State the $IUPAC$ name of the following complex: $Fe(C_5H_5)_2$.

In $Fe(CO)_5$ and $Cr(CO)_6$,how many $CO$ ligands can be replaced by $NO$ to maintain the $18$ electron rule?

Given below are two statements:
Statement $I$: The $M - C \sigma$ bond is formed by the donation of a lone pair of electrons on the carbonyl carbon into a vacant orbital of the metal.
Statement $II$: The $M - C \pi$ bond is formed by the donation of a pair of electrons from a filled $d$-orbital of the metal into the vacant antibonding $\pi^*$ orbital of carbon monoxide.
In the light of the above statements, choose the correct answer from the options given below:

Which of the following substances is used as an antiknock compound?

The number of bridging $CO$ ligand$(s)$ and $Co-Co$ bond$(s)$ in $Co_2(CO)_8$ respectively are

The molecular formula of Wilkinson catalyst,used in the hydrogenation of alkenes is -