INFRARED SPECTRA OF METHYLACETOXYSILANE
July 5, l O G O
Preparation of Tetramethyl-1,s-diacetoxydistannoxane .A mixture of dimethyltin oxide (4 8.) and acetic anhydride ( 2 5 g.) was refluxed for one hour, followed by distillation of the excess anhydride with 20-30 cc. of xylene. From the methanol soltition of the product, which was evaporated on a hot plate, three portions of crystals amounting to 2 g., 1 g. and 1 g. were obtained. The first two portions of these crystals melted at 236-237'. The same substance was obtained when dimethyltin oxide was allowed to react with glacial acetic acid or 50y0 aqueous acetic acid. Recrystallization from methanol. by adding a small amount of acetic acid, gave crystals n hich melted a t 240" and then frothed up to leave a wauy solid and a small amount of crystalline sublin u t e . The results of analyses of both preparations are given i n Table I . Sublimation was not considered to be a suitable method to obtain a pure compound because of contamination with some decomposition products even under 1 mm . pressure. Attempts to Obtain Dimethy1diacetoxystannane.-A reaction of dimethyltin dichloride and acetic acid with
[CONTRIBUTION FROM
THE
3287
sodium acetate was carried out, but the product decomposed even when sublimation was carried out under 1 mm. pressure. A small amount of sublimate (m.p. 233') seemed t o be a dimeric compound which had a pungent acetic smell. Tetramethyl-l,3-diacetoxydistannoxane (3.7 9.) was allowed to react with an excess of acetic anhydride. During the course of sublimation, a large wet crystalline sublimate (2.59.) was obtained. These crystals had a pungent acetic smell, turned white on exposure to air and melted a t an indefinite temperature. Recrystallization from benzene gave a product composed mainly of the distannoxane. The reaction of dimethylchloroacetoxystannane with an excess of acetic anhydride did not give the desired compound.
Acknowledgments.-We are indebted t o the Metal and Thermit Corporation for the gift of some dimethyltin dichloride. This work was supported in part by the Office of Naval Research.
MALLIXCKRODT CHEMICAL LABORATORY OF HARVARDIUNIVERSITY, CAMBRIDGE, XfASSACHUSETTS]
The Infrared Spectra of the Methylacetoxysilanes and Some Methyltin Carboxylates. The Configuration of the Trimethyltin and the Dimethyltin Cations B Y ROKURO OKAWARA,~ DAVIDE. w E B S T E R 2 A N D EUGENE G. ROCHOW RECEIVED SEPTEMBER 18,1959 The infrared spectra of trimethylacetoxysilane, dimethyldiacetoxysilane, methyltriacetoxysilane and silicon tetraacetate have been examined over the range 1000-3500 cm. -I. Trimethyltin acetate, formate, chloroacetates, propionate and halides, dimethyltin acetate, formate and halides and monomethyltin halides have also been studied over thc range 4003500 cm.-'. The spectra of the silicon acetates are very similar to those of organic acetates, and it is concluded that the bonding is similar to that of an organic ester. The spectra of the tin acetate and other tin derivatives, on the other hand, show the presence of the carboxylate anion. Characteristic vibrations of the methyl-tin groups are found near 780 and 1200 cm.-'. The trimethyltin cation is found to have a planar structure, and the dimethyltin cation is linear.
The methylacetoxysilanes have been known for time, but on!y recently has a variety of methyltin esters ken prepared.3 As there is now an increasing interest in the organic derivatives of tin,
hydroxide with 50% hydrofluoric acid and was recrystallized. Melting points and analyses are given in Table I. The preparation of the dimethyltin derivatives has been reported.S Dimethyltin and methvltin halides were obt i n e d by the reacGon of the hydrohalogen acid with di-
TABLE I M..P., C.
( CH3)aSnOOCH ( CHJ)khOOCCHS ( CH,)LhOOCCH2CI ( CH3)~Sn00CCHC12 ( CH3)3Sn00CCCl~ ( CH3)JSnOOCCzH5 ( CH, hSnF Lit.6 196.5-197.5'.
