DIIRON AND DICOBALT COMPLEXES OF A PHENOLATE-BRIDGED BINUCLEATING LIGAND WITH MIXED PHENOLATE AND PYRIDINE PODANDS

The ligand 2,6-bis{[(2-hydroxyphenyl)(2-pyridylmethyl)amino]methyl}-4-methylphenol (H3L) was synthesized, and its crystal structure was determined. Crystal data for H3L: triclinic space group P1BAR (No. 2), a = 8.935(3) angstrom, b = 12.376(4) angstrom, c = 13.843(4) angstrom, a = 73.21(2)-degrees, beta = 88.05(2)-degrees, gamma = 81.91(3), V= 1450.7(8) angstrom3, and Z = 2. The structure was refined to R = 0.064 (R(W) = 0.078) for 2117 data with I > 3sigma(I). Reaction of this ligand with CoCl2 and NaO2CCH2CH3 yielded the dicobaltic complex [Co2L(O2CCH2CH3)2]+. A crystal structure determination of the tetraphenylborate salt of this complex reveals that the two cobalt atoms are bridged by the central phenolate group of the ligand and that each cobalt atom is further chelated by three remaining donor sites of the septadentate ligand. The octahedral coordination sphere of each of the cobalt atoms is completed by two bridging propionate ligands. Crystal structure data for [LCo2(OPr)2]BPh4: monoclinic space group C2/c (No. 15), a = 41.123(18) angstrom, b = 11.469(5) angstrom, c = 30.576(14) angstrom, beta = 120.95(3)-degrees, V = 12368(8) angstrom3, and Z = 8. The structure was refined to R = 0.058 (R(w) = 0.069) for 4067 data with I > 3sigma(I). Reaction of the same ligand with FeCl2 or FeCl3 yielded the analogous diferric complex, [Fe2L(O2CCH2CH3)2]+. Oxidation proceeded very rapidly in the case of the iron complex, while the cobalt oxidation occurred much more slowly. A comparison of the structures of the free and coordinated ligand indicates that complexation proceeded with inversion at one of the tertiary amine junctures.