This work has been digitalized and published in 2013 by Verlag Zeitschrift für Naturforschung in cooperation with the Max Planck Society for the Advancement of Science under a Creative Commons Attribution 4.0 International License. Dieses Werk wurde im Jahr 2013 vom Verlag Zeitschrift für Naturforschung in Zusammenarbeit mit der Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V. digitalisiert und unter folgender Lizenz veröffentlicht: Creative Commons Namensnennung 4.0 Lizenz. Crystal Structure of Bis(triethylammonium)c/ 0so-decahydrodecaborate, [(C2H5)3NH]2[B10H10] Kathrin Hofmann and Barbara Albert Institut für Anorganische und Analytische Chemie, Justus-Liebig-Universität, Heinrich-Buff-Ring 58, D-35392 Giessen Reprint requests to Dr. B. Albert. Fax: Int.(+49)641-9934109. E-mail: barbara.albert@anorg.chemie.uni-giessen.de Z. Naturforsch. 55 b, 499-503 (2000); received January 10, 2000 c/oso-Decahydrodecaborate(2-), Cage Symmetry The crystal structure of bis(triethylammonium)c/o5o-decahydrodecaborate [bis(triethylam- monium)decaboranate(lO)], [(CaHs^NHMBioHio], was determined and refined (space group Pmmn, no. 59, a = 989.7, b = 1333.7, c = 903.7 pm). The compound is a versatile starting material for many substances containing the [BioHio]2- entity and its derivatives. The c7oso-[BioHio]2- cluster is a bicapped square antiprism which is only slightly distorted. Its deviation from D^ symmetry is smaller than that of the Bio cages in every other compound containing this entity that have been structurally characterised. The presence of additional (N)H---B 3 interactions in form of multiple-centre bonds between the cations and the anions, which were postulated earlier and which should influence the cage symmetry, could not be confirmed. At 55 °C, the transition into a high temperature phase was investigated by X-ray powder diffraction. The high temperature phase crystallises in the tetragonal crystal system (a = 946.9, c = 1351.0 pm). Introduction Compounds containing the [BioHio]2“ entity have been known since 1959, when bis(tetra- methylammonium)decahydrodecaborate [bis(tetra- methylammonium)decaboranate( 10 )], [N(CH3)4]2- [BioHio], was synthesised [1]. Early NMR results as well as the application of MO theory led to the assumption, that the arrangement of the ten boron atoms is that of a c/oso-cluster in form of a bicapped square antiprism. The title com pound, [N(C2H5 )3H] 2 [B,oHio], was first prepared in 1959, too [2]. It turned out to be a versa tile starting material for many other salts con taining the closo- Bio entity, and has been charac terised thoroughly. However, the crystal structures of [N(CH3)4]2 [B 1 oH 1 o] and [N(C2H5)3H]2 [B 1 oH1 o] have never been determined. Several early at tempts of crystal structure determinations of hy droborates with the closo- Bio entity failed due to crystallographic problems, as described for K2[B 10H 10] * *H 20, [N(CH 3)4] 2 [BioH,o] * *H 20, and [NH 4 ] 2 [B,oHio] * jcH20 [3], Finally, in 1962, Dobrott and Lipscomb succeeded in determining and refining the crystal structure of Cu2[BioHio] and hereby proved the expected anion configura tion to be real [3]. For Cu2 [BioHio], Cu'---H---B interactions between the cation and the anion were discussed [3, 4], Today, our knowledge on derivatives of the closo- decahydrodecaborates is extremely broad. Many salts and molecules that contain [Bio(X,Y,Z)io] entities have been structurally characterised, es pecially by Preetz and co-workers (for example, see [5]), but only a few crystal structures of com pounds containing the unsubstituted [BioHio]2- an ion have been reported. These are: Cu^BioH^] [3], [((C6H5)3P) 2Cu]2 [B 1 oH 1 o] * CHCI3 [6 ], [UO?]- [B 10H 10] * 7C O (N H 2)2 [7 ],[(C 5 H5 )Fe(C5 H4CH2N- (CH3) 3] 2 [B,oH,o] [8 ], [C,oH9N 2] 2 [B,oH,o] [9, 10], [C.oHjoN^B.oH^] [9, 10], [(CH3) 3NH] 2 [B 1 oH 1 o] [11], [(C6H5)3(CH3)P]4[C24H72B40Hg4][B10H,0] * 2 CH3CN [12], [(C5 H5N)C 12H25] 2 [B,oHio] [13], and [(C5H5N) 2NH 2] 2 [B 10H, 0] * 2 H 20 [14]. It can be assumed that crystal growth and twin ning problems were the main reasons for the lim ited structural data for compounds with the closo- [BjoHio] anion. We therefore initiated a series of re crystallisation experiments and addressed the prob lem using powder diffractometry and single crys tal data, aiming to elucidate the crystal structure of the title compound, [N(C2H 5) 3H] 2 [BioHio]. This 0932-0776/00/0600-0499 $ 06.00 © 2000 Verlag der Zeitschrift für Naturforschung, Tübingen • www.znaturforsch.com K