723
PROTON RESONANCE SPECTRA OF MONO-,DI-, AND TRISUBSTITUTED SILANES
Proton Resonance Spectra of Selected Mono-, Di=,and Trisubstituted Silanes]
by H. J. Campbell-Ferguson, E. A. V. Ebsworth, A. G. MacDiarmid, and T. Yoshioka University Chemical Laboratory, Cambridge, England, and Department of Chemistry and the Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (Received June 20,1966)
The proton nuclear magnetic resonance spectra of H2Si(OCH3)2,H2Si(OSiH3)2,H,Si [N(CH3)2]2,HSi(OCH3)3, HSi(OSiH3)s, HSi [N(CH3)2]3,HSiBr3, and HSiI3 have been exdata for these compounds are presented. amined and proton chemical shift and JsPsi, The values are compared with analogous data for H,SiX4-, (X = F, C1, Br) compounds and with values for the corresponding methane derivatives where available. I n all cases, the chemical shifts of the protons attached directly to the central silicon or carbon move downfield with increasing substitution, with the exception of the series H,SiX4-, (X = F, N(CH3)2,OCH3, OSiH3), where an unexpected upfield shift is observed. Possible reasons for the different trends in chemical shift values and certain relationships between JlSs,=values are discussed.
I n the course of some investigations into the reactions of silyl compounds, we have measured the proton resonance spectra of SiHBr3, SiH13, and compounds of formula SiH,X4-,, where X = OCH3, OSiH3, or N(CH3)2. The chemical shifts are presented in Table I and coupling constants in Table 11, together with the corresponding parameters for the other halomonosilanes. Long-range H-H coupling was not detected. The way in which the chemical shifts change with increasing substitution depends on the substituent in an interesting way. I n the chloro-, bromo-, and iodosilanes, r(SiH) decreases with increasing substitution (Table I), as does T(CH) in the analogous series of halomethanes, including the fluorides.2 This is the direction in which the chemical shifts would be expected to change if they were determined by changes in u-electron density at carbon and silicon, respectively. I n marked contrast, it has previously been noticed that in the fluorosilanes, T(SiH) actually increases with increasing substitution; the data in Table I show that n similar over-all upfield shift occurs with increasing oxygen and nitrogen substitution at a silicon atom. Since the factors that determine the SiH chemical shift are still ill defined, it is at present impossible to offer an explanation for the effect of fluorine, oxygen, or nitrogen substitution; but it is interesting that these three elements are commonly believed to form the
Table I : Chemical Shift Values for SiH,X4-,“ Compound
SiH3Clb SiHzC126 SiHCl? SiHtBrb SiHzBrzb SiHBra SiH31b SiHJ2b SiHI3
r(SiH)
Compound
T(SiH)
5.41 4.60 3.93 5.83 4.83 3.70 6.56 5.97 5.51
SiH3Fb SiHzFZb SiHF? SiH3N (CH3)ZC SiH?[N(CHa)?] SiH[N(CH3)?13 SiH30CHa SiHz(OCH3)2 SiH (OCHa)3 SiHaOSiH? SiHz(0SiH3)2 SiH(0SiHa)s
5.24 5.29 5.49 3.64 5.62 5.87 5.51 5.58 5.91 5.39 5.46 5.82
r(CH3) r ( O S i H 8 )
... ... ... 7.51 7.49 7.56 6.58 6.48 6.51
... ... ...
...
...
...
... ...
...
... ... ,
,.
5.39 5.33 5.34
‘All measurements carried out in cyclohexane solutions. Values given are extrapolated to infinite dilution except for the methoxy- and siloxysilanes, which were all measured a t 25% (vol.) concentration. Conversions to 7 scale based on CBHIZ being 1.44 ppm downfield from (CH3)aSi. Error in values E. A. V. Ebsworth and J. J. Turner, quoted is 5 f 0 . 0 1 ppm. J. Phys. Chem., 67, 805 (1963). J. C. Thompson, private communication. (1) A portion of this study was supported by the Advanced Research Projects Agency, Office of the Secretary of Defense, Washington, D. C. (2) A. A. Bothner-by and C. Naar-Colin, J . Am. Chem. SOC.,80, 1728 (1958); E. A. 1’. Ebsworth, “Volatile Silicon Compounds,” Pergamon Press Inc., New York, N. Y.,1963,p 23.
