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Solvates of uranium tetrachloride with phosphorus oxychloride
J. lnorg. Nucl. Chem., 19(30,Vol. 15, pp. 67 to 70. PergamonPress Ltd.
SOLVATES OF U R A N I U M TETRACHLORIDE WITH PHOSPHORUS OXYCHLORIDE* R. E. PANZER** a n d J. F. SU'ITLE~ (Received 2 November 1959)
Abstract--Two compounds of uranium tetrachloride and phosphorus oxychloride, the solvates, UCI4"4POCIa and UClcPOCIs are reported. The tetra-solvate is an aqua-green tetragonal crystalline material with indices of refraction of ne = 1"645, no = 1.657. The material melts at 340°C (closed tube), following partial liquefaction and resolidilicatiun at 118°C. The mono-solvate UCI,-POCI3 was prepared from the tetra-solvate by gentle heating under high vacuum. This material is light blue-green. Its symmetry class is unknown. Indices of refraction are: maximum index 1-660, minimum index: 1.645. It occurs in irregularly shaped crystals. Powder X-ray data are reported for these two compounds. The possible existence of other solvates in the series is discussed. WHILE c o n d u c t i n g electrolytic e x p e r i m e n t s i n p h o s p h o r u s o x y c h l o r i d e , P O C I a, CADY a n d TAFT d i s c o v e r e d t h a t s o l u t i o n o f v a r i o u s halides i n this s o l v e n t r e s u l t e d i n a v a r i e t y o f crystalline a n d g e l a t i n o u s c o m p o u n d s , tl~ P h o s p h o r u s o x y c h l o r i d e has r e c e n t l y b e e n utilized i n v a r i o u s m e t a t h e t i c a l r e a c t i o n s , solvate p r e p a r a t i o n a n d i n studies o f a c i d - b a s e p r o p e r t i e s i n n o n - a q u e o u s solvents, cz-5~ T h e c o m p o u n d s 3ZrC14.2POC1 a a n d 3HfCI4-2POCI s h a v e b e e n u s e d to effect a n efficient s e p a r a t i o n o f z i r c o n i u m a n d h a f n i u m via f r a c t i o n a l distillation, te~ T y p i c a l solvates o f p h o s p h o r u s o x y c h l o r i d e k n o w n t o f o r m are GaCIa-POC1 s, A1CIa'POCI a, TiCI4-2POC1 a, TeCI4.POC! a a n d A1SbCls'3POCIa37) EXPERIMENTAL Because of the hygroscopic nature of the complex uranium chlorides, prepared samples were transferred from weighing bottles into 100 ml volumetric flasks in a dry-box. The samples were then dissolved in 5 N nitric acid cooled to --10°C. This procedure prevented loss of hydrogen chloride. After solution was complete the uranium was oxidized to the uranyl state by gentle heating or through the addition of a few drops of 3 per cent hydrogen peroxide. The solution was then diluted to the mark and aliquot portions of the solution taken as required for the analyses. Methods o f analysis Uranium. Uranium was weighed as the ignited uranyl pyrophosphatc following its precipitation as uranyi phosphate ~*~in a solution buffered at pH 5 with ammonium acetate.
