A Crystalline Iron Terminal Methylidene

Iron methylidene
species are alleged intermediates in the Fischer–Tropsch
process and in olefin cyclopropanation, yet iron methylidene complexes
with unambiguously established molecular and electronic structures
remain elusive. In this study, we characterize an iron terminal methylidene
complex by single-crystal X-ray diffractometry (scXRD), CHN combustion
elemental analysis, 1H/13C/31P/1H–13C NMR, and zero-field 57Fe
Mössbauer spectroscopy and study its reactivity. A series of
closely related complexes in different oxidation states were synthesized,
isolated and characterized in order to validate the electronic structure
of the title methylidene complex. The computational analysis substantiates
the proposed Fischer-type electronic description while emphasizing
high FeCH2 bond covalency, considerable double
bond order, and thus, substantial alkylidene character.