Arylsilanes AMOS R. ANDERSON, ROBERT W. LERNER, and

Arylsilanes

AMOS R. ANDERSON, ROBERT W. LERNER, and WILLIAM E. SMITH

Downloaded by UNIV ILLINOIS URBANA-CHAMPAIGN on October 12, 2016 | http://pubs.acs.org Publication Date: January 1, 1959 | doi: 10.1021/ba-1959-0023.ch019

Anderson Chemical Co., Weston, Mich.

This investigation describes the study and development of methods of synthesis for the series of phenylbiphenylylsilanes, the characterization of these compounds, and the production of pilot plant quantities. Phenyltribiphenylylsilane, diphenyldibiphenylylsilane, triphenylbiphenylylsilane, and tetrabiphenylylsilane were produced by a sodium condensation method. The compounds have extreme thermal stability and several possible commercial applications are proposed.

It is somewhat unusual to find in the organosilicon field, where so much work has been carried out in the past 12 years, a class of silanes that have been almost entirely neglected. The tetraarylsilanes are such a class. In this class tetraphenylsilane is the oldest known compound and of all the references pertaining to the tetraarylsilanes only two were found describing other compounds than the tetraphenylsilane (28-30). The present investigation was undertaken to synthesize, characterize, and study the problem of pilot plant production of the complete series of phenylbiphenylylsilanes. The initial interest was in the unusual thermal stability of the silicon-aryl carbon bond and the low vapor pressure of the completely arylated silanes. During this work Spialter, Priest, and Harris published their work on phenylp-biphenylylsilanes (33) which corroborated many of the values found in this investigation. In general, all previous tetraarylsilanes have been prepared by the method of Polis (26) or some modification thereof. The equation for the preparation of tetraphenylsilane is typical of this method. 4C H C1 + SiCl + 8Na -> (C H ) Si + 8NaCl 6

5

4

6

5

4

The most notable modification is that of Schumb and Saffer (30), in which the alkylsodium is first prepared, subsequently added to the silicon tetrachloride, thereby giving a better distribution of organic groups. The sodium method is applicable to the synthesis of silanes which heretofore could be prepared only by the Grignard or alkylzinc methods. Other possible methods of synthesis, such as the Grignard method, the "direct method," and the silane route (2o), have been tried with varying degrees of success. Taking into account that the method chosen would be subject to a considerable scale-up, it was decided to use the Polis method with modifications and with the incorporation of the new sodium dispersion techniques. It was found early in the investigation that there were many variables which affected the reaction. 212

METAL-ORGANIC COMPOUNDS Advances in Chemistry; American Chemical Society: Washington, DC, 1959.

ANDERSON, LERNER, AND SMITH—ARYLSILANES

213

Discussion V e r y b r i e f l y t h e v a r i a b l e s w h i c h were r e a c t i o n s t o a m a r k e d degree were :


