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Synthesis and characterization of caesium tetrachlorouranate(III) tetrahydrate
Journal of the Less-Common Metals, 163 (1990) 159- 164
159
SYNTHESIS AND CHARACTERIZATION OF CAESIUM TETRACHLOROURANATE(II1) TETRAHYDRATE M. KARBOWIAK
and J. DROiDiYfiSKI
Institute of Chemistry, University of Wroctaw, 50-383 Wrocfaw (Poland) (Received February 16,199O)
Summary A new U(III) compound of the formula CsUCl,*4H,O has been synthesized, and some of its structural, spectroscopic and magnetic properties have been determined. The complex chloride belongs to the monoclinic system with a = 8.043 A, 6 = 8.671 A, c = 7.112 A, 0 = 99.28” and 2 = 2. Magnetic susceptibility measurements were carried out by the Faraday method in the 4.2-300 K temperature range. The Curie-Weiss law is followed in the 180-300 K region with the paramagnetic constants perr = 3.27 B.M. and f3= 29 K. The IR and electronic spectra of the compound in the solid state were recorded in the SO-4000 cm-’ and 4000-25 000 cm- l absorption ranges respectively and are discussed.
1. Introduction
In a previous paper [l] the synthesis and the characterization of potassium, rubidium and ammonium tetrachlorouranate( III) tetrahydrates have been reported. By using a somewhat modified method we were able to synthesize a further specimen in the series of compounds, i.e. CsUC1,.4H,O. As well as the expected similarities, some remarkable differences can be noted when compared ‘with the physico-chemical properties of the compounds previously reported.
2. Experimental
details
2.1. Synthesis The compound could not be obtained using the previously reported procedure for the preparation of the analogous potassium, rubidium and ammonium tetrachlorouranate( III) tetrahydrates because of the immediate formation of an insoluble precipitate resulting from the reaction of the dissolved UCl, with CsCl. For the synthesis of CsUCl,*4H,O two solutions were prepared consisting of: ( 1) 60 cm3 acetonitrile, 6 cm3 propionic acid, 1 cm3 water and an excess (about 1 g) of CsCl, and (2) 30 cm3 acetonitrile, 3 cm3 propionic acid and about 1.3 g UC&. 0022-5088/90/$3.50
0 Elsevier Sequoia/Printed
in The Netherlands
160
The solutions were well shaken and left to stand for at least 24 h. After filtering, about 0.5 cm3 of water was added to solution (2) in order to avoid some coprecipitation of CsCl during the further preparation procedure. The filtered solution (1) was slowly added to solution (2) and reduced in an inert atmosphere using a liquid zinc amalgam. The reduction resulted in the immediate formation of a fine crystalline, brown-green precipitate of the formula CsUCl,*4H,O. The opposite procedure, i.e. the addition of solution (2) to solution ( 1), resulted in the precipitation of an insoluble U(IV) complex chloride. The precipitate of CsUCl,*4H,O was thoroughly washed with a degassed 1:40 solution of propionic acid and acetonitrile, and finally washed with freshly distilled ether. The compound was then carefully dried under reduced pressure at 20°C and stored under nitrogen in sealed tubes at temperatures below 15 “C. The synthesis was carried out in an allglass apparatus with provisions for precipitation, filtration and drying in an inert atmosphere [2]. Somewhat larger crystals can be obtained by using a 1: 3.5 propionic acid solution diluted with acetonitrile which has been left standing above the liquid zinc amalgam without shaking for about 36 h. In any case the yield of the reaction was poor and much lower when compared with the yields obtained in the synthesis of the potassium, rubidium and ammonium tetrachlorouranate(II1) tetrahydrates. 2.2. Ana Iytical data Analysis calculated for CsUCl,*4H,O: Cs, 22.83; U, 40.70; H, 1.38. Found: Cs, 23.10; U, 40.92; Cl, 24.18; H, 1.29.
