Synthesis and deprotonation of (phenylselenolatodimethylsilyl) bis(trimethylsilyl) methane: The crystal structure of (Me3Si) 2(Me2SiBr)CH

Article abstract of DOI:10.1016/j.molstruc.2012.03.004

The moisture-sensitive compound [{bromodimethylsilyl}bis(trimethylsilyl) methane], [(Me₃Si)₂(Me₂SiBr)CH] 1 has been synthesized by the bromination of the hydride [(Me₃Si) ₂(Me₂SiH)CH] in CC

Full text of DOI:10.1016/j.molstruc.2012.03.004

Journal of Molecular Structure 1018 (2012) 137–144
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Synthesis and deprotonation of (phenylselenolatodimethylsilyl)bis(trimethylsilyl)
methane: The crystal structure of (Me3Si)2(Me2SiBr)CH
a
b
Sushil K. Gupta a, , Sujata Yumnam , Peter B. Hitchcock
⇑
a School of Studies in Chemistry, Jiwaji University, Gwalior 474 011, India
b Department of Chemistry, School of Life Sciences, University of Sussex, Brighton BN 1 9QJ, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
The moisture-sensitive compound [{bromodimethylsilyl}bis(trimethylsilyl)methane], [(Me3Si)2(Me2-
SiBr)CH] 1 has been synthesized by the bromination of the hydride [(Me3Si)2(Me2SiH)CH] in CCl4 in good
yield. Compound 1 has been characterized by multinuclear NMR and a single crystal X-ray diffraction
studies. The average Si–C and BrMe2Si–C distances are, respectively, 1.894(2) and 1.886(2) Å. The Si–
C–Si angle is 114.98(13)°. Treatment of 1 with NaSePh (obtained from the sodium triethylborohydride
reduction of diphenyldiselenide) in benzene at room temperature resulted in the isolation of light yellow
oil, [{phenylselenatodimethylsilyl}bis(trimethylsilyl)methane], [(Me3Si)2(Me2SiSePh)CH] 2. Compound 2
has been metallated with methyllithium as well as lithium diisopropylamide (LDA) in THF to give
[(Me3Si)2(Me2SiSePh)CLiꢀ2THF] 3. Compounds 2 and 3 have been characterized by elemental analysis,
mass and multinuclear NMR studies.
Received 6 January 2012
Received in revised form 1 March 2012
Accepted 3 March 2012
Available online 21 March 2012
Dedicated to Professor Colin Eaborn, FRS,
who passed away on 22 February 2004
Keywords:
Synthesis
Bromodimethylsilylbis(trimethylsilyl)-
methane
Ó 2012 Elsevier B.V. All rights reserved.
Bulky selenium containing silicon ligand
Lithium derivative
NMR spectra
X-ray structure
1. Introduction
the metal through both the central carbanionic site and the lone
pairs of the group X, has been isolated. These compounds adopt a
There is considerable interest in the structures of simple com-
pounds in which two or three bulky groups are attached to a central
carbon atom, as for example, in (Me3C)2CH2 [1], (Me3C)3CH [2],
(Me3Si)2CH2 [3], (Me3Si)3CH [4,5], (Me3Si)3CBr [6], (Me2SiOMe)3CBr
[7] and [(Me2SiBr)3CH], all of which were studied by electron dif-
fraction but [(Me2SiBr)3CH] by X-ray diffraction as well [8]. It there-
fore seemed to us appropriate to determine the structure of the
related species [(Me3Si)2(Me2SiBr)CH], which as a solid could be
studied by X-ray diffraction. A second aspect is that in recent years
we have witnessed an increasing interest in the chemistry of bulky
silyl-substituted ligands containing donor groups [9–11]. A series of
organometallic compounds of the general type MC(SiMe3)n
(SiMe2X)3–n (X = OMe, NMe2, or CH2PPh2, M = alkali metal or, for
