Organometallic complexes solubility

Odta — see Acetic acid, octamethylenediaminetetra-Optical resolution amine metal complexes, 25 Ore-forming solutions metal sulfides, 525 Organometallic complexes solubility... 

A group of water-soluble tertiary phosphines that can be used as ligands to synthesize organometallic complexes soluble in aqueous solution are shown in Fig. 2. These individual phosphines can be synthesized by the sulfonation of triphenylphosphine, 1 (Eq. 16) (40) the reaction between... 

The solubility of most metals is much higher when they exist as organometallic complexes.4445 Naturally occurring chemicals that can partially complex with metal compounds and increase the solubility of the metal include aliphatic acids, aromatic acids, alcohols, aldehydes, ketones, amines, aromatic hydrocarbons, esters, ethers, and phenols. Several complexation processes, including chelation and hydration, can occur in the deep-well environment. 

Table 1 Hydrogenation of trans-Cmnamaldehyde using water-soluble organometallic complexes.

Nagata, T., Pohl, M., Weiner, H., and Finke, R.G., Polyoxoanion-supported organometallic complexes carbonyls of Rhenium(I), Iridium(I), and Rhodium(I) that are soluble analogs of solid-oxide-supported M(CO) + and that exhibit novel M(CO)n+ mobility, Inorg. Chem., 36, 1366, 1997. 

Instead, native starch has been oxidized with H202 in the presence of soluble organometallic complexes to meet specific hydrophilic/hydrophobic properties needed for end-products to be used in paper, paint and cosmetic industries [79-... 

In periphery-functionalized dendritic catalysts, the functional groups at the surface determine the solubility and miscibility and thus the precipitation properties. Many dendrimers functionalized with organometallic complexes do not dissolve in apolar solvents, and the presence of multiple metal centers at the periphery facilitates precipitation upon addition of this type of solvent. It is emphasized that the use of dendrimer-immobilized catalysts with the goal of recovery through precipitation is worthwhile only if the tendency to precipitation of the dendritic system exceeds that of its non-dendritic equivalent. 

Alternatively, we have shown that CO2 can be used to induce miscibility of fluorocarbon-hydrocarbon mixtures (see Figure 1), even those involving polar compounds such as methanol (2). Fluorinated organometallic complexes have been well established to have significant solubility in supercritical CO2, and their use as catalysts in this medium is well developed (10). This allows the homogeneously catalyzed reaction to be carried out in the C02-expanded homogeneous solution. 

The Lo-Cat process, licensed by US Filter Company, and Dow/Shell s SulFerox process are additional liquid redox processes. These processes have replaced the vanadium oxidizing agents used in the Stretford process with iron. Organic chelating compounds are used to provide water-soluble organometallic complexes in the solution. As in the case of Stretford units, the solution is regenerated by contact with air. 

Some redox couples of organometallic complexes are used as potential references. In particular, the ferrocenium ion/ferrocene (Fc+/Fc) and bis(biphenyl)chromium(I)/ (0) (BCr+/BCr) couples have been recommended by IUPAC as the potential reference in each individual solvent (Section 6.1.3) [11]. Furthermore, these couples are often used as solvent-independent potential references for comparing the potentials in different solvents [21]. The oxidized and reduced forms of each couple have similar structures and large sizes. Moreover, the positive charge in the oxidized form is surrounded by bulky ligands. Thus, the potentials of these redox couples are expected to be fairly free of the effects of solvents and reactive impurities. However, these couples do have some problems. One problem is that in aqueous solutions Fc+ in water behaves somewhat differently to in other solvents [29] the solubility of BCr+BPhF is insufficient in aqueous solutions, although it increases somewhat at higher temperatures (>45°C) [22]. The other problem is that the potentials of these couples are influenced to some extent by solvent permittivity this was discussed in 8 of Chapter 2. The influence of solvent permittivity can be removed by... 

The mechanistic steps shown in Figs. 25 and 26 have been demonstrated with soluble organometallic complexes (4, 89-102). Some of the reactions have been shown to be truly parts of a catalytic cycle, and others were observed to produce stable products which were isolated and characterized (4). It should be kept in mind that organometallic chemistry studies generally involve reactions at low temperatures (<150°C), and reactions that do not proceed at these low temperatures could well occur at the higher... 

Many of these studies utilized noble metals such as Ir, Os, Rh, Ru, or Re, whereas others used more conventional metals such as Mn, Fe, Mo, or Co. The particular metal on which the observations were made is not important at this point. What is important is that all of the important steps required for direct sulfur removal and hydrogenation of thiophene and more condensed derivatives have been shown to occur with soluble metal complexes. Thus, organometallic complex chemistry can be of great value in elucidating the mechanisms involved in conventional HDS processes and perhaps can point the way to improved catalyst formulations. 

Nickel and vanadium in petroleum exist as soluble organometallic complexes that fall into two categories metal porphyrins and nonporphyrin metal complexes. Both the porphyrins and the nonporphyrins may be distributed over a wide boiling range (350-650°C+), reflecting significant variations in molecular weight, structure, and polarity. Metal porphyrins and nonporphyrin metal complexes also tend to precipitate as part of the asphaltene materia] to an extent that varies with the source of the crude oil. 

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