Cl, 24.25;
2.3. Physical measurements X-ray powder diffraction data were collected at the Institute of Low Temperature and Structure Research in Wroclaw on a computerized STADI P diffractometer combined with a Mera 79100 monitor, using Cu Ka, radiation. Unit cell parameters were obtained by least-squares refinement of 3 1 values for all observed reflections. The magnetic susceptibility was measured by the conventional Faraday method on a powdered sample sealed in a quartz tube at a field of 6 KOe and temperatures ranging from 4 to 300 K. The values were corrected for diamagnetic increments. The solid state absorption spectrum of the compound was recorded on a Cary-Varian 2300 spectrophotometer in the 4000-24 000 cm-’ range. In order to obtain the electronic spectrum a well ground mixture of the compound with some Halowax oil (chlorinated naphthalene, refraction index of 1.635) was placed between two quartz windows, pressed to get a transparent and uniform layer, and put into the cell compartment of the spectrophotometer. The IR spectra were recorded on Perkin-Elmer 180 and 789 spectrophotometers using hexachlorobutadiene and nujol mulls as well as KRr, CaF, and polyethylene plates.
161
3. Results and discussion 3.1. Characterization of the compound CsUCl,.4H,O precipitates from the solution in the form of brown-green, fine crystalline monoclinic crystals. The compound is not resistant to oxidation by air and may lose some of its water of crystallization at temperatures as low as 20 “C. As with almost all hydrated U(II1) halides and complex halides [3], the compound is easily soluble in a number of more polar organic solvents such as methanol, ethanol, formic acid, tributylphosphate and formamide. In water and aqueous acidic solutions it dissolves with oxidation to U(IV). The hydrate may be easily converted through thermal dehydration into the anhydrous salt by applying an TABLE Observed
1 and calculated
d spacings
hkl
4,
1 0 0 0 0 1 1 1 0
8.0040 7.0717 5.8676 5.7383 5.4632 4.7839 4.3345 4.2654 3.80 1 1 3.6169 3.4172 3.2436 3.1809 2.9249 2.8241 2.7263 2.6737 2.5916 2.5306 2.5068 2.4848 2.4438 2.3556 2.3359 2.2541 2.2190 2.1610 2.0854 2.0675 1.9485 1.8148
i 0 i 0 1 1 i i I 020 1 1 1 120 2 1 0 i 1 1 1 2 1 i 12 2 2 0 221 022 031 221 310 3 1 1 122 202 301 230 320 3 1 2 231 113 321 330 421
and observed
relative
intensities
for CsUCl,.4H20
III,, 7.9373 7.0189 5.8547 5.7373 5.4555 4.7847 4.3354 4.2539 3.8049 3.6086 3.4198 3.2416 3.1817 2.9274 2.8238 2.7278 2.6726 2.5943 2.5306 2.5072 2.4857 2.4409 2.3536 2.3364 2.2584 2.2217 2.1563 2.0886 2.0684 1.9516 1.8128
59.0 29.6 16.9 39.8 43.1 58.4 68.6 100.0 21.3 67.8 30.6 16.4 22.1 26.9 52.4 55.0 25.0 11.2 25.8 11.3 46.2 12.1 20.1 31.3 27.3 22.3 32.9 13.2 17.9 10.9 11.4
162
effective non-static high vacuum system. For this purpose the temperature was slowly and gradually increased from 20 to 400 “C at a vacuum of 10e5 to lo-” hPa. The anhydrous compound was first identified during investigations of the binary fused salt system CsCl-UCl, along with X-ray powder diffraction analysis (cubic, a = 9.16 A) [4]. Further investigations are in progress [5]. Analysis calculated for CsUCl,: Cs, 25.92; U, 46.42; Cl, 27.66. Found: Cs, 26.18; U, 46.21; Cl, 27.64. 3.2. X-ray powder di$raction analysis The observed and calculated d spacings together with the observed relative intensities for CsUC1,*4H,O are listed in Table 1. The data show that the compound crystallizes in the monoclinic system and possesses the following lattice parameters: a = 8.043 A, b= 8.671 A, c= 7.112 A, /3 = 99.28”, V= 489.48 A3, Z = 2, dca,c.= 3.97 g crnm3 and dpyk,= 4.15 g cmp3. Unfortunately, the space group could not be determined unambiguously and is either P2 or Pm. 3.3. IR spectra The IR and far-IR spectra of the compound are similar to those of the potassium, rubidium and ammonium tetrachlorouranate(II1) tetrahydrates [ 11. In the 1550-1650 and 2850-3600 cm-’ absorption regions strong and broad bands
1‘Yc; 2oc
150
1oc
50
/ / / /
0
50
I
I
I
I
100
150
200
250
*
TI'KI
Fig. 1. Inverse magnetic susceptibility of CsUC1,.4H,O
VS.temperature.
