[hz001]

I'm comparing the bonding strengths of C6 rings (benzene, cymene, mesitylene, hexamethylbenzene) to transition metals and trying to find their relative binding strengths... preferably literature on a quantitative analysis, but any quantitative guidance would also be appreciated. If you know of any recent (or not so recent) articles. Any help would be appreciated. Thanks

[Telamond]

Do you know which bonding options transition metals can have with pi-systems? Would the EDG on the benzene increase this strength or weaken it?

One can qualitatively measure the binding force of ligands to transition metal if carbonmonoxide (CO) is bound to the metal as well via IR (if the CO is anti to the pi-binding system).
You can probably intuitively guess why if you draw the MO system.

This has been done with Ru-complexes experimentally (afaik, I'm not interested in any other metals so I haven't checked their possibilities).

[hz001]

thank you for you reply
as electron density in the ring increases the metal-arene binding is expected to increase.
while the trend with benzene, mesitylene and hexamethylbenzene is clear ... not sure about cymene.

[Telamond]

My guess would be the mesitylene. Don't think that the difference in one isopropyl substituent compared to a methyl substituent is that big.

[hz001]

thank you - yes that would be my assumption as well. However, would be more comfortable if I could substantiate with a reference.

[Telamond]

Usually giving a way to find out which is the stronger doner ligand is even better!