[InternationalVelvet]

Hi,

I need help to determine whether or not are CpFe(CO)2X complexes are diamagnetic or paramagnetic. I know that Fe 2+ complexes can be octahedral high spin or low spin and in the case of low spin then are diamagnetic, but as CO is strong field ligand and halogen are low-field ligands, I am confused. Can someone help me to understand?
And what would be th answer in case of CpFe(CO)2Ar where Ar is an aryl?
Thanks for your help.

[vex]

I have seen similar tricarbonyl compounds that are low-spin. CO is a very strong-field ligand, so I would predict both of your complexes to be diamagnets. However, you won't know for sure unless you do another measurement. Something as simple as an NMR can tell you (if you see proton shifts at very high or very low ppm, you're paramagnetic). You might also consider a Guoy technique or EPR if you have access to those.