Manganese(III)-Catalyzed Free Radical Reactions on Trimetallic Nitride Endohedral Metallofullerenes

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• 作者：Chunying Shu ; Ting Cai ; Liaosa Xu ; Tianming Zuo ; Jonathan Reid ; Kim Harich ; Harry C. Dorn ; Harry W. Gibson
• 刊名：Journal of the American Chemical Society
• 出版年：2007
• 出版时间：December 19, 2007
• 年：2007
• 卷：129
• 期：50
• 页码：15710 - 15717
• 全文大小：307K
• 年卷期：v.129,no.50(December 19, 2007)
• ISSN：1520-5126

文摘

The first reactions of trimetallic nitride templated endohedral metallofullerenes (TNT EMFs) withcarbon radicals generated from diethyl malonate catalyzed by manganese(III) acetate are reported. Twomethano monoadducts, Sc₃N@C₈₀-A and Sc₃N@C₈₀-B, were isolated and characterized. Sc₃N@C₈₀-Acontains two ester moieties, whereas Sc₃N@C₈₀-B contains only one ester group and a hydrogen atom onthe central carbon of the addend. NMR spectroscopy of the two monoadducts suggests that the additionoccurs regioselectively at a 6,6-ring juncture on the surface of the icosahedrally (I_h) symmetric Sc₃N@C₈₀,forming the first 6,6-ring-bridged methano I_h Sc₃N@C₈₀ derivatives. The measured ¹J_(C,H) = 147 Hz for themethano carbon with its hydrogen in monoadduct Sc₃N@C₈₀-B nearly perfectly matches the data for-homoaromatic systems, indicating an open [6,6]-methano structure. Geometry optimization also foundthat the "closed" [6,6]-methano structures were energetically unstable and always led to the open forms.Thus, an "open" [6,6]-methanofulleride structure is proposed, which was induced by the norcaradienerearrangement, resulting in the cleavage of the cyclopropane ring and the formation of energetically stableopen cage fullerene derivatives. These are the first examples of thermodynamically stable adducts of the"open" type at the 6,6-ring juncture of I_h Sc₃N@C₈₀, differing greatly from the "closed" 5,6-ring junctureadducts reported previously. In addition, bis-, tri-, and up to octaadducts of Sc₃N@C₈₀ were detected bymatrix-assisted laser desorption ionization time-of-flight mass spectrometry; this synthetic method was alsoapplied to Lu₃N@C₈₀, producing adducts with up to 10 substituents on the carbon cage. These are thehighest levels of substitution of TNT metallofullerenes reported so far.