Neptunium(IV), and Plutonium (IV) Borohydrides - American Chemical

16 Synthesis and Characterization of Protactinium(IV),

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Neptunium(IV), and Plutonium (IV) Borohydrides RODNEY H. BANKS and NORMAN M. EDELSTEIN Materials and Molecular Research Division, Lawrence Berkeley Laboratory, Berkeley, CA 94720 and Department of Chemistry, University of California, Berkeley, CA 94720

Abstract The actinide borohydrides of Pa, Np, and Pu have been prepared and some of their physical and optical properties measured. X-ray powderdiffractionphotographs of Pa(BH) have shown that it is isostructural toTh(BH ) and U(BH ) . Np(BH ) and Pu(BH ) are much more volatile than the borohydrides of Th, Pa, and U and are liquids at room temperature. Results from low-temperature single-crystal x-raydiffractioninvestigation of Np(BH ) show that its structure is very similar to Zr(BH ) . With the data from low-temperature infrared and Raman spectra, a normal coordinate analysis onNp(BH ) andNp(BD ) has been completed. EPR experiments on Np(BH ) /Zr(BH ) and Np(BD)/ Zr(BD ) have characterized the ground electronic state. 44

4

4

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4 4

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4 4

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4 4

4 4

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Four of the seven known metal tetrakis-borohydrides--Zr, Hf, Th, and U borohydrides (1,2)--were first synthesized about 30 years ago during the Manhattan project. They were found to be very volatile and reactive compounds. In recent years, much structural, spectroscopic, and chemical studies were done on these molecules. New tetrakis-borohydrides of the actinides Pa, Np, and Pu have recently been prepared by analogous reactions used in the syntheses of U and Th borohydrides (3). The Pa compound, Pa(BH ) , is isomorphous to and behaves like U(BH) and Th(BH) while x-ray studies on Np(BH) and the isostructural Pu(BH) have shown that they resemble the highly volatile Zr and Hf compounds both in structure and properties. All seven compounds contain triple hydrogen bridge bonds connecting the boron atom to the metal. The 14 coordinate Th, Pa, and U borohydrides (4), in addition, have double-bridged borohydride groups that are involved in linking metal atoms together in a low symmetry, polymeric structure. The structures of the other four borohydride molecules are mono4 4

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0-8412-0568-X/80/47-131-331$05.00/0 © 1980 American Chemical Society Edelstein; Lanthanide and Actinide Chemistry and Spectroscopy ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

332

LANTHANIDE

A N D ACTINIDE

CHEMISTRY A N D SPECTROSCOPY

meric and much more symmetrical; the 12 coordinate metal is surrounded by a tetrahedral array of BH¯4 groups (5,6,7). In an effort to understand the energy level structures of actinide 4+ ions in borohydride environments, optical and magnetic measurements have been initiated. Spectra of pure Np(BH) and Np(BD ) , and these compounds diluted in single-crystal host matrices of Zr(BH) and Zr(BD ) , respectively, have been obtained in the region 2500-300 nm at 2K. The covalent actinide borohydrides display rich vibronic spectra (8) and assignment of the observed bands depends on a knowledge of the vibrational energy levels of M(BH) molecules. A normal coordinate analysis derived from low-temperature infrared and Raman spectra of Np(BH)4 and Np(BD) was undertaken to elucidate the nature of their fundamental vibrations and overtones. Electron paramagnetic resonance (epr) spectra of Np(BH) and Np(BD) that characterize the ground electronic state have been obtained in a number of host materials. Optical spectra of Pa(BH) and Pa(BD) isolated in an organic glass were obtained in the near infrared and visible regions at 2K. This paper will summarize our progress to date on these studies. 44

