The reaction of SO3 with either the palladium chlorides M2PdCl6 (M = Rb, NH4) or the nitrato-palladate (NO)2[Pd(NO3)4] at elevated temperature led to yellow single crystals of the complex palladates M2[Pd(S4O13)2] (M = NH4: triclinic, P1̅, a = 7.3882(3) Å, b = 8.5223(3) Å, c = 9.2712(4) Å, α = 71.945(2)°, β = 88.910(2)°, γ = 72.603(2)°, V = 527.88(4) Å3; M = NO: triclinic, P1̅, a = 7.2881(3) Å, b = 8.9125(2) Å, c = 8.9220(4) Å, α = 75.546(2)°, β = 89.151(2)°, γ = 69.516(2)°, V = 524.02(4) Å3; M = Rb: triclinic, P1̅, a = 7.4468(4) Å, b = 8.5066(4) Å, c = 9.2477(4) Å, α = 72.321(2)°, β = 88.512(2)°, γ = 72.128(2)°, V = 529.75(4) Å3). In the isotypic compounds, the Pd atom is in square planar oxygen coordination, achieved by two bidentate-chelating tetrasulfate anions. The reaction of Na2PdCl6 with neat SO3 afforded yellow crystals of Na2Pd(S4O13)2 (monoclinic, P21/c, a = 6.9953(4) Å, b = 15.9420(9) Å, c = 9.2299(5) Å, β = 100.235(2)°, V = 1012.45(1) Å3). The structure exhibits no palladate complexes but an anionic two-dimensional network, according to ∞2[Pd(S4O13)(4/2)]2–. The latter shows the tetrasulfate anions acting as bidentate-bridging ligands. The tetrasulfato-palladates were studied in more detail by means of thermal analyses and infrared (IR) spectroscopy. The observed IR bands were assigned according to quantum chemical calculations performed on the anion [Pd(S4O13)2]2–.