Probing Gold’s Catalytic Prowess

Once thought to be mostly chemically inert, gold has been shown in recent years to display surprising catalytic activity. An international research team studying how gold binds to carbon has now discovered a further surprise behind gold’s catalytic prowess—an inverse correlation between bond strength and the multiplicity of Au–C bonds in organogold complexes (Nat. Commun. 2013, DOI: 10.1038/ncomms3223). Gold is a good catalytic activator of alkynes for C–C cross-coupling reactions. To understand why, Brown University’s Lai-Sheng Wang, Tsinghua University’s Jun Li, and coworkers took a close look at Au–C bonding. The researchers used AuI and HC≡CMgCl to create a series of complexes by electrospray ionization in a mass spectrometer and then probed them via photoelectron spectroscopy. They further modeled the complexes and compared the experimental and computational results. The most interesting observation, Wang says, is that the Au–C bond in ClAu–C≡CH^–, which one might expect to form during a cross-coupling reaction, is stronger than the double and triple bonds in ClAu=CH₂ and ClAu≡C species. The strong Au–C single bond explains gold’s ability to readily form the necessary alkyne intermediates in catalytic cross-couplings, the researchers conclude.