IR spectra and point group symmetry

[Bladibla]

Hello

I'm currently studying the reaction of anisole with hexacarbonylchromium, and experiment shows the displacement of 2 of the carbonyl ligands with the anisole group, forming a 2-η ligand with the chromium ion.

After refluxing to obtain the crystals, IR and nmr spectra of the sample were obtained; Apprarently, the point group symmetry of the complex affects the IR spectra of the Cr(CO)4(anisole) compound, but I cannot see how it would affect the IR. Currently, In my IR spectra, I have a distinct peak at 1830 cm-1 corresponding the the CO stretch, and a lesser but nevetheless signficant peak at 1930 cm-1, which I can currently hypothesise is due to the backbonding of electrons to the carbonyl ligands.

Can anyone help with this?

Thanks.

 

[alxm]

I doubt anyone can say offhand. But yeah, probably the C-Cr stretch. Have you compard to the spectrum of pure Cr(CO)6?

 

[quicknote]

Hello,

I can understand your curiosity about the relationship between IR spectra and point group symmetry in the reaction you are studying. Point group symmetry is an important factor to consider in the interpretation of IR spectra. In this case, the point group symmetry of the complex may affect the vibrational modes of the molecule, resulting in changes in the IR spectra.

For example, the presence of a C2 axis of symmetry in the complex may lead to degenerate stretching modes, leading to a splitting or broadening of the CO stretch peak in the IR spectra. This can also explain the appearance of a peak at 1930 cm-1, which may correspond to a different vibrational mode of the CO ligand in the complex.

Furthermore, the presence of a mirror plane of symmetry in the complex may also affect the IR spectra, as it can result in changes in the dipole moment of the molecule and thus, the intensity of certain peaks in the IR spectra.

I suggest looking into the point group symmetry of the complex and comparing it to the expected IR spectra for a molecule with that symmetry. This can help in understanding the observed peaks and their intensities in the IR spectra. Additionally, conducting further experiments with different conditions or varying the point group symmetry of the complex may provide more insights into the relationship between IR spectra and point group symmetry in this reaction.

I hope this helps in your research and understanding of the complex reaction you are studying. Best of luck.