X = NMe2, M = MgI), in which the organosilyl ligand is bound to
range of molecular or chain structures. For example, LiC(Si-
Me2CH2PPh2)3 is monomeric with strong M–C bond [12], MgIC(Si-
Me2NMe2)3 [13] also monomeric with no normal M–C bond,
[LiC(SiMe2OMe)3]2 a dimeric [14] whereas [LiC(SiMe2NMe2)3]1
[15] or [KC(SiMe2NMe ) ]
2 3 1 [16] are polymeric. We have previously
reported the synthesis of tris{(diphenylphosphino)dimethylsi-
lyl}methane, HC(SiMe2PPh2)3 [17–19] and its sodium and potas-
sium derivatives of the type, (Ph2PMe2Si)3CM, (M = Na or K), by
the metallation of tris{(diphenylphosphino)dimethylsilyl}methane
(Ph2PMe2Si)3CH, with MeM (M = Na or K) in THF or Et2O. The
lithium compound, [Li(tmen)2][C(SiMe2PPh2)3](tmen = N,N,N0,
N0-tetramethylethane-1,2-diamine) has been shown to crystal-
lize in a lattice containing separated [Li(tmen)2] cations and
planar [C(SiMe2PPh2)3] carbanions [17,18]. However, few deriva-
tives of bulky silyl ligands containing chalcogen donors have
been isolated [20]. In the present study we report the synthesis,
structure and spectroscopic properties of [(Me3Si)2(Me2SiBr)CH]
(1), [(Me3Si)2 (Me2SiSePh)CH] (2) and its lithium derivative,
[(Me3Si)2(Me2SiSePh) CLiꢀ2THF] (3).
⇑
Corresponding author. Present address: Department of Chemistry, Howard
University, Washington, DC 20059, United States. Tel.: +91 751 2230867; fax: +91
751 2341450.
E-mail address: skggwr@gmail.com (S.K. Gupta).
0022-2860/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molstruc.2012.03.004

138
S.K. Gupta et al. / Journal of Molecular Structure 1018 (2012) 137–144
H
H
SePh
C
C
Me3Si
SiMe2Br
SiMe3
Si
SiMe3
Me3Si
Me2
1
2
SePh
Me3Si
_
C
SiMe2
[Li(THF)2]+
SiMe3
3
2. Experimental
2.1. General
Fig. 2. The molecular structure of the compound 1.
All reactions were conducted under an argon atmosphere and
compounds were manipulated on a double-manifold vacuum line
by the use of standard Schlenk techniques. Solvents were dried
and distilled over sodium-potassium alloy (benzene, heptane) or
sodium-benzophenone (Et2O, THF) and stored over a K or Na mirror
under argon. Microanalyses were carried out at Medac Ltd. (Brunel
University) as well as University of North London. The EI mass spec-
tra were recorded at 70 eV on a VG Autospec mass spectrometer.
The NMR spectra were recorded at ambient temperature in C6D6
at 300.1 (1H), 125.8 (13C), 99.4 (29Si) and 95.3 (77Se) MHz and cali-
brated internally to residual solvent resonances, (1H and 13C), exter-
nal SiMe4 or Me2Se. The quaternary carbon and 29Si signals were
detected by the INEPT (insensitive nuclei enhancement by polariza-
tion transfer) pulse technique. The compounds CHBr3, Me3SiCl,
[{(CH3)2CH}2NH] (diisopropylamine), MeLi (1.4 M solution in
diethyl ether) and BuLi (2.5 M solution in hexane) and Ph2Se2 were
purchased from Aldrich and used as received. The compounds (Me3-
Si)2CHBr, (Me3Si)2(Me2SiH)CH [21] and lithium diisopropylamide
(LDA) [22] were prepared as described in the literature.
[21] (16.70 g, 0.076 mol) in CCl4 (30 cm3) at 0 °C, and the resulting
orange solution was stirred at room temperature for 18 h. The sol-
vent was removed and the orange residue distilled (b.p. 54 °C/
10ꢁ3) to give a colorless oil that crystallized on standing, m.p.
