High-pressure methods as a tool in organometallic syntheses: Facilitation of oxidative addition to platinum(II)

Article abstract of DOI:10.1139/v96-227

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 son 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 S_N2 attack of Pt^II on the α-carbon in the alkyl iodides, forming I^- and [RMe₂Pt(bpy)]⁺.