151 197" 148 135 179 136
Sn
Anal., calcd.
56.84 53.27 46.13 40.69 36.39 64.93
we report the results of this comparative study of the infrared spectra of 24 compounds. Experimental The methylacetoxysilanes and silicon tetraacetate were prepared by the reaction of the corresponding methylchlorosilane or silicon tetrachloride with acetic anhydride.4 Trimethyltin salts other than the fluoride were obtained by the reaction of trimethyltin hydroxide and the corresponding acid, followed by purification by sublimation. The fluoride was prepared by neutralization of trimethyltin (1) Research Fellow in Chemistry at Harvard University, 19581959. (2) Research Fellow in Chemistry at Harvard University, 19581959. (3) R. Okawara and E. G. Rochow, THIS JOURNAL, 83,3285 (1960). (4) "Inorganic Syntheses," Vol. I V , McGraw-Hill Book Co., New York, N. Y . , 1953, p. 45.
C
H
Sn
23.01 26.95 23.34 20.58 18.41 30.42 19.71
4.83 5.43 4.31 3.46 2.78 5.96 4.96
56.88 53.39 46.21 40.87 36.37 64.94
A n d , found
.
C
H
23.37 26.75 23.79 20.84 18.41 30.28 19.73
4.83 5.56 4.71 3.75 2.67 6.01 4.76
methyltin oxide or methylstannoic acid. All the halides, except the fluoride, were identified by their melting points. The infrared absorption spectra were recorded using a Perkin-Elmer (Model 21) double-beam spectrophotometer equipped with NaCl or KBr6 optics. Spectra were calibrated using known peaks of a polystyrene film or of 1,3,5trichlorobenzene. The spectra of the silicon acetates are those of solutions in carbon tetrachloride. I n the NaCl region, the spectra of the methyltin halides, except the fluoride, are those of solutions in carbon tetrachloride and carbon disulfide. The other tin derivatives were insoluble, and the spectra were obtained using pressed KBr discs. In the KBr region, pure liquid, Nujol mull, and KBr discs were used. ( 5 ) G. J. M. van der Kerk and J. G. A. Luitjen, J . A p p l . Chcm., 6,4Q (1956). (6) We thank Dr. Nakamoto of Clark University, Worcester, Mass., for the use of his spectrophotometer equipped with KBr optin.
ROKURO OKAWARA, DAVIDE.~YEBSTER AND EUGENE G. ROCHOK
3288
Frequency, cm. -*. no00
2300
2000
Vol. 82
Frequency, cm. -I. 1300
1300
1200 1100
3000
- ~
100
1200
1500
~ ~--. ~
1000 ~
800 ~
_
700 _ ~
_
_
-7
u- 100 U
2 E
fiO
.c.' U .C
3
20
a 100 80
r80
20
', /
i
V n L -
-
LCC8t*)'iSn:23
___ . 8
6
4
Fig. 2.-Infrared
\J
10
12
~
14
Wave length, microns. absorption spectra of methyltin acetates.
The spectra of the three tin acetates in the region 6503500 cm.-' are given in Fig. 2.
TABLE 11" ISFRARED VIBRATIONAL FREQUENCIES OF (CH,),Si(OOCOF BANDS(IN CM.- I ) CH3)a-$: POSITIOXS r = 3 1018w
x = 2 1018m .. 1047w 1257s 1262s 1267s 1235s 1270s.h ( 1 2 9 1 ~ ) ~( 1 2 9 1 ~ ) 1377m 1377m 1430w 1430w (1725sh)* 1725s 1732s
..
1
CH3Si (OCOCH3)3
0
I
1047w 1279m 1220s 1262w (1291~) 1377s 1430w (1725~) 1748s
Assignment
CHsrock.
..
CHa(-Si) sym. deform. C-0(-Si) str.
1200s 1270w (1291~)
1377s CH3 sym. deform. 1430w CH3 asym. deform. (172.5~) 1765s C=O str.