* Taken in part from a dissertation submitted by R. E. PANZERto the Graduate School of the University of New Mexico in partial fulfillmentof the requirements for the degree of Doctor of Philosophy in Chemistry. ** Present address: U.S. Naval Ordnance Laboratory, Corona, California. ~; Present address: Lawrence Radiation Laboratory, University of California, Berkeley, California. tl~ H. P. CADYand R. TAFT,,L Phys. Chem. 19, 1065 (1925). tz~ V. GUTMANN,Ostereiehische Chem. Z. 56, 126 (1955). ~s~V. GUT~L~7~q~,J. Phys. Chem. 63, 378 0959). ~4~j. C. SHELDONand S. Y. TVRE~,JR., d. Amer. Chem. Soc. 81, 2290 (1959). ~sj N. N. GREENWOODand K. WADE, J. lnorg. Nucl. Chem. 3, 249 (1957). ¢6~D. M. GRtm~ and J. S. KATZ,J. Amer. Chem. Soc. 71, 3843 (1949). tT~j. R. VANWAZFAZ,Phosphorus and its Compounds Vol. l, Chemistry. Interscience, New York 0958). ~s~ C. J. RODDEN (Editor-in-Chief), Analytical Chemistry o f the Manhattan Project, NNES, Plutonium Project Record, Div. VIII, Vol. I. McGraw-Hill, N e w Y o r k (1950). 67
68
R . E . PANZERAND J. F. Strrrt~
Phosphorus. Determined by precipitation as ammonium phosphomolybdate which was filtered, washed and ignited at 425~C to the weighing form, phospho-molybdic anhydride, PtOs.24MoOsJ 'j Chloride. Determined by the usual gravimetric method of precipitation from nitric acid solution with silver nitrate, c~°~ X-ray methods. Powder X-ray photographs were obtained using Cu-K~ radiation. The camera had a radius of 57.3 mm, film was Eastman Kodak No-screen type mounted by the Straumanis method. Exposure times were as noted with the data from each sample. The X-ray data have been deposited with the A.S.T.M. X-ray Powder Data File, Pennsylvania State University, University Park, Pa., U.S.A. Optical hwesti~ations Optical crystallographic investigations were made using a polarizing microscope. Indices of refraction of the crystals were determined on the microscope stage by the immersion method. It was found that by working rapidly the indices could be determined before the compounds reacted with the index media. In addition, it was discovered that the compounds do not rapidly react with the high-index-range media. For general study a mineral oil SUSl~ension of the crystals on a glass slide was covered with a thin cover glass; it was thus possible to maintain the crystals unchanged for an hour or m6re. Purification of phosphorus oxychloride This solvent was purified by distilling through a seven stage bubble column at least three times before use. The first fraction containing most of the hydrogen chloride was discarded. Finally, the solvent was distilled directly into the vessel, (previously flame dried under vacuum), in* which it was to be used. Preparation of uranium tetrachloride This compound was prepared by the method of HERMANNand StrrrLE~H~. RESULTS
The solvate, UCI4"4POCI 8 During investigations o f the c o m p o u n d , U C l d P C I s , solutions o f UCI 4 in POCI 3 were prepared for use in studies o f the absorption spectra o f U e l 4, U C I 6 and UC1 e dissolved in p h o s p h o r u s oxychloride. ~lz) U r a n i u m tetrachloride dissolved in POCl 3 with subsequent appearance o f a pale green precipitate. This material was f o u n d to be a solvate o f u r a n i u m tetrachloride with p h o s p h o r u s oxychloride. T h e formula is UCI4.4POC! v ( F o u n d : U, 23.6; CI, 57.3; P, 12.2. Calc. U, 24.0; CI, 56.8; P, 12.4~). The molecular weight was not determined because no cryoscopic m e d i u m was found in which the c o m p o u n d was sufficiently soluble without ionization or reaction with the solvent. W h e n heated in a sealed tube the material appeared to partially liquefy at 118°C with a drop o f liquid appearing at the top o f the tube. The sample lightened in colour with further heating and melted at 340°C to a light green liquid. A n optical crystallographic investigation gave the following data. The c o m p o u n d is light green in plane polarized light; interference colours are first order greys to first order yellows; birefringence is low, the elongated crystals being length fast; extinction is parallel to the zone o f elongation. i,~ I. M. KOLTHOFFand E. B. SANDELL,Textbook of Quantitative Inorganic Analysis (3rd Ed.). Macmillan, New York (1952). cto)N. H. FURMAN(Editor), Scott's Standard Methods of Chemical Analysis Vol. 1. Van Nostrand, Princeton (1948). t11~j. A. HERMANNand J. F. SUTTLE,Inorganic Synthesis (Editor-in-chief T. MOELLER),VOI. 5, p. 143. McGraw-Hill, New York (1957). tx.~ R. E. PANZER,Doctoral dissertation, University of New Mexico (1958).
