Stability of Complexes of NH4 + with 18-Crown-6, Dicyclohexyl-18-Crown-6, Dibenzo-18-Crown-6 and Dibenzo-24-Crown-8 in Water Saturated Nitrobenzene

From extraction experiments with ²²Na tracer, the exchange extraction constants corresponding to the NH₄ ⁺(aq) + NaL⁺ (nb)NH₄L⁺(nb) + Na⁺ (aq) equilibrium taking place in the two-phase water-nitrobenzene system (L = 18-crown-6, dicyclohexyl-18-crown-6, dibenzo-18-crown-6 and dibenzo-24-crown-8; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the stability constants of the NH₄L⁺ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the order dibenzo-24-crown-8 (DB24C8) < dibenzo-18-crown-6 (DB18C6) < dicyclohexyl-18-crown-6 (DCH18C6) < 18-crown-6 (18C6).     

Complex forming and extraction properties of oligo benzo-fused crown ethers

The complex forming properties with alkali metal and ammonium ions of a series of oligo benzo-condensed 18-crown-6 ethers1–8 having a different gradation of lipophilicity and of molecular rigidity are investigated by voltammetry at the interface of two immiscible electrolyte solutions (ITIES) and by a liquid-liquid extraction technique. The experimental results obtained in the two phase system H₂O/nitrobenzene are discussed in relation to the structure of the crown and the cation type. The stability constants for the 1 : 1 complexes of Na⁺, K⁺, Rb⁺, Cs⁺ and NH ₄ ⁺ in nitrobenzene have been determined and compared with the extraction constants for the 1: 1 complexes of Na⁺ and K⁺ and for the 1 : 1 and 1 : 2 complexes of Cs⁺, showing the effect of oligo benzo condensation for the 18-crown-6 system.     

Extraction distribution of microamounts of cesium in the two-phase water-HCl-nitrobenzene-benzo-18-crown-6-hydrogen dicarbollylcobaltate system

Summary Extraction of microamounts of cesium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B^-) in the presence of benzo-18-crown-6 (B18C6,L) has been investigated. The equilibrium data have been explained assuming that the HL⁺, CsL⁺ and CsL complexes are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.     

Extraction of microamounts of strontium into nitrobenzene by using hydrogen dicarbollylcobaltate in the presence of dicyclohexyl-18-crown-6

Summary Extraction of microamounts of strontium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B^-) in the presence of dicyclohexyl-18-crown-6 (DCH18C6, L) has been investigated. The equilibrium data have been explained assuming that the complexes HL⁺, HL, SrL²⁺and SrL are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.     

Extraction of microamounts of calcium in the two-phase water-HCl-18-crown-6-nitrobenzene-hydrogen dicarbollylcobaltate system

Summary Extraction of microamounts of calcium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B^-) in the presence of 18-crown-6 (18C6, L) has been investigated. The equilibrium data have been explained assuming that the complexes HL⁺, CaL²⁺and CaL are extracted into the organic phase. The values of extraction and stability constants of the complex species in nitrobenzene saturated with water have been determined.     

Extraction of barium into nitrobenzene using hydrogen dicarbollylcobaltate in the presence of dibenzo-18-crown-6

Summary Extraction of microamounts of barium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B^-) in the presence of dibenzo-18-crown-6 (DB18C6, L) has been investigated. The equilibrium data have been explained assuming that the complexes HL⁺, BaL²⁺, BaL, BaHL³⁺and BaHL are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.     

Crown ether-facilitated transfers of alkali metal ions across the water-nitrobenzene interface

The transfer of Li⁺, Na⁺, K⁺ and Cs⁺ from water to nitrobenzene at their interface as facilitated by benzo-12-crown-4, benzo-15-crown-5, 4′-methylbenzo-15-crown-5 and benzo-18-crown-6 was studied by cyclic voltammetry. The mechanism of the transfer process was discussed and the stability constants of the complexes formed in nitrobenzene were determined.     

