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 2 2- anion, (Cp* 2 RE) 2 (μ-η 2 :η 2 -Bi 2 ), 1-RE (where Cp* = pentamethylcyclopentadienyl; RE = Gd ( 1-Gd ), Tb ( 1-Tb ), Dy ( 1-Dy ), Y ( 1-Y )), while the second series comprises the first Bi 2 3- radical-containing complexes for any d- or f-block metal ions, [K(crypt-222)][(Cp* 2 RE) 2 (μ-η 2 :η 2 -Bi 2 • )]·2THF ( 2-RE , RE = Gd ( 2-Gd ), Tb ( 2-Tb ), Dy ( 2-Dy ), Y ( 2-Y ); crypt-222 = 2.2.2-cryptand), which were obtained from one-electron reduction of 1-RE with KC 8 . The Bi 2 3- radical-bridged terbium and dysprosium congeners, 2-Tb and 2-Dy , 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 z * ground SOMO for Bi 2 3- , which has isotropic spin-spin exchange coupling with neighboring metal ions of ca. -20 cm -1 ; however, the exchange coupling is strongly augmented by orbitally dependent terms in the anisotropic cases of 2-Tb and 2-Dy . 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.