Properties and Reactions of Organosilanes and Organogermanes Containing the Potentially Bidentate (X(CH2)n)2N-Group

Article abstract of DOI:10.1081/SIM-120026551

Compounds in the series R₃SiN[(CH₂) _nX]₂ (R = (CH₃)₂H, (CH ₃)₂Cl, and CH₃ClH), R₂Si[N((CH ₂)_nX)₂]₂ (R = (CH₃) ₂, C₆H₅H, and C₆H₅Cl), R₃GeN(CH₂X)₂ (R = (CH₃) ₂Cl and (C₆H₅)₂Cl), and Cl ₂Sn[N-((CH₂)₃X)₂]₂, for X = N(CH₃)₂, n = 3; and OCH₃, n = 2, have been prepared and characterized by ¹H, ¹³C and ²⁹Si NMR spectroscopy, and by elemental analyses. For all the compounds studied, the terminal N(CH₃)₂ and OCH₃ groups appear not to coordinate to the central atom. The product C₆H ₅Si{N[(CH₂)₂OCH₃]₂} ₂B[3,5-(CF3)2C6H3]4, obtained from a reaction between C ₆H₅HSi{N[(CH₂)₂OCH₃] ₂}₂ and (C₆H₅)₃CB[3,5- (CF₃)₂C₆H₃]₄, should contain a silylium ion, but because of the suspected presence of a small quantity of silyl radical, has thus far eluded definitive characterization.

Full text of DOI:10.1081/SIM-120026551

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Properties and Reactions of Organosilanes and
Organogermanes Containing the Potentially Bidentate
(X(CH2)n)2N‐Group
Heather D. Harle a , Sela Han a , Claude H. Yoder a , Charles D. Schaeffer Jr. b , Paula L.
Falen b , Brian J. Frost b , Sharon R. Hatalla b , Stephanie D. Kerstetter b , Jennifer K.
Redline b , Samantha L. Uliana b & Lisa L. Walton b
a Chemistry Department , Franklin and Marshall College , Lancaster, Pennsylvania,
17604‐3303, USA
b Chemistry Department , Elizabethtown College , Elizabethtown, Pennsylvania, 17022‐2298,
USA
Published online: 15 Feb 2007.
To cite this article: Heather D. Harle , Sela Han , Claude H. Yoder , Charles D. Schaeffer Jr. , Paula L. Falen , Brian J. Frost ,
Sharon R. Hatalla , Stephanie D. Kerstetter , Jennifer K. Redline , Samantha L. Uliana & Lisa L. Walton (2003) Properties
and Reactions of Organosilanes and Organogermanes Containing the Potentially Bidentate (X(CH2)n)2N‐Group, Synthesis and
Reactivity in Inorganic and Metal-Organic Chemistry, 33:10, 1825-1834, DOI: 10.1081/SIM-120026551
To link to this article: http://dx.doi.org/10.1081/SIM-120026551
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SYNTHESIS AND REACTIVITY IN INORGANIC AND METAL-ORGANIC CHEMISTRY
Vol. 33, No. 10, pp. 1825–1834, 2003
Properties and Reactions of Organosilanes and
Organogermanes Containing the Potentially
Bidentate (X(CH2)n)2N-Group
Heather D. Harle,1 Sela Han,1 Claude H. Yoder,1,
*
Charles D. Schaeffer Jr.,2 Paula L. Falen,2 Brian J. Frost,2
Sharon R. Hatalla,2 Stephanie D. Kerstetter,2
Jennifer K. Redline,2 Samantha L. Uliana,2
and Lisa L. Walton2
1Chemistry Department, Franklin and Marshall College, Lancaster,
Pennsylvania, USA
2Chemistry Department, Elizabethtown College, Elizabethtown,
Pennsylvania, USA
ABSTRACT
Compounds in the series R3SiN[(CH2)nX]2 (R = (CH3)2H, (CH3)2Cl, and
CH3ClH), R2Si[N((CH2)nX)2]2 (R = (CH3)2, C6H5H, and C6H5Cl),
R3GeN(CH2X)2 (R = (CH3)2Cl and (C6H5)2Cl), and Cl2Sn[N-
((CH2)3X)2]2, for X = N(CH3)2, n = 3; and OCH3, n = 2, have been pre-
1
pared and characterized by H, 13C and 29Si NMR spectroscopy, and by
elemental analyses. For all the compounds studied, the terminal N(CH3)2
*
Correspondence: Claude H. Yoder, Chemistry Department, Franklin and Marshall
College, Lancaster, PA 17604-3303, USA; E-mail: claude.yoder@fandm.edu.
