Amalgams high coordination number

Tab. 2.4-1. Summary of alkali metal (M) amalgams containing anionic" mercury clusters, extended mercury partial structures and/or high coordination number polyhedra.

Fig. 2.4-10. High coordination number (CN) polyhedra around alkali (alkaline earth) atoms in different mercu7 rich amalgams and in BaCdn (a) CN 15 and (b) CN 16 around K in...

Details of Cs3Hg2o, which is a beautiful new example of an amalgam with high coordination number polyhedra, have been published recently. It can be described simply as being built up by linked octa-capped icosahedra of mercury or as a framework structure related to the clathrate-I type [6]. 

In mercury rich alloys such as M Hg12 (M = K, Rb), a particular situation occurs due to high coordination number (CN) polyhedra (up to CN 22) in their structures. In these compounds the electropositive atoms are located in the centers of these polyhedra and are thus spatially separated from each other. The covalent Hg-Hg interaction, as discussed above, is of minor importance in these amalgams. 

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