In Search of Benzene-like Sn₆^6-: Synthesis of Na₄CaSn₆ with Interconnected Cyclohexane-like Sn₆^6-

The title compound was synthesized in an attempt to produce stacked benzene-like Sn66- rings separated by alkaline-earth cations in analogy with the recently reported stacks of aromatic cyclopentadienyl-like Sn56- in Na8BaSn6 (in addition to isolated Sn4- anions). The resulting compound, synthesized from a stoichiometric mixture of the elements at high temperature, has the “correct” stoichiometry with six tin atoms and six positive charges. However, the rings of Sn66- are puckered into chair-type cyclohexanes that are interconnected into isolated cylindrical tubes stuffed with Ca2+ between the rings. Such tubes, if fused to each other, form the hexagonal diamond structure. The new compound is electronically balanced according to magnetic and four-probe resistivity measurements. Reported are also the synthesis and properties of Na10EuSn12 and Na10YbSn12 which are isostructural with the known Na10CaSn12.