δ-Bonding modulates the electronic structure of formally divalent nd rare earth arene complexes.

Landmark advances in rare earth (RE) chemistry have shown that divalent complexes can be isolated with non-Aufbau 4f {5d/6s} electron configurations, facilitating remarkable bonding motifs and magnetic properties. We report a series of divalent bis-tethered arene complexes, [RE(NHAr )] (2RE; RE = Sc, Y, La, Sm, Eu, Tm, Yb; NHAr = {N(H)CH-2,6-(CH-2,4,6-Pr)}). Fluid solution EPR spectroscopy gives < 2.