Solvates of uranium tetrachtoride with phosphorus oxychloride
69
Indices of refraction: n e ----- 1.645 (fast direction); n o = 1.657 (slow direction); birel¥ingence = 0.012. The crystals are uniaxial and the optical sign is negative. The existence of interference figures, together with the values of sin 2 0 which occur in multiples of 0.0080 for the first five lines in the X-ray powder pattern, indicate that the solvate compound is tetragonal. However, the occurrence of an isometric material sometimes mixed with the tetragonal crystals has created an ambiguity in the complete interpretation of the X-ray data. It is expected that further investigations of this solvate system will clarify the situation.
The solvate, UCI4.POCI 3 When the tetra-solvated compound described above was heated to 50°C under a pressure of 0-5 # another solvate formed which had the composition, UCI4-POCI a. It was light blue in colour. Analysis of this compound was as follows. (Found: U, 44"8; C1,45"6; P, 6-17. Calc. U, 44.6; CI, 46.5; P, 5.82% ). When this solvate was heated in a sealed tube the following phenomena were observed. At 280°C the sample darkened in colour and appeared to shrink; it melted at 340°C to a green liquid which became light green on cooling. This solid, investigated under a polarizing microscope was found to be isotropic and light yellow green in plane polarized light. It is thus isometric crystalline or amorphous. Optical data were obtained on the solvate, UCI~.POCI 3. It is pale bluish green in plane polarized light; interference colours are first-order greys to first order yellows; extinction is wavy and not complete for the entire crystal. No optical sign was determinable because no optical figure could be observed. Most of the crystals were irregularly shaped, though some were tabular. Indices of refraction: maximum i n d e x 1.660; minimum index : 1.645; birefringence -- 0"025. The symmetry class of the crystals is unknown. The method of preparation of the mono-solvated uranium tetrachloride, i.e., heating the tetra-solvated uranium tetrachloride to remove three molecules of phosphorus oxychloride is not conducive to the formation of well-defined crystals. In some batches of these solvates a different material was observed under the microscope, intermixed with the solvates reported here. This material is isotropic in plane polarized light and appeared to be isometric crystalline. It appears that there are other solvates in this system in addition to the two which have been characterized. DISCUSSION GUTMANN (la) has stated that so far no known compound solvated with phosphorus oxychloride has more than three molecules of the solvent attached to it. In explanation he advances the theory that the high molar volume of phosphorus oxychloride, 97-5 cm 3, prevents close co-ordination of more than three molecul.es of that solvent. The compound, UCI4-4POC13 is the first phosphorus oxychloride solvate reported in which four molecules of the solvent are attached to one of the solute. The.large coordination sphere of uranium apparently allows close approach of the four solvate molecules to the extent that they are readily co-ordinated. ~13~ V. GUTMANN, Ostereichische Chem. Z. 56, 128 (1955).
70
R.E. PANZF.J~ANDJ. F. SUTTLE
Ln,a~QU]ST and BRANDENhave determined that the co-ordination of solvent molecules may also take place through the oxygen atom, i.e., ClsPOSbCI~. ~14) Further investigations of the system UCI4-POCIs should be conducted to elaborate all the solvates existing in this system. The structures of these may also be found to involve co-ordination through the oxygen, atom. Acknowledgements--Our thanks are extended to Mr. F. C. H o ~ ,
who provided the optical investigations. Dr. A. ROSENZW~Gaided in the X-ray investigations. This research was carried out under a contract between the Los Alamos Scientific Laboratory and the University of New Mexico. The financial aid received by one of us, (R. E. P.) is gratefully acknowledged. c14~I. LINDQInSTand C. E. BRAND,N,Acta Chem. Scand. 12, 134 (1958).
