Invited
Alkene hydrofunctionalization via multifaceted redox non-innocence

Metal-ligand cooperation is an important aspect of catalysis with first-row transition metals. Utilizing ligands as electron reservoirs to supplement the redox-chemistry of the metal has resulted in many new exciting discoveries. Here we present a rare series of first-row transition metal complexes; [M(BDI)(OTf)x]n (2a: M = Fe and 2b: M = Co, x = 0-2, n = +1 - −1) that are capable of existing in five unique oxidation states. Crystallographic and spectroscopic (e.g. Mössbauer) studies on [Fe(BDI)(OTf)2] indicate that the redox-active ligand (bipyridine-diimine; BDI) unlocks the rich electrochemistry of the metal complex, findings that were also supported by Density Functional Theory (DFT) calculations. By allowing a three-electron ligand-based reduction the bipyridine backbone ultimately and partly dearomatizes, which is electrochemically reversible. In addition to the distinctive redox non-innocence, the activity of 2a and 2b towards alkene hydrofunctionalization was also investigated. While the corresponding iron complex 2a was found to be inactive, the hydrofunctionalization of unactivated alkenes with cobalt complex 2a occurs in exclusive anti-Markovnikov selectivity without any observed dehydrogenation.