Reductive Trapping of [(OC)5 W-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 (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 SmII (N4 Et8 )SmIII (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.