Solvothermal synthesis of a bimetallic thiometallate containing germanium in two oxidation states

A new layered germanium–antimony sulphide, [Ge(C2N2H8)3][GeSb2S6], has been prepared at 463 K under solvothermal conditions in the presence of ethylenediamine. The compound has been characterised by single-crystal X-ray diffraction, thermogravimetry, elemental analysis and reflectance spectroscopy. [Ge(C2N2H8)3][GeSb2S6] crystallises in the space group Pbca (a=13.3284(5), b=17.4801(6), c=18.5447(7) Å). The structure consists of cyclic [GeSb2S8]6− units that form chains which are cross-linked through Sb2S2 rings to generate layers of stoichiometry [GeSb2S6]2−, between which [Ge(en)3]2+ cations are located. [Ge(C2N2H8)3][GeSb2S6] contains germanium in both the divalent and tetravalent states. The optical band gap of 2.49(4) eV is in excellent agreement with the value expected on the basis of the correlation with the density of metal centres previously identified for thioantimonates, and is consistent with states at the top of the valence band being predominantly of sulphur 3p character.