Nickel complexes synthesis

Other Specialty Chemicals. In fuel-ceU technology, nickel oxide cathodes have been demonstrated for the conversion of synthesis gas and the generation of electricity (199) (see Fuel cells). Nickel salts have been proposed as additions to water-flood tertiary cmde-oil recovery systems (see Petroleum, ENHANCED oil recovery). The salt forms nickel sulfide, which is an oxidation catalyst for H2S, and provides corrosion protection for downweU equipment. Sulfur-containing nickel complexes have been used to limit the oxidative deterioration of solvent-refined mineral oils (200). 

Synthesis, characterization, and chemistry of core-modified porphyrins and their nickel complexes 97NJC691. 

Tetraaza macrocycles nickel complexes, 5, 5 synthesis, 2, 903 Tetraazaporphyrin, octaphenyl-metallation, 2, 858 Tetraazaporphyrins synthesis, 2, 857... 

Bora-2,5-cyclohexadienes have a much greater synthetic potential than is apparent from the examples given so far. This may be exemplified by two recent reactions. Reductive complex formation in the system Co(acac)3/COD/25/Mg/THF affords complex 51 via the organotin route (77) while an earlier synthesis used the cobaltocene route (60). Ni(COD)2 very cleanly forms the (Tj3-l,4,5-cyclooctenyl)nickel complex 52 (29). 

Although the copper mediated Ullmann reaction is a well known method for biaryl synthesis, drastic conditions in the range of 150-280 °C are required. Zerovalent nickel complexes such as bis(l,5-cyclooctadiene)nickel or tetrakis(triphenylphosphine)nickel have been shown to be acceptable coupling reagents under mild conditions however, the complexes are unstable and not easy to prepare. The method using activated metallic nickel eliminates most of these problems and provides an attractive alternative for carrying out aryl coupling reactions(36,38). 

The purpose of this review is to provide the reader with a scenario of what can be accomplished with nickel complexes. It is useful to do this via a series of broad schemes, hypothetical in some cases, which show the main reaction patterns, without considering mechanistic details. Examples will illustrate the various processes, but extension to other substrates or to different conditions often requires use of alternative ligands or solvents, or a change from a neutral complex to a cationic or anionic species, as indicated above. For references to syntheses with nickel see Baker et al. (10). For criteria for the synthesis of coordination compounds and stability of organotransition metal complexes in general, see references (11. 12). Organometallic literature has been collected periodically by Bruce (13). 

Nickel halides and nickel complexes resulting from oxidative addition can also give rise to subsequent replacement and insertion reactions. Replacement reactions have been described mainly with arylnickel halide complexes (examples 23, 29, and 31, Table III). Carbanionic species replace halide ions and can undergo coupling or insertion reactions. An example of application of a carbanionic reaction to the synthesis of a natural product is the coupling step between an aromatic iodo-derivative and an active methylene group to form cephalotaxinone (example 23, Table III). 

Biaryl synthesis from aryl halides is a more interesting reaction due to the value of these molecules and their difficult access by chemical methods. The first electrosyntheses were simultaneously done in 1979-80 by three groups [21-23] who used NiCljPPha (1-20%) as catalyst precursor in the presence of excess PPhs. Later, several groups investigated the use of bidentate phosphines like dppe associated with nickel in the synthesis of various biaryls, and notably 2,2 -bipyridine and of 2,2 -biquinoline from respectively 2-chloropyridine and 2-chloroquinoline [24], More recently new nickel complexes with l,2-bis(di-2-alkyl-phosphino)benzene have been studied from both fundamental and synthetic points of view [25]. They have been applied to the coupling of aryl halides. 

Kockerling, M. and Henkel, G. (2000) Synthesis and structure of [Ni4(S2C7Hio)4], the first tetranuclear cyclic nickel complex with bifunctional thiolate ligands and of the mononuclear precursor compound Na2[Ni(S2C7Hio)2]- 4MeOH. (PrOH)-Pr-i, Inorg. Chem. Commun., 3, 117-9. 

Rehmann [90] has employed ultrasound to improve the yield of polyphenylene, thought at one time to have a future as a conducting material. Using dibromobenzene and a nickel complex catalyst he investigated both bath and probe systems and found that sonication led to improved yield when compared to the conventional synthesis (i. e. reflux) and also had the advantage of allowing the use of a lower temperature (20 °C). 

Phenylmethylsilanediol, synthesis, 42 155 Phenylsilanetriol, monosodium salts, 42 169 4 -Phenyl-2,2 6, 2 -terpyridine bis nickel complex, 30 74 molecular structure, 30 74 PhjtfluorenyllSiOH, 42 197 (Ph(Me2N)C-=Nli], 37 59-65 orientation of imino ligand, 37 61-63 (PhMe SiljCSiH OH, 42 244-245, 248 (PhMe SiljCsiMeHlOH), 42 191 Phosphaalkenes acyclic, 33 338-353 butadienes, 33 346-349 cumulenes, 33 352... 

Le Narvor N, Robertson N, Weyland T, Kilbum JD, Underhill AE, Webster M, Svenstrup N, Becher J (1996) Synthesis, structure and properties of nickel complexes of 4,5-tetrathia-fulvalene dithiolates high conductivity in neutral dithiolate complexes. Chem Commun 1363-1364... 

Carbonylation of halides with tetramethyltin This nickel complex is the most efficient catalyst for the synthesis of methyl ketones by reaction of aryl halides with carbon monoxide and tetramethyltin in HMPT at 120°. No reaction occurs when tetraphenyltin is used. A typical reaction is formulated in equation (I). 

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