Uranyl Metaborate and Sodium Uranyl Borate

23 Uranyl Metaborate and Sodium Uranyl Borate HENRY R. HOEKSTRA

Downloaded by UNIV OF MISSOURI COLUMBIA on April 29, 2013 | http://pubs.acs.org Publication Date: June 1, 1967 | doi: 10.1021/ba-1967-0071.ch023

Argonne National Laboratory, Argonne, Ill.

Uranyl metaborate, UO (BO ) , is prepared by heating U O with an excess of boric oxide in air at 900°-1100°C. In the presence of excess B O the salt is thermally stable to 1100°C. in air and to ~950°C. in a nitrogen atmosphere. Without excess B O , decomposition begins at 750°C. in air. The greenish-yellow crystals of UO (BO ) are insoluble in water but hydrolyze slowly to UO (OH) · H O. The crystal symmetry is believed to be monoclinic. The infrared spectrum of UO (BO ) is compared with spectra of ring-type (NaBO ) and chain-type (CaB O ) metaborates. The synthesis of several alkali uranyl borates (MUO BO ) is described, and the infrared spectrum of the sodium salt is analyzed with the aid of a borate preparation enriched in B . 2

2

2

2 2

3

3

3

2

2

2

8

2 2

2

2

2 2

2

2

4

2

3

10

THew references to u r a n i u m borates a p p e a r i n t h e literature. ^

Larson

(12) r e p o r t e d that y e l l o w crystals, w h o s e c o m p o s i t i o n w a s a s s u m e d

to b e 3 U 0

3

· B 0 2

( u r a n y l orthoborate), were obtained among other

3

p r o d u c t s f r o m a m e l t of u r a n i u m n i o b a t e i n b o r i c oxide.

Bruhat and

D u b o i s (2) stated that p e r b o r a t e solutions react w i t h u r a n i u m o x i d e to g i v e a n a n h y d r o u s stable y e l l o w salt o f t h e c o m p o s i t i o n U B 0 .

No

4

f u r t h e r i n f o r m a t i o n has a p p e a r e d o n either o f these c o m p o u n d s .

Experimental T h e c o m p o u n d s u s e d i n this i n v e s t i g a t i o n ( H B 0 , U 0 , U 0 , C a O , a n d t h e a l k a l i m e t a l c a r b o n a t e s ) w e r e reagent grade c h e m i c a l s . B o r i c acid, U O , a n d L i C 0 were used directly, U 0 , N a C 0 , a n d K C 0 w e r e d r i e d at 5 0 0 ° C , a n d C a O w a s d r i e d at 9 0 0 ° C . p r i o r to use. A sample of boric acid enriched i n B to 9 2 % w a s u s e d i n several b o r a t e p r e p a r a t i o n s . T h e i n d i c a t e d i s o t o p i c r a t i o w a s c o n f i r m e d b y mass spect r o g r a p h i c analysis. T h e p r o d u c t s p r e p a r e d i n t h e experiments d e s c r i b e d b e l o w w e r e i n v e s t i g a t e d b y p o w d e r x - r a y d i f f r a c t i o n m e t h o d s . A P h i l l i p s 114.59 m m . 3

3

s

2

3

3

3

3

2

3

3

1 0

320 In Lanthanide/Actinide Chemistry; Fields, P., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1967.

8

2

3

23.

Uranyl

H O E K S T R A

321

Borates

c a m e r a was u s e d w i t h n i c k e l - f i l t e r e d c o p p e r r a d i a t i o n to o b t a i n the p o w d e r patterns. I n f r a r e d spectra of the p r o d u c t s w e r e o b t a i n e d o n a B e c k m a n I R - 1 2 spectrophotometer. P o t a s s i u m b r o m i d e disks (200 m g m . ) c o n t a i n i n g 0.4 to 1 % of the b o r a t e salt p e r m i t t e d i n v e s t i g a t i o n of the s p e c t r a b e t w e e n 4000 a n d 300 c m . " , w h i l e N u j o l m u l l s s p r e a d o n p o l y e t h y l e n e disks w e r e u s e d i n the 300 to 200 c m . " r e g i o n of the spectra. T h e borate salts u s e d i n the s p e c t r a l studies w e r e p u l v e r i z e d for 1 m i n u t e i n a W i g l b u g a m a l g a m a t o r to i m p r o v e the q u a l i t y a n d d e t a i l of the i n f r a r e d spectra. P r e p a r a t i o n of U r a n y l M e t a b o r a t e . A n a n h y d r o u s b o r i c oxide glass is p r e p a r e d b y t h e r m a l d e c o m p o s i t i o n of b o r i c a c i d i n a p l a t i n u m d i s h . T h e u r a n i u m o x i d e p o w d e r is t h e n s p r e a d o n the surface of the b o r i c o x i d e , a n d the reactants are h e a t e d i n air at — 1 0 0 0 ° C . u n t i l R e a c t i o n 1 1


1

2U 0 3

8

+ 6B 0 2

+ 0

3

2

-> 6 U 0 ( B 0 ) 2

2

(1)

