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

• Published in: Analytical Sciences Vol. 27; no. 12; p. 1207
• Main Authors: KUDO, Yoshihiro, KOIDE, Tsukasa, ZHAO, Yujie, KATSUTA, Shoichi, TAKEDA, Yasuyuki
• Format: Journal Article
• Language: English
• Published: Singapore The Japan Society for Analytical Chemistry 2011; Springer Nature Singapore
• Subjects: Analytical Chemistry; Chemistry
• ISSN: 0910-6340; 1348-2246
• DOI: 10.2116/analsci.27.1207

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.