Crystal chemistry of compounds containing mercury in low oxidation states

Published data are surveyed and a comparative crystal-chemical analysis is given for the structures of compounds containing mercury in low oxidation s tates as cluster Hg-n groups with covalent Hg-Hg bonds. The geometry of com pounds with Hg - Hg and Hg - X bonds (X = O, S, Se, N, Hal) is analysed and the types of coordination of mercury ions, the packing modes and the relat ionship between structural units are described. Crystallographic and crysta l-chemical data for compounds are given.