\vbox{ \centerline{\structure{\nopositioncheck \atom{O}\etriple\atom{C}\esingle\firstbicycloatom{Fe} \side{\nwsingle\atom{C}\nwtriple\atom{O}} \side{\swsingle\atom{C}\swtriple\atom{O}} \sesingle\atom{C}\side{\sdouble\atom{O}}\nesingle\phantatom{Fe} \side{\esingle\atom{C}\etriple\atom{O}} \side{\sesingle\atom{C}\setriple\atom{O}} \side{\nesingle\atom{C}\netriple\atom{O}} \nnwsingle\secondbicycloatom{C}\side{\nnedouble\atom{O}} \ssephantom\firstbicycloatom{Fe}\swphantom\phantatom{C} \nwphantom\phantatom{Fe}\nnesingle\secondbicycloatom{C} \side{\nnwdouble\atom{O}}\sswphantom\firstbicycloatom{Fe} \sephantom\phantatom{C}\nephantom\secondbicycloatom{Fe}}} \medskip \centerline{\bf Figure~8. \rm Tri-$\mu$-carbonyl-bis(tricarbonyliron).} }