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

Data for paper published in Angewandte Chemie International Edition (Sept, 2025)

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.

Abstract

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-CpSn)M(h5-Cpttt)]2 (1M; M = Y, Gd, Dy; CpSn = [SnC4-2,5-(SiMe3)2-3,4-Me2]2–, Cpttt = [1,2,4-C5tBu3H2]–), which form by virtue of Sn®M dative bonds. One-electron reduction of 1M with KC8/2.2.2-cryptand produces the mono-anionic complexes [{(h5-CpSn)M(h5-Cpttt)}2]– (2M), and two-electron reduction gives di-anionic [{(h5-CpSn)M(h5-Cpttt)}2]2– (3M) 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 2M are the first tin-radical ligands bound to rare earth elements. Spin density calculations of 2Y and 2Gd reveal significant build-up of unpaired spin on the tin atoms, with magnetic measurements on 2Gd yielding an unprecedentedly large tin-gadolinium exchange coupling constant of –112 cm–1 (–2J formalism).