γ-NiBO was synthesized in a high-pressure/high-temperature experiment at 5 GPa and 900 °C. The single-crystal structure analysis yielded the following results: space group P622 (No. 179), a = 425.6(2), c = 3490.5(2) pm, V = 0.5475(2) nm, Z = 6, and Flack parameter x = -0.010(5). Second harmonic generation measurements confirmed the acentric crystal structure. Furthermore, γ-NiBO was characterized via vibrational as well as single-crystal electronic absorption spectroscopy, magnetic measurements, high-temperature X-ray diffraction, differential scanning calorimetry, and thermogravimetry. Density functional theory-based calculations were performed to facilitate band assignments to vibrational modes and to evaluate the elastic properties and phase stability of γ-NiBO.

We report on the first thoroughly characterized molybdenum borate, which was synthesized in a high-pressure/high-temperature experiment at 12.3 GPa/1300 °C using a Walker-type multianvil apparatus. Mo B O incorporates tetrahedral molybdenum clusters into an anionic borate crystal structure-a structural motif that has never been observed before in the wide field of borate crystal chemistry. The six bonding molecular orbitals of the [Mo ] tetrahedron are completely filled with 12 electrons, which are fully delocalized over the four molybdenum atoms. This finding is in agreement with the results of the magnetic measurements, which confirmed the diamagnetic character of Mo B O . The two four-coordinated boron sites can be differentiated in the B MAS-NMR spectrum because of the strongly different degrees of local distortions. Experimentally obtained IR and Raman bands were assigned to vibrational modes based on DFT calculations.

The high-pressure ammonium triborate HP-(NH 4 )B 3 O 5 was synthesized in a high-pressure/high-temperature experiment at 3 GPa and 600°C. It crystalizes in the monoclinic space group C2/c (No. 15) with the parameters a = 981.0(2), b = 880.2(2), c = 922.2(2) pm, β = 103.8(1)°, V = 0.7735(3) nm 3 , Z = 8, R 1 = 0.0436, and wR 2 = 0.1059 (all data). The compound is built up from ribbons of interconnected corner-and edge-sharing BO 4 tetrahedra that are linked by planar 2753 groups to form a three-dimensional structure. The ammonium ions are situated in channels, forming four hydrogen bonds to oxygen of the boron oxygen network. The structure is a substitutional variant of the compounds HP-MB 3 O 5 , (M = K, Rb) and HP-Cs 1-x (H 3 O) x B 3 O 5 (x = 0.5-0.7). The collected IR and Raman spectra of HP-(NH 4 )B 3 O 5 show great similarities to the spectra of the analogous phases.through single-crystal X-ray diffraction, IR and Raman spectroscopy. Results and Discussion Crystal StructureThe structure of HP-(NH 4 )B 3 O 5 is depicted in Figure 1 exhibiting great similarities to HP-MB 3 O 5 (M = K, Rb) [3,4] and HP-Cs 1-x (H 3 O) x B 3 O 5 (x = 0.5-0.7) [6] due to a similar boron

Abstractα-Y2B4O9 was synthesized in a high-pressure/high-temperature experiment at 12.3 GPa/1020°C. The crystal structure has been determined via single-crystal X-ray diffraction. α-Y2B4O9 is isotypic to the lanthanide borates α-Ln2B4O9 (Ln=Sm–Ho) and crystallizes in the monoclinic space group C2/c (no. 15) with the following lattice parameters: a=25.084(2), b=4.3913(2), c=24.726(2) Å, and β=99.97(1)°. The compound was further characterized via X-ray powder diffraction as well as IR and Raman spectroscopy.

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