Actinide Chemistry

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Complexes Protactinium to Curium

ROBERT A. PENNEMAN, THOMAS Κ. KEENAN, and LARNED B. ASPREY University of California, Los Alamos Scientific Laboratory, Los Alamos, Ν. M. X-ray data are given for tetragonal LiF · XF and for rhombohedral 7NaF · 6XF, X = Th, Pa, U, Np, Pu, Am, and Cm. Hydrogen reduction of alkali fluoride-Pa(V) fluoride complexes yields LiF · PaF and 7MF · 6PaF (where M = Νa, Κ, Rb). When 3NaF · PaF is treated with H at 450°C., its absorption spectrum shows Pa(IV) to be present but its x-ray structure is not changed. Pentavalent compounds in clude MF · PaF , MF · UF (M = Li through Cs), as well as CsF · NpF , CsF · PuF , 2RbF · NpF , 2RbF · PuF , and 3RbF · PaF . Fluorination of UF in liquid anhydrous HF yields UF . When alkali fluoride and UF are present in liquid HF, fluorination forms blue, soluble UF -. Fluorine oxidation of NpF in a melt of CsF · 2HF yields magenta colored NpF -. 4

4

4

4

5

5

2

5

5

5

5

5

5

4

5

4

6

4

6

T n this p a p e r emphasis is g i v e n to recent results o b t a i n e d at t h e L o s A

A l a m o s Scientific L a b o r a t o r y rather t h a n to a c o m p l e t e survey.

Ref

erences to t h e c u r r e n t l i t e r a t u r e w i l l g i v e some i d e a of t h e scope of s u c h work.

Tetravalent Actinide Fluoride Complexes Complexes of

Protactinium ( I V ) .

PREPARATION A N DX - R A Y

PROPER

T I E S . A n u m b e r of c o m p l e x fluorides c o n t a i n i n g other tetravalent actinides are k n o w n (1, 8, 9, 13-15,

20, 22, 24, 25, 26, 27, 29),

but few

248 Fields and Moeller; Lanthanide/Actinide Chemistry Advances in Chemistry; American Chemical Society: Washington, DC, 1967.

fluoride

18.

Actinide

PENNEMAN ET AL.

compounds

Fluoride

249

Complexes

of P a ( I V ) h a v e b e e n described—e.g., the p r e l i m i n a r y c o m

munications on 7 R b F · 6 P a F of t h e c o m p l e x

fluorides

(3)

4

and 4 N H F 4

are w r i t t e n M F · X F

4

· PaF

(4).

4

or M F · X F

(Formulas 5

for ease of

d i s p l a y i n g the v a l e n c e of the a c t i n i d e . ) O u r p r e v i o u s w o r k o n 4 N H and 4 N H F · A m F 4

( I , 8, 22)

4

N a t i o n a l L a b o r a t o r y (9, 13, 14, 15, 24, 25, 26, 27) (29)

on compounds

4

·UF

4

p l u s the extensive w o r k at the O a k R i d g e

i n the a l k a l i

and b y Zachariasen

fluoride-uranium

p r o v i d e d x - r a y d a t a for the U ( I V )

fluoride

tetrafluoride systems

complexes.

I n most

cases,

the x - r a y properties of the P a ( I V ) c o m p o u n d s are s i m i l a r to those of t h e i r U(IV)

analogs.

Table I. Ratio MF:PaF,

A l k a l i Fluoride Complexes of Tetravalent Protactinium

M

t

Lattice Parameter,

Structure

Li Tetragonal Na Rhombohedral Κ Rhombohedral Rb Rhombohedral Cs (Unknown) All unknown Na Prob. tetragonal

1:1 7:6

a α α α

a

Q

b

6

5

2:1 3:1

ο ο ο

= = = =

A

14.96, c = 6.58 9.16, =107°54' 9.44,α=107°09' 9.64,α=107°0' Q

α

0

4:1

Κ

Prob. fee

Rb

Prob. fee

NH

4

Existence inferred from absorption spec trum, amount P a ( I V ) and of P a ( V ) unknown/ Existence inferred from absorption spec trum, amount P a ( I V ) and of P a ( V ) unknown/ Existence inferred from absorption spec trum, amount P a ( I V ) and of P a ( V ) unknown/ Isostructural w i t h ( N H ) X F ( X = U , N p , P u , and A m )

