Cylindrical hexameric antimony complexes, one with an enclosed hexaaquanickel(II) ion

The reaction of meso-2,3-dimercaptosuccinic acid and antimony trioxide produces an unusual hexameric cylindrical antimony complex. The cavity is large enough to accommodate the hexaaquanickel(II) cation. The crystal structures of both the parent hexamer and the Ni(II) species enclosed in the hexamer are reported. Bond valence sums were used to confirm that the antimony is +3 in both species and that the Ni ions are all +2 in the encapsulated complex.