VIBRATIONAL-SPECTRA AND AB-INITIO QUANTUM-MECHANICAL CALCULATION OF ENERGY, GEOMETRY AND VIBRATIONAL FREQUENCIES OF THE OXOTHIOPHOSPHATE IONS PO3S3-, PO2S2(3-) AND POS3(3-)

Water-free samples with the stoichiometries Na3PO3S, Na3PO2S2 and Na3P OS3 have been prepared, and from vibrational spectra the ions PO3S3- a nd PO2S23- have been found. POS33- seems to be unstable towards dispro portionation under these conditions. Some distinct differences are see n between the vibrational spectra of water-free and water-containing s amples. Ab initio calculations (SCF/triple split valence basis, MP2 en ergy) have been used to study the relative stability, geometry and vib rational spectra of the oxothiophosphate anions PO3S3-, PO2S23- and PO S33-. The significant deviations between calculated and experimental g eometry, especially for PO3S3-, are found to be due to the neglect of the counterions. The effect of several counterions is investigated, an d based on these results a corrected resonance hybridization scheme fo r PO3S3- is presented. By scaling the force constants in accordance wi th the observed inaccuracies in the calculated geometry a good fit to experimental frequencies is obtained, and the potential energy distrib ution (PED) is calculated. The scaling for PO3S3- is supported by calc ulation of the influence of one Na+ cation on the vibrational spectra.