Co-ordination chemistry of dimethylgold(III). Synthesis, spectroscopic, and structural studies of complexes with neutral aromatic nitrogen-donor ligands

Abstract

Dimethylgold(III) nitrate reacts with neutral ligands to form the complexes [AuMe₂(tpm)]NO₃·2H₂O (tpm = tri-2-pyridylmethane) and [AuMe₂L]NO₃[L = tri-2-pyridylmethanol (tpmo), di-2-pyridylmethane (dpm), αα-di-2-pyridyltoluene (dpt), di-1-pyrazolylmethane (dpzm), and tri-1-pyrazolylmethane (tpzm)]. The crystal structures of complexes of tpzm, tpm, and dpt have been determined by single-crystal X-ray diffraction at 295 K and refined by least-squares methods to R= 0.033, 0.029, and 0.042 for 3 043, 1 616, and 2 529 independent ‘observed’ reflections, respectively. In these structures the [AuMe₂L]⁺ cations have essentially cis-square-planar co-ordination for gold(III), AuC₂N₂, with Au–C 2.023(7)–2.041(12)Å and Au–N 2.127(8)–2.142(8)Å. In complexes of the potential tridentate ligands one pyridyl group is not co-ordinated in the tpm complex, and one pyrazolyl group is involved in a weak axial Au ⋯ N interaction [3.139(7)Å] in the tpzm complex. Comparison of the ¹H n.m.r. spectra of complexes of the potentially tridentate ligands (tpzm, tpm, and tpmo) with model complexes of bidentate ligands (dpzm, dpm, and dpt) suggests that the co-ordination behaviour of the ligands in methanol resembles that found in the solid state. Crystal data: [AuMe₂(tpzm)]NO₃, monoclinic, space group P2₁/n, a= 16.72(1), b= 9.662(3), c= 10.700(4)Å, β= 107.83(3)°, Z= 4; [AuMe₂(tpm)]NO₃·2H₂O, orthorhombic, space group P2₁2₁2₁, a= 18.56(1), b= 11.150(7), c= 9.983(7)Å, Z= 4; [AuMe₂(dpt)]NO₃, monoclinic, P2₁/n, a= 14.142(6), b= 13.012(7), c= 10.372(3)Å, β= 100.60(3)°, Z= 4.