Orthopalladation of phosphorus ylides in endo position with bidentate ligands

The ortho-metallated complexes [Pd(2){kappa(2)(C,C)-C(6)H(4)(PPh(2)CHC(O)C(6)H(5)R}(2)(mu-Cl)(2)] (R = Ph (1a), NO(2) (1b), Br (1c)) were prepared by refluxing equimolar mixtures of Ph(3)P=CHC(O)C(6)H(5)R, (R = Ph, NO(2), Br) and Pd(OAc)(2) in MeOH, followed by an excess of NaCl. The dinuclear complexes (1a-1c) react with silver trifluoromethylsulfonate and bidentate ligands [L = bipy (2,2'-bipyridine), phen (phenanthroline), dppe (bis(diphenylphosphino)ethane), dppp (bis(diphenylphosphino)propane)] giving the mononuclear stabilized orthopalladated complexes in endo position [Pd{kappa(2)(C,C)-C(6)H(4)(PPh(2)CHC(O)R}L](OTf) [R = Ph, L = phen (2a), bipy (3a), dppe (4a), dppp (5a); R = NO2, L = phen (2b), bipy (3b), dppe (4b), dppp (5b); R = Br, L = phen (2c), bipy (3c), dppe (4c), dppp (5c); OTf = trifluoromethylsulfonate anion]. Orthometalation and ylidic C-coordination are demonstrated by an X-ray diffraction study of 2c and 3c. In the structures, the palladium atom shows a slightly distorted square-planar coordination geometry