Synthesis and Characterization of Gold(III) Halide Complexes of Quinaldic Acid (Hqd), Methyl Quinaldate and Ethyl Quinaldate, and X-Ray Structure of [(HQd)₂H] [AuBr₄].H₂O

Abstract

Complexes of the types HAuX₄.2HQd, where X = Cl or Br and HQd = quinaldic acid, and AuX₃L₂, where L is methyl or ethyl quinaldate , have been prepared and characterized. Quinaldic acid as well as methyl and ethyl quinaldates function as monodentate ligands in these complexes, whose stereochemistries are discussed in relation to the number of gold-halogen stretching frequencies observed in their far-infrared spectra. The measured conductivities of these complexes are also discussed. Single-crystal X-ray analysis of monohydrated HAuBr₄.2HQd revealed that it should be formulated as [( HQd )₂H][AuBr₄].H₂O, in which a pair of zwitterionic HQd moieties are connected by a strong O...H...O hydrogen bond, and the gold(III) atom is in an elongated octahedral coordination environment with two long Au-O bonds of 3.388(8) and 3.440(8)Ǻ.