Reactivity of [Pd3(μ-OAc)3(μ,η2-MeSCHCO2Et-C,S)3] in the presence of triphenylphosphine: a model of the early steps of the Pd/PR3-catalysed Heck reaction
作者:Marino Basato*、Barbara Sesto、Marco Zecca*、Giovanni Valle、Sabrina Antonello、Flavio Maran*
DOI:10.1016/s0022-328x(00)00063-2
日期:2000.4
The stable complex [Pd(eta(1)-OAc)(eta(2)-MeSCHCO2Et-C,S)(PPh3)] (2) is readily formed by addition of triphenylphosphine to [Pd-3(mu-OAc)(3)(mu,eta(2)-MeSCHCO2Et-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 beta = 96.3(1)degrees, R(F) = 0.026, R-w (F-2)= 0.0765. The coordination of a second triphenylphosphine to the palladium atom leads to [Pd(eta(1)-OAc)CH(SMe)CO2Et}(PPh3)(2)] (3). Whereas 2 appears to be remarkably stable, 3, after a slow reductive elimination, evolves mainly to [Pd(eta(2)-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. (C) 2000 Elsevier Science S.A. All rights reserved.