- Email: [email protected]
The preparation of praseodymium tetrafluoride
IHORG. HUCL.
CHEM.
LETTERS
Vol.
2,
pp.
13- 14,
1966.
Pergamon Press
Ltd.
Printed
In
Greet
Britain.
THE PREPARATION OF PRASEODYMIUM TETRAFLUORIDE J. Sortano, M. Givon and J. Shamir I s r a e l A t o m i c E n e r g y C o m m i s s i o n , Yavne, I s r a e l and D e p a r t m e n t of Inorganic and Analytical C h e m i s t r y , Hebrew University, J e r u s a l e m , I s r a e l PRASEODYMIUM IS KNOWN to exist in the t e t r a v a l e n t state in the c o m p l e x e s MxPrF4+x, w h e r e M+ d e s i g n a t e s an alkali m e t a l cation, and x = 2, 3 or 4.1 Until now, all a t t e m p t s to p r e p a r e the compound P r F 4 have failed, 2 and opposing views have been e x p r e s s e d on its possible e x i s t e n c e . 3, 4 In this paper an original method for the p r e p a r a t i o n of P r F 4 is d e s c r i b e d . F i r s t , the complex salt N a 2 P r F 6 was p r e p a r e d by f l u o r i n a t i o n of Na2PrC15. The salt obtained was analyzed a c c o r d i n g to the m e t h o d of A s p r e y and Keenan, 1 and also by m e l t i n g together with solid p o t a s s i u m iodide (in o r d e r to avoid p o s s i b l e r e d u c t i o n by water) and t i t r a t i n g the l i b e r a t e d iodide.
Both m e t h o d s
showed that all the p r a s e o d y m i u m in the complex salt was in the t e t r a v a l e n t state.
The compound was then placed on top of a p o r o u s Teflon disc in a nickel
v e s s e l , which was then closed in a dry-box. a l l - m e t a l v a c u u m line and evacuated.
The v e s s e l was connected to an
Anhydrous hydrogen fluoride was d i s t i l -
led upon the compound, and f o r c e d ~ h r o u g h the f i l t e r with d r y helium.
This
o p e r a t i o n was r e p e a t e d s e v e r a l t i m e s . The liquid hydrogen fluoride d e c o m p o s e d the complex a c c o r d i n g to the reaction: Na2PrF6(s)
+ 2HF (1)
2NaHF 2 (soln) + P r F 4 (s)
The s o d i u m bifluoride d i s s o l v e d in the e x c e s s hydrogen fluoride and p a s s e d through the filter, w h e r e a s the p r a s e o d y m i u m t e t r a f l u o r t d e r e m a i n e d on the filter.
The solvent hydrogen fluoride was r e m o v e d f r o m the filtrate by d i s -
tillation and a white r e s i d u e r e m a i n e d .
Both r e s i d u e s w e r e analyzed for s o d i u m and p r a s e o d y m i u m and the 13
(1)
14
Prla4
Vol. 2, Ho. I
oxidizing power of the r e s i d u e on the f i l t e r was d e t e r m i n e d .
The r e s i d u e of the
filtrate was found to contain sodium but no p r a s e o d y m i u m , while that on the f i l t e r contained p r a s e o d y m i u m and only t r a c e s of sodium.
The oxidizing power
c o r r e s p o n d e d to about 40 p e r cent of that expected for P r F 4. p r a s e o d y m i u m ratio was found to be 3.4:1.
The fluorine to
Both f i g u r e s show that the r e s i d u e
on the f i l t e r was a m i x t u r e c o n s i s t i n g of 40 p e r cent P r F 4 and 60 p e r cent P r F 3. It is believed that the P r F 4 initially f o r m e d by r e a c t i o n (1) subsequently p a r t l y d e c o m p o s e d , due to its low stability, and p a r t l y was r e d u c e d by hydrogen p r e s e n t in the hydrogen fluoride, probably due to attack of the m e t a l v a c u u m line by the hydrogen fluoride. A p a r t of the p r o d u c t was d i s s o l v e d in s a t u r a t e d aqueous c e s i u m fluoride, and the a b s o r p t i o n s p e c t r u m was d e t e r m i n e d .
In addition to the p r a s e o d y m i u m
(HI) peaks, a peak at 320 rnu and an u n r e s o l v e d peak at about 250 mu (over a background due to light s c a t t e r i n g f r o m suspended p a r t i c l e s ) w e r e o b s e r v e d . The peak at 320 n ~ has been a s s i g n e d to p r a s e o d y m i u m (IV). 5
In o r d e r to obtain a higher yield of p r a s e o d y m i u m t e t r a f l u o r i d e and a p u r e r product, which can be fully c h a r a c t e r i z e d , an a l l - K E L - F a p p a r a t u s will be e m p l o y e d in f u r t h e r work which is in p r o g r e s s . A c k n o w l e d g e m e n t - - T h e help of Dr. R. Rafaeloff for c a r r y i n g out the a n a l y s i s is acknowledged. References 1. ASPREY L . B . and KEENAN T . K . , J. Inor$. Nucl. Chem. 16, 260 (1961). 2. PERROS T. and NAESER C . R . , J. A m e r . Chem. Soc. 74, 1357 (1952). 3. PERROS T . P . ,
(1953).
MUNSON T . R . and NAESER C., J. Chem. Educ. 30, 402
4. CUNNINGHAM B. B., FEAY P. C. and MOLLIER M. A . , J. A m e r . Chem. Soc. 76, 3361 (1954).
5. PAJAKOFF S . W . , Monatsh 94, 482 (1963).
CHEM.
