HANDLING AND USES OF THE ALKALI METALS

Uses of Lithium Metal W A L T E R M. F E N T O N , D O N A L D L. E S M A Y , R O N A L D L. L A R S E N , a n d HERBERT H . S C H R O E D E R

Downloaded by UNIV OF OKLAHOMA on October 28, 2014 | http://pubs.acs.org Publication Date: January 1, 1957 | doi: 10.1021/ba-1957-0019.ch003

Lithium C o r p . o f A m e r i c a , Inc., M i n n e a p o l i s , Minn.

Lithium metal m a y be u s e d as an a l k y l a t i n g agent in Grignard-type reactions in the production of synthetic vitamin A and other pharmaceutical products, as an ionic catalyst in new polymer technology, as a direct reducing agent in certain organic reactions, as a flux in new brazing techniques, as a starting point in production of metallic hydrides and borohydrides, and as a potential heat-transfer agent in new engineering developments.

L I T H I U M is the first element i n G r o u p I of the periodic table a n d hence is a u t o m a t i c a l l y classed as a n a l k a l i m e t a l . Nevertheless, a study of the p e c u l i a r a n d i n d i v i d u a l characteristics w h i c h m a k e possible some of the n e w e r uses of l i t h i u m shows that i n b e h a v i o r , at least, this element m o r e f r e q u e n t l y resembles the e l e ments of G r o u p s II a n d III. A l t h o u g h this paper deals p r i m a r i l y w i t h the metal, it refers b r i e f l y to c e r tain uses of the salts of l i t h i u m . T h i s w i l l serve to u n d e r l i n e the properties w h i c h resemble those of the G r o u p II o r G r o u p III elements. T o cite a f e w examples, l i t h i u m soaps used as g e l l i n g agents i n the n e w m u l t i p u r p o s e l u b r i c a t i n g greases are w a t e r - i n s o l u b l e w i t h w i d e ranges of t h e r m a l stability, thus r e s e m b l i n g b a r i u m a n d a l u m i n u m soaps rather t h a n their s o d i u m or potassium counterparts. I n the field of a i r conditioning, l i t h i u m c h l o r i d e a n d l i t h i u m b r o m i d e have f o u n d use b e cause of the hygroscopic nature of these two h a l i d e s — a g a i n a characteristic of G r o u p II halides. L i t h i u m halides e x h i b i t covalent tendencies as s h o w n b y t h e i r s o l u b i l i t y i n polar organic solvents, a p r o p e r t y generally true of elements i n G r o u p s II a n d III. I n r e v i e w i n g patents w h e r e l i t h i u m is r e f e r r e d to b y name, the element is g e n e r a l l y m e n t i o n e d as part of a group, the u s u a l clause b e i n g " a n element (or a salt, or a metal) selected f r o m the group consisting of s o d i u m , potassium, o r l i t h i u m . " I n almost e v e r y instance, the applicant proceeds to cite a n e x a m p l e of the reaction or process u s i n g a s o d i u m o r potassium salt. L i t h i u m is thereby i n c l u d e d i n the patent claims b y inference o n l y . T h i s conjecture c a n sometimes p r o v e erroneous, as i n so m a n y instances l i t h i u m w i l l not necessarily behave i n the same m a n n e r as its c o m p a n i o n elements i n G r o u p I. No lithium outline unique

attempt is m a d e here to catalog a l l the applications of l i t h i u m , w h e r e i n differs i n its b e h a v i o r f r o m the other m e m b e r s of G r o u p I. A f e w examples the m o r e i m p o r t a n t applications of l i t h i u m m e t a l , based l a r g e l y o n certain characteristics.

Production A short r e v i e w of the m e t h o d of extracting the l i t h i u m f r o m its salts m a y give a better u n d e r s t a n d i n g of the b e h a v i o r of the m e t a l . T h e m e t a l is obtained b y passing a c u r r e n t t h r o u g h a m o l t e n b a t h of l i t h i u m c h l o r i d e containing a m i n o r 16

In HANDLING AND USES OF THE ALKALI METALS; Advances in Chemistry; American Chemical Society: Washington, DC, 1957.

FENTON, ESMAY, LARSEN AND SCHROEDER—USES OF LITHIUM METAL

17

percentage of potassium chloride. T h e latter serves to effect a l o w e r i n g of the m e l t i n g point of the l i t h i u m salt. T h e anodes are graphite rods, a n d t h e cathodes are c o n v e n t i o n a l steel structures. A c u r r e n t of 10,000 amperes is i n t r o d u c e d to the anodes at 5 to 6 volts. A s the l i t h i u m c h l o r i d e is electrolyzed, the elemental metal, h a v i n g a specific g r a v i t y of o n l y 0.5, floats to the top of the m o l t e n bath, f r o m w h i c h it is p e r i o d i c a l l y l a d l e d and p o u r e d into cooling molds. These ingots are then r e melted to r e m o v e occluded salts. W h e r e forms other t h a n the ingot are r e q u i r e d , the m e t a l is r e w o r k e d b y extrusion, r o l l i n g , o r casting.


