There are a very large number of metal carbonyl clusters of the d-block metals. The bonding and shape for the small metal clusters may be explained by considering the 18e electron rule and the formation of M-M bonds to conform to this rule. The shape of larger clusters though cannot be easily assigned in this method. There is though a semiempirical description of the shape and structure of these clusters. The Table below illustrated the shapes of metal carbonyl clusters related to their cluster valance electron count. This approach is known as Wade-Mingos-Lauher rules and more information is found by reading the paper by them in J. Am. Chem. Soc., 100, 5305, 1978.
| Number of Metal Atoms | Type | Structure of metal frame | Cluster valence electron count |
Example: |
|---|
| 1 | Single metal | • | 18 | Ni(CO)4 |
|---|---|---|---|---|
| 2 | Linear |  |
34 | Mn2(CO)10 |
| 3 | Closed triangle |  |
48 | Co3(CO)9CH |
| 4 | Tetrahedron |  |
60 | Co4(CO)12 |
| Butterfly |  |
62 | [Fe4(CO)12C]2- | |
| Square |  |
64 | Pt4(O2CCH3)8 | |
| 5 | Trigonal bipyramid |  |
72 | Os5(CO)16 |
| Square pyramid |  |
74 | Fe5C(CO)15 | |
| 6 | Octahedron |  |
86 | Ru6C(CO)17 |
| Trigonal prism |  |
90 | [Rh6C(CO)15]2- |
Other molecules of the month compounds