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Highly Selective Extraction of Uranyl Ion by Acyclic Ligands Containing L-Phenylalanine.

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I
I
Dieses Manuskriptist
zu zitieren ais
Angew. Chem. Suppl.
This manuscript is
to be cited as
Angew. Chem. Suppl.
7983,794-802
1983,794-802
proved to be the most efficient (44% of UOZ2+ extraction versus 40% and
31% for Phe-3-0 and Phe-4-0 respectively).
Table 2. Extraction of U022+
U02(OAc)z(pH
0 Verlag Chemie GmbH. D-6940 Weinhem. 1983
0721 -4227/83/0707-0794102
50/0
CL1
=
rL]
by Phe-2-0 from an acetic solution of
4.8)
I [uo22+1
Extractions %
in CH2Cl2
Highly Selective Extraction of Uranyl Ion by Acyclic Ligends Containing
L-Phenylalanine
dM
I
Maurizio Delcanale, Rosangela Marchellif, Alessandro Mangia
, Amaldo
1
I x 10-2x
61
20
5
SO
2 x 10-511
76
4
97
250
~ o - ~ M
Dossena and Giuseppe Casnati
The extraction percentage is affected by the concentration of the ligand
and increases with the
Selective extraction of uianyi ions from aqueous solutions containing
other ionic species is a
fascinating subject both for theoretical and
Ill.
It h a s been tackled using macrocyclic
practical r e a s o n s
palydentates bearing negatively charged functions, e.g. the enolate form
of $-diketonee 121 and carboxylate anions /3/,vhich are a b l e to compete
[ ]'20U[/L
molar ratio to complete extraction
with a 70 fold excess of ligand (98%).
The change of the enion proved to
have little effect.
The extraction efficiency is v e r y sensitive to the pH of the aqueous
phase and reaches
a
maximvm at pH ca.4
( s e e Fig. 2 ) , under which
with the atable carbonate complexes present in sea water.
I41
We have recently reported the synthesis
and complexing properties
I51 of acyclic ligands containing L-phenylalanine (Pig. 1) linked by
oligaethyleneoxide bridges
high $+/Hf
amide bonds. They were shown to display
a
Figure 2. Concentration per
selectivity by spectroscopic measurements and extraction
centages of UOZ2+ W and
experiments.
Phe-2-0 @) in CH2C12
the
pH of the aqueous phase.
+Prof. Dr. R. Marchelli, Dr. M. Oelcanale, Or. A. Dossena, Prof. Dr. G.
Initial conditions:
Casnati
1.4 x 10-2M;
[U02(N03)2]=
Istituto di Chimiee Organica dell'universita'
[Phe-Z-Ol-
7.0 x 101'M.
Via M. D'Azeglio 85, 43100 Parma, Italy
conditions ligands should be, according t o their pKa values. at least
Prof. D r . A. Mangia
partially dissociated at the water-methylene chloride interphase
(see
ratituto di Chimica Generale dell'Universita'
Via H. D'Azeglio 85, 43100 Parma, Italy
- 794
-
-
796
-
later in Table 4 ) .
HN
NH
/
$C-CII2-CgH5
C6H5-CH2-CH
'coon
H00C'
Phe-1-0
X = 0
Phe-2-0
X
Phe-3-0
X
Phe-4-0
X = OnOnOnO
-db
-
High selectivity of the present ligands for the uranyl ion was also
OnDnO
ascertained by competition experiments wrth other metal cations,
reported in Table 3. Of all metals present in equal amaunt to
excess only copper and nickel cations
Pig.1. General structure of ligands Phe-n-0.
B
88
large
are extracted though to a very
small extent, while the total percentage of U O Z 2 + extracted into the
organic phase remain8 constant.
Here w e report that these ligands are particularly effective and
eelective in extracting the uranyl cation from an aqueous solution into
Table 3. Competitive extractions of metal nitrates by Phe-2-0
an organic phase (methylem chloride).
