An Iron-Based Dehydration Catalyst for Selective Formation of Styrene

We report the synthesis and crystal structure of [Fe­(OTf)₂(FOX)] (A). This robust iron­(II) complex was successfully applied as a homogeneous catalyst for the dehydration of 1-phenylethanol to styrene. Even at low catalyst loadings and moderate reaction temperatures, A showed a high catalytic efficiency. It was found to selectively activate the benzylic alcohol group of 1-phenylethanol. This is challenging since the vinyl system of styrene is highly reactive. In contrast to most of the other dehydration processes, the use of a Brønsted acid was not necessary. Furthermore, mechanistic insights into this E₁-type transformation and its competing S_N1-type side reactions are reported. [Fe­(^cHexOH)­(OTf)­(FOX)]­[OTf] (B), an alcohol adduct of A, [Fe­(H₂O)₂(FOX)]­[OTf]₂ (C), the completely hydrated derivative of A, and [μ-O­{Fe­(OTf)­(FOX)}₂]­[OTf]₂ (D), a dinuclear oxidation product of A, were also characterized and are discussed.