Addition reactions electrochemical

The syntheses and spectroscopic and electrochemical characterization of the rhodium and iridium porphyrin complexes (Por)IVI(R) and (Por)M(R)(L) have been summarized in three review articles.The classical syntheses involve Rh(Por)X with RLi or RMgBr, and [Rh(Por) with RX. In addition, reactions of the rhodium and iridium dimers have led to a wide variety of rhodium a-bonded complexes. For example, Rh(OEP)]2 reacts with benzyl bromide to give benzyl rhodium complexes, and with monosubstituted alkenes and alkynes to give a-alkyl and fT-vinyl products, respectively. More recent synthetic methods are summarized below. Although the development of iridium porphyrin chemistry has lagged behind that of rhodium, there have been few surprises and reactions of [IrfPorih and lr(Por)H parallel those of the rhodium congeners quite closely.Selected structural data for rr-bonded rhodium and iridium porphyrin complexes are collected in Table VI, and several examples are shown in Fig. 7. ... 

When the layer has electronic in addition to ionic conductivity, the electrochemical reaction will be partly or completely pushed out to its outer surface. In addition, other electrochemical reactions involving the solution components, particularly anodic oxygen evolution, can occur on top of the layer. 

Monomeric platinum(III) complexes have been observed frequently as transient species in electrochemical or pulse radiolysis studies and they are proposed as an intermediates in reductive elimination and oxidative addition reactions of platinum(IV) and platinum(II) respectively.382-388... 

In the application of XAS to the study of fuel cell catalysts, the limitations of the technique must also be acknowledged the greatest of which is that XAS provides a bulk average characterization of the sample, on a per-atom basis, and catalyst materials used in low temperature fuel cells are intrinsically nonuniform in nature, characterized by a distribution of particle sizes, compositions, and morphologies. In addition, the electrochemical reactions of interest in fuel cells take place at the surface of catalyst par-... 

Fhe electrochemical generation of alkyl radicals catalysed by square planar nickel complexes has been used to achieve radical-alkene addition reactions. Complex 64 was the catalyst of choice. Intramolecular cyclizations to give five raem-... 

Modern electrochemical methods provide the coordination chemist with a powerful means of studying chemical reactions coupled to electron transfer and exploiting such chemistry in electrosynthesis. In addition, the electrochemical generation of reactive metallo intermediates can provide routes for the activation of otherwise inert molecules, as in the reduction of N2 to ammonia,50 and for electrocatalyzing redox reactions, such as the reduction of C02 to formate and oxalate,51 the oxidation of NH3 to N02-,52 and the technologically important oxidation of water to 02 or its converse, the reduction of 02 to water.53 Electrochemical reactions involving coordination compounds and organometallic species have been extensively reviewed.54-60... 

Adipodinitrile is an intermediate for hexamethylenediamine, the amine component of nylon 66. The electrochemical process is economically superior to the synthesis of adipodinitrile from cyclohexanone. Today, it essentially competes with the addition reaction of HCN to butadiene. The total capacity of the electrochemical ADN synthesis is currently about 250,000 tonnes/year. The process is industrially fully developed. Recent work 34 347) is aimed at reducing the oxygen evolution potential at the anode in order to save further energy. 

The coupling reaction is perhaps the most useful among the different electrochemical reaction types, since it normally has few or no counterparts in conventional laboratory practice. It provides a simple and direct route to bifunctional dimeric compounds from monofunctional monomeric compounds. Anodic coupling processes are formally of two kinds, either a coupling-elimination or a coupling-addition reaction, as shown in Eq. (10) and (11). 

Electrochemical catalyst regeneration was tested for addition reactions of perfluoroalkyl halides 41b to a-methylstyrene 42 (Fig. 8) [96], Dimers 43 were isolated in 50% and 70% yield, respectively, using 6-10 mol% of Ni(bipy)Br2 as the catalyst in a divided cell at -1.2 V at a platinum cathode. Under these conditions the Ni(II) complex is first reduced to Ni(0). 

Fig. 23 Nickel-catalyzed electrochemically mediated reductive radical addition reactions...

Several electrochemically mediated Ni-catalyzed addition reactions with aryl halides were reported, but their mechanism is not fully clarified. Using 10 mol% of NiBr2 as a catalyst, heteroaryl halides were added to a, p-unsaturated carbonyl compounds affording (1-aryl carbonyl compounds in 15-86% yield [127]. These addition reactions seem to proceed rather by classical Ni(0)-Ni(II) or Ni(I)-Ni(III) catalytic cycles than by a radical catalysis mechanism. 

Unlike many other type of radical addition reactions, the product is most often an alkyl-cobalt(III) species capable of further manipulation. These product Co—C bonds have been converted in good yields to carbon-oxygen (alcohol, acetate), carbon-nitrogen (oxime, amine), carbon-halogen, carbon-sulfur (sulfide, sulfinic acid) and carbon-selenium bonds (equations 179 and 180)354. Exceptions to this rule are the intermolecular additions to electron-deficient olefins, in which the putative organocobalt(III) species eliminates to form an a,/ -unsaturated carbonyl compound or styrene353 or is reduced (under electrochemical conditions) to the alkane (equation 181)355. 

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