COMMUNICATIONS TO THE EDITOR
3148
A Kinetic Study of Monochlorocarbene Insertion into Silicon-Hydrogen Bonds
Figure 1. Relative yield of the fragment ions of normal hexadecane us. their number of carbons: ionizing voltage 10 V and temperature of the ion source 105”: *, calculated value measured value. by eq 1 ; X, calculated value by eq 2; 0,
-1
P
-I
wk-
5.
\
4i
Sir: The carbene insertion reaction was thought to be a unique process for singlet methylene with the carbonhydrogen bond, but recently both it and CClz have been observed to insert into other types of single bonds.lt2 Singlet methylene inserts with ease into the Si-H bond of various methyl-substituted silanes.3-5 I n fact, it was found to insert into the Si-H bond 7-9 times faster than in the C-H bond of methylsilane, indicating that the Si-H bond insertion is one of the fastest methylene reactions k n ~ w n .Also, ~ ~ ~the insertion of CClz into Si-H and Si-C bonds of silacyclobutane has been performed recently.6 In the present work we wish to report the insertion of monochlorocarbene into the Si-€1 bond and a kinetic study on this insertion process. From our results it can be demonstrated that CHCl inserts into the Si-H bond more readily than it adds to the carbon-carbon double bond. The latter process was thought to be the most efficient carbene interaction.‘ Monochlorocarbene in the form of CTCl was produced by the hot atom excitation method.’t8 A recoil tritium atom with high kinetic energy may substitute for a hydrogen atom in CHzClz or CHzClF to give an excited molecule which decomposed by H X elimination to yield CTC1.
W
L
t
CHzClX
-I W
--
+
(r
CHTClX*
He3(n,p)Ha* T” --+ CHTClX*
decomposition
stabilization
CHTCIX* -Figure 2. Relative yield of the fragment ions of normal triacontane us. their number of carbons: ionizing voltage 17 V and temperature of the ion source 90’ : x, calculated value by eq 2; 0, measured value.
approximation in the calculation, the above agreement is satisfactory. The result thus obtained can b e summarized by the statement that when rapid, competitive scission occurs a t each bond of the parent ion, the two complemental fragments produced have a positive charge in the ratio of the relative probabilities given by the working hypothesis. It may be a new problem to investigate the relationship between Stevenson’s rule and the hypothesis introduced in this paper on other compounds than on normal alkanes. DEP.4RTMENT O F CHEMISTRY FACULTY OF SCIENCE OSAKAUNIVERSITY TOYONAK.4, OSAKA 560, JhP.4N
MITSUO SAITO Iwao FUJITA KO20
RECEIVED MARCH2, 1970 The Journal of Physical Chemistry, VoK ‘74,No. 16, 1970
HIROT.4
+H CTCl + H X CHTClX
(1) (2) (3) (4)
Reactants which include He3, CH2C1X, 02, silanes, and sometimes ethylene were sealed in 1720 Pyrex bulbs and were irradiated a t a neutron flux of 1013 neutrons/(cm2 sec) for 5 to 20 min. The products were analyzed with standard radio-gas chromatographic technique^.^ (1) W. Kirmse, “Carbene Chemistry,” Academic Press, Inc., New York, N. Y., 1964. (2) J. Hine, “Divalent Carbon,” The Ronald Press Co., New York, N. Y., 1964. (3) J. W. Simons and C. J. Mazac, Can. J . Chem., 45, 1717 (1967). (4) C. J. Mazac and J. W. Simons, J. Amer. Chem. Soc., 90, 2484 (1968). (5) W. L. Hase, W. G. Brieland, and J. W. Simons, J . Phys. Chem., 73, 4401 (1969). (6) D. Seyferth, R. Damrauer, and S. S. Washburne, J . Amer. Chem. Soc., 89, 1538 (1967). (7) (a) Y.-N. Tang and F. S. Rowland, ibid., 87, 1625 (1965); (b) zbzd., 89, 6420 (1967); (c) ibid., 90, 574 (1968). ( 8 ) For the formation and reactions of CHCl in solution, see G. L. Closs and J. J. Coyle, ibid., 87, 4270 (1965). (9) J. K. Lee, E. K. C. Lee, B. Musgrave, Y.-N. Tang, J. W. Root, and F. 8. Rowland, Anal. Chem., 34, 741 (1962).
COMMUNICATIONS TO THE EDITOR
3149
CTCl derived by the above method has been shown to add very efficiently to ethylene, giving cyclopropyl CTCl
X
T
+
H2C=CH2
-+
C1 (5)
chloride-t. At 33 to 60 cm total pressure the decomposition/stabilization ratio for CHTClX", expressed in the form of c-C3H4TC1/CHTCIX, was 0.30 f 0.02 for unscavenged and 0.23 f 0.03 for 02-scavenged CHzCl2 samples when measured in systems containing ethylene.7alo In the case of CH2C1F, the corresponding ratio for 02-scavenged samples is 0.10 f 0.01.7" The difference in the two ratios of scavenged and unscavenged CHzC12systems can be explained as follows. In the scavenged samples, about 1/4 of the CTCl is removed by O2 in one form or another, either before or after its interaction with ethylene. The 0.30 value from the unscavenged systems probably represents essentially the total amount of CTCl formed because there is nothing else in the system that can effectively compete with ethylene for the CTC1, and also any diradicals formed will have a chance to undergo a ringclosure process instead of being scavenged by 0 2 . I n the present work, we have treated CTCl with (CH&SiH (TMS) and (CH3)h3iH2(DMS) and have measured the yields of the corresponding Si-H insertion products, trimethylchloromethylsilane-t (TMCMS) and dimethylchloromethylsilane-t (DMCMS). H3C
CTCl
+ \ Si / H3C
CTCl
CH3
+
\ / Si / \
H3C
H3C
\
--r
H
(6)
Hac --f
H
Si
specific reactivities per bond. The large error is due to overlapping peaks. Only TMClIS-t or DMCMS-t were measured directly in most of the analyses. The values for c-C3H4TC1were obtained by taking the difference between 0.31, the expected CTCl production, and the observed chloromethylsilane yield. From the data in Table 11, one can see that on a per bond basis Table I : Results of CTCl Insertion into Si-H Bonds in Monosilane and hIethylsilanesa Reacting silane X
Y
\ /si\
Product ratiob
CTCl H
source
(CH3)&H
CHzClz
(CH3)zSiHn
CHzClF CH2Clz
SiH4
CHzClz
0 0 0 0 0 0
3 1 f O 03 32 I O 02 32 i 0 01' 14 f 0 01 32 f 0 03 30 i.0 01
