Note: Crystal Structure, Vibrational Spectrum and Thermal Behavior of the Ammonium Hexathiohypodiphosphate Dihydrate, (NH 4 ) 4 P 2 S 6 · 2H 2 O

Single crystals of (NH 4 ) 4 P 2 S 6 ・ 2H 2 O could be obtained and the crystal structure determined (monoclinic, P2 1 /c with a = 6.931(1), b = 12.730(2), c = 17.446(2) Å , β = 96.87(1)°, V = 1528.2(4) Å 3 , Z = 4). The NH 4 + , and [P 2 S 6 ] 4− ions and the water molecules are involved in an extended hydrogenbonding network. The FT-Raman and FT-IR spectra have been recorded and the observed vibrational frequencies assigned to tetrahedral NH 4 + and [P 2 S 6 ] 4− (D 3d ) ions as well as to H 2 O molecules. The thermogravimetric analysis has shown that (NH 4 ) 4 P 2 S 6 · 2H 2 O starts to decompose at around 60 °C (up to 170 °C), but no distinct intermediates could be observed.