Data for paper: Reduction of Rare-Earth Stannole Sandwich Complexes to Tin-Based Radical Ligands and Tin-Tin Bonds

Data for paper published in<i> Angewandte Chemie International Edition</i> (Sept, 2025)<br>X-ray crystallography data in .cif format.Checkcif files.NMR data in .fid format.Magnetic measurements in spreadsheet format.UV/vis data.FTIR data.EPR data.<br><b>Abstract</b><br><br>f-Element organometallic chemistry is dominated by cyclopentadienyl ligands. In contrast, isoelectronic metallole ligands with the general formula [EC₄R₄]^2–, where E is a heavier group 14 element, are rare in the f-block, particularly stannole ligands. Here, we describe the synthesis of the dimetallic stannole complexes [(h⁵-Cp^Sn)M(h⁵-Cp^ttt)]₂ (<b>1</b>_{<strong>M</strong>}; M = Y, Gd, Dy; Cp^Sn = [SnC₄-2,5-(SiMe₃)₂-3,4-Me₂]^2–, Cp^ttt = [1,2,4-C₅^<em>t</em>Bu₃H₂]^–), which form by virtue of Sn®M dative bonds. One-electron reduction of <b>1</b>_{<strong>M</strong>} with KC₈/2.2.2-cryptand produces the mono-anionic complexes [{(h⁵-Cp^Sn)M(h⁵-Cp^ttt)}₂]^– (<b>2</b>_{<strong>M</strong>}), and two-electron reduction gives di-anionic [{(h⁵-Cp^Sn)M(h⁵-Cp^ttt)}₂]^2– (<b>3</b>_{<strong>M</strong>}) as [K(2.2.2-crypt)]⁺ salts. Studies of the stannole complexes using crystallography, UV/vis and EPR spectroscopy, magnetometry and computational methods reveal that the reduction steps generate tin-tin bonds through population of a delocalized molecular orbital that spans the {M₂Sn₂} rings, with attendant dearomatization of the stannole rings. Complexes <b>2</b>_{<strong>M</strong>} are the first tin-radical ligands bound to rare earth elements. Spin density calculations of <b>2</b>_{<strong>Y</strong>} and <b>2</b>_{<strong>Gd</strong>} reveal significant build-up of unpaired spin on the tin atoms, with magnetic measurements on <b>2</b>_{<strong>Gd</strong>} yielding an unprecedentedly large tin-gadolinium exchange coupling constant of –112 cm^–1 (–2<i>J</i> formalism).<br>