Palladium Compounds Dichlorobis

A degassed suspension of lhe halo compound 14 and an alkyne (1.2 equiv) in Et3N (0.1-0.2 mol) was stirred in the presence of dichlorobis(triphenylphosphane)palladium(II) (0.02 equiv) and coppcr(I) iodide (0.04 equiv) at 20 C for 20 h. EtOAc was added and the mixture was washed with H20 and brine the organic phase was dried (MgSOi) and evaporated to yield the product. 

Recently compounds containing cyclic polyolefins coordinated to platinum or palladium have received considerable attention as a result of the unique bonding found in these compounds and their possible use as intermediates in a variety of reactions. Several methods have been reported for the synthesis of these compounds, and among these procedures the displacement of ethylene1 from di-Ju-chloro-dichlorobis(ethylene)diplatinum(II) and benzonitrile2 from dichlorobis(benzonitrile)palladium(II) are the most generally applied procedures. Both of these methods involve the preparation of intermediates before the isolation of the product, and in addition these intermediates tend to decompose upon storage. 

Compound 4.8 is (7.v-dichlorobis(triethylphosphine)plat-inum(II) compound 4.9 is //Y///.y-tetramminebis(dimethylamido)-cobalt(IIl) ethoxide compound 4.10 is bis[c/ y-dibromo( i -dimethyl SLilfide)platinum(lI)] compound 4.11 is benzenethiolatochloro(ri--propene)palladium(Il). 

Under remarkably mild conditions aromatic cyanides can be prepared from halogen compounds with alkali metal cyanides in the presence of transition metal complexes. Complexes of palladium and nickel are particularly useful, for instance tetrakis(triphenylphosphine)palladium(0) (6), tris(triphe-nylphosphine)nickel(O) (7) or trun -dichlorobis(triphenylphosphine)nickel(II) (8 Scheme 7). 

The compounds PdCl2(MeCN)2 and PdCl2(PhCN)2 are convenient starting materials for the synthesis of dichlorobis(tertiary phosphine)palladium(ll) complexes. In a typical procedure, PdCl2(MeCN)2 is suspended in benzene (for arylphosphines) or ether (for alkylphosphines) under nitrogen. Two equivalents of tertiary phosphine is added and the mixture is stirred at room temperature for several hours. A yellow or orange precipitate of the desired compound is formed. If necessary, hexane or ether is added to complete the precipitation. The product is collected by filtration, washed with ether, and dried under vacuum. PdCl2(PR3)2 type complexes are also prepared by treatment of [PdClJ with phosphine [150]. 

Dichloro(l,S-cyclooctadiene)palladium(II) is an air-stable yellow solid. The compound is slightly soluble in solvents such as chloroform, sulfolane (tetrahydrothiophene 1,1-dioxide), and nitrobenzene and reacts with dimethyl sulfoxide to yield dichlorobis(dimethyl sulfoxide)palladium(II). The PMR spectrum of the compound in chloroform shows resonances at t3.68 for the olefinic protons and at t7.31 for the methylene protons. The infrared... 

Dichlorobis(benzonitrile)palladium(II) is known to react with butadiene to give a yellow complex, formulated by previous workers as a diolefin complex [Pdcyc Hg)] or shown this compound... 

Solvent effects on, and products from, reaction of styrene with ethylene in the presence of di-)ti-chloro-dichlorobis(styrene)dipalladium(n), [Pd-(Ph CH—CH2)Cl2]2, indicate a mechanism similar to (i)->(iv) above, with the addition of a preliminary equilibrium between the dimer and solvated monomers. The mechanism of reaction of styrene with vinyl compounds, catalysed by the same chloride-bridged dipalladium complex, has been studied using isotopic tracer (H, D) experiments. Palladium-acetate-catalysed reaction of styrene with benzene, also investigated using deuterium tracer experiments, involves no hydride shift, in contrast to the rather closely related Wacker process. The importance of intermediates with palladium-carbon n-bonds in palladium(ii)-catalysed alkylation and arylation of alkenes has been demonstrated. 

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