Ca2[BN2]H: the first nitridoborate hydride - synthesis, crystal structure, and vibrational spectra

Abstract

Ca2[BN2]H was synthesized from a mixture of the binary components Ca3N2, CaH2 and BN (molar ratio 1 : 1 : 2) in a sealed steel ampoule encapsulated in an evacuated silica tube at 1273 K. Ca2[BN2]H crystallizes in the orthorhombic space group Pnma (no. 62) with a = 9.2015(8)Å, b = 3.6676(2)Å and c = 9.9874(12)Å (Z = 4; Pearson symbol oP24). The crystal structure is a filled variant of the Co2P type and can be formulated as Co2P(□t)3(□py)3 ≡ Ca2[N—B—N]H(□t)2(□py)3 (□t and □py = tetrahedral and square-pyramidal hole, respectively). The d(B—N) bond lengths and bond angle for the linear [N—B—N]3— anion are: d(B—N1) = 1.324(3)Å, d(B—N2) = 1.350(2)Å and ∠N—B—N = 177.2(2)°. The vibrational spectra of Ca2[BN2]H confirm the presence of [N—B—N]3— groups deviating only slightly from the ideal D∞h symmetry. The vibrational frequencies and the ƒ(B—N) force constants are discussed and compared with those of the isotypic compound Ca2[BN2]F.