Monoclinic

4

4

8

° Isostructural with L i F · U F (13, 14). Isostructural with 7NaF · 6 U F (13, 15). Hydrogen reduction of 2 K F · P a F powder resulted in the formation of 7 K F · 6 P a F as the major solid phase, and not 2 K F · P a F . T h e x-ray structures of the 1:1 alkali fluoride : PaFs fluoride complexes are quite distinct from those of the 1:1 and 7:6 alkali fluoride:PaF complexes. At the 3:1 stoichiometry, the 3 K F · U F , 3 K F · U F , and 3 K F · U F compounds are all facecentered cubic and of nearly identical cell size (28). Absorption spectrum rather than x-ray was the criterion used to detect hydrogen reduction of 3 K F · P a F to 3 K F · P a F , and of 3NaF · P a F to 3NaF · P a F . 4

b

4

c

5

4

4

d

4

3

4

5

5

4

5

Complex fluorides

fluorides

4

c o n t a i n i n g tetravalent p r o t a c t i n i u m a n d the a l k a l i

( L i , N a , K , R b , a n d N H ) w e r e p r e p a r e d f r o m M F -f4

starting mixtures a n d b y reducing M F - P a F , compounds r

PaF

4

at 4 0 0 ° - 5 0 0 ° C .

u s i n g p u r e h y d r o g e n , o b t a i n e d f r o m U H . T h e x - r a y results o n 3

p o u n d s o b t a i n e d b y these m e t h o d s are p r e s e n t e d i n T a b l e I.

Fields and Moeller; Lanthanide/Actinide Chemistry Advances in Chemistry; American Chemical Society: Washington, DC, 1967.

com

250

LANTHANIDE/ACTINIDE CHEMISTRY

A B S O R P T I O N

S P E C T R U M

should have a 5/

O F

7RbF * 6PaF .

Tetravalent protactinium

4

e l e c t r o n a n d s h o w discrete o p t i c a l a b s o r p t i o n . T h i s is

1

d e m o n s t r a t e d i n T a b l e I I w h i c h shows the a b s o r p t i o n s p e c t r u m c h a r a c teristic of tetravalent p r o t a c t i n i u m . T h e s p e c t r u m w a s o b t a i n e d f r o m a m u l l i n a Fluorocarbon oil, held between

CaF

flats.

2

A C a r y 14 M R

spectrophotometer was used. Table II.

Absorption Spectrum of Tetravalent Protactinium Fluoride Compound

Peak Maxima, A

7RbF · 6PaF

2580 2920 3500 12600 14700 16000 17400 18270 18510

4

M W M S W , Br V W , Br VW VS, Narrow" W

F o r 7 R b F · 6 P a F , 3 N a F · P a F , a n d P a F , an intense infrared absorption b a n d is observed at — 6 4 8 5 c m . " , g i v i n g a value for fa of P a ( I V ) = 1567 c m . " .

a

4

4

4

1

1

Preparation and Lattice Constants of the L i F · X F and 7 N a F · 6 X F 4

(X =

Th —

fluorides

Cm)

(18)

Series.

a n d 7:6

been completed

4

T h e t w o series of 1:1 l i t h i u m - a c t i n i d e ( I V )

sodium-actinide(IV)

fluorides

have

(18)

for a l l a c t i n i d e s , t h o r i u m t h r o u g h c u r i u m (i.e.,

a v a i l a b l e a c t i n i d e s w h i c h e x h i b i t a tetravalent s t a t e ) .

now those

Berkelium would

u n d o u b t e d l y f o r m s i m i l a r c o m p o u n d s , b u t sufficient q u a n t i t i e s w e r e not yet a v a i l a b l e . A l t h o u g h the c o m p o u n d s L i F · T h F L i F · PaF

(13), 6UF

4

(7), 7 N a F · 6PaF

4

(7), L i F · U F

4

4

(13), 7 N a F · 6 T h F (13,14),

4

and 7 N a F ·

( 13 ) h a d b e e n k n o w n p r e v i o u s l y , d a t a for the l i t h i u m a n d s o d i u m

4

double

fluorides

lacking.

of n e p t u n i u m , p l u t o n i u m , a m e r i c i u m , a n d c u r i u m w e r e

These compounds

of either 1:1

L i : X or 7:6

have now been prepared.

