Calorimetric study on complexation of copper(II) ion with some amide solvents in acetonitrile

Complexation of copper(II) ion with some amide solvents such as N-methylformamide (NMF), formamide (FA), N,N-dimethylacetamide (DMA) and N-methylacetamide (NMA) has been studied by titration calorimetry in acetonitrile containing 0.1 mol dm−3 (C2H5)4ClO4 as an ionic medium at 298 K. These amides coordinate to the metal ion to form a series of mononuclear complexes, and their formation constants, enthalpies and entropies have been obtained. Thermodynamic parameters of formation of Cu(NMF)2+ and Cu(FA)2+ are not significantly different from those of Cu(DMF)2+ (DMF: N,N-dimethylformamide), implying that a strong hydrogen-bonded structure of liquid NMF and FA are practically ruptured in the acetonitrile solution examined. The formation of Cu(DMA)2+ and Cu(NMA)2+ are appreciably less exothermic than the respective formation of Cu(DMF)2+ and Cu(NMF)2+ complexes, implying that the presence of the acetyl group causes steric hindrance upon its coordination to the metal ion.