Preparing metal complexes

Furthermore, the complexes formed are also susceptible to further isocyanate insertions leading to product mixtures. [27] 

Tight Bite Angle N,0-Chelates. Amidates, Ureates and Beyond 377 -NaCI 

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Like graphite, C60 can be transformed into diamond, but the process requires less stringent conditions. It has also been found that Cso becomes a superconductor at low temperature. Another interesting characteristic of Cso is that when it is prepared in the presence of certain metals, the Cso cage can enclose a metal atom. In some cases, other materials can be enclosed within the C60 cage in a "shrink wrapped" manner to form "complexes" that are described as endohedral. It has also been possible to prepare metal complexes of Cso that contain metal-carbon bonds. A compound of this type is (C6H5P)2PtC60. 

Bidentate Schiff bases have been among those most used in preparing metal complexes. In the following subsections we shall describe the potentially bidentate ligands according to their donor atom set. 

Chemists have prepared metal complexes containing metal atoms/ions as a means to understand better the structure, chemical bonding, and properties of metals and metal ions. One of the first efforts to affix these metal complexes to a surface as a means to create a supported catalyst was reported by Ballard followed by reports collected by Yermakov, et al. and Basset et al. We distinguish here between metal complexes that contain zero-valent metals and those that show metal cations and we limit this review to complexes containing metal ions as others have published extensive reviews of zero-valent, metal clusters and their chemistryIn our previous three reviews on the chemistry of supported, polynuclear metal complexes, we described efforts to synthesize and characterize oxide-supported, metal complexes as adsorbents, catalysts and precursors to supported metal oxides. In one application of this technology, efforts were... 

Leonhardt and Mosbach prepared metal-complexing imprinted polymers by polymerising Co " complexes of N-vinyl imidazole and A-protected amino acids [14]. After work-up of the polymer and removal of the amino acid templates, the catalytic activities of the resulting imprinted metal-complexing polymers were evaluated by following the hydrolysis of the p-nitrophenyl esters of various amino acids. Assessment of the rate of hydrolysis revealed a clear preference for the substrates used as the templates. The polymers could be used several times without any deterioration of the catalytic activities and true turnover was observed. 

Figure 9.13 Stepwise coordination method to prepare metal complex molecular wire on Au.

Our attempts to prepare metal complexes in high oxidation states stabilized by other ligands capable of distributing the metal charge effectively have not yet been very successful. Complexes with cyanodithio-formate (Reaction 8) are rather insoluble (38). Complexes of p-hydroxy-... 

There are many coordination compounds with weakly coordinating ligands containing oxygen donors. These include ketones, aldehydes, esters, and some nitro compounds. Driessen and Groeneveld and Driessen et al. prepared metal complexes of these ligands through the reaction... 

One of the most prominent synthetic problems associated with preparing metal complexes bearing silylated ligands is that the sidechains are sensitive to water, and therefore susceptible to prematurely undergoing the hydrolysis and... 

Several different hut related experimental methods can be used to prepare metal complexes. Some of these are described in this chapter. The choice of method depends upon the system in question, and not all methods are applicable to the synthesis of a particular compormd. Finding a reaction that produces the desired compound in good yield is only the beginning. The next step is to find a suitable way to isolate the product from its reaction mixtare. Crystallization has been most frequently used. The more commonly used techniques include ... 

The direct reaction between an anhydrous salt and a liquid ligand can be used to prepare metal complexes. In many cases, the liquid ligand present in very large excess also serves as a solvent for the reaction mixture. One method, which can be used to synthesize metal ammines, involves the addition of a metal salt to liquid ammonia followed by evaporation to dryness. Evaporation occurs readily at room temperature, because ammonia boils at -33°C. The dry residue obtained is essentially the pure metal ammine. For example, [Ni(NH3)6]Cl2 can be prepared in this way by reaction (11). 

In systems that react slowly, it is often necessary to employ elevated temperatures and long reaction times in order to prepare desired coordination compounds. Alternatively, a catalyst may be used to increase the speed of a reaction. Catalysis has been used successfully in a few instances to prepare metal complexes. There are two types of catalysis heterogeneous catalysis takes place when the catalyst is in a different phase than that of the reactants homogeneous catalysis occurs when the catalyst and reacting materials are in the same phase. Examples of the use of heterogeneous and homogeneous catalysis in the synthesis of metal complexes are noted below. 

In addition, surface complexes are obtained through the formation of coordination complex of adatoms, i.e., atoms protruding from the terraces of the metal substrate and exhibiting the lowest possible coordination number with other surface atoms, with suitable ligands dissolved in solution (Fig. 5.5) [37, 38]. However, this fascinating method of preparing metal complexes on a metal surface has not been exploited in the frame of electroanalysis. 

Both monopyridyl and bipyridyl perfluorinated diarylethene ligands (ld(o) and 2(o)) have been used more recently to prepare metal complexes... 

Intermediates in Reactions.—Attempts to prepare metal complexes of thiirens resulted in the formation of complexes of thioketocarbenes instead. Treatment of 1,2,3-thiadiazoles and -selenadiazoles with di-iron enneacarbonyl gives thioketo- and selenoketo-carbene complexes. The formation of two carbene complexes from unsymmetrically substituted thia- or selena-diazoles suggests the intermediacy of a thiiren or seleniren complex. ... 

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