Lithium in Organic Synthesis E x c e p t i n the field of organometallic chemistry, there has been considerably less interest i n l i t h i u m m e t a l than i n metallic s o d i u m or potassium. O n e reason m a y be the previous l a c k of a v a i l a b i l i t y of l i t h i u m m e t a l i n p h y s i c a l forms s u i t able for l a b o r a t o r y - s c a l e investigations. A s these forms have become available w i t h i n recent years, there has been a n obvious increase i n e x p e r i m e n t a l w o r k done w i t h l i t h i u m metal. T h e first paper of r e c o r d o n o r g a n o l i t h i u m c h e m i s t r y was p u b l i s h e d i n 1910 (33), a n d it was 7 years before a second paper appeared (25). F o l l o w i n g these, a f e w papers appeared f r o m time to time, b u t i t was n o t u n t i l the e a r l y 30's that extensive w o r k was b e g u n o n l i t h i u m m e t a l i n organic systems. ALKYLATING AGENT IN GRIGNARD-TYPE REACTIONS IN PRODUCTION OF SYNTHETIC VITAMIN A AND OTHER PHARMACEUTICAL PRODUCTS. In r e v i e w i n g the p r e p a r a t i o n a n d reactions of o r g a n o l i t h i u m compounds, l i t h i u m is observed as the first m e m b e r of a group i n the periodic system a n d follows the general r u l e f o r such elements—that is, its properties are intermediate between those of the other a l k a l i metals i n G r o u p I and those of m a g n e s i u m a n d the a l k a l i n e earth metals i n G r o u p II. A s a result of extensive investigations b e g i n n i n g about 25 years ago, p a r t i c u l a r l y w o r k done b y G i l m a n a n d coworkers, the p r e p a r a t i o n of o r g a n o l i t h i u m compounds c a n n o w be r e a d i l y c a r r i e d out i n a m a n n e r analgous to that for p r e p a r i n g G r i g n a r d r e agents—i.e., b y reaction of the m e t a l w i t h the desired organic halide i n simple equipment. T h i s is s h o w n b y the f o l l o w i n g general reaction w h e r e R X is a n a l k y l or a r y l halide (14): RX

+ 2 Li

> RLi + LiX

P r e p a r a t i o n of o r g a n o s o d i u m a n d organopotassium compounds b y this p r o cedure is u s u a l l y unsuccessful, o w i n g to the fact that the W u r t z - t y p e c o u p l i n g reaction occurs p r e f e r e n t i a l l y . I n addition, the o r g a n o l i t h i u m compounds are s o l u ble i n ether a n d quite stable t h e r m a l l y , i n contrast to the organosodium a n d o r ganopotassium compounds w h i c h are insoluble i n ether a n d r e l a t i v e l y unstable. N o t o n l y do the properties of o r g a n o l i t h i u m compounds differ w i d e l y f r o m those of the compounds of the other a l k a l i metals, b u t they also differ f r o m the properties of the compounds of G r o u p II metals. F o r example, o r g a n o l i t h i u m compounds a d d to certain olefinic linkages whereas o r g a n o m a g n e s i u m compounds do not. T h u s , o r g a n o l i t h i u m compounds f o r m a u n i q u e class of organometallic compounds. P r o b a b l y the most useful reaction w h i c h o r g a n o l i t h i u m compounds undergo c a n be t e r m e d b r o a d l y a l k y l a t i o n o r a r y l a t i o n (14). T h i s is s h o w n i n the f o l l o w i n g t y p i c a l reaction of a ketone w i t h a n o r g a n o l i t h i u m c o m p o u n d to y i e l d the l i t h i u m salt of a t e r t i a r y a l c o h o l : R C = Ο + R'Li 2

> RsR'COLi

S i m i l a r reactions occur w i t h m a n y other types of compounds c o n t a i n i n g u n s a t u r ated l i n k a g e s — f o r e x a m p l e , aldehydes, esters, a n d nitriles. It is most convenient first to prepare the o r g a n o l i t h i u m c o m p o u n d separately, then combine it w i t h the m a t e r i a l to be a l k y l a t e d . A n e x a m p l e of this p r o c e d u r e is s h o w n b y the p r e p a r a t i o n of m e t h y l l i t h i u m ( C o m p o u n d I) f r o m m e t h y l iodide a n d l i t h i u m . Subsequent reaction of /9-ionylidenecrotonic acid w i t h the m e t h y l l i t h i u m f o l l o w e d b y h y d r o l y s i s yields C o m p o u n d II. CH I + 2Li 3

CHaLi + L i l I


A D V A N C E S IN CHEMISTRY SERIES

18

CH, CH, \ / H

2

C ^

C

"

ÇH,

C- C H = C H - C =CH-CHCOOH

»>

I

I H,C

»

,

L i

(2) H 0 2

/ C - C H ; I

CH,

H,

\ /

^ l o n y l i d e n e c r o t o n i c acid

H

^ -

Ί

C

CH, C H ,

CH

: i

^ C - C H = C H - C = C H - C H = C H c (

I

H,C


C H

C - C H ,

C I H

Π

2

T h i s is the reaction used i n the V a n D o r p - A r e n s p r e p a r a t i o n of a synthetic v i t a m i n A (34). S i m i l a r types of syntheses are c o m m o n l y used for the p r e p a r a t i o n of c o m pounds of interest for their possible p h y s i o l o g i c a l action. F o r example, M o r g a n a n d coworkers (24) recently described the use of a r y l l i t h i u m compounds i n the p r e p a r a t i o n of some stilbestrol analogs. T h e general procedure is s h o w n b y the reaction of e t h y l a - ( p - a n i s y l ) p r o p y l ketone w i t h a n a r y l l i t h i u m c o m p o u n d to y i e l d a l i t h i u m salt of a tertiary alcohol, w h e r e A r = — C H , 6

—

F

,

5

a n d other radicals:

C H C H /—λ \ I MeO—(' V - C H - C = 0 2

Ethyl a-(p-anisyl)

5

2

5

C H I )—CH 2

/r~\

+

ArLi

—>

MeO—('