TABLE 111 INFRARED VIBRATIOXAL FREQUEXCIES O F TRIMETHPLTIN A N D DIMETHYLTIN ACETATES: POSITIONS OF BANDS( I N CX.-'), R = OOCH3
I10 -
-
(CHdz- [R(CHs'zSnClR SnIzO
NaRa
664s
685s
647s
775s
795s 815sh 950w 1018m 1047w 1198w 1215w
(CHa)aSUR
I
4
I
I
6
1
I
8
m'ave length, microns. Fig. 1.-Infrared
r=O 1022s 1047w
a Frequencies over 2000 crn.-I are not shown in the tables. * T h e absorptions shown in the parentheses could be explained as those of acetic acid. The compounds shown in Table I are quite easily hydrolyzed t o give acetic acid.
I
-
0
r = l 1019s
absorption spectra of methylacetoxysilanes.
91Ow 1015m 1048w 1194111 1206m 1352111 . . 1428s 1413s
656s 666sh 696w 788s 94Ow 1024m 1053w 1197m
..
Assignment
COO scissor.
] CH,(-Sh) rock.
923m. C-C str. 1007111 1045mI
1
CH1(-Su) s y m . deform .. The vibrational frequencies of trimethylacetoxysilane, 1345m 1338w CHa sym. deform dimethyldiacetoxysilane, methyltriacetoxysilane and silicon tetraacetate are listed in Table 11, and the spectra in the 1410s 1425x11 COO svm. str. region 1100-3500 cm.-' are shown in Fig. 1. . . 1443sh 1430s 1440sh CH, asym. deform The compound dimethyltin diacetate could not be pre.. 1461s .. 1484sh pared, the products from dimethyltin dichloride being di1580s 1582s COO antisym str methylchlorotin acetate and tetramethyl-l,3-diacetoxy- 1576s 1564s a K. Nakamura, J . Chem. SOC. Japan, 79, 1411 (1958) (in distannoxane.3 The vibrational frequencies of these two compounds, together with those of trimethyltin acetate and Japanese). See also, L. H. Jones and E. McLaren, J . of sodium acetate for comparison, are shown in Table 111. Chem. Phys., 22, 1796 (1954).
)
July 5 , 1960 Frequency, cm.-'. '3000
_
~
_
-
~
~~-
700 600
500
----
3000 100 I '
400 1
60
1500 1200
-
Frequency, cm.-'.
Frequency, cm. -l
700
800
1500 1200 1000
100
3289
INFRARED SPECTRA OF LfETHYLACETOXYSILANE
700
1000 800 700 'I
500
20
0
100 60
~----7
L
"
20
,
-
, 'C"? 2 5 r C # . C 3 : , , " ~
~
L
_
_
4
~
Fig. 3.-Infrared
~
8
6
.
20 16
18 20
25
Wave length, microns.
__.___
~
10
12
& 1000 60
: 200 9 *
'!?
14
Wave length, microns. absorption spectra of methyltin formates.
The spectra of the trimethyltin and dimethyltin formates, chloroacetates and propionates are listed in Tables IV and V, and the spectra of the three tin formates are given in Fig. 3. To identify the bands associated with the methyl-tin groupings and to discuss their configurations, results from the study of certain methyltin halides are given in Table VI. In Fig. 4 are shown the spectra in the region 400-3500 cm.-l of the representative compounds in Table VI.