A. B. C. D. E.

found

t o affect

t h e progress

of these

S o d i u m particle size Solvent P u r i t y of reactants Agitation Temperature

T h e use of sodium dispersions, although n o t valuable i n l a b o r a t o r y reactions, became exceedingly i m p o r t a n t i n scale-up operations. B e c a u s e o f t h e necessary s c a l e - u p , the selection of s o l v e n t s b e c a m e v e r y i m p o r t a n t . A n e t h e r - t y p e s o l v e n t has been p r o v e d t o be t h e best f o r s o d i u m r e a c t i o n s (31), w i t h the d i e t h e r s s u p e r i o r t o the m o n o e t h e r s . B o t h d i e t h y l ether a n d the d i m e t h y l e t h e r o f e t h y l e n e g l y c o l were t r i e d e x p e r i m e n t a l l y a n d g a v e g o o d y i e l d s . However, because o f the flammability a n d the p o s s i b i l i t y o f p e r o x i d e f o r m a t i o n , these s o l v e n t s were r u l e d o u t f o r l a r g e scale o p e r a t i o n s . V M & Ρ h i g h flash n a p h t h a w a s chosen f o r s c a l e d - u p o p e r a t i o n s because o f the f o l l o w i n g c h a r a c t e r i s t i c s . T h e b o i l i n g range is above the m e l t i n g p o i n t of s o d i u m . I t has a flash p o i n t above 50°F. T h e products of reaction are soluble at reflux temperatures, b u t have negligible s o l u b i l i t y at r o o m temperatures. I t c o u l d therefore be u s e d as a g e n e r a l s o l v e n t f o r a l l phases o f the p i l o t p l a n t method. T h e r e a c t i o n s were f o u n d t o be e x t r e m e l y sensitive t o t r a c e i m p u r i t i e s p r e s e n t i n the halogenated b i p h e n y l a n d often completely i n h i b i t e d t h e desired reaction. T h i s d i f f i c u l t y was o v e r c o m e t o some e x t e n t b y t h e use of h i g h speed s h e a r i n g t y p e a g i t a t i o n . T h e effect o f excessively h i g h t e m p e r a t u r e s was s t u d i e d a n d f o u n d t o l e a d t o t h e coupling of the b i p h e n y l molecules. B y g i v i n g p r o p e r a t t e n t i o n t o a l l of these v a r i a b l e s the f o l l o w i n g g e n e r a l m e t h o d was w o r k e d o u t a n d s u c c e s s f u l l y e m p l o y e d w i t h o n l y a f e w e x c e p t i o n s . Sodium is d i s p e r s e d u n d e r n i t r o g e n , i n V M & Ρ h i g h flash n a p h t h a , i n a s p e c i a l l y designed u n i t . I t is then transferred t o the reaction kettle, a n d the chlorosilane a n d b i p h e n y l halide, d i s s o l v e d i n h i g h flash n a p h t h a , a r e a d d e d s l o w l y w i t h efficient a g i t a t i o n . H e a t i n g u n d e r reflux i s c o n t i n u e d t o c o m p l e t e t h e r e a c t i o n a n d the h o t m a s s i s t h e n f i l t e r e d t h r o u g h a n i t r o g e n pressure filter. T h e a r y l s i l a n e i s a l l o w e d t o c r y s t a l l i z e f r o m t h e n a p h t h a , t h e n i s filtered a n d d r i e d . F r o m t h i s stage o n e r e c r y s t a l l i z a t i o n i s u s u a l l y sufficient t o g i v e n e a r l y p u r e m a t e r i a l . Y i e l d s a r e of t h e o r d e r of 6 5 t o 8 0 % . B y t h i s m e t h o d t h e c o m p l e t e series o f p h e n y l - p - b i p h e n y l y l s i l a n e s o f t h e g e n e r a l f o r m u l a g i v e n b e l o w h a v e been p r e p a r e d i n q u a n t i t y .

A s o f t h i s w r i t i n g s e v e r a l m e m b e r s o f t h e series w i t h o- a n d ra-biphenyl have also been p r e p a r e d a n d t h e s y n t h e s i s o f u n s y m m e t r i c a l silane molecules c o n t a i n i n g p h e n y l o-, m - , a n d p - b i p h e n y l is u n d e r w a y . T h e s e r e a c t i o n s are s l u g g i s h , b u t c a n b e c o m e v i o l e n t i f excessive a m o u n t s of r e a c t a n t s are a l l o w e d t o b u i l d u p .

Experimental I n general, pilot plant production followed laboratory of the p i l o t p l a n t u n i t is r e p r e s e n t e d i n F i g u r e 1.

findings.

A flow d i a g r a m



214

ADVANCES IN CHEMISTRY SERIES

Figure

1.

