Taming Super-Reduced Bi 2 3- Radicals with Rare Earth Cations.

Here, we report the synthesis of two new sets of dibismuth-bridged rare earth molecules. The first series contains a bridging diamagnetic Bi anion, (Cp*RE)(μ-η:η-Bi), (where Cp* = pentamethylcyclopentadienyl; RE = Gd (), Tb (), Dy (), Y ()), while the second series comprises the first Bi radical-containing complexes for any d- or f-block metal ions, [K(crypt-222)][(Cp*RE)(μ-η:η-Bi)]·2THF (, RE = Gd (), Tb (), Dy (), Y (); crypt-222 = 2.2.2-cryptand), which were obtained from one-electron reduction of with KC. The Bi radical-bridged terbium and dysprosium congeners, and , are single-molecule magnets with magnetic hysteresis. We investigate the nature of the unprecedented lanthanide-bismuth and bismuth-bismuth bonding and their roles in magnetic communication between paramagnetic metal centers, through single-crystal X-ray diffraction, ultraviolet-visible/near-infrared (UV-vis/NIR) spectroscopy, SQUID magnetometry, DFT and multiconfigurational ab initio calculations. We find a π ground SOMO for Bi, which has isotropic spin-spin exchange coupling with neighboring metal ions of ca. -20 cm; however, the exchange coupling is strongly augmented by orbitally dependent terms in the anisotropic cases of and . As the first examples of p-block radicals beneath the second row bridging any metal ions, these studies have important ramifications for single-molecule magnetism, main group element, rare earth metal, and coordination chemistry at large.