Reductive Trapping of [(OC)₅ W-W(CO)₅ ]^2- in a Mixed-Valent Sm^II/III Calix[4]pyrrolide Sandwich

Reduction of tungsten hexacarbonyl by the divalent samarium(II) complex [Sm₂ (N₄ Et₈ )(thf)₄ ] ((N₄ Et₈ )^4- =meso-octaethylcalix[4]pyrrolide) in toluene at ambient temperature gave the remarkable heteronuclear mixed-valent samarium(II/III)/tungsten complex [{(thf)₂ Sm^II (N₄ Et₈ )Sm^III (thf)}₂ {(μ-OC)₂ W₂ (CO)₈ }], which features the trapping of a rare [W₂ (CO)₁₀ ]^2- anion with an unsupported W-W bond.