X

p r o p y l ketone

C2H5 I C — A r

5

O - L i

I n a d d i t i o n to the c a r b o n alkylations g i v e n above it has been f o u n d possible to a l k y l a t e atoms other t h a n c a r b o n w i t h the a i d of o r g a n o l i t h i u m compounds. F o r example, the general reaction of a silicon tetrahalide w i t h an o r g a n o l i t h i u m c o m p o u n d has been w i d e l y used as a m e t h o d for p r e p a r i n g organosilicon c o m pounds (13): SiX, +

4RLi

> R,Si +

4LiX

T h e direct a l k y l a t i o n of a m m o n i a a n d amines w i t h olefins i n the presence of a l k a l i metals as catalysts was r e p o r t e d b y H o w k a n d coworkers (17). T h e general procedure is s h o w n i n the f o l l o w i n g reaction, where R c a n be a h y d r o g e n atom or an a l k y l or a r y l g r o u p : RNH

2

+ R'CH = C H > H N (CH CH R')R K , N a , or L i 2

2

2

T h i s reaction is p o t e n t i a l l y v e r y interesting f r o m a c o m m e r c i a l standpoint. A l t h o u g h these w o r k e r s used s o d i u m i n most of their experiments, a few c o m p a r a tive runs are r e p o r t e d i n w h i c h l i t h i u m was used as the catalyst. T h e results were interpreted to show that i n the a l k y l a t i o n of a m m o n i a w i t h ethylene, s o d i u m a n d l i t h i u m gave about the same catalytic action. NH

3

+ CH = CH 2

2

> C H5NH + 2

2

(C,H ) NH + (C H ) N 5

2

2

5

3

H o w e v e r , i n the reaction of d i e t h y l a m i n e w i t h ethylene, l i t h i u m catalyzed f o r m a tion of t r i e t h y l a m i n e almost e x c l u s i v e l y , whereas the m a j o r p o r t i o n of the p r o d ucts f r o m the same reaction w i t h s o d i u m o r potassium as catalyst consisted of materials h i g h e r b o i l i n g t h a n t r i e t h y l a m i n e .


FENTON, E S M A Y, LARSEN AND SCHROEDER—USES OF LITHIUM METAL

Li (C H ) NH + C H = C H 2

5

2

2

(C H } N 2

5

3

19

(only)

2

Na

(C Hs).3N + 2

higher boiling materials


A related noncatalytic a l k y l a t i o n of the nitrogen atom is shown b y the f o l l o w i n g reaction of b e n z y l p h e n y l a m i n e w i t h / 3 - d i m e t h y l a m i n o e t h y l chloride i n the presence of l i t h i u m amide to y i e l d N - b e n z y l - i N T - p h e n y l - N ' ^ N ' - d i m e t h y l - l ^ - d i a m inoethane:

T h e substituted ethylenediamine product is a n antihistamine agent. M a n y other examples of the use of l i t h i u m a n d its compounds as a l k y l a t i n g or a r y l a t i n g catalysts or agents i n organic synthesis could be g i v e n . H o w e v e r , the above examples serve to point out the general principles i n v o l v e d . IONIC CATALYST IN NEW POLYMER TECHNOLOGY. T h e use of a l k a l i metals or their compounds as catalysts for the p o l y m e r i z a t i o n of conjugated diolefins has been practiced for m a n y years. A s is w e l l k n o w n , the name " b u n a " was given to the r u b b e r obtained b y p o l y m e r i z i n g butadiene w i t h n a t r i u m ( s o d i u m ) . Patents a n d articles o n this type of p o l y m e r i z a t i o n have u s u a l l y r e f e r r e d to the a l k a l i metals as a group of suitable catalysts. H o w e v e r , research w o r k e r s at Firestone have recently f o u n d that finely dispersed l i t h i u m is a specific a n d u n i q u e catalyst for the p o l y m e r i z a t i o n of isoprene to a n a t u r a l - t y p e r u b b e r . T h i s serves once again to point out the dangers i n v o l v e d i n p r e d i c t i n g properties for l i t h i u m or its c o m pounds based o n a knowledge of s o d i u m (or potassium) a n d its compounds. W h i l e predictions of general properties are u s u a l l y satisfactory, care must be exercised i n translating results w i t h s o d i u m to predictions for l i t h i u m i n specific instances. T h e use of l i t h i u m or o r g a n o l i t h i u m compounds as catalysts for the p o l y m e r i z ation or copolymerization of mono-olefins is likewise not n e w . F o r example, E l l i s ' patent (10) covers the addition of a n o r g a n o a l k a l i m e t a l c o m p o u n d , such as n - b u t y l l i t h i u m , to a h y d r o g e n a t i n g catalyst, such as reduced n i c k e l - o n - k i e s e l g u h r , to y i e l d a system capable of catalyzing the p o l y m e r i z a t i o n of ethylene. S o l i d p o l y mers are f o r m e d at temperatures of only 50° to 150 ° C . a n d pressures of o n l y 1000 to 2000 pounds p e r square i n c h gage. H a n f o r d a n d coworkers (15) patented the p o l y m e r i z a t i o n of ethylene to solid materials u n d e r essentially the same c o n d i tions, u s i n g o n l y o r g a n o l i t h i u m compounds as catalysts. A s this latter patent claims o n l y o r g a n o l i t h i u m compounds, a n d not o r g a n o a l k a l i m e t a l compounds i n general, a p p a r e n t l y the p o l y m e r i z i n g action is specific to the l i t h i u m compounds. So far, the discussion has covered the use of l i t h i u m or l i t h i u m compounds as catalysts for the p o l y m e r i z a t i o n of olefins or diolefins to solid p o l y m e r s only. H o w e v e r , it is also possible to p o l y m e r i z e olefins to l i q u i d p o l y m e r s using c a t a lysts comprised, i n part, at least, of l i t h i u m compounds. Ziegler a n d his coworkers (52) reported o n the reactions of l i t h i u m a l u m i n u m h y d r i d e w i t h mono-olefins to f o r m l i t h i u m a l u m i n u m t r i c y c l o a l k y l hydrides, l i t h i u m a l u m i n u m tetraalkyls, a n d so o n . A c c o r d i n g to a later patent (51), such l i t h i u m a l u m i n u m compounds c a n be used as catalysts for the p o l y m e r i z a t i o n of ethylene to p o l y m e r s r a n g i n g f r o m butene to w a x - r a n g e solids. A l t h o u g h this is b y no means a complete s u r v e y of the use of l i t h i u m a n d its compounds as p o l y m e r i z a t i o n catalysts, it points out that l i t h i u m has been used


