Carbon monoxide has lone pairs on both the carbon and the oxygen atoms. However, I have never seen any complex where the oxygen atom or both the oxygen and the carbon atoms are the donors.
I know that the much lower electronegativity of carbon makes it a much stronger donor. However, this difference in electronegativity exists in the cyanide ion too, albeit a little less. However, cyanide ion is ambidentate.
My question basically is : Why is carbon monoxide not an ambidentate ligand? Further, why is it not bidentate?