42 °C. Yield: 16.7 g (75%). Anal. Calc. for C9H25BrSi3 (%): C, 36.34;
H, 8.47; Found: C, 36.65; H, 8.60. MS: m/z (%): 281(100%)
[M–Me]+, 217(88%) [M–Br]+, 203(15%) [M–Br–CH2]+, 129(75%)
[M–Br–CH2–H–SiMe3]+, 73(45%) [SiMe3], 59(14%) [SiMe2H],
45(7%) [SiMe2H–CH2]+. IR (Nujol, CsBr plates) (cm–1): 1251 m,
d(C–H); 1030 w; 845 vs, 730 w
q
(CH3)(Si); 670 w, mas (SiC); 610
vw, ms (SiC); 429 s,
m
(Si–Br). 1H NMR (300 MHz, C6D6): d – 0.37
(1H, s, CH), 0.15 (18H, s, SiMe3), 0.54 (6H, s, SiMe2). 13C{1H} NMR
(300 MHz, C6D6): d 8.2 (Si3C, 1J(13Cmethine–1H) 100.11 Hz), 3.16
(SiMe3, 1J(13Cmethyl–1H) 118.78 Hz), 7.82 (SiMe2), 1J (13Cmethyl–1H)
121.29 Hz). 29Si{1H} NMR (300 MHz, C6D6): d – 0.4 (SiMe3); 24.7
(SiMe2Br).
2.3. Preparation of [(Me3Si)2(Me2SiSePh)CH] (2)
2.2. Preparation of [(Me3Si)2(Me2SiBr)CH] 1
Diphenyl diselenide (1.56 g, 4.9 mmol) was dissolved in diethyl
ether (60 cm3), and sodium triethylborohydride (10 cm3 of a 1.0 M
solution in THF, 10 mmol) was added by syringe. The yellow solu-
tion color disappeared within seconds. The colorless solution was
A solution of Br2 (12.15 g, 0.076 mol in CCl4 (50 cm3)) was
added dropwise during 1 h to a solution of [HC(SiMe3)2(SiMe2H)]
1J(13Cmethine – 1H) 100.11 Hz
1J(13Cmethyl – 1H) 118.78 Hz
1J(13Cmethyl – 1H) 121.29 Hz
Fig. 1. 13C (proton coupled) NMR Spectrum of [(Me3Si)2(Me2SiBr)CH] (1).

S.K. Gupta et al. / Journal of Molecular Structure 1018 (2012) 137–144
139
1J CH (Si3CH) 101.3 Hz
1J CH (SiMe3) 118.72 Hz
1J CH (SiMe2) 120.96 Hz
Fig. 3. 13C NMR (proton coupled) spectrum of [(Me3Si)2(Me2SiSePh)CH] 2.
stirred for 30 min and taken to dryness to give a white solid [23]. To
the benzene suspension of NaSePh (1.32 g, 7.40 mmol) was added
dropwise through a cannula a benzene solution of [(SiMe3)2(Si-
Me2Br)CH] (2.0 g, 6.75 mmol) and the mixture was stirred over-
night. The solvent was removed completely in an external trap
and the residue extracted with hexane. The solution was filtered
to remove NaBr and the solvent stripped off under reduced pressure
to give a light yellow oil. Yield: 3.3 g (80%). Anal. Calc. for
J(HH) 8 Hz). 13C{1H} NMR (300 MHz): d 3.5 (SiMe3), 4.9 (SiMe2),
5.6 (CH), 126.83 (p-C), 127.5 (m-C), 129.0 (o-C), 137.4 (i-C).
29Si{1H} NMR (300 MHz, C6D6):
– 0.3 (SiMe3), 13.7 (SiMe2),
1J(29Si77Se) 108.4 Hz. 77Se {1H} NMR (300 MHz, C6D6): 112.3 (SePh).
2.4. Synthesis of (Me3Si)2(Me2SiSePh)CLiꢀ2THF (3)
2.4.1. Method A
A solution of LiNPri2 (lithium diisopropylamide, LDA) was cooled
to ꢁ78 °C and the compound [(Me3Si)2(Me2SiSePh)CH] (0.9 g,
3.35 mmol) added slowly. The mixture was stirred for 1 h at –
78 °C, then brought to room temperature and the solvent was
pumped away to leave a pale yellow sticky residue which was ex-
tracted with hexane. Removal of solvent from the extract gave a
yellow solid. Yield: 0.8 g (90%), m.p. 103 °C.
