THE CIS-(PD-II(ME)(ALKENE)) FRAGMENT - STABILIZATION AND REACTIVITY

The reaction of trimethyloxonium tetrafluoroborate, Me3OBF4, with [Pd( dmf)(N,N-chelate)] precursors (N,N-chelate=1,10-phenanthroline (phen) or 2,9-Me-2-1,10-phenanthroline (dmphen); dmf=dimethylfumarate) has be en examined. When phen is present in the coordination sphere, the cycl ometallated square-planar complex [Pd{CH(CO2Me)CH(Me)COOMe)}(phen)]BF4 forms. Conversely, the more crowded dmphen stabilizes the five-coordi nate adduct [Pd(Me)(dmf)(dmphen)(H2O)]BF4. This species reacts with el ectron-rich olefins RCH=CH2 (R=H, Me, Ph) leading to the corresponding [Pd(Me)(RCH=CH2) (dmphen)(H2O)]BF4 compounds, which are not stable in solution and afford within a few hours propene, 2-methylpropene and E -beta-methylstyrene, respectively.