text: Salen complexes with d metal ions, such as Ni(salen), typically have a low-spin square planar molecular geometry in the coordination sphere.
  Other metal–salen complexes may have additional ligands above the salen nitrogen–oxygen plane. Complexes with one extra ligand, such as VO(salen), may have a square pyramidal molecular geometry. Complexes with two extra ligands, such as Co(salen)Cl(py), may have octahedral geometry. Usually the MNO core is relatively planar, even though the ethylene backbone is skewed and the overall salen ligand takes a twisted C symmetry. Examples exist where ancillary ligands force the NO donors out of planarity. No evidence indicates that salen is a redox-noninnocent ligand.