Chemical Reactivity of D_3h C₇₈ (Metallo)Fullerene: Regioselectivity Changes Induced by Sc₃N Encapsulation

Abstract

We report here for the first time a full comparison of the exohedral reactivity of a given fullerene and its parent trinitride template endohedral metallofullerene. In particular, we study the thermodynamics and kinetics for the Diels-Alder [4 + 2] cycloaddition between 1,3-butadiene and free D3h'-C78 fullerene and between butadiene and the corresponding endohedral D3h-Sc3N@C78 derivative. The reaction is studied for all nonequivalent bonds, in both the free and the endohedral fullerenes, at the BP86/TZP//BP86/DZP level. The change in exohedral reactivity and regioselectivity when a metal cluster is encapsulated inside the cage is profound. Consequently, the Diels-Alder reaction over the free fullerene and the endohedral derivative leads to totally different cycloadducts. This is caused by the metal nitride situated inside the fullerene cage that reduces the reactivity of the free fullerene and favors the reaction over different bonds.

Cycloaddition Reactions of Butadiene and 1,3‐Dipoles to Curved Arenes, Fullerenes, and Nanotubes: Theoretical Evaluation of the Role of Distortion Energies on Activation Barriers

“…Cycloaddition reactions of fullerene and its derivatives have been analyzed by considerations of bond lengths and orbital coefficients. [94,95] Short bond distances together with high pyramidalization angles are usually considered to be the most important structural parameters related to fullerene reactivity. On the other hand, low-lying unoccupied orbitals that present suitable energy and shape to interact are also required.…”

“…There are some cases where the previously mentioned parameters to understand cycloaddition reactions give contradictory predictions. The most pyramidalized bonds do not always lead to the most favorable addition; [94] those bonds with extremely long carbon distances can also be reactive. [95] Moreover, the predictions of reactivity from the LUMOs are qualitatively correct, but they are much too imprecise in the sense that one finds many bonds with suitable orbitals for the interaction with a diene or a 1,3-dipole.…”

“…[95] Moreover, the predictions of reactivity from the LUMOs are qualitatively correct, but they are much too imprecise in the sense that one finds many bonds with suitable orbitals for the interaction with a diene or a 1,3-dipole. [94] Although the distortion/interaction model requires to know the TS ge- www.chemeurj.org ometry, the correlation found between the distortion and the activation barrier is still of interest. In all different cycloadditions studied involving from small molecules to large systems (C 60 , nanotubes) the higher contribution to the activation barrier of these reactions comes from the energy required to distort both reactants rather than the interaction energy between them.…”

Reactivity differences of Sc3N@C2n (2n = 68 and 80). Synthesis of the first methanofullerene derivatives of Sc3N@D5h-C80

“…Unfortunately, we cannot compare our results with the monoadduct of Sc 3 N@D 5h -C 80 synthetized via a 1,3-dipolar cycloaddition 25,26 or to those calculated for the Diels-Alder additions, [36][37][38] because it has been shown that for endohedral fullerenes different reaction types yield different regioisomers. For example, 1,3-dipolar cycloadditions on Sc 3 N@I h -C 80 result in addition to [5,6]-bonds as the thermodynamic product, 39,40 while cyclopropanation reactions typically results in additions to [6,6]-bonds, 17 with only one exception reported.…”

Structural, electronic, and magnetoresponsive properties of triangular lanthanide clusters and their free‐standing nitrides

“…The metal-cage and intracluster bonding in endohedral metallofullerenes encapsulating among others La 2 and triangular La 3 N templates was studied in detail by quantum theory of atoms in molecules method. 38 Very recently 39,40 Osuna et al reported a full comparison of the exohedral reactivity of a given fullerene and its parent trinitride template endohedral metallofullerene. In particular, they studied the thermodynamics and kinetics for the Diels-Alder [4 1 2] cycloaddition between 1,3-butadiene and free D 3h -C 78 fullerene and between butadiene and the corresponding endohedral D 3h -Sc 3 N@C 78 and D 3h -Y 3 N@C 78 derivatives at the BP86/TZP//BP86/DZP level of theory.…”