Structure of organophosphorus acid extractants and their steric effect / Chin. J. Inorg. Chem.

Steric effect of organophosphorus acid extractants (OPA) with the structure of R(R')P(O)OH plays an important role in the selectivity for different metals. Until now, there is no widely accepted structure parameter for description of the effect. It is suggested in the present paper to take the angle between the two substituting groups and the phosphorous atom, angle RPR' as the steric parameter of the extactants. In an octahedral configuration of the extracts, the substituting groups from the two coor-inated OPA are approximately in the same plane, larger the angle RPR', larger the interaction between them, resulting in a higher steric effect. In a tetrahedral configuration, the substituted groups sre located in two perpendicular planes, the streric effect is much weaker. As Co2+ is extracted by OPA, the change of the thermodynamic parameters of conversion of octahedral to tetrahedral configuration of the cobalt extracts is in accordance with the angle RPR' of the extractants. / Steric effect of organophosphorus acid extractants (OPA) with the structure of R(R')P(O)OH plays an important role in the selectivity for different metals. Until now, there is no widely accepted structure parameter for description of the effect. It is suggested in the present paper to take the angle between the two substituting groups and the phosphorous atom, angle RPR' as the steric parameter of the extactants. In an octahedral configuration of the extracts, the substituting groups from the two coor-inated OPA are approximately in the same plane, larger the angle RPR', larger the interaction between them, resulting in a higher steric effect. In a tetrahedral configuration, the substituted groups sre located in two perpendicular planes, the streric effect is much weaker. As Co2+ is extracted by OPA, the change of the thermodynamic parameters of conversion of octahedral to tetrahedral configuration of the cobalt extracts is in accordance with the angle RPR' of the extractants.