Question

Select the I.U.P.A.C name for $Fe{{(\pi -{{C}_{5}}{{H}_{5}})}_{2}}$:
A. bis(${{\eta }^{6}}$-cyclopentadienyl) iron(II).
B. bis(${{\eta }^{5}}$-cyclopentadienyl) ferrate(II).
C. bis(${{\eta }^{5}}$-cyclopentadienyl) iron(0).
D. bis(${{\eta }^{5}}$-cyclopentadienyl) iron(II).

Answer 1

Hint: Cyclopentadiene is a ligand which is going to donate electrons to different types of metal atoms. One cyclopentadiene is going to act as penta coordinate with the metal atoms. One cyclopentadiene is going to donate one electron to the metal atom.

Complete answer:
- In the question it is asked to write the IUPAC name of the given compound $Fe{{(\pi -{{C}_{5}}{{H}_{5}})}_{2}}$.
- In the given complex the iron is going to act as a cation counterpart while the cyclopentadiene is going to act as anionic counterpart.
- Now we should know the oxidation state of the iron in the given complex to write the IUPAC name of the complex.
- We know that there are two cyclopentadienyl ligands present in the given complex.
- Means two cyclopentadienyl ligands are going to coordinate with one iron atom.
- Therefore, the oxidation of the iron in the given complex will be ‘+2’.
- There are two cyclopentadienyl ligands present, so we must include ‘bis’ in the IUPAC name of the compound.
- Now we can write the IUPAC name for the given complex as bis(${{\eta }^{5}}$-cyclopentadienyl) iron(II).
 - In the above name ${{\eta }^{5}}$ gives the information about the pentavalent coordination of the cyclopentadienyl ligand with the iron atom in the complex.

Note:
If the iron is in the form of a cation then we must write only iron in the IUPAC name. If the iron is in the anionic form, then we must write ferrate in the IUPAC name for the respective coordination complexes.