Starting mixtures

N a : X were prepared b y evaporation

from

aqueous H C 1 s o l u t i o n . H y d r o g e n r e d u c t i o n of the n e p t u n i u m at 3 5 0 ° C . i n the presence of H F f o r m e d L i F · N p F T r e a t m e n t of

4

and 7NaF · 6 N p F . 4

the s t a r t i n g m i x t u r e s of

p l u t o n i u m , a m e r i c i u m , or

c u r i u m w i t h e l e m e n t a l fluorine at 3 5 0 ° C . for — 16 h o u r s w a s necessary to f o r m g o o d x-ray samples of L i F * X F Cm).

4

or 7 N a F · 6 X F

4

c o n d i t i o n s . W h e n h e a v i e r alkalis are present ( R b or C s ) , such mixtures yields P u ( V )

Pu, Am,

fluorination

of

fluorides.

R e c e n t single c r y s t a l studies o n L i F · U F (15)

(X =

N o o x i d a t i o n to p e n t a v a l e n t p l u t o n i u m w a s o b s e r v e d u n d e r these

4

(14)

and 7 N a F · 6 Z r F

4

e s t a b l i s h e d the space g r o u p assignments a n d s t o i c h i o m e t r y so t h a t

powder diffraction data on the new actinide compounds

could be


more

18.

PENNEMAN

ET

Actinide

AL.

Fluoride

r e a d i l y i n t e r p r e t e d . T h e 1:1 L i F * X F

4

251

Complexes

c o m p o u n d s are t e t r a g o n a l , space

g r o u p I 4 i / , w i t h 16 molecules per u n i t c e l l . T h e 7 N a F · 6 X F a

are r h o m

4

b o h e d r a l , space g r o u p R 3 , w i t h three m o l e c u l e s p e r h e x a g o n a l u n i t c e l l . I n b o t h series, a steady decrease i n m o l e c u l a r v o l u m e is n o t e d

from

t h o r i u m to c u r i u m w h i c h is e v i d e n c e for the a c t i n i d e c o n t r a c t i o n i n the t e t r a v a l e n t state. compounds.

F i g u r e 1 shows this c o n t r a c t i o n for the t w o types of

C e l l constants for these t w o series are g i v e n i n T a b l e I I I .

Rb" Κ

7:6

AF:MF

4

Na

LÎF:MF

Pa

Th

Np __L_

U

Pu

Am

4

Cm

ACTINIDE (IE)

Figure 1.

Molar volumes of rhombohedral Na M F and tetragonal LiMF on the basis of I M atom/molecule 7

6

31

5

Pentavalent Actinide Fluoride Complexes Protactinium(V).

A

new

series of

pentavalent protactinium and alkali

pounds K F · P a F , R b F · P a F , N H F 5

5

complex

fluorides 4

fluorides

containing

w a s s y n t h e s i z e d ; the c o m -

· P a F , and C s F · P a F 5

5

were

s h o w n to b e i s o s t r u c t u r a l ( 2 , 6 ). O t h e r complexes w i t h the r a t i o of one a l k a l i to one p r o t a c t i n i u m w e r e also p r e p a r e d b u t these LiF · PaF

5

a n d N a F · P a F , w e r e not i s o s t r u c t u r a l w i t h the p r e c e d i n g 5

g r o u p n o r w i t h e a c h other ( 6 ) . (M =

compounds,

C o m p l e x e s of the 2:1 t y p e , 2 M F * P a F

5

K , R b , C s b u t n o t L i or N a ) f o r m r e a d i l y . T h e 3:1 t y p e ( 3 M F ·

P a F ) w e r e also p r e p a r e d , a n d 3 R b F · P a F 5

9.6 A ( 6 ) .

5

w a s i n d e x e d as fee,

T h e s e latter t w o classes of h i g h e r complexes

a

0

=

were studied

to a lesser extent at L o s A l a m o s since it was f o u n d that the E n g l i s h g r o u p at H a r w e l l was i n v e s t i g a t i n g t h e m (10, I I , 1 2 ) . findings

O n e of t h e i r i n t e r e s t i n g

w a s the c o o r d i n a t i o n of n i n e for P a ( V ) i n 2 K F · P a F

t h a n seven as occurs i n the t a n t a l u m a n a l o g .


5

rather

252

LANTHANIDE/ACTINIDE CHEMISTRY

Table III.

