New features in coordination chemistry Valuable hints from X-ray analyses of endohedral metallofullerenes 配位化学英语论文.docVIP

Polyhedron 52 (2013) 3–9 Contents lists available at SciVerse ScienceDirect Polyhedron journal homepage: /locate/poly New features in coordination chemistry: Valuable hints from X-ray analyses of endohedral metallofullerenes Yun-Peng Xie a, Xing Lu a,b,?, Takeshi Akasaka b,?, Shigeru Nagase c State Key Laboratory of Material Processing and Die Mould Technology, College of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China bLife Science Center for Tsukuba Advanced Research Alliance, University of Tsukuba, Tsukuba, Ibaraki 305-8577, Japan cFukui Institute for Fundamental Chemistry, Kyoto University, Takano-Nishihiraki-cho 34-4, Sakyo-ku, Kyoto 606-8103, Japan a article info abstract The cage-like structure of fullerenes enables a new strategy for derivatization, that is, endohedral doping with metallic species. Distinctly different from exohedral metal-fullerene complexes, endohedral metal- lofullerenes (EMFs) show several new features in metal–carbon interactions which result from the elec- tron transfer from the internal metallic species to the outer carbon cage. Taking advantage of recent achievements in the X-ray crystallographic characterization of EMFs, it was revealed that the single metal cation in mono-EMFs are always apart from the cage center, coordinating with the cage from inside, dom- inantly via electrostatic interactions, whereas the metal–cage interactions are much weaker in di-EMFs, featuring a moving dimetallic cluster in most cases. Moreover, formation of various metallic cluster spe- cies inside the fullerene cage suggest that the strong coordination ability of rare earth metals which always requests a maximal coordinated stereo environments, is a critical factor controlling the formation of stable EMF compounds. Finally, the structural features of the fullerene cage, such as the symmetry, the shape and the size, are also found to exert fundamental in?uences on the metal location or motion.