60th Annual Report on Research 2015

Tethered Ligands

We synthesized the complex diiodo-η⁵-[1-(8-quinolyl)-3-methylcyclopentadiene]-cobalt(III) with the idea that a Cp ring less donating than Cp* would facilitate reduction to Co(I).  Current attempts to reduce the complex to ethene-η⁵-[1-(8-quinolyl)-3-methylcyclopentadiene]-cobalt(I) have been unsuccessful.  Zinc amalgam appeared too weak to reduce the complex to cobalt(I), but sodium amalgam may have been too strong.  We are currently pursuing CV studies in order to understand if a metal to ligand charge transfer is operating and if the quinoline ring is compatible with Co(I).

Scheme 1.  New tethered ligand.

CH Activation.

We began a series of studies to understand if Co(I) species could activate CH bonds.  Using the complex Cp*Co(ethene)₂ and both aldimines and ketimines, we identified a stoichiometric reaction leading to what appears to be a ring-bite complex.   Proton NMR studies show evidence for a hydridic or agostic hydrogen at -2ppm, while high resolution LCMS shows a m/z peak consistent with the metallacycle shown in Scheme 2.  We are currently working to isolate and crystallize the product to fully characterize it.

Scheme 2.  Proposed CH activation products