L i X F ; T e t r a g o n a l , Spac e G r o u p I 4]L / a j Ζ —: 16 r >

Compound LiThF LiPaF LiUF LiNpF LiPuF LiAmF LiCmF

a , A. 0

15.10 14.97 14.8592 14.80 14.67 14.63 14.57

5

5

5

5

5

5

5

Na X F ; 7

Na Na Na Na Na Na Na

6

7 7 7 7 7 7 7

± ± ± ± ± ±

0

6.60 6.576 6.5433 6.516 6.479 6.449 6.437

0.02 0.0096 0.02 0.02 0.02 0.02

Th F Pa F U F Np F Pu F Am F Cm F 6

14.96 14.81 14.72 14.64 14.55 14.48 14.41

3 1

6

3 1

6

3 1

6

3 1

6

3 1

6

3 1

c

3 1

9.912 9.850 9.84 9.785 9.741 9.665 9.661

± 0.02 ± ± ± ±

T h e 1:1 complexes

0.02 0.02 0.02 0.02 between

± ± ± ± ± ±

3

± 0.003 ± ± ± ±

13 7 15 18 18,19 18 18

94.1 92.0 90.3 89.2 87.1 86.3 85.4

0.003 0.0009 0.005 0.005 0.005 0.005

Space Group R3, Ζ =

Hexagonal (Rhombohedral),

sl

Mol. Vol., Reference A.

, A.

0.003 0.003 0.003 0.003

the h e a v i e r a l k a l i

3

640.4 623.7 615.5 605.4 595.3 585.0 579.1

13 7 13 18 18 18 18

fluorides

and pro

t a c t i n i u m p e n t a f l u o r i d e are e s p e c i a l l y i n t e r e s t i n g since t h e y are n o t l i k e t h e i r t a n t a l u m analogs b u t m o r e closely r e s e m b l e those of p e n t a v a l e n t u r a n i u m . W e find t h e m to b e o r t h o r h o m b i c (see

Table I V ) .

Systematic

absences of reflections i n d i c a t e the space g r o u p to b e A b m 2 or A b m m (Cmma).

Reflections of the t y p e h k 1 for w h i c h k a n d 1 are

odd

are e x t r e m e l y w e a k , w h i l e those w i t h k a n d 1 even are g e n e r a l l y q u i t e strong.

T h e i n t e n s i t y d i s t r i b u t i o n of the strong reflections suggest that

at least the a c t i n i d e atoms are i n s u c h s p e c i a l positions as to

produce

a p s e u d o - c e l l of one q u a r t e r the v o l u m e of the t r u e c e l l . U r a n i u m ( V ) . I n the case of u r a n i u m , gaseous fluorine w i l l n o r m a l l y take U F o n past U F to U F . I n contrast, w e find that fluorine o x i d a t i o n 4

of U F

4

5

6

i n l i q u i d a n h y d r o u s H F p r o c e e d s r e a d i l y to U F

5

a n d t h e n goes

o n l y s l o w l y to U F . If a l k a l i fluoride is also present, the m e t h o d is espe 6

c i a l l y u s e f u l i n the p r e p a r a t i o n of M F · U F c o m p o u n d s free f r o m traces 5

of U ( I V ) or U ( V I ) . T h e t e c h n i q u e is g i v e n b e l o w : ( 1 ) W e p r e p a r e d U F b y s t i r r i n g a suspension of h i g h surface area U F i n l i q u i d a n h y d r o u s H F at 2 5 ° C . u n d e r 10 p.s.i.g. of F . T h e o x i d a t i o n c a n be r e a d i l y h a l t e d at / 2 - U F w h i c h is also i n s o l u b l e i n l i q u i d H F . 5

4

2

5

( 2 ) A s t i r r e d s l u r r y of C s F a n d U F ( 1 : 1 m o l e r a t i o ) i n l i q u i d H F w a s t r e a t e d w i t h F at 10 p.s.i.g., r e s u l t i n g i n s m o o t h o x i d a t i o n of U ( I V ) to U ( V ) , g i v i n g a clear b l u e s o l u t i o n of C s F · U F . O n e v a p o r a t i o n of H F , b l u e crystals of p u r e C s F · U F w e r e d e p o s i t e d . W i t h R b F , l i g h t y e l l o w R b F · U F crystals w e r e d e p o s i t e d f r o m the b l u e s o l u t i o n of R b F · U F i n l i q u i d H F . I n these latter reactions, U F n e e d not b e of h i g h surface area since the M F · U F r e a c t i o n p r o d u c t s are soluble. 4

2

5

5

5

5

4

5


18.

PENNEMAN

ET AL.

