Promoted by transition metal

Abstraction of a halogen has been studied much less, but the order of reactivity is RI > RBr > RCl 3> RF. There are now many cases where free-radical reactions are promoted by transition metals. ... 

The oxidation of lipids can be promoted by transition metals, such as copper or haem proteins, by a process that... 

In homogeneous solutions NO disproportionation maybe promoted by transition metal complexes, and a variety of mechanisms seem to be available owing to the many possible modes of coordination. One example is the reaction of NO with nickel carbonyl shown in Eq. (35) (76),... 

The discovery of the polymerization processes promoted by transition metal catalysts and the foundation of macromolecular stereochemistry represents a major breakthrough in chemistry in the second half of this century. Since the first discoveries by Ziegler in Miilheim and Natta in Milan there has been an enormous development of fundamental and applied research that still continues... 

Carbonylations of olefins, acetylenes, halides, alcohols, amines, nitro compounds, etc., promoted by transition metal complexes are very important in both industrial and laboratory organic syntheses. The mechanisms of those reactions have been studied extensively, especially for those associated with commercial processes. " The research... 

Carbon Electrophiles with Dienes and Polyenes Promoted by Transition Metals... 

Despite the fact that carbon dioxide (C02) is used in a great number of industrial applications, it remains a molecule of low reactivity, and methods have still to be identified for its activation. Both thermodynamic and kinetic problems are connected with the reactivity of C02, and few reactions are thermodynamically feasible. A very promising approach to activation is offered by its coordination to transition metal complexes, as both stoichiometric reactions of C-C bond formation and catalytic reactions of C02 are promoted by transition metal systems. Efforts to enhance the yield of hydrogen in water gas-shift (WGS) reactions have also been centered on C02 interactions with transition metal catalysts. The coordination on metal centers lowers the activation energy required in further reactions with suitable reactants involving C02, making it possible to convert this inert molecule into useful products. 

Nishimoto S, Ide H, Nakamichi K, Otsuki N, Kagiya T (1983c) Radiation-induced reductive conversion of 5-bromo-6-hydroxythymine to thymine promoted by transition metal salts in deaerated aqueous solution. Chem Lett 1441-1444... 

Innovations in the chemistry of aromatic compounds have occurred by recent development of many novel reactions of aryl halides or pseudohalides catalysed or promoted by transition metal complexes. Pd-catalysed reactions are the most important [2,29], The first reaction step is generation of the arylpalladium halide by oxidative addition of halide to Pd(0). Formation of phenylpalladium complex 1 as an intermediate from various benzene derivatives is summarized in Scheme 3.1. 

There are several types of reactions of hydro silanes that are promoted by transition metal complexes. In addition to homodehydrocoupling, Eq. (1) and heterodehydrocoupling, Eq. (2) (this process is sometimes referred to as dehydrogenative coupling), and disproportionation, Eq. (3) (only one possibility is depicted), an additional process and one of the most popularly employed is the addition of a Si-H bond to a substrate that contains a multiple bond. The addition reaction is referred to as hydrosilylation and a generalized example is shown in Eq. (4). 

Homodehydrocoupling is only one reaction of hydrosilanes that is promoted by transition metal complexes. In the development of pre-catalysts... 

Carbon-heteroatom coupling reactions including carbonylation and carboxy-lation polycondensations, promoted by transition metal catalysts, are becoming a promising route for various types of new condensation polymer. 

Metal complexes of heterocyclic compounds display reactivities changed greatly from those of the uncomplexed parent systems. All of the -electron system(s) of the parent heterocycle can be tied up in the complex formation, or part can be left to take part in alkenic reactions. The system may be greatly stabilized in the complex, so that reactions, on a heteroatom, for example, can be performed which the parent compound itself would not survive. Orbital energy levels may be split and symmetries changed, allowing hitherto forbidden reactions to occur. In short, a multitude of new reaction modes can be made possible by using complexes dimerization of azirines with a palladium catalyst serves as a typical example (Scheme 81). A variety of other insertion reactions, dimerizations, intramolecular cyclizations, and intermolecular addition reactions of azirines are promoted by transition metals. 

Tire deoxygenation of CO2 promoted by transition metal complexes merits some special considerations. Both the reduction to CO as well the disproportionation to CO and COj will be discussed. 

There are now many cases where free-radical reactions are promoted by transition metals. 

Scission of HA can occur by free radicals under oxidative conditions, and is promoted by transition metal ions [179-181]. The exact proportion of total HA turnover contributed by free-radical scission in the vertebrate organism is not known. 

This review will focus upon the subset of interesting reactions involving the apparent cleavage of carbon-carbon single bonds promoted by transition metals under homogeneous conditions. An excellent previous review should also be referred to [ 1 ]. Reactions in the presence of heterogeneous catalysts or in the vapor phase with naked metal ions [2] are outside the scope of this review. Reactions breaking carbon-carbon double bonds, such as olefin metathesis, are not included herein. 

In the previous review [1] various reactions involving the cleavage of C-0 bonds in organic compounds activated by transition metal complexes were treated. The present review is mainly concerned with the later development in the C-0 bond activation with inclusion of essential concepts related to the C-O bond cleavage reactions promoted by transition metal complexes. 

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