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.