1825
DOI: 10.1081/SIM-120026551
0094-5714 (Print); 1532-2440 (Online)
www.dekker.com
Copyright D 2003 by Marcel Dekker, Inc.

1826
Harle et al.
and OCH3 groups appear not to coordinate to the central atom. The
product C6H5Si{N[(CH2)2OCH3]2}2B[3,5-(CF3)2C6H3]4, obtained from
a reaction between C6H5HSi{N[(CH2)2OCH3]2}2 and (C6H5)3CB[3,5-
(CF3)2C6H3]4, should contain a silylium ion, but because of the sus-
pected presence of a small quantity of silyl radical, has thus far eluded
definitive characterization.
Key Words: Organosilanes; 29-Si NMR; Silylium ion.
INTRODUCTION
Our previous investigation[1] of organosilanes containing C6H5SiH- and
(C6H5)2SiH-attached to the potentially bidentate (X(CH2)n)2N-group (where
X = N(CH3)2 and OCH3, and n = 2, 3) indicated that these compounds,
unlike the amines and alkoxides reported by Corriu and others,[2–6] exhibit
no intramolecular coordination. In order to further explore the ‘‘anoma-
lous’’ behavior of compounds containing these potentially bidentate groups,
we have prepared an additional set of organosilanes and organogermanes
with methyl and chloro attached to the silicon and germanium to enhance
the Lewis acidity of the central atom. Coordination of the X group to the
silane might be expected to produce either five- or six-coordination as
shown below for a six-coordinate dimethylamino complex.
Because of the reactivity of the Si–H group with trityl salts and
consequent formation of a silylenium ion, we have also explored this
possibility with the derivative C6H5HSi{N[(CH2)2OCH3]2}2.
EXPERIMENTAL
General Considerations and Starting Materials
Reactions were performed with glassware dried in an oven at 110 °C for
at least one hour. All procedures involving potentially moisture- and oxygen-
sensitive materials were conducted in an argon-filled glove bag or under a

Organosilanes and Organogermanes
1827
stream of argon. Solvents and triethylamine were dried over Linde 4A
molecular sieves for at least one day prior to use, except for tetrahydrofuran
(THF) which was distilled under nitrogen from calcium hydride and then
stored over molecular sieves. All starting materials, including trityl triflate
(tritylium trifluoromethanesulfonate) and n-butyllithium (a 2.5 M solution in
hexane) were purchased commercially from Fluka/Aldrich Chemical
Company and were used without further purification.
Procedure
Silyl and germyl amines were prepared by standard amination pro-
cedures[7] utilizing stoichiometric amounts of the amine and triethylamine
in THF or diethyl ether to which was added dropwise the chlorosilane
(germane) at room temperature. Solvent was removed in vacuo. The stannyl
amine was prepared by lithioamination[8] using the lithium salt of HN[CH2-
CH2CH2N(CH3)2]2 (prepared from n-butyllithium and the amine). Sodium
tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (sodium TFPB) was obtained
according to the method of Bahr and Boudjouk,[9] and involved treating the
Grignard reagent resulting from the reaction of magnesium turnings with
3,5-bis(trifluoromethyl)-1-bromobenene in dry diethyl ether with dry solid
sodium tetrafluoroborate. The resulting suspension was then treated with a
saturated aqueous sodium chloride solution. The organic layer was separated,
and the aqueous layer was extracted with ether. The combined ether extracts
were dried, and the tan-colored solid product was isolated by ether removal
under vacuum. Triphenylmethylium tetrakis[3,5-bis(trifluoromethyl)phenyl]-
borate (trityl TFPB) was secured according to the method of Bahr and
Boudjouk,[9] and involved the 1:1 reaction of sodium TFPB with commercial
trityl triflate in dry methylene chloride, followed by vacuum filtration,
reduction of the filtrate volume under vacuum by two-thirds. Sufficient
hexane was added to induce crystallization of the bright yellow solid product.
