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A Dimeric Hydride-Bridged Complex with Geometrically Distinct Iron Centers Giving Rise to an S = 3 Ground State

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journal contribution
posted on 19.07.2019, 19:00 by Anne K. Hickey, Samuel M. Greer, Juan A. Valdez-Moreira, Sean A. Lutz, Maren Pink, Jordan A. DeGayner, T. David Harris, Stephen Hill, Joshua Telser, Jeremy M. Smith
Structural and spectroscopic characterization of the dimeric iron hydride complex [Ph2B­(tBuIm)2FeH]2 reveals an unusual structure in which a tetrahedral iron­(II) site (S = 2) is connected to a square planar iron­(II) site (S = 1) by two bridging hydride ligands. Magnetic susceptibility reveals strong ferromagnetic coupling between iron centers, with a coupling constant of J = +110(12) cm–1, to give an S = 3 ground state. High-frequency and -field electron paramagnetic resonance (HFEPR) spectroscopy confirms this model. A qualitative molecular orbital analysis of the electronic structure, as supported by electronic structure calculations, reveals that the observed spin configuration results from the orthogonal alignment of two geometrically distinct four-coordinate iron fragments held together by highly covalent hydride ligands.