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Experimental Preparation of Borohydrides. Metal borohydrides are very chemically reactive and most of them are pyrophoric in air. The syntheses of the compounds and all manipulations with Al, Zr, Hf, Np, and Pu borohydrides must therefore be performed in a greasefree high-vacuum line. Work involving the less volatile Th, Pa, and U borohydrides can also be done in argon-filled dryboxes. All actinide borohydrides are made by reacting the anhydrous actinide tetraf luoride with liquid Al(BHi+) 3 in the absence of a solvent in a sealed glass reaction tube. The basic reaction equation is: AnFi+ + 2Al(BHt) -> An(BHit) 4. + 2A1F2BHI,. t 3

Purification of the desired product is accomplished by sublimation where only the unreacted Al(BHi) and An(BHi+) + i are volatile. The large difference in volatilities of these compounds permit easy separation. Th(BH)i and PaCBH^) ^ are obtained on a 0° cold finger by heating the solid reaction mixture to 120° and 55° , respectively. Uranium, neptunium, and plutonium borohydrides sublime at room temperature and are collected in a dry ice trap through which the Al(BHit)3 passes into a liquid nitrogen trap. The stabilities of the actinide borohydrides dictate the type of reaction conditions needed for successful preparation. The polymeric compounds are stable at room temperature and their syntheses are carried out at 25° for about five days. NpCBH^K and Pu(BHttK are unstable at room temperature and require that the tetrafluorides react at 0° for only a few hours. These two f 3

t

+

Edelstein; Lanthanide and Actinide Chemistry and Spectroscopy ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

BANKS AND EDELSTEIN

16.

Pa(IV),

Np(IV),

and Pu(IV)

Borohydrides

333

borohydrides must be s t o r e d a t d r y - i c e or l i q u i d - n i t r o g e n temperature i n a g r e a s e l e s s storage tube. Zr(BHit)i» used i n experiments described here was prepared s i m i l a r l y t o U C B H O I * by r e a c t i n g N a Z r F with A l ( B H ) . 2

6

l+

3

P r e p a r a t i o n of Borodeuterides. A l l glassware which contacts the borodeuterides had been p r e v i o u s l y p a s s i v a t e d w i t h B2D6 or t r e a t e d with D2O and then baked out thoroughly under vacuum. The borodeuterides of Th, Pa, and U a r e prepared as d e s c r i b e d above using A l ( B D O 3 source o f BD^. The high v o l a t i l i t i e s of the covalent borohydrides a l l o w t h e i r deuterated analogs t o be prepared by a more s a t i s f a c t o r y method that u t i l i z e s the H D exchange property of these molecules w i t h deuterium ( 9 ) . I f the D2 gas i s maintained i n l a r g e excess, the extent of e q u i l i b r i u m w i l l g i v e the f u l l y deuterated product i n high y i e l d . In a passivated g l a s s bulb, a mixture o f the borohydride vapor and 1 atm of D gas was allowed t o stand f o r a few days a t room temperature. A f t e r f r e e z i n g out the products a t -78° and evacuating, another volume of D2 was added and the exchange r e a c t i o n continued. Three c y c l e s were s u f f i c i e n t t o g i v e the metal borodeuteride having an i s o t o p i c p u r i t y as high as that of the deuterium used (99.7%). a

s

t

n

e

2

An attempt to prepare Np(BTit)i* u s i n g the above method r e s u l t e d i n the decomposition of the borohydride due t o the extremely high r a d i a t i o n f i e l d of the T2 gas (66 C i ) and no v o l a t i l e Np compound was recovered. The vapor pressure of Np(BHi )i was determined as a f u n c t i o n of temperature u s i n g a Bourdon gauge ( 5 ) . The data f o r the l i q u i d and s o l i d shown i n F i g u r e 1 were used i n c a l c u l a t i n g thermodynamic q u a n t i t i e s of the a c t i n i d e borohydrides given i n Table 1. A s i n g l e c r y s t a l x-ray study (5) was c a r r i e d out f o r Np(BHt )i a t 130K. I t s s t r u c t u r e i s shown i n F i g u r e 2. Gas-phase i n f r a r e d and low-temperature s o l i d - s t a t e i n f r a r e d and Raman s p e c t r a were obtained f o r Np(BHO«+ and Np(BDt )i from 2.5 to 50y. Assignments were made o f the observed bands and the fundamental f r e q u e n c i e s were f i t t e d t o c a l c u l a t e d v a l u e s i n a normal coordinate a n a l y s i s (10). E l e c t r o n paramagnetic resonance s p e c t r a were taken of Np(BH )t /Zr(BHi ) and Np(BD ) i*/Zr (BD^K mixed c r y s t a l s a t X, K, and Q bands. Spin Hamiltonian parameters were found by a l e a s t squares f i t of the data. E l e c t r o n i c s p e c t r a of Pa(BHi )i and Pa(BDit)it i n an organic g l a s s were obtained a t 2K from 2200 nm - 300 nm. f