Physical properties and NMR spectral data for both sodium TFPB (in
CD3CN) and trityl TFPB (in CDCl3) matched those previously reported.[9]
Addition of a methylene chloride solution of C6H5SiH{N[(CH2)2OCH3]2}2
to a magnetically-stirred methylene chloride solution of trityl TFPB main-
tained at 0 °C, followed by removal of methylene chloride under vacuum and
addition of a small quantity of hexane, precipitated a small quantity of the tan
solid C6H5Si{N[(CH2)2OCH3]2}2B[3,5-(CF3)2C6H3]4.
Representative Preparation:
(CH3)2Si{N[(CH2)2OCH3]2}2
Bis(2-methoxyethyl)amine (24.4 g, 0.183 mol) and triethylamine
(20.4 g, 0.201 mol) were transferred to a 500 mL three-neck round bottom

1828
Harle et al.
flask containing 250 mL of anhydrous diethyl ether equipped with a
magnetic stirring bar and water condenser. Dimethyldichlorosilane (11.8 g,
0.0914 mol) and ether (75 mL) were added dropwise at ambient tem-
perature from a 125 mL pressure-equalizing dropping funnel charged in a
glove bag. An immediate thick white precipitate of triethylamine hydro-
chloride formed. The reaction mixture was stirred magnetically for two
hours after addition. The bulky amine hydrochloride precipitate was
separated from the pale yellow reaction mixture by vacuum filtration in a
glove bag through a 150 mL coarse porosity fritted funnel covered with a
thin layer of oven-dried Celite 5451. The Celite was washed with one 20
mL portion of ether. The filtrate was collected in a 250 mL one-neck
1
round-bottom flask. Volatiles were removed under vacuum until H and 13C
NMR spectra indicated the absence of spurious signals. The resulting
soluble dark orange high-boiling viscous liquid could not be distilled even
at reduced pressure or recrystallized.
Analyses and NMR Measurements
Carbon and hydrogen combustion analyses were conducted by
Schwarzkopf Microanalytical Laboratories, Woodside, NY. All NMR spec-
tra were obtained on either a JEOL FX90Q Fourier transform NMR spec-
trometer equipped with a Tecmag/Macintosh pulse and data system or a
Varian UNITY 300 spectrometer.
Products
CH3ClHSiN[(CH2)2OCH3]2. 1H NMR (CDCl3, d): 5.08 (q, SiH,
3J(1H-1H) = 2.4 Hz), 3.53 (m, OCH2), 3.40 (s, OCH3), 3.05 (m, CH2), 0.62
3
(d, SiCH3, J(1H-1H) = 2.4 Hz). 13C NMR (CDCl3, d): 71.7 (OCH2), 58.0
(OCH3), 47.2 (CH2), 0.4 (SiCH3). 29Si NMR (CDCl3, d): ꢀ2.7 (1J(29Si-1H)=
253.9 Hz). Anal. Calcd for C7H18ClNO2Si (211.8): C, 39.70; H, 8.57. Found:
C, 39.57; H, 8.73.
(CH3)2ClSiN[(CH2)2OCH3]2. 1H NMR (CDCl3, d): 3.60 (m, OCH2),
3.50 (s, OCH3), 3.09 (m, CH2), 0.60 (s, Si(CH3)2). 13C NMR (CDCl3, d):
71.9 (OCH2), 58.3 (OCH3), 46.5 (CH2), 1.6 (Si(CH3)2). 29Si NMR (CDCl3,
d): 14.1. Anal. Calcd for C8H20ClNO2Si (225.8): C, 42.56; H, 8.93. Found:
C, 43.57; H, 9.63.
(CH3)2Si{N[(CH2)2OCH3]2}2. 1H NMR (CDCl3, d): 3.63 (m, OCH2),
3.40 (s, OCH3), 2.87 (m, CH2), 0.22 (s, Si(CH3)2), 13C NMR (CDCl3, d): 72.3

Organosilanes and Organogermanes
1829
(OCH2), 57.7 (OCH3), 45.9 (CH2), ꢀ2.1 (Si(CH3)2). 29Si NMR (CDCl3, d):
ꢀ1.8. Anal. Calcd for C14H34N2O4Si (322.5): C, 52.14; H, 10.63. Found: C,
51.45; H, 10.48.
