<b>A six-legged piano stool dysprosium single-molecule magnet</b>
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Dysprosium single-molecule magnets (SMMs) with two mutually <i>trans</i>- anionic ligands have shown large crystal field (CF) splitting, giving record effective energy barriers to magnetic reversal (<i>U</i><sub>eff</sub>) and hysteresis temperatures (<i>T</i><sub>H</sub>). However, these complexes tend to be bent, imposing a transverse field that reduces the purity of the <i>m</i><sub><em>J</em></sub> projections of the CF states and promotes magnetic relaxation; a complex with only one anionic ligand could have more pure CF states, and thus high <i>U</i><sub>eff</sub> and <i>T</i><sub>H</sub>. Here we report the first example of an SMM with this topology, [Dy(C<sub>5</sub>Me<sub>5</sub>)(FPh)<sub>6</sub>][{Al[OC(CF<sub>3</sub>)<sub>3</sub>]<sub>3</sub>}<sub>2</sub>(<i>µ</i>-F)]<sub>2</sub> (<b>1-Dy</b>), which exhibits <i>U</i><sub>eff</sub> = 812(47) K and <i>T</i><sub>H</sub> = 14 K at sweep rates of 22 Oe<i> </i>s<sup>–1</sup>; the C<sub>5</sub>Me<sub>5</sub> ligand imposes a strong axial CF and the five equatorially-bound neutral fluorobenzenes present only weak transverse interactions. We show that complexes such as <b>1-Dy</b> can be useful starting materials for heteroleptic Ln complexes as the fluorobenzenes are easily displaced.
