A POLYMER-BOUND BIDENTATE-PHOSPHINE PALLADIUM COMPLEX AS A CATALYST IN THE HECK ARYLATION

Polymer-supported 1,2-bis(diisopropylphosphino)benz'ene Pd(II) complex 2 shows a higher level of catalytic activity than the structurally analogous monomeric Pd(II) complex 1 in the Heck arylation of methyl acrylate by iodobenzene. The polymer-supported Pd(II) complex has a much higher turnover number (by more than 1 order of magnitude) than either 1 or Pd(OAc)(2)/PPh(3) at synthetically useful concentrations of reagents. The reaction rate of the monomeric Pd(II) complex 1 is enhanced by electrochemical prereduction of Pd(II) to Pd(0). Deactivation in homogeneous solution via aggregation of the reactive complex to insoluble palladium metal clusters or by equilibration to a sterically blocked tetraphosphino complex is proposed to explain the higher catalytic activity of the polymer-supported Pd(II) complex than of its structurally analogous soluble monomer.