The extraction was performed by stirring a solution o f ligands Phe-n-0
(n
-
2-4) / b /
in methylene chloride (10-2-10-3 M ) with an aqueous
solution of U02(N03)2
or UO,(OAc),
i n a wide concentration range
(10-2-10-5 H ) , at various pH values and at different L/U02z* ratios, for
2 h. Determination of
uoZ2*
in the aqueous phase was made by measuring
the 650 nm absorption after treatment with Arsenazo 111 reagent 171. In
Tables 1 and 2 are reported the results obtained with ligend Phe-2-0,
which, from preliminary experiments with unbuffered aqueous solutions
Table 1. Extraction of UOZ2+ by Phe-2-0 from
U02(N03)2
LLI
P
nitric solution of
(pH = 4)
[IuOz2'7
[
L
J
/
[
u
O
z
2
'
]
Extraction
CH2C12
1.0
x
1.0 x
10-5
lo-%
1.0 x 10-2M
5
2
10~~11
20
5
~ o - ~ H
50
2 x 10-4M
48
84
90
1.0 x 10-'M
250
4
10-5M
98
1.0 x 10-21
500
2
IO-~N
98
5
2
10-hM
22
~ o - ~ M
~ o - ~ M
64
1.0
10-3~
1.0
IO-~M
20
5
1.0
~ o - ~ M
50
2
-
795
-
87
z
98
Li+
6.6
Na
X+
91
4.2 x lO-'M
1000
98
0
2.3 x I O - l M
1000
95
0
1000
97
0
10
98
0
a++ 3.9
lO-'M
x IO-'H
0
C8++
2.4
Cat+
2.4
x lO-'H
1000
97
0
Ba
7.0
10%
1
98
0
~ 10 ~
97
0
2
97
0
1
97
2.7
1
97
0.6
++
++
7.0
1
Z"++
1.9
~ o - ~ M
cu
1.6 x 10-4M
Nit+
1.7
BB
in
200
x
++
0
~
~o-~H
Init. eond.: L = 1.0 x lO-'M;
U02(N03)2
=
4
x
10-5M (pH
=
4).
The bound uranyl ion is quantitatively liberated within few minutes from
the organic phase by treatment with an aqueous 0.1 R HC1 solution.
Ligends are recovered very satisfactorily from the organic phase ( 90%).
The extraction time can be reduced from 2 h to 10-15 mi", without
significant loss of uranyl.
- 797
-
The acidity constants of ligands Phe-n-0 and the stability Constants of
by potentiometric titration in a 1:l
water:dioxane
uoZ2+ (1:~)
Ligand
Table 4. Acidity constants of Phe-n-0 and stability coastants of the
(log Kl) and 2:l (lag K2) L : U02'+
in C D ~ O D ~ .
solution under
nitrogen at 25OC and are reported in Table 4.
1:l
Table 5. 13C NKR chemical shifts of Phe-n-0 in the presence of
and 2:1 Ligand : Urenyl complexes vere determined
the corresponding 1:l
complexesa
Ligand
Phe-1-0
4.07
5.39
5.44
3.46
Phe-2-0
4.02
4.99
6.10
2.81
Phe-3-0
4.02
5.01
5.28
3.42
Phe-4-0
4.23
4.92
5.43
3.43
'
CONH
COOH
LA
(ppm'
175.1 E1.11
Phe-1-0
pl.01
=
CH-CMIH
-
'complex
171.7~0.1]
175.2
175.6 k1.61
172.8
Phe-4-0
175.OC+1.2]
172.6~l.q]
ligand]
54.9p0.71
172.4 C+0.5]
Phe-2-0
Phe-3-0
'Only
'free
54.9pO.51
p0.q
54.9pO.q
54.7[+0.q
the signals affected by the presence of UOZ(NO3),
are reported
In concluaion,the present ligands not only are very effective and
selective for the extraction of the ursnyl ion but are also particularly
efficient in the release. The msgnitudo of the stability conatants are,
*Standard deviatione are in the range 0.01-0.05.
in fact, in the most proper range to e n a b l e t h e m t o act a * t r u e
The values of pKeZ
-
pKal for Phe-"-0
(n = 1 - 4 ) are similar, ranging
from 0.69 to 1 . 3 2 pKa units, and do not provide
sufficient clues about
the conformations and potential intramolecular hydrogen bonding effects
ionophorer
/lo/.
n o r e o v e r , compared with
the previonsly reported
complexing agents 12, 3 1 , the present compounds are of much more facile
preparation.
in these compounds under the present conditions.
Extraction Procedure
All ligands provide urenyl complexes o f s i m i l a r s t a b i l i t y ,
thus
Suggesting that the ether oxygens in the bridge a r e not involved in
A methylene chloride solution of the ligend ( 1 cm3 10-2-10-3
complexation. This is elso supported by the fact that an analogous
equal volume o f aqueous solution of the metal salt (10-2-10-5 K) rere
ligand containing a hydrocarbon chain -C6H 12- (obtained from oetsndioie
1igand:uranyl complex, which had a stability
equilibrate by stirring in a stoppered centrifuge tube for 2 h at 2SoC.