163
are observed, characteristic of the stretching and bending modes of coordinated water with maxima at 1607, 1630, 3190, 3335 and 3410 cm-‘. In the spectrum the typical bands may also be noted for the coordinated water multiplet at 400-700 cm-’ with components at 465,482,518,535,615 and 672 cm-’ which corresponds to the rocking and wagging modes [6]. As in the case of the potassium, rubidium and ammonium tetrahydrates, the Y(U-Cl) stretching vibration appears as a broad multiplet of strong intensity with well-resolved bands at 156, 166, 194 and 218 cm-‘. The S(Cl-U-Cl) bending mode appears at 132 cm-i. Some other bands observed in this range probably correspond to lattice modes. 3.4. Magnetic susceptibilities and electronic spectrum The inverse magnetic susceptibility vs. temperature plot exhibits the Curie-Weiss dependence xi = C/( T- f3) in the 180-300 K range with the paramagnetic constants j+, = 2.84 co.5= 3.27 B.M. and 19= 29 K. The derived effective magnetic moment is typical of U( III) compounds but is somewhat lower than those reported for the potassium, rubidium and ammonium tetrahydrates [ 11. At temperatures lower than 180 K the plot curves above the Curie-Weiss line approaching l/x h = 0 (Fig. 1). The unusual temperature dependence of the reciprocal magnetic susceptibility in this range may be understood in terms of crystal field effects. Such a magnetic behaviour of Kramer’s ion U3+ is expected when the CF ground state of the ion bears a much smaller magnetic moment than its first
5
10
15
20
25 cm-’ x lo-'
Fig. 2. Absorption
spectrum of CsUC1,.4H,O.
164
The solid state absorption spectrum of CsUCI,*4H,O (Fig. 2) is similar to those reported for UCl,*7H,O [7] and the aquo-ion [8, 93. Contrary to the earlier reported spectra of KUCl,*4H,O, RbUCl,*4H,O and NH,UCl,*4H,O [l], no strong 5f3-5f26d1 absorption bands in the 15000-21000 cm-’ range are observed. The appearance of such bands in the visible region has been attributed to an increase in covalency or reducing character of the ligands [lo]. In accordance with this statement, in the solid state absorption spectra of U(II1) chlorocomplexes, an essential red shift of the wavenumbers of the first strong f-d bands with decreasing U-Cl lengths and coordination numbers lower than nine may be noticed [3, lo]. Hence, we may expect the presence of the water molecules in the first coordination sphere of CsUCl,*4H,O and a coordination number larger than nine.
Acknowledgments The financial support of the Polish Academy of Sciences is gratefully acknowledged. The authors would like to thank Mr. J. Jariczak of the Institute.of Low Temperature and Structure Research in Wroclaw for determination of the X-ray powder diffraction values and Mr. E. Zych of the Institute of Chemistry of the Wroclaw University for technical assistance. References J. Less-Common Met., 32 (1988) 271. Inorg Chim. Actu, 32 (1979) L83. in A. J. Freeman and C. Keller (eds.), Handbook on the Physics and Chemistry of theActinides,Vol. 6, North-Holland Physics Publishing, Amsterdam, 1990. I. G. Suglobova and D. E. Chirkst, Sov. J. Coord. Chem., 7( 1981) 52. M. Karbowiak and J. Droidiyriski, J. Less-Common Met., to be published. C. Postmus and J. R. Ferraro, J. Chem. Phys., 48 (1968) 3428. J. Droidiynski, fnorg. Chim. Acta, 109 (1985) 79. W. T. Carnal1 and B. G. Wybourne, J. Chem. Phys., 40 (1964) 3428. J. DroidPyriski, J. Inorg. Nucl. Chem., 40 (1978) 319. J. Droidiyriski, in Rare Earth Spectroscopy, Proc. Rare Earth Spectroscopy Symp. RES-84, Wrocfaw, September IO-15,1985, World Scientific Publishing, Singapore, 1985, pp. 57-80.
