Extended metal atom chains (Emacs) refer a family of molecules that consist of a central metal atoms with metal-metal bonds and four surrounding ligands. My colleague Shie-Min Peng is a pioneer in this field.
The shortest emacs contain three central metal atoms such as triCobalt emacs, [Co3(dipyridylamido)4Cl2]+, as shown in the following figure:
(Dimitrios A. Pantazis, Carlos A. Murillo and John E. McGrady, Dalton Trans., 2008, 608)
Originally, I don't think beads are suitable for making molecular model for this kind of molecules. But Chern Chuang proved that I was wrong. Today, right after I came back to my office, Chern gave me the first bead model of the longest emacs with 11 Nickel atoms that has ever been synthesized.