Erbium Chloride Complexation in Aqueous DMF

  • Herbert B. Silber
  • M. Rebecca Riddle


In water or mixed aqueous solvents, ErCl2+ complexation occurs via the following multi-step mechanism:

$${\text{E}}{{\text{r}}^{{\text{3 + }}}}\left( {\text{S}} \right)\,{\text{ + }}\,{\text{C}}{{\text{l}}^{\text{ - }}}\left( {\text{S}} \right)\,{\text{ = }}\,{\text{E}}{{\text{r}}^{{\text{3 + }}}}\left( {\text{S}} \right){\text{C}}{{\text{l}}^{\text{ - }}}\,{\text{ = }}\,{\text{ErC}}{{\text{l}}^{{\text{2 + }}}}\left( {\text{S}} \right)\,\left( 1 \right)$$

where S represents bound solvent, Er2+(S)Cl- is an outer-sphere complex and ErCl2+(S) is an inner sphere complex. The ultrasonic adsorption, α/f2, equals:

$$\alpha {\text{/}}{{{\text{f}}}^{{\text{2}}}}{\mkern 1mu} {\text{ - }}{\mkern 1mu} {\text{B}}{\mkern 1mu} {\text{ = }}{\mkern 1mu} {{{\text{A}}}_{{{\text{os}}}}}{\text{/}}\left( {{\text{1 + }}{{{\left( {{\text{f/}}{{{\text{f}}}_{{{\text{os}}}}}} \right)}}^{{\text{2}}}}} \right){\mkern 1mu} {\text{ + }}{\mkern 1mu} {{{\text{A}}}_{{{\text{is}}}}}{\text{/}}\left( {{\text{1 + }}{{{\left( {{\text{f/}}{{{\text{f}}}_{{{\text{os}}}}}} \right)}}^{{\text{2}}}}} \right){\mkern 1mu} \left( {\text{2}} \right) $$

where Aos and Ais are the amplitudes of the outer and inner sphere complexes, Fos and fis are the respective relaxation frequencies and B is the solvent background. The excess adsorption maxium µmax is equal to the product of one-half of the relaxation frequency, the relaxation amplitude and the solution sound velocity. At constant salt concentration, µmax is proportional to the square of the reaction volume change. If a coordination number change accompanies complexation, a plot of µmax is a function of water mole fraction, XH 0, has a maximum. In the absence of a coordination number change, µmax decreases with increased water content due to reduced complexation. For ErCl2+ formation in aqueous methanol (2) the coordination number change is absent, but is present in aqueous DMSO (3). This study in aqueous DMF was initiated to study the effect of solvent on coordination number in the Er(III) system.


Aqueous Methanol Increase Water Content Sphere Complex Excess Adsorption Ultrasonic Absorption 
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Copyright information

© Plenum Press, New York 1982

Authors and Affiliations

  • Herbert B. Silber
    • 1
  • M. Rebecca Riddle
    • 1
  1. 1.Division of Earth and Physical SciencesThe University of Texas at San Antonio (UTSA)San AntonioUSA

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