Complexes of gold(III) with mononegative bidentate N,O-ligands

Abstract
Gold(III) complexes of a variety of deprotonatable bidentate N,OH ligands have been prepared by direct reaction with [AuX4](X = Cl or Br). Schiff-base ligands 2-HOC6H4CHNR, (R = Me, Et, Pri, Bun, CH2Ph, or C6H11) give predominantly [Au(2-OC6H4CHNR)2][AuCl4]; the monomeric neutral form [AuCl2(2-OC6H4CHNR)] 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] or 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).

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