Gold(III) Alkyne Complexes: Bonding and Reaction Pathways

• Published in: Angewandte Chemie International Edition Vol. 56; no. 44; pp. 13861 - 13865
• Main Authors: Rocchigiani, Luca, Fernandez‐Cestau, Julio, Agonigi, Gabriele, Chambrier, Isabelle, Budzelaar, Peter H. M., Bochmann, Manfred
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 23.10.2017; Wiley Subscription Services, Inc; John Wiley and Sons Inc
• Edition: International ed. in English
• Subjects: Alkynes; Aromatic compounds; Bonding strength; Chemical bonds; Chemical synthesis; Chemistry; Chemistry, Multidisciplinary; Communication; Communications; Congeners; Cycloaddition; density functional calculations; Gold; homogeneous catalysis; Migration; Physical Sciences; Platinum; reaction mechanisms; Science & Technology; Slippage; gold; density functional calculations; CATALYSIS; INSERTION; ACTIVATION; homogeneous catalysis; alkynes; reaction mechanisms; PLATINUM; REDUCTIVE ELIMINATION
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.201708640

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. Good as gold: The synthesis of hitherto hypothetical gold(III) π‐alkyne complexes highlights the differences between classical platinum alkyne complexes and their drastically more reactive AuIII congeners. Alkyne bonding in these complexes is subject to a strong trans influence, with ligands trans to a pyridine N atom being bound significantly more strongly than those trans to an anionic C donor.