Unsymmetrische BN2 3--Ionen in den Strukturen von Ca2ClBN2 und Sr2ClBN2 / Unsymmetric BN2 3--Ions in the Structures of Ca2ClBN2 and Sr2ClBN2

Abstract

Abstract The new compounds Ca2ClBN2 (1) and Sr2ClBN2 (2) were prepared from the respective metal, its dihalide and h-BN in sealed tantalum ampoules at 1200 °C. The crystals obtained were transparent yellow (1) and blue (2), respectively. The crystal structures were determined from single crystal X-ray data. Ca2ClBN2 and Sr2ClBN2 are isotypic and crystallize in the orthorhombic space group Pnma (No. 62), Z = 4 (Ca2ClBN 2: a = 1166.7(2), b = 390.26(4), c = 899.8(1) pm, R1 = 0.043, wR2 = 0.115 for 554 independent reflections; Sr2ClBN2: a = 1242.8(1), b = 416.75(4), c = 920.8(1) pm, R1 = 0.031, wR2 = 0.054 for 662 independent reflections). The structures contain two different layers of M2+, Cl- and BN2 3- alternating along the [010] direction. The bond angles N-B-N are 177.2(4)° for (1) and 176,6(5)° for (2), the bond distances of the BN2 3- ions are dB_ N1] = 134.6(5) pm for (1), 136,3(7) pm for (2) and dB_N2 = 132.4(5) pm for (1) and 131,3(7) pm for (2). The unsymmetric structure of the BN2 3- ion, as is manifested particularly in the Sr compound (2), is caused by the coordination of N1 to four cations while N2 is coordinated only to three.