Neptunium ( V )

Actinide

Fluoride

A l t h o u g h U F , U F , and U F

and Plutonium ( V ) .

are w e l l k n o w n c o m p o u n d s ,

253

Complexes 4

e v i d e n c e for N p F

5

and P u F

5

6

is l a c k i n g .

5

U s i n g the m e t h o d w h i c h p r o v e d successful i n p r e p a r i n g U F , w e f o u n d 5

t h a t at 2 5 ° C , N p F to N p F

5

4

(0.17 g r a m s ) as a s l u r r y i n H F w a s n o t o x i d i z e d

b y 10 p.s.i.g. of F . H o w e v e r , w h e n 10 grams of C s F w e r e 2

a d d e d a n d H F p u m p e d off, T h e green N p F

fluorine

t h e n c a u s e d o x i d a t i o n to N p ( V ) .

d i s s o l v e d i n the r e s i d u a l w a r m ( 5 0 ° - 7 0 ° C . ) C s F · 2 H F

4

m i x t u r e a n d was o x i d i z e d b y F complex; C s F - N p F this s o l u t i o n ( 5 ) .

5

2

to a s o l u b l e , m a g e n t a N p ( V ) 5

W h e n l i q u i d H F w a s r e c o n d e n s e d o n this m a t e r i a l ,

d i s p r o p o r t i o n a t i o n took p l a c e , as d e d u c e d green N p F

4

fluoride

(isostructural w i t h C s F · U F ) was deposited from f r o m the o b s e r v a t i o n t h a t

r e m a i n e d b e h i n d a n d orange, v o l a t i l e N p F

the c o n n e c t i n g t r a p . C s F · N p F

5

6

condensed i n

is best p r e p a r e d b y the d r y t e c h n i q u e s

l i s t e d b e l o w for p l u t o n i u m ; d a t a for this c o m p o u n d are g i v e n i n T a b l e I V .

Table IV. Some A l k a l i Fluoride : Protactinium ( V ), U r a n i u m ( V ), N e p t u n i u m ( V ) , P l u t o n i u m ( V ) Fluoride Complexes* (1:1) Isostructural Orthorhombic Compounds

a , A.

b , A.

c , A.

5.64 5.61 5.84 5.83 5.86 5.82 6.14

11.54 11.46 11.90 11.89 11.97 11.89 12.56

7.98 7.96 8.03 8.03 8.04 8.03 8.06

0

0

K F · PaF KF · UF N H F · PaF NH F ·U F RbF · PaF RbF · U F CsF · PaF 5

5

4 4

5

5

5

5

5

0

(Id) Isostructural Rhombohedral Compounds CsF · U F CsF · N p F CsF · P u F

8.39 8.386 8.370

8.04 8.017 8.006

5

5

5

(2:1) Isostructural Monoclinic Compounds 2RbF · N p F 2RbF · P u F

5

5

A complete structure determination of R b P a F Keller (16).

a

13.42 13.41

6.26 6.27 6

6

8.90 (β 8.84 (β

= =

is b e i n g made b y B u r n s , L e v y , a n d


254

LANTHANIDE/ACTINIDE

The compounds 2 R b F · P u F

5

and C s F · P u F

5

CHEMISTRY

w e r e t h e first fluoride

c o m p l e x e s to b e c h a r a c t e r i z e d i n w h i c h a t r a n s u r a n i u m e l e m e n t i n t h e p e n t a v a l e n t state occurs w i t h o u t t h e " y l " t y p e of o x y g e n b o n d i n g ( 2 3 ) . F l u o r i n e gas w a s u s e d to o x i d i z e a n h y d r o u s s o l i d m i x t u r e s of r u b i d i u m fluoride

or c e s i u m

fluoride-plutonium(IV)

fluorides

i n 2 : 1 a n d 1:1 m o l e

r a t i o . T h e m i x t u r e s w e r e c o n t a i n e d i n s a p p h i r e boats a n d w e r e e x p o s e d to 6 p.s.i.g. F gas at 3 5 0 ° - 4 0 0 ° C . f o r times v a r y i n g f r o m 4 to 16 hours. 2

The compound 2 R b F c

0

=

8.84, β =

2RbF · NpF UF

5

5

· PuF

5

is m o n o c l i n i c , a

0

=

6.27, b

9 0 ° ; i t is i s o s t r u c t u r a l w i t h 2 K F · T a F

(5). C s F · P u F

5

0

5

—

13.42,

(17) a n d

is r h o m b o h e d r a l , i s o s t r u c t u r a l w i t h C s F ·

( 2 1 ) . D a t a o n these 1:1 c o m p l e x e s are l i s t e d i n T a b l e I V .

