Solvent extraction of permanganates (Na, K) by 18-crown-6 ether from water into 1,2-dichloroethane: elucidation of an extraction equilibrium based on component equilibria

Ion-pair formation constants (K_MLA mol⁻¹ dm³) of Na⁺– and K⁺–18-crown-6 ether (18C6) complexes with MnO₄⁻ in water (w) were determined potentiometrically at 25 °C. Simultaneously, extraction constants (K_ex mol⁻² dm⁶) of the permanganates with 18C6 from w into 1,2-dichloroethane at 25 °C were obtained from the spectrophotometric determination of distribution ratios of the permanganates. These K_ex values were divided into K_MLA and other three component equilibrium constants and thereby extraction-selectivity and -ability were discussed in comparison with corresponding metal picrate–18C6 extraction systems reported before.     

Synthesis and Crystal Structure of the Cesium Silver ­Permanganate Cs3Ag[MnO4]4

After successful syntheses and structural refinements of the already known permanganates of cesium (Cs[MnO₄]) and silver (Ag[MnO₄]) we started to blend aqueous solutions of both components in various molar ratios. From crystallization experiments of these mixtures only three species of crystals with different chemical compositions were obtained: tricesium monosilver tetrakispermanganate (Cs₃Ag[MnO₄]₄) and, depending upon the respective ratio, either additional silver permanganate or surplus cesium permanganate, namely. The new title compound crystallizes in the orthorhombic space group Pnnm (no. 58) with two formula units per unit cell and cell dimensions of a = 764.53(4), b = 1883.57(9) and c = 584.34(3) pm. The crystal structure of Cs₃Ag[MnO₄]₄ consists of two crystallographically distinguishable cesium cations. (Cs1)⁺ is surrounded by fourteen oxygen atoms constructing a slightly distorted bicapped hexagonal prism. These polyhedra are connected through edge‐sharing with two other polyhedra of this kind to form chains along [001]. The chains are linked to each other via sixfold coordinated Ag⁺ cations (d(Ag–O) = 238–246 pm), arranged in such a manner that they link three oxygen atoms of two cesium polyhedra, leading to a two‐dimensional layer spreading out parallel to the (001) plane. Together with the two crystallographically different tetrahedral oxomanganate(VII) anions [MnO₄]^– (d(Mn–O) = 161–162 pm) the other kind of cesium cations ((Cs2)⁺ with CN = 13) finally connect these layers three‐dimensionally.     

Zur Kenntnis von Oxyden A[MO4]: Über LiMnO4, KMnO4, RbMnO4, CsMnO4 sowie RbIO4 und CsIO4. (– Was heißt eigentlich “Die Kristallstruktur von …”? –)

On the Knowledge of Oxides A[MO₄]: On LiMnO₄, KMnO₄, RbMnO₄, CsMnO₄ as well as RbIO₄, CsIO₄. (– What does “The Crystal Structure of …” mean? –) These investigations confirm again that, sufficient purity, symmetry and lack of disorder etc. of investigated single crystals provided: the structure of a solid is characterized only if a) lattice constants are determined precisely by powder data; b) a couple of single crystals is sufficiently investigated by film data; c) the “quantitative” comparison of crystal structures of a chemical series like A[MnO₄] with another one like A₂[SO₄] alone enables one to estimate the quality of different structural investigations of the same material. d) ” The ” crystal structure of a solid is still non-existent.     

Determination of ion-pair formation constants of univalent metal–crown ether complex ions with anions in water using ion-selective electrodes: application of modified determination methods to several salts

Ion-pair formation constants (mol^–1 dm³ unit), K_MX for a univalent metal salt (MX) and K_MLX for its ion-pair complex (ML⁺X^–) with a crown ether (L) in water, were determined at various ionic strengths (I) and 25°C by potentiometry with ion-selective electrodes for MX=NaPic, NaMnO₄, NaBPh₄, KPic, and KMnO₄; and MLX=Na(18C6)Pic, K(18C6)Pic, and Na(18C6)BPh₄, where Pic^– and 18C6 denote a picrate ion and 18-crown-6 ether, respectively. Equations for analyzing I-dependence of logK_MLX and logK_MX were derived and fitted well to the I-dependence using a non-linear regression analysis. The equilibrium constants at I=0 mol dm^–3, K_MLX° and K_MX°, were simultaneously obtained from the analysis. The experimental values of K_MLX and K_MX were only in agreement with the values calculated from K_MLX° and K_MX°, respectively, in the ranges of higher I.