RATE AND MECHANISM OF OXIDATIVE ADDITION OF ARYL TRIFLATES TO ZEROVALENT PALLADIUM COMPLEXES - EVIDENCE FOR THE FORMATION OF CATIONIC (SIGMA-ARYL)PALLADIUM COMPLEXES
A. Jutand et A. Mosleh, RATE AND MECHANISM OF OXIDATIVE ADDITION OF ARYL TRIFLATES TO ZEROVALENT PALLADIUM COMPLEXES - EVIDENCE FOR THE FORMATION OF CATIONIC (SIGMA-ARYL)PALLADIUM COMPLEXES, Organometallics, 14(4), 1995, pp. 1810-1817
The rate of oxidative addition of Pd-0(PPh(3))(4) to aryl triflates is
monitored by amperometry and conductivity measurements in DMF. The ki
netics follow a Hammett correlation, the oxidative addition being fast
er when the aryl group is substituted with an electron-withdrawing gro
up. This reaction proceeds in the absence of deliberately added halide
s, to afford a unique, well-defined, stable arylpalladium complex that
has been characterized for the first time, by conductivity measuremen
ts and mass and IR spectroscopies, as a cationic complex Ar-Pd(PPh(3))
(2)(+) with CF3SO3- as the counteranion. The oxidative addition is fas
ter in the presence of added chloride and affords neutral complexes tr
ans-Ar-PdX(PPh(3))(2). The aryl triflates are found to be less reactiv
e with Pd-0(PPh(3))(4) than aryl iodides but slightly more reactive th
an aryl bromides.