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(IBioxMeb>4b>)b>2b>(H)b>2b>}⁺ (<b>2b>), containing the conformationally rigid NHC ligand IBioxMeb>4b>, is reported. Hydrogenation of trans-[Ir(IBioxMeb>4b>)b>2b>(COE)Cl] (<b>1b>) in the presence of excess Na[BAr^Fb>4b>] leads to the formation of dimeric [{Ir(IBioxMeb>4b>)b>2b>(H)b>2b>}b>2b>Cl][BAr^Fb>4b>] (<b>3b>), which is structurally fluxional in solution and acts as a reservoir of monomeric <b>2b> in the presence of excess halogen ion abstractor. Stable dihydride complexes trans-[Ir(IBioxMeb>4b>)b>2b>(2,2鈥?bipyridine)(H)b>2b>][BAr^Fb>4b>] (<b>4b>) and [Ir(IBioxMeb>4b>)b>3b>(H)b>2b>][BAr^Fb>4b>] (<b>5b>) were subsequently isolated through in situ trapping of <b>2b> using 2,2鈥?bipyridine and IBioxMeb>4b>, respectively, and fully characterized. Using mixtures of <b>3b> and Na[BAr^Fb>4b>] as a latent source of <b>2b>, the reactive monomeric fragment鈥檚 reactivity was explored with excess ethylene and cyclooctene, and trans-[Ir(IBioxMeb>4b>)b>2b>(Cb>2b>Hb>4b>)b>2b>][BAr^Fb>4b>] (<b>6b>) and cis-[Ir(IBioxMeb>4b>)b>2b>(COD)][BAr^Fb>4b>] (<b>7b>) were isolated, respectively, through sacrificial hydrogenation of the alkenes. Complex <b>6b> 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 <b>7b> via transfer dehydrogenation of COE highlights the ability to partner IBioxMeb>4b> with reactive metal centers capable of C鈥揌 bond activation, without intramolecular activation. Reaction of <b>7b> with CO slowly formed trans-[Ir(IBioxMeb>4b>)b>2b>(CO)b>2b>][BAr^Fb>4b>] (<b>8b>), but the equivalent reaction with bis-ethylene <b>6b> was an order of magnitude faster, quantifying the strong coordination of COD in <b>7b>.