The non-innocence of specific ligands in transition metal complexes is well-documented. For example, mesoionic carbenes engage in bond activation processes via reversible hydrogen capture. Such cooperativity between the metal center and the ligand flattens the potential energy surface of a catalytic reaction and hence rises the competence of the catalyst, thus entailing higher turnover numbers as well as the conversion of more challenging substrates. Likewise, such cooperativity is expected to enhance the catalytic activity of metal centers that are typically not considered to be catalytically very active, such as the ‘rusty’ first row transition metals (Mn, Fe, Ni). Surprisingly, however, this concept has largely been overlooked when designing catalytic transformations based on these earth-abundant and low-cost transition metals. This project will exploit the synergistic potential of mesoionic carbenes as synthetically highly versatile and actively supporting ligands to access a new generation of sustainable high-performance catalysts based on Me, Fe, and Ni for challenging redox transformations such as dehydrogenative oxidations. Specificlly, 1,2,3-triazolylidenes, which support ligand-metal cooperativity through their mesoionic character, will be utilized for (transient) storage/release of protons and electrons. Apart from enabling challenging transformations — with obvious impact on synthetic methodology, energy conversion, and molecular electronics — this project will break into new grounds in catalyst design that will be widely applicable as a new paradigm. Furthermore, this project will capitalize on the unique synthetic versatility of triazolylidene precursors and the opportunity to combine different functional entities such as carbohydrates, surfactants, or dyes with an organometallic entity, thus providing a straightforward approach to new classes of multifunctional materials for application in therapeutics and diagnostics, or as smart surfaces.