A D V A N C E S IN

20

CHEMISTRY SERIES

successfully as a p o l y m e r i z a t i o n catalyst. I n addition, l i t h i u m was completely u n i q u e i n its action i n several instances. W i t h these observations as starting points, the use of l i t h i u m as a p o l y m e r i z a t i o n catalyst w i l l c e r t a i n l y be more extensively investigated i n the future. DIRECT REDUCING AGENT IN CERTAIN ORGANIC REACTIONS.

T h e use of l i t h i u m a l u m -


i n u m h y d r i d e as a selective r e d u c i n g agent has enjoyed tremendous p o p u l a r i t y i n the laboratory, since its d i s c o v e r y was r e p o r t e d b y Schlesinger a n d coworkers i n 1947 (11). T h e use of l i t h i u m a l u m i n u m h y d r i d e reductions has become so w e l l k n o w n that little i n the w a y of elaboration is needed here. T h e use of l i t h i u m i n a m m o n i a (47), low m o l e c u l a r weight amines (4), a n d e t h y l e n e d i a m i n e (35) as a selective a n d u n i q u e r e d u c i n g agent has r e c e i v e d c o n s i d erable study i n the past few years. T h e r e p o r t e d results point out once again that w h i l e s o d i u m a n d l i t h i u m can g e n e r a l l y be classed together as far as o v e r - a l l r e actions go, w h e n it comes to the fine points, considerable differences c a n be e x pected. F o r e x a m p l e , B e n k e s e r a n d coworkers r e p o r t e d recently (5) that l i t h i u m i n e t h y l a m i n e reduces naphthalene to the isomeric A - a n d A - O c t a l i n , w h e r e as s o d i u m i n a m m o n i a reduces it to T e t r a l i n : M 0

i e

N a in N H j

C'

Tetralin

L i in EtNHs

A -Octalin

A^-Octalin

1 9

T h e scope of the use of l i t h i u m i n amines as a r e d u c i n g agent has been extended r e c e n t l y (3) to i n c l u d e the r e d u c t i o n of f u n c t i o n a l groups, s u c h as keto a n d n i t r i l e groups. T h e f o l l o w i n g reactions illustrate the courses of the reductions: H

I

Li

C-CH I OH

CHjNH.

0

1-Cyclohexenylmethyl carbinol

Acetophenone ^ ~ ^ - C H

2

C N

Benzylcyanide

CHJNHÏ

3

^ ^ - C H

2

C H

2

N H

2

j9-(l-Cyclohexenyl) ethylamine

+

S y-

CH CH NH 2

2

2

/3-Cyclohexylethylamine

T h e successful r e d u c t i o n of f u n c t i o n a l groups thus considerably extends the scope a n d usefulness of these u n i q u e l i t h i u m - a m i n e r e d u c i n g systems.

Metallurgical Applications of Lithium A l t h o u g h l i t h i u m m e t a l has b e e n a v a i l a b l e for 60 years, v e r y little use has been made of it i n m e t a l l u r g i c a l applications u n t i l recently. T h e first r e p o r t e d use was i n 1918, w h e n G e r m a n metallurgists u t i l i z e d it as a n a l l o y i n g element i n the p r o d u c t i o n of S c l e r o n , a n a l u m i n u m - z i n c a l l o y c o n t a i n i n g 0.1% l i t h i u m . S t a r t i n g i n the late thirties, a l i m i t e d c o m m e r c i a l use was m a d e of l i t h i u m i n the degasification of copper c a s t i n g s — a s o - c a l l e d " l i t h i u m - c o p p e r a l l o y " b e i n g used. I n r e a l i t y , this was a copper ingot w i t h l i t h i u m particles dispersed t h r o u g h o u t — t h e ratio b e i n g 98% copper a n d 2% l i t h i u m . Subsequently, l i t h i u m - c o p p e r cartridges were substituted for the " a l l o y . " T h e s e cartridges consist of a specific


