A structural analysis of {M 4 O 4 } cubanes where M = Mn and Fe

The structures of the M4O4 units found in manganese and iron cubanes are analysed. The model used is that established previously for cobalt and nickel cubanes based on a distortion of the cube by compression of the oxygen atoms along a body diagonal. Further distortion which maintains a S4 or, less frequently, a C3 axis is generally seen. In spite of the distortion, average M-M distances in a cubane are quite constant for a given oxidation state and generally decrease as the metal is oxidised. The angles at the oxygen atoms increase from 90 degrees for the ideal cube to around 97 degrees . For metal oxidation states above or equal to +iii micro3-hydroxo ligands transform to micro3-oxo ligands. Ligands such as carboxylates which can bridge diagonal faces of the cube are generally seen with higher oxidation states.