Merrifield-diphenylphosphane Palladium Complexes

Abstract

[7440-05-3] (used as immobilized and reusable palladium catalysts in heterogeneous cross coupling, allylic substitutions, hydrogenation, and telomerization reactions1) Alternate Name: [Pd](PS-CH2PPh2) (PS = divinylbenzene-crosslinked polystyrene). Solubility: insoluble resins. Form Supplied in: not commercially available. The diphenylphosphanemethyl polystyrene ligand PS-CH2PPh2 is commercially available and is a 1–2% crosslinked divinylbenzene–styrene copolymer, 100–200 mesh, with loading of 0.90–1.40 mmol/g. Depending on the way of preparation (ligands, Pd/P ratio, and percentage of Pd), the palladium-containing resin shows from brown-red to yellow color. Analysis of Reagent Purity: the palladium content of the complexes can be determined by elemental analysis, ICP-AES, UV-VIS spectrophotometry,2 or X-ray diffraction.3 Preparative Methods: the palladium complexes are obtained by reaction of PS-CH2PPh2 with a palladium(II) salt or palladium(0) source, such as PdCl2 or Pd(PPh3)4, to give a supported palladium complex.1, 4 When a palladium salt is used, the formed supported palladium(II) can be transformed into a palladium(0) complex after treatment with hydrazine in the presence of triphenylphosphane.4 Recovery of the palladium catalyst is achieved by filtration or centrifugation after the reaction. The Merrifield-derived ligand PS-CH2PPh2 is obtained by reaction of the Merrifield resin with lithium diphenylphosphide.4 Handling, Storage, and Precaution: the complexes are usually stable when stored in air at room temperature.