Metal Atoms Collinear with the Spiro Carbon of 6,6-Open Adducts, M₂@C₈₀(Ad) (M = La and Ce, Ad = Adamantylidene)

Abstract

The photochemical reaction of M2@C80 (M = La and Ce) with 2-adamantane-2,3'-[3H]-diazirine (1) affords the corresponding adducts by carbene addition. The adducts were characterized by spectroscopic and single-crystal X-ray structure analyses. Crystallographic data for the adduct La2@C80(Ad) (2, Ad = adamantylidene) reveal that the two La atoms are collinear with the spiro carbon of the 6,6-open adduct. It is noteworthy that the La-La distance is highly elongated by the addition of carbene. Paramagnetic 13C NMR spectral analysis of the adduct Ce2@C80(Ad) (3) indicates that the two Ce atoms are also collinear with the spiro carbon at room temperature in solution. The unique metal positions were confirmed by density functional calculations.

Chemical, Electrochemical, and Structural Properties of Endohedral Metallofullerenes

“…[40,137] These results confirmed the electron-donating nature of the adamantylidene group towards the endohedral fullerene, since each addition of an adamantylidene group systematically shifted the first oxidation and first reduction towards more cathodic potentials. Interestingly, the magnitude of the shift was dependent on the position of the addend on the carbon cage, as nicely illustrated by the La 2 C 78 -adamentylidene monoadduct family, [40a] and by the number of addends.…”

“…Echegoyen and coworkers exploited this large difference in the oxidation potentials of the two isomers to separate them. [125] By choosing a chemical oxidant (tris(p-bromophenyl)aminium hexachloroantimonate, "magic blue") with a redox potential [137] 0.89 0.47 À0. 43 intermediate between those of the two isomers, the D 5h isomer was preferentially oxidized and removed from the mixture by simple filtration over SiO 2 .…”

A Spherical Molecule with a Carbon‐Free Ih‐C80 Topological Framework

“…[6] In this case the I h -symmetric isomer was also found in low yields; however, no crystallographic confirmation has been obtained for these spherical systems. Only by the functionalization of the endofullerenes La 2 @C 80 [7] and Sc 4 O@C 80 [8] was it possible to receive structural information about such derivatives by Xray crystallography in order to confirm the original icosahedral symmetry. …”

Buckyballs

“…Several reactions have already been reported considering these C 80 cages: carbene additions [201], radical trifluoromethylations [202], or free radical additions [203], even though cycloaddition reactions are the most effective way to generate covalent derivatives of endohedral metallofullerenes to date.…”