C
15H30Si3Se(%): C, 48.22; H, 8.09; Found: C, 48.01; H, 7.84. MS: m/
z
(%): 374(10%) [M]+, 359(50%) [M–Me]+, 282(20%) [M–
Me–Ph]+, 217(85%) [M–SePh]+, 201(15%) [M–SePh–CH4]+, 187(7%)
[M–SePh–CH4–CH2]+, 129(100%) [M–SePh–CH4–CH2–SiMe2]+,
73(75%) [SiMe3], 59(20%) [SiMe2H], 45(10%) [SiMe2H–CH2]. 1H
NMR (300 MHz, C6D6): d ꢁ0.38 (1H, s, CH), 0.19 (18H, s SiMe3),
0.38 (6H, s, SiMe2), 7.57 (2H, d, Ph, J(HH) 8 Hz), 6.95 (3H, d, Ph,
1J(29Si77Se) 108.4 Hz
Fig. 4. 29Si{1H} NMR spectrum with 77Se satellites of [(Me3Si)2(Me2SiSePh)CH] 2.

140
S.K. Gupta et al. / Journal of Molecular Structure 1018 (2012) 137–144
moved to leave a sticky pale yellow solid which was extracted into
hexane (20 cm3). The filtered extract was reduced to 5 cm3 and
kept at ꢁ20 °C to give yellow crystals. Yield: 0.5 g (80%), m.p.
102 °C (dec.). Anal.Calcd. for C15H29Si3SeLiꢀ2C4H8O (%): C, 52.74;
H, 8.65; Found: C, 48.14; H, 7.74. 1H NMR (300 MHz, C6D6): d
0.21 (18H, s, SiMe3), 0.55 (6H, s, SiMe2), 1.40 (8H, m, THF), 3.61
(8H, m, THF), 7.15–8.03 (5H, m, Ph). 29Si{1H} NMR (300 MHz,
C6D6): ꢁ10.0 (SiMe3), ꢁ0.5 (SiMe2).
Table 1
Crystal data and structure refinement for compound 1.
Empirical formula
C9H25BrSi3
Formula weight
Temperature
Wavelength
Crystal system
Space group
Unit cell dimensions
297.47
173(2) K
0.71073 Å
Monoclinic
P21/c(No. 14)
a = 8.8476(4) Å
a = 90°
b = 14.8285(9) Å b = 104.038(3)
2.5. X-ray structure determination
c = 12.2137(5) Å
1554.5(1) Å3
4
c = 90°
Volume
Z
Density (calculated)
Absorption coefficient
F(000)
Crystal size
Theta range for data collection
Index ranges
Reflections collected
Independent reflections
Reflections with I > 2sigma(I)
Completeness to theta = 27.90°
Tmax. and Tmin.
Colorless crystals were obtained using vacuum sublimation at
65 °C. Crystallographic data for 1 were collected on a Nonius-Kap-
pa CCD diffractometer. Crystal data, data collection and refinement
parameters are summarized in Table 1. Absorption corrections
were applied using MULTISCAN. The structure was solved and
refined using SHELXL-97 [24] as incorporated in the program pack-
age WINGX. The non-hydrogen atoms were refined anisotropically
with hydrogen atoms in the riding mode. The ORTEP-3 programme
[25] was used to prepare the molecular drawings. Selected bond
lengths and angles for 1 are listed in Table 2.
1.27 Mg/m3
2.84 mmꢁ1
624
0.4 ꢂ 0.2 ꢂ 0.2 mm3
3.76–27.90°
ꢁ11 6 h 6 11, ꢁ19 6 k 6 12, ꢁ13 6 1 6 16
9035
3685 [R(int) = 0.050]
2994
99.2%
0.507 and 0.428
Full-matrix least-squares on F2
3685/1/121
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2sigma(I)]
R indices (all data)
Largest diff. peak and hole
1.066
3. Results and discussion
R1 = 0.044, wR2 = 0.097
R1 = 0.060, wR2 = 0.105
0.63 and ꢁ0.48 e Å3
3.1. Synthesis and properties of [(Me3Si)2(Me2SiBr)CH] (1)
The compound bromodimethylsilylbis(trimethylsilyl)methane,
[(Me3Si)2Me2–SiBr)CH] 1 has been synthesized by the bromination
of the hydride (Me3Si)2(Me2–SiH)CH (prepared from the literature
method [21]) in CCl4 in good yield (Scheme 1). The compound 1 is
readily isolated as colorless crystalline solid by removing the sol-
vent under reduced pressure. It is soluble in hydrocarbon solvents.