2

is c o m p l e t e . C o n v e r s i o n to the m e t a b o r a t e takes p l a c e s l o w l y . A t h i n film of finely p o w d e r e d U 0 reacts c o m p l e t e l y w i t h i n s e v e r a l h o u r s , b u t a t h i c k e r l a y e r of sintered U 0 m a y r e q u i r e several weeks to r e a c h c o m p l e t i o n . S i n c e b o r i c o x i d e v o l a t i l i z e s s l o w l y at the t e m p e r a t u r e r e q u i r e d to effect this r e a c t i o n , a n excess of the sesquioxide is necessary. A 5- to 10-fold excess of B 0 gives c o m p l e t e c o n v e r s i o n to U 0 ( B 0 ) w i t h i n a reasonable t i m e . A loose fitting cover c a n be u s e d to m i n i m i z e B 0 loss w h i l e p e r m i t t i n g access of the o x y g e n r e q u i r e d i n the r e a c t i o n . T h e u s e f u l w o r k i n g t e m p e r a t u r e range is 900° to 1100°C. B e l o w 9 0 0 ° C . the r e a c t i o n rate is too s l o w , w h i l e a b o v e 1 1 0 0 ° C . the salt is not f o r m e d a n d a c t u a l d e c o m p o s i t i o n is o b s e r v e d , e v e n i n the presence of excess B 0 . A f t e r c o m p l e t e c o n v e r s i o n to U 0 ( B 0 ) is a c h i e v e d , the u r a n y l salt is f r e e d f r o m B 0 b y d i s s o l v i n g the excess sesquioxide i n absolute m e t h a n o l . R e a s o n a b l e care s h o u l d be t a k e n to m i n i m i z e access of m o i s t u r e to the m e t a b o r a t e d u r i n g the p u r i f i c a t i o n step, b u t c o m p l e t e l y a n h y d r o u s c o n d i t i o n s are not r e q u i r e d . A s a m p l e of U 0 B 0 p r e p a r e d as d e s c r i b e d a b o v e gave the f o l l o w i n g a n a l y t i c a l r e s u l t s : u r a n i u m f o u n d 66.80%, theoretical 66.93%, and boron found 6.02%, theoretical 6.08%. A t t e m p t s to p r e p a r e u r a n y l borate f r o m U 0 i n s t e a d of U 0 were o n l y p a r t i a l l y successful. T h e t r i o x i d e is m o r e r e a c t i v e t h a n U O a n d e l i m i n a t e s the necessity for a n o x i d a t i o n step i n the m e t a b o r a t e synthesis r e a c t i o n , b u t the l o w t h e r m a l s t a b i l i t y of U 0 restricts the r e a c t i o n t e m p e r a t u r e to < 6 5 0 ° C . I n f r a r e d a n d x - r a y analyses of p r o d u c t s o b t a i n e d after h e a t i n g Ù 0 a n d B 0 m i x t u r e s for s e v e r a l days at 6 5 0 ° C . i n d i c a t e d that o n l y a m i n o r c o n v e r s i o n to the metaborate h a d b e e n effected. T h e " t w o c o n t a i n e r " p r o c e d u r e d e m o n s t r a t e d t h a t gaseous b o r i c o x i d e c a n be u s e d as w e l l as the m o l t e n o x i d e to o b t a i n c o n v e r s i o n of U 0 to the metaborate. T h e U 0 p o w d e r w a s p l a c e d i n a s m a l l p l a t i n u m d i s h s u s p e n d e d w i t h i n a l a r g e r d i s h c o n t a i n i n g the B 0 glass. T h e l a r g e r d i s h w a s c o v e r e d w i t h p l a t i n u m f o i l a n d h e a t e d at 1000°C. A s l o w c o n v e r s i o n of U O to the m e t a b o r a t e was a c h i e v e d , b u t s e v e r a l m o n t h s w e r e r e q u i r e d to c o m p l e t e the r e a c t i o n . T h i s t e c h n i q u e e l i m i n a t e s the necessity for a m e t h a n o l p u r i f i c a t i o n step. E a c h of the p r o c e d u r e s d e s c r i b e d a b o v e leads to the f o r m a t i o n of a microcrystalline U 0 ( B 0 ) p o w d e r . A l l attempts to p r e p a r e l a r g e r 3

8

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3

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2

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8

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8

3

8

2

3

3

s

2

2

2

In Lanthanide/Actinide Chemistry; Fields, P., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1967.

s

2

322

LANTHANIDE/ACTINIDE CHEMISTRY

crystals of the salt b y l o n g c o n t i n u e d h e a t i n g just b e l o w 1100°C. p r o v e d u n s u c c e s s f u l ; no a p p r e c i a b l e c r y s t a l g r o w t h c o u l d b e detected. L a r g e r crystals c a n b e o b t a i n e d b y a d d i n g a s m a l l a m o u n t of s o d i u m i o n , i n the f o r m of N a U 0 or N a B 0 , to the r e a c t i o n m i x t u r e . A f t e r s e v e r a l weeks at 1 0 0 0 ° C , t h i n g r e e n i s h - y e l l o w flakes a n d needles of u r a n y l m e t a b o r a t e c a n b e i s o l a t e d f r o m the m i x t u r e b y a m e t h a n o l p u r i f i c a t i o n . X - r a y a n d i n f r a r e d analysis h a v e c o n f i r m e d the i d e n t i t y of this p r o d u c t e v e n t h o u g h (see b e l o w ) l a r g e r amounts of s o d i u m i o n l e a d to the s y n thesis of another salt. Downloaded by UNIV OF MISSOURI COLUMBIA on April 29, 2013 | http://pubs.acs.org Publication Date: June 1, 1967 | doi: 10.1021/ba-1967-0071.ch023

2

2

Table I.