f

t

f

tt

t

t

1+

f

f

4

f

f

R e s u l t s and D i s c u s s i o n The c r y s t a l s t r u c t u r e of 1 1 ( 6 1 1 4 ) 4 has been examined by s i n g l e c r y s t a l x-ray (4b) and neutron d i f f r a c t i o n techniques (4a). Much l i k e the bonding i n the well-known boron hydrides (11), t h i s metal borohydride e x h i b i t s hydrogen b r i d g e bonds that j o i n the boron atom to the metal. I n U ( B H 4 ) i + , there a r e two t r i d e n t a t e and f o u r


334

LANTHANIDE

A N D ACTINIDE

CHEMISTRY

A N D SPECTROSCOPY

Figure 1. Vapor pressure vs. I/T for N p ( B H J ; (O), data of the liquid; (%), data for the solid. 4



2

Ref. 5 d Ref. 4

Ref.

fa

C

1

êf.

3

e

d

0.19/30

insol

-

21 -

slight

49.0 37.7 II. 3 high

3.4

13.0 9.6

19.5

13.6 9.3 4.3 50.0 36.8 13.2 high

2983 10.919

2844 10.719

4264.6 13.354

61.1

4

P43m^ (cubic) monomeric 1.13 28.7 123 15.0/25

u

Zr(BH ) a

2039 8.032

e

P43m (cubic) monomeric I. 85 29.0 118 14.9/25

Hf (BHi»)if

2097 8.247

3

0.05/130

3

P4 2i2 (tetragonal) polymeric 2.69 126^

iKBIUn

Tetrakis-Borohydrides

P4 2i2 (tetragonal) polymeric 2.53 203^

Th(BHit) 4a

W i t h decomposition k Log p(mmHg) = -A/T + B

^Ref. 6

Ref. 7

Heat of sublimation (Kcal/mol) Heat of v a p o r i z a t i o n (Kcal/mol) Heat of f u s i o n (Kcal/mol) Entropy o f sublimation (cal/mol°) Entropy of v a p o r i z a t i o n (cal/mol°) Entropy of f u s i o n (cal/mol°) S o l u b i l i t y i n pentane

Solid* A Solid B

1

Liquid* A Liquid B

1

Solid-state structure Density i n the s o l i d state(gm/cc) M e l t i n g point CC) B o i l i n g p o i n t (°C) extrap. Vapor pressure (mmHg/°C)

C r y s t a l l o g r a p h i c space group

Property

Table 1 P h y s i c a l P r o p e r t i e s of Metal 1+

14.5 8.5 6.0 54.0 33.1 20.9 high

3168 11.80

1858 7.24

P42/nmc (tetragonal) monomeric 2.23 14.2 153 10.0/25

4

Np(BH )

336

LANTHANIDE

AND

ACTINIDE

CHEMISTRY

AND

SPECTROSCOPY


16.

