Preparation,Structural Determination,and Characterization of Electronic Properties of Bis‐silylated and Bis‐germylated Lu3N@Ih‐C80

Bis‐silylated and bis‐germylated derivatives of Lu₃N@I_h‐C₈₀ ( 3 , 4 , 5 ) were successfully synthesized by the photochemical addition of disiliranes 1 a , 1 b or digermirane 2 , and fully characterized by spectroscopic, electrochemical, and theoretical studies. Interestingly, digermirane 2 reacts more efficiently than disiliranes 1 a and 1 b because of its good electron‐donor properties and lower steric hindrance around the Ge?Ge bond. The 1,4‐adduct structures of 3 , 4 , 5 were unequivocally established by single‐crystal X‐ray crystallographic analyses. The electrochemical and theoretical studies reveal that the energy gaps between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the 1,4‐adducts are remarkably smaller than those of Lu₃N@I_h‐C₈₀, because the electron‐donating groups effectively raise the HOMO levels. It is also observed that germyl groups are slightly more electron‐donating than the silyl groups on the basis of the redox properties and the HOMO–LUMO energies of 4 and 5 . Bis‐silylation and bis‐germylation are effective and versatile methods for tuning the electronic characteristics of endohedral metallofullerenes.     

Preparation,Structural Determination,and Characterization of Electronic Properties of [5,6]‐ and [6,6]‐Carbosilylated Sc3N@Ih‐C80

Photochemical carbosilylation of Sc₃N@I_h ‐C₈₀ with silirane 1 afforded two corresponding [5,6]‐adducts, 2 and 3 , and a [6,6]‐adduct, 4 . The structural and electronic properties of these products were characterized by means of spectroscopic, electrochemical, and theoretical methods. The structure of 2 was disclosed by means of single‐crystal X‐ray crystallographic analysis. Thermal isomerization of 3 to 2 was observed, whereas that of 2 to 3 proceeded less efficiently at 100 °C. Upon heating under the same conditions, adduct 4 underwent facile decomposition to afford Sc₃N@I_h ‐C₈₀, or isomerized into small amounts of 2 and 3 . The relative stabilities of 2 , 3 , and 4 were rationalized through the results of theoretical calculations. In contrast, adducts 2 , 3 , and 4 were stable under the photolytic conditions employed for carbosilylation. The photochemical functionalization of Sc₃N@I_h ‐C₈₀ represents a convenient synthetic method to obtain thermally labile fullerene‐based products.     

Cover Picture: Solid‐State Structural Characterization of Cutinase–ECE‐Pincer–Metal Hybrids (Chem. Eur. J. 17/2009)

The interfacial enzyme cutinase…? shown at the air–water interface on the cover, was site‐selectively modified with two different ECE‐pincer–metal complexes. The resulting cutinase–pincer–metal hybrids crystallized under halide‐rich conditions to give monomeric crystal structures, but also crystallized under halide‐poor conditions to form a metal‐induced dimer. See the Full Paper by R. J. M. Klein Gebbink, P. Gros, G. van Koten et al. on page 4270 ff. , for details of the chemistry and the crystal structures. Photograph: View from the island of Saba (Netherlands Antilles) taken by Birgit Wieczorek. Design: Birgit Wieczorek and Cornelis A. Kruithof.