Hybrid (Te,O) ligands 2-(phenyltelluromethyl)tetrahydro-2H-pyran (L1) and 2-(2-{4-methoxyphenyl}telluorethyl)-1,3-dioxane (L2), and their palladium(II) and platinum(II) complexes

Article abstract of DOI:10.1016/S0277-5387(96)00525-6

The nucleophilic reaction of in situ generated [ArTe^-] with appropriate organic halides has been used to synthesize 2-(phenyrtelluromethyl)-tetrahydro-2H-pyran (L¹) and 2-(2-{4-methoxyphenyl}telluorethyl-1,3-dioxane (L²). Their complexes with stoichiometries [MCl₂(L)₂],[M(L)₂](ClO₄) ₂, [M(DPPE)(L)₂](ClO₄)₂, [M(PPh₃)₂(L)₂](ClO₄)₂ and [M(phen)(L)₂](ClO₄)₂ [where M = Pd¹¹ or Pt¹¹; L = L¹ or L², DPPE = 1,2-bis(diphenylphosphino)ethane], have been synthesized. Molecular weight, conductance measurements, IR, UV-visible, ¹H, ¹²⁵Te-{¹H} and ³¹P-{¹H} NMR spectra have been used to characterize L¹, L² and their complexes. Ligation of the two (Te,O) ligands, in all the complexes, except [M(L)₂](ClO₄)₂, is in the monodentate mode through tellurium only. [PtCl₂(L)₂]-type complexes exist in solution as a mixture of cis and trans isomers, the latter being present in very high abundance. The complexes [PdCl₂(L)₂] exhibit only one v(Pd - Cl) between 340 and 350 cm^-1, consistent with a trans structure. The ¹J(Pt - Te) values (658-704 Hz) in the ¹²⁵Te NMR spectra of [Pt(L)₂](ClO₄)₂ and [Pt(PPh₃)₂(L)₂](ClO₄)₂ correspond to trans structures, which are supported in the second type of complexes by ¹J(Pt - P) (ca 3000 Hz). The ³¹P NMR spectral data indicate that the mixed ligand complexes of Pd¹¹ and Pt¹¹containing PPh₃ and DPPE are isostructural. The chelate shifts in the ¹²⁵Te NMR spectra have been found to be large and positive (113-127 ppm) when five-membered chelate rings are formed, but for six-membered chelation the shift is small and negative (-15 to 19 ppm). The quenching of ¹O₂ by [Pd(phen)(L)₂](ClO₄)₂ has been observed.