Constant in the same range : log K1
phases. Every extraction w a 8 performed also vithout the figand in the
a c i d ) provided a 1:l
~
5.35.
N) and an
Centrifugation was carried out to ensure complete separation of the
methylene chloride phase (blank). All metals, excery U, vere determined
At pH values betveen 3-5 uranyl and ligands Phe-n-0 form at least tvo
in the aqueous p h a s e by
complexes both with the d i a n i o n i c s p e c i e s (L2-)
spectroscopy. UOZ2+ vas determined in both phases using Arsenazo 111:
hypotheses cannot he ruled out so far. One is
B
although other
1:l complex with the
flame and f l a m e l e s s a t o m i c a b s o r p t i o n
O.OW% nitric aqueous aolutiona of Areenezo
Ill were added to aliquots
highest formation percentage (relative to the tote1 metal present) at pH
of the aqueous phase to reach a concentration range of 0.3-6
ca 3.5;
U022i.
the other is a 2:l complex formed at pH
4.5 (Fig. 3 ) .
ppm for
The absorbance vas measured st 650 nm. The CHzC12 phases were
reextracted vith sliquots of the Araensro I11 solution, the combined
portions vere adjusted to a known volume, and meamred at 650 M.
-
798 -
-
800 -
Determination of Dissociation And Pormation Constants
Constants vere determined by potentioaretric measure-enfa
with a
Radiometer PHK 52 p o t e n t i m t e r equipped with a C2025 B glass electrode,
and
B
K 401 calomel electrode. Eo and Kv were determined by titration of
a known amount of HC1 in 0.1 K NaCl with a NaOH standard, followinO the
Gran method 1111.
In the pKa determinations, weighed amounts of Phe-n-0 yere dissolved in
1
of 1:l (v) dioxane-water and added to 14 =a3 of a stock solution
d
0.05 K in NaC104 and 0.02
n
(v) dioxane-vatcr.
in EC104 in 1:l
K, and log
In the determination of the formation constants(1og
%),
weighed a m u n t s of uranyl nitrate were added to the previously described
Figure 3. Formation percentages relative to the total concentration of
metal
o f 1:l
and
2:l
Phe-2-0
: UOZ2*
c o m p l e x e s % t h e pH.
ligand solution to obtain a 1igand:aetal
titrated at 25O
f
0.1
ratio = 5. The solutions were
under nitrogen with C02 free 0.1
automatic piston burette.
n
KOH, using an
E was measured after every 0.1
or 0.05 cm3
As far aa ligand organization in metal complexes,moleculer models (CPK)
addition. The titration in the presence of UOZ2* van carried out in the
of Phe-n-0 indicate that they can be arranged to sllow at least five or
pH range 1.0-5.0
s i x oxygen atoms to converge inwards to form penta or hexadentate
coordination in near coplanarity, vhich corresponds to the crystalline
l3C NMR spectra
structure of several uranyl salts. Actually, from the 13C NKR spectra
(Tables) there is evidence that carboxyl and amide carbonyl groups are
13C NMR spectra were recorded on a Varian XL-100 apectroaeter and the
involved in complexation, since in the presence o f uranyl salts the
c h e m i c a l ahifts were measured io ppm from T K S . 0.1 K solutions of
corresponding signals undergo significant dounfield shifts 181, whereas
ligands in anhydrous CD30D before and after addition of u r m y l nitrate
the signals of carbons adjacent to the ether oxygena in the bridge shov
(L:K = 1:l)were
no or very small variations ((0.2 ppm).
This is
measured.
in contrast with the
chemical shift behaviour observed on complexation of the same ligands
Acknowledgements:
with alkaline earth cations 151, which seem t o be located inside the
This vork v a s supported by a grant from the Italian W I .
pseudo-cavity
originated from the bridge and bound to the ether and
T h e authors thank
dr. C. Schianchi a n d prof.
P. D a l l a v a l l e for
smide carbonyl oxygena. It is conceivable that a different coordination
assistance in the determination of pKa and fo-tion
mode operates with uranyl, thusindicating
E. Dradi for recording and discussing the NW. apectra.
the preference of the latter
for carboxylate rather than for crown or aemicrovn ligation 191.
-
799 -
-
801 -
constants a d prof.
