Counterintuitive charge distribution in Ba8Si6Sn - A new tetralide Zintl phase containing Si36--units

The mixed tetrel Zintl phase Ba8Si6Sn consists of two different blocks of the composition Ba2Sn and Ba6(Si36-)2, respectively. The Si36--units are isolated three membered rings. The triangles are best described as pseudo-sulfur units with two single bonds per atom according to the Zintl-Klemm concept. The tin atoms are isolated and have a formal charge of 4−.