The mechanism through which nitrogenase enzymes convert dinitrogen into ammonia is a mystery that has been under active investigation for many years. Crystallographic studies have revealed that six high-spin iron atoms in the active-site cluster (the "iron-molybdenum cofactor" shown below) have an unusual coordination environment, with three strong sulfide donors and one weak interaction with an interstitial atom. Based on the hypothesis that this weak interaction is disrupted during the catalytic cycle, we have studied three- and four-coordinate, high-spin iron complexes with an intent of outlining the potential reaction pathways for iron atoms like those in the iron-molybdenum cofactor. Recent research has shown that some of these well-characterized complexes (a) reduce the dinitrogen molecule by two electrons, (b) cooperatively react with hydrazines to break the N-N bond, and (c) break N=N double bonds.