Question

The Mo–Mo bond order in [(η5-C5H5)Mo(CO)2]2 which obeys the 18-electron rule is \(\underline{\hspace{2cm}}\).

Hint:

The 18-electron rule is important for predicting the stability of metal-ligand complexes, especially for transition metals.

Answer 1

Correct Answer: 3

The 18-electron rule helps predict the stability of transition metal complexes. The Mo–Mo bond order in the given compound can be calculated by determining the electron count on the metal centers.
1. The \( \eta^5 \)-cyclopentadienyl (\( C_5H_5 \)) ligand contributes 5 electrons.
2. Each CO ligand contributes 2 electrons, so two CO ligands contribute \( 2 \times 2 = 4 \) electrons.
Thus, the total electron count on the Mo atom is \( 5 + 4 = 9 \) electrons. For the compound to follow the 18-electron rule, the Mo-Mo bond order will be calculated based on the interaction between the two Mo centers. Since both Mo atoms are coordinated with a total of 18 electrons, the bond order is \( 1 \).