FENTON, ESMAY, LARSEN A N D

21

SCHROEDER—USES OF LITHIUM METAL


weight of l i t h i u m m e t a l sealed i n t h i n - w a l l e d copper t u b i n g (22). T h e f u n c t i o n of the l i t h i u m is to react w i t h the gases ( p r i m a r i l y o x y g e n a n d occasionally h y d r o g e n a n d nitrogen) absorbed i n the m o l t e n c o p p e r - b e a r i n g a l l o y . C a r t r i d g e a d d i t i o n is made about 3 minutes before p o u r i n g into the m o l d . In this w a y a denser casting is obtained b y the e l i m i n a t i o n of p i n h o l e porosity. A c c o r d i n g to the best i n f o r m a t i o n available, between 30,000,000 a n d 50,000,000 pounds of nonferrous castings were p r o d u c e d i n 1955 using this method of degasification. T h e success of this a p p l i c a t i o n l e d to a serious study of the m e t a l l u r g i c a l applications of l i t h i u m . T h e most recent w o r k is that of B r e d z s a n d C a n o n i c o (6) i n the development of self-fluxing metals a n d alloys for the b r a z i n g o f a l l o y steels. O r i g i n a l l y , l i t h i u m was studied as a n a l l o y i n g element to reduce the m e l t i n g point of the b r a z i n g alloy, thus increasing its fluidity. I n the course of the i n vestigation, it was f o u n d that the l i t h i u m h a d a strong d e o x i d i z i n g effect o n the oxide coating of the steel, thus increasing the wetting character of the alloy. Subsequent investigation r e v e a l e d that the fluxing effect of the l i t h i u m was sufficient to e l i m i n a t e the n e e d for c h e m i c a l fluxes a n d i n some cases inert atmospheres c o m m o n l y used. T h u s the w o r k to date has s h o w n that l i t h i u m is the most s u i t able m e t a l for d e v e l o p i n g s e l f - f l u x i n g b r a z i n g alloys.

Lithium Hydride as a Starting Point in Production of Simple and Complex Hydrides T h e importance of l i t h i u m h y d r i d e i n the p r o d u c t i o n of simple a n d c o m p l e x h y d r i d e s is dependent u p o n certain u n i q u e properties. F o r example, according to H u r d (19), it is the v e r y slight solubility of l i t h i u m h y d r i d e i n p o l a r organic compounds as w e l l as the a b i l i t y to sustain metathetical reactions that provides for the p r o d u c t i o n of n u m e r o u s h y d r i d e s . T h i s is true for l i t h i u m h y d r i d e , whereas the other a l k a l i a n d a l k a l i n e earth m e t a l h y d r i d e s are insoluble i n p o l a r organic solvents, a n d their metathetical reactions do not proceed at a l l or at a slow rate at best (19,29). G r e a t e r use of l i t h i u m h y d r i d e is possible i n such reactions because of its l o w dissociation pressure at its m e l t i n g point of 680 ° C . W i t h the p r e p a r a t i o n of l i t h i u m a l u m i n u m h y d r i d e , Schlesinger a n d coworkers not o n l y opened w i d e fields of w o r k i n organic c h e m i s t r y , b u t p r o v i d e d i m p r o v e d methods for the p r e p a r a t i o n of m a n y h y d r i d e s (11). I n general, the reaction of l i t h i u m h y d r i d e o r l i t h i u m a l u m i n u m h y d r i d e to f o r m other h y d r i d e s is a m e t a thesis of the f o l l o w i n g f o r m , w h e r e a m e t a l h y d r i d e reacts w i t h the salt of a n other m e t a l to give a m e t a l - m e t a l interchange: MH

+

NX

> MX +

NH

In this reaction M is m o r e electropositive t h a n N , a n d X is m o r e t h a n h y d r o g e n . A specific e x a m p l e of s u c h a r e a c t i o n is (45): 3LiH +

InCl*

> 3LiCl +

electronegative

InHa

Et.O I n addition, l i t h i u m a l u m i n u m h y d r i d e also lends itself to stepwise r e d u c t i o n (19), w h i c h facilitates synthesis of c o m p l e x h y d r i d e s . T h e general reaction for this type of synthesis is as follows: 4MX + LiAlH* 4MH«-,X + L i A l H * n

>4MHX -i + L i X + A 1 X >4MH« + L i X + A1X3 n

3

T a b l e I lists some of the h y d r i d e s that have been p r e p a r e d u s i n g l i t h i u m h y dride and lithium a l u m i n u m hydride.

Table I. Hydrides Synthesized through Use of Lithium Hydride and Lithium Aluminum Hydride Hydride LiGaH* M g H a (-TiLiH) SiH* ThHeorThH* ZnH ZnHI 2

Lit. (11.20,45) (45) (12) (8) (41) (41)

Hydride Lithium Hydride AIHa B He BeH2 InHs ( L i H ) L i (BHsCN) L1BH4 ( E t a O ) 2

Lit. (11) (7,27,28) (2,36,38) (45) (50) (9,16,26,27,29,48,49)


ADVANCES

22

IN CHEMISTRY SERIES

Table I. (Continued) Lithium Aluminum Hydride (42) (11) (19) (2,36,38) (1) (1,40) (42) (31,36,45) (45) (12) (40) (31,36, 45) (45)

AgAlH* AI(BH4) AsHa Be(AlH ) B e H (-nEt20) CdH CuH GaiAlHOs GaHa GeH* HgH In(AlH4) InH 3

4

2

2

2

2

3

3

(31,36) (37) (1) (19) (12) (12) (39) (12) (44) (46) (32,36,46) (1,43)

LiGaH4 Mg(AlH4) M g H (-nEt 0) SbH Si H S1H4 Sn(AlH )4 SnH4 Ti(AlH4) T1(A1H4) Tl(GaH4)s ZnH 2

2

2

a

2

6

4

4

3

2


T h i s table includes references to preparations of inorganic h y d r i d e s only, b u t it c o u l d be extended to include references to preparations of organometallic h y d r i d e s (1,11,12,19). T h e f o l l o w i n g are examples of such reactions: (C H ) SiCl + Diethylsilicon dichloride 2

5

2

2

2LiH

> (C H ) SiH + 2LiCl Dioxane Diethylsilane 2

2(n-Pr) SiCL + L1AIH4 D i - n - p r o p y l s i l i c o n dichloride 2

5

2

2

> 2 (n-Pr) SiH + LiCl Di-n-propylsilane 2

EUO

2

+ A1CL

M a n y other h y d r i d e s c a n feasibly be p r e p a r e d t h r o u g h the use of l i t h i u m h y d r i d e a n d l i t h i u m a l u m i n u m h y d r i d e as w e l l as other c o m p l e x h y d r i d e s — e . g . , L i B H * (27, 30, 36, 50) a n d L i G a H 4 (36).

