L.U.P.A.C. name for complex $\left[\mathrm{Mn}\left(\mathrm{\pi }-{\mathrm{C}}_5{\mathrm{H}}_5\right)(\mathrm{CO}{)}_3\right]$

I.U.P.A.C name for [Mn(π−C_​5H₅​)(CO)₃​]is 

Tricarbonyl (η5-cyclopentadienyl)manganese(I)

In this complex CO is a neutral ligand so it will named first followed by C_5​H_5​ but as it is a π bonded ligand and has five carbons so it is named as η5-cyclopentadienyl. C_5​H_5​ has +1 charge so overall charge and oxidation state of manganese will be +1. 

Thus, the complex is named as  Tricarbonyl (η5-cyclopentadienyl)manganese(I)