CATALYTIC WITH

REACTION

WITH

PHENYLCHLOROSILANES

METHYLCHLOROSILANES

COMMUNICATION AND

OF

4. REACTION

OF DIPHENYLDICHLOROSILANE

TRIPHENYLCHLOROSILANE DIMETHYLDICHLOROSILANE V. N. S. A.

Penskii, Golubtsov,*

V.

UDC 542.97:547.1'128

V. Ponomarev, and K. A. Andrianov

Diphenyldichlorosilane (DPDCS) r e a c t s with methylchlorosilanes at 250 ~ under p r e s s u r e , in the p r e s e n c e of LiA1H4, either with the exchange of the phenyl group by the chlorine atom of m e t h y l t r i c h l o r o silane (MTCS) [1], or the exchange of either the phenyl group or the chlorine atom by the methyl group of t r i m e t h y l c h l o r o s i l a n e (TMCS); in this connection the exchange of the radical is evidently the m o r e p r e f e r r e d [2]. Triphenylchlorosilane (TPCS) under the described conditions r e a c t s with MTCS and TMCS only via exchange of the phenyl group by the chlorine atom of MTCS [1], or by the methyl group of TMCS [2]. Methylphenylchlorosilanes are practically not formed when dimethyldichlorosilane (DMDCS) is reacted with phenyltriehlorosilane (PTCS) under these conditions [3]. Since PTCS exchanges only the chlorine atom, then the reaction between DMDCS and PTCS should proceed only with the formation of methylphenylchlorosilane, but this fails to occur. Apparently, only the exchange of the chlorine atom is characteristic (under the investigated conditions) for DMDCS. * Deceased. 10 .oY

n,8

o

.o

~-

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-c.

o-

o2

~o,~/

N N

3

-o

N ~o,z

o,z

//o,

o o

o

~

o

7

/ 2 h 3 ~/ h P Fig. 2 Fig. 1 Fig. 1. Degree of conversion of DPDCS (1) and DMDCS (2) and yield of reaction products (when b a s e d on r e a c t e d DPDCS) at 250 ~ as a function of time: 3) MPDCS; 4) MDPCS; 5) DMPCS; 6) PTCS; 7) TPCS; 8) MTCS; 9) TMCS. i

Z

Fig. 2. Degree of conversion of DPDCS (1) and DMDCS (2) and yield of reaction products (when based on r e a c t e d DPDCS) at 200 ~ as a function of time: 3) DMPCS; 3) PTCS; 5) MPDCS; 6) TPCS; 7) MDPCS.

T r a n s l a t e d f r o m Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1145-1149, May, 1972. Original article submitted June 24, 1970.

9 1972 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011. All rights reserved. This article cannot be reproduced for any purpose whatsoever without permission of the publisher. A copy of this article is available from the publisher for $15.00.

1096

~

g,8

o~.

~o

~t7,5 -

~

oa

~,Z

0. l 7

/,0

z,g

~0 Fig. 3

h

g,0

0,5 ~,o TPCS/DMDCS, M Fig. 4

r,5

Fig. 3. Degree of conversion of DMDCS (1) and TI~CS (2) and yield of reaction products (when b a s e d on r e a c t e d TPCS) as a function of time: 3) DPMCS; 4) MPDCS; 5) Dt~DCS; 6) DMPCS; 7) TMCS; 8) MTCS. Fig. 4. Degree of conversion of DMDCS (1) and TPCS (2) and yield of reaction products (when b a s e d on r e a c t e d TPCS) as a function of the ratio of the starting reactants: 3) MI)PCS; 4) DPDCS; 5) MI~DCS; 6) DMPCS; 7) TMCS. In the p r e s e n t p a p e r we studied the reaction of DMDCS with D1DDCS and TPCS at 200 and 250 ~ under p r e s s u r e , ia the p r e s e n c e of LiA1H4, as a function of the ratio of the starting products and the duration of the p r o c e s s . The main reaction p r o d u c t s of DMDCS with DPDCS is methylphenyldiehlorosilane (MPDCS) (N 35%), while the yield when b a s e d on r e a c t e d DPDCS r e a c h e s 90%. The other methylphenylchlorosilanes, and specifically dimethylphenylchlorosilane (DMPCS) and diphenylmethylchlorosilane (DPMCS) are f o r m e d in s m a l l amounts (Fig. 1). T o g e t h e r with the methylphenylchlorosilanes, the reaction m a s s contains up to 10% of ]?TCS. The m a x i m u m degree of conversion is r e a c h e d at 250 ~ in l h , and is 70% for DPDCS, and 65% for DMDCS. We will examine the possible s c h e m e s for the reaction of DPDCS with DMDCS: CGH~C!~SiCeH~ + C1SiCI(CHa)~~ C6HsSiCI~ + CsHsSiC1 (CH3)~

(1)