1 J. Droidiyriski, 2 J. Droidiyriski, 3 J. Droidiytiski, 4 5 6 7 8 9
10
159
SYNTHESIS AND CHARACTERIZATION OF CAESIUM TETRACHLOROURANATE(II1) TETRAHYDRATE M. KARBOWIAK
and J. DROiDiYfiSKI
Institute of Chemistry, University of Wroctaw, 50-383 Wrocfaw (Poland) (Received February 16,199O)
Summary A new U(III) compound of the formula CsUCl,*4H,O has been synthesized, and some of its structural, spectroscopic and magnetic properties have been determined. The complex chloride belongs to the monoclinic system with a = 8.043 A, 6 = 8.671 A, c = 7.112 A, 0 = 99.28” and 2 = 2. Magnetic susceptibility measurements were carried out by the Faraday method in the 4.2-300 K temperature range. The Curie-Weiss law is followed in the 180-300 K region with the paramagnetic constants perr = 3.27 B.M. and f3= 29 K. The IR and electronic spectra of the compound in the solid state were recorded in the SO-4000 cm-’ and 4000-25 000 cm- l absorption ranges respectively and are discussed.
1. Introduction
In a previous paper [l] the synthesis and the characterization of potassium, rubidium and ammonium tetrachlorouranate( III) tetrahydrates have been reported. By using a somewhat modified method we were able to synthesize a further specimen in the series of compounds, i.e. CsUC1,.4H,O. As well as the expected similarities, some remarkable differences can be noted when compared ‘with the physico-chemical properties of the compounds previously reported.
2. Experimental
details
2.1. Synthesis The compound could not be obtained using the previously reported procedure for the preparation of the analogous potassium, rubidium and ammonium tetrachlorouranate( III) tetrahydrates because of the immediate formation of an insoluble precipitate resulting from the reaction of the dissolved UCl, with CsCl. For the synthesis of CsUCl,*4H,O two solutions were prepared consisting of: ( 1) 60 cm3 acetonitrile, 6 cm3 propionic acid, 1 cm3 water and an excess (about 1 g) of CsCl, and (2) 30 cm3 acetonitrile, 3 cm3 propionic acid and about 1.3 g UC&. 0022-5088/90/$3.50
0 Elsevier Sequoia/Printed
in The Netherlands
160
The solutions were well shaken and left to stand for at least 24 h. After filtering, about 0.5 cm3 of water was added to solution (2) in order to avoid some coprecipitation of CsCl during the further preparation procedure. The filtered solution (1) was slowly added to solution (2) and reduced in an inert atmosphere using a liquid zinc amalgam. The reduction resulted in the immediate formation of a fine crystalline, brown-green precipitate of the formula CsUCl,*4H,O. The opposite procedure, i.e. the addition of solution (2) to solution ( 1), resulted in the precipitation of an insoluble U(IV) complex chloride. The precipitate of CsUCl,*4H,O was thoroughly washed with a degassed 1:40 solution of propionic acid and acetonitrile, and finally washed with freshly distilled ether. The compound was then carefully dried under reduced pressure at 20°C and stored under nitrogen in sealed tubes at temperatures below 15 “C. The synthesis was carried out in an allglass apparatus with provisions for precipitation, filtration and drying in an inert atmosphere [2]. Somewhat larger crystals can be obtained by using a 1: 3.5 propionic acid solution diluted with acetonitrile which has been left standing above the liquid zinc amalgam without shaking for about 36 h. In any case the yield of the reaction was poor and much lower when compared with the yields obtained in the synthesis of the potassium, rubidium and ammonium tetrachlorouranate(II1) tetrahydrates. 2.2. Ana Iytical data Analysis calculated for CsUCl,*4H,O: Cs, 22.83; U, 40.70; H, 1.38. Found: Cs, 23.10; U, 40.92; Cl, 24.18; H, 1.29.