BANKS AND EDELSTEIN

Pa(IV),

Np(IV),

and

Pu(IV)

Borohydrides

337

b i d e n t a t e BH4. groups. The t r i d e n t a t e b r i d g e bond l i n k s the metal atom t o the boron atom through a t r i p l e - h y d r o g e n - b r i d g e bond w h i l e the f o u r t h hydrogen atom forms a t e r m i n a l bond w i t h the boron atom. The b i d e n t a t e b r i d g e bond l i n k s one boron atom t o two metal atoms through two double-hydrogen-bridge bonds, r e s u l t i n g i n a h e l i c a l polymeric s t r u c t u r e . Low-temperature x-ray powder d i f f r a c t i o n photographs(3) o f NpCBHOit and Pu(BHitK r e v e a l e d t h a t they are i s o s t r u c t u r a l and o f a unique s t r u c t u r e type. The s t r u c t u r e o f NpCBIUK was determined by a low-temperature, s i n g l e - c r y s t a l x-ray study a t 130K ( 5 ) . The borohydride molecules are monomeric and c r y s t a l l i z e i n t o the t e t r a g o n a l space group, P42/nmc, where a = 8.559(9) A, c = 6.017(9) A, and Z = 2. The f o u r t e r m i n a l , t r i p l y - b r i d g e d borohydride groups are bound t o the Np atom w i t h Np-B d i s t a n c e s of 2.46(3) A. Although the hydrogen atoms were observed i n the F o u r i e r maps and r e f i n e d , values o f the Np-I^ bond l e n g t h s , 2.2(5) A, had l a r g e standard d e v i a t i o n s . No evidence was found f o r symmetry lower than T f o r Np(BHi )i . The molecular s t r u c t u r e of Np(BHi )i i s i l l u s t r a t e d i n the ORTEP diagram shown i n F i g u r e 2. S t r u c t u r a l s t u d i e s on Zr(BHi )i (6) and Hf(BHt ) (7) have shown t h a t these molecules are monomeric and c r y s t a l l i z e i n t o a c u b i c l a t t i c e w i t h molecular s t r u c t u r e s very s i m i l a r t o those o f Np and Pu borohydrides. Some o f the p h y s i c a l p r o p e r t i e s of metal t e t r a k i s - b o r o h y d r i d e s , which are p r i m a r i l y determined by t h e i r s o l i d - s t a t e s t r u c t u r e , are l i s t e d i n Table 1. The polymeric Th, Pa, and U borohydrides are of much lower v o l a t i l i t y than the monomeric Z r , Hf, Np, and Pu compounds. The i n t e r m o l e c u l a r bonds connecting molecules together decrease t h e i r v o l a t i l i t y s u b s t a n t i a l l y s i n c e these bonds break when the s o l i d v a p o r i z e s (12). A p l o t o f l o g p(mmHg) v s 1/T y i e l d s the equation l o g p(mmHg) = -A/T + B, where T i s i n K. Values o f A and B a l l o w the c a l c u l a t i o n o f the heats (AH) and e n t r o p i e s (AS) f o r phase-change processes as shown i n Table 1. The a c t i n i d e i o n s i n the polymeric compounds are 14 c o o r d i n a t e ; however, i n the gaseous s t a t e they are 12 c o o r d i n a t e (12). The f r e e energy f o r the s t r u c t u r e t r a n s f o r m a t i o n a t 290K d e s c r i b e d by the equation d

t

t

t

f

t

f

t

tt

U(BH0 4 ( s o l i d , 14 c o o r d i n a t e , 4 double hydrogen b r i d g e bonds, 2 t r i p l e - h y d r o g e n - b r i d g e bonds) U(BH)Oi* ( s o l i d , 12 c o o r d i n a t e , 4 t r i p l e hydrogen b r i d g e bonds) can be estimated. AH and AS v a l u e s f o r a 12 c o o r d i n a t e U(BHi )i s t r u c t u r e were obtained by an e x t r a p o l a t i o n o f the measured q u a n t i t i e s f o r Hf(BHi )i and Np(BHi )i v s metal i o n i c r a d i u s . S u b t r a c t i n g these d e r i v e d U(BHt )i values from the corresponding t

