263755-12-0Relevant articles and documents
Mechanistic studies on the selective oxidative carbonylation of MeOH to dimethyl oxalate catalyzed by [Pd(COOMe)n(TsO)2-n(PPh 3)2] (n = 0, 1, 2) using p-benzoquinone as a stoichiometric oxidant
Amadio, Emanuele,Toniolo, Luigi
, p. 74 - 79 (2014)
The reactivity of the complexes cis-[Pd(OTs)2(PPh 3)2] (I), trans-[Pd(COOMe)(OTs)(PPh3) 2] (II) and trans-[(COOMe)2(PPh3)2] (III), regarding the catalytic oxidative carbonylation of MeOH to dimethyl oxalate (DMO) using benzoquinone (BQ) as a stoichiometric oxidant, has been studied in CD2Cl2/MeOH (10/1, v/v) by 1H and 31P{1H} NMR spectroscopy. I reacts with CO and MeOH at 193 K giving II, which is transformed into III upon addition of a base. The same occurs in the presence of BQ. Instead, if the base is added before admission of CO, [Pd(BQ)(PPh3)2] is formed. Starting also from II, complex III is formed only after addition of a base. The base neutralizes TsOH which is formed in the transformation of I to II and III. III is unstable in the presence of 1 equivalent of TsOH and it is transformed into II. At 333 K, under 0.4 MPa of CO, III decomposes with formation of DMO and dimethyl carbonate (DMC) (15%) each), whereas, in the presence of BQ, III is unstable already at 298 K, with formation of only DMO (10%). Catalysis to DMO is observed at 333 K. Thus BQ enhances the reactivity of III and directs the catalysis selectively to DMO. I, II and III have also been used in catalytic experiments in pure MeOH at 298 K, under 0.3 MPa of CO. II and III are active even in the absence of a base (TOF ca. 30 h-1). I is active only after addition of a base. A catalytic cycle is proposed.
New carboalkoxybis(triphenylphosphine)palladium(II) cationic complexes: Synthesis, characterization, reactivity and role in the catalytic hydrocarboalkoxylation of ethene. X-ray structure of trans-[Pd(COOMe)(TsO)(PPh3)2]·2CHCl3
Amadio,Cavinato,Dolmella,Ronchin,Toniolo,Vavasori
, p. 103 - 110 (2009/04/12)
The cationic complexes trans-[Pd(COOR)(H2O)(PPh3)2](TsO) have been synthesised by reacting cis-[Pd(H2O)2(PPh3)2](TsO)2·2H2O with CO in ROH (R = Me and Et), practically under room conditions, or by methathetical exchange of trans-[Pd(COOMe)Cl(PPh3)2] with Ag(TsO) (R = n-Pr, iso-Pr, n-Bu, iso-Bu, sec-Bu). They have been characterised by IR, 1H NMR and 31P NMR spectroscopies. The X-ray investigation of trans-[Pd(COOMe)(TsO)(PPh3)2] reveals that the palladium center is surrounded in a virtually square planar environment realized by two PPh3 trans to each other, the carbon atom of the carbomethoxy ligand and an oxygen atom of the p-toluensulfonate anion, with two crystallization molecules of CHCl3. The Pd-O-S angle, 151.9 (3)°, is very wide, probably due to the interaction of one CHCl3 molecule with the complex inner core. The carbomethoxy derivatives react with R′OH yielding the corresponding R′ carboalkoxy derivative (R′ = Et, n-Pr and iso-Pr); ethene does not insert into the Pd-COOMe bond; decarbomethoxylation occurs when treated with TsOH/H2O in MeOH at 50 °C. All the carboalkoxy are precursors for the catalytic carboalkoxylation of ethene if used in combination of PPh3 and TsOH, better in the presence of some water. Experimental evidences are more in favor of the so-called "hydride" mechanism rather than the "carbomethoxy" mechanism.
Synthesis, characterization and catalytic activity in the carbonylation of ethene of compounds Ia and IIa (see abstract). X-ray structure of Ia and IIa·2CH2Cl2
Cavinato, Gianni,Vavasori, Andrea,Toniolo, Luigi,Dolmella, Alessandro
, p. 2737 - 2747 (2008/10/09)
The complexes cis-[Pd(H2O)2(PPh3) 2]X2·nH2O (Ia: X=p-CH3C 6H4SO3, n=2; IIa: X=CH3SO 3, n=0) have been synthesized by reacting Pd(OAc)2, PPh3 and HX in acetone in the presence of H2O. They have been characterized by IR, 1H and 31P NMR spectroscopy and TA analysis. By re-crystallization of these complexes, crystals of Ia and IIa·2CH2Cl2 suitable for the X-ray analysis have been obtained. The solid-state investigation of Ia reveals that the two p-toluenesulfonato units act as counter anions of a dicationic complex, in which the metal atom is surrounded in a square planar environment realized by two water molecules and two PPh3 moieties that are cis to each other. The X-ray investigation of IIa·2CH2Cl2 shows that also in this case the two PPh3 are cis to each other and that in the acentric triclinic cell there are two independent [Pd(H2O) 2(PPh3)2]2+ units, together with two methanesulfonato counter anions and two crystallization molecules of CH 2Cl2. The cationic complexes Ia and IIa are easily inter-converted with the neutral species trans-[Pd(p-CH3C 6H4SO3)2(PPh3) 2] (Ib) and trans-[Pd(CH3SO3) 2(PPh3)2] (IIb), respectively, depending on temperature and solvent. In chloroform at r.t., complex Ia catalyzes the carbonylation of ethene to a polyketone; at higher temperature in methanol it catalyzes the hydroesterification of ethene. In both cases catalysis is accompanied by CO2 evolution. These results suggest that catalysis occurs via initial formation of a Pd(II)-H species by interaction of H 2O with CO on the metal center though a reaction closely related to that of the water gas-shift.
Characterization and catalytic activity of trans-[Pd(COCH2CH3)(TsO)(PPh3)2 ], isolated from the hydro-methoxycarbonylation of ethene catalyzed by [Pd(TsO)2(PPh3)2]
Cavinato, Gianni,Toniolo, Luigi,Vavasori, Andrea
, p. 233 - 240 (2008/10/09)
trans-[Pd(COCH2CH3)(TsO)(PPh 3)2] (I) was isolated after running the hydro-methoxycarbonylation (HMC) of ethylene. Complex (I) catalyzed the HMC of ethylene to methylpropanoate. Catalysis occurred via an initial
