Reaction of Nitromethane with an Iridium Pincer Complex. Multiple Binding Modes of the Nitromethanate Anion

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• 作者：Xiawei Zhang ; Thomas J. Emge ; Rajshekhar Ghosh ; Karsten Krogh-Jespersen ; and Alan S. Goldman
• 刊名：Organometallics
• 出版年：2006
• 出版时间：February 27, 2006
• 年：2006
• 卷：25
• 期：5
• 页码：1303 - 1309
• 全文大小：145K
• 年卷期：v.25,no.5(February 27, 2006)
• ISSN：1520-6041

文摘

The reaction of nitromethane with (PCP)Ir (PCP = ³-2,6-(^tBu₂PCH₂)₂C₆H₃) yields the bidentate O,O-ligated nitromethanate complex (PCP)Ir(H)(²-O,O-NO₂CH₂) (1). Reaction of 1 with CO affords a COadduct with a mono-oxygen-ligated nitromethanate, 2, which represents the first characterized transitionmetal mono-oxygen-ligated nitromethanate complex. At elevated temperature, complex 2 isomerizes togive the carbon-bound nitromethyl complex 3. Complex 1 also undergoes addition of cyclohexylisocyanide(analogous to the reaction with CO) to form the mono-oxygen-ligated nitromethanate complex 4, whichalso isomerizes to form the corresponding nitromethyl complex, 5. The (PCP)Ir-(CH₃NO₂) system is thefirst species known to display three binding modes with a nitromethanate anion. Results from densityfunctional calculations illustrate the structures and energies of the minima and transition states on thepotential energy surfaces. The calculations suggest that 1 is the thermodynamic product of (PCP)Ir reactingwith nitromethane; a kinetic product, formed via oxidative addition of a nitromethane C-H bond, shouldreadily rearrange to form 1.