t

f

t

f

t

t


t

338

LANTHANIDE

AND

ACTINIDE

CHEMISTRY

AND

SPECTROSCOPY

measured ones gives the heat of t r a n s f o r m a t i o n (4.5 Kcal/mol) and entropy of the t r a n s f o r m a t i o n (6.5 cal/mol degree) of the 14 coo r d i n a t e to the 12 coordinate s t r u c t u r e f o r UCBHOu. Using the equation AG = AH - TAS, AG i s found to be +2.6 Kcal/mol. This value can be compared to the f r e e energy of an exchange process i n v o l v i n g the b r i d g e and t e r m i n a l hydrogen atoms i n s o l u t i o n f o r ( C 5 H 5 ) 3U*BHtt where AG* * 5 Kcal/mol at the coalescence temperature of -140 ± 20° C (13). The c a l c u l a t e d value f o r the spontaneous transformation of the 14 coordinate s t r u c t u r e to the 12 coordinate s t r u c t u r e i s V700K. In a d d i t i o n to low vapor pressure, h i g h m e l t i n g p o i n t s and low s o l u b i l i t y i n noncoordinating organic s o l v e n t s are c h a r a c t e r i s t i c of the polymeric borohydrides. In c o n t r a s t , Zr, Hf, and Np borohydrides melt around room temperature and are h i g h l y s o l u b l e i n pentane. V i b r a t i o n a l Spectroscopy. In s p i t e of t h e i r complex molecu l a r frameworks, the monomeric borohydrides d i s p l a y s u r p r i s i n g l y simple v i b r a t i o n a l s p e c t r a due to t h e i r high symmetry (T

2084

vi

2 V B H

sh on V 5

2

VBH

2

vi ,

vi

2

6HBH,VMH

sh on V ^ ^ v J B

2

strong, broad T o

1205

sh on Vi* , V

1122

v?

1080

v? -vf

478

2

strong, sharp

U

1280 1240

strong

b

6HBH,VMH

B

T

2

vi

2

VMB,

vm^

5

medium, s l . b r . 2

sh on V 6 strong

NpCBDO

1930

V

1922

v?

1605

2vl

1

0

u T sh on V i

2

BD

t

2

VBD x

strong

T

*

1562

V

1

0

BD

medium u on vT sh

2

2

U

D

1558

v?

1526

2

2

*

strong

VBD D

vi

strong,sharp

VBD,

b 6HBD

1190 928

v.weak, b r .

6DBD,VMD,

strong, s l . b r D

845 437

vi

2

v?

2

6DBD,VMD.

weak, b r .

b V M B , VMD, b

strong

In the t a b l e : b r = broad, sh = shoulder, s i = s l i g h t l y , v = very, = b r i d g i n g hydrogen, H = t e r m i n a l hydrogen. (See Appendix f o r d e s c r i p t i o n o f notation) *These two bands are apparently i n Fermi resonance. t


340

LANTHANIDE

Figure 3.

A N D ACTINIDE

CHEMISTRY

AND

SPECTROSCOPY

Gas-phase IR spectra of NpfBH^)^ and 'Np(BDj ) t

h


16.