C6H5ClSi{N[(CH2)2OCH3]2}2. 1H NMR (CDCl3, d): 8.05–7.62 (m,
C6H5), 3.75 (m, OCH2), 3.45 (s, OCH3), 3.27 (m, CH2). 13C NMR (CDCl3,
d): 138.4, 133.2, 130.0, 127.5 (C6H5), 71.8 (OCH2), 58.2 (OCH3), 45.6
(NCH2). 29Si NMR (CDCl3, d): ꢀ16.9. Anal. Calcd for C18H33ClN2O4Si
(405.0): C, 53.38; H, 8.21. Found: C, 53.49; H, 8.28.
C6H5HSi{N[(CH2)2OCH3]2}2. 1H NMR (CDCl3, d): 7.86–7.40 (m,
C6H5), 5.15 (s, SiH), 3.60 (m, OCH2), 3.45 (s, OCH3), 3.30 (m, CH2). 13C
NMR (CDCl3, d): 135.8, 134.2, 129.0, 127.2 (C6H5), 72.2 (OCH2), d 58.0
(OCH3), 46.2 (NCH2). 29Si NMR (CDCl3, d): ꢀ16.4. Anal. Calcd for
C18H34N2O4Si (370.6): C, 58.34; H, 9.25. Found: C, 58.00; H, 9.28.
(CH3)2HSiN[(CH2)3N(CH3)2]2. 1H NMR (CDCl3, d): 4.35 (br, SiH),
2.71 (m, CH2), 2.12 (m, CH2), 2.12 (s, N(CH3)2), 1.56 (m, CH2), 0.04 (d,
Si(CH3)2). 13C NMR (CDCl3, d): 56.9 (NCH2), 44.9 (N(CH3)2), 44.6 (CH2),
27.3 (CH2), ꢀ2.1 (Si(CH3)2). 29Si NMR (CDCl3, d): ꢀ6.5. Anal. Calcd for
C12H31N3Si (245.5): C, 58.71; H, 12.73. Found: C, 57.99; H, 12.90.
(CH3)2ClSiN[(CH2)3N(CH3)2]2. 1H NMR (CDCl3, d): 2.75 (m, CH2),
2.08 (m, CH2), 2.08 (s, N(CH3)2), 1.48 (m, CH2), 0.33 (s, Si(CH3)2). 13C
NMR (CDCl3, d): 56.4 (NCH2), 44.6 (N(CH3)2), 42.9 (CH2), 26.4 (CH2),
1.3 (Si(CH3)2). 29Si NMR (CDCl3, d): 12.4. Anal. Calcd for C12H30ClN3Si
(279.9): C, 51.49; H, 10.80. Found: C, 50.52; H, 11.19.
CH3ClHSiN[(CH2)3N(CH3)2]2. 1H NMR (CD3CN, d): 4.35 (q, SiH),
2.92 (m, CH2), 2.45 (m, CH2), 2.20 (s, N(CH3)2), 1.56 (m, CH2), 0.43 (d,
SiCH3). 13C NMR (CD3CN, d): 58.2 (NCH2), 47.8 (NCH2), 45.5 (N(CH3)2),
26.1 (CH2), ꢀ2.1 (SiCH3). 29Si NMR (CDCl3, d): ꢀ32.6 (1J(29Si-1H) = 278.3
Hz). Anal. Calcd for C11H28ClN3Si (265.9): C, 49.69; H, 10.61. Found: C,
49.34; H, 10.94.
C6H5HSi{N[(CH2)3N(CH3)2]2}2. 1H NMR (CDCl3, d): 7.70–7.20
(m, C6H5), 4.90 (s, SiH), 2.95 (m, CH2), 2.20 (m, CH2), 2.20 (s, N(CH3)2),
1.70 (m, CH2). 13C NMR (CDCl3, d): 136.3, 134.0, 128.8, 127.2 (C6H5),
57.2 (CH2), 45.0 (N(CH3)2), 43.9 (CH2), 27.4 (CH2). 29Si NMR (CDCl3,
d): ꢀ17.6. Anal. Calcd for C26H54N6Si (478.8): C, 65.22; H, 11.37. Found:
C, 64.89; H, 10.93.

