Synthesis and characterization of bis(diphenylphosphino)methanide and -amide complexes of NiII and PdII. Crystal structure of [PdCl(Ph2PNPPh2)(PEt3)]

Abstract

The reaction of Li[Ph₂PYPPh₂](Y = CH or N) with [MX₂L₂](M = Ni or Pd; X = Cl or Br; L = PPh₃, PMe₂Ph or PEt₃) has been studied. With Y = CH only palladium derivatives [PdCl(Ph₂PCHPPh₂)L] were obtained; subsequent reaction with Grignard reagents, MgBr(R), gave [PdR(Ph₂PCHPPh₂)L](R = mesityl or o-tolyl). With Y = N, nickel and palladium complexes, [MX(Ph₂PNPPh₂)(PEt₃)], were obtained only with PEt₃. The compounds [Pd(Ph₂PNPPh₂)₂] or [{Ni(µ-Cl)(Ph₂PNPPh₂)}₂] were formed using PPh₃ or PMe₂Ph instead of PEt₃. Treatment of these complexes with HBF₄ yielded the corresponding cationic complexes containing the neutral chelate ligand. These complexes have been characterized by IR, ¹H and ³¹P NMR spectroscopy. The complex [PdCl(Ph₂PNPPh₂)(PEt₃)] crystallizes in the monoclinic space group C2/c, with a= 18.416(6), b= 11.702(4), c= 27.620(9)Å, β= 93.50(4)° and Z= 8. The P–N bond distances 1.64–1.65 Å are consistent with delocalization of the negative charge in the anionic ligand. The P ⋯ P distance, 2.440 Å, is close to a single P–P bond length.