SYNTHESIS, REACTIVITY AND MULTINUCLEAR NMR-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)

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 AgClO4 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] (ClO4)2 (III/IV). The bimetallic complexes [(c)Pd(mu-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)22+ with the metallo-ligands, (EPh)2M(dppe). Elemental analyses, conductance and molecular weight measurements of these complexes, together with IR, electronic and NMR (H-1, Te-125{H-1}, Pt-195(H-1) and P-31{H-1}) 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 PT, with a - 9.061(1), b - 10.058(2), c - 13.044(1)angstrom, alpha - 96.38(1), beta - 95.22(2), gamma - 91.54(l)-degrees and Z - 2 for Ic, and a - 9.030(1), b - 10.576(2), c - 13.074(2) angstrom, alpha - 96.18(1), beta - 94.88(l), gamma - 90.64(2)-degrees 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 angstrom. The M-Cl bond opposite to tellurium is longer than the other, a manifestation of the trans influence of the Te-C (methoxyphenyl) bond.