Palladium sulfoxides

The reaction of alcohols with CO was catalyzed by Pd compounds, iodides and/or bromides, and amides (or thioamides). Thus, MeOH was carbonylated in the presence of Pd acetate, NiCl2, tV-methylpyrrolidone, Mel, and Lil to give HOAc. AcOH is prepared by the reaction of MeOH with CO in the presence of a catalyst system comprising a Pd compound, an ionic Br or I compound other than HBr or HI, a sulfone or sulfoxide, and, in some cases, a Ni compound and a phosphine oxide or a phosphinic acid.60 Palladium(II) salts catalyze the carbonylation of methyl iodide in methanol to methyl acetate in the presence of an excess of iodide, even without amine or phosphine co-ligands platinum(II) salts are less effective.61 A novel Pd11 complex (13) is a highly efficient catalyst for the carbonylation of organic alcohols and alkenes to carboxylic acids/esters.62... 

Also, the trimerization reaction was observed by using jr-allyl complexes of palladium stabilized by chelating ligands, such as 28 and 29 (38). The reaction was carried out at 70°C in dimethylformamide (DMF) or dimethyl sulfoxide (DMSO), and 1,3,6,10-dodecatetraene (27) was obtained in 60% yield at 30% conversion. 

Structural Identification of a Palladium Complex with a Chiral Sulfoxide Ligand... 

The technique, although attractive, is experimentally rather complex charging problems can frequently occur, leading to the observation of elevated apparent binding energies, and interpretational difficulties exist. Thus, the X-PES of palladium(II) sulfoxide complexes are difficult to interpret unambiguously as the oxygen Is peak is nearly... 

The use of palladium(II) sulfoxide complexes as catalyst precursors for polymerization has met with mixed results thus a report of a palla-dium(II) chloride-dimethyl sulfoxide system as a catalyst precursor for phenylacetylene polymerization suggests similar results to those obtained using tin chloride as catalyst precursor (421). However, addition of dimethyl sulfoxide to solutions of [NH fPdCh] decreases the activity as a catalyst precursor for the polymerization of butadiene (100). Dimethyl sulfoxide complexes of iron have also been mentioned as catalyst precursors for styrene polymerization (141). 

Much of the chemistry of palladium and platinum sulfoxide complexes has been discussed in previous sections and so only additional salient points will be mentioned here. A complete listing of all palladium and platinum sulfoxide complexes prepared would require a review article in itself. 

Neutralization of the strip solution with hydrochloric acid gives Pd(NH3)2-CI2 as product. One of the problems that has emerged is the formation of di- -hexylsulfoxide [34] by oxidation of the sulfide. This may cause several problems including extraction of iron(III) that is strongly dependent on the HCl concentration. The iron can easily be stripped by water. There have also been indications of a buildup of rhodium in the extract phase that again can be explained by the extraction of anionic rhodium species by the sulfoxide. One benefit from the presence of the sulfoxide is that the rate of palladium extraction is increased by the presence of the protonated sulfoxide at high acidities however, this kinetic enhancement is less that found with TOA HCl, which remains protonated even at low acidities. 

Dialkyl and diaryl sulfoxides were reduced (deoxygenated) to sulfides by several methods. As a little surprise sulfides were obtained from sulfoxides by catalytic hydrogenation over 5% palladium on charcoal in ethanol at 80-90° and 65-90 atm in yields of 59-99% [684. In the case of p-tolyl -styryl sulfoxide deoxygenation was achieved even without reduction of the double bond giving 66% of p-tolyl -styryl sulfide and only 16% of p-tolyl -phenyl-ethyl sulfide [684],... 

In high polarity solvents, such as acetonitrile, dimethyl sulfoxide, methyl acetate, and methanol, the branched dimer, 4-methyl azelate precursor, is formed in high yield. In methanol, a methoxy dimer (CH302CCgH] 4(0013)0020113) is also formed in moderate yield. Heavies contain both an acyclic methyl, 4-pentadienoate trimeric product and high molecular weight methyl, 4-pentadienoate homopolymer. Polymerization in the absence of air(48) appears to be catalyzed by traces of the tertiary phosphine which is used to prepare the palladium dimerization catalyst. 

Dibromonaphthalene 274 undergoes a Pd(0)-BINAP [3+3] coupling reaction, believed to involve an initial N-arylation reaction and subsequent C-C bond formation of product 275 (Equation 37) <2004OL3293>. Bis(sulfonamide) 276 (formed in 56% yield in the presence of Cul and CsOAc in dimethyl sulfoxide (DMSO)) is not observed under the palladium-catalyzed conditions. 

Fluoro-6-iodopyridazine (6) required for palladium-catalyzed Heck coupling with hydroxy-protected prop-2-yn-l-ol has been prepared by simply heating the 3,6-diiodopyridazine (5) with potassium fluoride in dimethyl sulfoxide at 140°C for 18 hours.121... 

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