Polynuclear complexes in solution

Oxidation-Reduction Photochemistry of Polynuclear Complexes in Solution... 

Topics which have formed the subjects of reviews this year include photosubstitution reactions of transition-metal complexes, redox photochemistry of mononuclear and polynuclear" complexes in solution, excited-state electron transfer processes, transition-metal complexes as mediators in photochemical and chemiluminescence reactions, lanthanide ion luminescence in coordination chemistry, inorganic photosensitive materials," and photocatalytic systems using light-sensitive co-ordination compounds. Reviews have also appeared on the photoreduction of water.Finally, various aspects of inorganic photochemistry have been reviewed in a single issue of the Journal of Chemical Education. 

Piguet C. Five thermodynamic describers for addressing serendipity in the selRassembly of polynuclear complexes in solution. Chem Commun. 2010 46 6209-6231. 

The great recent development in electrochemical techniques will certainly be helpful for the study of redox processes of a metal which can occur in so many oxidation states. Multinuclear NMR spectrometers will allow increased use of 51V resonance as a routine method for the characterization of complexes in solution. Other recent developments are the study of polynuclear complexes, metal clusters (homo and hetero-nuclear) and mixed valence complexes, and it can be anticipated that these topics will soon become important areas of vanadium coordination chemistry, although the isolation of compounds with such complex... 

The same three spectrophotometric reagents were compared for their abilities to differentiate mono- and polynuclear hydroxy-aluminium complexes in solutions typical of those used in phytotoxicity studies (Parker et al., 1988b). Methods based upon each of the three reagents yielded estimates of the mononuclear aluminium fraction of adequate precision for most purposes. Studies using ferron demonstrated its utility for characterising the non-mononuclear aluminium fraction using kinetic analyses. The ferron spectrophotometric procedure was preferred for its simplicity, level of precision and moderate rate of reaction with aluminium. 

Structure determinations of polynuclear complexes in aqueous solutions are summarized in Table VIII 202-222). 

Chemisorption is very pronouneed if the radionuelide is able to react with the surface. An example is the sorption of hydroxo complexes of tri- and tetravalent elements by the silanol groups on glass surfaces. Sorption increases with the formation of mononuclear hydroxo complexes in solution and deereases with the eondensation to polynuclear complexes at higher pH values. Several measures may be taken to suppress ion exchange or chemisorption of traces of radionuclides on glass surfaees ... 

The fraction of polynuclear complexes in a solution decreases on dilution. 

The metal component of catalysts, solvent selection, and reaction concentration can influence aggregation and affect reactivity. The titanium catalyst 13 forms monomeric complexes in solution, but the analogous zirconium catalyst 14 forms polynuclear aggregates (Figure 9.7) this may explain why the chirality induced by oxidation of the sulfides is opposite for these two catalysts [23]. 

OEL/HEL] Oelkers, E. H., Helgeson, H. C., Triple-ion anions and polynuclear complexing in supercritical electrolyte solutions, Geochim. Cosmochim. Acta, 54, (1990), 727-738. Cited on pages 595, 596. 

There is a trend towards the formation of polynuclear complexes in the solutions of oxocompounds of Group V of the Periodic Table in molten salts,... 

DAV/ZAB] Davydov, Y. P., Zabrodskii, V. N., Hydrolysis of zirconium(lV) with the formation of mono- and polynuclear hydroxy complexes in solutions, Vestsi Akad. Navuk BSSR, Ser. Khim. Navuk, 2, (1987), 3-8, in Russian. Cited on pages 101, 102, 104, 106, 107,333,404. 

Davydov, Yu. P., Toropov, I. G., Hydrolysis of thorium(4+) cations with formation of polynuclear hydroxo complexes in solutions, Dokl. Akad. Nauk Belarusi, 36, (1992), 229-233, in Russian. Cited on page 593. 

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

Figure 1.4 shows distribution of Ag(I)-thiocyanide complexes in solutions in which both mono- and polynuclear complexes can be found. Here, molar fractions... 

In the foregoing it has been assumed that the complex species does not contain more than one metal ion, but under appropriate conditions a binuclear complex, i.e. one containing two metal ions, or even a polynuclear complex, containing more than two metal ions may be formed. Thus interaction between Zn2+ and Cl ions may result in the formation of binuclear complexes, e.g. [Zn2Cl6]2-, in addition to simple species such as ZnCl3 and ZnCl -. The formation of bi- and poly-nuclear complexes will clearly be favoured by a high concentration of the metal ion if the latter is present as a trace constituent of a solution, polynuclear complexes are unlikely to be formed. 

---