Dinitrogen Cleavage and Hydrogenation by a Trinuclear Titanium Polyhydride Complex

• Published in: Science (American Association for the Advancement of Science) Vol. 340; no. 6140; pp. 1549 - 1552
• Main Authors: Shima, Takanori, Hu, Shaowei, Luo, Gen, Kang, Xiaohui, Luo, Yi, Hou, Zhaomin
• Format: Journal Article
• Language: English
• Published: Washington, DC American Association for the Advancement of Science 28.06.2013; The American Association for the Advancement of Science
• Subjects: Alkali metals; Aluminum; Ambient temperature; Ammonia; Atoms; Catalysis; Catalysts; Chemical bonding; Chemical reactions; Chemistry; chemists; Climate; Crystallography; Crystallography, X-Ray; Enzymes; Exact sciences and technology; General and physical chemistry; High temperature; Hydrides; Hydrogen bonds; Hydrogenation; Hydrogenolysis; Ligands; Magnetic Resonance Spectroscopy; Molecular chemistry; Molecules; Nitrogen; Nitrogen - chemistry; nitrogen fertilizers; nitrogenase; NMR; Nuclear magnetic resonance; Protons; Reactivity; Reduction; Searching; slicing; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Titanium; Titanium - chemistry; Veins; Titanium Complexes; Transition element complexes; Trinuclear complex; Organometallic compound; Enzymatic catalysis; Activation; Nitrogen; Chemical reactivity; Hydrogenation; Chemical reaction kinetics; Hydrido complex
• ISSN: 0036-8075; 1095-9203; 1095-9203
• DOI: 10.1126/science.1238663

Both the Haber-Bosch and biological ammonia syntheses are thought to rely on the cooperation of multiple metals in breaking the strong N=N triple bond and forming an N-H bond. This has spurred investigations of the reactivity of molecular multimetallic hydrides with dinitrogen. We report here the reaction of a trinuclear titanium polyhydride complex with dinitrogen, which induces dinitrogen cleavage and partial hydrogénation at ambient temperature and pressure. By ¹H and ¹⁵N nuclear magnetic resonance, x-ray crystallographic, and computational studies of some key reaction steps and products, we have determined that the dinitrogen (N₂) reduction proceeds sequentially through scission of a N₂ molecule bonded to three Ti atoms in a μ-η¹:η²:η²-end-on-side-on fashion to give a μ₂-N/μ₃-N dinitrido species, followed by intramolecular hydrogen migration from Ti to the μ₂-N nitrido unit.