title: Spatial separation of covalent, ionic, and metallic interactions in Mg11Rh18B8 and Mg3Rh5B3.
abstract: 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 BRh 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.
authors.affiliation: Max-Planck-Institut für Chemische Physik Fester Stoffe, Nöthnitzer Str. 40, 01187 Dresden (Germany); Chemistry Department, Moscow State University, 119991, Moscow (Russia); MSU-MPG Partner Group and the Chemistry Department, Moscow State University, 119991, Moscow (Russia). alekseevaam@gmail.com.
authors.forename: Anastasia M
authors.initials: AM
authors.lastname: Alekseeva
authors.forename: Artem M
authors.initials: AM
authors.lastname: Abakumov
authors.forename: Andreas
authors.initials: A
authors.lastname: Leither-Jasper
authors.forename: Walter
authors.initials: W
authors.lastname: Schnelle
authors.forename: Yuri
authors.initials: Y
authors.lastname: Prots
authors.forename: Gustaaf Van
authors.initials: GV
authors.lastname: Tendeloo
authors.forename: Eugene V
authors.initials: EV
authors.lastname: Antipov
authors.forename: Yuri
authors.initials: Y
authors.lastname: Grin
keywords: X-ray diffraction; borides; coordination modes; magnesium; rhodium