Nickel halide catalyst

Methanol can be hydroformylated with syngas (CO and H2) in the presence of a copper or nickel halide catalyst to give acetaldehyde. Reaction conditions are 350-400°F and 4000-6000 psi. 

With these catalysts molecular weights would, in the absence of chain termination reactions, increase directly with conversion, with Poisson distributions. Monomer transfer, which has been observed with the 7r-allyl nickel halide catalysts, would lead to lower values and a broadening of the distribution. 

C. Supported Nickel Halide Catalysts Nickel iodide, nickel bromide, and nickel chloride, based on various supports, like silica gel, kieselguhr, kaolin, pumice, and charcoal, were prepared by almost similar methods. The halides were prepared by dissolving nickel hydroxide in the minimum quantity of hydriodic acid, hydrobromic acid or hydrochloric acid. 

Nickel halide complexes with amines give mixtures of linear polymer and cychc trimers (30). Nickel chelates give up to 40% of linear polymer (31). When heated with ammonia over cadmium calcium phosphate catalysts, propargyl alcohol gives a mixture of pyridines (32). 

Significant synthetic applications of the nickel-salen catalysts are the formation of cycloalkanes by reduction of <>, -a-dihaloalkanes255,256 and unsaturated halides,257,258 the conversion of benzal chloride (C6H5CHC12) into a variety of dimeric products 259 the synthesis of 1,4-butanediol from 2-bromo- and 2-iodoethanol260 or the reduction of acylhalides to aldehydes261 and carboxylic acids.262... 

Examples of w-allylnickel-X compounds (X = anionic ligand) other than 77-allylnickel halides which have been used in combination with (alkyl)aluminum halides as olefin oligomerization catalysts are 7r-allyl-nickel acetylacetonate (11) (Section III), 7r-allylnickel aziridide (4, 56), and bis(7r-allyl)nickel (6) (59). In addition to ir-allylnickel halides, organo-nickel halides such as tritylnickel chloride (60, 61) and pentafluoro-phenylbis(triphenylphosphine)nickel bromide (62), or hydridonickel halides, e.g., trans-hydridobis(triisopropylphosphine)nickel chloride (12) (Section III), give active catalysts after activation with aluminum halides... 

The nickel carbonyl catalyst is preformed by passing a fast stream of CO through a two-phase system of aqueous NaOH (5M, 25 ml) and Me2CHCH2COMe (25 ml) containing TBA-HSO, (0.07 g, 0.2 mmol). Ni(CN)2 (0.11 g, 1.0 mmol) is added and the mixture heated at 60 °C for 3 h under CO (1 atmos.). The system is cooled to room temperature and the allyl halide (11.6 mmol) in Me2CHCH2COMe (20 ml) is added over 3 h and the mixture is then stirred under CO (1 atmos.) for 12 h. The aqueous layer is separated, washed with Et20 (2 x 25 ml) and acidified with sulphuric acid (3M). CAUTION. HCN may be evolved. The acidified solution is extracted with EtzO (4 x 25 ml), and the extracts are washed with H20 (20 ml), dried (MgS04) and evaporated to produce the acid. 

Predominantly cis-1,4-polybutadiene is produced by coordination polymerization with mixed catalysts.187,487,488 Three catalyst systems based on titanium, cobalt, or nickel are used in industrial practice. Iodine is an inevitable component in titanium-alkylaluminum sytems to get high cis content. Numerous different technologies are used 490,491 A unique process was developed by Snamprogetti employing a (Tr-allyl)uranium halide catalyst with a Lewis acid cocatalyst.492-494 This catalyst system produces poly butadiene with 1,4-ris content up to 99%. 

The carbonylation of allyl chloride with a nickel carbonyl catalyst appears to be the first useful example of an organic halide reaction to be reported (6). In alcohol solution at 50 atm pressure and 100°, mixtures of esters of 2- and 3-butenoic acid were obtained in about 50% yield with the 3-isomer predominating. Such high pressures and temperatures are probably not necessary for this reaction, however (7) ... 

Palladium catalyzes the carbonylation of allylic, vinylic, benzylic, and aromatic halides in alcohols to form esters under conditions similar to those required by the nickel carbonyl catalyst (11). The palladium-catalyzed reaction offers the advantage of not requiring the use of highly toxic and volatile nickel carbonyl, and perhaps higher catalyst activity, although accurate comparisons have not been made. Like the nickel reaction, the palladium reaction... 

The relative success of these nickel-based catalysts has led to generic complexes of the type TpxNiX (X = Cl, Br, F) being patented in this role,16 as were TpxNi(ri3-allyl),21 though these are significantly less active than the halide complexes. 

Vinyl and aryl halides have been electrochemically coupled using nickel complex catalysts and these methods have been reviewed previously825. 

The past decade has seen extensive development of cross-coupling reactions of organozinc compounds and organic halides catalyzed by nickel or palladium catalysts. Although nickel-based catalysts are more reactive with respect to the organic halide partner, the number of failures with these catalysts and the greater selectivity realized with palladium-based catalysts have resulted in the almost exclusive use of the latter group of catalysts for these reactions. 

The bis-triphenylphosphine nickel halides are not activated by tin (II) halides. However, the iodide, (03P)2Nil2, is an effective catalyst for the hydrogenation of methyl linoleate to the monoene stage. The bromide is less effective, and the chloride has very little catalytic power. None of these nickel compounds has much ability to bring about isomerization. The nickel compounds are unstable in alcoholic solutions, and the experiments reported in Table III were carried out in either benzene, tetrahydro-furan, or toluene. 

Soluble single species catalysts are also known, such as the bis(7r-allyl nickel halides) [7]. These can be prepared separately or in situ by reacting bis-allyl nickel (which is an ologomerization catalyst for butadiene but does not give high molecular weight polymer) with an equimolar quantity of nickel halide, and thus bears some resemblance to the catalysts from titanium subhalides and alkyl titanium halides. It is of interest to note that the active species is the monomeric form of the initiator as TT-complex with butadiene (XII) [61]. 

Certain catalysts, such as the 7r-allyl nickel halides, which are effective for butadiene, exist in dimeric form and are converted into active species by dissociation. Partial dissociation followed by addition of monomer to the active catalyst fragments would result in the rate of polymerization being proportional to [C2] [M], where C2 represents the dimeric catalyst species. 

From a retrosynfhetic viewpoint, N-aryl-l,2-diimine Ni precatalysts are synthesized by (i) reaction of 1,2 diimines with nickel halides from (ii) 1,2-diimine ligands which in turn are obtained by (iii) condensing 1,2-dicarbonyl substrates with two equivalents of primary aromatic amines, usually under acidic conditions [11]. In analogy, the synthesis of N-hetaryl 1,2 diimine catalysts starts from the corresponding substituted N-heterocyclic primary amines as the amine building blocks. The synthesis of three types of such heterocycles, N-amino-pyrroles, -indoles and -carbazoles, and their corresponding diimine derivatives is presented in the following sections. 

Using catalysis by palladium systems, allylic halides show little tendency to add. However, with nickel(O) catalysts [e.g., Ni(cod)2] allylic halides add to norbornene. in contrast to vinyl and aryl halides9. The palladium system also catalyzes the coaddition of alkynes and benzylic halides to strained bicyclic alkenes10- u. Thus, addition of methyl 2-[3-(chloromethyl)phenoxy]acetate and optically pure (S)-l-octyn-3-ol to norbornene, norbornadiene or 7-oxanorbornene 4 leads to diastereomeric adducts 5, used as precursors of interphenylene prostaglandin endoperoxides, in 34-58% yield. No diastereomeric ratios were reported. 

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