Nickel phosphine carbonyl complex

In the case of phosphine, especially tri-n-butyl and triphenyl phosphines, an active phosphine complex is formed in the reaction medium via reaction with nickel carbonyl. This complex is a very active species provided that the optimum concentration of phosphine is used. Low phosphine concentration results in a loss of the effective nickel concentration through the formation of nickel tetra-carbonyl, nickel metal or nickel iodide. The absolute concentration of phosphine is less important than the P/Ni ratio. In addition to form the stable Ni-P catalyst, the phosphine has to compete with other ligands in the reaction mixture for nickel. With high carbon monoxide partial pressure, there is more CO in solution to compete with phosphine favoring the formation of the carbonyl, which is inactive under the reaction conditions. Hence with high carbon mon-... 

The effect of tin compounds, especially tetra-alkyl and tetra-aryl tin compounds, is similar to that of phosphine, though lower temperature and pressure are required for the catalyst s optimum activity. Tin can promote the activity of the nickel catalyst to a level that matches that of rhodium under mild conditions of system pressure and temperature e.g. 400 psig at 160 C. The tin-nickel complex is less stable than the phosphine containing catalyst. In the absence of carbon monoxide and at high temperature, as in carbonyl-ation effluent processing, the tin catalyst did not demonstrate the high stability of the phosphine complex. As in the case of phosphine, addition of tin in amounts larger than required to maintain catalyst stability has no effect on reaction activity. 

The ability of nickel complexes, e.g., nickel carbonyl and its phosphine derivatives, to catalyze polymerization and other reactions of olefins and acetylenes has been studied extensively (46, 53), particularly by Reppe. 

Tetrakis(alkyl isocyanide) complexes of nickel(O), Ni(CNR)4, and the mixed isocyanide complexes with phosphines and unsaturated molecules are strictly analogous to the corresponding carbonyl complexes.23,24 They are generally more stable than [Ni(CN)4]4-. Mixed isocyanide complexes have been prepared by the reaction of Ni(cod)2 and CNBu followed by reaction with the appropriate phosphine or unsaturated molecules (alkenes, arylnitroso compounds, azo compounds, etc.) as outlined in equations (7) and (S).25... 

Thiocarbonyl derivatives of 1,3-dioxolanes and 1,3-oxathiolanes are readily isomerized to the 2-carbonyl compounds as shown in Scheme 20. Alkylation of the sulfur atom with alkyl halides usually leads to ring-opened products (Scheme 21) (69JOC3011). Most of the other chemistry of the sulfur derivatives has focused on desulfurization and subsequent generation of alkenes. The reaction is shown in equation (20) and proceeds with cis elimination via carbene intermediate (see Section 4.30.2.2.5) and is usually carried out with a phosphine (73JA7161) or a zero-valent nickel complex (73TL2667). 

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). 

The catalytic hydrocarbonylation and hydrocarboxylation of olefins, alkynes, and other TT-bonded compounds are reactions of important industrial potential.Various transition metal complexes, such as palladium, rhodium, ruthenium, or nickel complexes, have widely been used in combination with phosphines and other types of ligands as catalysts in most carbonylation reactions. The reactions of alkenes, alkynes, and other related substrates with carbon monoxide in the presence of group VIII metals and a source of proton affords various carboxylic acids or carboxylic acid derivatives.f f f f f While many metals have successfully been employed as catalysts in these reactions, they often lead to mixtures of products under drastic experimental conditions.f i f f f In the last twenty years, palladium complexes are the most frequently and successfully used catalysts for regio-, stereo-, and enantioselective hydrocarbonylation and hydrocarboxylation reactions.f ... 

Silylene 59 also behaves somewhat like a phosphine in its interactions with metal carbonyls Typical reactions involve substitution of silylene for CO, to give a silylene-metal complex. Three examples are shown in Scheme 20, and the structure of the nickel complex 75 is displayed in Figure This complex is both the first silylene-nickel complex, and the first example of a bis-silylene-metal complex free of stabilization by Lewis base donors. 

Since Reppe s discovery of the cyclotrimerization of acetylene to benzene in the presence of nickel carbonyl-phosphine complexes, the use of nickel catalysts in many organic transformations has become popular. Transition metal complex catalysis provides many elegant entries to carbon-carbon bond-forming reactions in organic synthesis. One notable example is carbocyclic ring expansion mediated by nickel(O) complexes. ... 

Phosphorus also functions as a chelating group. The carbonyl group of a phosphine-tethered benzophenone/nickel complex was extruded upon heating to give a biaryl (Scheme 1.18) [28]. The extrusion/insertion of CO was reversible, indicating that the aryl-aryl bond also adds to nickel(O) facilely. The related oxidative addition reaction to iridiumfl) and rhodiumfl) was also reported [29]. 

Many of these nickel carbonyl-base compounds have been prepared primarily for use in infrared studies, some of the conclusions of which are summarized briefly in Section II, C 30,41,46,47,48,50,51,127,349). The phosphine-nickel complexes have catalytic activity in the polymerization of acetylenes, and the mechanisms of these polymerizations have been studied 350, 351). Interest in these catalysts has led to an investigation of their phosphorus-31 NMR spectra, which may be qualitatively correlated with the accepted ideas on metal-ligand bonding (72). 

The complex (CH2=CHCN)3Mo(CO)3 is known and in this case the acrylonitrile is bonding as a 2-electron C=C system [88]. With nickel tetra-carbonyl, acrylonitrile forms the pyrophoric deep red (CH2=CHCN)2Ni [91], whose structure is unknown [85]. Treatment of this with triphenyl-phosphine gives the complex (PPh3)2Ni(CH2=CHCN)2 two possible structures for which are (A) and (B). 

Recently, the heterogenization technique has allowed more-selective reactions to be observed. For example, butadiene gives 95% of 1,3,6-octatriene (example 28 in Table 1) on a catalyst obtained by reduction of NiBr2(supported phenylphosphines)2 with NaBH4 (44). Nickel-carbonyl complexes have also been supported on phosphinated silica (55). 

I, Table X) requires tertiary phosphine-nickel halide or tertiary phosphine-nickel carbonyl complexes at 140-170°C. This implies oxidative addition of aromatic halides to nickel, replacement of the halide with amines, and reductive elimination. 

Both form nickel carbonyl complexes (36). The lithium salt of triphenylstannide, which can readily be formed from tetraphenyltin and lithium salts, reacts violently with nickel carbonyl to give the presumably efficient catalyst Li(Ni(C0)3Sn(Ph)3). This complex possibly catalyzes the carbonylation of methyl iodide in a manner similar to that of the phosphine complex. 

Only a limited number of cyano and isocyano complexes and mixed carbonyl, nitrosyl and phosphine cyano complexes of nickel(O) have been described so far.16... 

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