Analytical Sciences

Abstract − Analytical Sciences, 27(12), 1207 (2011).

Ion-pair Formation between Cd(II), Na(I), and Ag(I) Complex Ions with 18-Crown-6 Ether Derivatives and Various Pairing Anions in Water: an Understanding of the Ion-pair Formation Based on the HSAB Principle
Yoshihiro KUDO,* Tsukasa KOIDE,** Yujie ZHAO,* Shoichi KATSUTA,* and Yasuyuki TAKEDA*
*Graduate School of Science, Chiba University, Chiba 263-8522, Japan
**Department of Chemistry, Faculty of Science, Chiba University, Chiba 263-8522, Japan
The ion-pair formation constants (KMLX0/mol−1 dm3) of CdL2+ with Br or NaL+ with N,N-diethyldithiocarbamate ion (DDTC) in water were determined potentiometrically at 25°C; ionic strength (I)→0: L denotes 18-crown-6 ether (18C6) and its mono-benzo derivative for the CdBr2-L system and 15-crown-5 ether and 18C6 for the NaDDTC-L one. The formation constant corresponding to the simple salt, NaDDTC, in water was also determined at I→0. Using the log KCdLX0 values of CdLCl+, CdLBr+, CdLPic+, and CdLSO4, then CdL2+ and picrate ion (Pic) in water have been classified with the hard and soft acids and bases principle, where the values were available in the literature, except for CdLBr+. The same classification was examined in NaX-L systems with X = DDTC, trifluoroacetate ion, MnO4, ReO4, Pic, and BPh4 and the AgPic-L one. Consequently, CdL2+, NaL+, and AgL+ were classified as the hard acids, while Pic and BPh4 as the hard bases. These results reflected the reactivities of the complex ions in ion-pair formation with X and SO42− in water.