In recent years, several catalytic transformations involving Mn(I) complexes have been reported to exhibit similar structure, reactivity and stability as compared to established Ru(II) and Fe(II) systems. Alike the similar chemical properties between elements of the second and third period, it can be assumed that Ru(II) and isoelectronic Mn(I) comprise a diagonal relationship in the periodic table. This relationship is strongly inspired by the successful application of vanadium alkylidenes in OM, mimicking the reactivity of related Mo complexes. Unfortunately, the total number of currently known and stable manganese carbene complexes is small and mostly comprised of Fischer-type complexes. In contrast to Mo and Ru based catalysts, these compounds readily undergo cyclopropanation reactions. Fischer-type carbenes are defined as M=CRX with X being a hetero atom and are thus electrophilic by nature, in contrast to Schrock-type carbenes (M=CR 2 ). The only Mn system that resembles elements of OM was reported by Braunschweig and coworkers in 2013 and involves the formation of [MnCp(CO) 2 (=CPh 2 )] via cycloreversion of a Mn borylene metallacycle. Consequently, manganese catalyzed olefin metathesis has (in contrast to iron) neither been theoretically studied nor experimentally attempted before.