1830
Harle et al.
CH3ClHSiN[(CH2)4CH3]2. 1H NMR (CD3CN, d): d 4.35 (q, SiH),
2.92 (m, CH2), 2.45 (m, CH2), 2.20 (s, N(CH3)2), 1.56 (m, CH2), 0.37 (d,
SiCH3). 13C NMR (CD3CN, d): 58.2 (CH2), 47.8 (CH2), 45.5 (N(CH3)2),
26.1 (CH2), ꢀ2.1 (SiCH3). 29Si NMR (CD3CN, d): ꢀ4.2. Anal. Calcd for
C11H26ClNSi (235.9): C, 56.01; H, 11.11. Found: C, 55.56; H, 11.23.
(CH3)2SiClN[(CH2)4CH3]2. 1H NMR (CDCl3, d): 2.75 (m, CH2),
2.08 (m, CH2), 2.08 (s, N(CH3)2), 1.48 (m, CH2), 0.33 (s, Si(CH3)2). 13C
NMR (CDCl3, d): 56.3 (NCH2), 44.6 (N(CH3)2), 42.9 (CH2), 26.4 (CH2),
1.3 (Si(CH3)2). 29Si NMR (CDCl3, d): 11.7. Anal. Calcd. for C12H28ClNSi
(249.9): C, 57.68; H, 11.29. Found: C, 57.13; H, 11.41.
(CH3)2HSiN[(CH2)4CH3]2. 1H NMR (CDCl3, d): 4.65 (septet, SiH,
3J(1H-1H) = 6.1 Hz), 3.02–1.00 (m, CH2 and CH3), 0.27 (d, Si(CH3)2,
3J(1H-1H) = 4.9 Hz). 13C NMR (CDCl3, d): 47.2 (NCH2), 29.5 (CH2), 29.2
(CH2), 22.5 (CH2), 13.8 (CH3), ꢀ1.7 (Si(CH3)2). 29Si NMR (CDCl3, d):
ꢀ7.0 (1J(29Si-1H) = 192.9 Hz). Anal. Calcd for C12H29NSi (215.4): C,
66.91; H, 13.57. Found: C, 66.89; H, 13.11.
C6H5Si{N[(CH2)2OCH3]2}2B[3,5-(CF3)2C6H3]4. 1H NMR (CDCl3,
d): 8.05–7.00 (m, C6H5 and C6H3), 3.75 (m, OCH2), 3.62 (s, OCH3), 3.20
(m, NCH2). 13C NMR (CDCl3, d): 161.8 (four resonances, 1J(11B-13C) = 49.8
Hz, B-C1), 134.9 (br s, B-C2,6), 129.1 (q, 2J(19F-13C) = 31.6 Hz, B-C3,5), 124.7
(q, 1J(19F-13C) = 272.3 Hz, CF3), 117.5 (br septet, B–C4), 67.6 (OCH2), 58.8
(OCH3), 47.6 (NCH2), four Si–C6H5 carbon resonances, undetected. Anal.
Calcd for C50H45BF24N2O4Si (1232.8): C, 48.72; H, 3.68; N, 2.27. Found: C,
48.67; H, 3.57; N, 1.92; ash, 1.72.
(CH3)2ClGeN[(CH2)2OCH3]2. 1H NMR (CDCl3, d): 3.62 (m, OCH2),
3.50 (s, OCH3), 3.13 (m, CH2), 0.83 (s, Ge(CH3)2). 13C NMR (CDCl3, d):
71.8 (OCH2), 58.1 (OCH3), 48.4 (CH2), 3.6 (Ge(CH3)2). Anal. Calcd for
C8H20ClGeNO2 (270.3): C, 35.55; H, 7.46. Found: C, 35.74 ; H, 8.53.
