Journal of the American Chemical Society, Vol.137, No.10, 3478-3481, 2015
Spectroscopic Identification of an Fe-III Center, not Fe-IV, in the Crystalline Sc-O-Fe Adduct Derived from [Fe-IV(O)(TMC)](2+)
The apparent Sc3+ adduct of [Fe-IV(O)(TMC)](2+) (1, TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane) has been synthesized in amounts sufficient to allow its characterization by various spectroscopic techniques. Contrary to the earlier assignment of a +4 oxidation state for the iron center of 1, we establish that 1 has a high-spin iron(III) center based on its Mossbauer and EPR spectra and its quantitative reduction by 1 equiv of ferrocene to [Fe-II(TMC)](2+). Thus, 1 is best described as a Sc-III-O-Fe-III complex, in agreement with previous DFT calculations (Swart, M. Chem. Commun. 2013, 49, 6650.). These results shed light on the interaction of Lewis acids with high-valent metal-oxo species.