100
60 20
t - c o
100 60 20 0 100 GO
20 0
4 6 8 10 12 14 16 18 20 25 TABLE IV INFRARED VIBRATIONAL FREQUENCIES OF TRIMETHYLTIN Wave length, microns. Wave length, microns. AND DIMETHYLTIN FORMATES: POSITIONS OF BAXDS(IN Fig. 4.-Infrared absorption spectra of methyltin halides. C M . - ~ )R , = OOCH
Discussion The Methylsilicon and Methyltin Carboxylic Acid Derivatives.-The spectra of the acetoxy derivatives of silicon (Table 11) show the band associated with the carbonyl group7 a t 1725-1765
cm.-', the frequency increasing with an increasing number of acetate groups in the molecule. The band associated with the C-O(-Si) bond is found a t 1200-1267 cm.-', the frequency decreasing with an increasing number of acetate groups in the molecule. These two bands are as found in organic acetates,* and i t is concluded that in the acetoxysilanes the Si-0 bond is covalent. The spectra of the acetoxy derivatives of tin (Table 111) show completely different features from those of the methylacetoxysilanes. In all the tin compounds studied here, the spectra are interpreted as superpositions of the absorptions of the carboxylic acid anion and those of the methyltin cation. Freeman' has reported that di-n-butyltin acetate is an ionic compound. Assignment of the characteristic bands of the acetate ion can be made with certainty. The remaining strong band near 780 em.-' and the two sharp bands near 1200 cm.-l then can be assigned to the rocking and symmetric deformation vibrations of the methyl groups attached to tin. This assignment is supported by the spectra of the methyltin formates (Table I V ) . Most of the bands are readily assigned t o the formate ion; only slight differences occur between the tin derivatives and sodium formate. The main differences are the appearance of a strong band near 780 cm.-l and one, or two, sharp bands near 1200 cm.-l. These, as for the acetate, are assigned to methyl-tin vibrations. In the chloroacetates (Table V), the C-C1 bands are near the 780 cm.-l band but assignment is still possible. Characteristic Vibrations of the Methyltin Compounds and the Configuration of the Trimethyltin and Dimethyltin Cations.-Since the rocking vibra-
(7) J. P. Freeman, TEISJOURNAL,80, 5954 (19581, reports this band a t 1715 cm.-' for the trimethyl compound.
(8) L. J. Bellamy, "The Infrared Spectra of Complex Molecules," 2nd E d , Methuen, London, 1958.
(CHa)sSnRa
(CHdzSnRZa
770s 790sh
770s 800m
..
..
(CHs)zSnClR
789s 818 21 2s
..
NaRb
Assignment
. , CH3(-Sn) rock. 784 COO deform. 1070 CH out-of-plane bend. . . CH3(-Sn) syrn. .. deform. 1365 CH in-plane bend. 1377 COO syrn. str.
1195x11 .. .. 1205111 1202w 1204w 1363s 1373s 1325s 1378s 1390s 1375m 15g0s 1588s 1595s 1620 COO antisym. str. 1615s a In the KBr region, only one strong band is found a t 552 em.-' in the spectrum of (CHZ)&hOOCH and a t 592 em.-' in (CHs)zSn(OOCH)2. R. Newman, J . Chem. Phys., 20, 1663 (1952). See also, K. Ito and H . J. Bernstein, Cunad. J . Chem., 34, 170 (1956).
TABLE V METHYL(-TIN) VIBRATIONAL FREQUENCIES A S D THE cos STRETCHISG FREQUENCIES O F THE CHLOROACETATES AND PROPIONATE IONS: P O S I T I O X S O F BANDS ( I N (!M.-'), ( CH3)3Sn00CR R = CHz CHs
775 1192 1202 1433 157-1
CHzCl
CHClz
CCIs
772 1195
1418
765 1195 1206 1393
1640
:i
765 Or 783 1196
..
1660
1
Assignment
~
..
CH3(-Sn) rock. CH3(-Sn)sym. deform.
1352 j 1656
1
COO str.
GEORGEE. RYSCHKEWITSCH
3290
TVPRARFD \'TBRATIONAL FREQUENCIES O F
X -
(CHdsSnX CI nr n 1
F La
513m 555s
782s
545s 722m 782s
I 1
512m
509m
543s 723w 781s
540s
720w 780s
TABLE VI MBTHYLTIN ITA1 IDES IK CM -1)
---k
(CHs)zSnX-Rr k,n
1 n
515s
514s
511m
c1
567s 745w 786s
563s 743sh 779s 790sh 1198w
400-1500
TIIE I