(C6H5)2ClGeN[(CH2)2OCH3]2. 1H NMR (CDCl3, d): 8.22–7.57 (m,
C6H5), 3.89 (m, OCH2), 3.20 (m, CH2), 3.14 (s, OCH3). 13C NMR (CDCl3, d):
133.9, 133.5, 130.2, 128.1 (C6H5), 72.0 (OCH2), 58.0 (OCH3), 48.1 (CH2).
Anal. Calcd for C18H24ClGeNO2 (394.4): C, 54.82; H, 6.13. Found: C, 54.17;
H, 6.58.
(CH3)2ClGeN[(CH2)3N(CH3)2]2. 1H NMR (CDCl3, d): 3.07 (m,
NCH2), 2.22 (m, CH2), 2.22 (s, N(CH3)2), 1.70 (m, CH2), 0.74 (s, Ge(CH3)2).
13C NMR (CDCl3, d): 56.7 (NCH2), 45.7 (NCH2), 44.9 (N(CH3)2), 27.2

Organosilanes and Organogermanes
1831
(CH2), 3.1 (Ge(CH3)2). Anal. Calcd for C12H30ClGeN3 (324.4): C, 44.43; H,
9.32. Found: C, 43.61; H, 9.40.
(C6H5)2ClGeN[(CH2)3N(CH3)2]2. 1H NMR (CDCl3, d): 7.95–7.29
(m, C6H5), 3.17 (m, NCH2), 2.20 (m, CH2), 2.20 (s, N(CH3)2), 1.80 (m,
CH2). 13C NMR (CDCl3, d): 133.6, 133.0, 129.8, 127.9 (C6H5), 56.6
(NCH2), 45.6 (CH2), 44.6 (N(CH3)2), 27.0 (CH2). Anal. Calcd for C22H34
ClGeN3 (448.6): C, 58.91; 7.64 H. Found: C, 58.34; H, 8.32.
Cl2Sn{N[(CH2)3N(CH3)2]2}2. 1H NMR (CD2Cl2, d): 2.53 (m, NCH2),
2.21 (m, CH2), 2.09 (s, N(CH3)2), 1.54 (m, CH2). 13C NMR (CD2Cl2, d):
58.4 (NCH2), 48.7 (CH2), 45.7 (N(CH3)2), 28.3 (CH2). Anal. Calcd for
C20H48Cl2N6Sn (562.2): C, 42.73; 8.60 H. Found: C, 41.66; H, 6.87.
RESULTS AND DISCUSSION
The compounds, in general, were isolated as high-boiling viscous oils
which were not further purified because the very high boiling points
precluded effective distillation even at reduced pressures.[1] Purity was
estimated to equal or exceed 95%, as judged by the absence of spurious
1
signals in the H, 13C and 29Si NMR spectra, and by elemental analyses.
Yields ranged between 50–75% for reactions conducted in diethyl ether
and THF. Silyl- and germylamines were available according to the gene-
ralized procedure outlined earlier and illustrated by the reaction of Eq. 1.
2 HN½ðCH2Þ2OCH3Š2 þ ðCH3Þ2SiCl2 þ 2ðC2H5Þ3N
! ðCH3Þ2SifN½ðCH2Þ2OCH3Š2g2 þ 2ðC2H5Þ3NHCl
ð1Þ
Tin amines, in general, are not amenable to this synthetic approach owing
to basicity considerations. The one stannylamine part of this investigation
was secured through a standard in situ route involving lithioamination of
the appropriate amine followed by treatment with, in this case, tin(IV)
chloride (Eqs. 2 and 3).
2 HN½ðCH2Þ3NðCH3Þ2Š2 þ 2 n ꢀ C4H9Li
! 2LiN½ðCH2Þ3NðCH3Þ2Š2 þ 2 n ꢀ C4H10
ð2Þ
ð3Þ
2 LiN½ðCH2Þ3NðCH3Þ2Š2 þ SnCl4
! 2 Cl2SnfN½ðCH2Þ3NðCH3Þ2Š2g2 þ 2 LiCl

1832
Harle et al.
The proton, carbon-13, and silicon-29 NMR shifts for the N(CH3)2 or
OCH3 groups of all compounds are summarized in Table 1.
