Calorimetric and Raman Spectroscopic Studies of Cadmium(II) Thiocyanato Complexes in N,N-Dimethylformamide

Article abstract of DOI:10.1246/bcsj.61.3901

Formation of thiocyanato complexes of cadmium(II) ion has been calorimetrically studied in N,N-dimethylformamide (DMF) at 25 deg C.Calorimetric data obtained were well explained in terms of the formation of a series of four mononuclear n>^(2-n)+ (n=1-4, X=SCN) complexes, and their formation constants, enthalpies, and entropies were determined.Raman band shifts for the C-S stretching vibration of SCN^- ion indicated that SCN^- ion binds to cadmium(II) ion only with the N end within the mono- or dithiocyanato complex, ⁺ or .Within the tri- and tetracyanato complexes, thiocyanate ions bind with both the N and S ends, and the coordination modes, ^- and ^2-, were suggested.The coordination modes for the di- and tetrathiocyanato complexes in DMF, and ^2-, are different from those in water, and >Cd(NCS)2(SCN)>^2-.It is thus shown that the N-bonding becomes more favorable in DMF than in water.Such a result may mainly be ascribed to relatively weakened solvation of the SCN^- ion in DMF, especially at the N atom site which is hydrogen-bonded with water molecules but not with DMF.