Synthesis and characterization of nickel and palladium complexes containing hetero-multidentate PNO ligands

Formation of mono- and dinuclear complexes containing ligands stemmed from the condensation of 2,6-diformyl-4-methylphenol derivatives with 2-(diphenylphosphino)aniline (P∼N) was investigated. Condensation of P∼N with 2,6-diformyl-4-methylanisole yielded the desired bis(imine-phosphine) L₃, but provided the cyclized benzoazaphospholium compound with 2,6-diformyl-4-methylphenol. Complexation of L₃ with (COD)PdCl₂ gave the dinuclear complex 4. On the other hand, L₃ underwent the intramolecular cyclization in the presence of (DME)NiCl₂ via the formation of benzoazaphospholium rings. Template condensation of 2,6-diformyl-4-methylphenol with P∼N in the presence of metal ions yielded the mononuclear nickel(II) and palladium(II) complexes, respectively.