 Solution

Each trisilanol cage loses its three hydroxyl protons and supplies a facial tridentate silanolate ligand of charge $3-$. Two such coordination ligands replace all six chlorides of tungsten(VI), givingwith approximately octahedral $\mathrm{W}{\mathrm{O}}_6$ coordination. tungsten remains $+6$, is $d^0$, and is bound to six oxygen donors, three from each cage. The six liberated protons combine with the six chlorides to give six HCl; no W=O bond or tungsten reduction is needed. The molecular formula is ${\mathrm{C}}_{84}{\mathrm{H}}_{154}\mathrm{S}{\mathrm{i}}_{14}{\mathrm{O}}_{24}\mathrm{W}$. This bis(cage) tungsten structure was directly prepared and characterized in the primary literature.^[ref]