Effect of Spectator Ligands on Haptotropic Rearrangements of Metal‐Azulene Complexes

• Published in: European journal of inorganic chemistry Vol. 2021; no. 44; pp. 4579 - 4585
• Main Authors: Guzmán‐Espinoza, Carlos Víctor, Ledesma‐Olvera, Lydia Gabriela, Barquera‐Lozada, José Enrique
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 25.11.2021
• Subjects: Amines; Azulene; Azulene complexes; Coordination compounds; Electron density; Haptotropic Rearrangements; Inorganic chemistry; Ligands; Molecular switch; Preferences; QTAIM; π back-donation
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.202100669

Azulene is a very remarkable ligand because of its zwitterionic character and the large variety of ways that it can coordinate with a metal. However, there is little knowledge about the factors that control the diversity of coordination modes in metal‐Azulene complexes. We carry out an energy and electron density analysis in the framework of DFT and QTAIM to understand how the nature of the spectator ligands affects the azulene‘s coordination preference in these systems. The results show that the π back‐donation plays a fundamental role in the coordination preference of the metal and also show that the π‐acidity of spectator ligands can be used to control inter‐ring haptotropic preferences. If the spectator ligands are strong acceptors as CO, the metal centre prefers to coordinate at the five‐membered ring. Meanwhile, poor acidic ligands as amines, favour a coordination to the seven‐membered ring. The azulene's zwitterionic character gives it the ability to coordinate to a metallic centre on any of its two rings depending on the spectator ligands π‐acidity nature. These ligands can control the haptotropic preferences in metal‐Azulene complexes. QTAIM shows that π back‐donation affects the coordination preference of the metal.