High-pressure (2 GPa) batch reactors now commercially available may offer substantial accelerations of organometallic syntheses, without resort to heating, when the activation process is multicentered or involves the generation and solvation of ions. As an example of the latter class of reactions, the kinetics of the oxidative additions of methyl and ethyl iodides (RI) to dimethyl(2,2′-bipyridine)platinum(II) in acetone have been studied over the pressure range 0–200 MPa. The volumes of activation ΔV1≠, if assumed to be constant over this range, are −11.7 ± 0.3 and −9.7 ± 0.7 cm3 mol−1, respectively, implying an acceleration of ca. 3000-fold for a batch synthesis of this sort at 2 GPa. However, a possible slight pressure dependence of ΔV1≠ may reduce this acceleration to ca. 1 000-fold. The ΔV1≠ data and the 500-fold retardation on going from R = Me to R = Et are consistent with an SN2 attack of Pt11 on the α-carbon in the alkyl iodides, forming I− and [RMe2Pt(bpy)]+. Key words: volumes of activation, high pressure, oxidative addition, platinum(II), organometallic syntheses.