Volume 7 1 , Number 8 February 1967
724
H. CAMPBELL-FERGUSON, E. EBSWORTH, A. MACDIARMID, AND T. YOSHIOKA
Table I1 : Coupling Constant Parameters for SiH,X4-,"
JzosiH(obsd),
Compound
CPS
SiH3F SiHZFZ SiHF3 SiH3Cl SiHZClZ SiHCI3 SiHaBr SiHZBrz SiHBr3 SiHJ SiHA SiHI3 SiHaOCHa SiH*(OCH3)2 SiH(OCH3)3 SiHsOSiH3 SiHt(OSiH3)2 SiH(OSiH3)s SiHaN(CH3)z SiHz[N(CH3)2]z SiH [ N ( C H ~ )3Z ] a
229.0 i 0.6' 282 i 3' 381.7 f 1.5" 238.1 i 0.2' 288.0 f 0.4' 362.9 f 0.2' 240.5 i 0.3' 289.0 f 0.6' 357.3 240.1 i 0.2' 280.5 i 0.2' 325.1 216.2 247.6 f 0 . 6 d 297.9 f 0 . 3 d 221.5 i 0 . 2 d 256.6 f 0 . 3 d 316.0 i 0 . 5 d 205.7 i 0 . 5 e 217.6 i 0 . 4 235 f 1 . 0
JzosiH(obsd)
JisCH(obsd)
(SiHaO-),
(CHsN-),
A,b
lOOA/
CPS
OPS
CPS
CPS
J(obsd)
... ...
... ..*
...
...
...
255.5 282.0
-26.5 -99.7
9.40 26.12
273.7 309.3
-14.3 -53.6
278.5 316.5
-10.5 -40.8
...
... ... ... ... ... ... ... ...
... ...
...
... ... ...
...
...
... ... ...
...
... ...
... ...
221.5 i 0.2d 222.9 i 0.6d 223.4 f 0.6d
...
...
JmgiH(add),
...
...
...
t
.
.
4.96 14.77
... 3.63 11.42
...
...
...
277.7 315.3
-2.8 -9.8
1.00 3.11
...
...
229.9 243.6
-17.7 -54.3
7.15 18.23
...
...
...
240.5 259.5
-16.1 -56.5
6.27 17.88
-22.9
4.00 9.74
...
... 135 i 2
212.1
Dln
D
0.3625 1.0294 2.1318 0.4821 1.1008 1.9361 0.5133 1.1126 1.8768 0.5081 1.0114 1.5266 0.1902 0.6046 1.2170 0.2622 0.7184 1.4245 0.0450 0.2093 0.4417
0.3625 0,5147 0,7106 0,4821 0.5504 0,6454 0.5133 0.5563 0,6256 0.5081 0,5057 0.5089 0.1902 0.3023 0.4057 0.2622 0,3592 0.4748 0,0450 0.1046 0,1472
D and D / n values were recalculated in this study. A value of J29~i~(SiH4) = 202.5 cps was used in all calculations. (See ref 9.) E. A. V. Ebsworth and J. J. Turner, J. Chem. Phys., 36, 2628 (1962). Error is expressedin
A = JsssiH(obsd) - JzssiH(add).
terms of a 95'1, confidence limit from the arithmetic mean. Thompson, private communication.
See R. B. Dean and W. J. Dixon, Anal. Chem., 23, 636 (1951).
strongest (p -P d ) r bonds to silicon. Such 7r bonding seems to be weaker to germanium3 than to silicon; in the fluorogermanes, 7(GeH) decreases with increasing fluorine substitution, as in the other halogermanes so far s t ~ d i e d . ~ ~Ialinowski5calculated 13CH coupling constants for the simple halomethanes CHtC12, CHC13, CH2Br2, and CHJ2, as well as for other more complex molecules from the experimentally determined I3CH coupling constants in CH3X and CHI, using a relationship which, for such compounds, may be expressed as JiaCH(C&-,-Y,)
=
+
Jisc~(CH4)
n [J1scH(CH3X) - J1ac,(CHd)
I
(1)
Good agreement between the calculated [Jls,,(add)] and experimental Jlsca values was obtained in all cases; however, subsequent calculations for CH2F2, CHFs, CHz(OCH3)zi and CH(OCH3)3 gave poor agreement between the calculated and experimental values.6 When a similar treatment was applied by Juan and Gutowsky' 29SiH constants Of silicon com~ounds,the agreement between the calm was very poorcdated and experimental This treatment has been extended to the compounds The Journal of Physical Chemistry
