(a) Os₅(CO)₁₈ has a metal framework consisting of three edge-sharing triangles (a raft structure). Show that the valence electron count for this raft is consistent with the number available.

(b) Figure 24.33 shows the metal core of [Ir₈(CO)22]²⁻. What would be an appropriate electron-counting scheme for this cluster?

Figure 24.43.