Cl, 24.25;
2.3. Physical measurements X-ray powder diffraction data were collected at the Institute of Low Temperature and Structure Research in Wroclaw on a computerized STADI P diffractometer combined with a Mera 79100 monitor, using Cu Ka, radiation. Unit cell parameters were obtained by least-squares refinement of 3 1 values for all observed reflections. The magnetic susceptibility was measured by the conventional Faraday method on a powdered sample sealed in a quartz tube at a field of 6 KOe and temperatures ranging from 4 to 300 K. The values were corrected for diamagnetic increments. The solid state absorption spectrum of the compound was recorded on a Cary-Varian 2300 spectrophotometer in the 4000-24 000 cm-’ range. In order to obtain the electronic spectrum a well ground mixture of the compound with some Halowax oil (chlorinated naphthalene, refraction index of 1.635) was placed between two quartz windows, pressed to get a transparent and uniform layer, and put into the cell compartment of the spectrophotometer. The IR spectra were recorded on Perkin-Elmer 180 and 789 spectrophotometers using hexachlorobutadiene and nujol mulls as well as KRr, CaF, and polyethylene plates.
161
3. Results and discussion 3.1. Characterization of the compound CsUCl,.4H,O precipitates from the solution in the form of brown-green, fine crystalline monoclinic crystals. The compound is not resistant to oxidation by air and may lose some of its water of crystallization at temperatures as low as 20 “C. As with almost all hydrated U(II1) halides and complex halides [3], the compound is easily soluble in a number of more polar organic solvents such as methanol, ethanol, formic acid, tributylphosphate and formamide. In water and aqueous acidic solutions it dissolves with oxidation to U(IV). The hydrate may be easily converted through thermal dehydration into the anhydrous salt by applying an TABLE Observed
1 and calculated
d spacings
hkl
4,
1 0 0 0 0 1 1 1 0
8.0040 7.0717 5.8676 5.7383 5.4632 4.7839 4.3345 4.2654 3.80 1 1 3.6169 3.4172 3.2436 3.1809 2.9249 2.8241 2.7263 2.6737 2.5916 2.5306 2.5068 2.4848 2.4438 2.3556 2.3359 2.2541 2.2190 2.1610 2.0854 2.0675 1.9485 1.8148
i 0 i 0 1 1 i i I 020 1 1 1 120 2 1 0 i 1 1 1 2 1 i 12 2 2 0 221 022 031 221 310 3 1 1 122 202 301 230 320 3 1 2 231 113 321 330 421
and observed
relative
intensities
for CsUCl,.4H20
III,, 7.9373 7.0189 5.8547 5.7373 5.4555 4.7847 4.3354 4.2539 3.8049 3.6086 3.4198 3.2416 3.1817 2.9274 2.8238 2.7278 2.6726 2.5943 2.5306 2.5072 2.4857 2.4409 2.3536 2.3364 2.2584 2.2217 2.1563 2.0886 2.0684 1.9516 1.8128
59.0 29.6 16.9 39.8 43.1 58.4 68.6 100.0 21.3 67.8 30.6 16.4 22.1 26.9 52.4 55.0 25.0 11.2 25.8 11.3 46.2 12.1 20.1 31.3 27.3 22.3 32.9 13.2 17.9 10.9 11.4
162
effective non-static high vacuum system. For this purpose the temperature was slowly and gradually increased from 20 to 400 “C at a vacuum of 10e5 to lo-” hPa. The anhydrous compound was first identified during investigations of the binary fused salt system CsCl-UCl, along with X-ray powder diffraction analysis (cubic, a = 9.16 A) [4]. Further investigations are in progress [5]. Analysis calculated for CsUCl,: Cs, 25.92; U, 46.42; Cl, 27.66. Found: Cs, 26.18; U, 46.21; Cl, 27.64. 3.2. X-ray powder di$raction analysis The observed and calculated d spacings together with the observed relative intensities for CsUC1,*4H,O are listed in Table 1. The data show that the compound crystallizes in the monoclinic system and possesses the following lattice parameters: a = 8.043 A, b= 8.671 A, c= 7.112 A, /3 = 99.28”, V= 489.48 A3, Z = 2, dca,c.= 3.97 g crnm3 and dpyk,= 4.15 g cmp3. Unfortunately, the space group could not be determined unambiguously and is either P2 or Pm. 3.3. IR spectra The IR and far-IR spectra of the compound are similar to those of the potassium, rubidium and ammonium tetrachlorouranate(II1) tetrahydrates [ 11. In the 1550-1650 and 2850-3600 cm-’ absorption regions strong and broad bands
1‘Yc; 2oc
150
1oc
50
/ / / /
0
50
I
I
I
I
100
150
200
250
*
TI'KI
Fig. 1. Inverse magnetic susceptibility of CsUC1,.4H,O
VS.temperature.
