Number of bridging CO ligands in $$[Mn_2(CO)_{10}]$$ is ______

$$[Mn_2(CO)_{10}]$$ is a dinuclear metal carbonyl complex. In this complex, two manganese atoms are bonded together by a direct Mn-Mn single bond.

Each Mn atom is bonded to 5 terminal CO ligands (total 10 CO ligands for the two Mn atoms). The structure has a staggered conformation with no bridging CO ligands.

We can verify this using the 18-electron rule. Mn has 7 valence electrons. Each terminal CO donates 2 electrons, and the Mn-Mn bond contributes 1 electron to each Mn:

$$\text{Electron count per Mn} = 7 + 5(2) + 1 = 18$$

Since each Mn achieves 18 electrons with 5 terminal COs and one Mn-Mn bond, there is no need for bridging CO ligands.

The number of bridging CO ligands in $$[Mn_2(CO)_{10}]$$ is $$\boxed{0}$$.