Orthopalladation of phosphorus ylides in endo position with bidentate ligands

The ortho-metallated complexes [Pd₂{κ²(C,C)-C₆H₄(PPh₂CHC(O)C₆H₅R}₂(μ-Cl)₂] (R = Ph (1a), NO₂ (1b), Br (1c)) were prepared by refluxing equimolar mixtures of Ph₃PCHC(O)C₆H₅R, (R = Ph, NO₂, 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{κ²(C,C)-C₆H₄(PPh₂CHC(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.     

New orthopalladated complexes of phosphorus ylides: Crystal structure of [Pd{CH{P(C7H6)(p-tolyl)2}COCH3}Cl{P(p-tolyl)3}]

This work reports on the preparation of the complexes [PdCl₂(Y¹)₂], [PdCl₂(Y²)₂] (Y¹ = (p-tolyl)₃PCHCOCH₃ (1a); Y² = Ph₃PCHCO₂CH₂Ph (1b)), [Pd{CHP(C₇H₆)(p-tolyl)₂COCH₃}(μ-Cl)]₂ (2a), [Pd{CHP(C₆H₄)Ph₂CO₂CH₂Ph}(μ-Cl)]₂ (2b), [Pd{CH{P(C₇H₆)(p-tolyl)₂}COCH₃}Cl(L)] (L = PPh₃ (3a), P(p-tolyl)₃ (4a)) and [Pd{CH{P(C₆H₄)Ph₂}CO₂CH₂Ph}Cl(L)] (L = PPh₃ (3b), P(p-tolyl)₃ (4b)). Orthometallation and ylide C-coordination in complexes 2a–4b are demonstrated by an X-ray diffraction study of 4a.     

The orthopalladation dinuclear [Pd(L1)(μ-OAc)]2, [Pd(L2)(μ-OAc)]2 and mononuclear [Pd(L3)2] complexes with [N, C, O] or [N, O] containing ligands: Synthesis, spectral characterization, electrochemistry and catalytic properties

Treatment of the salicylaldimine ligands (L₁H, L₂H, L₃H, L₄H and L₅H) with palladium(II) acetate in absolute ethanol gave the orthopalladation dinuclear [Pd(L₁)(μ-OAc)]₂, [Pd(L₂)(μ-OAc)]₂ and mononuclear [Pd(L₃)₂] with the tetradentate ligands [N, C, O] or [N, O] moiety. The ligands L₁H and L₂H are coordinated through the imine nitrogen and aromatic ortho carbon atoms, whereas the ligand L₃H coordinated through the imine nitrogen and phenolic oxygens atoms. The Pd(II) complexes have a square-planar structure and were found to be effective catalysts for the hydrogenation of both nitrobenzene and cyclohexene. These metal complexes were also tested as catalysts in Suzuki-Miyaura coupling of aryl bromide in the presence of K₂CO₃. The catalytic studies showed that the introduction of different groups on the salicyl ring of the molecules effected the catalytic activity towards hydrogenation of nitrobenzene and cyclohexene in DMF at 25 and 45 °C. The Pd(II) complexes easily prepared from cheap materials could be used as versatile and efficient catalysts for different C-C coupling reactions (Suzuki-Miyaura reactions). The structure of ligands and their complexes was characterized by UV-Vis, FT-IR, ¹H and ¹³C NMR, elemental analysis, molar conductivity, as well as by electrochemical techniques.     

Synthesis and structure of mono- and di-nuclear complexes of ortho-palladated derived from phosphorus ylides

The phosphorus ylides Ph₃PCHC(O)C₆H₄R (R = 4-Me 1a, 4-Br 1b) react with PdCl₂ in equimolar ratios to give the C,C-orthopalladated [Pd{CHP(C₆H₄)Ph₂CO-C₆H₄-R)}(μ-Cl)]₂ (R = 4-Me 2a, 4-Br 2b) which react with NaClO₄/dppe, NaClO₄/dppm, py and PPh₃ to give the mononuclear derivatives [Pd{CH{P(C₆H₄)Ph₂}COC₆H₄-R}(dppe-P,P′)[(ClO₄) (R = 4-Me 3a, 4-Br 3b), [Pd{CH{P(C₆H₄)Ph₂}COC₆H₄-R}(dppm-P,P′)[(ClO₄ ( (R = 4-Me 4a, 4-Br 4b), [Pd{CH{P(C₆H₄)Ph₂}COC₆H₄-R}Cl(L)] (L = py, R = 4-Me 5a, 4-Br 5b, L = PPh₃, R = 4-Me 6a, 4-Br 6b). The C, C-metalated chelate are demonstrated by an X-ray diffraction study of 3a and 4a. Characterization of the obtained compounds was also performed by elemental analysis, IR, ¹H, ³¹P, and ¹³C NMR.