These carbonyls
have simple, well defined structures Tetracarbonylnickel(0) is
tetrahedral, pentacarbonyliron(0) is trigonalbipyramidal while
hexacarbonyl chromium(0) is octahedral Decacarbonyldimanganese(0) is made up of two square pyramidal
Mn(CO)5 units joined by a Mn – Mn bond Octacarbonyldicobalt(0)
has a Co – Co bond bridged by two CO groups (Fig