Complexation Of Alkali Metal Cations Research Articles

Alkali-metal cryptates in nitromethane. Thermodynamic parameters for complex formation and for transfer among different solvents

Enthalpies of complexation of alkali-metal cations and cryptand 222 in nitromethane have been measured calorimetrically at 298 K. The single-ion enthalpy for the transfer of alkali-metal cations from propylene carbonate (PC) to nitromethane (NM) were derived and single-ion ΔH°t values for these cations in transfers from water are reported.Enthalpies for the transfer of alkali-metal cryptates from water to NM have been obtained from direct calorimetric measurements of the enthalpies of solution of metal-ion cryptates in NM and in water. Combination of these data with single-ion ΔH°t values for the corresponding anions yielded ΔH°t[M+222] from water to NM.Entropies of complexation between alkali-metal cations and cryptand 222, obtained from free energy and enthalpy data in NM are reported. The thermodynamic parameters ΔGc°, ΔHc° and ΔSc° suggest that the process of complexation between the alkali-metal cations and cryptand 222 in dipolar aprotic solvents is strongly influenced by the solvation energy of the cation in the respective solvent. The thermodynamic parameters for the metal-ion cryptates in their transfers from PC to NM are compared with corresponding data for the transfer to other dipolar aprotic solvents and it is shown that, within experimental error, small variations are found in the transfer of the metal-ion cryptates among dipolar aprotic solvents.

Tris(3,6-dioxaheptyl)amine alkali-metal cation complexes. A fast atom bombardment mass spectrometry, infrared, and nuclear magnetic resonance study

Tris(3,6-dioxaheptyl)amine (tdoha, industrial name TDA-1) is shown to complex with a series of alkali-metal cations in solution, complexation being observed by fast atom bombardment mass spectrometry (f.a.b.m.s.; observation of a metal–tdoha cation), i.r., and 19F n.m.r. Approximate values of the relative concentrations of the tdoha and crown ether complexes are obtained by f.a.b.m.s. by competitive complexation experiments with a range of cations.

Complexation of alkali metal and barium cations by sym-dibenzo-16-crown-5-oxyacetic acid in 80% methanol-water. Determination of pH dependence by calorimetric titration

Parametres thermodynamiques et constantes de stabilite des complexes de Ba et des metaux alcalins

ChemInform Abstract: SYNTHESIS AND COMPLEXING PROPERTIES OF NOVEL FERROCENE CROWN ETHERS

AbstractAusgehend von den Hydroxymethylferrocenen (II) bzw. (VII) werden die Ferrocen‐haltigen Kronenether (lag) und (Ib) hergestellt.

Diaza crown ether complexes of alkali metal and ammonium cations paired with organic anions

Formation of a series of diaza crown ether complexes of alkali metal and ammonium cations paired with organic anions is reported. Diaza 18-crown-6 (1) forms complexes with potassium, ammonium, and methylammonium 4-nitrophenolate to yield 1:1 colored crystalline compounds. The lowering of energy in the COC frequency absorption band and the solubility of all crown ether complexes in chloroform provided evidence of complex formation. The 1H nmr signal for −NH protons of crown ether is shifted the most in the [K-1] 4-nitrophenolate complex. The polyether (1) also yields a complex with potassium 2,4-dinotrophenolate but no complex with sodium could be isolated. However, diaza 15-crown-5 (2) yields 1:1 complexes with sodium as well as with potassium and ammonium 4-nitrophenolate salts.

Membrane transport systems. VI. Complexation of cations by lipophilic crown ether carboxylic acids

The complexation of alkali metal and alkaline earth cations by crown ether carboxylic acids has been studied by potentiometric titration and by infrared and nuclear magnetic resonance spectroscopy. Complexation in methanol–water solution is governed by the electrostatic interactions between the cation and the carboxylate, hence discrimination among cations on the basis of ionic radius is poor. The isomers syn and anti (8NH)218-6A2 exhibit differing complexation behaviour towards cations with the anti isomer giving the stronger complexes. Interaction between the carboxylates across the face of the macrocycle of syn (8NH)218-6A2 can be inferred from the potentiometric data. Combined infrared and nuclear magnetic resonance studies of the complexes in chloroform solution show that the cation is held as an asymmetric tight ion pair with the carboxylate. The dimeric salt (4NH18-6)2Ca exhibits both a tight and a symmetric or loose ion pair between the cation and the two carboxylates. The substituents on the macrocycle are pseudoaxially disposed and in some cases gauche ethylenedioxy units can be recognized from the spectra. The complexes are monomeric in solution and in most cases the conformations are unaffected by small amounts of water in the chloroform solution. The structural results correlate with observations from transport experiments.

SYNTHESIS AND COMPLEXING PROPERTIES OF NOVEL FERROCENE CROWN ETHERS

Abstract Two novel ferrocene crown compounds in which the ferrocene nucleus bears one and two 18-crown-6 units are synthesized and their alkali metal cation complexation is examined in solvent extraction. The ferrocene biscrown exhibits selectivity for K+ and Rb+ in competitive extraction.

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

The stability constants for the ML+ complex species, where M+ is an alkali metal cation and L is dibenzo-18-crown-6, in nitrobenzene saturated with water were calculated by employing published equilibrium data. The stability is found to increase in the cation order Li+ < Cs+ < Rb+ < K+ < Na+. For the NaL+, KL+, RbL+, and CsL+ complex cations the individual extraction constants in the water-nitrobenzene system were determined; their values increase in the series Na+ < K+ < Rb+ < Cs+.

A new type of macrobicyclic polyether: synthesis and complexation of alkali metal cations

Macrobicylic polyethers with novel ring structures have been synthesized and found to complex with Na+ and K+ in accordance with the relative sizes of the cavity and the cation.

ChemInform Abstract: CHEMISTRY OF CROWN ETHERS. PART XXII. SYNTHESIS AND COMPLEXING PROPERTIES OF MONOPHOSPHA‐CROWN ETHERS

AbstractDie Komplexierung der wie aufgezeichnet synthetisierten Phospha‐Kronenether (V) und ihrer P‐Oxide mit Li‐, Na‐ oder Rh(l)‐Kationen in CDCl3 wird mittels 1H‐ und 31P‐NMR‐Spektroskopie untersucht.

Chemistry of crown ethers. Part XXII. Synthesis and complexing properties of monophospha‐crown ethers

AbstractThe synthesis of phenyl‐ and tert‐butyl‐phosphadibenzo‐18‐crown‐6 and phenylphosphadibenzo‐21‐crown‐7 is described. The complexation of alkali metal cations and rhodium(I) by these macrocycles and their phosphine oxides has been studied by NMR methods. The phosphorus crown ethers are all capable of solubilizing lithium cations into chloroform. The phosphine oxide macrocycles also solubilize sodium cations. It is remarkable that tert‐butyl‐phosphadibenzo‐18‐crown‐6 complexes the sodium cation, whereas phenylphosphadibenzo‐18‐crown‐6, whose cavity is about the same size, does not. The formation of a bimetallic (Rh(I),Li+) complex of phenylphosphadibenzo‐21‐crown‐7 is discussed.

Über polymere koronanden auf der basis von 18‐krone‐6 enthaltenden vinylmonomeren

AbstractVinyl group containing derivatives of 18‐crown‐6 were synthesized and copolymerized with styrene and p‐divinylbenzene of p‐divinylbiphenyl. The selectivity of the alkali metal cation complexation of one of the polymers was investigated. The prepared polymers were applied as catalysts in several nucleophilic substitution reactions. The influence of the crosslinking agent as well as the degree of crosslinking on the catalytic activity of the polymers was studied.