The first metallasilsesquioxane of a divalent lanthanide, Yb{Cy7Si7O11(OSiMe3)}(THF),1, was synthesized and structurally characterized. The Cy7Si7O11(OSiMe3)(2-)ligands in1bind two Yb(ii) ions in a bridging mode. The dinuclear complex effects the two-electron reduction of azobenzene yielding the Yb(iii) complex [{Yb(Cy7Si7O11(OSiMe3))(THF)(2)}(2)(PhNNPh)],2, and the CO(2)reduction to CO and carbonate.