ALKYL HALIDE TRANSFER FROM PALLADIUM(IV) TO PLATINUM(II) AND A STUDY OF REACTIVITY, SELECTIVITY, AND MECHANISM IN THIS AND RELATED REACTIONS

Kinetic studies of the oxidative addition of Mel or PhCH2Br to [MMe2(L2)] (M = Pd or Pt, L2 = 2, 2'-bipyridine or 1, 10-phenanthroline) indicate that the reactions occur by the Sn2 mechanism, and the reactions occur 7–22 times faster when M = Pt over Pd and 1.2-2.2 times faster when L2 = phen over bpy. Reductive elimination from [PdBrMe2(CH2Ph)(L2)] in the solid state occurs to give both Me-Me and PhCH2Me, and there is a preference for methyl group loss. Thermochemical studies indicate that CH3-CH3 loss gives ΔH = -108 ± 4 kJ mol-1 but PhCH2-CH3 loss gives ΔH = -48 ± 12 kJ mol-1, indicating a relatively strong PhCH2-Pd bond. The complexes [PdIMe3(L2)] or [PdBrMe2(CH2Ph)(L2)] react rapidly with [PtMe2(L2)] by alkyl halide transfer. Kinetic studies have shown that the major route involves loss of halide from palladium(IV) in a preequilibrium step, followed by SN2 attack by [PtMe2(L2)] on an alkyl group of [PdMe3(L2)]+ or [PdMe2(CH2Ph)(L2)]+. In the latter case, benzyl group transfer is preferred over methyl group transfer. © 1989, American Chemical Society. All rights reserved.