COMPLEXES OF GOLD(III) WITH MONONEGATIVE BIDENTATE N,O-LIGANDS

Gold(III) complexes of a variety of deprotonatable bidentate N,OH ligands have been prepared by direct reaction with [AuX(4)] - (X = Cl or Br). Schiff -base ligands 2-HOC6H4CH=NR, (R = Me, Et, Pr(i), Bu(n), CH-2Ph, or C6H11) give predominantly [Au(2-OC6H4CH=NR)2][AuCl4]; the monomeric neutral form [AuCl2(2-OC6H4CH=NR)] is always a minor product. 2-Pyridyl-methanol and -ethanol (HL) give simple complexes [AuX3(HL)] in the presence of excess of halide ion. These ligands and a range of substituted pyridine-2-carboxylic acids and quinolinecarboxylic acids (HL') give mono- and bis-chelated complexes [AuX2(L')] and [AuL'2]+. Some of the latter are capable of binding chloride ion to give five-co-ordinate complexes [AuCl(L')2]. When the ligand substituent is a hydroxy or carboxylic acid group another deprotonation step is possible to give neutral hydrogen-bonded polymeric [{AuL'(L' - H)}n] qr anionic [Au(L' - H)2] - complexes. Crystal structure data are reported for Na[Au(L' - H)2].4H2O (HL' = pyridine-2,5-dicarboxylic acid) and [AuX2(L')] (X = Cl or Br; HL' = pyridine-2-carboxylic acid: X = Cl, HL' = 3-hydroxypyridine-2-carboxylic acid), showing the expected square-planar geometry for gold with a trans arrangement for the bis(chelate).