BANKS AND EDELSTEIN

Pa(IV),

Np(IV),

and

Pu(IV) Borohydrides

341

bands are given i n Table 2. The s o l i d - s t a t e s p e c t r a show many more bands and i t i s from these that a normal coordinate a n a l y s i s was c a r r i e d out. A modified valence f o r c e f i e l d using the f o r c e constants and i n t e r n a l coordinates l i s t e d i n Table 3 gave the c a l c u l a t e d frequencies shown with the corresponding observed ones i n Table 4. The f o r c e constants are very s i m i l a r to those used i n Zr(BH/+)it and Hf (BH l e v e l s as shown i n F i g u r e 4 where A i s assumed p o s i t i v e . The arrows i n F i g u r e 4 represent observed allowed t r a n s i tions. Results of least-squares c a l c u l a t i o n s of the data to the spin-Hamiltonian above are shown i n Table 5. The Np(BHi4) i+/Zr(BHi+) 1+ s p e c t r a gave r e l a t i v e l y broad resonances compared to the deuteride and a r e l i a b l e g^ value could not be found. I n c l u s i o n of a nonzero g-j. value i n the c a l c u l a t i o n s of the deuteride data improved the f i t even though i t was c a l c u l a t e d to be very s m a l l . However, the s i g n i f i c a n c e of t h i s improved f i t must be t e s t e d f u r t h e r . S i m i l a r t r i a l s on the hydride data gave poorer f i t s . The experimental g value i s lower than c a l c u l a t e d from LLW wavefunctions (17) (^2.7), which may i n d i c a t e that covalency (19) or J a h n - T e l l e r (20) e f f e c t s may be important. f

1

F

E l e c t r o n i c Spectra of PaCBHz+K. Cary 17 s p e c t r a of Pa(BHi+K and Pa(BDi4)i+ i n an organic g l a s s at 2K are shown i n Figure 5.



b

3

.26 . 18*

Sl^ME^ ( C )

eH. BMB

2

vMH^:6H^MH^

vBH^ 6 ^ 1 ^ ( i n t r a )

VMB rai^MH^

VMHÎVMF^

VBH^VBHîntra)

I n t e r n a l coordinates

.04

.04

?

solely

-.09 md/rad

.02

.04 md/A

Value

I n t e r a c t i o n Force Constants

* This f o r c e constant was a r b i t r a r i l y s e t at .18 s i n c e t h i s depends almost on the A t o r s i o n mode, which i s not observed.

. 36

t

(S^BR^

.28 mdA/rad

1.28

VMB

6H BH

.37

VM*^

3.51 md/A 2.36

t

Value

VBI^

vBH

I n t e r n a l coordinate

Primary Force Constants

Best F i t Force Constants f o r S o l i d Neptunium Borohydride at 77K

Table 3

16.

BANKS AND EDELSTEIN

Pa(IV),

Np(IV),

and Pu(IV)

Borohydrides

Table 4 Fundamental V i b r a t i o n s (cm ) of Np(BH,), and Np(BD,) Np(BH ) Mode

v

v

Calculated

Observed

Calculated

2551

2557

1912

1911

2143

2144

1548

1603

T 2

2069

2078

1516

1485

2

1247

1266

926

897

T 2

1225

1223

917

895

T 2

1138

1104

860

824

T 2

—

575

437

447

T 2

475

488

—

415

T 2

130

156

112

139

2557

2554

1913

1905

2149

2147

1517

1523

1283

1284

955

953

517

517

475

466

2123

2117

1619

1589

1260

1270

905

899

1053

1089

795

807

—

571

—

413

168

142

154

125

5

v

6

v

7

v

8

v

9

Ai Vi A l

v

2

V s

A

l

E

v,

E v

2

Ti v

2 T

V3

v

L

T l 5

v

P

Observed

3

vj

N (BD )

A2

— — — — — —

405

— — — — —

288

—

2116 1256 1084 565

1587 889 810 405 288 204


343

344

LANTHANIDE

0.00

2.00

4.00

A N D ACTINIDE

6.00

8.00

CHEMISTRY

10.00

A N D SPECTROSCOPY

12.00

14.00

MAGNETIC FIELD (KG) NP(BH4)4

Figure 4. Observed allowed EPR transitions for X band; ( ), K band; (

'Np(BH )i -Zr(BH )i : ), Q band. h

t

Il

l

(— • — •),


16.

