Isonitrosoacetophenone, synthesized by nitrosotion of acetophenone, has been condensed with diamines (1,4-phenylenediamine, 4,4′-diaminobiphenyl, 4,4′-diaminodiphenylmethane or 4,4′-diaminodiphenylether) to obtain the tetradentate Schiff bases 1,4-phenyliminobis(isonitrosoacetophenone), I,I'-biphenyl-4,4′-diiminobis(isonitrosoacetophenone), 1,1′-diphenylmethane-4,4′-diiminobis(isonitroso-acetophenone) or 1,1′-diphenyloxy-4,4′-diiminobis(isonitrosoacetophenone). The polymeric Ni(II) and Cu(II) complexes of these Schiff bases are square-planar while the polymeric Co(II) complexes are octahedral with water molecules at the axial positions. The structures of the above complexes were determined by 1 H NMR and IR spectroscopy and elemental analyses.