1,10-Phenanthroline-5,6-dione complexes of middle transition elements: Mono- and dinuclear derivatives

The synthesis and the characterization of several mono- and dinuclear middle transition metal derivatives of 1,10-phenanthroline-5,6-dione, 1, are presented. The reaction of 1 with CrCl₂(THF)₂ gives CrCl₂(O,O′-C₁₂H₆N₂O₂)(THF)₂, 2, while the halides of iron(II), cobalt(II) and nickel(II) afford adducts of general formula MX₂(N,N′-C₁₂H₆N₂O₂), M = Fe, 4, Co, 5, X = Cl; M = Ni, 6, X = Br. DFT calculations on CrCl₂(L)(THF)₂ with L = O,O′-C₁₂H₆N₂O₂ or O,O′-C₁₄H₈O₂ allowed a direct comparison of the coordination properties of 9,10-phenanthrenequinone and 1,10-phenanthroline-5,6-dione to be made. Dinuclear compounds of general formula CrCl₂(THF)₂(O,O′-C₁₂H₆N₂O₂-N,N′)MX_nL_m, M = Zr, 7, X = Cl, n = 4, m = 0; M = Cr, 8, X = Cl, n = 2, L = THF, m = 2; M = Fe, 9, Co, 10, X = Cl, n = 2, m = 0; M = Ni, 11, X = Br, n = 2, m = 0, are prepared from 2 and the corresponding metal halide, while VCp₂(O,O′-C₁₂H₆N₂O₂-N,N′)FeCl₂, 12, is synthesized by reacting 4 with VCp₂. The electronic properties of the different complexes are investigated by magnetic moment measurements and EPR spectroscopy.