Reactions with metal complexes

Reactions 33 and 35 constitute the two principal reactions of alkyl hydroperoxides with metal complexes and are the most common pathway for catalysis of LPOs (2). Both manganese and cobalt are especially effective in these reactions. There is extensive evidence that the oxidation of intermediate ketones is enhanced by a manganese catalyst, probably through an enol mechanism (34,96,183—185). 

Such a broad range of classical elementary reactions of homogeneous catalysis with metal complexes, that can be facilitated by photons, make illumination of reaction solution a very useful instrument for substantial increase of the possibilities of homogeneous metal complex catalysis in organic synthesis. Particular examples of light-assisted syntheses will be given in section 3. 

Modification of clays with metal complexes containing chiral ligands can be used for the preparation of catalysts for asymmetric reactions. Since the modified clays have limited interlayer space, the interaction between chiral ligands and substrates can be enforced and this may enhance the selectivity.203,204... 

Furthermore, ir-arene complexes of transition metals are seldom formed by the direct reaction of benzene with metal complexes. More usually, the syntheses require the formation of (often unstable) metal aryl complexes and these are then converted to ir-arene complexes. The analogous formation of w-adsorbed benzene at a metal surface via the initial formation of ff-adsorbcd phenyl, merits more consideration than it has yet been given. It is to be hoped that the recognition and study of structure-sensitive reactions will allow more exact definition of the sites responsible for catalytic activity at metal surfaces. The reactions of benzene, using suitably labeled materials, may prove to be useful probes for such studies. 

Electroless deposition should not be confused with metal displacement reactions, which are often known as cementation or immersion plating processes. In the latter, the less noble metal dissolves and eventually becomes coated with a more noble metal, and the deposition process ceases. Coating thicknesses are usually < 1 pm, and tend to be less continuous than coatings obtained by other methods. A well-known example of an immersion plating process that has technological applications is the deposition of Sn on Cu [17] here a strong complexant for Cu(I), such as thiourea, forces the Cu(I)/Cu couple cathodic with respect to the Sn(II)/Sn couple, thereby increasing the thermodynamic stability in solution of thiourea-complexed Cu(I) relative to Sn(II). 

Hydroperoxide decomposing antioxidants. These are compounds that react with hydroperoxides without forming free radicals sulfides, phosphites, arsenites, thiophosphates, carbamates, and some metal complexes. Reactions with hydroperoxides can be either stoichiometric (typical of, for example, sulfides and phosphites) or catalytic (typical of chelate metal complexes). 

During the oxidative copperizing process, an o-hydroxyazo compound reacts with a copper(II) salt in the presence of hydrogen peroxide. Both methods broaden the scope of metal complexation reactions by extending the selection of suitable diazo components [8,9]. 

Solvent polarity effects are also seen in the formation of isomers of transition metal complexes. Reactions that give a mixture of cis and trans isomers can be tuned by careful choice of solvent to give one isomer in preference to the other. For example, with cis and trans- PUlLI.-SbCL (where H2L = A-benzoyl-A -propylthiourea), shown in Scheme 1.4 [29], the cis isomer is favoured in solvents of high polarity whereas the trans isomer is dominant in solvents of low polarity. These observations are in accordance with other related observations [30], and... 

It has been known for a long time that the decomposition of diazoalkanes can be catalyzed by transition metal complexes [493-496]. Carbene complexes were proposed as possible intermediates by Yates in 1952 [497]. However, because reactions of diazoalkanes with metal complexes tend to be difficult to control, it was not until 1975 [498] that stable carbene complexes could be directly obtained from diazoalkanes (Figure 3.19). 

VII. Other Reactions of Diynes with Metal Complexes. 199... 

OTHER REACTIONS OF DIYNES WITH METAL COMPLEXES... 

Figure 10. Reactions of cycloproparenes with metal complexes.

Cationic mononuclear metal complexes, reaction with anionic carbonyl clusters, 30 155-158... 

Neutral metal complexes, reaction with carbonyl metallates, 30 152-155 Neutrons... 

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