Nickel aryl compound

Nickel associated with 2,2 -bipyridine has also been studied and the low valent complexes obtained by electroreduction are very efficient catalysts in the dimerisation of aryl compounds [26]. In addition, they have been used in combination with the sacrificial anode process which allows the running of such... 

In the case of orthosubstituted aryl halides the corresponding arylnickel intermediate Ar2Nibpy is stable and should be oxidized to lead to the coupling product and regenerate the nickel(II) compound [27]. 

Stable aryl compounds of nickel(II) were first reported by Chatt and Shaw with the use of... 

Oxidative addition reactions to nickel(O) complexes are another well-developed synthetic method which affords mono and bis alkyl and aryl compounds (equation 148).1232-1239 The oxidative addition of a, ar -dichloro-p-xylene to [Ni(QjH4)(PPh3)2] gives the dinuclear nickel(II) complex t(PPh3)2ClNi(CH2C6H4CH2)NiCl(PPh3)2].124 ... 

A novel method for the introduction of a 3-aryl substituent into a cyclohexanone has been reported.63 This route uses the photocyclization of the thio-aryl compounds (90) to the cyclic products (91), which can be desulphurized by Raney nickel. This treatment partially reduces the carbonyl function but oxidation of the crude product affords high yields of the ketones (92). The mr triplet excited state is responsible for the transformation of 3-anilino-6-methyI-cyclohex-2-en-1 -one into 3,4-dihydro-5-hydroxy-4-methyl-1 -benzazocine.64... 

Many examples of alkene and alkyne insertion into metal-carbon bonds can also be found in the section on homogeneous catalysis. Other recent examples include the insertion of conjugated dienes into palladium-allyl bonds, olefin arylation in the presence of palladium acetate, and the reaction of ethylene with arylmagnesium halides in the presence of nickel chloride. Reaction of isocyanates with nickel-ethynyl compounds... 

In 1975, both Cassar [72] and Murahashi and coworkers [73] reported on the applications of palladium complexes to catalytic cross-coupling chemistry [74]. Initially, Cassar compared nickel and palladium complexes in the catalytic crosscoupling between aryl or alkenyl halides and terminal alkynes, and found that nickel-based compounds exhibited no catalytic activity. In contrast, [Pd(PPh3)4] enabled catalytic coupling reactions of various organic halides bearing C(sp )-X bonds as reactive functional groups, notably in the absence of any copper [75] additives (Scheme 1.20) [72]. 

As described above, nickel compounds are liable to afford the 7r-compIex with compounds having a carbon-carbon unsaturated bond such as olefins, acetylenes, allyl and aryl compounds, and further the nickel compounds are also liable to afford (T-compIexes with alkyl or aryl compounds. 

Perfluoroalkyl or -aryl halides undergo oxidative addition with metal vapors to form nonsolvated fluonnated organometallic halides and this topic has been die subject of a review [289] Pentafluorophenyl halides react with Rieke nickel, cobalt, and iron to give bispentafluorophenylmetal compounds, which can be isolated in good yields as liquid complexes [290] Rieke nickel can also be used to promote the reaction of pentafluorophenyl halides with acid halides [297] (equation 193)... 

This reaction is similar to 13-1 and, like that one, generally requires activated substrates. With unactivated substrates, side reactions predominate, though aryl methyl ethers have been prepared from unactivated chlorides by treatment with MeO in HMPA. This reaction gives better yields than 13-1 and is used more often. A good solvent is liquid ammonia. The compound NaOMe reacted with o- and p-fluoronitrobenzenes 10 times faster in NH3 at — 70°C than in MeOH. Phase-transfer catalysis has also been used. The reaction of 4-iodotoluene and 3,4-dimethylphenol, in the presence of a copper catalyst and cesium carbonate, gave the diaryl ether (Ar—O—Ar ). Alcohols were coupled with aryl halides in the presence of palladium catalysts to give the Ar—O—R ether. Nickel catalysts have also been used. ... 

Substantially more work has been done on reactions of square-planar nickel, palladium, and platinum alkyl and aryl complexes with isocyanides. A communication by Otsuka et al. (108) described the initial work in this area. These workers carried out oxidative addition reactions with Ni(CNBu )4 and with [Pd(CNBu )2] (. In a reaction of the latter compound with methyl iodide the complex, Pd(CNBu )2(CH3)I, stable as a solid but unstable in solution, was obtained. This complex when dissolved in toluene proceeds through an intermediate believed to be dimeric, which then reacts with an additional ligand L (CNBu or PPh3) to give PdL(CNBu )- C(CH3)=NBu I [Eq. (7)]. 

In a Kumada-Corriu reaction, an aryl halide is oxidatively coupled with a homogeneous nickel(ll)-phosphine catalyst [2], This species reacts with a Grignard reagent to give biaryl or alkylaryl compounds. Later, palladium-phosphine complexes were also successfully applied. By this means, stereospecific transformations were achieved. 

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