Elemental analysis agreed well with the above formulation.
The compound 1 is moisture-sensitive and is easily hydrolyzed.
Table 2
Selected bond lengths (Å) and angles (°) for 1.
Si(1)–C(2)
Si(1)–C(3)
Si(i)–C(1)
Si(1)–Br
Si(2)–C(6)
Si(2)–C(5)
Si(2)–C(1)
Si(2)–C(4)
Si(3)–C(7)
Si(3)–C(9)
Si(3)–C(1)
Si(3)–C(8)
1.863(3)
1.863(3)
1.869(2)
2.2426(8)
1.874(3)
1.874(3)
1.894(2)
2.001(2)
1.866(3)
1.881(3)
1.895(3)
2.0252(17)
3.1.1. Mass spectrum
The EI mass spectrum of 1 did not exhibit the molecular ion
peak at m/z 296 [M]+ but it showed a peak at m/z 281 (100%) due
to the loss of one CH3 from the molecular ion. The peak at m/z
217 corresponds to [M–Br]+. The isotopic pattern and intensity of
each of the peaks confirm the presence of one bromine. Other
important fragments which could be identified are m/z(%):
203(15%) [M–Br–CH2]+, 129(75%) [M–Br–CH2–H–SiMe3]+, 73(45%)
[SiMe3], 59(14%) [SiMe2H], 45(7%) [SiMe2H–CH2]+. Calculated and
observed isotopic patterns for C8H22BrSi3 [M–Me]+ are in good
agreement.
C(2)–Si(1)–C(3)
C(2)–Si(1)–C(1)
C(3)–Si(1)–C(1)
C(2)–Si(1)–Br
C(3)–Si(1)–Br
C(1)–Si(1)–Br
106.92(16)
113.06(13)
115.42(13)
106.67(10)
104.70(11)
109.40(8)
105.09(15)
110.64(12)
112.87(13)
109.61(12)
106.78(13)
111.57(10)
105.53(14)
109.76(12)
113.96(13)
110.36(11)
105.19(12)
111.78(9)
C(6)–SiC(2)–C(5)
C(6)–Si(2)–C(1)
C(5)–Si(2)–C(1)
C(6)–Si(2)–C(4)
C(5)–Si(2)–C(4)
C(1)–Si(2)–C(4)
C(7)–Si(3)–C(9)
C(7)–Si(3)–C(1)
C(9)–Si(3)–C(1)
C(7)–SiC3)–C(8)
C(9)–Si(3)–C(8)
C(1)–Si(3)–C(8)
Si(1)–C(1)–Si(2)
Si(1)–C(1)–Si(3)
SiC2)–C(1)–Si(3)
3.1.2. IR spectra
The IR spectrum of compound 1 shows medium intensity band
at 1251 cmꢁ1, assignable to bending methyl vibrations, d (CH3). The
bands at 1030, 845 and 730 cmꢁ1 are assigned to methyl-silicon
rocking modes (
q(CH3)(Si)). The silicon–carbon (tertiary) asym-
metric and symmetric stretching vibrations (
m
as(SiC) and s(SiC))
m
are observed at 670 and 610 cmꢁ1 respectively. The strong band
at 429 cmꢁ1 is assigned to Si–Br stretching vibrations. These
assignments are in good agreement with data from related bulky
silyl substituted compounds [26–28].
114.70(13)
115.68(12)
114.57(13)
2.4.2. Method B
3.1.3. 1H NMR
A solution of MeLi (1.6 mmol) in THF (15 cm3) was added at
room temperature to a stirred solution of [(Me3Si)2(Me2SiSePh)CH]
(0.59 g, 1.6 mmol) in THF (15 cm3). Gas was evolved immediately.
The resulting yellow solution was stirred for 4 h and the solvent re-
The 1H NMR spectrum of compound 1 recorded in C6D6 at
300 MHz showed signals at d – 0.37 assigned to the methine pro-
ton. Other peaks at d 0.15 and d 0.54 are assigned to the SiMe3
and SiMe2 protons respectively.

