The Indide-Hydride Ba-9[In](4)[H]: Synthesis, Crystal Structure, NMR Spectroscopy, Chemical Bonding

The new indide hydride Ba-9[In](4)[H'] was synthesized from the elements in stoichiometric proportions using the inherent hydrogen content of commercial elemental barium as hydrogen source. Its structure, constituting a new type, was determined using single-crystal Xray data (tetragonal, space group I4/m, a = 1397.3(2), c = 591.8(1) pm, Z = 2) in sufficient quality (R1 = 0.0261) to allow identification and location of the hydride ion as well as the refinement of its thermal parameter. The crystal structure of Ba-9[In]4[H] exhibits isolated indium atoms, which are coordinated by 10 barium cations in a cubicosahedral arrangement. The hydride anions are octahedrally surrounded by six Ba2+ cations. According to [HBa4Ba2/2] these octahedra are connected by opposite corners to form chains running along the c axis. The presence of the hydride ion was determined by solid state NMR spectroscopy, where the chemical shift of the H-1-MAS-NMR signal of -9.0 ppm nicely corresponds to the values in BaH2 and other metallid hydrides. Like in other binary alkaline-earth indides, the band structure calculated in the frame of the FP-LAPW methods shows a pseudo band gap slightly above the Fermi level, associated with the electron precise valence electron count after Zintl (isolated In5-). The title compound was compared to other hydrides and indides both according to the structural as well as the bonding features.