New catalyst for the synthesis of dialkyl ketones from olefins, carbon monoxide, and hydrogen

Polyketones are obtained by the copolymerization of carbon monoxide and ethylene in the presence of a palladium catalyst formed in situ from Pd(OAc) 2 , dppp and formic acid in methanol which acted as a solvent. The productivity (g polymer/g Pd * h) is significantly influenced by the concentration of formic acid. Using the ratio Pd/dppp/HCOOH = 1/1/3000 at 90 • C and 45 atm, a productivity of 7500 h −1 is obtained. It is suggested that the efficiency of HCOOH as a promoter is due to its capability to act as a source of Pd-hydride species, which initiates the catalytic cycle.

Section: Effect Of Hcooh On the Productivitymentioning

confidence: 99%

Carbon monoxide–ethylene copolymerization catalyzed by a Pd(OAc)2/dppp/formic acid system [dppp=1,3-bis(diphenylphosphino)propane]

Vavasori¹,

Cavinato

Toniolo³

2003

“…of PPh 3 . The reduction occurs with concomitant formation of CO 2 , probably via a reaction closely related to the water gas shift reaction through the intermediacy of a Pd(II)-(COOH) species [64][65][66]:…”

Section: Reactivity With Water and With Water/tsohmentioning

confidence: 99%

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

Amadio¹,

Cavinato²,

Dolmella³

et al. 2009

a b s t r a c tThe cationic complexes trans- [Pd(COOR) (R = n-Pr, iso-Pr, n-Bu, iso-Bu, sec-Bu). They have been characterised by IR, 1 H NMR and 31 P NMR spectroscopies. The X-ray investigation of trans-[Pd(COOMe)(TsO)(PPh 3 ) 2 ] reveals that the palladium center is surrounded in a virtually square planar environment realized by two PPh 3 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 CHCl 3 . The Pd-O-S angle, 151.9 (3)• , is very wide, probably due to the interaction of one CHCl 3 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/H 2 O in MeOH at 50• C. All the carboalkoxy are precursors for the catalytic carboalkoxylation of ethene if used in combination of PPh 3 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.

“…200 h −1 , but increasing the water content up to 500-800 ppm, a maximum value of TOF is observed (850 h −1 ). Since it is known that water can act as a source of hydride species through a reaction strictly related to the water gas shift [18], it is reasonable to suppose that water favors the formation of Pd-hydride species [16].…”

Section: On the Catalystmentioning

confidence: 99%

Hydroesterification of cyclohexene using the complex Pd(PPh3)2(TsO)2 as catalyst precursor Effect of a hydrogen source (TsOH, H2O) on the TOF and a kinetic study (TsOH: p-toluenesulfonic acid)

Vavasori¹,

Toniolo²,

Cavinato

2003

The hydroesterification of cyclohexene is catalyzed by a preformed Pd(PPh 3 ) 2 (TsO) 2 complex I in methanol as solvent. The effect of PPh 3 , TsOH, and water on the TOF has been evaluated. The system I/PPh 3 /TsOH = 1/6/8, in the presence of 800 ppm of H 2 O, at 373 K and under 2.0 MPa of CO leads to a TOF as high as 850 h −1 . The increase of TOF observed adding a hydride source such as TsOH and H 2 O suggests that Pd-hydride species plays a key role in the first step of the catalytic cycle. The initial reaction rate increases linearly with the concentration of cyclohexene and of MeOH and passes through a maximum with increasing the pressure of CO. The rate equation r 0 = k 1 P CO (1 + k 2 P CO + k 3 P 2 CO ) −1 fits well the experimental data. The values of k 1 , k 2 , and k 3 have been evaluated at different temperatures. From the plot ln k versus 1/T, E 1 = 19.4 kcal/mol, E 2 = 20.6 kcal/mol and E 3 = 6.5 kcal/mol have been evaluated. On the basis of experimental evidences and of the kinetic study, a catalytic cycle mechanism has been proposed.