Orthopalladation of phosphorus ylides in endo position with bidentate ligands

摘要

The ortho-metallated complexes [Pd_2{κ~2(C,C)- C_6H_4(PPh_2CHC(O)C_6H _5R}_2(μ-Cl)_2] (R = Ph (1a), NO_2 (1b), Br (1c)) were prepared by refluxing equimolar mixtures of Ph _3PCHC(O)C_6H_5R, (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{κ~2(C,C)-C_6H_4(PPh_2CHC(O)R} L](OTf) [R = Ph, L = phen (2a), bipy (3a), dppe (4a), dppp (5a); R = NO 2, 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