Optical Isomerism of [Fe(H2O)6] Complex

In summary, [Fe(H2O)6] complex exhibits optical isomerism due to the presence of six water molecules surrounding the central iron atom. The two possible isomers, cis-[Fe(H2O)4(OH)2] and trans-[Fe(H2O)4(OH)2], differ in the arrangement of the water molecules around the iron atom, leading to different optical properties. This phenomenon is commonly observed in coordination complexes and has important implications in fields such as bioinorganic chemistry and materials science.
  • #1
broegger
257
0
Hi. I'm asked the following question:

What isomers does the complex [tex][\text{Fe}(\text{H}_2\text{O})_6][/tex] give rise to? Is it optically active?

My answer to the first question would be 'none': The 6 identical H2O molecules are arranged in an octahedral fashion around the central Fe-atom, so there are no asymmetries that could give rise to isomers. Is this correct? It seems to me that this question is phrased as if some isomers do exist (I'm not asked whether they exist or not).

The answer to the second question would of course be 'no', since there are also no optical isomerism.

Am I missing something?
 
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  • #2
Your argument is insufficient. You could use essentially use the same argument to "prove" the optical inactivity of [Co(en)_3]^3+, but that would be wrong...wouldn't it?

While I'd still be inclined to agree with your result, I have never happened upon the bonding/geometry of aquo complexes myself, to say anything definitive. If there is some kind of hydrogen bonding between neighboring H2O ligands (which I think is unlikely), that might induce optical activity.
 
  • #3
I see your point. If we assume that every H2O molecule occupies one ligand space and does not interact with it's neighbors -- would I then be correct? It's an introductory course, so I assume there's no pitfalls.
 
  • #4
broegger said:
I see your point. If we assume that every H2O molecule occupies one ligand space and does not interact with it's neighbors -- would I then be correct? It's an introductory course, so I assume there's no pitfalls.
I'm inclined to say yes, but I'd rather someone who's formally trained in this area weigh in. There may just happen to be some standard result (or exception to the rule) which is completely unobvious to deduce.

Do you have a link to a website talking about bonding/geometry in hexaquo complexes?
 
  • #5
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1. What is optical isomerism?

Optical isomerism is a phenomenon in which molecules have the same chemical formula and bonding structure, but differ in the arrangement of their atoms in space. This results in two or more versions of the molecule that are non-superimposable mirror images of each other, known as enantiomers.

2. How does optical isomerism occur in the [Fe(H2O)6] complex?

The [Fe(H2O)6] complex contains an iron atom bonded to six water molecules. Due to the presence of a chiral center (the iron atom), two enantiomers of this complex can form. These enantiomers differ in the spatial arrangement of the water molecules around the iron atom, resulting in optical isomerism.

3. What is the significance of optical isomerism in the [Fe(H2O)6] complex?

Optical isomerism in the [Fe(H2O)6] complex has important implications in fields such as biochemistry, material science, and pharmacology. It can affect the physical and chemical properties of the complex, as well as its biological activity and reactivity.

4. How can optical isomers of the [Fe(H2O)6] complex be distinguished?

The two enantiomers of the [Fe(H2O)6] complex can be distinguished using techniques such as polarimetry, which measures the rotation of plane-polarized light by the different enantiomers. Additionally, they may have different melting points, boiling points, and solubility properties.

5. Is the [Fe(H2O)6] complex optically active?

Yes, the [Fe(H2O)6] complex is optically active due to the presence of enantiomers. This means that it is capable of rotating the plane of polarized light, with the amount of rotation depending on the concentration of the two enantiomers present. The optical activity of the complex is also temperature and solvent-dependent.

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