Functionalization of Carbon Dioxide with Ethylene at Molybdenum Hydride Complexes

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• 作者：Yuanyuan Zhang ; Brian S. Hanna ; Andrew Dineen ; Paul G. Williard ; Wesley H. Bernskoetter
• 刊名：Organometallics
• 出版年：2013
• 出版时间：July 22, 2013
• 年：2013
• 卷：32
• 期：14
• 页码：3969-3979
• 全文大小：460K
• 年卷期：v.32,no.14(July 22, 2013)
• ISSN：1520-6041

文摘

The molybdenum tetrahydride species (Triphos)MoH₄PPh₃ (Triphos = PhP(CH₂CH₂PPh₂)₂) generated from sodium triethylborohydride addition to (Triphos)MoCl₃ was found to promote CO₂ functionalization to afford acrylate, propionate, and formate species. The formation of (Triphos)MoH₄PPh₃ occurs via a (Triphos)Mo(H)Cl(PPh₃) intermediate followed by dismutation of an unobserved six-coordinate molybdenum(II) dihydride complex. Addition of dihydrogen to the dismuation product mixture affords a nearly quantitative yield of (Triphos)MoH₄PPh₃. The molybdenum tetrahydride species facilitates CO₂ insertion into a metal hydride to produce a formate complex, (Triphos)Mo(H)(魏²-CHO₂)(PPh₃), with an observed rate constant of [2.9(2)] 脳 10^鈥? s^鈥? (25 掳C), which is independent of CO₂ pressure. Selective formation of acrylate and propionate carbon dioxide鈥揺thylene coupling products, (Triphos)Mo(H)(魏²-C₃H₃O₂)(PPh₃) and (Triphos)Mo(H)(魏²-C₃H₅O₂)(PPh₃), was achieved by sequential addition of olefin and heterocumulene to (Triphos)MoH₄PPh₃. A formally zerovalent TriphosMo(畏²-C₂H₄)₃ intermediate was characterized by NMR spectroscopy and computational analysis along the pathway for carbon dioxide鈥揺thylene coupling.