The geometric constraints imposed by a tetradentate P4N2 ligand play an essential role in stabilizing square planar pyramidal Fe-0(N-2)(P4N2) complex catalyzes the conversion of N-2 highest turnover number of any Fe-based N-2 silylation catalyst to Fe complexes with changes in metal oxidation state. The square to N(SiR3)(3) (R = Me, Et) at room temperature, representing the date (up to 65 equiv N(SiMe3)(3) per Fe center). Elevated N-2 pressures (>1 atm) have a dramatic effect on catalysis, increasing N-2 solubility and the thermodynamic N-2 binding affinity at Fe (N2)(P4N2). A combination of high-pressure electrochemistry and variable-temperature UV-vis spectroscopy were used to obtain thermodynamic measurements of N-2 binding. In addition, X-ray crystallography, Fe-57 Mossbauer spectroscopy, and EPR spectroscopy were used to fully characterize these new compounds. Analysis of Fe-0, Fe-I, and Fe-II complexes reveals that the free energy of N-2 binding across three oxidation states spans more than 37 kcal mol(-1).