Equipment flow chart for phenylbiphenylylsilanes

A. Nitrogen cylinder B. Sodium dispersator C. Charge tanks D. Reactor E. Condensers F. Receiver tanks G. Filters H. Crystallizing tanks

/. Solution make-up kettle J. Purification kettle K. Solvent recovery still L. Drying oven M. Pulverizer N. Solvent storage tank O. Solvent pumps

T h e f o l l o w i n g p r o c e d u r e for t h e p i l o t p l a n t p r o d u c t i o n o f t r i p h e n y l - p - b i p h e n y l y l silane is t y p i c a l o f t h e series. T h e r e a c t o r s y s t e m , c o n s i s t i n g o f a s p e c i a l l y designed s o d i u m d i s p e r s a t o r , B, r e a c t i o n k e t t l e D, a n d filter G, was p u r g e d w i t h n i t r o g e n u n t i l a n O r s a t a n a l y s i s p r o v e d i t free o f o x y g e n . S i x gallons o f h i g h flash n a p h t h a a n d 11 p o u n d s a n d 4 ounces o f s o d i u m were c h a r g e d i n t o t h e d i s p e r s i o n t a n k . T h e t e m p e r a t u r e w a s r a i s e d t o 110° to 1 2 0 ° C . a n d t h e s o d i u m d i s p e r s i o n was o b t a i n e d b y o p e r a t i n g t h e d i s p e r s a t o r h e a d a t 3500 r . p . m . f o r 15 t o 20 m i n u t e s . T h i s d i s p e r s i o n was t h e n t r a n s f e r r e d b y n i t r o g e n p r e s s u r e t o t h e n i t r o g e n p u r g e d , previously w a r m e d (70°C.) glass-lined P f a u d l e r kettle. T h i s kettle was fitted w i t h a n a i r c o n d e n s e r , r e c e i v e r , glass a d d i t i o n t a n k , n i t r o g e n i n l e t , t h e r m o m e t e r , d i s p e r s i o n i n l e t , a n d a n c h o r - t y p e a g i t a t o r . A glass p i p e was also e x t e n d e d n e a r l y t o t h e b o t t o m of t h e k e t t l e a n d i t w a s f i t t e d w i t h a r u b b e r s u c t i o n b u l b f o r d r a w i n g u p a s a m p l e o f the reaction m i x t u r e f o r observation. A f t e r t h e dispersion was transferred, t h e d i s p e r s i o n p o t w a s r i n s e d w i t h t w o 1-gallon p o r t i o n s o f h i g h flash n a p h t h a a n d t r a n s f e r r e d b y n i t r o g e n pressure i n t o t h e r e a c t i o n k e t t l e . T h e a d d i t i o n o f t h e s o l u t i o n o f halides i n h i g h flash n a p h t h a was i m m e d i a t e l y b e g u n a n d t h e i n i t i a t i o n o f t h e r e a c t i o n , a f t e r t h e a d d i t i o n h a d s t a r t e d , was e v i d e n c e d b y a r a p i d rise i n t e m p e r a t u r e a n d development of the characteristic blue colored reaction m i x t u r e . T h e addition was a d j u s t e d t o m a i n t a i n t h e r e a c t i o n t e m p e r a t u r e a t 120° t o 1 3 0 ° C . A reflux p e r i o d o f 4 h o u r s f o l l o w e d a f t e r t h e a d d i t i o n w a s c o m p l e t e d , a n d d u r i n g t h i s p e r i o d 5 g a l l o n s o f h i g h flash n a p h t h a w a s d i s t i l l e d o v e r a n d r e m o v e d . T h e hot refluxing reaction m i x t u r e was then filtered under nitrogen pressure. T h e filtrate was allowed t o stand 3 t o 4 days t o crystallize the triphenyl-p-biphenylylsilane. T h e light y e l l o w c r y s t a l l i n e s o l i d was f i l t e r e d off, w a s h e d w i t h 10 g a l l o n s o f f r e s h h i g h flash


ANDERSON, LERNER, A N D SMITH—ARYLSILANES

215

naphtha, a n d dried i n a steam-heated v a c u u m oven. T h e crude y i e l d was 66 pounds, 71.5% of theory, melting point 153-6°C. O n e r e c r y s t a l l i z a t i o n f r o m h i g h flash n a p h t h a g a v e w h i t e c r y s t a l s o f m e l t i n g p o i n t 157° t o 1 6 0 ° C . T h e e n t i r e series o f p h e n y l - p - b i p h e n y l y l s i l a n e s w a s p r e p a r e d b y s i m i l a r

procedures

w i t h r e s u l t s as l i s t e d i n T a b l e I .