163
are observed, characteristic of the stretching and bending modes of coordinated water with maxima at 1607, 1630, 3190, 3335 and 3410 cm-‘. In the spectrum the typical bands may also be noted for the coordinated water multiplet at 400-700 cm-’ with components at 465,482,518,535,615 and 672 cm-’ which corresponds to the rocking and wagging modes [6]. As in the case of the potassium, rubidium and ammonium tetrahydrates, the Y(U-Cl) stretching vibration appears as a broad multiplet of strong intensity with well-resolved bands at 156, 166, 194 and 218 cm-‘. The S(Cl-U-Cl) bending mode appears at 132 cm-i. Some other bands observed in this range probably correspond to lattice modes. 3.4. Magnetic susceptibilities and electronic spectrum The inverse magnetic susceptibility vs. temperature plot exhibits the Curie-Weiss dependence xi = C/( T- f3) in the 180-300 K range with the paramagnetic constants j+, = 2.84 co.5= 3.27 B.M. and 19= 29 K. The derived effective magnetic moment is typical of U( III) compounds but is somewhat lower than those reported for the potassium, rubidium and ammonium tetrahydrates [ 11. At temperatures lower than 180 K the plot curves above the Curie-Weiss line approaching l/x h = 0 (Fig. 1). The unusual temperature dependence of the reciprocal magnetic susceptibility in this range may be understood in terms of crystal field effects. Such a magnetic behaviour of Kramer’s ion U3+ is expected when the CF ground state of the ion bears a much smaller magnetic moment than its first
5
10
15
20
25 cm-’ x lo-'
Fig. 2. Absorption
spectrum of CsUC1,.4H,O.
164
The solid state absorption spectrum of CsUCI,*4H,O (Fig. 2) is similar to those reported for UCl,*7H,O [7] and the aquo-ion [8, 93. Contrary to the earlier reported spectra of KUCl,*4H,O, RbUCl,*4H,O and NH,UCl,*4H,O [l], no strong 5f3-5f26d1 absorption bands in the 15000-21000 cm-’ range are observed. The appearance of such bands in the visible region has been attributed to an increase in covalency or reducing character of the ligands [lo]. In accordance with this statement, in the solid state absorption spectra of U(II1) chlorocomplexes, an essential red shift of the wavenumbers of the first strong f-d bands with decreasing U-Cl lengths and coordination numbers lower than nine may be noticed [3, lo]. Hence, we may expect the presence of the water molecules in the first coordination sphere of CsUCl,*4H,O and a coordination number larger than nine.
Acknowledgments The financial support of the Polish Academy of Sciences is gratefully acknowledged. The authors would like to thank Mr. J. Jariczak of the Institute.of Low Temperature and Structure Research in Wroclaw for determination of the X-ray powder diffraction values and Mr. E. Zych of the Institute of Chemistry of the Wroclaw University for technical assistance. References J. Less-Common Met., 32 (1988) 271. Inorg Chim. Actu, 32 (1979) L83. in A. J. Freeman and C. Keller (eds.), Handbook on the Physics and Chemistry of theActinides,Vol. 6, North-Holland Physics Publishing, Amsterdam, 1990. I. G. Suglobova and D. E. Chirkst, Sov. J. Coord. Chem., 7( 1981) 52. M. Karbowiak and J. Droidiyriski, J. Less-Common Met., to be published. C. Postmus and J. R. Ferraro, J. Chem. Phys., 48 (1968) 3428. J. Droidiynski, fnorg. Chim. Acta, 109 (1985) 79. W. T. Carnal1 and B. G. Wybourne, J. Chem. Phys., 40 (1964) 3428. J. DroidPyriski, J. Inorg. Nucl. Chem., 40 (1978) 319. J. Droidiyriski, in Rare Earth Spectroscopy, Proc. Rare Earth Spectroscopy Symp. RES-84, Wrocfaw, September IO-15,1985, World Scientific Publishing, Singapore, 1985, pp. 57-80.
1 J. Droidiyriski, 2 J. Droidiyriski, 3 J. Droidiytiski, 4 5 6 7 8 9
10