On the stability of an unsupported mercury-mercury bond linking group 15 Zintl clusters

The dimeric Zintl ion [Hg ₂(As ₇) ₂] ^4- has been synthesized with high crystalline yield from the reaction of an ethylendiamine solution of the intermetallic Zintl phase K ₃As ₇ with diphenyl mercury. Single crystal X-ray diffraction of [K(2,2,2-crypt)] ₄[Hg ₂As ₁₄], 1 (2,2,2-crypt = 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]-hexacosane), reveals that the cluster anion exhibits a Hg-Hg bond and the compound has been further characterized using Raman spectroscopy, cyclic voltammetry and its band gap energy was measured. Theoretical studies provide a microscopic understanding of the bonding in this unusual compound.