Rb2Dy[S2][AsS4]: Synthesis and characterization of a novel lanthanoid thioarsenate(V) containing outer-sphere disulfide dumbbells

Solid-state syntheses with polysulfide fluxes in sealed silica ampoules offer common approaches for the successful preparation of lanthanoid thiophosphates and -arsenates. However, the synthesis of the new dysprosium thioarsenate(V) from Rb 2 S 3 , As 2 S 3 , Dy and S at 823 K illustrates the effect of the ampoule orientation and the melt-surface during the synthesis. crystallizes monoclinically in the centrosymmetric space group P 2 1 / c with a = 1586.12(9) pm, b = 954.08(5) pm, c = 784.37(4) pm and β = 97.165(3)°for Z = 4. Within its crystal structure, two anionic building blocks arise, namely tetrahedral units and disulfide dumbbells . These anions construct the eightfold sulfur coordination sphere around the unique Dy 3 + cations, assembling as face-connected bicapped trigonal prisms to form 1 ∞ { } chains. They propagate along [001] and showcase a disulfide backside and a front of sulfur thorns. Separated by Rb + cations in seven- and tenfold sulfur coordination, which complete the three-dimensional network, they are leaving small empty channels in [001] direction. Single-crystal Raman spectroscopy confirmed the presence of both disulfide dumbbells and tetrahedra.