Fullerenes DOI: 10.1002/ange.200905832 Saturnene Revealed: X-ray Crystal Structure of D 5d -C 60 F 20 Formed in Reactions of C 60 with A x MF y Fluorinating Agents (A = Alkali Metal; M = 3d Metal)** Natalia B. Shustova, Zoran Mazej, Yu-Sheng Chen, Alexey A. Popov, Steven H. Strauss,* and Olga V. Boltalina* New fluorinated carbon materials (FCMs) have been [1] and continue to be prepared and studied because of their extant or potential applications in energy storage, low-surface-energy coatings, low-dielectric materials, bioengineering, medicine, and lubrication. [2–6] One class of FCMs, fluorofullerenes (FFs), are known to have variable optical gaps [7] and have been used as dopants to improve the surface conductivity of diamond [8] and as components of LED devices. [9] One attractive feature of FFs that distinguishes them from most other FCMs is that they are molecular and in many cases have been isolated with 85 mol % purity or higher as single isomers with well-determined structures and well-determined, repro- ducible physicochemical properties. [10] These FFs include 13 C 60 F n compounds (n = 2, 4, 6, 8 (two isomers), 18, 20, 24, 36 (three isomers), 38, 48) and several dozen fluorinated higher fullerenes and heterofullerenes. [10] For any FF to become a practical component of an FCM for a particular application, its efficient synthesis and purification must be possible. However, selective syntheses, defined as reactions that produce at least 85 mol % of a single composition in the crude product mixture, are known for only three C 60 F n compositions, C 60 F 18 ,C 60 F 36 , and C 60 F 48 , [11–13] and only two of them, C 60 F 18 and C 60 F 48 , are produced as single isomers. We now report new reactions of C 60 with a variety of ternary metal fluorides A x MF y , in which A is an alkali metal and M is a high-valent 3d metal. Among the reactions reported is a selective synthesis of the composition C 60 F 44 . We also report a nonchromatographic purification of the pre- viously reported FF C 60 F 20 . [14] This alternative technique enabled us to verify the proposed Saturn-like structure of this compound by X-ray crystallography. The use of d-block metal fluorides as fluorinating agents (FAs) for the synthesis of FFs was first reported in 1995. [15] In general, these FAs are softer, more selective, and safer to use than F 2 , XeF 2 , or KrF 2 . [10] For example, the degree of fluorination (i.e., the value of n in the C 60 F n products) can be controlled by varying the oxidation state of the metal or by “adding” alkali metal fluorides (i.e., by using a mechanical mixture of AF and MF x or a ternary salt A x MF y ). [16] We carried out the reactions of C 60 and the FAs MF x or A x MF y listed in Table 1. Most of these FAs were used for fullerene fluorination for the first time (the exceptions are CoF 3 [12] and MnF 3 , KMnF 4 , and K 3 MnF 6 [16] ). The FAs can be roughly divided into two groups: those which produced C 60 F n FFs with I) n > 36 and II) n  36. The first group includes ternary metal fluorides containing Cr V , Ni IV , and Cu IV . These high-oxidation-state compounds produced FFs with n = 42, 44, and 46. In the case of Cs 2 CuF 6 under the reaction conditions indicated, the composition C 60 F 44 was synthesized selectively. The 19 F NMR spectrum of the reaction mixture showed that several C 60 F 44 isomers were probably present. In ongoing studies, we are attempting to develop selective syntheses for n = 42, 44, and 46 with these FAs and to separate the isomers produced by using all available means. The second group of FAs includes ternary salts containing Mn III and Co III . It is known that CoF 3 is a more active FA than MnF 3 . [16–18] In the present study, this difference is manifested in the FF products of C 60 fluorination under identical conditions: C 60 F 36 was formed primarily along with small amounts of C 60 F 18 and C 60 F 20 when MnF 3 was used, and C 60 F 38 and C 60 F 40 were formed primarily along with some C 60 F 36 when CoF 3 was used. It was also found that LiCoF 4 is a stronger FA than LiMnF 4 . However, neither K 3 CoF 6 nor K 3 MnF 6 produced any FFs, so their relative fluorinating abilities for C 60 cannot be compared. [*] N. B. Shustova, Prof. S. H. Strauss, Dr. O. V. Boltalina Department of Chemistry, Colorado State University Fort Collins, CO 80523 (USA) Fax: (+ 1) 970-491-1801 E-mail: steven.strauss@colostate.edu olga.boltalina@colostate.edu Dr. Z. Mazej Department of Inorganic Chemistry and Technology Joz ˇef Stefan Institute, 1000 Ljubljana (Slovenia) Dr. Y.-S. Chen ChemMatCARS, Center for Advanced Radiation Sources The University of Chicago c/o Advanced Photon Source/Argonne National Laboratory Argonne, IL 60439 (USA) Dr. A. A. Popov Department of Electrochemistry and Conducting Polymers Leibniz Institute for Solid State and Materials Research 01069 Dresden (Germany) [**] This research was supported by the U.S. NSF (grant No. CHE- 0707223), the Slovenian Research Agency (grant No. P1-0045, Inorganic Chemistry and Technology), and the Electrochemical Society (Fellowship to N.B.S.). ChemMatCARS Section 15 is principally supported by the U.S. NSF/U.S. DOE (grant No. CHE- 0822838). Use of the Advanced Photon Source was supported by the U.S. Department of Energy, Office of Basic Energy Sciences (contract No. DE-AC02-06CH11357). A.A.P. thanks the Humboldt Foundation for support. Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/anie.200905832. Zuschriften 824  2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Angew. Chem. 2010, 122, 824 –827