HYBRID (TE,O) LIGANDS 2-(PHENYLTELLUROMETHYL)TETRAHYDRO-2H-PYRAN (L-1) AND 2-(2-(4-METHOXYPHENYL)TELLUORETHYL)-1,3-DIOXANE (L-2), AND THEIRPALLADIUM(II) AND PLATINUM(II) COMPLEXES

The nucleophilic reaction of in situ generated [ArTe-] with appropriat e organic halides has been used to synthesize 2-(phenyltelluromethyl)- tetrahydro-2H-pyran (L-1) and 2-(2-{4-methoxyphenyl}telluorethyl-1,3-d ioxane (L-2). 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) an d [M(phen)(L)(2)](ClO4)(2) [where M = Pd-II or Pt-II; L = L-1 or L-2, DPPE = 1,2-bis(diphenylphosphino)ethane], have been synthesized. Molec ular weight, conductance measurements, IR, UV-visible, H-1, Te-125-{H- 1} and P-31-{H-1} NMR spectra have been used to characterize L-1, L-2 and their complexes. Ligation of the two (Te,O) ligands, in all the co mplexes, except [M(L)(2)](ClO4)(2), is in the monodentate mode through tellurium only. [PtCl2(L)(2)]-type complexes exist in solution as a m ixture of cis and trans isomers, the latter being present in very high abundance. The complexes [PdCl2(L)(2)] exhibit only one v(Pd-Cl) betw een 340 and 350 cm(-1), consistent with a trans structure. The (1)J(Pt -Te) values (658-704 Hz) in the Te-125 NMR spectra of [Pt(L)(2)](ClO4) (2) and [Pt(PPh3)(2)(L)(2)](ClO4)(2) correspond to trans structures, w hich are supported in the second type of complexes by (1)J(Pt-P) (ca 3 000 Hz). The P-31 NMR spectral data indicate that the mixed ligand com plexes of Pd-II and Pt-II containing PPh3 and DPPE are isostructural. The chelate shifts in the Te-125 NMR spectra have been found to be lar ge and positive (113-127 ppm) when five-membered chelate rings are for med, but for six-membered chelation the shift is small and negative (- 15 to 19 ppm). The quenching of O-1(2) by [Pd(phen)(L)(2)](ClO4)(2) ha s been observed. (C) 1997 Elsevier Science Ltd.