Solubility metal complexes

Progress and prospects in hydrogenation, hydrogenolysis, and desulfurization of thiophenes with soluble metal complexes 98ACR109. 

To this category belong, e.g., homogeneous photocatalytic systems based on soluble metal complexes or organic dyes as photocatalysts. Instructive examples are photoreactions assisted by heteropolyacids (HPAs), transition meal complexes with carbonyl, phosphine or some other ligands, and metal porphyrins. 

The most frequently used organic supports are polystyrene and styrene-divinylbenzene copolymer beads with functional groups such as diphenylpho.sphine covalently bonded. The polymer-anchored catalyst complex can then be obtained, for example, by displacement of a ligand already co-ordinated to a soluble metal complex (Cornils and Herrmann, 1996) ... 

When natural or synthetic complexing agents are added, soluble metal complexes may form. 

The importance of heteroatom removal from crude oil feedstocks has therefore directed most of the R D investments toward the design of more efficient heterogeneous catalysts for the reactions in Equations (12), (13), (14), (15). A considerable contribution to a better understanding of the HDS and HDN mechanism has been provided by homogeneous studies involving soluble metal complexes.161,162... 

Solvent-soluble metal complex azo black dyes are used in both industrial ink jet printing and hot melt ink jet printing. Cl Solvent Black 35 (61) is a typical dye.48... 

The Rate Constants (298 K) for the on and off Reactions of NO and CO with certain Water Soluble Metal Complexes in Aqueous Solution... 

Analogously, the SAPC catalyzed hydroformylation reaction was carried out using other water-soluble metal complexes of Pt and Co. Pt complexes in the presence of an Sn co-catalyst underwent hydrolysis of the Pt-Sn bond, which led to lower reaction selectivity. With the corresponding Co catalyst, good hydroformylation selectivities and conversions could be achieved, provided excess phosphine was used. Other authors performed hydrogenation of a,(3-unsaturated aldehydes using SAPC, and Ru and Ir water-soluble complexes. 

Photo-electrochemical (PEC) processes can produce hydrogen in one step - splitting water by illuminating a water-immersed semiconductor with sunlight. There are two types of photo-electrochemical processes. The first uses soluble metal complexes as catalysts. When these complexes dissolve, they absorb solar energy and produce an electrical charge that drives the water splitting reaction. This process mimics photo-synthesis, however, currently there is minimal experience in this process. 

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. 

A wide range of soluble metal complexes has proved to exert catalytic activity in hydrogenation of unsaturated molecules. Most attention, however, has focused on Group Vm elements since they give rise to the most active catalytic systems. 

Since the ligand is basic, various protonated species may occur in solution. Specifically, if Cl is thg total concentration of ligand in solution then, ignoring any small amount present as any water-soluble metal complex, and omitting charges for the sake of generality ... 

Our knowledge concerning soluble metal complexes with sulfide ions as ligands has increased considerably during the last two decades and this kind of Compound is still of topical interest. Some of the reasons for this are the development of a very flexible and fascinating structural chemistry of multinuclear metal-sulfur complexes, the fact that the active sites of some electron transfer proteins contain metal ions and labile sulfur,41,42 and also the relation of metal-sulfur cluster compounds to some heterogeneous catalysts. In addition, apart from the numerous binary and ternary sulfides which occur in nature, we have at our disposal a rich solid state chemistry of metal sulfides, which has been reviewed elsewhere and will be excluded here.43"17... 

Sposito, G., Holtzclaw, K. M., and Baham, J. (1976). Analytical properties of the soluble, metal-complexing fractions in sludge-soil mixtures II. Comparative structural chemistry of fulvic acid. Soil Sci. Soc. Am. J. 40, 691-697. 

Bhanage BM, Shirai M, Arai M et al (1999) Multiphase catalysis using water-soluble metal complexes in supercritical carbon dioxide. Chem Commun 14 1277-1278... 

The classic method for carrying out catalytic oxidations of hydrocarbon substrates has involved the use of the hydrocarbon itself as solvent and trace amounts of hydrocarbon-soluble metal complexes, such as metal stearates, naph-thenates, or acetylacetonates, as catalysts. These reactions were generally carried out to low conversions to avoid excessive by-product formation. Catalysis involved redox reactions of the metal catalyst with intermediate hydroperoxides. 

Fancy DA, Denison C, Kim K, et al. Scope, limitations and mechanistic aspects of the photo-induced cross-linking of proteins by water-soluble metal complexes. Chem Biol 2000 7 697-708. 

The other approach, resolution of a racemic mixture, is also used in many industrial processes. Here physical resolution (i.e., resolution by crystallization of a diastereomeric derivative) is in general the favored method. However, kinetic resolution in principle can also be used for separating out two enantiomers. Although kinetic resolution involving a soluble metal complex catalyst has yet to be widely practiced, the potential importance of such an approach is significant (see Section 9.3.5). 

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