Ternary metal complexes

Type IV includes chiral phases that usually interact with the enantiomeric analytes through the formation of metal complexes. There are usually used to separate amino acid enantiomers. These types of phases are also called ligand exchange phases. The transient diastereomeric complexes are ternary metal complexes between a transitional metal (usually Cu +), an amino acid enantiomeric analyte, and another compound immobilized on the CSP which is able to undergo complexation with the transitional metal (see also the ligand exchange section. Section 22.5). The two enantiomers are separated based on the difference in the stability constant of the two diastereomeric species. The mobile phases used to separate such enantiomeric analytes are usually aqueous solutions of copper (II) salts such as copper sulfate or copper acetate. To modulate the retention, several parameters—such as the pH of the mobile phase, the concentration of the copper ion, or the addition of an organic modifier such as acetonitrile or methanol in the mobile phase—can be varied. 

LEC separation is based on the formation of labile ternary metal complexes in the stationary phase ... 

The literature on arene - arene interactions in ternary metal-ion complexes, as reviewed in Section 3.2.3, indicates that these interactions are generally enthalpy-driven and counteracted by a reduction... 

Metal-induced reductive dimerization of carbonyl compounds is a useful synthetic method for the formation of vicinally functionalized carbon-carbon bonds. For stoichiometric reductive dimerizations, low-valent metals such as aluminum amalgam, titanium, vanadium, zinc, and samarium have been employed. Alternatively, ternary systems consisting of catalytic amounts of a metal salt or metal complex, a chlorosilane, and a stoichiometric co-reductant provide a catalytic method for the formation of pinacols based on reversible redox couples.2 The homocoupling of aldehydes is effected by vanadium or titanium catalysts in the presence of Me3SiCl and Zn or A1 to give the 1,2-diol derivatives high selectivity for the /-isomer is observed in the case of secondary aliphatic or aromatic aldehydes. 

Iron(III)-catalyzed autoxidation of ascorbic acid has received considerably less attention than the comparable reactions with copper species. Anaerobic studies confirmed that Fe(III) can easily oxidize ascorbic acid to dehydroascorbic acid. Xu and Jordan reported two-stage kinetics for this system in the presence of an excess of the metal ion, and suggested the fast formation of iron(III) ascorbate complexes which undergo reversible electron transfer steps (21). However, Bansch and coworkers did not find spectral evidence for the formation of ascorbate complexes in excess ascorbic acid (22). On the basis of a combined pH, temperature and pressure dependence study these authors confirmed that the oxidation by Fe(H20)g+ proceeds via an outer-sphere mechanism, while the reaction with Fe(H20)50H2+ is substitution-controlled and follows an inner-sphere electron transfer path. To some extent, these results may contradict with the model proposed by Taqui Khan and Martell (6), because the oxidation by the metal ion may take place before the ternary oxygen complex is actually formed in Eq. (17). 

Schindler, P. W. (1990), "Co-Adsorption of Metal Ions and Organic Ligands Formation of Ternary Surface Complexes", in M. F. Jr.. Hochelia and A. F. White, Eds., Mineral-Water Interface Geochemistry, Mineralogical Soc. of America, Washington, DC, 281-307. 

Owing to their numerous actual and potential applications, several ternary and complex systems of these metals, especially of aluminium, have been investigated a few examples of the systematics of Al-Me-X alloys are presented in 5.18 and in Fig. 5.41. Recent contributions to this subject have been given with the study of the systems R-Al-Cu (Riani et al. 2005, and references there in). These rare earth alloys, characterized by the formation of several intermediate phases, are interesting also as raw materials for the preparation of amorphous alloys. Regularities in the trends of their properties have been underlined. The experimental and calculated data relevant to the binary systems Al-Fe, Al-Ni and Fe-Ni have been examined and discussed in a paper concerning the assessment of the ternary Al-Fe-Ni system (Eleno et al. 2006). 

A route for designing Gd(HI) complexes whose relaxivity depends on the presence of lactate, is provided by the ability shown by some hexa- or hepta-coordinate chelates to form ternary complexes with a wide array of anionic species (154-161). The interaction between the coordinatively unsatured metal complex and lactate involves the displacement of two water molecules coordinated to Gd(III) ion with the two donor atoms of the substrate, thus leading to a marked decrease in the relaxivity. Lactate is a good ligand for Gd(IH) ion because it can form a stable 5-membered ring by using the hydroxo and carboxylic oxygen donor atoms (Fig. 19). 

This volume summarizes recent results of some of the leading investigators in trahsition metal hydride research. Readers interested in more extensive background material are urged to consult some of the many excellent books on the subject, such as Transition Metal Hydrides edited by E. L. Muetterties (Marcel Dekker, Inc., New York, 1971), which covers covalent metal hydride complexes, and Metal Hydrides edited by W. M. Mueller, J. P. Blackledge, and G. G. Libowitz (Academic, New York, 1968), which comprehensively covers work in binary and ternary metal hydrides. Also available in the covalent metal hydride area are excellent reviews by Ginsberg [Transition Metal Chemistry (1965) 1,112], and Kaesz and Saillant [Chemical Reviews (1972) 72, 231]. In this book we have not tried to be comprehensive rather, our purpose is to update recent developments in both major areas of metal hydride research. 

Binary [M(OH2)J"+ entities are not known in crystal hydrates for x > 9 (indeed no ML, (L monodentate) has yet been characterized178), but ternary aquo complexes are known in which the coordination number of the metal ion is 10, 11 or 12 (Table 5).178 183 The [M(OH2)7]"+ unit does not appear to have been characterized crystallographically, but again ternary aquo complexes of this coordination number exist, e.g. [U02(0H2)5]2+ in the salt U02(C104)2 7H20.11... 

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