S.K. Gupta et al. / Journal of Molecular Structure 1018 (2012) 137–144
141
Fig. 5. 77Se{1H} NMR spectrum of [(Me3Si)2(Me2SiSePh)CH] 2.
3.1.4. 13C NMR
SiMe3
Br
The proton decoupled 13CNMR spectrum of compound 1 re-
corded in C6D6 solution at 300 MHz showed signals at d 8.2 for
the methine carbon. The signals at d 3.2 and 7.8 are assignable to
the SiMe3 and SiMe2 carbons respectively.
Br
Br
SiMe3
2 BuLi
SiMe3
Cl
2
+
oC
H
-
THF
78
H
/
Br
The spin–spin coupling of two magnetically active nuclei in
neighboring atoms is thought to occur by ‘knock-on’ couplings
from nucleus A to the near bonding electron 1 and from bonding
electron 2 to nucleus B. Obviously, the efficiency of this coupling
depends sharply on the probability of finding the bonding
electrons at the nuclei. In MO theory, this probability is non-zero
for s-type orbitals and their hybrids. Pure p-type orbitals, however,
have no amplitude at the nucleus. From this argument, it follows
that the coupling constant between a given pair of nuclei increases
with the s-character of the bond between atoms.
_
SiMe2H
Mg
+Cl
THF
+
SiMe3
SiMe3
SiMe3
SiMe3
Br
+
2
CCl4
H
H
SiMe2Br
SiMe2H
Scheme 1.
The C–H bonds in SiMe groups are expected to be fairly normal
sp3 bonds since they are very nearly tetrahedrally arranged, as
shown in numerous crystal structures. The magnitude of the cou-
pling constant indicates an appreciable s-character; in a perfect
sp3 orbital, it is 25%. The tertiary C–H bonds, on the other hand,
show lower coupling constants. To a first approximation, these
bonds also are sp3. The other three bonds in the system are C–Si
bonds, though, and these three seem to absorb most of the s-char-
acter, leaving a very p-like orbital for the C–H. The p-orbital on the
Et2O
Ph2Se2
NaEt3BH
NaSePh
2
+
SiMe3
SiMe3
SiMe3
SiMe3
C6H6
RT
SePh
Na
+
H
H
SiMe2Br
SiMe2SePh
carbon atom is well positioned to overlap with empty orbitals of
p
symmetry on the silicon atoms (I).
Scheme 2.
THF
[(CH3)2CH]2NH] CH3(CH2)3Li
[(CH3)2CH]2NLi]
LDA
+
o
-
78
C
(Me2CH)2NLi]
[(Me3Si)2(Me2SiSePh)CH]
+
THF
-780 C
THF
RT
[(Me3Si)2(Me2SiSePh)CLi.2THF]
3
MeLi
[(Me3Si)2(Me2SiSePh)CH]
+
Scheme 3.

142
S.K. Gupta et al. / Journal of Molecular Structure 1018 (2012) 137–144
and were refined with partial occupancies. Bond lengths involving
the disordered sites are unreliable.
The Si–C–Si bond angles are widened from the tetrahedral value
to an average of 114.98(13)°, not significantly different from that
observed in [CH(SiMe2Br)3] {mean 115.16(3)°} [8]. The mean
Si–C1 bond length to the central carbon {1.886(2) Å} is essentially
identical with that in [CH(SiMe2Br)3] {mean 1.884(5) Å}. The
BrMe2Si–C1 distance {1.869(2) Å} appears to be significantly short-
er than the Me3Si–C1 distance {1.894(2) Å}. The Si–Br bond length,
2.243(8) Å, is essentially similar to that, 2.256(2) Å, in [CH(Si-
Me2Br)3] but is significantly longer than those in BrnSiH4ꢁn and
MenSiBr4ꢁn (2.14–2.235 Å) [31,32] and 1-bromo-3,5,7-trimethyl-
1,3,5,7-tetrasilaadamantane (2.197 Å) [33]. Further it is a little
shorter than those [2.284(5), 2.283(1) Å] in two sterically encum-
bered polysilanes [34,35].