Table 1 shows that both proton and carbon-13 shifts are essentially
identical for all of the compounds. They are also identical to the shifts of
the N(CH3)2 and OCH3 groups of the starting amines: 2.15 (1H), 44.3 (13C)
and 3.26 (1H) and 58.7 (13C), respectively. The 29Si shifts can be compared
to the shifts of the bis(pentyl)amino derivatives: (CH3)2ClSiN[(CH2)4CH3]2,
11.7 ppm; (CH3)2HSiN[(CH2)4CH3]2, ꢀ7.0 ppm.[10] The shifts of the N(CH3)2
and OCH3 derivatives are very similar to those of these noncoordinating
pentyl derivatives. The shifts at temperatures down to ꢀ90 °C in CD2Cl2
were very similar to those reported in the table at room temperature. There
were also no indications in the low-temperature spectra of broadening or
additional peaks due to the slowing of some fluxional process. We
conclude, therefore, that for all compounds studied, including those with
low steric hindrance such as the (CH3)2HSi group, those with electroneg-
ative groups such as one chlorine (e.g., CH3ClH); and a dichlorostannyl
group containing two electronegative groups and a more strongly Lewis
acidic central atom, that the terminal N(CH3)2 and OCH3 groups do not
coordinate to the central atom. We have previously attributed the difference
between the lack of coordination of our system and the many systems
studied by others[2–6] to the greater conformational flexibility of our purely
aliphatic chains. The greater decrease in entropy that results from co-
ordination in our system is perhaps sufficient to prevent the observation of
Table 1. XCH3 H, 13C, and 29Si NMR chemical shifts.a
1
R3SiN[(CH2)nX]2
R
X = N(CH3)2, n = 3
X = OCH3, n = 2
1H
13C
29Si
1H
13C
29Si
(CH3)2H
(CH3)2Cl
CH3ClH
2.12
2.08
2.20
44.9
44.6
45.5
ꢀ6.5
12.4
3.50
3.40
58.3
58.0
14.1
ꢀ2.7
ꢀ32.6
R2Si[N((CH2)nX)2]2
(CH3)2
C6H5H
3.40
3.45
3.45
57.7
58.0
58.2
ꢀ2.0
ꢀ16.4
ꢀ16.9
2.20
45.0
ꢀ17.6
C6H5Cl
R3GeN[(CH2)nX]2
(CH3)2Cl
(C6H5)2Cl
2.22
2.20
2.19
44.9
44.6
3.50
3.14
58.1
58.0
Cl2Sn[N((CH2)3X)2]2
aRelative to TMS in ca. 30% (v/v or w/v) solutions in CD2Cl2, CDCl3, or CD3CN.

Organosilanes and Organogermanes
1833
coordinational isomers even at low temperatures. On the other hand, we
were surprised to find that these potentially bidentate systems do not co-
ordinate even to the (CH3)2ClGe and Cl2Sn sites.
The product C6H5Si{N[(CH2)2OCH3]2}2B[3,5-(CF3)2C6H3]4, obtained
from C6H5HSi{N[(CH2)2OCH3]2}2, should contain a silylium ion. Because
this product is an oil that has resisted all of our attempts at recrystallization (as
is true for many other derivatives not reported here), X-ray conformation of
the structure is not possible. Moreover, repeated attempts to obtain 29Si data
using varying pulse delays, many pulses, addition of relaxation reagents,
variable temperature, varied solvents, and addition of benzoyl peroxide as a
radical scavenger have been unsuccessful. Indeed, the resonance of the
carbon atom directly attached to silicon in this compound has also not been
observed. We tentatively attribute the difficulty in obtaining both resonances
to the presence of a small amount of the silyl radical.
ACKNOWLEDGMENTS
We are indebted to the donors of the Petroleum Research Fund,
administered by the American Chemical Society, and to Dow Corning
Corporation, for partial support of this research. We also thank the Franklin
and Marshall College Hackman program and the Elizabethtown College
Faculty Grants Committee for summer stipends. The National Science
Foundation, Armstrong World Industries, and Franklin and Marshall
College assisted in acquiring a Varian UNITY 300-MHz NMR spectrometer
and support facilities.
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Received October 19, 2002
Accepted July 11, 2003
Referee I: C. L. Kepler
Referee II: K. Moedritzer