Phosphine complexes nickel

Alkyl- and aryl-pyridazines can be prepared by cross-coupling reactions between chloropyridazines and Grignard reagents in the presence of nickel-phosphine complexes as catalysts. Dichloro[l,2-bis(diphenylphosphino)propane]nickel is used for alkylation and dichloro[l,2-bis(diphenylphosphino)ethane]nickel for arylation (78CPB2550). 3-Alkynyl-pyridazines and their A-oxides are prepared from 3-chloropyridazines and their A-oxides and alkynes using a Pd(PPh3)Cl2-Cu complex and triethylamine (78H(9)1397). 

In addition to the neutral nickel/phosphine complexes used in the Shell Higher Olefins Process (SHOP), cationic Ni-complexes such as [(mall)Ni(dppmo)][SbF6] (see Figure 5.2-7) have attracted some attention as highly selective and highly active catalysts for ethylene oligomerization to HAOs [106]. 

Layered inorganic solids have been used for site isolation, for example, nickel phosphine complexes confined within the interlayer spaces of sepiolite have been used as olefin hydrogenation catalysts [63], and similarly there has been the encapsulation of metal complexes into zirconium phosphates [64], The principal idea is illustrated in Figure 5.8. The metal complex can be encapsulated by covalent means (a) or by non-covalent interactions (b). 

K. Tamao, S. Kodama, I. Nakajima, M. Kumada, A. Minato, and K. Suzuki, Nickel-phosphine complex-catalyzed Grignard coupling — II Grignard coupling of heterocyclic compounds, Tetrahedron, 38 3347-3354, 1982. 

Migration of organosilicon groups from metal to ligand is believed to be a key step in the mechanism of olefin hydrosilylation catalyzed by nickel-phosphine complexes (59), as shown in Scheme 1. (Substituents are omitted for clarity.)... 

Tetrakis(phenyldifluorophosphine)nickel-(0) could also be obtained, using arsenic trifluoride in the presence of catalytic amounts of antimony pentachloride, or zinc fluoride as fluorinating agents. Yields as high as 50% could be obtained, but sizable decomposition on the process of fluorination of the chlorophosphine nickel-(0) complexes in solution could not be entirely suppressed. The marked instability of zerovalent nickel-phosphine complexes in solution in organic solvents, even under strictly anhydrous and anaerobic conditions, has been noted by several workers (16,20), but is still lacking a detailed explanation. A closer examination of the system carbon tetrachloride-tetrakis(trichlorophosphine)nickel-(0) (23) showed the main pa h of the reaction to consist in the formation of hexachloro-ethane with conversion of zerovalent into bivalent nickel, while the coordinated... 

The monomers dealt with can be polymerized by various mechanisms, not only by ROMP. For example, a rapid polymerization of norbornadiene occurs using a homogeneous catalytic system consisting of nickel acetylacetonate or a nickel-phosphine complex, such as nickel bis-(tri-n-butylphosphine) dichloride (NiCl2(TBP)2) or nickel bis-(tricyclohexylphosphine) dichloride (NiCl2(TBP)2). Nickel acetylacetonate as catalyst is known to initiate rather a classical vinyl polymerization (7). The classical vinyl polymerization... 

When some other reaction parameter, Z, such as the log of a rate constant, is plotted on to this steric and electronic map on an axis normal to the plane of the paper the comparative contributions of 6 and v should become apparent. A purely steric effect will slope north or south (the reader is encouraged to view Figures 26-28 of ref. 187 to appreciate this fully). Weimann and co-workers211 used Tolman s methodology to show the % steric effect in the oligomerization of butadiene catalyzed by nickel phosphine complexes. 

Terao and Kambe showed a dichotomy in the reactivity of nickel complexes (review [102]). While nickel diene complexes reacted primarily via two-electron pathways [34—37], nickel phosphine complexes promote radical addition reactions [103],... 

