Volume Profile Analysis of Oxidative Addition to Palladium(II) and Reductive Elimination from Palladium(IV)

Abstract

The oxidative addition of MeI to Pd(II) in the complex PdMe2(bpy) to produce PdIMe3(bpy) was studied as a function of [MeI] and pressure. The DV* of -11.9 +/- 0.6 cm3 mol-' for the addition process underlines the validity of the proposed SN2 mechanism in the literature. The reductive elimination from PdIMe3(bpy) to form PdIMe(bpy) and C2H6 was studied as a function of pressure and [NaI]. The complex was prepared in situ via oxidative addition of Me1 to the Pd(II) complex. DV* is +17 +/- 1 cm3/mol for the reductive elimination process. If NaI is added to the Pd(IV) compound, the rate slows down, but it did not affect the activation volume. The large positive value of DV* for the elimination reaction suggests bond cleavage and/or the partial reduction from Pd(IV) to Pd(II) in the transition state. A volume profile for the overall oxidative addition and reductive elimination reactions is presented.