Effect of a Hydride Source (Water, Hydrogen, p-Toluenesulfonic Acid) on the Hydroesterification of Ethylene to Methyl Propionate Using a Pd(PPh3)2(TsO)2 (TsO = p-toluenesulfonate anion) Catalyst Precursor

Hydroesterification of ethylene to methyl propionate has been studied using the catalyst precursor Pd(PPh3)2(TsO)2, which is active in presence of PPh3 and TsOH (TOF = 5700 h-1 at 120°C, 40 atm (CO/C2H4 = 1/1), Pd/PPh3/TsOH = 1/8/10, [Pd] = 2 × 10-3 moll-1, solvent methanol, H2O = 800ppm). In this paper we study the promoting effect of a hydride source, molecular hydrogen, water and p-toluenesulfonic acid (TsOH) and the inhibiting effect of p-benzoquinone. On the basis of experimental evidences, of the two possible initial steps of the catalytic cycle, the insertion of the olefin into a Pd-H species or into a Pd-OCH3 species, it is suggested that the first plays a more important role. © 2001 Elsevier Science B.V. All rights reserved.