  We analyze the metallic (pi,0) antiferromagnetic state of a five-orbital
model for iron superconductors. We find that with increasing interactions the
system does not evolve trivially from the pure itinerant to the pure localized
regime. Instead we find a region with a strong orbital differentiation between
xy and yz, which are half-filled gapped states at the Fermi level, and
itinerant zx, 3z^2-r^2 and x^2-y^2. We argue that orbital ordering between yz
and zx orbitals arises as a consequence of the interplay of the exchange energy
in the antiferromagnetic x direction and the kinetic energy gained by the
itinerant orbitals along the ferromagnetic y direction with an overall
dominance of the kinetic energy gain. We indicate that iron superconductors are
close to the boundary between the itinerant and the orbital differentiated
regimes and that it could be possible to cross this boundary with doping.
