I. INTRODUCTION 2 Iron pnictides 1 represent a challenge in the field of superconductivity, both from the experimental and theoretical point of view $^{2,3}$. They are magnetic metals that upon electron ( e ) or hole ( h ) doping transform into high temperature superconductors. The prototype of this new family of superconductors is LaOFeAs $^{1}$, which superconducts at 26K upon partial substitution ( ≈ 14%) of O with F. Several other superconducting pnictides have since been discovered, with a record critical temperature up to T$_{c}$ ≈ 55 K $^{4}$. The parent undoped compound for these superconductors are anti-ferromagnetic (AFM) semi-metals, with several competing magnetic structures lying within a few tens of a meV $^{5–12}$. This is an ideal situation for the presence of magnetic instabilities, with a strong possibility of spin fluctuations playing an important role. In fact this is confirmed by experiments, which show that the suppression of the magnetic instability is a necessary step to obtain superconductivity $^{13,14}$. This proximity to an AFM instability leads one to draw parallels between pnictides and cuprates. Despite several similarities these two families of superconductors show important differences. One of the most important differences is related to electronic correlations; cuprates are well known to be strongly correlated materials, where a treatment of on site Coulomb interactions is essential to get the correct normal ground state. On the other hand in the case of pnictides it was concluded by Anisimov et al. 15 that the electronic structure of these materials is consistent with a small value of U (within LSDA+ U scheme) indicating that strong correlations may not be essential to describe them. In fact, unlike in cuprates, standard local/semi local functionals within density functional theory (DFT) can describe the occurrence of magnetism in pnictides, although the agreement between the calculated and the experimental magnetic moment and its dependence upon the choice of functional and atomic positions has been extensively discussed $^{2,6}$. There is not a general consensus about the mechanism leading to superconductivity in these materials. It seems clear, however, that the electron-phonon interaction alone (without involvement of spins) is too weak 16 to produce such a high T$_{c}$ , at least within the standard Migdal-Eliashberg theory. On the other hand explicit involvement of the spin degree of freedom leads to an enhancement of electron-phonon coupling $^{17,18}$; therefore the role of phonons has not been completely ruled out. However, the presence of a weak electron phonon coupling at least in the classic sense