The sum of bridging carbonyls in W(CO)$$_6$$ and Mn$$_2$$(CO)$$_{10}$$ is ______.

We need to find the sum of bridging carbonyls in W(CO)₆ and Mn₂(CO)₁₀.

W(CO)₆: Tungsten hexacarbonyl is a mononuclear complex with octahedral geometry. All 6 CO ligands are terminal (bonded only to W). There are 0 bridging COs.

Mn₂(CO)₁₀: Dimanganese decacarbonyl has two Mn atoms connected by a direct Mn-Mn bond. Each Mn has 5 terminal CO ligands in a staggered arrangement. There are 0 bridging COs. (This is different from Co₂(CO)₈ which has 2 bridging COs in one of its structures.)

Sum of bridging carbonyls = $$0 + 0 = 0$$.

The answer is $$\boxed{0}$$.