Sequestration of Alkyltin(IV) Compounds in Aqueous Solution: Formation, Stability, and Empirical Relationships for the Binding of Dimethyltin(IV) Cation by N- and O-Donor Ligands

Abstract

The sequestering ability of polyamines and aminoacids of biological and environmental relevance (namely, ethylenediamine, putrescine, spermine, a polyallylamine, a branched polyethyleneimine, aspartate, glycinate, lysinate) toward dimethyltin(IV) cation was evaluated. The stability of various dimethyltin(IV) / ligand species was determined inNaClaqatt=25∘Cand at different ionic strengths(0.1≤I/mol L-1≤1.0), and the dependence of stability constants on this parameter was modeled by an Extended Debye-Hückel equation and by Specific ion Interaction Theory (SIT) approach. AtI=0.1molL−1, for the ML species we have logK=10.8, 14.2, 12.0, 14.7, 11.9, 7.7, 13.7, and 8.0 for ethylenediamine, putrescine, polyallylamine, spermine, polyethyleneimine, glycinate, lysinate, and aspartate, respectively. The sequestering ability toward dimethyltin(IV) cation was defined by calculating the parameterpL50(the total ligand concentration, as−logCL, able to bind 50% of metal cation), able to give an objective representation of this ability. Equations were formulated to model the dependence ofpL50on different variables, such as ionic strength and pH, and other empirical predictive relationships were also found.