Synthesis, characterization and biological activity of cycloaurated organogold(III) complexes with imidate ligands

Abstract

The reactions of the cycloaurated gold(III) complexes (2-bp)AuCl2 (2-bp = 2-benzylpyridyl) or (damp)AuCl2 (damp = Me2NCH2C6H4) with an excess of sodium saccharinate (Nasacc), potassium phthalimidate (Kphth), or with isatin and trimethylamine in refluxing methanol results in the successful isolation of a series of new gold(III) imidate complexes. These were characterised by NMR and IR spectroscopies, and by X-ray structure determinations on (2-bp)Au(sacc)2 and (2-bp)Au(phth)2. In both structures, the planes of the saccharinate and the phthalimidate ligands are orientated almost perpendicular to the gold coordination plane. As expected from trans-influence considerations, the Au-N(imidate) bond lengths trans to the aryl carbon atoms are longer than the Au-N(imidate) bond lengths trans to the pyridyl groups. The complexes have also been characterised by electrospray ionisation MS; in the presence of halide ligands, one imidate ligand is readily displaced. Anti-tumour (P388 murine leukemia) and selected anti-microbial data for the new complexes are reported. Surprisingly, all three damp complexes had low anti-tumour activity, which is likely to be a consequence of the poor solubility of these complexes. The synthesis and characterisation of a related gold(III) bis(amidate) complex derived from sulfathiazole is also described.