The Shape of the Sc2(μ2-S) Unit Trapped in C82: Crystallographic, Computational, and Electrochemical Studies of the Isomers, Sc2(μ2-S)@Cs(6)-C82 and Sc2(μ2-S)@C3v(8)-C82

Document Type

Article

Publication Date

5-1-2011

Department

Chemistry and Biochemistry

School

Mathematics and Natural Sciences

Abstract

Single-crystal X-ray diffraction studies of Sc2(μ2-S)@Cs(6)-C82·NiII(OEP)·2C6H6 and Sc2(μ2-S)@C3v(8)-C82·NiII(OEP)·2C6H6 reveal that both contain fully ordered fullerene cages. The crystallographic data for Sc2(μ2-S)@Cs(6)-C82·NiII(OEP)·2C6H6 show two remarkable features: the presence of two slightly different cage sites and a fully ordered molecule Sc2(μ2-S)@Cs(6)-C82 in one of these sites. The Sc−S−Sc angles in Sc2(μ2-S)@Cs(6)-C82 (113.84(3)°) and Sc2(μ2-S)@C3v(8)-C82 differ (97.34(13)°). This is the first case where the nature and structure of the fullerene cage isomer exerts a demonstrable effect on the geometry of the cluster contained within. Computational studies have shown that, among the nine isomers that follow the isolated pentagon rule for C82, the cage stability changes markedly between 0 and 250 K, but the Cs(6)-C82 cage is preferred at temperatures ≥250 °C when using the energies obtained with the free encapsulated model (FEM). However, the C3v(8)-C82 cage is preferred at temperatures ≥250 °C using the energies obtained by rigid rotor−harmonic oscillator (RRHO) approximation. These results corroborate the fact that both cages are observed and likely to trap the Sc2(μ2-S) cluster, whereas earlier FEM and RRHO calculations predicted only the Cs(6)-C82 cage is likely to trap the Sc2(μ2-O) cluster. We also compare the recently published electrochemistry of the sulfide-containing Sc2(μ2-S)@Cs(6)-C82 to that of corresponding oxide-containing Sc2(μ2-O)@Cs(6)-C82.

Publication Title

Journal of the American Chemical Society

Volume

133

Issue

17

First Page

6752

Last Page

6760

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