Spatial Separation of Covalent, Ionic, and Metallic Interactions in Mg11Rh18B8 and Mg3Rh5B3

• Published in: Chemistry : a European journal 2013-12, Vol.19 (52), p.17860-17870
• Main Authors: Alekseeva, Anastasia M., Abakumov, Artem M., Leither-Jasper, Andreas, Schnelle, Walter, Prots, Yuri, Tendeloo, Gustaaf Van, Antipov, Eugene V., Grin, Yuri
• Format: Article
• Language: English
• Subjects: borides; Chemistry; coordination modes; magnesium; rhodium; X-ray diffraction
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201301512

The crystal structures of Mg11Rh18B8 and Mg3Rh5B3 have been investigated by using single‐crystal X‐ray diffraction. Mg11Rh18B8: space group P4/mbm; a=17.9949(7), c=2.9271(1) Å; Z=2. Mg3Rh5B3: space group Pmma; a=8.450(2), b=2.8644(6), c=11.602(2) Å; Z=2. Both crystal structures are characterized by trigonal prismatic coordination of the boron atoms by rhodium atoms. The [BRh6] trigonal prisms form arrangements with different connectivity patterns. Analysis of the chemical bonding by means of the electron‐localizability/electron‐density approach reveals covalent BRh interactions in these arrangements and the formation of BRh polyanions. The magnesium atoms that are located inside the polyanions interact ionically with their environment, whereas, in the structure parts, which are mainly formed by Mg and Rh atoms, multicenter (metallic) interactions are observed. Diamagnetic behavior and metallic electron transport of the Mg11Rh18B8 and Mg3Rh5B3 phases are in agreement with the bonding picture and the band structure. Spaces, the final frontier: The crystal structures of Mg11Rh18B8 and Mg3Rh5B3 are characterized by different arrangements of the [BRh6] trigonal prisms. Electron‐localizability/electron‐density reveals the formation of covalently bonded BRh polyanions. Mg atoms inside the polyanions interact ionically with their environment, whereas in the structure parts, multicenter (metallic) Mg/Rh interactions are found.