Reactivity of [Pd3(μ-OAc)3(μ,η2-MeSCHCO 2Et-C,S)3] in the presence of triphenylphosphine: A model of the early steps of the Pd/PR3-catalysed Heck reaction

Article abstract of DOI:10.1016/S0022-328X(00)00063-2

The stable complex [Pd(η¹-OAc)(η²-MeSCHCO₂Et-C,S)(PPh ₃)] (2) is readily formed by addition of triphenylphosphine to [Pd₃(μ-OAc)₃(μ,η²-MeSCHCO ₂Et-C,S)₃] (1:1 P:Pd) in acetone. It crystallizes in the monoclinic space group C2/c, with Z=8, a=145.08(2), b=109.82(1), c=306.33(3) pm and β=96.3(1)°, R(F)=0.026, R_w (F²)=0.0765. The coordination of a second triphenylphosphine to the palladium atom leads to [Pd(η¹-OAc){CH(SMe)CO₂Et}(PPh₃) ₂] (3). Whereas 2 appears to be remarkably stable, 3, after a slow reductive elimination, evolves mainly to [Pd(η²-MeSCHCO₂Et-C,S)(PPh₃) ₂]^-. Zero-valent palladium species can also be generated by electrochemical reduction of 3. The rate constant for the oxidative addition of iodobenzene to the electrogenerated palladium(0) species has been estimated.