Process (SHOP). The oligomerization reaction is carried out on a nickel phosphine complex which is separated and recycled by means of a solvent. The reaction product consists of a-olefins and i-olefins of different carbon chain lengths. 

As already mentioned, the mechanism of oligomerization is the same as discussed for polymerization, and a catalytic cycle similar to the one shown in Fig. 6.3 operates. Many nickel-phosphine complexes have been successfully used as the precatalysts 7.17 is one such example. As shown by 7.5, reaction of a phosphorous ylide with a suitable nickel-containing precursor makes this... 

Compound (17-G-V) is used in analysis for the gravimetric determination of nickel. Phosphine complexes of the type tro/is-NiX and (L—L)NiX2 are used as precursors for numerous catalytic reactions some of these have also been discussed as potential anti-tumor agents.2 An unusual class of compounds are the metalladithi-olenes, for example, (17-G-VI) and (17-G-VII), which are readily oxidized to give, formally, Ni111 and Ni1 species. These compounds show metallic conductivity and may show low-temperature superconductivity.3... 

The arylation of activated alkenes with aryl halides in the presence of base was discovered by R. F. Heck in 1971 and is now one of the standard methods for C—C bond formation. The catalysts are mostly palladium or nickel phosphine complexes, which react via a succession of oxidative addition and insertion reactions, as shown in the following simplified cycle ... 

Grignard reagents remove tellurium from the tellurophene ring in refluxing benzene in the presence of nickel-phosphine complexes. ... 

Because of an increasing demand for these products in the pharmaceutical industry, a number of companies have paid special interest to the synthesis of profenes [32] such as ibuprofen, naproxen, ketoprofen and others from 1-arylethanol derivatives. Catalysts used for this transformation are palladium-phosphine complexes in concentrated hydrochloric acid, and to a lesser extent nickel-phosphine complexes in the presence of alkyl iodides or rhodium salts (cf. Section 2.9). 

Numerous complexes of nickel(II) and nickel(O) catalyze the addition of the Si-H bond to olefins. Among such catalysts are nickel-phosphine complexes, e.g., Ni(PR3)2X2 (where X=C1, I, NO3 R=alkyl and aryl), Ni(PPh3)4, and Ni-(CO)2(PPh3)2, as well as bidentate complexes of NiCl2-(chelate) and Ni(acac)2L (I phosphine), and Ni(cod)2(Pr3)2 [1-5]. A characteristic feature of nickel-phosphine-catalyzed olefin hydrosilylation is side reactions such as H/Cl, redistribution at silicon and the formation of substantial amounts of internal adducts in addition to terminal ones [69]. Phosphine complexes of nickel(O) and nickel(II) are used as catalysts in the hydrosilylation of olefins with functional groups, e.g., vinyl acetate, acrylonitrile [1-4], alkynes [70], and butadiynes [71]. 

A remarkable example of the cooperation of different active sites in a polyfunctional catalyst is the one-step synthesis of 2-ethylhexanol, including a combined hydroformylation, aldol condensation, and hydrogenation process [17]. The catalyst in this case is a carbonyl-phosphine-rhodium complex immobilized on to polystyrene carrying amino groups close to the metal center. Another multistep catalytic process is the cyclooligomerization of butadiene combined with a subsequent hydroformylation or hydrogenation step [24, 25] using a styrene polymer on to which a rhodium-phosphine and a nickel-phosphine complex are anchored (cf Section 3.1.5). 

Tamao, K., Sumitani, K., Kumada, M. Seiective carbon-carbon bond formation by cross-coupiing of Grignard reagents with organic halides. Catalysis by nickel-phosphine complexes. J. Am. Chem. Soc. 1972, 94, 4374 376. 

Tamao, K. Discovery of the cross-coupling reaction between Grignard reagents and C(sp2) halides catalyzed by nickel-phosphine complexes. J. Organomet. Chem. 2002, 653, 23-26. 

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