Li4Ba[BN2]2 – Structure and vibrational spectra

Abstract

The nitridoborate Li4Ba[BN2](2) was synthesized from a 4:1 molar ratio of Li-3[BN](2) and Ba-3[BN2](2) in an arc-welded niobium ampoule at a maximum annealing temperature of 1173 K. The structure was refined from single-crystal X-ray diffractometer data: new type, P (1) over bar, a = 533.9(2), b = 585.0(3), c = 860.6(4) pm, = 80.72(3), = 73.84(6), = 89.87(4)degrees, wR(2) = 0.1196, 1429 F-2 values, 50 variables. The Li4Ba[BN2](2) structure contains two crystallographically independent [BN2](3-) units with 134 pm B-N distance, which are slightly bent: 178 degrees for N2-B1-N1 and 175 degrees for N4-B2-N3. Due to the high lithium content both [BN2](3-) units have a strongly distorted coordination by 8Li(+) + 3Ba(2+). The four crystallographically independent lithium cations show distorted tetrahedral coordination by [BN2](3-) units with Li-N distances ranging from 195 to 247 pm. IR and Raman spectra show the typical vibrations of the [BN2] unit along with a well-resolved splitting of the (B-10) and (B-11) frequencies.