Mono- and binuclear orthopalladated complexes of phosphorus ylides containing nitrogen, phosphorus or bridging diphosphine ligands: Self-assembly, theoretical calculations and comparative catalytic activity

• Synthesize and characterization of orthopalladated complexes of phosphorus ylides.
• Synthesize and characterization of new bridging diphosphine complexes.
• Structural study and self-assembly of new synthesized complexes.
• Theoretical calculations to study between experiment and theory.
• Efficient catalytic activity of new complexes in the Suzuki coupling reactions.

Binuclear orthopalladated complexes of phosphorus ylides containing electron-withdrawing fluoro (Y1), bromo (Y2) or phenyl (Y3) substituent, [Pd{κ2(C,C)-[(C6H4-2)PPh2]CH(CO)C6H4X-4}(μ-Cl)]2 (X = F (1), Br (2), Ph (3)) were obtained by two different methods from the reaction of corresponding ylides and PdCl2 or Pd(OAc)2. The synthesized orthopalladated complexes 1 and 2 reacted with the monodentate ligands with various donor abilities affording the mononuclear complexes [PdCl{C,C-{CH[P(C6H4-2)Ph2]C(O)C6H4X-4]}}L] [L = triphenylphosphine (X = Cl (1a), X = Br (2a)); 3-methylpyridine (X = Cl (1b), X = Br (2b)); 4-methylpyridine (X = Br (2c)); 2,4,6-trimethylpyridine (X = Cl (1c)); pyridine (X = Cl (1d)); piperidine (X = Cl (1e)). The reaction of chloro-bridged complex 3 with bis(diphenylphosphino)ethane, dppe, and bis(diphenylphosphino)propane, dppp, in the 1:1 ratio occurred to give the symmetrical bridged complexes of general formula [Pd2Cl2{C,C-{CH[P(C6H4-2)Ph2]C(O)C6H4X-4]}2}}(μ-PˆP)] (PˆP = dppe (3a) and dppp (3b)). New complexes were fully characterized by elemental analysis, IR and NMR spectroscopies. The crystal structures of 1, 1a, 2a, 3 and 3a were determined by single-crystal X-ray diffraction analysis that revealed the self-assembly of complexes via the short contacts between donor and acceptor groups to form polymer, sheet or network supramolecular structures. Density functional theory (DFT) calculations for complexes 1, 1a and 2a indicated the good agreement with the experimental value reported in this work. The catalytic activity of 1, 1a and 2a were comparatively studied in the Suzuki cross-coupling reactions which showed the more efficiency of mononuclear complex 1a with fluoro substituent.

This paper provides the preparation of orthopalladated complexes of phosphorus ylides with nitrogen, phosphorus and bridging diphosphine ligands. According to the structural data, complexes self-assembled to form supramolecular structures. Theoretical results showed the good agreement between the calculated and experimental data. Complexes were comparatively evaluated in the Suzuki cross-coupling reactions.Figure optionsDownload as PowerPoint slide