[(ZnSb6)2]4- : a new structure type for coupled norbornadiene-like subunits

The norbornadiene-like bimetallic dimer [(ZnSb6)(2)](4-) anion (1) was prepared by direct extraction from a ternary alloy with nominal composition K6ZnSb5 in ethylenediamine/toluene/2,2,2-crypt solutions. The structure represents a new type for coupled norbornadiene subunits, however, distortions around the Zn2+ ions degrade the overall symmetry. The Zn2+ ions achieve a 16e(-) configuration and reside in near perfect ZnSb3 triangular coordination environments. DFT calculations reveal a 2.35 eV HOMO-LUMO gap and suggest covalent bonding between the Zn and Sb atoms.