SOLVATES OF U R A N I U M TETRACHLORIDE WITH PHOSPHORUS OXYCHLORIDE* R. E. PANZER** a n d J. F. SU'ITLE~ (Received 2 November 1959)
Abstract--Two compounds of uranium tetrachloride and phosphorus oxychloride, the solvates, UCI4"4POCIa and UClcPOCIs are reported. The tetra-solvate is an aqua-green tetragonal crystalline material with indices of refraction of ne = 1"645, no = 1.657. The material melts at 340°C (closed tube), following partial liquefaction and resolidilicatiun at 118°C. The mono-solvate UCI,-POCI3 was prepared from the tetra-solvate by gentle heating under high vacuum. This material is light blue-green. Its symmetry class is unknown. Indices of refraction are: maximum index 1-660, minimum index: 1.645. It occurs in irregularly shaped crystals. Powder X-ray data are reported for these two compounds. The possible existence of other solvates in the series is discussed. WHILE c o n d u c t i n g electrolytic e x p e r i m e n t s i n p h o s p h o r u s o x y c h l o r i d e , P O C I a, CADY a n d TAFT d i s c o v e r e d t h a t s o l u t i o n o f v a r i o u s halides i n this s o l v e n t r e s u l t e d i n a v a r i e t y o f crystalline a n d g e l a t i n o u s c o m p o u n d s , tl~ P h o s p h o r u s o x y c h l o r i d e has r e c e n t l y b e e n utilized i n v a r i o u s m e t a t h e t i c a l r e a c t i o n s , solvate p r e p a r a t i o n a n d i n studies o f a c i d - b a s e p r o p e r t i e s i n n o n - a q u e o u s solvents, cz-5~ T h e c o m p o u n d s 3ZrC14.2POC1 a a n d 3HfCI4-2POCI s h a v e b e e n u s e d to effect a n efficient s e p a r a t i o n o f z i r c o n i u m a n d h a f n i u m via f r a c t i o n a l distillation, te~ T y p i c a l solvates o f p h o s p h o r u s o x y c h l o r i d e k n o w n t o f o r m are GaCIa-POC1 s, A1CIa'POCI a, TiCI4-2POC1 a, TeCI4.POC! a a n d A1SbCls'3POCIa37) EXPERIMENTAL Because of the hygroscopic nature of the complex uranium chlorides, prepared samples were transferred from weighing bottles into 100 ml volumetric flasks in a dry-box. The samples were then dissolved in 5 N nitric acid cooled to --10°C. This procedure prevented loss of hydrogen chloride. After solution was complete the uranium was oxidized to the uranyl state by gentle heating or through the addition of a few drops of 3 per cent hydrogen peroxide. The solution was then diluted to the mark and aliquot portions of the solution taken as required for the analyses. Methods o f analysis Uranium. Uranium was weighed as the ignited uranyl pyrophosphatc following its precipitation as uranyi phosphate ~*~in a solution buffered at pH 5 with ammonium acetate.