Potentialities of Lithium Metal as a Heat Transfer Agent in New Engineering Developments In a n effort to detail the properties of l i t h i u m metal i n its m o l t e n state, the authors have recorded i n T a b l e II certain pertinent facts concerning the metal a n d

Table II. Physical Properties of Metals and Water'

Lithium Sodium Sodium-potassium, 44% potassium Lead Mercury Water Bismuth Lead-bismuth, 55.5% bismuth

Density, G./Cc. (800 °C.) 0.46 (700°C.) 0.78 (700 °C.) 0.70 (800 °C.) 10.04 (300 °C.) 12.88 (4°C.) 1.0 (800 °C.) 9.40 (800°C.) 9.64

Melting Point, °C. 179 98

-11

Boiling Point, °C. 1317 883 784

327 -39 0 271 125

1737 357 100 1477 1670

Latent Heat of Fusion, Cal./G. 158 27

Heat Thermal Viscosity, Capacity, Conductivity, C a l . / G . °C. Cal./Sec.-Cm.°C. Cp. 1.0 (980°C.) 0.41 0.09 Lithium 0.31 0.16 (700°C.) 0.18 Sodium 0.21 Sodium-potassium, 0.06 (700°C.) 0.15 44% potassium Lead 0.037 0.036 (845°C.) 1.19 Mercury 0.032 0.03 (200°C.) 1.0 Water 1.0 0.001 (100°C.) 0.28 Bismuth 0.04 0.037 (600°C.) 1.0 Lead-bismuth, 0.035 0.026 (600°C.) 1.17 55.5% bismuth " A l l data except water t a k e n f r o m (23, pp.40-4). Estimated.

V o l . Change on F u s i o n , % of S o l i d Volume 1.5 2.5 2.5

Latent Heat of Vaporization Cal./G. 4680 1005

3.6 3.6 -8.3 -3.3 0.0

205 70 540 204

5.8 2.8 79 12.0

Temp, for 10 M m . H g . Vapor Pressure, °C. 890 548 458 1167 184 11 1067 1100

h

Electrical Resistivity, Atohms (230°C.) 45.3 (300 °C.) 16.7 (200 °C.) 47.0 (327°C.) 94.6 (300°C.) 127.5 (300 °C.) 128.9 (300°C.) 118.0

b

p h y s i c a l characteristics that m a y have a b e a r i n g o n its heat transfer properties. T h e v a l u e of l i t h i u m as a heat transfer l i q u i d is dependent u p o n certain p h y s i c a l a n d c h e m i c a l properties w h i c h are r e l a t i v e l y superior to those of other metals a n d alloys. A study of T a b l e II reveals that l i t h i u m compares v e r y f a v o r a b l y w i t h the other materials i n the table. I n fact, i n not one category is the v a l u e of l i t h i u m such that it w o u l d be considered objectionable.



