Reactive metalloradical intermediates have been implicated in both biological and synthetic catalyst systems for small molecule activation processes, including proton reduction and ammonia oxidation. Towards a greater mechanistic understanding of such transformations on well-defined model complexes, this thesis explores relevant H–H and N–N bond-forming reactions mediated by trivalent Fe and Ni species, as well as catalytic N–N bond cleavage mediated by an open-shell VFe bimetallic complex. First, a pair of thiolate-supported, S = ½ iron...