Alkyl Bond Formation

Although many pieces of work in which metal-alkyl a bonds are formed will be discussed later, particularly in the sections on fran -alkylation and oxidative addition, four sets of experiments do not really fit into these categories. 

Two involve formation of Hg-C bonds. Gas phase studies on MeHg have shown that the stability of its adduct, MeHgB , falls along the series of bases, B Ei N Et2NH i-PrCeHs EtCeHs MeCeHs C6H5I  

Cu-C bond formation has also been studied. Rate constants (second order at 25°C) have been measured for the reaction of copper(II) tetraglycine, [Cu(II)G4], with various radicals generated by pulse radiolysis  

The decay of the first two organocopper(III) species is pH dependent but that of the third is not, its rate constant being 0.5 0.2 s K 

Though TT-bonded intermediates are often postulated in reactions of coba-lamins and model B12 compounds, as was done by Espenson and Wang (see above), they remain elusive. Ramasami and Espenson propose reactions (19) and (20) to account for the reaction of a BF2-cobaloxime derivative and acrylonitrile. 

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Another example of transient formation of a palladacycle is the Pd-mediated ortho-alkylation and ipso-vinylation of aryl iodides depicted in Scheme 8.23. In this multicomponent reaction the ability of norbomene to undergo reversible arylation and palladacycle formation is exploited. This reaction also illustrates that aryl halides undergo oxidative addition to Pd faster than do alkyl halides, and that aryl-alkyl bond-formation by reductive elimination also proceeds faster than alkyl-alkyl bond-formation. The large excess of alkyl iodide used in these reactions prevents the formation of biaryls. Benzocyclobutenes can also be formed in this reaction, in particular when the alkyl group on the aryl iodide is sterically demanding or when a secondary alkyl iodide is used [161]. 

Aryl-Aryl and Aryl-Alkyl Bond Formation... 

Aromatic C(sp )—H C—H Activation Aryl-Alkyl Bond Formations.126... 

CARBONYL C(sp2)—H C—H ACTIVATION ACYL-ALKENYL AND ACYL-ALKYL BOND FORMATIONS... 

Aromatic C—H Alkylations, C(sph—Aryl-Alkyl Bond Formations.185... 

Alkene C—H Alkylations, C(sph—Alkene-Alkyl Bond Formations.188... 

Alkynyl C—H Alkylations, C(sp)—Alkynyl-Alkyl Bond Formations. .. 192... 

Metal-Alkyl Bond Formation and Fission Oxidative Addition and Reductive Elimination... 

The following paragraphs on aryl/aryl(het-eroaryl)- and aryl/alkyl-bond formation centre on organometallic mediated C-C coupling reactions. For want of space, certain methods have had to be omitted and only those most commonly used have been included. Indeed, in certain cases combina-... 

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