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)

✍ Scribed by Andrea Vavasori; Luigi Toniolo; Gianni Cavinato

• Publisher: Elsevier Science
• Year: 2003
• Tongue: English
• Weight: 194 KB
• Volume: 191
• Category: Article
• ISSN: 1381-1169
• DOI: 10.1016/s1381-1169(02)00358-8

✦ Synopsis

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.