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(PPh 3) 4 provided two different mononuclear palladium selenolato complexes, Pd(Se∩N)(PPh 3)Cl ( 4) [Se∩N = chelating 2-(4,4-dimethyl-2-oxazolinyl)phenylselenolate] and Pd(Se∩N)(Se∩N*)(PPh 3) ( 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(PPh 3) 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(PPh 3) 4. The oxidative addition of 2-( N, N-dimethylaminomethyl)phenylselenenyl bromide and iodide to Pd(PPh 3) 4 afforded mononuclear palladium selenolate complexes, Pd(Se∩N)(PPh 3)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)Cl 2 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 P2 1/ c of the monoclinic system where the selenolato and halo ligands are trans to each other. Complex 5 crystallizes in the space group P2 1/ 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 P 1 ¯ space group of the triclinic system.