These effects could be at least partially steric in nature: the
SiMe3 groups, in repelling each other, will open the Si–C–Si bond
angle up. The resulting geometry may be the main factor imposing
the unusual hybridization of the central carbon. In organometallic
compounds of trisyl-like ligands, the p-orbital carries even more
electron density and so the s-character of the three Si–C bonds
goes up even further as the limiting case of an sp2 carbanion is
approached.
The flatter carbon is observed in all Si3CH compounds. The sum
of the three Si–C(1)–Si bonds are 345° whereas a similar total for a
normal tetrahedral center would be 327°. The C–Si–C–Si torsion
angles ca. ꢁ160°, 41° and 79° are similar to those in related com-
pounds [8].
The Newman projection of the compound 1 is shown below.
In the proton-coupled 13C spectrum (Fig. 1, II) various coupling
constants are measured as follows: 1J(13Cmethine–1H) 100.11 Hz,
1J(13Cmethyl –1H) for SiMe3 118.78 Hz and that of 1J(13Cmethyl –1H)
for SiMe2 121.29 Hz.
H
Me
Me
Si
H
C
H
Br
2
Me3Si
Si
(
)
H
C
SiMe3
Me3Si
H
Si
H
Br
C
(
)
H
H
3
Newman Projection
II
The analytical, spectral and crystal structure data suggest that
the bromodimethylsilylbis(trimethylsilyl)methane has the dis-
torted tetrahedral structure with the bromine atom away from
the central carbon atom and silicon atom retains their tetrahedral
configuration.
It is well known that the presence of electronegative groups in-
creases the magnitude of the chemical shifts and C–H coupling
constants [29]. In this case it can be seen that substituting the H
by Br in 1 increases the chemical shift from 1.9 to 8.2 for the
methine carbon, 2.4 to 3.2 for the SiMe3 carbon and ꢁ0.6 to 7.8
for the SiMe2 carbon. The coupling constants also increase in the
order: 1JCH (SiMe2) from 120.0 Hz to 121.29 Hz, while the 1JCH
(Si3C) increases from 98.0 Hz to 100.11 Hz. Although these in-
creases are only small, they nonetheless demonstrate the effect
of electronegative groups on the geometry of the central carbon.
3.2. Synthesis and properties of [(Me3Si)2(Me2SiSePh)CH] (2)
The compound [{phenylselenatodimethylsilyl}bis(trimethyl-
silyl)methane], [(Me3Si)2(Me2SiSePh)CH] 2 has been synthesized
by the reaction of sodium phenyl selenolate, NaSePh (obtained
from the triethylborohydride reduction of diphenyl diselenide,
Ph2Se2) with the bromide, [(SiMe3)2(SiMe2Br)CH] in benzene at
room temperature in good yield (Scheme 2). The compound 2 is
readily isolated as light yellow oil under reduced pressure. It is sol-
uble in hydrocarbon solvents. Elemental analysis agreed well with
the above formulation.
3.1.5. 29Si{1H} NMR
The proton-decoupled 29Si{1H} NMR spectrum of compound 1
recorded in C6D6 solution at 300 MHz showed resonance at d
ꢁ0.4 assigned to the SiMe3 silicon and d 24.7 for the SiMe2 silicon.
The SiMe3 silicon signal is at lower frequency than that of the hy-
dride (d 0.3) whereas the SiMe2 silicon signal is at higher frequency
than that in the hydride (d ꢁ15.6).
3.2.1. Mass spectrum
The EI mass spectrum of 2 exhibits the molecular ion peak at
m/z 374 [M]+. The peaks at m/z 359, 282 and 217 are due to the ra-
pid loss of CH3, Ph and SePh fragments respectively from the
molecular ion peak [M]+. The isotopic pattern and intensity of
the peaks confirm the presence of one selenium atom. Other
important fragments which could be identified are: MS: m/z(%):
201(15%) [M–SePh–CH4]+, 187(7%) [M–SePh–CH4–CH2]+, 129
(100%) [M–SePh–CH4–CH2–SiMe2]+, 73(75%) [SiMe3], 59(20%) [Si-
Me2H], 45(10%) [SiMe2H–CH2]. Calculated and observed isotopic
pattern for C15H30Si3Se (M+) are in good agreement.
