The complex formation of aluminum(III) with phosphinate and phosphite ions in acidic solutions (pH 1-3) has been investigated by 27Al NMR spectroscopy. The formation of a 2:2 complex was established in addition to ordinary stepwise complexes in both Al3+-PH2O2- and -PHO32- systems. Formation constants of these complexes formed in both systems, and thermodynamic quantities for the complexation in the Al3+-PH2O2- system were determined at an ionic strength of 1.0 moldm-3 NaClO4. The stepwise complexation up to 1:3 becomes more exothermic and less entropy-productive in a regular manner. Both ΔH° and ΔS° values for the 2:2 complexation are quite large and positive due to the dimerization.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Inorganic Chemistry
- Materials Chemistry