Gold(III) Alkyne Complexes: Bonding and Reaction Pathways

The synthesis and characterization of hitherto hypothetical AuIII π‐alkyne complexes is reported. Bonding and stability depend strongly on the trans effect and steric factors. Bonding characteristics shed light on the reasons for the very different stabilities between the classical alkyne complexes of PtII and their drastically more reactive AuIII congeners. Lack of back‐bonding facilitates alkyne slippage, which is energetically less costly for gold than for platinum and explains the propensity of gold to facilitate C−C bond formation. Cycloaddition followed by aryl migration and reductive deprotonation is presented as a new reaction sequence in gold chemistry. Gold hat seine eigenen Gesetze: Die Synthese bisher nur vermuteter Gold(III)‐π‐Alkin‐Komplexe bestätigt, dass diese deutlich reaktiver sind als die entsprechenden klassischen Platin‐Alkinkomplexe. Die Alkinbindung in den Goldkomplexen unterliegt einem starken trans‐Einfluss: Die Liganden sind in trans‐Stellung zu einem Pyridin‐N‐Atom signifikant fester gebunden als trans zu einem negativ geladenen C‐Donor.