Polydentate chalcogen reagents for the facile preparation of Pd2 and Pd4 complexes

Abstract

The silylated organochalcogen reagents 1,2-(Me₃SiSCH₂)₂C₆H₄, 1a and 1,2-(Me₃SiSeCH₂)₂C₆H₄, 1b were prepared from the corresponding organobromides and lithium trimethylsilanechalcogenolate Li[ESiMe₃] (E = S, Se). They have been characterized by multinuclear NMR spectroscopy (¹H, ¹³C, ⁷⁷Se) and electrospray ionization mass spectrometry. 1a and 1b react under mild conditions with (1,3-bis(diphenylphosphino)propane)palladium(II) chloride, [PdCl₂(dppp)], to provide the dinuclear organochalcogenolate-bridged complexes [(dppp)₂Pd₂-μ-κ²S-{1,2-(SCH₂)₂C₆H₄}]X₂, [2a]X₂ and [(dppp)₂Pd₂-μ-κ²Se-{1,2-(SeCH₂)₂C₆H₄}]X₂, [2b]X₂ (X = Cl, Br) in good yield, respectively. Furthermore, the tetranuclear palladium complex [(dppp)₄Pd₄-μ-κ⁴S-{1,2,4,5-(SCH₂)₄C₆H₂}]X₄, [3]X₄ (X = Cl, Br) can be synthesized from the reaction of the tetrathiotetrasilane 1,2,4,5-(Me₃SiSCH₂)₄C₆H₂, and [PdCl₂(dppp)]. The structures of [2a]X₂, [2b]X₂ and [3]X₄ were determined by single crystal X-ray diffraction methods. A variety of NMR experiments including two-dimensional homonuclear and heteronuclear correlated spectra were used to probe the solution behaviour of the dinuclear complexes in more detail. These complexes were further characterized by electrospray ionization (ESI) mass spectrometry, and for [2a]X₂ and [2b]X₂, UV–Vis absorption spectroscopy.