Synthesis and Crystal Structure of AgTl3(Cr2O7)2

Red single crystals of AgTl3(Cr2O7)2 were prepared via high oxygen pressure synthesis as well as by hydrothermal autoclave techniques. Initially, AgTl3(Cr2O7)2 was obtained from a reaction of stoichiometric mixtures of Ag2O, Cr and TlNO3 under elevated oxygen pressures. Following an optimized approach, the title compound can be synthesized at mild hydrothermal conditions, starting from AgNO3, TlNO3 and K2Cr2O7 in aqueous solution. AgTl3(Cr2O7)2 crystallizes in space group C2/c (no. 15) with a = 10.3638(3), b = 10.4817(3), c = 13.4717(4) Å, β = 106.55(1)◦ , V = 1402.80(5) Å3, and Z = 4. The structure refinement was based on 3554 independent reflections and resulted in R1 = 2.13%, wR2 = 4.54%. The crystal structure contains independent Cr2O72− anions, which are surrounded by silver and thallium cations forming layers that are stacked perpendicular to the bc plane.