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Licensed Unlicensed Requires Authentication Published by De Gruyter (O) May 3, 2011

Syntheses, crystal structures, magnetic properties and vibrational spectra of nitridoborate-halide compounds Sr2[BN2]Br and Eu2[BN2]X (X = Br, I) with isolated [BN2]3– units

Ilkin Kokal, Umut Aydemir, Yurii Prots, Walter Schnelle, Lev Akselrud, Peter Höhn and Mehmet Somer

Abstract

The title compounds Sr2[BN2]Br (1), Eu2[BN2]Br (2) and Eu2[BN2]I (3) were obtained from reactions of mixtures of Sr3[BN2]2 and SrBr2 (1) and the binaries EuN, h-BN and EuX2 (X = Br, I) (2, 3), respectively. The crystal structure of Sr2[BN2]Br was solved from X-ray powder diffraction data and those of the europium compounds from X-ray single crystal data. Sr2[BN2]Br and Eu2[BN2]Br are isotypic crystallizing in the rhombohedral space group R-3m (No. 166, Pearson code: hR18; Z = 3; a = 4.11692(2) Å, c = 26.4611(2) Å (1); a = 4.0728(3) Å, c = 26.589(3) Å (2)). The crystal structures are built up by layers of condensed edge-sharing [B—N—B]@Eu6 and [Br]@Eu6 trigonal antiprisms, which are alternately stacked along [001]. Eu2[BN2]I – isotypic to Sr2[BN2]I – crystallizes in the monoclinic space group P21/m (No. 11, Pearson code: mP24; Z = 4; a = 10.2548(6) Å, b = 4.1587(3) Å, c = 13.1234(9) Å, β = 91.215(4)°). The crystal structure is characterized by slightly puckered layers formed by condensed edge sharing I@Eu6 octahedra which are separated by isolated [BN2]3– units. The bond lengths for the strictly linear [BN2]3– anions in (1) and (2) are d(B—N) = 1.351(4) Å and 1.356(8) Å, respectively. In Eu2[BN2]I two crystallograhically distinct [BN2]3– anions are present with d(B1—N) = 1.32(4) Å, 1.37(4) Å and d(B2—N) = 1.30(4) Å, 1.34(4) Å, respectively. Their bond angles vary slightly: ∠(N—B1—N) = 179(3)° and ∠(N—B2—N) = 177(3)°. The magnetic susceptibility data of the europium compounds (2) and (3) indicate that the Eu ions are divalent with 4f7 configuration. Vibrational spectra were measured and interpreted based on the Dh symmetry of the discrete linear [N—B—N]3– moieties, considering the site symmetry reduction and the presence of two distinct [BN2]3– groups in (3).


* Correspondence address: Max Planck Institute for Chemical Physics os Solids, Nöthnitzer Str. 40, 01187 Dresden, Deutschland,

Published Online: 2011-05-03
Published in Print: 2011-08

© by Oldenbourg Wissenschaftsverlag, Dresden, Germany

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