Dichloro(pyridine-2-carboxamido-N1,N2)gold(III), a bis-nitrogen aurocycle: syntheses, gold-197 Mossbauer spectroscopy, and X-ray crystal structure

Abstract

The title compound 1, an N, N′-bis-coordinated gold(III) aurocycle, was obtained as an orange–yellow solid, m.p. 314–316 °C, upon heating an aqueous solution of HAuCl 4 with picolinamide or from NaAuCl 4 and picolinamide in water at ambient temperature. The IR spectrum of 1 showed a CO stretching frequency at 1650.8 cm −1. The 1H and 13C NMR spectra were consistent with a picolinamide complex. The 197Au Mossbauer spectrum of 1 is a doublet consistent with a distorted square planar coordinate Au(III) (QS=2.40 mm s −1, IS=3.22 mm s −1 relative to Au metal). Compound 1 crystallized in a monoclinic space group P2 1/ c with lattice constants a=8.738(2), b=5.935(1), and c=17.127(2) Å and β=90.88(2) with Z=4. The X-ray structure determination confirms that 1 is nearly square planar with the two rings being almost coplanar. The two AuCl bond lengths differ significantly.