FENTON, ESMAY, LARSEN A N D SCHROEDER—USES OF LITHIUM METAL

23

L i t h i u m has a l o w m e l t i n g point ( 1 7 9 ° C . ) a n d h i g h b o i l i n g point ( 1 3 1 7 ° C ) , g i v i n g it a l i q u i d operating range of over 1000°C. T h u s , it c o u l d be used as a coolant f r o m at least 200° to 1200 ° C . at atmospheric pressure. L i t h i u m has the lowest density of a n y m e t a l a n d therefore the c i r c u l a t i n g weight of l i q u i d m e t a l i n a cooling system c a n be kept at a m i n i m u m . H i g h fluid velocities c a n be e m p l o y e d because of this l o w density. T h e heat capacity of l i t h i u m is m u c h greater than a n y of the other metals listed i n T a b l e II a n d it is the only m e t a l w i t h a v a l u e near or e q u a l to that of water. T h i s w o u l d serve to reduce the v o l u m e a n d weight of coolant r e q u i r e d i n the entire system. T h e latent heat of v a p o r i z a t i o n is h i g h c o m p a r e d to those other metals s h o w n i n T a b l e II, a n d this w o u l d serve to reduce the possibility of b o i l i n g at " h o t spots" i n the system. A m o n g the more c o m m o n metals, the t h e r m a l c o n d u c t i v i t y of l i t h i u m m e t a l is second only to that of sodium. T h e latent heat of fusion is e x t r e m e l y h i g h , r e d u c i n g somewhat the possibility of solidification i n instances where a s m a l l heat loss occurs near the m e l t i n g point. T h e viscosity of l i t h i u m m e t a l is about a v e r age for those metals s h o w n i n T a b l e II, a n d t h e v o l u m e change o n fusion is l o w e r t h a n average (about 1.5%). T h e electrical resistivity is higher t h a n that of s o d i u m but lower than that of a n y of the other metals s h o w n i n T a b l e II. B a s e d o n p h y s i cal properties alone, l i t h i u m w o u l d appear to have no e q u a l as a l i q u i d metal coolant. H o w e v e r , the p r i n c i p a l disadvantages at present to the use of l i q u i d l i t h i u m as a coolant appear to arise f r o m c h e m i c a l properties. A r e v i e w of the p u b l i s h e d l i t erature reveals that l i q u i d l i t h i u m is h i g h l y corrosive. H o w e v e r , these data are subject to question, i n v i e w of the fact that the amount of contained impurities was not accurately reported. L i t h i u m is h i g h l y reactive w i t h most of the m a j o r constituents of the s u r r o u n d i n g a t m o s p h e r e — o x y g e n , nitrogen, a n d water. T h e l i t h i u m compounds of these elements therefore a r e u s u a l l y present i n l i t h i u m as i m p u r i ties. A l l of these compounds of l i t h i u m c a n be expected to react w i t h most m a t e rials of construction at elevated temperatures. T o the authors' knowledge, l i t e r a ture p u b l i s h e d to date does not cover the rate of corrosion b y m o l t e n l i t h i u m m e t a l i n relation to the contained impurities. T h e " L i q u i d - M e t a l s H a n d b o o k " (23) contains p r o b a b l y the best s u m m a r y of the data available o n the corrosiveness of l i q u i d l i t h i u m . T h i s report listed o n l y p u r e i r o n , c o l u m b i u m , t a n t a l u m , a n d m o l y b d e n u m as h a v i n g good resistance for r e l a t i v e l y l o n g periods of use at temperatures u p to 900 ° C . F e r r i t i c - c h r o m i u m stainless steels are listed as h a v i n g good resistance u p to 800 ° C . A l l other metals a n d nonmetals do not have a good l o n g - t e r m resistance at h i g h temperatures. G o o d resistance to l i q u i d l i t h i u m u p to 600 ° C . b y T y p e 347 stainless steel a n d b e r y l l i u m has been listed i n a recent report (21) c o v e r i n g w o r k p e r f o r m e d at A r g o n n e N a t i o n a l L a b o r a t o r y . Hoffman a n d M a n l y stated (18) that only m o l y b d e n u m , tungsten, n i o b i u m , a n d A r m c o i r o n h a v e good corrosion resistance to h i g h temperature ( 8 0 0 ° C . ) static l i t h i u m . Because of l i t h i u m ' s excellent p h y s i c a l properties as a heat transfer m e d i u m , more t h o r o u g h studies need to be made of the corrosive properties of l i q u i d l i t h i u m , w i t h some attempt to evaluate the effect of k n o w n amounts of i m p u r i t i e s . T h e corrosion a n d mass transfer d u e to p u r e l i t h i u m s h o u l d be d e t e r m i n e d as accurately as possible. T h e effect o n corrosion due to a k n o w n q u a n t i t y of i m p u r ities c o u l d then be determined. W i t h this k n o w l e d g e available, two approaches to the p r o b l e m of m a k i n g l i t h i u m a usable coolant c o u l d be m a d e : to develop alloys resistant to l i t h i u m w i t h k n o w n amounts of impurities, a n d to develop techniques of m a n u f a c t u r i n g a n d h a n d l i n g l i t h i u m i n o r d e r to m a i n t a i n the degree of p u r i t y r e q u i r e d . D a t a o n the properties of l i t h i u m alloys as l i q u i d m e t a l coolants have not been r e v i e w e d b y the authors. H o w e v e r , w i t h this approach, it m a y be possible to m a k e use of l i t h i u m ' s excellent p h y s i c a l properties a n d overcome some of its adverse c h e m i c a l properties.

Summary L i t h i u m is p r o p e r l y i n c l u d e d as the first m e m b e r of G r o u p I i n the P e r i o d i c T a b l e b y reason of its atomic configuration a n d general characteristics. H o w e v e r ,


A D V A N C E S IN CHEMISTRY SERIES

24

a d e t a i l e d s t u d y of the p r o p e r t i e s a n d reactions of b o t h the elements a n d t h e i r compounds

shows that l i t h i u m often

resembles G r o u p s II

a n d III

metals

more

closely t h a n G r o u p I metals. O r g a n o l i t h i u m c o m p o u n d s f o r m a u n i q u e class of o r g a n o m e t a l l i c

compounds

w i t h s t a b i l i t y , s o l u b i l i t y , a n d a c t i v i t y characteristics i n t e r m e d i a t e b e t w e e n those of the other G r o u p I a n d the G r o u p II o r g a n o m e t a l l i c Recent

investigations

have

shown

l i t h i u m to be

compounds. a unique

catalyst

for

the

p o l y m e r i z a t i o n of diolefins to m a t e r i a l s of definite a n d p r e d i c t a b l e s t r u c t u r e , a n d to h a v e a n i n t e r e s t i n g p o t e n t i a l as a d i r e c t r e d u c i n g agent i n solvents

such

as

a m m o n i a , amines of l o w m o l e c u l a r , a n d e t h y l e n e d i a m i n e . The

affinity of l i t h i u m f o r o x y g e n is b e i n g u t i l i z e d i n the m e t a l l u r g i c a l

to r e d u c e the p o r o s i t y i n castings of copper a n d copper alloys.

field

Recent investiga

t i o n has r e v e a l e d that l i t h i u m w i l l p r o d u c e b r a z i n g alloys w i t h s e l f - f l u x i n g p r o p


erties a n d increase the w e t t i n g a b i l i t y of these a l l o y s . T h e usefulness of l i t h i u m h y d r i d e a n d l i t h i u m a l u m i n u m h y d r i d e i n the p r e p a r a t i o n of other h y d r i d e s has b e e n w i d e l y d e m o n s t r a t e d . O t h e r c o m p l e x

hydrides

p r e p a r e d i n a s i m i l a r m a n n e r m a y p r o v e to be i n t e r e s t i n g tools for r e s e a r c h . B a s e d o n its p h y s i c a l p r o p e r t i e s alone, l i t h i u m m e t a l w o u l d a p p e a r to n o e q u a l as a l i q u i d m e t a l coolant.

have

H o w e v e r , because of c o r r o s i o n c a u s e d at e l e

vated temperatures b y impurities i n commercially available l i t h i u m and b y

the

m e t a l iself, l i t h i u m has f o u n d o n l y e x p e r i m e n t a l use as a l i q u i d m e t a l coolant.

