In a coordinating solvent such as DMF, the
fast oxidative
addition of vinyl triflates to Pd0(PPh3)4
performed under stoichiometric conditions gives the cationic complexes [(η1-vinyl)Pd(PPh3)2(DMF)]+TfO-,
which have been characterized by conductivity measurements, electrospray mass
spectrometry, and NMR spectroscopy, before their decomposition to
vinylphosphonium salts [vinyl-PPh3]+TfO- and
Pd0 complexes. [(η1-vinyl)Pd(PPh3)2(DMF)]+TfO-
complexes are less stable than [(aryl)Pd(PPh3)2(DMF)]+TfO-
formed in the oxidative
addition of aryl triflates to Pd0(PPh3)4.
The rate constant of the oxidative addition
of vinyl triflates and bromides to Pd0(PPh3)4
has been determined and compared to that of aryl triflates and halides. The
following reactivity orders are established in DMF: vinyl-OTf
vinyl-Br > PhBr and vinyl-OTf
PhOTf.
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