3-Ketoglutarates: Compounds with Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Mg, and Na

Where A designates the dinegative 3-ketoglutarate ion and L indicates a trinegative species (likely the enolate ion), the following compounds have been obtained: Na 2 A, NaCuL.XH 2 O, MgA.XH 2 O, MnA.XH 2 O, CoA.XH 2 O, NiA.XH 2 O. Hydration numbers are uncertain. Stoichiometry of Cu(II) and Zn(II) compounds could not be established. Structures have been assigned on the basis of the infrared spectra. Na 2 A appears to be a simple ionic carboxylate. MgA, MnA, CoA, and NiA are assigned a similar structure, with unidentate carboxylate coordination and hydrogen-bonded coordination between the metal and the second carboxylate oxygen (through water). NaCuL is assigned a metal-bridged polymer structure. There is not significant metal interaction with the carbonyl oxygen in any of the proposed structures.