7

2

4

7

X - R a y Diffraction D a t a on U r a n i u m Borates

Uranyl Metaborate

Sodium Uranyl

Borate

ntensity

D

Intensity

D

Intensity

D

Intensity

D

W W M M W W M VVW VW VW

5.228 4.858 4.372 3.815 3.300 3.098 2.920 2.733 2.635 2.602 2.569 2.454 2.320 2.205 2.102 2.086 2.050 1.982 1.940 1.921 1.887 1.867 1.778 1.759 1.736 1.686 1.676

VVW VW F F F F VVW VVW VW VVW VVW VVW VVW F VW F F F F W VW F VW

1.664 1.639 1.625 1.592 1.555 1.552 1.526 1.519 1.503 1.473 1.465 1.439 1.402 1.400 1.381 1.351 1.337 1.330 1.320 1.303 1.249 1.229 1.221

M W VW M M M S VW W VW F VW M F W F F W W F VW VW F VVW VW F W

5.738 5.343 5.085 4.223 4.070 3.919 3.409 3.040 2.947 2.891 2.842 2.786 2.583 2.540 2.493 2.424 2.384 2.291 2.244 2.130 2.104 2.086 2.044 2.007 1.976 1.925 1.880

VW VVW VW VW VW VW B-W F F F F VVW F VVW F VW W W F VVW F VVW F VVW VVW F F W W

1.828 1.787 1.767 1.736 1.720 1.696 1.666 1.647 1.600 1.585 1.574 1.539 1.525 1.521 1.494 1.460 1.446 1.433 1.403 1.374 1.364 1.339 1.328 1.325 1.306 1.295 1.249

w VVW VW VW VW VVW

w VVW VW VW VW VW VVW F B-W VVW VVW

Preparation of Sodium and Calcium Metaborate. T h e s e c o m p o u n d s c a n b e p r e p a r e d b y w e i g h i n g a n d m i x i n g the c a l c u l a t e d amounts o f Na C0 or C a O w i t h H B 0 . T h e m i x t u r e s are h e a t e d c a r e f u l l y to l i b e r a t e v o l a t i l e p r o d u c t s ; the r e s i d u e is t h e n h e a t e d s t r o n g l y to f o r m the m o l t e n m e t a b o r a t e . T h e c o m p o s i t i o n of the p r o d u c t c a n be d e t e r m i n e d b y m e a s u r i n g w e i g h t loss d u r i n g the r e a c t i o n . A n y b o r i c oxide lost d u r i n g the s a m p l e i g n i t i o n is r e p l a c e d b y a d d i n g m o r e b o r i c a c i d a n d r e f u s i o n to f o r m a h o m o g e n e o u s p r o d u c t . P o w d e r patterns of N a B 0 and 2

3

3

3

2


23.

Uranyl

H O E K S T R A

323

Borates

C a ( B 0 ) 2 p r e p a r e d b y this p r o c e d u r e w e r e f o u n d to b e i n excellent agreement w i t h data given b y M a r e z i o , Plettinger, a n d Zachariasen ( 15). P r e p a r a t i o n of S o d i u m U r a n y l B o r a t e . E q u i v a l e n t amounts of so d i u m , u r a n i u m , a n d b o r o n ( w e i g h e d as N a C 0 , U 0 , a n d H B 0 ) are m i x e d a n d g r o u n d i n a m o r t a r , t h e n h e a t e d i n a g o l d c r u c i b l e at g r a d u a l l y i n c r e a s i n g temperatures to d r i v e off v o l a t i l e p r o d u c t s . T h e s o l i d p r o d u c t is h e a t e d at 9 0 0 ° C . for a d a y to give a b r i g h t y e l l o w c r y s t a l l i n e p o w d e r . S i m i l a r p r o c e d u r e s c a n be u t i l i z e d to p r e p a r e the l i t h i u m a n d p o t a s s i u m u r a n y l borates. 2


2

3

3

3

3

Results and Discussion C r y s t a l S t r u c t u r e . C r y s t a l l o g r a p h i c studies o n a n u m b e r of m e t a l borates h a v e e s t a b l i s h e d t h a t e a c h b o r o n a t o m is b o n d e d either to three o x y g e n atoms i n a p l a n a r B 0

g r o u p or to f o u r o x y g e n atoms i n a t e t r a -

3

h e d r a l c o n f i g u r a t i o n . I n some instances b o t h arrangements are f o u n d i n a single c o m p o u n d .

B o r o n - o x y g e n b o n d lengths v a r y f r o m 1.27 to 1.59A.,

a n d Z a c h a r i a s e n has c o r r e l a t e d o b s e r v e d b o n d lengths w i t h b o n d strengths (21).