LETTERS
Vol.
2,
pp.
13- 14,
1966.
Pergamon Press
Ltd.
Printed
In
Greet
Britain.
THE PREPARATION OF PRASEODYMIUM TETRAFLUORIDE J. Sortano, M. Givon and J. Shamir I s r a e l A t o m i c E n e r g y C o m m i s s i o n , Yavne, I s r a e l and D e p a r t m e n t of Inorganic and Analytical C h e m i s t r y , Hebrew University, J e r u s a l e m , I s r a e l PRASEODYMIUM IS KNOWN to exist in the t e t r a v a l e n t state in the c o m p l e x e s MxPrF4+x, w h e r e M+ d e s i g n a t e s an alkali m e t a l cation, and x = 2, 3 or 4.1 Until now, all a t t e m p t s to p r e p a r e the compound P r F 4 have failed, 2 and opposing views have been e x p r e s s e d on its possible e x i s t e n c e . 3, 4 In this paper an original method for the p r e p a r a t i o n of P r F 4 is d e s c r i b e d . F i r s t , the complex salt N a 2 P r F 6 was p r e p a r e d by f l u o r i n a t i o n of Na2PrC15. The salt obtained was analyzed a c c o r d i n g to the m e t h o d of A s p r e y and Keenan, 1 and also by m e l t i n g together with solid p o t a s s i u m iodide (in o r d e r to avoid p o s s i b l e r e d u c t i o n by water) and t i t r a t i n g the l i b e r a t e d iodide.
Both m e t h o d s
showed that all the p r a s e o d y m i u m in the complex salt was in the t e t r a v a l e n t state.
The compound was then placed on top of a p o r o u s Teflon disc in a nickel
v e s s e l , which was then closed in a dry-box. a l l - m e t a l v a c u u m line and evacuated.
The v e s s e l was connected to an
Anhydrous hydrogen fluoride was d i s t i l -
led upon the compound, and f o r c e d ~ h r o u g h the f i l t e r with d r y helium.
This
o p e r a t i o n was r e p e a t e d s e v e r a l t i m e s . The liquid hydrogen fluoride d e c o m p o s e d the complex a c c o r d i n g to the reaction: Na2PrF6(s)
+ 2HF (1)
2NaHF 2 (soln) + P r F 4 (s)
The s o d i u m bifluoride d i s s o l v e d in the e x c e s s hydrogen fluoride and p a s s e d through the filter, w h e r e a s the p r a s e o d y m i u m t e t r a f l u o r t d e r e m a i n e d on the filter.
The solvent hydrogen fluoride was r e m o v e d f r o m the filtrate by d i s -
tillation and a white r e s i d u e r e m a i n e d .
Both r e s i d u e s w e r e analyzed for s o d i u m and p r a s e o d y m i u m and the 13
(1)
14
Prla4
Vol. 2, Ho. I
oxidizing power of the r e s i d u e on the f i l t e r was d e t e r m i n e d .
The r e s i d u e of the
filtrate was found to contain sodium but no p r a s e o d y m i u m , while that on the f i l t e r contained p r a s e o d y m i u m and only t r a c e s of sodium.
The oxidizing power
c o r r e s p o n d e d to about 40 p e r cent of that expected for P r F 4. p r a s e o d y m i u m ratio was found to be 3.4:1.
The fluorine to
Both f i g u r e s show that the r e s i d u e
on the f i l t e r was a m i x t u r e c o n s i s t i n g of 40 p e r cent P r F 4 and 60 p e r cent P r F 3. It is believed that the P r F 4 initially f o r m e d by r e a c t i o n (1) subsequently p a r t l y d e c o m p o s e d , due to its low stability, and p a r t l y was r e d u c e d by hydrogen p r e s e n t in the hydrogen fluoride, probably due to attack of the m e t a l v a c u u m line by the hydrogen fluoride. A p a r t of the p r o d u c t was d i s s o l v e d in s a t u r a t e d aqueous c e s i u m fluoride, and the a b s o r p t i o n s p e c t r u m was d e t e r m i n e d .
In addition to the p r a s e o d y m i u m
(HI) peaks, a peak at 320 rnu and an u n r e s o l v e d peak at about 250 mu (over a background due to light s c a t t e r i n g f r o m suspended p a r t i c l e s ) w e r e o b s e r v e d . The peak at 320 n ~ has been a s s i g n e d to p r a s e o d y m i u m (IV). 5
In o r d e r to obtain a higher yield of p r a s e o d y m i u m t e t r a f l u o r i d e and a p u r e r product, which can be fully c h a r a c t e r i z e d , an a l l - K E L - F a p p a r a t u s will be e m p l o y e d in f u r t h e r work which is in p r o g r e s s . A c k n o w l e d g e m e n t - - T h e help of Dr. R. Rafaeloff for c a r r y i n g out the a n a l y s i s is acknowledged. References 1. ASPREY L . B . and KEENAN T . K . , J. Inor$. Nucl. Chem. 16, 260 (1961). 2. PERROS T. and NAESER C . R . , J. A m e r . Chem. Soc. 74, 1357 (1952). 3. PERROS T . P . ,
(1953).
MUNSON T . R . and NAESER C., J. Chem. Educ. 30, 402
4. CUNNINGHAM B. B., FEAY P. C. and MOLLIER M. A . , J. A m e r . Chem. Soc. 76, 3361 (1954).
5. PAJAKOFF S . W . , Monatsh 94, 482 (1963).