Bidentate and tetradentate ligands derived from pentane-2, 4-dione.

3-Substituted pentsine-2, 4-diones, CH3.CO.CHR.CO.CH3, have been prepared: R = (i) H- (ii) CH3- (iii) C2H5- (iv) n-C3H7- (V) i-C3H7- (Vi) CH2=CH-CH2- (vii) CH3CH2CH=CH- (viii) C2H5O.CO- (ix) Cl- The decomposition of these compounds has been studied in alkaline solution. Derivatives (ii) and (iii) decomposed quantitatively to give ethanoic acid (acetic acid) and the appropriate ketone. Derivative (vii) yielded ethanoic acid and a complex mixture of products. Mass spectrometry indicated the tendency to cleave at the 2, 3, bond, the most abundant species being the acylium ion CH3CO+. NMR studies have investigated the keto-enol tautomerism of the series, as pure liquids and in solution in 50% deuterated dioxan/heavy water. These results compared well with those obtained by a chemical method. Compounds (i), (ii) and (vi) have been condensed with 1, 2- diaminoethane to produce Schiff base-type tetradentate ligands. These keto-imines were found to be weakly acidic, giving pKa around 14 in 50% dioxan. Mass spectra of the keto-imines have shown these ligands to have a common fragmentation pattern consistent with the proposed structure. NMR spectra of the Keto-imines has shown imine-enamine tautomerism for the three ligands, and that the enamine tautomer predominated in CDCl3 to the extent of about 60%. Copper (II) and nickel (II) chelates of the keto-imines have been prepared. Mass spectra of the copper (II) chelates have been compared with ligand spectra to determine the effect of the metal on thermal stability of the ligand.