Anhydrous

b o n d s , as i n S c B 0

orthoborates 3

and I n B 0

3

may

have

three

equal

boron-oxygen

( 5 ) , or t w o Β — Ο b o n d s w h i c h are either

shorter or l o n g e r t h a n t h e t h i r d , as i n C o ( B 0 ) 3

3

2

or M g ( B 0 ) 3

T h e o x y g e n to b o r o n r a t i o of the metaborates ( 2 : 1 )

3

2

(I).

r e q u i r e s t h a t at

least one of the o x y g e n atoms m u s t be s h a r e d b e t w e e n t w o b o r o n atoms to o b t a i n the c u s t o m a r y b o r o n c o o r d i n a t i o n n u m b e r . M e t a b o r a t e s w i t h the triangular B O

f 3

g r o u p c r y s t a l l i z e i n ( a ) a t r i m e r i c r i n g structure, or (b)

c h a i n structure. S o d i u m a n d p o t a s s i u m metaborates a n d Ο

Ο

Ο

\ / \

/

Β

Β

Ο

Ο

Ο Ο

Ο

Β

Β 1 ο

Β ο-

Ο Ο

Ο \

a

orthorhombic

/ (b)

m e t a b o r i e a c i d are examples of the r i n g s t r u c t u r e , w h i l e c a l c i u m a n d s t r o n t i u m metaborates c r y s t a l l i z e i n the c h a i n structure. The powder

x-ray diffraction data on

U0 (B0 ) 2

2

2

are g i v e n i n

T a b l e I. T h e c r y s t a l s y m m e t r y is b e l i e v e d to b e m o n o c l i n i c , b u t the c e l l d i m e n s i o n s a n d a t o m i c a r r a n g e m e n t i n the c r y s t a l l a t t i c e h a v e not b e e n determined.

T h e single crystals of u r a n y l m e t a b o r a t e p r e p a r e d thus f a r

h a v e p r o v i d e d l i t t l e assistance i n d e t e r m i n i n g its s t r u c t u r e since

the

crystals e x h i b i t extensive t w i n n i n g . Studies to d e t e r m i n e w h e t h e r u r a n y l m e t a b o r a t e crystallizes i n the r i n g or c h a i n c o n f i g u r a t i o n are c o n t i n u i n g .


324


O n l y m i c r o c r y s t a l l i n e p o w d e r s of N a U 0 B 0 (see T a b l e I for p o w d e r d a t a ) h a v e b e e n o b t a i n e d to date, a n d the c r y s t a l s y m m e t r y is unknown. 2

U r a n y l metaborate

Thermal Stability.

3

is one

of the most

stable

( t h e r m a l l y ) u r a n y l salts; the p u r e salt begins to s h o w e v i d e n c e of composition only w h e n heated above 750°C.

de-

E v e n at 8 0 0 ° C , o n l y 3 %

d e c o m p o s i t i o n is o b s e r v e d after t w o days. T h e reverse r e a c t i o n occurs to 1 1 0 0 ° C . i n a i r w h e n excess B 0 Downloaded by UNIV OF MISSOURI COLUMBIA on April 29, 2013 | http://pubs.acs.org Publication Date: June 1, 1967 | doi: 10.1021/ba-1967-0071.ch023

2

b i l i t y is o c c a s i o n e d

is present, thus s h o w i n g t h a t this i n s t a -

3

b y loss of B 0 2

3

f r o m the c r y s t a l . T h e e q u i l i b r i u m

pressure of b o r i c o x i d e over the m e t a b o r a t e b e t w e e n 800° a n d 1 1 0 0 ° C . m u s t b e less t h a n that of p u r e B 0 . A n e q u a t i o n d e r i v e d b y N e s m e y a 2

n o v a n d F i r s o v a (16) pressure of 1100 ° C ;

3

f r o m effusion d a t a o n b o r i c o x i d e gives a v a p o r

a p p r o x i m a t e l y 0.0002 m m . at 1 0 0 0 ° C . a n d 0.002 m m .

at

these values m u s t constitute the u p p e r l i m i t for the u r a n y l

m e t a b o r a t e e q u i l i b r i u m d e c o m p o s i t i o n pressure. N o m e a s u r a b l e p o s i t i o n of U 0 ( B 0 ) 2

2

was d e t e c t e d

2

decom-

after t w o hours at 9 2 5 ° C .

n i t r o g e n atmosphere, b u t s u b s t a n t i a l d e c o m p o s i t i o n

o c c u r r e d after

in a two

h o u r s at 1 0 0 0 ° C . Reaction with Water.

U r a n y l m e t a b o r a t e is v i r t u a l l y i n s o l u b l e i n

w a t e r at 2 5 ° C , b u t the salt h y d r o l y z e s s l o w l y over s e v e r a l days to f o r m uranyl hydroxide. U0 (B0 ) 2

2

2

+ 5 H 0 -> U 0 ( O H ) 2

2

2

· H 0 + 2H B0 2

3

(2)

3

T h e h y d r a t e d p r o d u c t ( w h i c h m a y also b e d e s i g n a t e d as U 0 * 2 H 0 o r H U 0 · H 0 ) w a s i d e n t i f i e d b y its p o w d e r p a t t e r n a n d its i n f r a r e d spectrum. 3

2

4

2

2

S o d i u m u r a n y l borate is i n s o l u b l e i n w a t e r at 2 5 ° C . a n d gave n o e v i d e n c e of h y d r o l y s i s e v e n after a five-day exposure to l i q u i d w a t e r . T h e p o t a s s i u m salt s h o w e d s l i g h t e v i d e n c e of h y d r o l y s i s i n this t i m e , as d i d the l i t h i u m salt. Infrared Spectra. T h e i n t e r p r e t a t i o n of i n f r a r e d a n d R a m a n spectra of borates a n d r e l a t e d c o m p o u n d s

has b e e n confined l a r g e l y to the less

c o m p l e x configurations, e.g., substances c o n t a i n i n g i n d i v i d u a l B 0 , B 0 X , 3

or B O X

2

groups (4, 6, 13, 14, 18, 19).