(C~H~)~C1SiC1 + CH3SiCI~CHs-->-(CsH~)2SiC1CH3 + CH3SiC13

(2)

CsH~CI~SiC6H 5 + CH3 -- SiCI~CH3 -+ 2C6HsSiCI~CH3

(3)

Of the presented schemes, only (3) leads to the formation of !Vf!DDCS --the main product in the reaction mixture. PTCS, DMPCS, DPMCS, and especially MTCS, the preparation of which is possible according to schemes (i) and (2), are formed in much lower yield (see Fig. i). At first glance this leads to the postulation that reaction (3) is the most probable in the discussed case. However, such a course for the process is associated with the exchange of the methyl group in the DMDCS molecule, which contradicts the conclusions that were made on the basis of studying the reaction of DYf[DCS with PTCS [3]. As can be seen from Fig. I, the reaction mixture comes to equilibrium even within an hour from the start of heating at 250 ~ Hardly any changes in the concentrations of the starting and formed products takes place on further heating of the reaction mass (8 h). As a result, the mechanism for the formation of the variolm compounds must be studied in the early stages of the reaction, i.e., the composition of the reaction mixture has to be studied before equilibrium is reached. Thus, at 200 ~ in the first 2h of heating, the main reaction products are DMPCS and PTCS, while the yield of MPDCS is small at first (Fig. 2). Consequently, here the reaction of DPDCS with DMDCS proceeds mainly according to scheme (i), in which connection the formation of hl~PDCS is not associated with the direct reaction of DPDCS with DMDCS, which is in complete agreement with the data given in [3]. After 4h the conversion of the starting materials reaches equilibrium, while the concentration of MPDCS continues to increase, with a simultaneous synchronous decrease in the yield of DMPCS and PTCS. This leads to the postulation that MPDCS is formed as the result of their reaction:

1097

(4)

~C~HsCl~SiCl + CH~SiCI(C~H~)CH~ --~ 2(CHa)C6H~SiCI~ It is interesting to mention that the p r e s e n c e of MTCS in the reaction mixture was not detected at 200 ~. This apparently suggests that s c h e m e (2) in general is not realized. The s a m e as in the reaction of Dt~DCS with TMCS, in the d i s c u s s e d case a l a r g e amount of TPCS (up to 0.5 M p e r M of r e a c t e d DPDCS) is f o r m e d at the start, the concentration of which d e c r e a s e s with time (see Fig. 2). According to [1], in the given case the formation of TPCS is a s s o c i a t e d with the disproportionation of DPDCS (C6H~)~SiC12 --~ C6H~SiCI3 + (C~H~)3SiC1

(5)

First, there o c c u r s a d e c r e a s e in the TPCS concentration with time due to a shift of equilibrium (5) to the left with i n c r e a s e in the amount of PTCS, and second, the formation of DPlVICS (see Fig. 2) evidently occurs, due to the reaction of TPCS with DMPCS: CHsC~H~C1SiCH~ + C~HsSi(C6Hs)2C1--~ 2CH3(CeHs)~SiC1

(6)

since, as we had a l r e a d y mentioned above, the formation of DPMCS according to reaction (2) fails to occur. The formation of DPMCS f r o m MPDCS and TPCS apparently also fails to o c c u r in view of the low concentration of MPDCS in the initial p e r i o d and the low concentration of TPCS in the final period of reaction. The higher yield of DMPCS when compared with 1DTCS [reaction (1)] is apparently explained by the r e a c tion of TPCS with DMDCS: (C~H~)2C1SiCeH~ -f- C1SiCI(CH3)~~ (C~H~)~SiC12 ~ (CH~)~CISiC~H~

(7)

which is responsible for the lower degree of conversion of DPDCS when c o m p a r e d with DMDCS that is o b s e r v e d at the s t a r t . The formation of TMCS and MTCS apparently o c c u r s during the disproportionation of DMDCS in the initial p e r i o d of reaction, as is evidenced by their p r a c t i c a l l y constant amount in the reaction products at 250 ~ and their absence at 200 ~ The data obtained by us on the disproportionation of pure DMDCS in the p r e s e n c e of LiA1H4 at various t e m p e r a t u r e s s e r v e s as confirmation of this (see Fig. 1). The second part of the p r e s e n t paper was a study of the reaction of DMDCS with TPCS. The main reaction products a r e DPIV[CS, 3IFDCS, DPDCS and DMPCS, and s m a l l amounts of TMCS and MTCS. The degree of conversion of the s t a r t i n g m a t e r i a l s is ~80% at 250 ~ and it r e a c h e s its m a x i m u m value in p r a c tically an hour, but the equilibrium of the reaction products is r e a c h e d somewhat later, in approximately 4h. As a result, changes in the composition of the reaction m a s s after the f i r s t hour of reaction p r o c e e d without involving the starting reactants. Scheme (9) must be excluded f r o m the three variations for the reaction of T1DCS with DMDCS: (CsHs)~C1SiC6H~ + C1SiCI(CH3)2-~ (CsHs)~SiCI~ + C~ItsC1Si(CI-I3)~

