Rate and Mechanism of the Oxidative Addition of Benzoic Anhydride to Palladium(0) Complexes in DMF

The rate constant of the oxidative addition of the benzoic anhydride (PhCO)2O to [Pd0(PPh3)4] has been determined in DMF and compared to that of phenyl halides and phenyl triflate. The following reactivity order has been established: PhI >> (PhCO)2O > PhOTf > PhBr. The oxidative addition of (PhCO)2O proceeds by activation of one C−O bond. Two acyl-PdII complexes are formed: a neutral complex trans-[(PhCO)Pd(OCOPh)(PPh3)2] and a cationic complex trans-[(PhCO)PdS(PPh3)2]+ (S = DMF) showing that the decarbonylation process is highly endergonic. The exchange of PPh3 by the bidentate ligand dppp does not favor the decarbonylation process.