2

T h e planar B 0 , with D

3h

3

sym-

m e t r y , has f o u r n o r m a l m o d e s of v i b r a t i o n . T h e s y m m e t r i c stretch ( vi ) is i n a c t i v e i n the i n f r a r e d , b u t the o u t - o f - p l a n e b e n d (v ), the a s y m m e t r i c 2

stretch (v ) 3

a n d the i n - p l a n e b e n d (j/ ) 4

are i n f r a r e d active. T h e v i b r a -

t i o n a l frequencies of t w o of the f u n d a m e n t a l s (v

2

and v ) 3

are d i r e c t l y

affected b y a change i n mass of the c e n t r a l a t o m i n the p l a n a r g r o u p . T h u s a change f r o m B proximately 4 %

n

0

3

to B

1 0

O

3

s h o u l d p r o d u c e a n increase of a p -

i n the o u t - o f - p l a n e b e n d i n g a n d a s y m m e t r i c s t r e t c h i n g

frequencies, w h i l e the other t w o m o d e s are v i r t u a l l y unaffected.


23.

Uranyl

H O E K S T R A

325

Borates

T h e Β — Ο a s y m m e t r i c s t r e t c h i n g v i b r a t i o n is u s u a l l y o b s e r v e d i n the 1380 to 1310 c m .

r e g i o n of the i n f r a r e d s p e c t r u m .

- 1

T h e frequency

s o m e w h a t l o w e r ( ^ 1 2 5 0 c m . " ) i n the m e t a l orthoborates. 1

is

In-plane and

o u t - o f - p l a n e b e n d i n g v i b r a t i o n s o c c u r i n the 750 to 600 c m . " p o r t i o n of 1

the s p e c t r u m . T h e a s y m m e t r i c s t r e t c h i n g f r e q u e n c y is s u b s t a n t i a l l y l o w e r (at ^ 1 0 0 0 cm." ) i n compounds 1

containing tetrahedral Β—Ο

bonds.

S p e c t r a of s u b s t i t u t e d borates are m o r e c o m p l e x as the s y m m e t r y is Downloaded by UNIV OF MISSOURI COLUMBIA on April 29, 2013 | http://pubs.acs.org Publication Date: June 1, 1967 | doi: 10.1021/ba-1967-0071.ch023

l o w e r e d to C

2 v

or C ; the s y m m e t r i c s t r e t c h i n g m o d e becomes i n f r a r e d s

a c t i v e , a n d the t w o degenerate m o d e s c a n e a c h separate i n t o t w o b a n d s to g i v e a t o t a l of six a b s o r p t i o n m a x i m a . A s i m i l a r result c a n b e o b s e r v e d i n the c r y s t a l l i n e orthoborates w h e r e the selection rules are g o v e r n e d

by

site s y m m e t r y r a t h e r t h a n p o i n t s y m m e t r y of the borate i o n . I n a d d i t i o n , u n e q u a l b o n d lengths i n B 0

3

3

" i o n c a n l o w e r the s y m m e t r y a n d l e a d to

as m a n y as six a b s o r p t i o n b a n d s i n the i n f r a r e d s p e c t r u m . R e l a t i v e l y l i t t l e i n f o r m a t i o n has a p p e a r e d o n the i n f r a r e d spectra of the metaborates.

I n a d d i t i o n to several s u r v e y

investigations

which

i n c l u d e a n u m b e r of m e t a b o r a t e spectra (8, 2 0 ) , some tentative b a n d assignments h a v e b e e n r e p o r t e d for several c o m p o u n d s

c o n t a i n i n g the

t r i m e r i c metaborate ( b o r o x o l e ) r i n g (6, 7 , 1 1 , 1 7 ) . T h e c h a i n - t y p e m e t a borate spectra h a v e n o t b e e n s t u d i e d i n a n y d e t a i l . F o u r t e e n v i b r a t i o n a l m o d e s are possible i n the D

3 7 i

b o r o x o l e r i n g , seven of w h i c h are active i n

the i n f r a r e d ( 2 A " a n d 5 E ' ). S o m e or a l l of the r e m a i n i n g seven b a n d s 2

m a y b e c o m e a c t i v e o w i n g to site g r o u p considerations, a n d s p l i t t i n g of the five E ' b a n d s is possible. A s a result metaborate i n f r a r e d spectra c a n be complex,

a n d t h e i r i n t e r p r e t a t i o n is less c e r t a i n t h a n

spectra. I n g e n e r a l , the b o r o n - o x y g e n 1500 to 1100 c m . "

1

p o r t i o n of the s p e c t r u m .

f o u n d at l o w e r frequencies,

orthoborate

s t r e t c h i n g v i b r a t i o n s o c c u r i n the T h e b e n d i n g m o d e s are

w i t h some as l o w as 200 c m . " . 1

Further

details are discussed b e l o w . U r a n y l , Sodium and C a l c i u m Metaborate.

