Transition metal organometallic complexes are crucial contributors to modern society as catalysts for a myriad of chemical transformations. These span from cross-coupling reactions or polymerization to olefin metathesis, essential processes that have revolutionized our daily lives by providing access to pharmaceuticals, plastics or commodity chemicals. (1) Among the vast domain of molecular catalysts, a notable distinction arises between those formed from 1 st -row transition metals and those featuring a metal from the 2 nd or 3 rd -row. The latter have dominated the catalysis landscape due to their higher activities and controllable behavior associated with well-established two-electron processes in closed-shell systems. In contrast, 1 st -row transition metals tend to operate through less amenable odd electron processes via open-shell electronic configurations. While this introduces complex mechanistic intricacies and undesired sidereactions, it also enables catalytic transformations unavailable for their heavier congeners, thereby significantly expanding the applications of transition metal catalysis. .