Water metal complex catalysts

Proteins are water-soluble biopolymers with a huge number of potential donor atoms and coordination sites which could make them useful carriers of metal complex catalysts. Indeed, a few successful attempts can be found in the literature [139] but often the interaction of proteins and metal complexes lead to a loss of catalytic activity [140]. This was not the case with human serum albumin (HSA) which formed a stable and active catalytically active complex with [Rh(acac)(CO)2]. In the hydroformylation of 1-octene and styrene the selectivity towards aldehydes was excellent, moreover styrene reacted with high regioselectivity (b/1 = 19). The activity... 

The general principle of two-phase catalysis in polar solvents, for example, in water, is shown in the simplified diagram of Fig. 1. The metal complex catalyst, which can be solubilized by hydrophilic ligands, converts the reactants A + B into the product C. The product is more soluble in the second than in the first phase and can be separated from the catalyst medium by simple phase separation. Excellent mixing and contacting of the two phases are necessary for efficient catalytic reaction, and thus the reactor is normally well stirred. 

Homogeneous catalysis by transition metal complexes almost always involves processes in which product-catalyst separation and catalyst recycling are important issues. For years, researchers have worked to find effective ways to isolate metal-complex catalysts in phases separate from those containing the catalyst, usually by anchoring the metal complex to a solid surface. As summarized by Driessen-Holscher, it is now evident that the method that has met with most practical success in this direction involves the use of multiple liquid phases. For example, rhodium complexes with water-soluble sulfonated ligands are used to catalyze alkene hydroformyla-tion, and the aqueous-phase catalyst and the organic products are easily separated as insoluble liquid phases. 

Organo metal complex catalyst for use with silicone water repellents, such as PROTOSIL GH. 

Fig. 16. A model water oxidation center composed of Nation membrane coated n-CdS semiconductor electrode and metal complex catalyst...

Figure 4. General principle of biphasic catalysis in water. The metal complex catalyst (C), which is solubilized by hydrophilic ligands, converts the substrates (in this case propene [S] and syngas [A-B]) to the products, which can be separated from the catalyst (medium) by phase separation.

In a technology involving two liquid phases, one of which contains the metal complex catalyst in solution, the idea of using water as one of the phases is not necessarily obvious. Hydroformylation, in 1972 - the time of Manasserfs idea -the most important application of homogeneous catalysis, utilized cobalt catalysts, whose handling sensitivity ruled out an aqueous phase. Or, as P. Cintas [20] wrote,... 

Earlandite structure, 849 Electrical conductivity metal complexes, 133 tetracyanoplatinates anion-deficient salts, 136 Electrical properties metal complexes, 133-154 Electrocatalysis, 28 Electrochemical cells, 1 Electrochemistry, 1-33 hydrogen or oxygen production from water coordination complex catalysts, 532 mineral processing, 831 reduction, 831 Electrodeposi (ion of metals, 1-15 mineral processing difficulty, 831 Electrodes clay modified, 23 ferrocene modified, 20 nation coated, 15 polymers on, 16 polyvinylferrocene coated, 19 poly(4-vinylpyridine) coated, 17 redox centres, 17 Prussian blue modified, 21 surface modified, 15-31 Electrolysis... 

The inverse (anti-Arrhenius) temperature dependence of the water solubility of metal complex catalysts based on poly(ethylene oxide). Such a dependence opens up the possibility of using these catalysts as models in developing concepts of thermoregulated catalysis and smart ligands. 

Shimizu. S. Shirakawa, S. Sasaki, Y. Hirai. C. Novel water-soluble calix[4]arene ligands with phosphane-con-taining groups for dual functional metal-complex catalysts ... 

Metal complex catalysts allowed under mild conditions several reactions, which were previously unknown in chemistry, viz., reduction of molecular nitrogen to hydrazine and ammonia, alkane activation and oxidation, water photodecomposition, etc. 

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