Iridium Complexes of the Conformationally Rigid IBioxMe4 Ligand: Hydride Complexes and Dehydrogenation of Cyclooctene

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• 作者：Simone A. Hauser ; Ralf Tonner ; Adrian B. Chaplin
• 刊名：Organometallics
• 出版年：2015
• 出版时间：September 14, 2015
• 年：2015
• 卷：34
• 期：17
• 页码：4419-4427
• 全文大小：495K
• ISSN：1520-6041

文摘

A method for accessing the formally 14 VE iridium(III) hydride fragment {Ir(IBioxMe₄)₂(H)₂}⁺ (2), containing the conformationally rigid NHC ligand IBioxMe₄, is reported. Hydrogenation of trans-[Ir(IBioxMe₄)₂(COE)Cl] (1) in the presence of excess Na[BAr^F₄] leads to the formation of dimeric [{Ir(IBioxMe₄)₂(H)₂}₂Cl][BAr^F₄] (3), which is structurally fluxional in solution and acts as a reservoir of monomeric 2 in the presence of excess halogen ion abstractor. Stable dihydride complexes trans-[Ir(IBioxMe₄)₂(2,2鈥?bipyridine)(H)₂][BAr^F₄] (4) and [Ir(IBioxMe₄)₃(H)₂][BAr^F₄] (5) were subsequently isolated through in situ trapping of 2 using 2,2鈥?bipyridine and IBioxMe₄, respectively, and fully characterized. Using mixtures of 3 and Na[BAr^F₄] as a latent source of 2, the reactive monomeric fragment鈥檚 reactivity was explored with excess ethylene and cyclooctene, and trans-[Ir(IBioxMe₄)₂(C₂H₄)₂][BAr^F₄] (6) and cis-[Ir(IBioxMe₄)₂(COD)][BAr^F₄] (7) were isolated, respectively, through sacrificial hydrogenation of the alkenes. Complex 6 is notable for the adoption of a very unusual orthogonal arrangement of the trans-ethylene ligands in the solid state, which has been analyzed computationally using energy and charge decomposition (EDA-NOCV). The formation of 7 via transfer dehydrogenation of COE highlights the ability to partner IBioxMe₄ with reactive metal centers capable of C鈥揌 bond activation, without intramolecular activation. Reaction of 7 with CO slowly formed trans-[Ir(IBioxMe₄)₂(CO)₂][BAr^F₄] (8), but the equivalent reaction with bis-ethylene 6 was an order of magnitude faster, quantifying the strong coordination of COD in 7.