Isomerism in Metal -Complexes

Linkage isomerism in metal complexes. J. L. Burmeister, Coord. Chem. Rev., 1968. 3. 225-245... 

Introduction 231 Fundamental concepts 233 Electronic structure of transition-metal ions 235 Structural characteristics necessary for complex formation 240 Preparation of metal-complex colorants 248 Isomerism in metal-complex dyes 260 Stability of metal-complex dyes 261 Chromium-related problems in the mordant dyeing of wool 268 References 277... 

A recurring theme throughout all the reported work on isomerism in metal complexes of tridentate azo compounds is the facility with which individual isomers revert to equilibrium mixtures in solution at elevated temperatures. Since these are the very conditions under which most metal complex dyes are applied, little technical application can be seen for the phenomenon of isomerism on dyes of this type. Nonetheless, the subject is of considerable theoretical interest and merits inclusion in this chapter on those grounds alone. 

Isomerism in metal complexes of tridentate azo compounds has been attributed to a number of factors and in the interest of clarity these will first be described in broad terms and then discussed in more detail. 

Na—Np isomerism Perhaps the most immediately obvious source of isomerism in metal complexes of tridentate azo compounds is the involvement of different nitrogen atoms of the azo group in coordination to the metal. This is not relevant in the case of symmetrical azo compounds but two structurally isomeric metal complexes (79) and (80) are conceivable for unsymmetrical azo compounds. These have been designated by Pfitzner78 as Na and Np isomers. 

Table 3 Isomerism in Metal Complexes of Tridentate Azo Compounds ...

Linkage isomerism in metal complexes was discovered in 1894 by Jorgensen.1 He prepared and characterized the nitrito... 

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