Preferred phosphine ligand for use in combination with Pd salts in the Heck-type coupling reactions of vinylic halides. For examples, see Palladium(II)- acetate. For a review of the Heck reaction, see: Org. React., 27, 345 (1982). The Pd-catalyzed amination of bromoarenes with 1-Boc-piperazine, in the presence of this ligand, provides a route to arylpiperazines of potential pharmacological interest: Tetrahedron Lett., 39, 2219 (1998).