References
bei 12K durchgefuhrt: die Photolyseprodukte wurden IR-spektroskopisch charakterisiert. In allen Matrices
111 I. Tabushi, Y. Kobuke, T. Nishiya, Nature (London) 280, 665
(1979).
-
aur3er Koh-
lenmonoxid - laBt sich als erster Schritt der Photoreaktion
die Abspaltung eines Carbonylliganden und die Bildung des
121 A.H. Alberts and D.J. Cram, J. h e r . Chem. S O C . I&, 3545 (1979);
1. Tabushi, Y. Kobuke, T. Nishiya, Tetrahedron Lett., 3515 (19791
koordinativ ungesattigten 16-Elektronenfragments
C,H,M(CO)2H
nachweisen:
131 I. Tabushi, I. Kobuke, K. Ando, M. Kishimato, E . Chara, J. h e r .
Chem. Sac.
~_
102,
5948 (1980).
141 T. Lodi, R. Marchelli, A.
290
Dossena, E. Dradi, G. Casnati,
Tetrahedron 38, 2055 (1982).
~151 R. Marchelli, 1. Dradi, A. Dossena, 6 . Casnati, Tetrahedron _38
I
~
2061 (1982).
CsHsM(CO),H
[z.B.
< A < 370 nm
’
A > 370 nm
CsHsM(C0)2H
C5H5W(CO)aH: v(C0) = 2025.5/1939.5/1935.1
+
CO
cm-’; Amax
=
305 nm: CsHIW(C0)2H: v(C0) = 1956.4/1872.0 Cm-’:
I61 Phe-1-0 is not svfficiently lipophilic to allow extraction
experiments in the Concentration
ranges
used with the other
ligends.
freies CO: v(C0)
=
2138.0; in Argonmatrix be1 12x1. Die Reak-
tion kann riickgangig gemacht werden, wenn nach der Photolyse
> 370 nm) einge-
(290 < A < 370 nm) mit sichtbarem Licht ( A
/7/ H.Onishi, Y. Toite, Bunseki Kagaku
14, 1141
(1965).
strahlt wird. Die C.H,M(CO).H-Bruchstucke
181 H. Wieczorek and H. Kozlovski, Inorg. Nucl. Chem. Letters ‘6, 401
( 1980).
191 P.G. Eller, R.A. Penneman, Inorg. Chem. E , 2439 (1976).
Christensen, J.L. Oscarson, B.L. Nielsen, B.W.
1101 J.D. Lamb, J.J.
Asay, R.M. Izatt, J. Amer. Chem.
SOC.
102, 6820
(1980).
1111 G. Gran, AnalysC (London) 11,661 (1952).
geeignete Liganden L in der Matrix (L
lassen srch durch
=
N,,
C2H,,
”CO)
oder
THF, PMe,) ln Form von cis/trans-isomein Losung (L = C,H,,
ren Komplexen des Typs CsHsM(C0)2 (L)H ~tabilisieren’~’. In
CO-Matrices be1 12K kann ferner die Bildung der Radikale
CsHIM(CO) und CHO IR-spektroskopisch nachgewiesen ~ e r d e n / ~ / .
Dies deutet auf die photoinduzierte Spaltung der MetallWasserstoff-Bindung hin.
Die Photolyse der drei Carbonyl-Hydrido-Komplexe C,H,M(CO),H
Received March 1,
revised April 19, 1983 / Z 298 S /
(M = Cr, Mo, W) (ca. 2 mmol in 300 ml Pentan bei 15 OC) liefert unterschiedliche Produkte: Das gelbe, sehr luftempfindliche C,H,Cr(CO),H
wird innerhalb von ca. 20 Minuten voll]2/5/
standig in das bekannte [C,H,Cr(COl,
ubergefuhrt. Das
Photolysegas besteht aus Wasserstoff und Kohlenmonoxid. Die
TH-NMR-spektroskopische Beobachtung der Reaktion in Toluol-d,
bei -40 OC lieD keinerlei Zwischenverbindungen erkennen.
CSH,Mo(CO),H
ist wesentlich lichtbestandiger als das Cr-Deri-
vat; die vollstandige photoinduzierte Dehydrierung dauert
etwa drei Stunden; als Hauptprodukt konnte [C,H,Mo(COI,],
-
802
-
-
804
-
neben sehr wenig [C5H5M~(C0)212 isoliert werden. Der farb-
This manuscript is
to be cited as
Angew. Chem. Suppl.
