SYNTHESIS, REACTIVITY AND MULTINUCLEAR N.M.R. STUDIES OF 2-(2-ARYLTELLUROETHYL)PYRIDINES AND THEIR PALLADIUM(II) AND PLATINUM(II) COMPLEXES: CRYSTAL STRUCTURES OF 4-MeO-C6H4TeCH2CH2-2-(C5H4N)MCl2(M = Pd,Pt)

Abstract

Abstract New organotellurium ligands (L), 2-(2-aryltelluro-ethyl)pyridines (a–d), (aryl = ph (a), 4-Me-C6H4 (b), 4-MeO-C6H4 (c) and 4-EtO-C6H4 (d)), and their complexes with palladium(II) and platinum(II) of the type MLCl2 [Ia–d(Pd); IIa–d (Pt)] have been synthesized. Addition of methanolic AgCIO4 to Ic/IIc in chloroform and subsequently an excess of (c) after removal of the precipitated AgCl results in the formation of [M(c)2] (CIO4)2 (III/IV). The bimetallic complexes [(c)Pd(μ-EPh)2M(dppe)]2+ (M = Pd/Pt, E = Se/Te, dppe = 1,2-bis (dephenylphosphino) ethane) (V–VIII) have been obtained by reaction of Pd(c)(MeOH)2 2+ with the metallo-ligands, (EPh)2 M(dppe). Elemental analyses, conductance and molecular weight measurements of these complexes, together with IR, electronic and NMR (1H, 125Te{1H}, 195Pt{1H} and 31P{1H} data suggest coordination of ligands (a–d) through tellurium and nitrogen. The structures of Ic and IIc have been determined by X-ray methods. Crystals belong to the triclinic crystal system, space group PΓ, with a – 9.061(1), b – 10.058(2), c – 13.044(1)Å, α – 96.38(1), β – 95.22(2), γ – 91.54(1)° and Z – 2 for Ic, and a – 9.030(1), b – 10.576(2), c – 13.074(2)Å, α = 96.18(1), β – 94.88(1), γ = 90.64(2)° and Z – 2 for IIc. The coordination about the metal atom is square planar; the two Cl atoms are cis to each other and the ligand forms a six-membered non-planar chelate ring around the metal atom with the tellurium atom as a centre of chirality. The Pd-Te distance is observed to be longer than that of the Pt-Te distance by some 0.04 Å. The M-Cl bond opposite to tellurium is longer than the other, a manifestation of the trans influence of the Te-C (methoxyphenyl) bond.