Mild, Reversible Reaction of Iridium(III) Amido Complexes with Carbon Dioxide

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• 作者：Graham E. Dobereiner ; Jianguo Wu ; Michael G. Manas ; Nathan D. Schley ; Michael K. Takase ; Robert H. Crabtree ; Nilay Hazari ; Feliu Maseras ; Ainara Nova
• 刊名：Inorganic Chemistry
• 出版年：2012
• 出版时间：September 17, 2012
• 年：2012
• 卷：51
• 期：18
• 页码：9683-9693
• 全文大小：498K
• 年卷期：v.51,no.18(September 17, 2012)
• ISSN：1520-510X

文摘

Unlike some other Ir(III) hydrides, the aminopyridine complex [(2-NH₂鈥揅₅NH₄)IrH₃(PPh₃)₂] (1-PPh₃) does not insert CO₂ into the Ir鈥揌 bond. Instead 1-PPh₃ loses H₂ to form the cyclometalated species [(魏²-N,N-2-NH-C₅NH₄)IrH₂(PPh₃)₂] (2-PPh₃), which subsequently reacts with CO₂ to form the carbamato species [(魏²-O,N-2-OC(O)NH-C₅NH₄)IrH₂(PPh₃)₂] (10-PPh₃). To study the insertion of CO₂ into the Ir鈥揘 bond of the cyclometalated species, a family of compounds of the type [(魏²-N,N-2-NR-C₅NH₄)IrH₂(PR鈥?sub>3)₂] (R = H, R鈥?= Ph (2-PPh₃); R = H, R鈥?= Cy (2-PCy₃); R = Me, R鈥?= Ph (4-PPh₃); R = Ph, R鈥?= Ph (5-PPh₃); R = Ph, R鈥?= Cy (5-PCy₃)) and the pyrimidine complex [(魏²-N,N-2-NH-C₄N₂H₃)IrH₂(PPh₃)₂] (6-PPh₃) were prepared. The rate of CO₂ insertion is faster for the more nucleophilic amides. DFT studies suggest that the mechanism of insertion involves initial nucleophilic attack of the nitrogen lone pair of the amide on CO₂ to form an N-bound carbamato complex, followed by rearrangement to the O-bound species. CO₂ insertion into 1-PPh₃ is reversible in the presence of H₂ and treatment of 10-PPh₃ with H₂ regenerates 1-PPh₃, along with Ir(PPh₃)₂H₅.