E
J. C.
studied in this investigation; and the differences, A, between the calculated [Jzss,,(add) ] and experimental 29SiHcoupling constants are given in Table 11. It can be seen that A decreases in the order F > -OCH3 > -OSiH3 > C1 > Br > -N(CH3)2 > I for SiH2X2compounds. For SiHX3 compounds, the order is the same except for the fact that the position of the -OCH3 and -OSiH3 groups is reversed. The value of A increases with increasing substitution. The percentage deviations, 100A/J23s,H, which are probably somewhat more significant, also follow the same general order, except that in the case of SiH2X2 compounds the positions of Br and N(CH& are reversed, while in the case of the HSiX3 species the order is followed exactly. More recently, Reeves6 has calculated deviation (3) J. E. Griffiths and K. B. McAfee, Jr., Proc. Chem. Soc., 456 (1961). (4) E. A. V. Ebsworth, S. G. Frankiss, and A. G. Robiette, J . i1.102. Spectry., 12, 299 (1964). ( 5 ) E.Malinowski, J . A m , Chem. Sot., 83, 4479 (1961). (6) N. Muller and P. I. ~ o s eibid., , 84,3973 (1962). (7) C. Juan and H. 9. Gutowsky, J. Chem. Phys., 3 7 , 2198 (1962). (8)L. w. Reeves, {bid., 40, 2128 (1964).
PROTON RESONAXCE SPECTRA OF hIoNo-, DI-,
Table 111:
J18CH
CHIF CHzFz CHF3 CH&l CHzClz CHCl, CHaBr CH2Br2 CHBr3 CHBI CHzIz CHI3 CH30CH3 CHz(0CHa)z CH(OCHI)I
TRISUBSTITUTED SILAKES
725
Parameters for CH,X4-,a JiaCH(obsd).
Compound
AND
CPS
149’ 18jd 23F 150” 178csf 209’1~ 152O 178p 206c 15lC’J 173“ ... 140e 162e 186e
JiaCH(&dd),
A,b
lOOA/
CPS
CPS
J(obsd)
... 173 197
...
...
-41
6.49 17.23
- 12
...
...
179 206
1 -3
.
I
.
...
...
0.56 1.43 .
I
.
1 0
...
...
0.56 0.00
177
4
2.25
179 206
... ... 155 170
...
... -7
- 16
...
... ... 4.32 8.60
D
0.3664 0.8645 1.5164 0.3810 0.7717 1.1699 0,4101 0.7717 1,1327 0.3956 0.7043
D/n
0.3664 0.4322 0.5055 0.3810 0.3859 0.3900 0.4101 0.3859 0,3776 0.3956 0.3522
...
...
0,2327 0.5526 0.8776
0.2327 0,2763 0.2925
‘
’D and D / n values mere recalculated in this study. A value of J I ~ C E ( C H=~ ) 125 cps was used in all calculations (see ref 9). A = JiJcH(obsd) - Jl:icH(add). N. Muller and D. E. Pritchard, J . Chem. Phys., 31,1471 (1959). N. hiuller, ibid., 36,359 (1962). See ref 6. G. V. D. Tiers, J. Phys. Chem., 64, 373 (1960). See ref 5 . parameters “D” for a number of compounds, among which were many analogous carbon and silicon molecules. For such compounds
where J ~ ~ is Bthe -H coupling constant in JAp-H is the coupling constant in the substituted molecule (hIH,X4-,), and 711 and Y H are the corresponding gyromagnetic ratios. Values of D and D / n for the compounds discussed by Reevesg as well as for the compounds studied in this investigation are given in Tables I1 and 111. It can be seen from Table I1 that the variation in the deviation parameters per bond, D / n , within a given series of silicon compounds, descreases in the order F > CH30 SiH30 > C1 > Br > X(CH3)Z > I. It is interesting to note that this order is essentially identical with that obtained from the A or 100A/J20s,, values, which are obtained from a somewhat different method of approach. For the carbon compounds listed, the value of D / n is very much more constant within a given series, and it varies appreciably only for the fluoromethanes. For any given series, the variation of D / n values is very much greater for the silicon compounds than for the analogous carbon species, with the excepl ion of the iodides. It might be stressed that, in certain extreme cases, a series of some silicon compounds behaves more “additively” than a series of carbon compounds. For example, I OOA/JlacH for C H 2 R = 6.49%) whereas 100A/Jzss,H = l . O O ~ o for SiH212. Also, the variation
in D / n values for the fluoromethanes is 0.1391, while that for the iodosilanes is 0.0032. If it is assumed that (p + d ) r bonding between fluorine and carbon is small in the fluoromethanes, then it appears possible that the “abnormaP” behavior of the fluoromethanes may be due to polarization of the carbon by the fluorine atoms. If this should be the case, then the greater “abnormal” behavior in analogous silicon compounds may be due to the greater polarizability of silicon as compared to carbon, as suggested by Juan and Gutowsky.’ It is noteworthy that the relative magnitude of 100A/ J 2 s s l H or D / n for a given subsituent might reasonably represent its relative polarizing power. r bonding might also contribute to the deviations, but it seems unwise to attempt to relate them primarily to Tbonding effects and to use one explanation for “abnormal” effects in the substituted methanes and another explanation of abnormalities observed in the substituted silanes.
