INFLUENCE OF CONJUGATED NITROGENOUS BASES ON THE SPECTRA AND STRUCTURE OF MIXED-LIGAND NICKEL(II) CHELATES CONTAINING BETA-DIONES

The infrared and electronic excitation spectra of a series of new nick el(II) chelates containing an alpha-diimine (or nitrogenous base, enR) and the anion of a beta-dione (1,3-ketoenol or 1,3-ketoester, beta H) were obtained in the solid state and in solution. The composition and the overall structure of the new chelates in the solid state depends on ligand concentration, the substituents within the beta-dionato moie ty and the counterion present. The IR and electronic excitation spectr a of [Ni(enR)(2) beta]NO3 and [Ni(enR)beta(O2NO)] indicate, in conjunc tion with other physicochemical measurements, bidentate coordination o f the ligands, while the spectral shifts reveal replacement of the (O, O')nitrato group by basic solvents. The existence of the nickel(II) in an octahedral environment is confirmed by an X-ray structure analysis of [Ni(dpamH)(2)acac]NO3 . CH3OH (monoclinic, space group P2(1)/n, a = 17.296(1), b = 7.462(1), c = 21.604(3) Angstrom, beta = 95.65(1)degr ees, Z = 4, R = 0.0534, Rw = 0.0600), where dpamH denotes the 2,2'-dip yridylamine.