Ionic Association of Mixed Nickel(II) Chelates in Alcohols, Ketones, and Nitrobenzene

Abstract

Abstract The conductances of mixed nickel(II) chelates, [Ni(acac)(N,N,N′,N′-tmen)]X (where acac=2,4-pentanedionato, N,N,N′,N′-tmen=N,N,N′,N′-tetramethylethylenediamine, and X−=ClO4− or NO3−), in alcohols {ethanol (EtOH), 1-propanol (n-PrOH), 2-propanol (i-PrOH), and 1-butanol (n-BuOH)}, ketones {acetone (Me2CO), methyl ethyl ketone (MEK), and methyl isobutyl ketone (MIBK)}, and nitrobenzene (PhNO2) were measured at 25 °C. The obtained ionic association constants (Ka) of [Ni(acac)(N,N,N′,N′-tmen)]ClO4 which were derived by using the extended Fouss–Hsia function indicated that (1) the perchlorate complex is a normal type of uni-uni-valent electrolyte and (2) it is more dissociated than [Co(acac)2(N,N,N′,N′-tmen)]ClO4 in EtOH, n-PrOH, and n-BuOH. Walden products of the cations suggest that the nickel(II) chelate cation in the alcohols is present as an octahedral form with the coordination of two solvent molecules. On the other hand, Ka of [Ni(acac)(N,N,N′,N′-tmen)]NO3 are much larger than those of [Ni(acac)(N,N,N′,N′-tmen)]ClO4. This can be ascribed to the coordination of a nitrate ion to the nickel(II) ion. The effect is large and approximately the same in the ketones and PhNO2, though small in EtOH, n-PrOH, and n-BuOH due to the coordination of solvent molecules.