BANKS AND EDELSTEIN

Pa(IV),

Np(lV),

and Pu(IV)

Borohydrides

345

Table 5 E l e c t r o n Paramagnetic Resonance of 1

K = A I - S + g6H-S

f

237

Np(BH^)^ and

237

Np(BD^)^

^J^l

- g^H-I

Spin Hamiltonian Parameters 1

|A| (cm ) Np(BH )

g

8

I

4

.1140 ± .001

1.894 ± .002

'U)

Np(BD )^

.1140 ± .001

1.892 ± .002

.0062 ± .002

4

4

Observed and C a l c u l a t e d F i e l d Values (gauss) a t K Band Np(BH ) 4

V = 25.986GHz Observed 6355.6 7295.0 8406.0 9700.0 11177.0 12829.6

Np(BD )

4

Calculated 6355.8 7294.3 8405.7 9700.2 11178.1 12828.7

4

4

v = 24.238GHz Observed 5683.1 6596.0 7695.0 8991.0 10487.6 12167.9

Calculated 5683.1 6595.8 7694.3 8991.4 10487.1 12167.6


346

LANTHANIDE

Figure 5.

A N D ACTINIDE

CHEMISTRY A N D SPECTROSCOPY

Optical spectra of PafBHj,)^ and Fa{BD, ) in methylcyclohexane. S above a peak represents a solvent band. t k


16.

BANKS AND EDELSTEIN

Pa(IV),

Np(IV),

347

and Pu(IV) Borohydrides

In l i q u i d s o l u t i o n a t 25°C, the d i s s o l v e d PaCBH^K i s monomeric and of symmetry. Under these conditions there are f i v e c r y s t a l f i e l d l e v e l s : Γ , Γ , and Γ , Γ ^ , Γ of the F / 2 (ground) and F 7 / 2 levels. Point charge c a l c u l a t i o n s (20) give the Γ ( F 5 / 2 ) l e v e l as the ground s t a t e . K e i d e r l i n g (7b) has observed that when U(BHi )« d i s s o l v e d i n an organic solvent i s cooled to 2K, the monomeric structure transforms back i n t o the polymeric s t r u c t u r e . Although i t i s tempting to assign the observed bands based upon the t e t r a h e d r a l s t r u c t u r e , d e f i n i t e conclusions must await comparison with pure PaiBHit)^ s p e c t r a . Near i n f r a r e d and o p t i c a l s p e c t r a have been obtained f o r 2

7

8

6

5

8

2

8

+

Np(BHO i+ and Np(BDtt) 1+ d i l u t e d

i n ΖΓ(ΒΗ^)^,

Zr(BDttK

+

and methy1-

cyclohexane a t 2K. The s p e c t r a are dominated by v i b r o n i c t r a n s i t i o n s and the a n a l y s i s o f the data i s now underway. Summary The a c t i n i d e borohydrides P a ( B H t ) , Νρ(ΒΗ^Κ, and Pu(BH ) have been synthesized. The s t r u c t u r e of Νρ(ΒΗι+Κ has been studied by s i n g l e - c r y s t a l x-ray d i f f r a c t i o n and found to be s i m i l a r i n s t r u c t u r e to Hf(BHi+K. A normal coordinate a n a l y s i s on ΝρίΒΗι^Κ was completed using IR and Raman s p e c t r a . The e l e c t r o n i c ground s t a t e o f Np(BHit)it has been c h a r a c t e r i z e d by EPR spectroscopy. The e l e c t r o n i c s p e c t r a of Νρ(ΒΗι+) t* and Pa(BH )i are under investigation. t

