Palladium complexes triphenylphosphine

A novel catalyst system consisting of a palladium complex, triphenylphosphine, and indium(III) triflate is more active for the dimerization of vinylarenes compared with the generally used cationic palladium(II) catalysts (eq 22). ... 

It was found [99JCS(PI )3713] that, in all cases, the formation of the deiodinated products 38 and 39 was accompanied by formation of the diynes 40 which were isolated in 60-90% yield. The authors believed that the mechanism of deiodination may be represented as an interaction ofbis(triphenylphosphine)phenylethynyl-palladium(II) hydride with the 4-iodopyrazole, giving rise to the bisftriphenylphos-phine)phenylethynyl palladium(II) iodide complex which, due to the reductive elimination of 1 -iodoalkyne and subsequent addition of alk-1 -yne, converts into the initial palladium complex. Furthermore, the interaction of 1-iodoalkynes with the initial alkyne in the presence of Cul and EtsN (the Cadiot-Chodkiewicz reaction) results in the formation of the observed disubstituted butadiynes 40 (Scheme 51). 

In the direct coupling reaction (Scheme 30), it is presumed that a coordinatively unsaturated 14-electron palladium(o) complex such as bis(triphenylphosphine)palladium(o) serves as the catalytically active species. An oxidative addition of the organic electrophile, RX, to the palladium catalyst generates a 16-electron palladium(n) complex A, which then participates in a transmetalation with the organotin reagent (see A—>B). After facile trans- cis isomerization (see B— C), a reductive elimination releases the primary organic product D and regenerates the catalytically active palladium ) complex. 

Nucleophilic Substitution of xi-Allyl Palladium Complexes. TT-Allyl palladium species are subject to a number of useful reactions that result in allylation of nucleophiles.114 The reaction can be applied to carbon-carbon bond formation using relatively stable carbanions, such as those derived from malonate esters and (3-sulfonyl esters.115 The TT-allyl complexes are usually generated in situ by reaction of an allylic acetate with a catalytic amount of fefrafcz s-(triphenylphosphine)palladium... 

The analogous formation of aryl stannanes and aryl germanes from aryl halides occurs in the presence of catalytic amounts of palladium complexes of triphenylphosphine. Hexabutyl-... 

The distribution of the catalyst depends on the choice of the non-polar solvent and on the ligand used. With cyclohexane and the alcohols the palladium complexes of tricyclohexylphosphine and triphenylphosphine are located in the polar phase, with p-xylene the complex of triphenylphosphine is dispersed in both phases, and the complex of tricyclohexylphosphine can be predominantly found in the non-polar phase. Because of the low solubility of... 

To investigate the use of a non-polar catalyst phase and a polar product phase EC, PC and acetonitrile were chosen as polar solvents and cyclohexane and p-xylene as non-polar solvents. Tricyclohexylphosphine, triphenylphos-phine and bisadamantyl-n-butyl-phosphine were used as the ligand for Pd(acac)2. If cyclohexane is used as the non-polar solvent, the palladium complexes of tricyclohexylphosphine and triphenylphosphine are situated in the polar solvent and with p-xylene the complex of tricyclohexylphosphine is located in the non-polar phase, hi the solvent system EC/cyclohexane the palladium complex of bisadamantyl-n-butyl-phosphine can be found in the cyclohexane phase. 

Palladium(o) triphenylphosphine complexes catalyse the reduction of aryl bromides and iodides in a divided cell to give the diaryl [230]. The catalytic species... 

Tetrak1s(tr1phenylphosphine)palladium was prepared according to an Inorganic Syntheses procedure. The submitters used a freshly prepared, shiny yellow crystalline sample of the palladium complex. On standing for an extended period of time (> a few weeks), its color gradually darkens. The checkers used tetrakis(triphenylphosphine)palladium purchased from Aldrich Chemical Company, Inc. 

Although lithiation remains the most frequently used metalation reaction, there have been a number of new reports of direct palladation of aryloxazolines. For example, Smoliakova and co-workers prepared the dimeric palladium complex 457 by direct reaction of Pd(OAc)2 with 2-phenyloxazoline in the presence of NaOAc/ HOAc (Scheme 8.150). ° The dimeric complex 457 was converted to the monomeric triphenylphosphine complex 458 for which the X-ray crystal structure was determined. A similar reaction sequence was observed for naphthalenes. Muller... 

The carbonylation of Af-benzyl-y-(o-bromophenyl)propylamine to give AT-benzyl-tetrahydro-2-benzazepin-l-one is catalyzed by palladium acetate-triphenylphosphine complex (78JOC1684). On treatment with 2M sodium hydroxide the aminoketone (236) undergoes ring expansion to the 2-benzazepin-l-one (237) in a manner analogous to that outlined in Scheme 28 (80HCA924). 

The aqueous-organic two-phase system was successfully applied to perform hydrocarboxylation.300 Palladium complexes of trisulfonated triphenylphosphine ligands were shown to exhibit high activity.301-303 The application of cosolvents and modified cyclodextrins allow to eliminate solubility problems associated with the transformation of higher alkenes.304... 

Hydrocarboxylation of Polyunsaturated Fatty Acids and Esters with a Palladium Chloride— Triphenylphosphine Complex Catalyst... 

This result has been explained72 390 by the particular instability of the alkene complex resulting from exocyclic addition (14) relative to endocyclic addition (15) in the cyclohexyl system. This rationale is supported by the results obtained by the use of the considerably more sterically bulky tri-o-tolylphos-phine instead of triphenylphosphine. A 13 83 exocyclic endocyclic ratio is obtained with the bulky phosphine. This result is nicely explained by the ability of the bulky phosphine to magnify the instability of the endocyclic alkene-palladium complex (14) relative to the exocyclic alkene complex (15) and favor endocyclic addition. 

Further investigations including 109Ag NMR confirmed the in situ formation of alkynyl silver through jt complexation and proton abstraction.117 They also revealed that the best palladium catalyst, namely, palladium tetrakis(triphenylphosphine), played a key role, in that a phosphine liberated by decoordination ended up on the alkynyl silver, stabilizing it and rendering it more soluble.118 The resulting alkynyl silver then entered the palladium catalytic cycle at the transmetallation step (See section 10.6.2).105... 

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