A comprehensive characterization of thiophosgene in the solid state

Thiophosgene is one of the principal C=S building blocks in synthetic chemistry. At room temperature, thiophosgene is a red liquid. While its properties in the liquid and gaseous states are well known, a comprehensive characterization of thiophosgene in its solid state is presented here. Differential scanning calorimetry shows that thiophosgene forms a supercooled melt before rapidly crystallizing. Its melting point is 231.85 K (-41.3 °C). At 80 K, thiophosgene crystallizes in space group P6₃/m [No. 174, a = b = 5.9645 (2), c = 6.2835 (3) Å, V = 193.59 (2) ų]. The molecule shows a distinct rotational disorder: all S and Cl positions are of mixed occupancy and the disorder does not resolve at temperatures as low as 10 K, as was shown by neutron powder diffraction. Infrared, Raman and inelastic neutron scattering spectra were collected and assigned with the aid of quantum chemical calculations. A larger ordered structural model allowed for better agreement between the measured and calculated spectra, further indicating that disorder is an inherent feature of solid-state thiophosgene.