Chelate complexes of some NNO tridentate Schiff bases with iron(II), cobalt(II), nickel(II) and copper(II)

Summary The Schiff bases a-(C₅H₄N)CMe=NNHCOR (R = Ph, 2-thienyl or Me), prepared by condensation of 2-acetylpyridine with the acylhydrazines RCONHNH₂, coordinate in the deprotonated iminol form to yield the octahedral complexes, MNNO]₂ M = Co or Ni; NNOH] = Schiff base and the square-planar complexes, PdNNO]Cl. The Schiff bases also coordinate in the neutral keto form yielding the octahedral complexes (MNNOH]2)Z2 (M = Ni, Co or Fe; Z = C104, BF₄ or N03) and complexes of the type MNNOH]X2 (M = Ni, Co, Fe or Cu; X = Cl, Br or NCS). Spectral and x-ray diffraction data indicate that the complexes MNNOH]X2 (M = Ni or Fe) are polymeric octahedral, as are the corresponding cobalt complexes having R = 2-thienyl. However, the cobalt complexes CoNNOH]X2 (X = CI or Br; R = Ph or Me) and the copper complexes CuNNOH]CI₂ (R = Ph, 2-thienyl or Me) are five-coordinate, while the thiocyanato complex CoNNOH](NCS)₂ (R = 2-thienyl) is tetrahedral.