Cationic platinum(II) - or palladium(II)-carbyl complexes and unsaturated substrates: a facile way to C-C bond formation

Alkenes, alkynes, 1,2- and 1,3-dienes react with [MR(N-N)(MeCN)](+) (M = Pt or Pd; R = hydrocarbyl group; N-N = bidentate nitrogen ligand) to give R-substituted derivatives. The organic fragment is generally retained within the metal environment in eta(1) or eta(3) coordination, except in the reaction of alkenes with Pd(II) complexes. In this case, a free R-substituted alkene is produced via a relatively fast beta-elimination process from a Pd-alkyl intermediate. Different regiochemistries are detected in the reaction between monosubstituted olefins (propene or styrene) and homologous Pt and Pd complexes. The Pt-C bond is always formed with the terminal unsubstituted alkene carbon, while a preference toward the internal carbon, particularly if phenyl-substituted, is observed with Pd species. Neutral [MCIR(N-N)] are markedly less reactive. In this case, when M = Pt, the unsaturated organic substrate generally adds to the metal affording fairly stable tbp five-coordinate complexes.