Lifschitz salts

Planar-octahedral equilibria. Dissolution of planar Ni compounds in coordinating solvents such as water or pyridine frequently leads to the formation of octahedral complexes by the coordination of 2 solvent molecules. This can, on occasions, lead to solutions in which the Ni has an intermediate value of jie indicating the presence of comparable amounts of planar and octahedral molecules varying with temperature and concentration more commonly the conversion is complete and octahedral solvates can be crystallized out. Well-known examples of this behaviour are provided by the complexes [Ni(L-L)2X2] (L-L = substituted ethylenediamine, X = variety of anions) generally known by the name of their discoverer I. Lifschitz. Some of these Lifschitz salts are yellow, diamagnetic and planar, [Ni(L-L)2]X2, others are blue, paramagnetic, and octahedral, [Ni(L-L)2X2] or... 

Well-known examples of the square-octahedral ambivalence are the Lifschitz salts, complexes of nickel(II) with substituted ethylenediamines, especially the stil-benediamines, one of which is illustrated in (17-G-IX). Many years ago Lifschitz and others observed that such complexes were sometimes blue and paramagnetic and other times yellow and diamagnetic, depending on factors such as temperature, identity of the anions present, the solvent in which they are dissolved or from which they were crystallized, exposure to atmospheric water vapor, and the particular diamine involved. The bare experimental facts bewildered chemists for several decades. It is now recognized that the yellow species are square complexes, as typified by (17-G-IX), and the blue ones are octahedral complexes, derived from the square complexes by coordination of two additional ligands—solvent molecules, water molecules, or anions—above and below the plane of the square complex. 

More comprehensive examination of spectroscopic and magnetic properties of d ions followed which provided an explanation for the different types of Lifschitz salts (p. II60) and led to studies of systems exhibiting anomalous properties. Rational explanations of these properties were eventually forthcoming. 

Well-known examples of the square-octahedral ambivalence are provided by the Lifschitz salts, which are complexes of nickel(n) with substituted ethylenediamines, especially the stilbenediamines, one of which is illustrated in (25-G-VII). Many years ago, Lifschitz and others observed that such... 

Lewis octet rule. 298 Lifschitz salts, 308 Ligands, 300 UH2. 94 UH ,94... 

Ultraviolet spectra of diazonium salt solutions were recorded for the first time by Hantzsch and Lifschitz as early as 1912. However, electron spectra did not provide significant information on the structure of diazonium ions, either at that time or later. For example, Anderson and coworkers (Anderson and Steedly, 1954 Anderson and Manning, 1955), compared spectra of 4-amino-benzenediazonium salts with those of diphenylquinomethane (4.18). Their conclusion that the structures of these compounds are analogous is basically correct, but the arguments given by Anderson can easily be refuted, as shown by Sorriso (1978, p. 102). 

According to the views presented here, electrolytic dissociation is not the forerunner of chemical reactions and in fact chemical reactions do not depend upon the presence of ions as postulated in that theory. Certain physical properties of substances, which, early in the history of the electrolytic dissociation theory, were considered to be dependent upon, ionization, have since been shown to be independent of it. Thus, the color of a salt in solution was assumed to be made up of the different colors of the ions and the un-ionized molecule. Later work showed that ionization changes do not affect the color of the substance. Reference may be made here to a detailed review of these relations published by J. Lifschitz (Sammlung chemischer... 

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