Steric and Electronic Effects on Arylphosphonate Elimination from Organopalladium Complexes

To study the effects of electronic and steric manipulation of metal-bound aryl fragments on
arylphosphonate formation, model organopalladium complexes have been prepared and investigated. While
no phosphorus−carbon bond formation was observed at 25 °C, all of the arylpalladium phosphonates
underwent clean reductive elimination in C6D6 solutions at elevated temperatures. The incorporation of
electron-donating groups into the metal-bound aryl fragments accelerated the elimination process, while
palladium complexes containing aryl groups with electron-withdrawing or ortho substituents exhibited
slower elimination rates. While the rate of arylphosphonate formation was dependent upon the nature of
the metal-bound aryl fragment, it was rather insensitive to the identity of the phosphonate moiety. These
results demonstrate the results of subtle changes in the electronic and steric composition of the eliminating
species in P(O)−C bond-forming reactions.