* Taken in part from a dissertation submitted by R. E. PANZERto the Graduate School of the University of New Mexico in partial fulfillmentof the requirements for the degree of Doctor of Philosophy in Chemistry. ** Present address: U.S. Naval Ordnance Laboratory, Corona, California. ~; Present address: Lawrence Radiation Laboratory, University of California, Berkeley, California. tl~ H. P. CADYand R. TAFT,,L Phys. Chem. 19, 1065 (1925). tz~ V. GUTMANN,Ostereiehische Chem. Z. 56, 126 (1955). ~s~V. GUT~L~7~q~,J. Phys. Chem. 63, 378 0959). ~4~j. C. SHELDONand S. Y. TVRE~,JR., d. Amer. Chem. Soc. 81, 2290 (1959). ~sj N. N. GREENWOODand K. WADE, J. lnorg. Nucl. Chem. 3, 249 (1957). ¢6~D. M. GRtm~ and J. S. KATZ,J. Amer. Chem. Soc. 71, 3843 (1949). tT~j. R. VANWAZFAZ,Phosphorus and its Compounds Vol. l, Chemistry. Interscience, New York 0958). ~s~ C. J. RODDEN (Editor-in-Chief), Analytical Chemistry o f the Manhattan Project, NNES, Plutonium Project Record, Div. VIII, Vol. I. McGraw-Hill, N e w Y o r k (1950). 67
68
R . E . PANZERAND J. F. Strrrt~
Phosphorus. Determined by precipitation as ammonium phosphomolybdate which was filtered, washed and ignited at 425~C to the weighing form, phospho-molybdic anhydride, PtOs.24MoOsJ 'j Chloride. Determined by the usual gravimetric method of precipitation from nitric acid solution with silver nitrate, c~°~ X-ray methods. Powder X-ray photographs were obtained using Cu-K~ radiation. The camera had a radius of 57.3 mm, film was Eastman Kodak No-screen type mounted by the Straumanis method. Exposure times were as noted with the data from each sample. The X-ray data have been deposited with the A.S.T.M. X-ray Powder Data File, Pennsylvania State University, University Park, Pa., U.S.A. Optical hwesti~ations Optical crystallographic investigations were made using a polarizing microscope. Indices of refraction of the crystals were determined on the microscope stage by the immersion method. It was found that by working rapidly the indices could be determined before the compounds reacted with the index media. In addition, it was discovered that the compounds do not rapidly react with the high-index-range media. For general study a mineral oil SUSl~ension of the crystals on a glass slide was covered with a thin cover glass; it was thus possible to maintain the crystals unchanged for an hour or m6re. Purification of phosphorus oxychloride This solvent was purified by distilling through a seven stage bubble column at least three times before use. The first fraction containing most of the hydrogen chloride was discarded. Finally, the solvent was distilled directly into the vessel, (previously flame dried under vacuum), in* which it was to be used. Preparation of uranium tetrachloride This compound was prepared by the method of HERMANNand StrrrLE~H~. RESULTS
The solvate, UCI4"4POCI 8 During investigations o f the c o m p o u n d , U C l d P C I s , solutions o f UCI 4 in POCI 3 were prepared for use in studies o f the absorption spectra o f U e l 4, U C I 6 and UC1 e dissolved in p h o s p h o r u s oxychloride. ~lz) U r a n i u m tetrachloride dissolved in POCl 3 with subsequent appearance o f a pale green precipitate. This material was f o u n d to be a solvate o f u r a n i u m tetrachloride with p h o s p h o r u s oxychloride. T h e formula is UCI4.4POC! v ( F o u n d : U, 23.6; CI, 57.3; P, 12.2. Calc. U, 24.0; CI, 56.8; P, 12.4~). The molecular weight was not determined because no cryoscopic m e d i u m was found in which the c o m p o u n d was sufficiently soluble without ionization or reaction with the solvent. W h e n heated in a sealed tube the material appeared to partially liquefy at 118°C with a drop o f liquid appearing at the top o f the tube. The sample lightened in colour with further heating and melted at 340°C to a light green liquid. A n optical crystallographic investigation gave the following data. The c o m p o u n d is light green in plane polarized light; interference colours are first order greys to first order yellows; birefringence is low, the elongated crystals being length fast; extinction is parallel to the zone o f elongation. i,~ I. M. KOLTHOFFand E. B. SANDELL,Textbook of Quantitative Inorganic Analysis (3rd Ed.). Macmillan, New York (1952). cto)N. H. FURMAN(Editor), Scott's Standard Methods of Chemical Analysis Vol. 1. Van Nostrand, Princeton (1948). t11~j. A. HERMANNand J. F. SUTTLE,Inorganic Synthesis (Editor-in-chief T. MOELLER),VOI. 5, p. 143. McGraw-Hill, New York (1957). tx.~ R. E. PANZER,Doctoral dissertation, University of New Mexico (1958).