Table I. Reaction Solvent VM&P naphtha

Product (CerhjiSiCeFUCeHe (C6H )2Si(CeH4C6H ) 6

CeH Si(CeH4CeH5)s Si(C H4CeH )4

6

Melting Point of Crude, ° C . 153-6

Crude Yield, % 71

165-72 150-63 264-74

82 62 79

2

6

6

Reaction Conditions

6

Solvent Recovery VM&P solvent

Purified Yield, % 56

Melting Point of Purified, ° C . 157-60

Xylene

62 54 72

168-70 156-58 278-282

T o c h a r a c t e r i z e these c o m p o u n d s a n u m b e r o f p h y s i c a l c o n s t a n t s w e r e d e t e r m i n e d (Table I I ) .

Table II. Physical Properties Melting point, °C. K H S Boiling point, ° C . Flash point, open cup, °C. Fire point, open cup, °C. Density 20° C . Surface tension, dynes/cm. 350° F . 450° F . Solubility, grams/100 ml. 20° C . Benzene Methyl ethyl ketone Ethyl alcohol n-Heptane Pyridine Viscosity, cps. 300° F . 450° F . e

a

Physical Properties of Phenylbiphenylylsilanes Ί ri-p-biphcnylylphenylsilane 174 580 380 440 1.10

Di-p-biphcnylyldiphenylsilane 170 570 338 392 1.14

Tetra-p-biphenylylp-Biphenylyltriphenylsilane silane 283 159 512 600 299 400 338 499 1.16 1.07

48.63 43.86

31.61 28.91

42.26 38.47

40.67 39.50

17.776 9.396 0.238 0.052 2.725

36.46 6.54 0.40 0.38 12.91

14.10 3.49 0.205 0.799 17.88

0.27 8.20 0.049 0.096 16.69

40 1

8 1

370 12

solid 500

For comparison boiling points were included as determined by Spialter (38).

Practical Applications With

the determination

of t h e p h y s i c a l

properties

complete,

work

on

the

a p p l i c a t i o n s o f these m a t e r i a l s i s b e i n g c a r r i e d o u t . T h e a p p l i c a t i o n s w i l l d e p e n d p r i m a r i l y o n t h e s u p e r i o r t h e r m a l s t a b i l i t y , l o w v a p o r p r e s s u r e , a n d e x c e l l e n t resistance t o b e t a r a d i a t i o n o f these c o m p o u n d s . A l t h o u g h n e w design a n d engineering w o r k w o u l d be n e c e s s a r y , t h e y m a y w e l l p r o v e a d e q u a t e as e x t r e m e h i g h t e m p e r a t u r e l u b r i c a n t s a n d h y d r a u l i c fluids n e e d e d f o r s u p e r s o n i c a i r c r a f t a n d g u i d e d m i s s i l e s . F o r p u r p o s e s o f c o m p a r i s o n , a v a i l a b l e a i r c r a f t h y d r a u l i c s y s t e m s s e l d o m r e a c h t e m p e r a t u r e s i n excess of 3 0 0 ° F . , w h e r e a s p l a n e s a n d g u i d e d missiles b e y o n d p r e s e n t p r o t o t y p e s w i l l p r o b a b l y exceed t h e 7 0 0 ° F . r a n g e . T h e best o f t h e c o m m e r c i a l l y a v a i l a b l e oils, t o d a y , w i l l n o t w i t h s t a n d temperatures above 550°F., whereas t h e p h e n y l b i p h e n y l y l s i l a n e s have shown n o d e c o m p o s i t i o n a t t e m p e r a t u r e s w e l l i n excess o f t h e 7 0 0 ° F . g o a l . M o r e i m m e d i a t e l y , these c o m p o u n d s a r e b e i n g i n v e s t i g a t e d as grease fillers, p o t t i n g c o m p o u n d s , p l a s t i c stabilizers, a n d f o r m a n y other applications where t h e r m a l a n d r a d i a t i o n stability are important.

