Complexes in non-aqueous solutions

Many potentiometric studies have been carried out to obtain information about the compositions and formation constants of metal complexes in non-aqueous solutions. Ion-selective electrodes and metal (or metal amalgam) electrodes are used as indicator electrodes. 

The diketonates of indium(III) are thermodynamically stable complexes in non-aqueous solution,9 and are sufficiently robust to allow studies of polarographic reduction, which has demonstrated one-electron reduction to the formally indium(II) and indium(I) compounds (see Section 25.2.3.3).30... 

Lanthanides form many types of complexes in both aqueous and non-aqueous solutions and have been studied extensively. In the early stages the main interest was in the development of efficient ligands for the separation of lanthanides by the ion-exchange technique. The second thrust was the study of complexes in non-aqueous solutions which can be used in the solvent extraction separation of lanthanides. 

In aqueous solutions it is needless to state that any complexing ion or ligand has to compete with water molecules for coordination to the metal ion and also should not be so basic in nature that lanthanide hydroxide/hydroxo species are precipitated. With respect to non-aqueous solutions, the limitation is the solubility of ligands in organic solvents in the formation of lanthanide complexes in non-aqueous solutions. Some typical rare earth complexes in solution are given in Table 4.3. 

Complexing in Non-Aqueous Solution, Ed. G. Krestov, Moscow, Nauka, 1989. 

FORMATION AND STABILITY OF MIXED AND POLYNUCLEAR COMPLEXES IN NON-AQUEOUS SOLUTIONS,... 

The solvation of inorganic substances and complex formation in non-aqueous solutions. A. M. Golub, Russ. Chem. Rev. (Engl. Transl.), 1976,45, 479-500 (358). 

The monovalent Co chemistry of amines is sparse. No structurally characterized example of low-valent Co complexed exclusively to amines is known. At low potentials and in non-aqueous solutions, Co1 amines have been identified electrochemically, but usually in the presence of co-ligands that stabilize the reduced complex. At low potential, the putative monovalent [Co(cyclam)]+ (cyclam = 1,4,8,11-tetraazacyclotetradecane) in NaOH solution catalyzes the reduction of both nitrate and nitrite to give mixtures of hydroxylamine and ammonia.100 Mixed N-donor systems bearing 7r-acceptor imine ligands in addition to amines are well known, but these examples are discussed separately in Section 6.1.2.1.3. 

Figure 22.1 The amphiphilic nature of phospholipids in solution drives the formation of complex structures. Spherical micelles may form in aqueous solution, wherein the hydrophilic head groups all point out toward the surrounding water environment and the hydrophobic tails point inward to the exclusion of water. Larger lipid bilayers may form by similar forces, creating sheets, spheres, and other highly complex morphologies. In non-aqueous solution, inverted micelles may form, wherein the tails all point toward the outer hydrophobic region and the heads point inward forming hexagonal shapes.

During the past few decades, it has been shown that multi-nuclear NMR is a very powerful experimental technique to study alkali complexes particularly in non-aqueous solutions. The experimental method used throughout this work was 7Li NMR. This method possesses features that make it convenient for this kind of investigation. Particular attention was given to high-pressure 7Li NMR, which includes the first example reported for... 

In non-aqueous solution, the copper catalyzed autoxidation of catechol was interpreted in terms of a Cu(I)/Cu(II) redox cycle (34). It was assumed that the formation of a dinuclear copper(II)-catecholate intermediate is followed by an intramolecular two-electron step. The product Cu(I) is quickly reoxidized by dioxygen to Cu(II). A somewhat different model postulated the reversible formation of a substrate-catalyst-dioxy-gen ternary complex for the Mn(II) and Co(II) catalyzed autoxidations in protic media (35). 

This book was written to provide readers with some knowledge of electrochemistry in non-aqueous solutions, from its fundamentals to the latest developments, including the current situation concerning hazardous solvents. The book is divided into two parts. Part I (Chapters 1 to 4) contains a discussion of solvent properties and then deals with solvent effects on chemical processes such as ion solvation, ion complexation, electrolyte dissociation, acid-base reactions and redox reactions. Such solvent effects are of fundamental importance in understanding chem-... 

The anion (EtO)2P02 forms the complex Nd EtO)2P02 3 on treatment of anhydrous NdCl3 with OP(OEt)3 in non-aqueous solution. X-Ray analysis shows a linear chain of slightly distorted octahedrally coordinated Nd3+ ions, with Nd—0 = 2.40 A average. Each pair of adjacent Nd3+ ions is bridged by three anions, and each anion bridges thus Nd—O— P(OEt)2—O—Nd.353... 

The antitumour action of the natural antibiotic bleomycin is thought to involve the aerobic degradation of DNA by the Fe2+-bleomycin complex. In order to probe the mechanism of antitumour action of bleomycin, the 4-ethylamido[5,(2 -thienyl)-2-thiophene] imidazole iron(II) complex was synthesized [129]. It was studied in non-aqueous solution using cyclic voltammetry and showed antitumour activity in vitro, its action causing cleavage of the double helical DNA. 

Similar to aqueous solutions studies on lanthanide complex formation in non-aqueous solutions involve complex equilibria characterized by equilibrium constants and stability constants which have been discussed in detail in Chapter 3. To recall, we define the equilibrium constants and stability constants as follows ... 

Many methods have been used in the studies of lanthanide complex formation in non-aqueous solutions. Some commonly used methods are given below ... 

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