Potassium, Cesium, and Ammonium Peroxogermanates with Inorganic Hexanuclear Peroxo Bridged Germanium Anion Isolated from Aqueous Solution

Potassium (K6[Ge6(μ-OO)6(μ-O)6(OH)6]·14H2O, 1), cesium ammonium (Cs4.2(NH4)1.8[Ge6(μ-OO)6(μ-O)6(OH)6]·8H2O, 2), and
potassium ammonium (K2.4(NH4)3.6[Ge6(μ-OO)6(μ-O)6(OH)6]·6H2O, 3) peroxogermanates were isolated
from 3% hydrogen peroxide aqueous solutions of the corresponding hydroxogermanates
and characterized by single crystal and powder X-ray diffraction studies
and by Raman spectroscopy and thermal analysis. The crystal structure
of all three compounds consists of cations of potassium and/or ammonium
and cesium, water molecules, and centrosymmetric hexanuclear peroxogermanate
anion [Ge6(μ-OO)6(μ-O)6(OH)6]6– with six μ-oxo- and six
μ-peroxo groups. Peroxogermanates demonstrate relatively high
thermal stability: the peroxide remains in the structure even after
water release after heating to 100–120 °C. DFT calculations
of the peroxogermanate [Ge6(μ-OO)6(μ-O)6(OH)6]6– anion confirm its higher
thermodynamic stability compared to the hydroperoxo- and oxogermanate
analogues.

本研究从相应羟基锗酸盐的3%过氧化氢水溶液中分离得到三种过氧锗酸盐（peroxogermanates）：编号1的K₆[Ge₆(μ-OO)₆(μ-O)₆(OH)₆]·14H₂O（钾盐）、编号2的Cs₄.₂(NH₄)₁.₈[Ge₆(μ-OO)₆(μ-O)₆(OH)₆]·8H₂O（铯铵盐）以及编号3的K₂.₄(NH₄)₃.₆[Ge₆(μ-OO)₆(μ-O)₆(OH)₆]·6H₂O（钾铵盐）。上述化合物通过单晶与粉末X射线衍射（single crystal and powder X-ray diffraction）、拉曼光谱（Raman spectroscopy）以及热分析（thermal analysis）完成表征。
三种化合物的晶体结构均由钾/铵与铯阳离子、水分子，以及带有6个μ-氧桥（μ-oxo-）和6个μ-过氧桥基团（μ-peroxo groups）的中心对称六核过氧锗酸根阴离子[Ge₆(μ-OO)₆(μ-O)₆(OH)₆]⁶⁻构成。该类过氧锗酸盐展现出较高的热稳定性：即便在加热至100~120℃并释放结晶水后，其结构中的过氧基团仍可保留。
针对阴离子[Ge₆(μ-OO)₆(μ-O)₆(OH)₆]⁶⁻的密度泛函理论（DFT）计算结果证实，相较于氢过氧锗酸盐与氧锗酸盐类似物，该阴离子具有更高的热力学稳定性。