- Email: [email protected]
Regularities associated with the formation of lanthanide and actinide complexes
INORG. NUCL. CHEM. LETTERS
Vol. 7,
pp.
305-306, 1971. Pergamon
Press.
Printed in Great Britain.
REGULARITIES ASSOCIATED WITH THE FORMATION OF LANTHANIDEAND ACTINIDE COMPLEXES* by Richard Mo Wallace Savannah River Laboratory E. I. du Pont de Nemours and Company Aiken, South Carolina 29801 ~ e c e i v e d 19 June 1970)
In a recent
paper,
Siekierski
(1)
reported
finding
new r e g u l a r i t i e s
in
the stability constants of trivalent lanthanide and actinide ions with a variety of ligandso
The purpose of this present communication is to show
that these regularities may be a result of the method used to establish them, rather than an inherent property of the lanthanides or actinides. The procedure used by Siekierski to establish regularities was to plot the free energy of complex formation between lanthanides and a ligand versus the atomic number of the lanthanide.
Straight lines were then drawn between
the following lanthanide pairs La-Nd, Pm-Gd, Gd-Ho, and Er-Luo
The experi-
mental points between each of these pairs was then shown to usually fall below these line segments.
This procedure was derived from variations in
the free energy in certain solvent extraction systems where the regularities are obvious; however, if applied in general, the procedure will lead to the sought for regularities where none exist. If applied to a smooth curve for example, the procedure is equivalent to drawing chords to the curve and determining if the curve falls above or below the chords.
The curve will, of course, always fall below the line segments if
* The information contained in this article was developed during the course of work under Contract AT(07-2)-1 with the U. S. Atomic Energy Commission. 305
306
LANTHANIDE AND ACTINIDE COMPLEXES
Vol. 7, No. 4
I I I I I I I T I I I I I I ID
-6 o
(.P
-.I0
I
~9 <3 0
-2 L9 <3
-4
I 1 1 1 1 1 1 1 1 i [ 1 1 [
La Ce Pr Nd PmSmPuGdTbDy HoEr TmYb Lu FIG.
I
APPLICATION
OF S I E K I E R S K I PROCEDURE TO QUADRATIC CURVE
the curve is concave upward (i.e., the second derivative is positive).
In
Figure i, the appIication of the Siekierski procedure to a hypothetical system is shown in which the plot of ~G vs atomic number is a simple quadratic relation
AG = -X + .05 X 2,
where X = (atomic number - 57).
The lower
part of the figure shows the curve and the chords along which interpolations are made.
The upper part is a plot, AG - AG (interpolated) vs atomic number,
which shows the same regularities as similar plots with experimental data in reference I.
Clearly, the procedure will show the desired regularities when
applied to any set of data with the proper curvature, and, therefore, cannot be expected to tell much about the chemistry of the lanthanides and actinides.
References (I)
S. SIEKIERSKI, J. Inorg. Nucl. Chem. 32, 519 (1970).
Vol. 7,
pp.
305-306, 1971. Pergamon
Press.
Printed in Great Britain.
REGULARITIES ASSOCIATED WITH THE FORMATION OF LANTHANIDEAND ACTINIDE COMPLEXES* by Richard Mo Wallace Savannah River Laboratory E. I. du Pont de Nemours and Company Aiken, South Carolina 29801 ~ e c e i v e d 19 June 1970)
In a recent
paper,
Siekierski
(1)
reported
finding
new r e g u l a r i t i e s
in
the stability constants of trivalent lanthanide and actinide ions with a variety of ligandso
The purpose of this present communication is to show
that these regularities may be a result of the method used to establish them, rather than an inherent property of the lanthanides or actinides. The procedure used by Siekierski to establish regularities was to plot the free energy of complex formation between lanthanides and a ligand versus the atomic number of the lanthanide.
Straight lines were then drawn between
the following lanthanide pairs La-Nd, Pm-Gd, Gd-Ho, and Er-Luo
The experi-
mental points between each of these pairs was then shown to usually fall below these line segments.
This procedure was derived from variations in
the free energy in certain solvent extraction systems where the regularities are obvious; however, if applied in general, the procedure will lead to the sought for regularities where none exist. If applied to a smooth curve for example, the procedure is equivalent to drawing chords to the curve and determining if the curve falls above or below the chords.
The curve will, of course, always fall below the line segments if
* The information contained in this article was developed during the course of work under Contract AT(07-2)-1 with the U. S. Atomic Energy Commission. 305
306
LANTHANIDE AND ACTINIDE COMPLEXES
Vol. 7, No. 4
I I I I I I I T I I I I I I ID
-6 o
(.P
-.I0
I
~9 <3 0
-2 L9 <3
-4
I 1 1 1 1 1 1 1 1 i [ 1 1 [
La Ce Pr Nd PmSmPuGdTbDy HoEr TmYb Lu FIG.
I
APPLICATION
OF S I E K I E R S K I PROCEDURE TO QUADRATIC CURVE
the curve is concave upward (i.e., the second derivative is positive).
In
Figure i, the appIication of the Siekierski procedure to a hypothetical system is shown in which the plot of ~G vs atomic number is a simple quadratic relation
AG = -X + .05 X 2,
where X = (atomic number - 57).
The lower
part of the figure shows the curve and the chords along which interpolations are made.
The upper part is a plot, AG - AG (interpolated) vs atomic number,
which shows the same regularities as similar plots with experimental data in reference I.
Clearly, the procedure will show the desired regularities when
applied to any set of data with the proper curvature, and, therefore, cannot be expected to tell much about the chemistry of the lanthanides and actinides.
References (I)
S. SIEKIERSKI, J. Inorg. Nucl. Chem. 32, 519 (1970).