Transition metal complexes of diethyl Cyclopentanone-2,5-diglyoxylate

Diethyl cyclopentanone-2,5-diglyoxylate (ecgH2; IV) forms complexes of the type M(ecg)Bn with divalent transition metals, where M = Mn, Fe, Co, Ni, Cu, Zn; B = H2O or a heterocyclic base, and n = 1 (when M = Cu) or n = 2 (M = others). All complexes have the high-spin configuration. Infrared spectra show the presence of chelate β-diketone rings and free carbonyl groups. Visible and near-infrared spectra support octahedral stereochemistry for the nickel(II) and cobalt(II) complexes. Molecular weights show the complexes to be dimeric. These results are consistent with an oxygen-bridged structure, M2L2B2n, in which base molecules are added above and below a planar M2L2 unit (VI).