Transition metal chelates of two ONNNO quinquedentate ligands

Summary The Schiff bases ,-(RCONHN=CMe)₂C₅H₃N (R = Ph or 2-thienyl) have been prepared by the condensation of 2-acetylpyridine with the substituted hydrazines RCONHNH₂. By the loss of two protons from their iminol tautomers, these Schiff bases act as ONNNO quinquedentate ligands, forming the neutral complexes Met(ONNNO) (Met = Co, Ni, Cu, Zn, Cd or Pd). The zinc and cadmium complexes are monomeric and probably five-coordinate. The cobalt, nickel, and copper complexes are six-coordinate, presumably with an oxygen-bridged dimeric or polymeric structure. The structure of the palladium complex is not known.A uranyl complex UO₂(ONNNO) was also obtained. An x-ray structural determination shows that the complex has a pentagonal bipyrimidal structure with the donor atoms of the quinquedentate Schiff base in the equatorial plane.