Palladium selenolates via oxidative addition of organylselenenyl halides to palladium(0) precursor and via cleavage reaction of diselenides: synthesis, structure and spectroscopic investigation

Abstract

Oxidative addition of bis[2-(4,4-dimethyl-2-oxazolinyl)phenyl] diselenide to Pd(PPh₃)₄ provided two different mononuclear palladium selenolato complexes, Pd(Se∩N)(PPh₃)Cl (4) [Se∩N=chelating 2-(4,4-dimethyl-2-oxazolinyl)phenylselenolate] and Pd(Se∩N)(Se∩N^∗)(PPh₃) (5) [Se∩N=chelating, Se∩N^∗=non-chelating 2-(4,4-dimethyl-2-oxazolinyl)phenylselenolato ligand] in dicholoromethane and toluene respectively. Complex 4 has also been synthesized by the oxidative addition of 2-(4,4-dimethyl-2-oxazolinyl)phenylselenenyl chloride to Pd(PPh₃)₄. The bromo and iodo analogs of 4 (9 and 10) were similarly synthesized by the oxidative addition of 2-(4,4-dimethyl-2-oxazolinyl)phenylselenenyl bromide and iodide, respectively to Pd(PPh₃)₄. The oxidative addition of 2-(N,N-dimethylaminomethyl)phenylselenenyl bromide and iodide to Pd(PPh₃)4 afforded mononuclear palladium selenolate complexes, Pd(Se∩N)(PPh₃)X (13 and 14) [Se∩N=chelating 2-(N,N-dimethylaminomethyl)phenylselenolate, X=Br: 13, X=I: 14]. The reactions of bis[2-(4,4-dimethyl-2-oxazolinyl)phenyl] diselenide and bis[2-(N,N-dimethylaminomethyl)phenyl] diselenide with Pd(COD)Cl₂ provided dinuclear selenolato-bridged complexes [PdCl(Se∩N)]₂ (15) [Se∩N=chelating 2-(4,4-dimethyl-2-oxazolinyl)phenylselenolate] and [PdCl(Se∩N)]₂ (19) [Se∩N=chelating 2-(N,N-dimethylaminomethyl)phenylselenolate] respectively. The complexes were characterized by elemental analysis and NMR (¹H and ⁷⁷Se) spectroscopy. Complexes 4 and 5 were also characterized by mass spectrometry. Molecular structures of 4, 5, 9, 14 and 15 have been established by single crystal X-ray diffraction analysis. Complexes 4 and 9 are isomorphous and crystallize in the space group P2₁/c of the monoclinic system where the selenolato and halo ligands are trans to each other. Complex 5 crystallizes in the space group P2₁/n of the monoclinic system where one chelating and one non-chelating selenolato ligands are trans to each other. Mononuclear complex 14 and binuclear centrosymmetric complex 15 crystallize in the P1̅ space group of the triclinic system.