Extraction of cesium by the nitrobenzene solution of sodium bis-1,2-dicarbollylcobaltate in the presence of 18-crown-6

Extraction of cesium by the nitrobenzene solution of sodium bis-1,2-dicarbollylcobaltate (Na⁺B⁻) in the presence of 18-crown-6 (18C6, L) has been investigated. The equilibrium data have been explained assuming that the complexes NaL⁺, CsL⁺ and CsL₂ ⁺ are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.     

Extraction of85Sr by the nitrobenzene solution of bis-1,2-dicarbollylcobaltate in the presence of dibenzo-18-crown-6

Extraction of strontium by the nitrobenzene solution of bis-1,2-dicarbollylcobaltate in the presence of dibenzo-18-crown-6 (DB18C6, L) has been investigated. the equilibrium data and the typical maxima concerning the dependencies of the Sr distribution ratios on the total analytical concentration of DB18C6 in the system under study can be explained assuming that the particles Sr²⁺, SrL²⁺, SrL₂ ²⁺, SrHL³⁺ and SrHL₂ ³⁺ are extracted into the nitrobenzene phase. The values of the corresponding extraction and stability constants of the extracted species in nitrobenzene saturated with water have been determined.     

Extraction of cesium by the nitrobenzene solution of bis-1,2-dicarbollylcobaltate in the presence of dibenzo-18-crown-6

Extraction of cesium by the nitrobenzene solution of bis-1,2-dicarbollylcobaltate in the presence of dibenzo-18-crown-6 (DB18C6, L) was investigated. It was found, that besides hydrated cesium ion Cs _org ⁺ the complexes CsL _org ⁺ and CsL _2,org ⁺ were extracted to nitrobenzene phase. No maximums on dependencies of the cesium distribution ratio (D) on the concentration of crown in the systemc _L was found andD increased monotony withc _L. Values of extraction constants and stability constants of extracted species in nitrobenzene have been determined.     

Extraction distribution of microamounts of cesium in the two-phase water-HCl-nitrobenzene-dibenzo-18-crown-6-hydrogen dicarbollylcobaltate system

Summary Extraction distribution of microamounts of cesium in the water-HCl-nitrobenzene-dibenzo-18-crown-6(L)-hydrogen dicarbollylcobaltate has been investigated. The equilibrium data have been explained assuming that the complexes HL⁺, CsL⁺and CsL_2,⁺are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.     

Ion-pair extraction of tetravalent plutonium from hydrochloric acid medium using crown ethers

Ion-pair extraction behaviour of plutonium (IV) from varying concentrations of HCl solution was studied employing crown ethers (benzo-l5-crown-5 (B15C5), 18-crown-6, (18C6), dibenzo-18-crown-6 (DB18C6), dicyclohexano-18-crown-6, (DC18C6), dibenzo-24-crown-8 (DB24C8) and dicyclohexano-24-crown-8 (DCH24C8)) in nitrobenzene as the extractant. Ammonium metavanidate was used as the holding oxidant in the aqueous phase and the conditions necessary for the quantitative extraction of the tetravalent ion were found. The co-extraction of species of the type [HL⁺].[HPu(Cl) ₆ ^– ] and [HL⁺]2·[Pu(Cl) ₆ ^2– ] as ion-pairs (where L represents the crown ether) is suggested.     

On the protonation of dibenzo-18-crown-6

Abstract  

The stability constant of the dibenzo-18-crown-6·H₃O⁺ cationic complex species dissolved in nitrobenzene saturated with water has been determined from extraction experiments in the two-phase water–nitrobenzene system and from γ-activity measurements. Various structures of protonated dibenzo-18-crown-6 are discussed.     

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.     

