The oxidation of C-H bonds by Fe(II)-containing active sites has been extensively studied, although few models of Fe(II) in all O-donor environment resembling Zeolite active sites have been reported in the literature, favoring instead N-donor rich ligand environments widely observed in enzymatic systems. The Doerrer group has previously reported the synthesis and characterization of both {K(DME)2}2[Fe(pinF)2] (pinF: perfluoropinacolate) and {K(18C6)}[Fe(OC4F9)3] (OC4F9: perfluoro-tert-butoxide). Here, we report the synthesis of analogs of both complexes with other alkali metal cations varying in size (A: Na, K, Cs) and degrees of encapsulation by ethereal ligands (naked, half or fully encapsulated). The variable temperature reactivity of these complexes with O2, was followed via UV-visible spectroscopy, at temperatures ranging from -80 C to room temperature. This study revealed a difference in the chromophores formed as a function of the nature of the cation and its degree of encapsulation – possibly due to the presence or lack of A---O/F interactions, which are more or less inhibited when the alkali ion is encapsulated. The characterization of isolated oxidized Fe-containing products via UV-vis spectroscopy and single crystal X-ray diffraction will also be discussed. These two systems show that the redox-inert alkali metal cations can exert significant control over the reactivity, which can therefore be used to tune C-H bond oxidation chemistry.

Spectroscopic studies of alkali metal cation control of FeII-fluorinated alkoxide complexes' reduction of O2

ACS Spring Meeting 2021

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