T h e spectra of u r a n y l ,

s o d i u m , a n d c a l c i u m metaborates are i l l u s t r a t e d i n F i g u r e 1, a n d T a b l e I I lists the a b s o r p t i o n m a x i m a for three c o m p o u n d s . 92% B

1 0

c o m p o u n d s are also l o c a t e d .

T h e b a n d s i n the

D a t a o n the s o d i u m a n d c a l c i u m

salts, as representative of the r i n g a n d c h a i n m e t a b o r a t e structures, are i n agreement w i t h results r e p o r t e d b y G o u b e a u a n d H u m m e l (6). spectra g i v e n b y W i e r a n d S c h r o e d e r ( 2 0 )

The

are m o r e c o m p l e x a n d m a y

not represent p u r e phases. It is e v i d e n t f r o m the c h a r a c t e r i s t i c strong a b s o r p t i o n i n the 1400 to 1200 c m . " r e g i o n of the s p e c t r u m that U 0 ( B 0 ) 1

2

2

2

contains 3 - c o o r d i n a t e d

r a t h e r t h a n 4 - c o o r d i n a t e d b o r o n atoms, b u t that it cannot b e classed as a r i n g - or c h a i n - t y p e structure s i m p l y b y a c u r s o r y c o m p a r i s o n of the three spectra.

T h e b r o a d features of the three spectra are s i m i l a r , b u t e a c h


326


differs i n details. O n e d i s t i n c t i v e difference i n the u r a n y l salt is the p r e s ence of a r e l a t i v e l y strong b a n d at 950 c m . " . T h i s a b s o r p t i o n is assigned 1

to the a s y m m e t r i c s t r e t c h i n g m o d e of the u r a n y l g r o u p ( 1 0 ) .

The uranyl

b o n d l e n g t h c a n b e e s t i m a t e d w i t h the a i d of a n e q u a t i o n ( 3 )

derived

f r o m B a d g e r ' s r u l e , i.e., Ruo(A.)=-^-

+

m

VA*/

0

I n this e q u a t i o n v

is the a s y m m e t r i c s t r e t c h i n g f r e q u e n c y i n c m . " , a n d 1


A

53.3 a n d 1.17 are constants c h a r a c t e r i s t i c of the b o n d i n g atoms.

The

c a l c u l a t e d u r a n y l b o n d l e n g t h is 1.72A. T h e s t r o n g b a n d at 243 c m . "

1

m a y arise, at least i n p a r t , f r o m the b e n d i n g m o d e of this u r a n y l g r o u p .

Figure 1.

Infrared absorption

spectra of metaborates

T h e three m e t a b o r a t e spectra e a c h h a v e t w o strong b a n d s i n the asymmetric Β—Ο

stretching region

( ^ 1 4 5 0 and ^ 1 2 2 0

cm." ). 1

The

h i g h e r f r e q u e n c y b a n d is i d e n t i f i e d w i t h the s i d e - c h a i n or b r a n c h o x y g e n a t o m , w h i l e the l o w e r f r e q u e n c y b a n d is i d e n t i f i e d w i t h a r i n g o r c h a i n


23.

H O E K S T R A

stretching mode.

Uranyl

327

Borates

I n the absence of a n y d e f i n i t i v e s t r u c t u r a l d a t a , a n y

a t t e m p t to assign the r e m a i n i n g u r a n y l m e t a b o r a t e

bands

would

be

classed as h i g h l y s p e c u l a t i v e at present. Table II.

Infrared Bands in Sodium, Calcium and U r a n y l Metaborates ( c m . ) 1

Sodium B Downloaded by UNIV OF MISSOURI COLUMBIA on April 29, 2013 | http://pubs.acs.org Publication Date: June 1, 1967 | doi: 10.1021/ba-1967-0071.ch023

11

2035 1730 1565

Metaborate

βίο

VW VW W

2065 1730 1565

2350

VW

1497

sh

S

1482 1432 1375 1267 1238 950

1440

S

1270 1165

sh

S

1193

765 732 700 686 633

W M M M M

780 739 707 694 639

308 235

M W

308 238

W

715 700

M M

238

Metaborate

Intensity

1450 1423 1380 1255 1228 950

368

Calcium

βίο

sh sh

S S

W M

Table III.

V

Species

6 7 8 9 10 11 12

A " A " E' E' E' E' E' 2

2

727

B

11

Intensity

1483

370 238

Uranyl B

11

Metaborate

Intensity

βίο

2355 1788 1495 1456 1392

VW VW W W

1313

VW

1210 950 763 720

s s

1230 950 767 727

687

S

695

403

M

403

243

S

245

1508 1457 1418

S

M M

Infrared Vibrations of Boroxole Ring Structure Goubeau ùHummel

Description B-ring O out-of-plane bending B-branch Ο wagging B-branch 0 stretching B-ring 0 stretching B-ring Ο stretching B-ring Ο bending B-branch Ο rocking

T h e s p e c t r a l d a t a o n the t w o N a B 0

2

Present

—

700 (184) 1423,1450 1255 1228 715 238

(473) 1425,1450 1227,1255 702, 720

— —

p r e p a r a t i o n s do s h o w t h a t the

assignments of G o u b e a u a n d H u m m e l ( 6 ) , b a s e d o n s p e c t r a t a k e n i n the N a C l r e g i o n , are not e n t i r e l y correct.

