6, except for the competitive-extractions for the special case in CHCl₃ of TBTA-18-crown-6, it was found that the Mn²⁺/M ⁿ⁺ values were relatively higher according to the other transition metal cations. A systematic sequence in these two types of solvents is not found for a given transition metal cation in terms of the variation of selectivity with the tetra-aza-crown ethers. The results provide alternatives for the rational design of other specific ligands on the transition metal cations.     

Extraction Equilibria between Benzene and Water of Uni- and Bivalent Metal Picrates with Lariat 16-Crown-5: Effect of the Side Arms on the Extraction Ability and Selectivity

The overall extraction constants (K_ex) of uni- andbivalent metal picrates with 15-(2,5-dioxahexyl)-15-methyl-16-crown-5(L16C5) were determined between benzene and water at 25°C. TheK_ex values were analyzed into the constituent equilibriumconstants, i.e., the extraction constant of picric acid, the distributionconstant of the crown ether, the stability constant of the metalion–crown ether complex in water, and the ion-pair extraction constantof the complex cation with the picrate anion. The K_ex valuedecreases in the orders Ag⁺ > Na⁺ >Tl⁺ > K⁺ > Li⁺ andPb²⁺ > Ba²⁺ > Sr²⁺ for theuni- and bivalent metals, respectively, which are the same as those observedfor 16C5. The extraction selectivity was found to be governed by theselectivity of the ion-pair extraction of the L16C5–metal picratecomplex rather than by that of the complex formation in water. Theextraction ability of L16C5 is smaller for all the metals than that of 16C5,which is mostly attributed to the higher lipophilicity of L16C5. Differencesin the extraction selectivity between L16C5 and 16C5 were observed for thebivalent metals but little for the univalent metals. The side-arm effect onthe extraction selectivity was interpreted on the basis of the negativecorrelation between the effect on the complex stability constant in waterand that on the ion-pair extraction constant.     

Complexation Studies of Phosphorus Containing Bis and Tris (Benzocrown Ether) Moieties

The complexation behaviour between salts of Li⁺-Rb⁺ in CD₃CN and tris(benzocrown ether)s 2a,bX=P(NMeN=CH-B15C5)₃ (X = O, S) and tri[bis(benzocrown ether)][N=P(NMeN=CH-B15C5)₂]₃ 3 was investigated by ¹³ C NMR spectroscopy. Using the program RMNSTAB, the complexation constants for the different possible complexes (M₂L, ML andML₂ were L represents one benzo-15-crown-5) were obtained and were compared with those of the corresponding monomer material. A remarkable ``biscrown effect' for compounds 2a,b and 3 was found, especially for potassium and rubidium by the predominant formation of stable ML₂ complexes. The strong chelate effect make these ligands highly efficient extracting agents for alkali metal picrate salts of K⁺, Rb⁺ and Cs⁺,as shown by UV-Vis spectroscopy.     

Stability of complexes of alkali metal cations with dibenzo-24-crown-8 in water saturated nitrobenzene

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M⁺(aq)+NaL⁺(nb)⇄ML⁺(nb)+Na⁺(aq) taking place in the two-phase water-nitrobenzene system (M⁺=Li⁺, K⁺, Rb⁺, Cs⁺; L=dibenzo-24-crown-8; aq=aqueous phase, nb=nitrobenzene phase) were evaluated. Further, the stability constants of the ML⁺ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the Cs⁺Rb⁺L⁺Na⁺ order.     

Solvent extraction of microamounts of strontium and barium from water into nitrobenzene using hydrogen dicarbollylcobaltate in the presence of benzo-18-crown-6

Extraction of microamounts of strontium and barium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B⁻¹) in the presence of benzo-18-crown-6 (B18C6, L) has been investigated. The equilibrium data been explained assuming that the complexes HL⁺, ML²⁺, ML₂²⁺ and MHL₂³⁺ (M²⁺ = Sr²⁺, Ba²⁺) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.     

Thermodynamics of cesium cation complexation with dibenzo-24-crown-8 in mixed nonaqueous solvents

Thermodynamics of complexation of cesium cation by dibenzo-24-crown-8 was studied in three binary solvent mixtures: acetonitrile-nitromethane (AN/NM),N,N-dimethylformamide-nitromethane (DMF/NM) and acetonitrile-propylene carbonate (AN/PC) using the¹³³Cs-NMR technique. In all cases the variation of the formation constant,K _f, with the solvent composition was monotonic:K _f increased as the mole-% of the solvent of low donicity was increased. The temperature dependence ofK _f indicated that the complexes are generally enthalpy stabilized, but entropy destabilized. The enthalpy and entropy of complexation reactions are quite sensitive to the solvent composition. However, their variation with solvent composition was not monotonic but showed maxima or minima at the isosolvation points of the cation or the complexed cation. In all cases an enthalpy-entropy compensating effect was observed.     

Extraction distributions of microamounts of strontium and barium in the two-phase water-HCl-nitrobenzene-dibenzo-21-crown-7-hydrogen dicarbollylcobaltate system

Extraction of microamounts of strontium and barium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B⁻) in the presence of dibenzo-21-crown-7 (DB21C7, L) has been investigated. The equilibrium data have been explained assuming that the complexes HL⁺, ML²⁺, ML₂²⁺ and MHL₂³⁺ (M²⁺ = Sr²⁺, Ba²⁺) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.     

Thermodynamics of Solvation of 18-Crown-6 and Its Alkali-Metal Complexes in Various Solvents

Heats of solution of 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6) in acetonitrile, 1,2-dichloroethane, N,N-dimethylformamide, dimethyl sulfoxide, nitromethane, propylene carbonate, pyridine and water were measured at 25 °C and the enthalpies of the transfer of 18-crown-6 from waterto the aprotic solvents were derived. The thermodynamic quantities, G₁°, H₁° and T S₁°, for the formation of the[M(18-crown-6)]⁺ (M⁺ = Na⁺, K⁺, Rb⁺, Cs⁺, NH₄ ⁺) complexeswere determined by titration calorimetry in dimethyl sulfoxide containing0.1 mol dm^-3 (C₂H₅)₄NClO₄ as a constant ionic medium at 25 °C. These thermodynamic quantities suggest that the complexationof 18-crown-6 with the alkali-metal ions mainly reflects the different solvationof 18-crown-6 and also the different degree of solvent structure.     

Effect of solvent upon competitive liquid-liquid extraction of alkali metal cations by isomeric dibenzo-16-crown-5-oxyacetic acids

The selectivity and efficiency of competitive liquid-liquid extraction of alkali metal cations into organic solvents containingsym-(octyl)dibenzo-16-crown-5-oxyacetic acid (2) andsym-bis[4(5)-tert-butylbenzo]-16-crown-5-oxyacetic acid (3) have been determined. Solvents examined include: dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, 1,1,1-trichloroethane, benzene, toluene,p-xylene, chlorobenzene, 1,2-dichlorobenzene, and 1,2,3,4-tetrahydronaphthalene. The Na⁺/K⁺ and Na⁺/Li⁺ extraction ratios are highest in chloroform. The extraction selectivity is found to correlate with the diluent parameter (DP) of the organic solvent.This paper is dedicated to the memory of the late Dr C. J. Pedersen.