(8)

(CsH~)sSiCl + CH3SiCI2CHs -~ (C6H~)3SiCHs + CH3SiCl, (C~H~)~CISiC6H~ -~ CH~SiCI2CH3-+

(C6H~)2SiCICH3

~- C~H~CI~SiCH,

(9) (I0)

since triphenylmethylsilane (TI~MS) is absent in the reaction products and only t r a c e s of MTCS are p r e sent. After establishing equilibrium, DPMCS and MPDCS a r e p r e s e n t in the l a r g e s t amount in the r e a c tion m a s s , i.e., products that are f o r m e d according to s c h e m e (10). The concentration of DMPCS and DPDCS [scheme (8)] is 1.5-2 times less. It s e e m s that the reaction p r o c e e d s mainly according to scheme (10), but this contradicts the data that were obtained by us earlier, since s c h e m e (10) postulates the exchange of a methyl group in DMDCS, which fails to o c c u r either when it is r e a c t e d with PTCS [3] o r with DPDCS. The assumption r e m a i n s that the reaction p r o c e e d s according to scheme (8), while DPMCS and MPDCS are formed by the reaction of DMPCS with DPDCS C6H~CHsC1SiCH8 + C1Si(C6Hs)2C1--~CH3C~H~SiC12 + CH3C1Si(C6H~)2 C,H~CH3C1SiCHa + C6HsSiC12C6H~-+ CH3C,HsSiC12 -]- CH3C1Si(C6Hs)~ Actually, within 0.5h after the start of heating the amount of DPDCS products greatly exceeds the amount of MPDCS and DPMCS, i.e., scheme

1098

and DMPCS in the reaction (8) is realized at the start of

the p r o c e s s . F u r t h e r heating leads to a s h a r p d e c r e a s e in the yield of DPDCS and DMPCS, with a s i m u l taneous i n c r e a s e in the amounts of DPMCS and MPDCS, which c o r r o b o r a t e s the r e a l i t y of s c h e m e s (11, 12) (Fig. 3). As a result, DMDCS in a mixture with TPCS also reacts mainly with a replacement of the chlorine atom; the exchange of the chlorine atom in DMPCS apparently fails to occur, since dimethyldiphenylsilane (DMDPS) was not detected in the products. This again corroborated the results obtained by us earlier [i] concerning the tendency of compounds of type R'R2SiCI to exchange organic radicals under the described conditions, analogous to compounds of type R3SiCI, and specifically TPCS and TMCS. The reaction products also contain amounts of TMCS and MTCS, the formation of which apparently occurs via a disproportionation of DMDCS. Somewhat greater amounts of TMCS are also formed as the result of the reaction of either MDPCS or DMPCS with DMDCS. An increase in the amount of DMDCS in the starting mixture leads to an increase in MPDCS and DMPCS and a decrease in DPMCS and DPDCS. These changes are not associated with the progress of the main processes (8) or (I0), since an increase in the yield of DMPCS according to scheme (8) should lead to an increase in the concentration of DPDCS, while an increase in the yield of DPMCS according to scheme (i0} should lead to an increase in the concentration of MPDCS. Actually, the reverse relation is observed (Fig. 4). Apparently, in excess DMDCS the compound reacts with DPMCS. The yield of MPDCS and DMPCS decreases in excess TPCS, probably due to their reaction with the TPCS. EXPERIMENTAL A stuffy of the reaction of DPDCS scribed method [i, 3].

and TPCS

METHOD with DMDCS

was carried out using the previously

de-

CONCLUSIONS groups

i. In all cases dimethyldichlorosilane reacts with a replacement of diphenyldichlorosilane and triphenylchlorosilane.

of the chlorine atom by the phenyl

2. D~methylphenylchlorosilane and diphenylmethylchlorosilane react only with an exchange of the organic radical, in which connection with a predominant exchange of the methyl group in the case of dimethylphenylchlorosilane, and of the phenyl group in the case of diphenylmethylchlorosilane. The temperature, leaction time and ratio of the starting reactants all influence the composition of the reaction products. LITERATURE

1. 2. 3.

CITED

V . N . Penskii, V. V. P o n o m a r e v , S. A. Golubtsov, and K. A. Andrianov, Izv. Akad. Nauk SSSR, Ser. K h i m . , 876 (1972). V . N . Penskii, V. V. P o n o m a r e v , S. A. Golubtsov, and K. A. Andrianov, Izv. Akad. Nauk SSSR, Ser. K h i m . , 880 (1972). V . N . Penskii, V. V. P o n o m a r e v , S. A. Golubtsov, and K. A. Andrian0v, Izv. Akad. Nauk SSSR, Ser. K h i m . , 1898 (1971).

1099