T a b l e I I I i n d i c a t e s the b a n d s

assigned, as w e l l as the r e v i s e d assignments b a s e d o n the spectra de s c r i b e d i n T a b l e I I . G o u b e a u a n d H u m m e F s p l a c e m e n t of v at 473 c m . " 7

w a s b a s e d o n the assignment of a w e a k b a n d at 946 c m . " NaB0

2

1

to 2v . 7

1

The

s p e c t r u m of F i g u r e 1 i n d i c a t e s t h a t n o b a n d is f o u n d at 473 c m . " . 1


328


T h e w e a k a b s o r p t i o n at 946 c m .

c a n b e a s c r i b e d to νιο, as Parsons d i d

- 1

f o r m e t a b o r i c a c i d , or to the s y m m e t r i c s t r e t c h i n g m o d e (vi)

w h i c h is

w e a k l y active because of site s y m m e t r y considerations. I p r e f e r the latter e x p l a n a t i o n because the b a n d is unaffected b y a shift i n b o r o n r a t i o . T h e r e v i s e d f r e q u e n c y for v is 184 c m . " 7

1

the w e a k b a n d at 368 c m . " is 2v . T h i s f r e q u e n c y is i n better 1

isotope

o n the a s s u m p t i o n that agreement

7

w i t h Parson's assignment for the v i b r a t i o n i n m e t a b o r i c a c i d . T h e t w o r i n g stretching modes (v

9

a n d νιο) are assigned to the t w i n m a x i m a at

1255 a n d 1228 c m . " , a n d the b r a n c h o x y g e n s t r e t c h i n g v i b r a t i o n ( p o s s i b l y


1

s p l i t at the 1423 c m . "

1

s h o u l d e r ) to the 1450 c m . "

b a n d . T h e b a n d at

1

700 c m . " is assigned to v because it shows a m a r k e d isotope effect. 1

a g a i n , the assigned f r e q u e n c y (HB0 )3. 2

Here

6

is close to that g i v e n b y

Parsons

for

T h e f r e q u e n c y assigned to v u (715 c m . " ) is u n u s u a l l y h i g h , 1

b u t n o g o o d a l t e r n a t i v e seems to exist. A c c o r d i n g to the T e l l e r - R e d l i c h p r o d u c t r u l e ( 9 )

a B

1

0

/B

n

fre

q u e n c y r a t i o of — 1 . 0 4 s h o u l d be o b s e r v e d i n the p r o d u c t of the t w o A " 2

vibrations, and ^ 1 . 0 7 spectral

assignments

i n the p r o d u c t of the five E' v i b r a t i o n s . proposed

here

give

ratios

of

1.04

and

The 1.06

respectively. S o d i u m U r a n y l B o r a t e . T h e i n f r a r e d spectra of s o d i u m u r a n y l borate ( the n o r m a l a n d B

Figure 2.

1 0

e n r i c h e d salts ) are g i v e n i n F i g u r e 2, a n d T a b l e I V

Infrared absorption NaUOSOs

spectra of sodium uranyl borate 82% 92%

B B

11 w


23.

Table I V .

I n f r a r e d M a x i m a ( i n c m . " ) of A l k a l i U r a n y l B o r a t e s 1

LiU0 BO 2

cm."


1

329

Uranyl Borates

H O E K S T R A

NaU0 B0

s

2

Intensity

B cm.~ 11

Intensity

1

1370

sh S W S W S s w w

1300 1220 1170 960 925 860 797 710

S W S W M M VW w

1288 1203 1133 958 884 842 773 706

685 630 362 310 270 243

M MW M M W W

680 635 368 312 265

MS M M S M

KU0 BO

3

2

s

B cm." Intensity

cm."

Intensity

1350 1332 1297 1188 1156 958 890 841 775 709 701 680 637 367 314 264

1380

sh

1290 1207 1135 951 893 840 762 724

S W S VW M MS VW W

699 638 326 292 250

M MW M S M

10

1

1

S VW VW S W W S s w VW MS W M M S M

lists the a b s o r p t i o n m a x i m a f o u n d i n these a l k a l i u r a n y l borates.

The

d o u b l e salt spectra c a n b e d i v i d e d into f o u r p o r t i o n s : 1500-1100 c m . 1 0 0 0 - 800 c m .

- 1

- 1

7 5 0 - 600 c m . "

1

5 0 0 - 200 c m . "

1

Boron-oxygen stretching modes U r a n y l asymmetric stretching, possibly Β — O sym. stretching Boron-oxygen bending Uranium-secondary oxygen stretching, uranyl bending.

