Data for paper: Benzene Tetra-anion Complexes of Early and Late Rare-Earth Metals

Data for paper published in <i>Journal of the American Chemical Society</i> <i>(March 2025)</i>X-ray crystallography data in .cif format.Checkcif for all compounds.Magnetic measurement data for all compounds.<br><br><b>Abstract</b><br>A novel synthetic route to the triple-decker benzene tetra-anion complexes [(η⁵-C₅^<em>i</em>Pr₅)M(μ:η⁶:η⁶-C₆H₆)M(η⁵-C₅^<em>i</em>Pr₅)] is reported for a range of early and late rare-earth elements, i.e., M = Y, La, Sm, Gd, and Dy (<b>1</b>_{<strong>M</strong>}). The lanthanum complex <b>1</b>_{<strong>La</strong>} is the first benzene tetra-anion complex of the largest rare-earth element. Aromaticity in the 10π-electron benzene ligands is confirmed through crystallographic studies of all compounds and nucleus-independent chemical shift calculations on <b>1</b>_{<strong>Y</strong>} and <b>1</b>_{<strong>La</strong>}. Analysis of the bonding in <b>1</b>_{<strong>Y</strong>} and <b>1</b>_{<strong>La</strong>} using density functional theory revealed strong covalency in the metal-benzene interactions, with very similar contributions from the metal 4d/5d orbitals, respectively, and the benzene π* orbitals. Magnetic susceptibility measurements on <b>1</b>_{<strong>Sm</strong>}, <b>1</b>_{<strong>Gd</strong>}, and <b>1</b>_{<strong>Dy</strong>} are also consistent with the presence of a benzene tetra-anion ligand. The origins of the appreciable exchange coupling constant of <i>J</i>_exch = −3.35 cm^–1 (−2<i>J</i> formalism) in <b>1</b>_{<strong>Gd</strong>} are established through a computational study of the interacting magnetic orbitals. The dynamic magnetic properties of <b>1</b>_{<strong>Dy</strong>} are also described. The clear absence of SMM behavior in the dysprosium complex is explained using multireference calculations and an ab initio ligand-field theory description of the 4f orbitals, which clearly show that the benzene tetra-anion ligand provides a dominant equatorial contribution.