Organometallic compounds, aryl

The transmetallation of various organometallic compounds (Hg, Tl, Sn, B, Si, etc.) with Pd(II) generates the reactive cr-aryl, alkenyl, and alkyl Pd compounds. These carbopalladation products can be used without isolation for further reactions. Pd(II) and Hg(II) salts have similar reactivity toward alkenes and aromatic compounds, but Hg(II) salts form stable mercuration products with alkenes and aromatic rings. The mercuration products are isolated and handled easily. On the other hand, the corresponding palladation products are too reactive to be isolated. The stable mercuration products can be used for various reactions based on facile transmetallation with Pd(II) salts to generate the very reactive palladation products 399 and 400 in rim[364,365]. 

In Grignard reactions, Mg(0) metal reacts with organic halides of. sp carbons (alkyl halides) more easily than halides of sp carbons (aryl and alkenyl halides). On the other hand. Pd(0) complexes react more easily with halides of carbons. In other words, alkenyl and aryl halides undergo facile oxidative additions to Pd(0) to form complexes 1 which have a Pd—C tr-bond as an initial step. Then mainly two transformations of these intermediate complexes are possible insertion and transmetallation. Unsaturated compounds such as alkenes. conjugated dienes, alkynes, and CO insert into the Pd—C bond. The final step of the reactions is reductive elimination or elimination of /J-hydro-gen. At the same time, the Pd(0) catalytic species is regenerated to start a new catalytic cycle. The transmetallation takes place with organometallic compounds of Li, Mg, Zn, B, Al, Sn, Si, Hg, etc., and the reaction terminates by reductive elimination. 

Organometallic compounds contain a carbon-metal bond They are named as alkyl (or aryl) derivatives of metals... 

It is notable that the preparation of alkyl and aryl derivatives from Pb starting materials always results in Pb organometallic compounds. The only well-defined examples of Ptf ... 

Grignard reagents are a very important class of organometallic compounds. For their preparation an alkyl halide or aryl halide 5 is reacted with magnesium metal. The formation of the organometallic species takes place at the metal surface by transfer of an electron from magnesium to a halide molecule, an alkyl or aryl radical species 6 respectively is formed. Whether the intermediate radical species stays adsorbed at the metal surface (the A-modelf, or desorbs into solution (the D-model), still is in debate ... 

Phthalic anhydride also shows the ability to inhibit thermal destruction of polyolefins [21]. Among the organometallic compounds may be quoted organotin compounds R2Sr(OR )2, where R2 means alkyl, aryl, or cycloalkyl OR means alkoxyl, acyl, or R2Sn(CH2COORi)2, where Rj—Ci—Cm means alkyl, allyl, or benzyl Ro represents chloro-, mono-, or triorga-notin mercaptans [22,23]. 

Common metallo-organic alkyls, alicyclic, and aryl compounds and their relevant properties are listed in Table 4.1 l l Many additional organometallic compounds are available commercially as listed in Ref 7. 

Organometallic compounds can be hydrolyzed by acid treatment. For active metals such as Mg, Li, and so on, water is sufficiently acidic. The most important example of this reaction is hydrolysis of Grignard reagents, but M may be many other metals or metalloids. Examples are SiRs, HgR, Na, and B(OH)2- Since aryl Grignard and aryllithium compounds are fairly easy to prepare, they are often used to prepare salts of weak acids, for example,... 

Other reactions of aryl organometallic compounds are treated with their aliphatic analogs Reactions 12-24-12-34. 

Coupling of Organometallic Compounds with Aryl Halides, Ethers, and Carboxylic Esters... 

Coupling of organometallic compounds with aryl halides, ethers, and... 

Reaction of aryl organometallic compounds with halogens Aryl halide exchange halo-denitration halo-dehydroxylation Reaction between diazonium salts and iodide ion Heating of diazonium fluoroborates (Schiemann)... 

Metallation of alkyl or aryl halides with organometallic compounds... 

The most widely used route to organoboranes is hydroboration, introduced in Section 4.5.1, which provides access to both alkyl- and alkenylboranes. Aryl-, methyl-, allylic, and benzylboranes cannot be prepared by hydroboration, and the most general route to these organoboranes is by reaction of an organometallic compound with a halo- or alkoxyboron derivative.1... 

It occurs with the alkyls, aryls or acetylides of metals more electropositive than magnesium, but including Grignard reagents, and is often carried out by adding a solution of the organometallic compound in an inert solvent to a large excess of powdered, solid C02 it is a particularly useful method for the preparation of acetylenic acids. The Kolbe-Schmidt reaction (p. 291) is another example of carbanion carbonation. 

Aryl Migrations in Organometallic Compounds of the Alkali Metals, 16, 167... 

Diastereoselective addition of a wide range of Grignard reagents to C -alkyl and C-aryl-A-[a.-phenyl- or u-methyl-j3-(benzyloxy)ethyl nitrones is determined by the presence of a stereogenic A -substituent (136, 137). High diastereoselectiv-ity in the addition of organometalic compounds to A-(( i-methoxyalkyl) nitrones can be explained by a simple chelation model (Scheme 2.132) (136). 

The catalyst component consists of halides of IV-VIII group elements having transition valence and the cocatalysts are organometallic compounds like alkyls, aryls and hydrides of group I-IV metals. Although there are hundreds of such catalyst cocatalyst systems listed in table below. Systems based on the organoaluminium compounds such as triethyl aluminium (AlEt3) or diethyl aluminium chloride... 

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