As you may know many Co(II) compounds easily turn into Co(III).
We had an explanation at the university but it isn't mentioned in
our script and I can't find any source for it on the net.
Our professor said that Co-Complexes would usually have an octahedral
coordination - that's what I would expect from an upper d-Metal, too.
But Co has the anomality to only bind 5 ligands. So you end up with
a pyramide or an octahedron with a flat bottom. If you then have two
of these the remaining place can be used to build a Co-Co bond.
So you end up with something like that:
L5Co-CoL5
This Co-Co bond is quite unstable and falls apart where one Co is oxidized. That's how the fast autooxidation of Co(II) to Co(III) happens.
Now I can't find anything related to that in the literature, does anyone have heard of this before ?
