Preparation and Structure of CeSc 2 N@C 80 : An Icosahedral Carbon Cage Enclosing an Acentric CeSc 2 N Unit with Buried f Electron Spin Xuelei Wang, † Tianming Zuo, † Marilyn M. Olmstead, ‡ James C. Duchamp, § Thomas E. Glass, † Frank Cromer, † Alan L. Balch,* ,‡ and Harry C. Dorn* ,† Contribution from the Department of Chemistry, Virginia Polytechnic Institute and State UniVersity, Blacksburg, Virginia 24061, Department of Chemistry, UniVersity of California at DaVis, DaVis, California 95616, and Department of Chemistry, Emory & Henry College, Emory, Virginia 24327 Received March 1, 2006; E-mail: albalch@ucdavis.edu; hdorn@vt.edu Abstract: Herein, we report the preparation, purification, and characterization of a mixed trimetallic nitride endohedral metallofullerene, CeSc2N@C80. Single-crystal X-ray diffraction shows that CeSc2N@C80 consists of a four-atom asymmetric top (CeSc2N) inside a C80 (I h) carbon cage. Unlike the situation in most endohedrals of the M3N@C2n type, the nitride ion is not located at the center of the carbon cage but is offset by 0.36 Å in order to accommodate the large Ce III ion. The cage carbon atoms near the endohedral Ce and Sc atoms exhibit significantly larger pyramidal angles than the other carbon atoms on the C80 cage. Surprisingly, at ambient temperature, the 13 C NMR spectrum exhibits isotropic motional averaging yielding only two signals (3 to 1 intensity ratio) for the icosahedral C80 cage carbons. At the same temperature, the 45 Sc NMR exhibits a relatively narrow, symmetric signal (2700 Hz) with a small temperature- dependent Curie shift. A rotation energy barrier (Ea ) 79 meV) was derived from the 45 Sc NMR line-width analysis. Finally, the XPS spectrum for CeSc2N@C80 confirms a +3 oxidation state for cerium, Ce 3+ - (4f 1 5d 0 ).This oxidation state and the Curie shift are consistent with a weakly paramagnetic system with a single buried f electron spin. Introduction Since the beginning of fullerene chemistry, metal-containing endohedral fullerenes have attracted particular interest since the encapsulated metal atoms can impart unusual physical and chemical properties. 1-6 Also, the metal can readily donate charge to the cage which in certain cases stabilizes reactive empty cage fullerenes, such as the IPR-obeying C 74 7 (IPR ) isolated pentagon rule) and the non-IPR obeying C 66 8 and C 68 cages. 9 However, progress in exploring the structures and properties of endohedal metallofullerenes (EMFs) has been hampered by their low production yields and by purification difficulties. Nevertheless, in the past two decades, scandium, cerium, praseodymium, terbium, gadolinium, neodymium, lanthanum, erbium, holmium, dysprosium, lutetium, thulium, samarium, europium, and ytterbium have been encapsulated to yield a mono- or dimetallofullerene species via the Kra ¨tschmer- Huffman electric-arc process. 7,10-18 In 1996, the cerium mono- metallofullerene and di-metallofullerene, Ce@C 82 and Ce 2 @C 80 , were synthesized by Yang and co-workers. 16 The UV-vis- NIR absorption spectra and XPS patterns suggested that cerium in both Ce@C 82 and Ce 2 @C 80 should be in the Ce 3+ oxidation state, although earlier ab initio calculation suggested that the electronic structure of Ce@C 82 should be formally described as Ce 2+ @C 82 2- . 19 Recently, the magnetic properties of Ce@C 82 † Virginia Polytechnic Institute and State University. ‡ University of California at Davis. § Emory & Henry College. (1) Shinohara, H. Rep. Prog. Phys. 2000, 63, 843-892. (2) Akasaka, T.; Nagase, S. Endofullerenes: A New Family of Carbon Clusters; Kluwer Academic Publishers: Dordrecht, 2002. (3) Dunsch, L.; Krause, M.; Noack, J.; Georgi, P. J. Phys. Chem. Solids 2004, 65, 309-315. (4) Wilson, L. J.; Cagle, D. W.; Thrash, T. P.; Kennel, S. J.; Mirzadeh, S.; Alford, J. M.; Ehrhardt, G. J. Coord. Chem. ReV. 1999, 190-192, 199- 207. (5) Kato, H.; Kanazawa, Y.; Okumura, M.; Taninaka, A.; Yokawa, T.; Shinohara, H. J. Am. Chem. Soc. 2003, 125, 4391-4397. (6) Sun, D.; Liu, Z.; Guo, X.; Xu, W.; Liu, S. Fullerene Sci. Technol. 1997, 5, 137-143. (7) Kuran, P.; Krause, M.; Bartl, A.; Dunsch, L. Chem. Phys. Lett. 1998, 292, 580-586. (8) Wang, C. R.; Kai, T.; Tomiyama, T.; Yoshida, T.; Kobayashi, Y.; Nishibori, E.; Takata, M.; Sakata, M.; Shinohara, H. Nature 2000, 408, 426-427. (9) Stevenson, S.; Fowler, P. W.; Heine, T.; Duchamp, J. C.; Rice, G.; Glass, T.; Harich, K.; Hajdu, E.; Bible, R.; Dorn, H. C. Nature 2000, 408, 427- 428. (10) Lebedkin, S.; Renker, B.; Heid, R.; Schober, H.; Rietschel, H. Appl. Phys. A 1998, 66, 273-280. (11) Ding, J. Q.; Yang, S. H. J. Am. Chem. Soc. 1996, 118, 11254-11257. (12) Gu, G.; Huang, H. J.; Yang, S. H.; Yu, P.; Fu, J. S.; Wong, G. K.; Wan, X. G.; Dong, J. M.; Du, Y. W. Chem. Phys. Lett. 1998, 289, 167-173. (13) Hino, S.; Umishita, K.; Iwasaki, K.; Miyazaki, T.; Miyamae, T.; Kikuchi, K.; Achiba, Y. Chem. Phys. Lett. 1997, 281, 115-122. (14) Grannan, S. M.; Birmingham, J. T.; Richards, P. L.; Bethune, D. S.; De Vries, M. S.; Van Loosdrecht, P. H. M.; Dorn, H. C.; Burbank, P.; Bailey, J.; Stevenson, S. Chem. Phys. Lett. 1997, 264, 359-365. (15) Ding, X. Y.; Alford, J. M.; Wright, J. C. Chem. Phys. Lett. 1997, 269, 72-78. (16) (a) Ding, J. Q.; Weng, L. T.; Yang, S. H. J. Phys. Chem. 1996, 100, 11120- 11121. (b) Ding, J. Q.; Yang, S. H. Angew. Chem., Int. Ed. Engl. 1996, 35, 2234-2235. (17) Okazaki, T.; Lian, Y.; Gu, Z.; Suenaga, K.; Shinohara, H. Chem. Phys. Lett. 2000, 320, 435-440. Published on Web 06/17/2006 8884 9 J. AM. CHEM. SOC. 2006, 128, 8884-8889 10.1021/ja061434i CCC: $33.50 © 2006 American Chemical Society