Quaternary phosphonium nickel

Better results were obtained with catalysts of the type of quaternary phosphonium nickel halogenides or the corresponding ammonia compounds [408, 409]. Nickel bromide and nickel iodide are only soluble in butyl acrylate/butanol mixtures in amounts which are insufficient for the maintenance of the catalytic process. As mentioned in patents [408, 409], tertiary and quaternary complex compounds supply the required concentration of nickel and halogen ions for a continuous reaction. Many of the carbonylations, especially the stoichiometric reactions with Ni(CO)4 are carried out in the presence of water and acids. Jones [369] investigated the efficiency of the monobasic acids and showed hydrochloric acid and acetic acid to be of the same efficiency, whereas trichloro acetic acid is inefficient. He concludes that not the protons of the acids but the anions are of importance in the reaction mechanism. Apart from hydrochloric acid and acetic acid [345], sulfuric acid, aqueous phosphoric add, formic acid [367] and monochloroacetic acid are suited. A number of other organic acids [367] are ineffective. Acetic acid may be used in less than the equivalent amount because the unsaturated acid formed in the hydrocarbox-ylation [367] may replace acetic acid. 

Nickel (continued) polysulfide complex, 31 98 half chair conformation, 31 115 porphyrin complexes, 32 13 in proteins, 47 284-285 quadruply bridged dimers, 40 211-214 steric structures, 40 190-194 quaternary phosphonium salts of, 6 31-32 redox chemistry probes of structure, 32 243-245 steric and electronic requirements, 32 242-243... 

Other Compounds. Horner and co-workers [129-131] have described the production of optically active phosphines and arsines in the cathodic cleavage of quaternary phosphonium and arsonium salts. This reaction, like its reverse quaternization reaction, takes place with retention of configuration. Shapoval, Skobets, and Markova [132, 133] have described the production of a. stereoregular isocyanate polymer during reduction at a nickel cathode in dimethyl-formamide. The formation of a stereoregular product evidently demonstrates the orienting effect of the electrode on the molecules of the monomer in the polymerization process. 

Whatever metal is used, homogeneous processes suffer from high cost resulting from the consumption of the catalyst, whether recycled or not. This is why two-phase catalytic processes have been developed such as hydroformylation catalyzed by rhodium complexes, which are dissolved in water thanks to hydrophilic phosphines (cf. Section 3.1.1.1) [17]. Due to the sensitivity of most dimerization catalysts to proton-active or coordinating solvents, the use of non-aqueous ionic liquids (NAILs) as catalyst solvents has been proposed. These media are typically mixtures of quaternary ammonium or phosphonium salts, such as 1,3-dialkylimi-dazolium chloride, with aluminum trichloride (cf. Section 3.1.1.2.2). They prove to be superb solvents for cationic active species such as the cationic nickel complexes which are the active species of olefin dimerization [18, 19]. The dimers. 

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