Metal Complexes with Azine Ligands. II. Iron(II), Cobalt(II), and Nickel(II) Complexes with 2-Pyridyl Methyl Ketazine

Iron(II), cobalt(II), and nickel(II) complexes of the new ketazine ligand 2-pyridyl methyl ketazine (PMK) have been synthesized and characterized by analytical, magnetic, spectrophotometric, and X-ray measurements. PMK forms di-nuclear complexes of the formula [M-2(PMK)(2)X-4 with bridged tetrafunctional coordination of each ligand in the trans,trans configuration. These complexes do not undergo a rearrangement into tridentate 1:2 complexes of the type previously reported for 2-pyridine aldazine (PAA) complexes, presumably because the methyl groups block the C=N group to prevent acid hydrolysis. Dq values are reported for the nickel complexes of PMK and PAA. Iron(II) also forms [Fe(PMK)2]I-2. 4H(2)O and nickel(II) forms Ni(PMK)I-2 center dot 2H(2)O, while cobalt(II) forms neither type.