Which of the following homoleptic carbonyl complexes is expected to be the most reactive?

The most reactive homoleptic carbonyl complex among the options is Fe(CO)5. This can be understood by analyzing the properties of the metal-ligand bonding and electron configuration.

Fe(CO)5 features iron in a +0 oxidation state, allowing it to maintain a relatively high reactivity compared to the other complexes. The presence of five carbonyl (CO) ligands provides a pentacoordinate geometry that can facilitate a wide range of coordination and reactivity patterns. The CO ligands are strong field ligands that create a stable but not overly stabilized complex, allowing for potential reactivity with other substrates.

Additionally, iron's ability to participate in various oxidation states, along with its d-electron configuration, means that it can engage in oxidation-reduction reactions more readily. Consequently, this enhances its reactivity compared to the other carbonyl complexes listed, which are either more stable or present at different oxidation states that do not favor high reactivity.

In summary, the structural and electronic features of Fe(CO)5 contribute to its status as the most reactive homoleptic carbonyl complex in the given set.