Synthesis of Low-Spin Fe(II) NHC Complexes and Their Computational Evaluations in the Context of Olefin Metathesis

The
development of Fe-based olefin metathesis has been a long-standing
goal for several decades. Research from both experimental and theoretical
groups has indicated that suitable Fe alkylidenes should be low-spin
complexes with a high bond dissociation energy (BDE) for the FeC
bond. In this study, we synthesized a series of low-spin Fe complexes
featuring IMes (IMes = 1,3-dimesitylimidazol-2-ylidene), CN, and CO
ligands, which have potential applications in the synthesis of Fe
alkylidenes. We computationally investigated the corresponding Fe
benzylidenes in the context of olefin metathesis. Although some of
these complexes favor low-spin states and demonstrate high BDE, competing
side reactionssuch as cyclopropanation and carbene insertionscould
impede their effectiveness in olefin metathesis.