Comparison of isoelectronic Fe and Mn systems In pursuit of an in silico operational manganese system for olefin metathesis, we developed a series of suitable model complexes that allow for a comparison with already known and investigated systems regarding spin state splittings, electronic structure and thermodynamic parameters. For a direct comparison with a literature known Fe system, we first adopted the simple model catalyst 1-Fe reported by Mauksch and Tsogoeva 22 and substituted the putative Fe(II) center with formally isoelectronic Mn(I). The main focus of this 2017 publication was to demonstrate the possibility of low-valent iron for OM based on orbital symmetry and aromaticity arguments.