Acknowledgment T h e research described was supported b y the C h e m i s t r y Research B r a n c h , W r i g h t A i r Development

Center, Wright-Patterson A i r Force Base, Ohio.


216

ADVANCES IN CHEMISTRY SERIES


References (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) (34) (35) (36)

Anderson, T. J., J. Chem. Phys. 4, 161-4 (1936). Behagel, O. Seibert, H., Ber. deut. chem. Ges. 66B, 922-4 (1933). Clapp, D. B., J. Am. Chem. Soc. 61, 523-4 (1939). Dolgov, B. N., Volnor, Y. N., Zhur. ObshcheĭKhim, Ser. I, 1931, 1091-104. Drew, H. D. K., Landquist, J. K., J. Chem. Soc. 1935, 1480-2. Gatterman, L,, Weinlig, K., Ber. deut. chem. Ges. 27, 1943-48 (1894). George, W. H., Proc. Roy. Soc. 113A, 585-93 (1927). Giacomello, G., Gazz. chim. ital. 68, 422-8 (1938). Gilman, H., Woods, L. Α., J. Am. Chem. Soc. 65, 435-7 (1943). Ipatieff, V. N., Dolgov, B., Ber. deut. chem. Ges. 62B, 1220 (1929). Jorg. H., Stetter, I., J. prakt. Chem.117,305-10 (1927). Kipping, F. S., Blackburn, J. E., J. Chem. Soc. 1932, 2200. Kipping, F. S., Blackburn, J. E., Shurt, J. F., Ibid., 1931, 1290-8. Kipping, F. S., Cura, Ν. W., Ibid., 1935, 1088-91. Kipping, F. S., Lloyd, L. L., Proc. Chem. Soc. 15, 174 (1899). Kipping, F. S., Murray, A. G., J. Chem. Soc. 1929, 360-7. Kipping, F. S., Short, J. F., Ibid., 1931, 1290-8. Kraus, C. Α., Eatough, H., J. Am. Chem. Soc. 55, 5008-14 (1933). Krause, E., Renwanz, G., Ber. deut. chem. Ges. 62B, 1710-16 (1929). Ladenberg, A., Ibid., 46, 2274-9 (1907). Makarova, L. G., Nesmeyanov, A. S., J. Gen. Chem. (U.S.S.R.) 9, 771-9 (1939). Manulkin, Α., Yakubura, F., Ibid., 10, 1300-2 (1941). Mark, H., Nehner, H., Z. Krist. 65, 455-60 (1927). Milazzo, G., Gazz. chim. ital. 71, 73-81 (1941). Peake, J. S., Nebergall, W. H., Chen, Y. T., J. Am. Chem. Soc. 74, 1526 (1952). Polis, Α., Ber. deut. chem. Ges. 18, 1540-4 (1885). Ibid., 19, 1012-24 (1886). Schumb, W. C., Ackerman, J., Jr., Saffer, C. M., Jr., J. Am. Chem. Soc. 60, 2486-8 (1938). Schumb, W. C., Saffer, C. M., Jr., Ibid., 61, 363-6 (1939). Ibid., 63, 93 (1941). Scott, N . D., Walker, J. F., Hansley, V. L., Ibid., 58, 2442-4 (1936). Smith, R. H., Andrews, D. H., Ibid., 53, 3661-7 (1931). Spialter, L., Priest, D. C., Harris, C. W., Ibid.,77, 6227 (1955). Sugden, S., Wilkins, H., J. Chem. Soc. 1931, 126-8. Vorlander, D., Ber. deut. chem. Ges., 58B, 1893-914 (1925). Wiley, R. H . (to Ε. I. du Pont de Nemours and Co.), U . S. Patent 2,238,669 (April 15, 1941). RECEIVED for review May 10, 1957. Accepted June 1, 1957.


Arylsilanes AMOS R. ANDERSON, ROBERT W. LERNER, and

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