Extraction of microamounts of calcium,strontium and barium into nitrobenzene by using hydrogen dicarbollylcobaltate in the presence of dibenzo-18-crown-6

Extraction of microamounts of calcium, strontium and barium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B⁻) in the presence of dibenzo-18-crown-6 (DB18C6, L) has been investigated. The equilibrium data have been explained assuming that the complexes HL⁺, ML²⁺, ML₂²⁺ and MHL₂³⁺ (M²⁺ = Ca²⁺, 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.     

Complexes of Mercury(II) Cyanide with Crown Ethers in Dimethylsulfoxide

The complexation of mercury(II) cyanide with macrocyclic ligands 15-crown-5,18-crown-6 and dibenzo-24-crown-8 in dimethylsulfoxide was studied using¹⁹⁹Hg NMR measurements. No significant complexation with 15-crown-5was observed. The stability constants K_s for 1 : 1 complexes with two other ligands were determined and found to be similar, in contrary to the results reported in nitrobenzene. Solvent effects on K_s values obtained are discussed in comparison with the literature data. X-ray crystal structure of Hg(CN)₂.A18-crown-6 was also determined.     

Contribution to the thermodynamics of complexes of alkali metal cations with 18-crown-6 in the water—nitrobenzene extraction system

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=18-crown-6; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. The stability constants of the ML⁺ complexes in nitrobenzene saturated with water were calculated; they are found to increase in the cation order Cs⁺Li⁺Na⁺Rb⁺K⁺. Further, the individual extraction constants for the NaL⁺, KL⁺, RbL⁺ and CsL⁺ complex species in the wate-nitrobenzene system were determined; their values increase in the series Na⁺Rb⁺Cs⁺K⁺.     

Stability of complex of Na+ with 18-crown-6 in nitrobenzene saturated with water

From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Na⁺(aq)+HL⁺(nb)⇆NaL⁺(nb)+H⁺(aq) taking place in the two-phase water-nitrobenzene system (L=18-crown-6; aq=aqueous phase, nb=nitrobenzene phase) was evaluated as logK _ex (Na⁺,HL⁺)=0.1. Further, the stability constant of the 18-crown-6-sodium complex in nitrobenzene saturated with water was calculated: logβ _nh(NaL⁺)=8.0.     

Solvent extraction of calcium into nitrobenzene by using hydrogen dicarbollylcobaltate in the presence of dicyclohexano-18-crown-6 and dicyclohexano-24-crown-8

Extraction of microamounts of calcium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B^?) in the presence of dicyclohexano-18-crown-6 (DCH18C6, L) and dicyclohexano-24-crown-8 (DCH24C8, L) has been investigated. The equilibrium data have been explained assuming that the species HL⁺, $ {\text{HL}}_{2}^{ + },$ CaL²⁺ and $ {\text{CaL}}_{2}^{2 + } $ (L = DCH18C6, DCH24C8) are present in the organic phase. The values of extraction and stability constants of the complex species in nitrobenzene saturated with water have been determined. It was found that the stability constants of CaL²⁺ (L = DCH18C6, DCH24C8) for both ligands under study are practically the same in nitrobenzene saturated with water, whereas in this medium the stability of the complex $ {\text{CaL}}_{2}^{2 + } $ involving the DCH24C8 ligand is somewhat higher than that of $ {\text{CaL}}_{2}^{2 + } $ with the ligand DCH18C6.     

Extraction of strontium from nitric acid solutions by selected crown ethers

The extraction of Sr from nitric acid solutions by the crown ethers, 12-crown-4, 15-crown-5, 18-crown-6 and DB 18-crown-6 dissolved in chloroform has been investigated. Sr is reasonably well extracted by 18-crown-6 compared to other crown ethers from different nitric acid solutions. The extraction is strongly dependent on the concentration of HNO₃ and nitrate salts. Preliminary studies indicate that¹³⁷Cs is also extracted to a limited extent by 18-crown-6 from nitrate medium. Stripping of Sr was achieved by an aqueous solution of low acidity, the crown ether being regenerated for subsequent extraction.