The molecular formula of dodecacarbonyltrimanganese(0)

The correct answer is Option (2) → \([Mn_3(CO)_{12}]\)

The name of a metal carbonyl gives its formula directly. The numerical prefix before “carbonyl” gives the number of CO ligands, the prefix before the metal gives the number of metal atoms, and the Roman numeral gives the oxidation state of the metal. CO is a neutral ligand, so a carbonyl with no other ligand has the metal in the zero oxidation state.

• dodecacarbonyl = 12 CO ligands

• trimanganese = 3 Mn atoms

• (0) = Mn in the zero oxidation state; 12 neutral CO ligands keep the complex neutral.

So the formula is [Mn₃(CO)₁₂].