Complex alkyl-metal anions

All of the reactions described above use anionic alkyl metal complexes as stoichiometric reductants. Cationic zirconium catalyst 58 was shown to re-ductively cyclize a variety of 1,5-dienes to give both mono- and bicyclic silane products when H3SiPh was employed as the stoichiometric reductant (Scheme 10) [32]. Poor yields due to competing polymerization processes were observed when less substituted dienes were employed. It is likely that... 

The catalysis of the cleavage of carbon-halogen bonds by complexation with metal ions such as silver or mercuric ion is a well-known phenomenon. The compounds susceptible to this action are alkyl halides capable of forming car-bonium ions. The complexed anions such as in mercuric nitrate, mercuric perchlorate, or hydrated mercuric ion do not exhibit a simple relationship between their effect on the total rate and on the relative distribution of products stemming from water or the anion. This evidence is indicative of the following catalytic mechanism ... 

Neither the palladium nor nickel catalyst described will promote the carbonylation of saturated aliphatic halides as noted above. However, this reaction can be catalyzed with cobalt (17) or iron (77) and probably with manganese (18) carbonyl anion salts. These carbonyl anions are strongly nucleophilic species and readily displace halide or other good leaving groups from primary or secondary positions giving alkyl metal carbonyl complexes. 

Danusso s conclusion that the monomer is only weakly polarized in the complex must certainly be true for the stereospecific coordinated anionic catalysts, such as AlR3/TiCl3, which are used for a-olefin polymerization. If it were not so, then rapid termination would take place through hydride abstraction by the strongly polarized monomer. This appears to be the case when strongly acidic alkyl metal chlorides are used in catalysts. For example, low molecular weight polypropylene oils are obtained with RAlCl2/TiCla catalyst (308) and polyethylene oils are obtained with RjA Cla/TiC catalysts in reactive alkyl halide solvents (309). 

Carbonylate complexes have many useful synthetic applications. Typical reactions involve nucleophilic attack of the metal anion on a positive center (alternatively viewed as an electrophilic attack on the metal). The synthesis of ntctal alkyl complexes has been referred to earlier (fiqs. 15.46 and 15.47). Other examples include ... 

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