Palladium complexes sulfoxides

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). 

A number of metal / -diketonates have been used to catalyze the oxidation of sulfides to sulfoxides, important synthetic intermediates for the construction of various biologically active molecules . For example, an elegant study by Ishii and coworkers demonstrated that VO(acac)2 (35) selectively catalyzed the sulfoxidation of adamantane (41) by SO2/O2 to give 1-adamantane sulfonic acid (42) (equation 10) . Although a number of metal acac complexes were examined as catalysts for this reaction, all but the vanadium compound failed to promote the sulfoxidation. The catalytic oxidation of triarylphosphines using the palladium complex Pd(acac)2 (29) has also been investigated . 

A useful synthesis of functionalized dienes from alkenes used the initial formation of a stable rr-allyl palladium complex, followed by reaction with a-sulfinyl ester enolate and pyrolytic sulfoxide elimination (Scheme 55). ... 

Chiral /3-amino sulfoxides served as chiral ligands in Pd-catalyzed allylations. Chiral j8-aminoethyl sulfoxides 31a-f-palladium complexes catalyzed asymmetric ally-lations of 33 to give (5)-34 with 29% ee. o-Aminophenyl sulfoxides 32a,b provided much higher enantioselectivity (50%), presumably due to the sterically fixed structure of the intermediary palladium complex 35 (Scheme 17). 

Battace, A., Zair, T., Doucet, H. and Santelli, M. (2006) Heck vinylations using vinyl sulfide, vinyl sulfoxide, vinyl sulfone, or vinyl sulfonate derivatives and aryl bromides catal3raed by a palladium complex derived from a tetraphosphine. Synthesis, 3495 505. 

DMSO complexes have also been prepared and studied in contexts related to organome-tallic chemistiy. DMSO binds to low-valent late metals through the electron pair on sulfur, to harder high-valent metals through the electron pairs on oxygen, and to some complexes with a mixture of 0- and S-bound forms. " Palladium complexes of DMSO and of biden-tate sulfoxide ligands have been used as catalysts for the oxidative cyclization of enols and... 

A chiral sulfoxide-palladium complex was determined as a chelate coordinated by the sulfinyl oxygen atom by X-ray crystallographic analysis. ° The amino-phosphine palladium chloride 43 was transformed into 44 by chloride abstraction with AgPFg. The six-membered P—O chelate strucmre was confirmed by crystallographic analysis (Scheme 21). 

Analogously, a decrease in the S-O stretching frequency, indicative of oxygen coordination, is observed when dimethyl sulfoxide or tetramethylene sulfoxide is complexed to many metal ions, iodine and phenol, whereas the S-O stretching frequency increases in the palladium complex of dimethyl sulfoxide, compared to free sulfoxide, which suggests sulfur coordination. 

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. 

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