Synthesis of heteroatomic Zintl anions in liquid ammonia - the new highly charged [Sn4Bi4]4− and fully ordered [Sn2Bi2]2−Electronic supplementary information (ESI) available. See DOI: 10.1039/c2cc35380f

The new Zintl anion [Sn 4 Bi 4 ] 4− , synthesized by dissolving CsSnBi in liquid ammonia, forms a monocapped nortricyclane-like cage. Its electron localization function (ELF) analysis shows evidence for 3-centre bonding. The analogous reaction with KSnBi results in a crystallographically fully ordered tetrahedral [Sn 2 Bi 2 ] 2− ion. While the tetrahedral cluster [Sn 2 Bi 2 ] 2− may be easily understood as a Zintl ion that is isoelectronic to P 4 , the bonding situation in the new cluster [Sn 4 Bi 4 ] 4− presents a puzzle.