Torsion Effects Beyond the δ Bond and the Role of π Metal‐Ligand Interactions

• Published in: Advanced science 2024-07, Vol.11 (25), p.e2401293-n/a
• Main Authors: Inchausti, Almudena, Mollfulleda, Rosa, Swart, Marcel, Perles, Josefina, Herrero, Santiago, Baonza, Valentín G., Taravillo, Mercedes, Lobato, Álvaro
• Format: Article
• Language: English
• Subjects: bidentate ligands; Chemistry; diruthenium; electronic structure; Electrons; Ligands; metal–metal bond; Oxidation; paddlewheel; Standard deviation
• ISSN: 2198-3844; 2198-3844
• DOI: 10.1002/advs.202401293

Previous studies on bimetallic paddlewheel compounds have established a direct correlation between metal–metal distance and ligand torsion angles, leading to the rule that higher torsion results in longer metal‐metal bond distances. Here, the new discovery based on diarylformamidinate Ru₂⁵⁺ paddlewheel compounds [Ru2Cl(DArF)4] that show an opposite behavior is reported: higher torsions lead to shorter metal–metal distances. This discovery challenges the assumption that internal rotation solely impacts the δ bond. By combining experimental and theoretical techniques, it is demostrated that this trend is associated with previously overlooked π metal‐ligand interactions. These π metal‐ligand interactions are a direct consequence of the paddlewheel structure and the conjugated nature of the bidentate ligands. This findings offer far‐reaching insights into the influence of equatorial ligands and their π‐conjugation characteristics on the electronic properties of paddlewheel complexes. That this effect is not exclusive of diruthenium compounds but also occurs in other bimetallic cores such as ditungsten or dirhodium is demonstrated, and with other ligands showing allyl type conjugation. These results provide a novel approach for fine‐tuning the properties of these compounds with significant implications for materials design. Recent research challenges established notions in bimetallic paddlewheel compounds. Contrary to prior findings, higher torsion results in shorter metal–metal distances, not longer. This anomaly, attributed to overlooked π metal‐ligand interactions, highlights the importance of the π conjugated nature of the equatorial ligands in the electronic structure of metal–metal compounds, and offers new avenues for precise design of bimetallic compounds.