Superoxo coordination geometries

Two extremes are shown in Figure 4.22 for the interaction of a diatomic molecule A-B with the metal center a linear geometry on the left and a bent geometry on the right. A side-on geometry is omitted for the binding of O2 to a Co" or Fe" porphyrin, since this would lead to either an M side-on superoxo or an M peroxo species both these modes of coordination to these metals are currently without precedent. 

---