1212
Aromaticity As Driving Force for Bingel-Hirsch Derivatization of Endohedral Metallofullerenes

Wednesday, May 14, 2014: 08:00
Bonnet Creek Ballroom XI, Lobby Level (Hilton Orlando Bonnet Creek)
S. Osuna, M. Garcia-Borràs (Institut de Química Computacional i Catàlisi, Departament de Química, Universitat de Girona), M. Swart (Institut de Química Computacional i Catàlisi, Departament de Química, Universitat de Girona, Institució Catalana de Recerca i Estudis Avançats (ICREA)), J. M. Luis (Institut de Química Computacional i Catàlisi, Departament de Química, Universitat de Girona), L. Echegoyen (University of Texas - El Paso), and M. Solà (Institut de Química Computacional i Catàlisi, Departament de Química, Universitat de Girona)
Functionalization of EMFs is mainly achieved via cycloaddition reactions, principally through Diels-Alder (DA), 1,3-dipolar and nucleophilic [2+1] Bingel-Hirsch (BH) additions. It has been shown that the strain induced by the inner metal cluster on the carbon structure plays an important role in determining the regioselectivity of the EMF exohedral functionalizations.1 Electronic effects are also essential due to the formal charge transfer from the metal cluster to the fullerene cage.2 In DA and 1,3-dipolar cases, the best criterion for chemical-reactivity predictions of EMFs is provided by a combination of short bond lengths, high pyramidalization angles, and appropriate shape of some of the LUMOs.1 However, there are some recent experimental examples of BH cycloadditions on non-IPR EMFs where the usually employed reactivity parameters are not able to reproduce the experimental observations.3 In this communication, we unveil that the driving force behind the BH addition on EMFs is the aromaticity. We have explored the complete BH reaction mechanism for Sc3N@D3h-C78 considering all non-equivalent addition sites.  This system is the perfect scenario for investigating the BH addition as the encapsulated metal cluster cannot freely rotate and, therefore, the effect of the cluster on the BH reactivity is directly investigated. Our results clearly show that the BH addition is governed by the aromaticity of the fullerene rings.4 The aromaticity of the carbon cage of the first step intermediate of the reaction dictates the BH addition. Based on these observations, we have proposed some general aromaticity-based rules that correctly predict the most suitable BH addition sites for experimentally studied EMFs.5

[Figure 1 here]

 

  1. S. Osuna, M. Swart and M. Solà, J. Am. Chem. Soc., 2009, 131, 129.
  2. M. Garcia-Borràs, A. Romero-Rivera, S. Osuna, J. M. Luis, M. Swart and M. Solà, J. Chem. Theory Comput., 2012, 8, 1671.
  3. N. Alegret, M. N. Chaur, E. Santos, A. Rodríguez-Fortea, L. Echegoyen and J. M. Poblet, J. Org. Chem., 2010, 75, 8299.
  4. M. Garcia-Borràs, S. Osuna, M. Swart, J.M. Luis, L. Echegoyen, and M. Solà, Chem. Commun. 2013, 49, 8767.
  5. M. Garcia-Borràs, S. Osuna, M. Swart, J.M. Luis, L. Echegoyen, and M. Solà, in preparation. 

See more of: Endofullerenes and Carbon Nanocapsules I
See more of: M5: Endofullerenes and Carbon Nanocapsules
See more of: Carbon Nanostructures and Devices
Previous Abstract | Next Abstract >>