Orthorhombic Ba3[BN2]2:: a new structure type for an alkaline earth metal nitrido borate

Yellow, transparent single crystals of Ba-3[BN2](2) (P2(1)2(1)2(1) (No. 19), a = 424.73(2), b = 1105.60(4) and c = 1475.72(6) pm, Z = 4) are obtained by the reaction of Ba2N and BN in arc-welded Nb ampoules at 1300 K. The title compound crystallizes, despite its familiar 3:2:4 stoichiometry, in a new structure type. The vibrational spectra of orthorhombic Ba-3[BN2](2) have been measured and assigned. The IR spectrum reveals strong band splitting arising from the low site symmetry and the presence of two different sets of crystallographically independent [BN2](3-) groups. The new structure and the vibrational data are compared with those previously reported for the cubic form of Ba-3[BN2](2). (C) 2003 Elsevier B.V. All rights reserved.