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 [AuMe 2 (tpm)]NO 3 ·2H 2 O (tpm = tri-2-pyridylmethane) and [AuMe 2 L]NO 3 [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 [AuMe 2 L] + cations have essentially cis-square-planar co-ordination for gold(III), AuC 2 N 2, 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 1 H 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: [AuMe 2 (tpzm)]NO 3, monoclinic, space group P2 1 /n, a = 16.72(1), b = 9.662(3), c = 10.700(4) Å, β = 107.83(3)°, Z = 4; [AuMe 2 (tpm)]NO 3 ·2H 2 O, orthorhombic, space group P2 1 2 1 2 1, a = 18.56(1), b = 11.150(7), c = 9.983(7) Å, Z = 4; [AuMe 2 (dpt)]NO 3, monoclinic, P2 1 /n, a = 14.142(6), b = 13.012(7), c = 10.372(3) Å, β = 100.60(3)°, Z = 4.