Solvates of uranium tetrachtoride with phosphorus oxychloride
69
Indices of refraction: n e ----- 1.645 (fast direction); n o = 1.657 (slow direction); birel¥ingence = 0.012. The crystals are uniaxial and the optical sign is negative. The existence of interference figures, together with the values of sin 2 0 which occur in multiples of 0.0080 for the first five lines in the X-ray powder pattern, indicate that the solvate compound is tetragonal. However, the occurrence of an isometric material sometimes mixed with the tetragonal crystals has created an ambiguity in the complete interpretation of the X-ray data. It is expected that further investigations of this solvate system will clarify the situation.
The solvate, UCI4.POCI 3 When the tetra-solvated compound described above was heated to 50°C under a pressure of 0-5 # another solvate formed which had the composition, UCI4-POCI a. It was light blue in colour. Analysis of this compound was as follows. (Found: U, 44"8; C1,45"6; P, 6-17. Calc. U, 44.6; CI, 46.5; P, 5.82% ). When this solvate was heated in a sealed tube the following phenomena were observed. At 280°C the sample darkened in colour and appeared to shrink; it melted at 340°C to a green liquid which became light green on cooling. This solid, investigated under a polarizing microscope was found to be isotropic and light yellow green in plane polarized light. It is thus isometric crystalline or amorphous. Optical data were obtained on the solvate, UCI~.POCI 3. It is pale bluish green in plane polarized light; interference colours are first-order greys to first order yellows; extinction is wavy and not complete for the entire crystal. No optical sign was determinable because no optical figure could be observed. Most of the crystals were irregularly shaped, though some were tabular. Indices of refraction: maximum i n d e x 1.660; minimum index : 1.645; birefringence -- 0"025. The symmetry class of the crystals is unknown. The method of preparation of the mono-solvated uranium tetrachloride, i.e., heating the tetra-solvated uranium tetrachloride to remove three molecules of phosphorus oxychloride is not conducive to the formation of well-defined crystals. In some batches of these solvates a different material was observed under the microscope, intermixed with the solvates reported here. This material is isotropic in plane polarized light and appeared to be isometric crystalline. It appears that there are other solvates in this system in addition to the two which have been characterized. DISCUSSION GUTMANN (la) has stated that so far no known compound solvated with phosphorus oxychloride has more than three molecules of the solvent attached to it. In explanation he advances the theory that the high molar volume of phosphorus oxychloride, 97-5 cm 3, prevents close co-ordination of more than three molecul.es of that solvent. The compound, UCI4-4POC13 is the first phosphorus oxychloride solvate reported in which four molecules of the solvent are attached to one of the solute. The.large coordination sphere of uranium apparently allows close approach of the four solvate molecules to the extent that they are readily co-ordinated. ~13~ V. GUTMANN, Ostereichische Chem. Z. 56, 128 (1955).
70
R.E. PANZF.J~ANDJ. F. SUTTLE
Ln,a~QU]ST and BRANDENhave determined that the co-ordination of solvent molecules may also take place through the oxygen atom, i.e., ClsPOSbCI~. ~14) Further investigations of the system UCI4-POCIs should be conducted to elaborate all the solvates existing in this system. The structures of these may also be found to involve co-ordination through the oxygen, atom. Acknowledgements--Our thanks are extended to Mr. F. C. H o ~ ,
who provided the optical investigations. Dr. A. ROSENZW~Gaided in the X-ray investigations. This research was carried out under a contract between the Los Alamos Scientific Laboratory and the University of New Mexico. The financial aid received by one of us, (R. E. P.) is gratefully acknowledged. c14~I. LINDQInSTand C. E. BRAND,N,Acta Chem. Scand. 12, 134 (1958).