Literature Cited (1) Asprey, L. B., Penneman, R. Α., Inorg. Chem. 1, 134 (1962). (2) Asprey, L. B., Penneman, R. Α., Science 145, 924 (1964). (3) Asprey, L. B., Kruse, F. H., Penneman, R. Α., J. Am. Chem. Soc. 87, 3518 (1965). (4) Asprey, L. B., Penneman, R. Α., Centre Natl. Rech. Sci. (Paris) Colloq. Intern. Phys. Chem. 154, 109 (1966). (5) Asprey, L. B., Keenan, T. K., Penneman, R. Α., Sturgeon, G. D., Inorg. Nucl. Chem. Letters 2, 19 (1966). (6) Asprey, L. B., Kruse, F. H., Rosenzweig, Α., Penneman, R. Α., Inorg. Chem. 5, 659 (1966). (7) Asprey, L. B., Kruse, F. H., Penneman, R. Α., Inorg. Chem. 6, 544 (1967). (8) Benz, R., Douglass, R. M., Kruse, F. H., Penneman, R. Α., Inorg. Chem. 2, 799 (1963). (9) Barton, C. J., et al., U. S. At. Energy Comm. Oak Ridge Natl. Lab. Rept. ORNL-2548 (Nov. 2, 1959). (10) Brown, D., Smith, A. J., Chem. Commun. 554 (1965). (11) Brown, D., Easey, J. F., Nature 205, 589 (1965). (12) Brown, D., Easey, J. F., J. Chem. Soc. 1966, 254. (13) Brunton, G. D., Insley, H., McVay, T. N., Thoma, R. E., U. S. At. Energy Comm. Oak Ridge Natl. Lab. Rept. ORNL-3761, (Feb. 1965). (14) Brunton, G. D., U. S. At. Energy Comm. Oak Ridge Natl. Lab. Rept. ORNL-3913, 10 (1966); Acta Cryst. 21, 814 (1966). (15) Burns, J. H., Ellison, R. D., Levy, Η. Α., U. S. At. Energy Comm. Oak Ridge Natl. Lab. Rept. ORNL-3913, 17 (1966); Acta Cryst. (to be pub lished). (16) Burns, J. H., Levy, Η. Α., Keller, O. L., Oak Ridge Natl. Lab. (private communication). (17) Hoard, J. L., J. Am. Chem. Soc. 61, 1252 (1939). (18) Keenan, T. K., Inorg. Nucl. Chem. Letters 2, 153, 211 (1966). (19) Keller, C., Schmutz, H., Inorg. Nucl. Chem. Letters 2, 355 (1966). (20) Kruse, F. H., Asprey, L. B., Inorg. Chem. 1, 137 (1962). (21) Penneman, R. Α., Sturgeon, G. D., Asprey, L. B., Inorg. Chem. 3, 126 (1964). (22) Penneman, R. Α., Kruse, F. H., George, R. S., Coleman, J. S., Inorg. Chem. 3, 309 (1964). (23) Penneman, R. Α., Sturgeon, G. D., Asprey, L. B., Kruse, F. H., J. Am. Soc. 87, 5803 (1965).


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PENNEMAN ET A L .

Actinide Fluoride Complexes

255

(24) Thoma, R. E., Barton, C. J., Friedman, H. Α., Grimes, W. R., Insley, H., Moore, R. E., J. Am. Ceram. Soc. 41, 63 (1958). (25) Thoma, R. E., Insley, H., Landau, B. S., Friedman, H. Α., Grimes, W. R., J. Am. Ceram. Soc. 41, 538 (1958). (26) Thoma, R. E., Inorg. Chem. 1, 220 (1962). (27) Thoma, R. E., Insley, H., Herbert, G. M., Friedman, H. Α., Weaver, C. F., J. Am. Ceram. Soc. 46, 37 (1963). (28) Thoma, R. E., Friedman, H. Α., Penneman, R. Α., J. Am. Chem. Soc. 88, 2046 (1966). (29) Zachariasen, W. H., J. Am. Chem. Soc. 70, 2147 (1948). RECEIVED October 18, 1966. This work was sponsored by the U. S. Atomic Energy Commission.


Actinide Chemistry

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