VOLUME PROFILE ANALYSIS OF OXIDATIVE ADDITION TO PALLADIUM(II) AND REDUCTIVE ELIMINATION FROM PALLADIUM(IV)

The oxidative addition of Mel to Pd(II) in the complex PdMe2(bpy) to p roduce PdlMe3(bpy) was studied as a function of [Mell and pressure. Th e DELTAV(double dagger) of -11.9 +/- 0.6 cm3 mol-1 for the addition pr ocess underlines the validity of the proposed S(N)2 mechanism in the l iterature. The reductive elimination from PdIMe3(bpy) to form PdIMe(bp y) and C2H6 was studied as a function of pressure and [NaI]. The compl ex was prepared in situ via oxidative addition of MeI to the Pd(II) co mplex. DELTAV(double dagger) is + 17 +/- 1 cm3/mol for the reductive e limination process. If NaI is added to the Pd(IV) compound, the rate s lows down, but it did not affect the activation volume. The large posi tive value of DELTAV(double dagger) for the elimination reaction sugge sts bond cleavage and/or the partial reduction from Pd(IV) to Pd(II) i n the transition state. A volume profile for the overall oxidative add ition and reductive elimination reactions is presented.