1983,803-811
Dieses Manuskript ist
zu zitieren als
Angew. Chem. Suppl.
1983,803-811
lose Komplex C5HsW(CO13H reagiert im Verlauf von funf Stunden im UV-Licht nur zu ca. 80 %:
In der braunen Reaktionslo-
sung befinden sich vorwiegend [C.H.W(CO),],
[C,H,W(C0),l2.
neben sehr wenig
Das Hauptprodukt ist ein dunkelbrauner Nie-
derschlag, dessen IR-, ‘H-NMR- und massenspektroskopische
0 Verlag Chemie GmbH, D-6940 Weinheim, 1983
07214227/83107070803$02.50/0
Charakterisierung fur einen Zweikernkomplex der Zusammensetzung [ CsH5W(C0)2H]2 spricht. Fur den in Losung zersetzlichen
d m e r e n Komplex schlagen wir folgende Struktur vor:
Photolyse der cyclopentadienyl(hydrido)komplexe
(M
=
Cr,Mo, W) in
CSH.M(CO)~H
Matrix und in Losung:
Charak terisierung von [ CsHsW(C0)2H],
und, [CSMe.W(C0)2H ]Z**
von Helmut G . Alt*, Khalil A. Mahmoud und Antony J. Rest
Die Dissoziationsenergie VOn tlbergangsmetall-WasserstoffBindungen liegt beachtlich heher als die entsprechender
Ubergangsmetall-Kohlenstoff-Einfachbindungen’l’.
ES 1st daher
denkbar, daB be1 der Photolyse von Carbonyl-Hydrido-Komplexen
der erste Schritt in der Abspaltung von Carbonylliganden und
der Bildung von hochreaktiven Hydrido-Komplexfragrnenten besteht.
Wir haben die Carbonyl-Hydrrdo-Verbindungen C,H,M(CO)3H
(M
=
Cr, Mo, W), die be1 der Photolyse der Alkylkomplexe
Die beiden Hydridoliqanden ergeben im ‘H-NMR-Spektrum nur
ein einzlges Signal bei 5 = -13.24 ppm ([D6]-Aceton1. Im
Vergleich zu den Zweikernkomplexen H,Re.(COls
ppm, in CDCl,)/6/
und [C,Me,Os(CO)H]z
( 6 = -19.04
( 5 = -18.60 ppm, in
CD2C1,)/7a/, die ebenfalls eine Metall-Metall-Doppelbindung
aufweisen, sind die Wasserstoffbruckenliganden in
[C5HsW(C0)2H]2 wesentlich starker entschirmt. Die Intensitat
der Wolframsatelliten, J(W,H) = 83.1 Hz, betragt 24 % der
Hydridosignalintensitat und beweist somit eindeutig den
CsH,M(CO),R
(M = MO, W ; R = Et, “Pr, “Bu) entstehen/2/,
in Losung bestrahlt ( A > 300 nm) und die Reaktionsprodukte
Bruckencharakter der Hydridoliganden. Auch die GrOBe der
J(WHW)-Kopplung liegt beachtlich hoher als “on terminalen
isoliert. Zur Aufklarung der photochemischen Primarschritte
wurde die Photolyse auch in Gasmatrices (Ar, CH,, Nn, CO)
Hydridoliganden [ (J(W,H) = 20 - 40 Hz) 1 . Weitere Hinweise
auf einen symmetrrschen B a u des Zweikernkomplexes liefert
das IR- und das ‘H-NMR-Spektrum: die vier Carbonylliganden
Priv.-Doz. Dr. H. G. Alt
Laboratorium fur Anorganische Chemie der Universitat
Bayreuth, UniversitltsstraBe 30, D-8580 Bayreuth
Dr. A. J. Rest und K. A. Mahmoud
Department of Chemistry, The University
Southampton, SO9 5NH, England
**
zeigen nur zwei CO-Banden (1930 und 1860 cm-‘, in Toluol),
die beiden C,H,-Liganden ergeben nur ern einziges Singulettsignal be1 tiefem Feld ( 5 = 6.14 ppm, in [D,]-Aceton). Xhnl x h e spektroskopische Daten sind fiir den kiirzlich dargestellten Osmiumkomplex [C,Me,Os (CO)H],/7/ angegeben worden.
Diese Arbeit wurde von der Deutschen Forschungsgemeinschaft und dem Fonds der Chemischen Industrie unterstutzt.
-
803
-
-
805
-
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