4

tt

i+

lf

t

Acknowledgment This work was done with support from the D i v i s i o n of Nuclear Sciences, O f f i c e of B a s i c Energy Sciences, U.S. Department o f Energy, under Contract No. W-7405-Eng-48. Literature Cited 1. Hoekstra, H.R.; Katz, J . J . J . Am. Chem. Soc., 1949, 71, 2488. 2a. S c h l e s i n g e r , H.I.,: Brown, H.C. J . Am. Chem. Soc., 1953, 75, 219. 2b. Katz, J . J . ; Rabinowitch, E. "Chemistry of Uranium"; McGrawHill: New York NY, 1951. 3. Banks; R.H.; E d e l s t e i n , N.M.; R i e t z , R.R.; Templeton, D.H.; Z a l k i n , A. J . Am. Chem. Soc, 1978, 100, 1975. 4a. B e r n s t e i n , E.R.; Hamilton, W.C.; K e i d e r l i n g , T.A.; LaPlaca, S.J.; Lippard, S.J.; Mayerle, J . J . Inorg. Chem., 1972, 11, 3009. 4b. B e r n s t e i n , E.R.; K e i d e r l i n g , T.A.; Lippard, S.J.; Mayerle, J . J . J . Am. Chem. Soc., 1972, 94, 2552. 5. Banks, R.H.; E d e l s t e i n , N.M.; Spencer, B.; Templeton, D.H.; Z a l k i n , A. J . Am. Chem. Soc., 1980, 102, 0000. 6. B i r d , P.H.; C h u r c h i l l , M.R. Chem. Comm., 1967, 403.


LANTHANIDE AND ACTINIDE CHEMISTRY AND SPECTROSCOPY

348

7a. Broach, R.S.;Chuang, I.S.; W i l l i a m s , J.M.; Marks, T . J . P r i v a t e communication, 1979. 7b. K e i d e r l i n g , T.A. PhD t h e s i s , P r i n c e t o n U n i v e r s i t y , 1974. 8. B e r n s t e i n , E.R.; K e i d e r l i n g , T.A. J . Chem. Phys., 1973, 59, 2105. 9. Maybury, P.C.; Larrabee, J.C. A b s t r a c t o f papers, 135th Meeting of the American Chemical S o c i e t y , 1959. P-28M. 10. Banks, R.H.; E d e l s t e i n , N.M., to be p u b l i s h e d . 11. M u e t t e r t i e s , E.L. "Boron Hydride Chemistry"; Academic P r e s s : New York NY, 1975. 12. James, B.D.; Smith, B.E.; Wallbridge, M.G.H. J . Mol. S t r u c t . 1972, 14, 327. 13. Marks, T.J.; Kolb, J.R. J . Am. Chem. Soc., 1975, 97, 27. 14. Smith, B.E.; S h u r v e l l , H.F.; James, B.D. JCS Dalton, 1978, 710. 15. K e i d e r l i n g , T.A.; Wozniak, W.T.; Gay, R.S.; Jurkowitz, D.; B e r n s t e i n , E.R.; L i p p a r d , S.J.; S p i r o , T.G. Inorg. Chem., 1975, 14, 576. 16. P r i c e , W.C. J . Chem. Phys., 1948, 16, 894. 17. Emery, A.R.; T a y l o r , R.C. J . Chem. Phys., 1958, 28, 1029. 18. Bleany, B. Proc. Roy. Soc. Lond., 1964, A277, 289. 19. Judd, B.R. 2nd I n t e r . Conf. on E l e c t r o n i c S t r u c t u r e o f An, Warsaw, Poland, 1976. 20. Lea, K.R.; Leask, M.J.M.; Wolf, W.P. J . Phys. Chem. S o l i d s , 1962, 23, 1381. Appendix In Tables 2 and 4, a fundamental or overtone i s denoted by the symbol nV^, where b i s the M u l l i k e n symbol f o r the i r r e d u c i b L r e p r e s e n t a t i o n of the mode and a i s the number of the mode s t a r t i n g w i t h 1 f o r the highest frequency, 2 f o r the second h i g h e s t , e t c . The n i s omitted f o r fundamentals, equals 2 f o r f i r s t overtones, 3 f o r second overtones, e t c . The t a b l e given below r e l a t e s our n o t a t i o n to that used i n e a r l i e r work (7b,15). This work

Literature Vi

-

v

-

6

v

h

Vio

V n -

Vis

Vie-

V if 2

RECEIVED January 7, 1980.


Neptunium(IV), and Plutonium (IV) Borohydrides - American Chemical

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