It is a s s u m e d i n the f o l l o w i n g d i s c u s s i o n that these borate salts c o n t a i n i n d i v i d u a l B 0

3

groups. T h e t e t r a h e d r a l Β — Ο

double

configuration

c a n b e e l i m i n a t e d f r o m c o n s i d e r a t i o n because of the s t r o n g a b s o r p t i o n m a x i m a at 1288 a n d 1133 c m . " . 1

T h e t w o s p e c t r a of the s o d i u m salt

i n d i c a t e t h a t b o t h h i g h f r e q u e n c y b a n d s arise f r o m Β — Ο

asymmetric

s t r e t c h i n g m o d e s because t h e y b o t h s h o w the 4 %

shift.

w e a k m a x i m u m at 960 c m . "

1

isotope

The

is p r o b a b l y v i , the s y m m e t r i c s t r e t c h i n g

v i b r a t i o n . T h e borate s p e c t r u m is thus g o v e r n e d b y C

2v

or C

8

selection

rules. T h e t w o m a x i m a at 900 a n d 850 c m . "

1

s h o w little or no isotope shift

a n d o c c u r i n the f r e q u e n c y r a n g e e x p e c t e d for the a s y m m e t r i c u r a n y l s t r e t c h i n g m o d e . It does not seem l i k e l y that the 850 c m . "

1

b a n d arises

f r o m the s y m m e t r i c U — Ο stretch a c t i v a t e d b y site s y m m e t r y because the a b s o r p t i o n is too strong. is n o t s y m m e t r i c a l , the

O t h e r possibilities are t h a t the u r a n y l

Ο—U—Ο

group

b o n d s are not c o l l i n e a r , or t w o different


330

L A N T H A N I D E / A C T I N I D E

C H E M I S T R Y

u r a n y l groups (sites) o c c u r i n t h e c r y s t a l . T h e d a t a a r e insufficient to p e r m i t a c h o i c e at this t i m e . T h e b a n d near 700 c m . " is assigned to t h e o u t - o f - p l a n e b e n d i n g i n 1

B0

3

3

~ since i t shows a n isotope shift, w h i l e t h e 650 c m . " b a n d is a n 1

i n - p l a n e b e n d i n g m o d e w i t h o u t isotope effect.

T h e w e a k b a n d at 780

c m . " m a y represent the r e m a i n i n g i n - p l a n e b e n d i n g v i b r a t i o n . 1

T h e l o w f r e q u e n c y m a x i m a are assigned to t h e U — O

n

stretching


m o d e s (i.e., to those o x y g e n atoms b o n d e d w e a k l y to u r a n i u m at r i g h t angles to t h e u r a n y l b o n d s ) a n d to t h e u r a n y l b e n d i n g v i b r a t i o n . T h e s p e c t r a of L i U 0 B 0 2

3

and K U 0 B 0 2

3

are s i m i l a r to t h e s o d i u m

salt s p e c t r u m — a n i n d i c a t i o n that t h e u r a n y l a n d b o r a t e site s y m m e t r i e s are s i m i l a r i n t h e three

compounds.

Literature Cited (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21)

Berger, S. V., Acta Chem. Scand. 3, 660 (1949). Bruhat, J., Dubois, H., Compt. rend. 140, 506 (1905). Carnall, W. T., Neufeldt, S. J., Walker, Α., Inorg. Chem. 4, 1808 (1965). Finch, Α., Pearn, E. J., Spectrochim Acta 19, 1621 (1963). Goldschmidt, V. M., Hauptmann, H., Nachr. Ges. Wiss. Gottingen 53 (1932). Goubeau, J., Hummel, D., Z. Phys. Chem. 20, 15 (1959). Goubeau, J., Keller, Η., Z. Anorg. Chem. 272, 303 (1953). Hart, P. B., Smallwood, S. E. F., J. Inorg.Nucl.Chem. 24, 1047 (1962). Herzerg, G., "Infrared and Raman Spectra," p. 231, Van Nostrand, Princeton, 1945. Hoekstra, H. R., Inorg. Chem. 2, 492 (1963). Lappert, M. F., J. Chem. Soc. 1958, 2791 (1958). Larsson, Α., Ζ. Anorg. Chem. 12, 188 (1896). Lehmann, W. J., Onak, T. P., Shapiro, I., J. Chem. Phys. 30, 1215, 1219 (1959). Lehmann, W. J., Weiss, H. G., Shapiro, I., J. Chem. Phys. 30, 1222, 1226 (1959). Marezio, M., Plettinger, Η. Α., Zachariasen, W. H., Acta Cryst. 16, 390, 594 (1963). Nesmeyanov, A. N., Firsova, L. P., Zh. Fis. Khim. 34, 1032 (1960). Parsons, J. L., J. Chem. Phys. 33, 1860 (1960). Pistorius, C. W. F. T., J. Chem. Phys. 31, 1454 (1959). Steele, W. C., Decius, J. C., J. Chem. Phys. 25, 1184 (1956). Wier, C. E., Schroeder, R. Α., J. Res. Natl. Bur. Std. 68A, 465 (1964). Zachariasen, W. H., Acta Cryst. 16, 385 (1963).

RECEIVED October 24, 1966. Based on work performed under the auspices of the U. S. Atomic Energy Commission.


Uranyl Metaborate and Sodium Uranyl Borate

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