Is Mn(I) More Promising Than Fe(II)A Comparison of Mn vs Fe Complexes for Olefin Metathesis

Olefin metathesis
is one of the most significant transformations
in organic chemistry and is an excellent example for efficient homogeneous
catalysis. Although most currently used catalysts are primarily based
on 4d and 5d metals, cycloaddition and cycloreversion reactions can
also be attributed to first-row transition metals, such as Fe. Surprisingly,
the potential of Mn(I)-based catalysts for olefin metathesis has been
unexplored despite their prominence in homogeneous catalysis and their
diagonal relationship to Ru(II). In the present study, we have investigated
the prospective capabilities of Mn complexes for cycloaddition and
reversion reactions using density functional theory. Therefore, we
have initially compared the literature known iron model systems and
their isoelectronic Mn counterparts regarding their reactivity and
electronic structure. Next, we constructed potential Mn complexes
derived from synthetically accessible species, including carbonyl
ligands and obeying octahedral geometry. Based on thermodynamic parameters
and the calculation of electronic descriptors, we were able to validate
the isodiagonal relationship. Our study serves as guidance for the
experimental chemist.