In the crystal structure of as-synthesized nonasil, which has orthorhombic symmetry (space group 𝑃𝑐𝑐𝑛), the [Co(cp)2] + cations occupying the large [5 8 ] cages are fully ordered. The fluoride anions are disordered over two sites in adjacent nonasil ] cages, which are fused together via one 4MR. Removal of one F atom per pair of fused cages in an ordered fashion leads to a structure in space group 𝑃𝑐2 1 𝑛, which is visualized in Figure S1. Among different possible arrangements of fluoride anions with respect to each other, this corresponds to one of the arrangements having the highest symmetry (𝑃𝑐2 1 𝑛 being a maximal non-isomorphic subgroup of 𝑃𝑐𝑐𝑛 ).