Reductive Trapping of [(OC)5W–W(CO)5]2− in a Mixed‐Valent SmII/III Calix[4]pyrrolide Sandwich

Reduction of tungsten hexacarbonyl by the divalent samarium(II) complex [Sm2(N4Et8)(thf)4] ((N4Et8)4−=meso‐octaethylcalix[4]pyrrolide) in toluene at ambient temperature gave the remarkable heteronuclear mixed‐valent samarium(II/III)/tungsten complex [{(thf)2SmII(N4Et8)SmIII(thf)}2{(μ‐OC)2W2(CO)8}], which features the trapping of a rare [W2(CO)10]2− anion with an unsupported W−W bond. Rare mixed‐valent SmII/III and EuII/III calix[4]pyrrolide complexes were synthesized in good and repeatable yield by oxidation of relevant divalent metal precursors. One synthesis involves trapping an extremely rare anionic ditungsten decacarbonyl [W2(CO)10]2− unit with an unsupported W−W bond, achieved through a reductive coupling induced by the divalent samarium calix[4]pyrrolide complex.