Solvation and Ionic Association of Bis(β-diketonato)(diamine)cobalt(III) Perchlorates in Alcohols and Ketones

Abstract

Abstract The conductances of bis(2,4-pentanedionato)(diamine)cobalt(III) perchlorates, [Co(acac)2(diamine)]ClO4 (where acac:2,4-pentanedionato; diamine:en (ethylenediamine) and N,N,N′,N′-tmen (N,N,N′,N′-tetramethylethylenediamine)) in methanol (MeOH), ethanol (EtOH), 2-propanol (i-PrOH), methyl ethyl ketone (MEK), and methyl isobutyl ketone (MIBK) and of bis(β-diketonato)(ethylenediamine)cobalt(III) perchlorates, [Co(β-dik)2(en)]ClO4 (where β-dik: acacBr (3-bromo-2,4-pentanedionato) and acacNO2 (3-nitro-2,4-pentanedionato)) in EtOH, acetone (Me2CO), and MEK were measured at 25 °C. [Co(acac)2(en)]ClO4 in the alcohols was found to be more dissociated than [Co(acac)2(N,N,N′,N′-tmen)]ClO4. This behavior was explained as being due to the strong solvation of [Co(acac)2(en)]+ by the alcohols. [Co(acac)2(N,N,N′,N′-tmen)]+ seems to be solvated in ketones rather than alcohols. The sequence of the ionic association constant for [Co(β-dik)2(en)]ClO4, acac<acacBr<acacNO2, could be interpreted in terms of an enhanced polarity of the cations with the electron-withdrawing groups.