Literature Cited (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22) (23) (24) (25) (26) (27) (28) (29) (30) (31) (32) (33)

B a r b a r a s , G . D . , D i l l a r d , C., F i n h o l t , A. E., W a r t i k , T . , W i l z b a c h , Κ . E., Schlesinger, H . I., J. Am. Chem. Soc. 73, 4585 (1951). B a u e r , R., " U b e r H y d r i d e u . M i s c h - h y d r i d e des Magnesiums, B e r y l l i u m s u . Z i n n s , " Dissertation, 1951; (cf. 36). Benkeser, R. Α . , A r n o l d , C., L a m b e r t , R. F . , T h o m a s , O . H . , J. Am. Chem. Soc. 77, 6042 (1955). Benkeser, R . Α . , R o b i n s o n , R. E., Suave, D . M., T h o m a s , Ο. H., Abstracts of P a p e r s , 125th M e e t i n g , A C S , K a n s a s C i t y , M o . , M a r c h 1954. Benkeser, R . Α . , R o b i n s o n , R. E., Suave, D . M., T h o m a s , O . H., J. Am. Chem. Soc. 77, 3230 (1955). B r e d z s , N . , C a n o n i c o , D . , Welding J., Research Supplement, N o v e m b e r 1955. B r o w n , H. C., Schlesinger, Η . I., U. S. Patent 2,543,511 (Feb. 27, 1951). Chauvenet, E., Ann. chim. et phys. 23, 430 (1911). E l l i o t , J. R., B o l d e b u c k , E. M., Roedel, G. F., J. Am. Chem. Soc. 74, 5047 (1952). E l l i s , L. M., U. S. Patent 2,212,155 ( A u g . 20, 1940). F i n h o l t , A. E., B o n d , A. C., Schlesinger H. I., J. Am. Chem. Soc. 69, 1199 (1947). F i n h o l t , A. E., B o n d , A. C., W i l z b a c h Κ . E., Schlesinger, H. I., Ibid., 69, 2692 (1947). F l e m i n g , R. F., U. S. Patent 2,386,452 (Oct. 9, 1945). G i l m a n , H., " O r g a n i c C h e m i s t r y , An A d v a n c e d T r e a t i s e , " 2nd ed., Vol. I, p. 489, W i l e y , N e w Y o r k , 1943; G i l m a n , H., M o r t o n , J. W . , " O r g a n i c R e a c t i o n s , " V o l . VIII, p. 258, W i l e y , N e w Y o r k , 1954. H a n f o r d , W . M., R o l a n d , J. R., Y o u n g , H. S., U. S. Patent 2,377,779 (June 5, 1945). H e y l , W . , B r i t . P a t e n t 711,174 (June 23, 1954). H o w k , B . W . , L i t t l e , E. L., Scott, S . L., W h i t m a n , G . M., J. Am. Chem. Soc. 76, 1899 (1954). Hoffman, Ε. E., M a n l y , W . D . , P r e p r i n t , N u c l e a r E n g i n e e r i n g a n d Science Congress, C l e v e l a n d , O h i o , D e c e m b e r 1955. H u r d , D . T . , " I n t r o d u c t i o n to C h e m i s t r y of H y d r i d e s , " W i l e y , N e w Y o r k , 1952. H u t t e , H. H., B r i t . Patent 707,851 ( A p r i l 21, 1954). K e l m a n , L. R., W i l k i n s o n , W . D . , Yaggee, F . L., U. S. A t o m i c E n e r g y C o m m i s s i o n , "Re sistance of Materials to A t t a c k b y L i q u i d M e t a l s , " ANL-4417 (1950). L a n d o l t , P. E., P y n e , F. R., Foundry 77, N o . 3, 90 (1949). L y o n , R . N., " L i q u i d - M e t a l s H a n d b o o k , " 2nd ed., Supt. of Documents, Washington, D . C., 1952. M o r g a n , R. L., T a n n h a u s e r , P . , P r a t t , R. J., M y e r s , T . C., Jensen, Ε. V., J. Am. Chem. Soc. 77, 5658 (1955). S c h l e n k W . , H o l t z , J., Ber. 50, 262 (1917). Schlesinger, H. I., B r o w n , H. C., U. S. Patent 2,545,633 ( M a r c h 20, 1951). Schlesinger, H. I., B r o w n , H. C., others, J. Am. Chem. Soc. 75, 186 (1953). Schlesinger, H. I., B r o w n , H. C., G i l b r e a t h , J. R., K a t z , J. J., Ibid., 75, 195 (1953). Schlesinger, H. I., B r o w n , H. C., H o e k s t r a , H. R., R a p p , L. R., Ibid., 75, 199 (1953). Schlesinger, H. I., B r o w n , H. C., H y d e , Ε. K., Ibid., 75, 209 (1953). S c h m i d t , M . , "Z. K e n n t n i s u . H y d r i d e n u . M i s c h h y d r i d e n des A l u m i n i u m s , G a l l i u m s , Indiums u n d T h a l l i u m s , " Dissertation, S. 12ff., 42ff., 60ff., 1951; (cf. 36). Ibid., S. 30ff., 54ff., 75ff. Spencer, J. F., P r i c e , G. M., J. Chem. Soc. 97, 385 (1910).


FENTON, ESMAY, LARSEN A N D SCHROEDER—USES OF LITHIUM METAL (34) (35)


(36) (37) (38) (39) (40) (41) (42) (43) (44) (45) (46) (47) (48) (49) (50) (51) (52)

25

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