Synthesis and structure of fullerene halides in the C 60 -(TiCl 4 + Br 2 ) system: Molecular structures of (C 60 Cl 5 )
- PDF / 663,392 Bytes
- 8 Pages / 612 x 792 pts (letter) Page_size
- 75 Downloads / 226 Views
CTURE OF ORGANIC COMPOUNDS
Synthesis and Structure of Fullerene Halides in the C60–(TiCl4 + Br2) System: Molecular Structures of (C60Cl5)2, C60X6, C60X8, and C60X24 (X = Cl, Br) S. I. Troyanova*, A. V. Burtseva, and E. Kemnitzb a
Department of Physical Chemistry, Faculty of Chemistry, Moscow State University, Moscow, 119991 Russia * e-mail: [email protected] b Chemistry Department, Humboldt University Berlin, Brook-Taylor Str. 2, Berlin, 12489 Germany Received April 16, 2008
Abstract—The reactions in the C60–(TiCl4 + Br2) system have been performed in ampoules at elevated temperatures. The molecular structure of the fullerene halides (C60Cl5)2, C60X6, C60X8, and C60X24 (X = Cl, Br) has been determined and refined using single-crystal X-ray diffraction. It has been established that an increase in the bromine concentration results in an increase in the number of halogen atoms attached to the fullerene cage and in an increase in the relative fraction of bromine atoms in mixed halogen derivatives from almost pure chlorides (C60Cl5)2 and C60Cl6 to halides C60X8 and C60X24 with a high relative bromine content. PACS numbers: 61.10.Nz, 61.48.+c, 61.66.Hg, 61.82.Rx DOI: 10.1134/S1063774509020126
INTRODUCTION Fullerene halides are important compounds used for the subsequent functionalization of fullerenes. Individual bromides of the compositions C60Br6, C60Br8, C60Br24, and C70Br10 can be prepared by direct reaction of the ë60 or ë70 fullerenes with liquid bromine or bromine in organic solvents, whereas chlorination with the participation of gaseous or liquid chlorine leads to the formation of complex chloride mixtures [1, 2]. A method for synthesizing the C60Cl6 chloride with the use of iodine monochloride was developed earlier by Birkett et al. [3]. In recent years, we have succeeded in developing effective techniques for preparing individual chlorides of the ë60 and ë70 fullerenes: C60Cl24 [4], C60Cl28 [5], C60Cl30 [5, 6], and C70Cl28 [4]. The method is based on the reaction of fullerenes with chlorides of elements with variable oxidation states: SbCl5, VCl4, PCl5, MoCl5, VOCl3, etc. [7]. Subsequently, it was established that a bromine solution in titanium tetrachloride is also a chlorinating agent. With this technique, we managed to synthesize the fullerene chloride C70Cl16 for the first time [8] and also to perform the synthesis of the C70Cl10 chloride [9], which was originally produced by the reaction of the ë70 fullerene with the ICl chloride in organic solvents [10]. Upon the reaction of a (TiCl4 + Br2) mixture with higher fullerenes, the C76Cl18 [11] and C78Cl18 [9] chlorides were isolated and their crystal and molecular structures were investigated. It turned out that the action of the (TiCl4 + Br2) mixture depends on the bromine concentration in the
system. At a low Br2 concentration, the product of the reaction with ë70 is the cationic dimer [(C70)2]2+ stabilized by (Ti3Cl13)– anions [9]. The same compound is formed upon the reaction of C70Br10 with TiCl4 [12]; i.e., the dehalogenation process occurs
Data Loading...
