Ionothermal Synthesis of Sulfido‐Antimony Dicubanes with 3d‐Metal Spiro‐Atoms

Ternary dicubane cations ( M Sb 6 S 8 ) 4+ with M = Fe, Co, Ni are obtained from the reaction of M Cl 2 with Sb 2 S 3 in the Lewis‐acidic ionic liquid [BMIm]Cl·4.4AlCl 3 at 200 °C (BMIm = butyl‐methyl‐imidazolium). The cationic cluster consists of two cubes that share one vertex, the spiro ‐atom, which is the transition metal M . Counteranions are either [AlCl 4 ] – or [S(AlCl 3 ) 4 ] 2– . The latter complex anion can be described as a supertetrahedron of [AlCl 3 S 1/4 ] tetrahedra that share only one common vertex, which is the central sulfide ion. All three compounds are paramagnetic with effective moments consistent with high‐spin M 2+ cations. Tauc plots reveal optical bandgaps that range between 1.7 and 2.2 eV, assuming direct electron transitions. The present anions induce high sensitivity toward humid air, which leads to rapid decomposition of the compounds into colored oxo‐compounds of the transition metals.