Preparation and NMR Spectroscopy of (1,2-Bis(diphenylphosphino)ethane)(η3-1,3-diarylallyl)- palladium Tetrafluoroborates. Correlation of Chemical Shifts with Hammett Substituent Constants and with the Regioselectivity of Nucleophilic Attack

13 C NMR chemical shifts of the terminal allyl carbon atoms C-1 and C-3 of (1,2-bis(diphenylphosphino)ethane)(η 3 -1,3-diarylallyl)palladium tetrafluoroborates correlate with σ Hammett substituent constants. For each complex the chemical shift at lower field indicates the site of preferred attack by soft nucleophiles in the Tsuji−Trost reaction.