Mixed sodium thio/oxo orthovanadates(V), dark red Na 3 [VS 3 O] and orange red Na 3 [VS 2 O 2 ], were synthesized via reactions in the melt starting from V, Na, Na 2 S, Na 2 O and sulfur. The structure of the low temperature phase of Na 3 [VS 3 O] (space group Pnma, a = 589.5(3), b = 962.8(5), c = 1186.6(6) pm, Z = 4, R1 = 0.0494) contains anions [VS 3 O] 3− almost identical to those known from the high temperature form, β -Na 3 [VS 3 O] (space group Cmc2 1 , a = 968.4(4), b = 1194.6(4), c = 590.5(2) pm, Z = 4, R1 = 0.0291). The second order phase transition between these two forms at 536 °C was studied by temperature dependent powder diffraction and explained on the basis of a comparison of the anion packing in the two related structures. The packing of the dithiodioxovanadate anions in Na 3 [VS 2 O 2 ] (space group Pbca, a = 1162.7(2), b = 592.71(12), c =1766.7(4) pm, Z = 8, R1 = 0.0312) is also closely related. The chemical bonding in the anions [VS 3 O] 3− and [VS 2 O 2 ] 3− of approximately ideal C 3v and C 2v symmetry is discussed on the basis of FP-LAPW band structure calculations and force constants obtained from Raman spectroscopy. The decrease of the calculated band gaps with increasing S content x in Na 3 [VS x O 4−x ] is in accordance with the optical properties showing a gradually deepening of the crystal and solution colour. Discernible trends in the chemical bonding in this series of mixed thio-oxo anions also include the amount of π bonding of the V-O and V-S bonds and the corresponding variation of force constants and V-O/V-S distances.