A Complete Guide on the Influence of Metal Clusters in the Diels-Alder Regioselectivity of I-h-C-80 Endohedral Metallofullerenes

作者：Garcia Borras Marc; Osuna Silvia; Luis Josep M^*; Swart Marcel; Sola Miquel

来源：Chemistry - A European Journal, 2013, 19(44): 14931-14940.

DOI：10.1002/chem.201302202

• metal clusters
• cycloaddition
• density functional calculations
• Diels-Alder reactions
• fullerenes
• regioselectivity

The chemical functionalization of endohedral metallofullerenes (EMFs) has aroused considerable interest due to the possibility of synthesizing new species with potential applications in materials science and medicine. Experimental and theoretical studies on the reactivity of endohedral metallofullerenes are scarce. To improve our understanding of the endohedral metallofullerene reactivity, we have systematically studied with DFT methods the Diels-Alder cycloaddition between s-cis-1,3-butadiene and practically all X@I-h-C-80 EMFs synthesized to date: X=Sc3N, Lu3N, Y3N, La-2, Y-3, Sc3C2, Sc4C2, Sc3CH, Sc3NC, Sc4O2 and Sc4O3. We have studied both the thermodynamic and kinetic regioselectivity, taking into account the free rotation of the metallic cluster inside the fullerene. This systematic study has been made possible through the use of the frozen cage model (FCM), a computationally cheap approach to accurately predicting the exohedral regioselectivity of cycloaddition reactions in EMFs. Our results show that the EMFs are less reactive than the hollow I-h-C-80 cage. Except for the Y-3 cluster, the additions occur predominantly at the [5,6] bond. In many cases, however, a mixture of the two possible regioisomers is predicted. In general, [6,6] addition is favored in EMFs that have a larger charge transfer from the metal cluster to the cage or a voluminous metal cluster inside. The present guide represents the first complete and exhaustive investigation of the reactivity of I-h-C-80-based EMFs.

• 出版日期2013-10-25