Two new Schiff bases containing olefinic linkages have been synthesized by condensing aliphatic diamines with dicinnamoylmethane under specified conditions. The existence of these compounds predominantly in the intramolecularly hydrogen bonded keto-enamine form was well demonstrated by their IR, 1 H-NMR and mass spectral data. Dibasic tetradentate N 2 O 2 coordination of the compounds in their [ML] complexes (M = Ni(II), Cu(II) and Zn(II)) was established on the basis of analytical and spectral data.

Phenylazo- and thiazolylazo-2,4-pentanediones on reaction with 2-aminophenol and 2-aminothiophenol yielded a new series of polydentate Schiff?s base ligands. The structure and tautomeric nature of these compounds and their metal complexes were established on the basis of their IR, 1H-NMR and mass spectral data. The spectral and analytical data revealed the condensation of both carbonyl groups of 3-(2-thiazolylazo)- 2,4-pentanedione with 2-aminophenol to form an N2O2 tetradentate ligand. Details on the formation of its [ML] complexes with Ni(II), Cu(II) and Zn(II) and the nature of their bonding are discussed based on analytical, IR, 1H-NMR and mass spectral data.