HIGH-PRESSURE METHODS AS A TOOL IN ORGANOMETALLIC SYNTHESES - FACILITATION OF OXIDATIVE ADDITION TO PLATINUM(II)

High-pressure (2 GPa) batch reactors now commercially available may of fer substantial accelerations of organometallic syntheses, without res ort to heating, when the activation process is multicentered or involv es the generation and solvation of ions. as an example of the latter c lass of reactions, the kinetics of the oxidative additions of methyl a nd ethyl iodides (RI) to dimethyl(2,2'-bipyridine)platinum(II) in acet one have been studied over the pressure range 0-200 MPa. The volumes o f activation Delta V-1(not equal), if assumed to be constant over this range, are -11.7 +/- 0.3 and -9.7 +/- 0.7 cm(3) mol(-1), respectively , implying an acceleration of ca. 3000-fold for a batch synthesis of t his sort at 2 GPa. However, a possible slight pressure dependence of D elta V-1(not equal) may reduce this acceleration to ca. 1 000-fold. Th e Delta V-1(not equal) data and the 500-fold retardation on going from R = Me to R = Et are consistent with an S(N)2 attack of Pt-II on the alpha-carbon in the alkyl iodides, forming I- and [RMe(2)Pt(bpy)](+).