Study on carbon–hydrogen activation of ketones by Gold(III) complexes and the synthesis and characterization of two ketonylgold(III) complexes

The acetonylgold(III) compound [Au(ppy)(CH2COCH3)Cl] (1) (ppy = 2-phenylpyridine) was unexpectedly obtained during the crystallization process of Au(III) lactate complex [Au(ppy)(CH3CHOHCOO−)Cl]. This new structure prompted us to further study the role of Au(III) complexes on the carbon–hydrogen activation of ketones. Complex [Au(ppy)(CH2COCH3)NO3] (2) was synthesized by reacting [Au(ppy)(NO3)2] with acetone while the ketonyl Au(III) complex [Au(apd)Cl2] (3) (Hapd = 2-acetylpyridine) was obtained through carbon–hydrogen bond activation of the acetyl group. The crystal structures of 1 and 2 have common features: a square–planar Au(III) centre coordinated by one five-membered chelate ring, one acetonyl ligand and one anion (chloride or nitrate). Both structures show that carbon–hydrogen activation of acetone by 2-phenylpyridine–Au(III) complexes leads to the formation of acetonyl–Au(III) complexes. The Au–CH2 bond lengths (2.067(7) Å, 1 and 2.059(5) Å, 2) are similar to each other but longer than the Au–C (phenyl) bond lengths. The two softest ligands (carbanion) are also cis to each other in the thermodynamically most stable isomer. In complex 3, the σ-bonded acetyl group is confirmed by 13C DEPT NMR spectroscopy.