Metal complexes, volatile

Preparation and Properties of Organophosphines. AUphatic phosphines can be gases, volatile Hquids, or oils. Aromatic phosphines frequentiy are crystalline, although many are oils. Some physical properties are Hsted in Table 14. The most characteristic chemical properties of phosphines include their susceptabiUty to oxidation and their nucleophilicity. The most common derivatives of the phosphines include halophosphines, phosphine oxides, metal complexes of phosphines, and phosphonium salts. Phosphines are also raw materials in the preparation of derivatives, ie, derivatives of the isomers phosphinic acid, HP(OH)2, and phosphonous acid, H2P(=0)0H. 

Many transition metal complexes dissolve readily in ionic liquids, which enables their use as solvents for transition metal catalysis. Sufficient solubility for a wide range of catalyst complexes is an obvious, but not trivial, prerequisite for a versatile solvent for homogenous catalysis. Some of the other approaches to the replacement of traditional volatile organic solvents by greener alternatives in transition metal catalysis, namely the use of supercritical CO2 or perfluorinated solvents, very often suffer from low catalyst solubility. This limitation is usually overcome by use of special ligand systems, which have to be synthesized prior to the catalytic reaction. 

The growing interest in volatile silyl-metal complexes for chemical vapor deposition reactions should also be mentioned. This technique is extremely useful for the preparation of silicide films in microelectronic devices. Further examples of applications of silicon-metal compounds are given in the appropriate sections. 

Of course, commercially available transition metal complexes are stable at room temperature because they have achieved an 18-electron noble gas-like electronic configuration. Thus, molecules like iron pentacarbonyl [Fe(CO)s], ferrocene [Fe(C5H5)2], as well as piano-stool complexes such as C5H5Co(CO)2 are chemically quite inert. In order to study bimolecular reactions, it is necessary to first prepare unsaturated complexes. For studies using molecular beams, one approach is through photolysis of a stable volatile precursor in a supersonic nozzle. 

Formation of 2-propanol and propene was confirmed by GC/MS. Chemisorption of Ti(0 Pr)4 is therefore suggested to be a consequence of nonhydrolytic condensation of the 2-propoxide ligands, which generates V-O-Ti bridges in the absence of surface hydroxyl groups. After removal of volatiles and desorption of physisorbed metal complexes, analysis reveals the presence of two equiv. Ti per V site on the surface, Table 1 (experiments 3 and 4). 

For generation of acidic conditions, a non-volatile acid such as citric acid (12.7), or an acid donor such as ammonium tartrate (12.8) or ammonium sulphate, is preferred. An acid or acid donor is not used with 1 2 metal-complex dyes of high neutral-dyeing affinity,... 

The formation of volatile chlorotrimethylsilane is a very clean synthetic pathway to prepare several metal complexes. Various trimethylsilyl derivatives of sulfur, selenium, and tellurium have been described. 

On the other hand, if one looks at gas phase electron transfer we find that it s dominated by small molecules and nonmethyl molecule and the system is quite remote from what we see in solution (H ions, and so forth). And I do wonder whether people will turn their attention to using, for example, organo-metallic complexes, many of which are volatile and unstable in the gas phase. 

Imidazolium salts that can be prepared by the first procedure, the alkylation of imidazole, are easy to obtain and often used for metal complex synthesis. Potassium imidazolide is reacted with the first equivalent of alkyl halide in toluene to give the 1-alkylimidazole. Subsequent alkylation in 3-position is achieved by addition of another equivalent of alkyl halide [Eq. (2)]. " A variant of this approach employs commercially available A-trimethylsilyl imidazole with 2 equiv of an alkyl chloride, under elimination of volatile MesSiCl. The drawback of these simple routes is the fact that only primary alkyl halides can be reacted in satisfactory yields because secondary and tertiary alkyl halides give substantial amounts of elimination by-products. 

Metal reclamation from acid mine drainage and contaminated surface- and groundwater and wastewaters has been extensively studied. Technologies for metal removal from solution are based on the microbial—metal interactions discussed earlier the binding of metal ions to microbial cell surfaces the intracellular uptake of metals the volatilization of metals and the precipitation of metals via complexation with microbially produced ligands. 

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