Taming Super-Reduced Bi<sub>2</sub><sup>3–</sup>Radicals with Rare Earth Cations
Peng Zhang, Rizwan Nabi, Jakob K. Staab, Nicholas F. Chilton, Selvan Demir
Abstract
High Resolution Image Download MS PowerPoint Slide 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.