Zero-valent triphenylphosphine

Another route to p.-Carbido complexes which we have found is oxidative addition of Lalor s halocarbyne complexes [21] to zero valent triphenylphosphine compounds of nickel, palladium and platinum. In these reactions the heterodimetalla cyclopropenes could be isolated which isomerize at higher temperatures to the dimetalla allene complexes. The first adducts of arylcarbyne complexes to zerovalent platinum complexes (arylcarbyne as analogue of ace-... 

Hydrides of Pt(II) are the most numerous of any transition metal hydride group. In addition to the presence of the hydride ligand, the complexes invariably have a coordinated phosphine, and synthetic routes to these compounds using both hydridic and protonic reagents have been reported (I). The pure complexes are usually both air stable and kinetically inert. The purpose of this chapter is to show the diversity of hydrides that can be obtained from protonation reactions on zero-valent and di-valent triphenylphosphine platinum compounds, and to rationalize the type and nature of the product formed from the character of the acid HX. 

An elegant synthesis method which is specific to sulfone polymers containing phenyl—phenyl linkages (such as PPSF) is the nickel-catalyzed coupling of aryl dihalides. The scheme for this synthesis involves a two-step process. First, an aromatic dihalide intermediate is formed which carries the backbone features of the desired polymer. This aromatic dihalide intermediate is then self-coupled in the presence of zero-valent nickel, triphenylphosphine, and excess zinc to form the biphenyl- or terphenyl-containing polymer. Application of this two-step scheme to PPSF can be depicted as follows ... 

Methods (i) and (ii) require palladium(II) salts as reactants. Either palladium acetate, palladium chloride or lithium tetrachloropalladate(II) usually are used. These salts may also be used as catalysts in method (iii) but need to be reduced in situ to become active. The reduction usually occurs spontaneously in reactions carried out at 100 °C but may be slow or inefficient at lower temperatures. In these cases, zero valent complexes such as bis(dibenzylideneacetone)palladium(0) or tetrakis(triphenylphos-phine)palladium(O) may be used, or a reducing agent such as sodium borohydride, formic acid or hydrazine may be added to reaction mixtures containing palladium(II) salts to initiate the reactions. Triarylphosphines are usually added to the palladium catalysts in method (iii), but not in methods (i) or (ii). Normally, 2 equiv. of triphenylphosphine, or better, tri-o-tolylphosphine, are added per mol of the palladium compound. Larger amounts may be necessary in reactions where palladium metal tends to precipitate prematurely from the reaction mixtures. Large concentrations of phosphines are to be avoided, however, since they usually inhibit the reactions. 

Electroreduction of triphenylphosphino- or 1,2-bisdiphenylphosphinoethanenickel(II) complexes in ethanol via zero valent complexes with halobenzenes has been described87. Arylation of olefins (equation 55) can be achieved by electro generated Ni(0) complex 106, associated with triphenylphosphine and an alkene (107). The optimum conditions for the reaction include the use of one to three equivalents of triphenylphosphine and a base such as triethylamine30. 

Tetrachloropalladate(II) ion catalyzes the interconversion of 1- and 2-butenes in aqueous solutions containing chloride and hydronium ions. Sodium tetrachloropalladate(II) catalyzes the conversion of allylbenzene to propenyl-benzene in acetic acid solutions. Tetrakis(ethylene))Lt,/x -dichlororhodium(l) catalyzes butene isomerization in methanolic hydrogen chloride solutions . Cyclooctadienes isomerize in benzene-methanol solutions of dichlorobis-(triphenylphosphine)platinum(11) and stannous chloride. Chloroplatinic acid-stannous chloride catalyzes the isomerization of pentenes. Coordination complexes of zero-valent nickel with tris(2-biphenylyl)phosphite or triphenyl-phosphine catalyze the isomerization of cis-1,2-divinylcyclobutane to a mixture of c/5,m-l, 5-cyclooctadiene and 4-vinylcyclohexene . Detailed discussions of reaction kinetics and mechanisms appear in the papers cited. 

Tris- and tetrakis(triphenylphosphine) derivatives of zero-valent platinum can be obtained by reduction of platinum(II) triphenylphosphine compounds by alcoholic potassium hydroxide or hydrazine. The tris(triphenyl-phosphine) derivative is easily obtained from the tetrakis derivative by treatment with hot ethanol. ... 

As indicated in a previous paper near quantitative yields of biphenyl derivatives can be obtained from select chloroaromatic compounds using zero valent nickel-triphenylphosphine complex in the presence of zinc metal. The conditions employ a catalytic amount of nickel-triphenylphosphine complex in the presence of zinc metal in dry, dipolar aprotic solvents at 60 to 80°C. The reaction is complete in a few minutes. 

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