Oxidative Addition of Ligand-Chelated Palladium(0) to Aryl Halides: Comparison between 1,2-Bisthioethers and 1,2-Bisphosphines

The kinetics of the oxidative addition of bidentate ligand-chelated Pd0 complexes to phenyl iodide and bromide has been studied via cyclic voltammetry. The dibenzylideneacetone (dba) delivered by the palladium precursor Pd(dba)2 was found to affect the concentration of the more reactive dba-free Pd0 complex and consequently the kinetics of the overall oxidative addition. The complexes generated from Pd(dba)2 and PhSCH2CH2SPh (pte) were found to be considerably more reactive than those generated from Pd(dba)2 and Ph2PCH2CH2PPh2 (dppe). The former complexes can react with PhBr at low temperatures.