Solvating extractants donor atoms

Solvating extractants contain one or more electron donor atoms, usually oxygen, which can supplant or partially supplant the water which is attached to the metal ions. Perhaps the best known example of such an extractant is tri-( -butyl) phosphate) [126-73-8] (TBP), which forms... 

In liquid-liquid extraction by solvation, the solvent itself takes part in complexation of the metal ion. This is brought about by donation of electrons by the donor atom present in the solvent molecule to the coordination sphere of the metal ion. Such an association of the solvent molecules with the metal ion results in the formation of a solvated complex that is extractable in the solvent. Thus, for example, octanol, Cg H17-OH, extracts Co2+ in the presence of perchlorate ion as [Co (C8 H17-OH)] (C104)2. Extraction by solvation generally employs oxygenated solvents such as alcohols, ethers or ketones or neutral organophosphorus compounds. These solvents stand the competition from water for solvation of the metal ion successfully because of the higher availability of electrons from their donor atoms. 

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