Experimental Section SiH, [N(CH&], and SiH [N(CH,),], were obtained according to the method described by Aylett and Peterson.’O Tribromosilane was obtained by the reaction of SiH [S(CH3)2]3 with HBr. Triiodosilane was obtained from the reaction of SiH, with H I in the presence of aluminum iodide catalyst at l l O o . l l -1Iethoxysilane was synthesized from (SiH&S and (9) P. T. Inglefield and L. W. Reeves, J . Chem. Phys., 40, 2424 (1964). (10) B. J. (11) H. J.
Aylett and L. K. Peterson, J . Chem. Soc., 3429 (1964). Emelbus, A. G. Maddock, and C. Reid, ibid., 353 (1941).
Volume 7 1 , Number S
February 1967
726
L. W. NICHOL,A. G. OGSTON, AND D. J. WINZOR
CH30H.12 The compounds (CH30)2SiH2and (CH30)3SiH were prepared by the base-catalyzed condensation of CH30SiH3.l 3 The compounds (SiH30)2SiH2 and (SiH30)3SiHwere obtained by the base-catalyzed condensation of (SiH3)20.13The nmr spectra of SiHBr3 and SiH13 were measured using a Perkin-Elmer HRlO spectrometer operating at 60 Alc/sec. The dimethylaminosilanes were recorded using a Varian Associates V4300B spectrometer operating at 40 Mc/sec; and the methoxy- and siloxysilanes were measured with a
Varian Associates HR60 spectrometer, Model 4300D, with flux stabilizer, operated at 60 Mc/sec. Acknowledgment. H. J. C.-F. wishes to acknowledge the receipt of a maintenance grant from the D.S.I.R. during the time that these experiments were being performed. (12) G. S. Weiss and E. R. Nixon, Spectrochim. Acta, 21, 903 (1965). (13) T. Yoshioka and A. G. MacDiarmid, Abstracts of 149th
National Meeting, American Chemical Society, Detroit, Mich., Sept 1964, p 5M.
Reaction Boundaries and Elution Profiles in Column Chromatography
by L. W. Nichol, A. G. Ogston, and D. J. Winzor Russell Grimwade School of Biochemistry, University of Melbourne, Victoria, Australia, Department of Physical Biochemistry, J o h n Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory, Australia, and C.S.I.R.O. Wheat Research U n i t , North R y d e , N e w South Wales, Australia (Receised June 37, 1966)
The relationships between the forms of migration boundaries within a chromatographic column and the forms of the elution profiles are examined by a method which makes use of constituent concepts of concentration and velocity of migration. The treatment applies to any procedure of column chromatography in which a plateau of all solute concentrations is ensured throughout the experiment. It is shown that the constituent concentration of any solute species in the effluent fluid is at any moment identical with that in the mobile solution within the column which reaches the exit plane at that time. I n addition, equations are derived in both differential and integrated form describing essential features of the elution profiles obtained with systems affected by chemical or physical interaction. It is concluded that the equations are formally identical with those obtained previously to describe migration patterns obtained in moving boundary experiments not involving a stationary phase, provided elution volumes are substituted directly for velocity terms. The conclusion is in agreement with other workers who considered the case of chemically reacting systems subjected to column chromatography.
Theoretical discussion of the forms of migration boundaries in interacting systems has been along two lines. Gilbert’s2 and Gilbert and Jenkins3 did Dioneer work in describing boundaries in freely migrating, chemically interacting systems ; Ackers and Thompson4 their method to the behavior Of a have merizing system in gel filtration. A later alternative T h e Journal of Physical Chemistry
approach uses “constituent” concepts of velocity and c o n ~ e n t r a t i o n :this ~ ~ ~approach has been developed in (1) G. A. Gilbert, Discussions Faraday Sac., 20, 68 (1955). (2) G. A. Gilbert, PTOC. Roy. SOC.(London), A250, 377 (1959). (3) G. A. Gilbert and R. C. L. Jenkins, ibid., A253, 420 (1959). (4) G. K.Ackers and T. E. Thompson, Proc. Natl. Acad. Sci. U.S., 53,342 (1965).
