The IUPAC name of the complex [(CO)5Mn - Mn(CO)5] is decacarbonyldimanganate(0) [option C].

Explanation:

1. Understanding the complex:
The complex contains two Mn atoms, each coordinated to five CO ligands. The central Mn atom is connected to the other Mn atom through a bridging CO ligand.

2. Identifying the oxidation state:
To determine the oxidation state of the complex, we need to consider the charge on the ligands and the overall charge of the complex. Each CO ligand is considered to be neutral, so the oxidation state of the Mn atoms can be calculated as follows:

For the central Mn atom:
5 CO ligands x 0 charge = 0
1 bridging CO ligand x (-1 charge) = -1

For the other Mn atom:
5 CO ligands x 0 charge = 0

The overall charge of the complex is 0, so the oxidation state of both Mn atoms is 0.

3. Naming the complex:
The IUPAC name of the complex is determined by considering the ligands and the oxidation state of the central metal atom.

In this case, the complex contains two Mn atoms, each coordinated to five CO ligands. The central Mn atom is connected to the other Mn atom through a bridging CO ligand.

The IUPAC name follows the pattern:
[metal name (oxidation state) ligand name]

For the central Mn atom:
Deca- indicates the presence of 10 CO ligands (5 directly bonded and 5 bridging).
Carbonyl- indicates the type of ligand.
Dimanganate(0) indicates the presence of two Mn atoms with an oxidation state of 0.

For the other Mn atom:
Bis- indicates the presence of two Mn atoms.
Pentacarbonyl- indicates the presence of 5 CO ligands.
Dimanganese(0) indicates the presence of two Mn atoms with an oxidation state of 0.

So, the complete IUPAC name of the complex is decacarbonyldimanganate(0).

In summary, the IUPAC name of the complex [(CO)5Mn - Mn(CO)5] is decacarbonyldimanganate(0) [option C]. The name is determined by considering the ligands (CO) and the oxidation state of the central metal atom (Mn).