The values of 0.1 ppm for the Si3CH carbon and 6.3 ppm for the
SiMe2Br silicon, given in a previous paper [30], are incorrect.
3.1.6. Crystal structure of (Me3Si)2(Me2SiBr)CH
An ORTEP view of the bromide 1 with the atom numbering
scheme is shown in Fig. 2. Crystallographic details are presented
in Table 1 and bond lengths and angles are given in Table 2. The
Br atom is disordered 78:9:13% over the three sides labeled Br,
C(4) and C(8). The overlapping Br/C atoms sited were not resolved

S.K. Gupta et al. / Journal of Molecular Structure 1018 (2012) 137–144
143
3.2.2. 1H NMR
deprotonation steps unambiguous, no lithium–halogen exchange
is possible in this case [22,37] (Scheme 3).
The 1H NMR spectrum of compound 2 recorded in C6D6 at
300 MHz shows singlet signals at d – 0.38, d 0.19 and d 0.38 assign-
able to the methine (CH), SiMe3 and SiMe2 protons respectively.
The ortho- and meta- and para-phenyl protons appear as doublets
at d 7.57 and d 6.95 respectively. The proton-proton coupling con-
stants (J 8 Hz) are in the usual range.
The lithiation has been completed within 2 h at room tempera-
ture in contrast with that of the related substrate (Me3Si)3CH
which requires 4–6 h in refluxing THF [38]. The compound has
been isolated as air- and moisture-sensitive pale yellow solid in
good yield. It is soluble in pentane, hexane, benzene, toluene and
THF. Carbon and hydrogen analyses are not satisfactory due to
air- and moisture-sensitivity of the compound.
3.2.3. 13C NMR
The proton decoupled 13C{1H} NMR spectrum of compound 2
recorded in C6D6 solution at 300 MHz shows signals at d 5.6 for
the methine carbon. The signals at d 3.5 and 4.9 are assignable to
the SiMe3 and SiMe2 carbons respectively. The chemical shift val-
ues of compound 2 are similar to the values obtained for 1 and
clearly indicate the replacement of bromide by weaker nucleophile
SePh. The ipso-phenyl carbon appears as strong downfield shift at
137.4. The ortho-, meta- and para-phenyl carbon appear in their
usual positions.
3.3.1. 1H NMR
The 1H NMR spectrum of lithium derivative shows peaks at d
0.21 and 0.55 assignable to SiMe3 and SiMe2 and at 3.6 and 1.4
for complexed THF. The integration of the peaks suggests that
there are two THF molecules coordinated to Li.
The absence of CH peak confirms the deprotonation. The ob-
served chemical shifts for SiMe3 and SiMe2 protons are downfield
compared to free ligand. The multiplets at 8.03 and 7.15 are as-
signed to phenyl protons.
In the proton-coupled 13C spectrum (Fig. 3, III) various coupling
constants are calculated as follows: 1J(13Cmethine–1H) 101.3 Hz,
1J(13Cmethyl–1H) for SiMe3 118.72 Hz and that of 1J(13Cmethyl–1H)
for SiMe2 120.96 Hz.
3.3.2. 29Si{1H} NMR
The 29Si {1H} NMR spectrum shows two peaks at d ꢁ10.0 and
ꢁ0.5 ppm which are assigned to SiMe3 and SiMe2 silicon signals.
The observed chemical shifts were shifted upfield to those in 2.
Similar ionic structures for lithium derivative have been reported
earlier [17–19].
H
SePh
C
H
Me3Si
Si
(
)
H
2
C
H
4. Conclusion
Si
H
C
The present study involves synthesis and structure of bromo-
dimethylsilylbis(trimethylsilyl)methane, (Me3Si)2(Me2SiBr)CH, 1.
The bromide has been successfully converted into a bulky ligand,
(Me3Si)2(Me2SiSePh)CH, 2 with a potential selenium donor func-
tion. Compound 2 has been metallated with LDA as well as with
MeLi. The NMR spectra closely resemble those of the previously
characterized lithium derivatives, suggesting that (Me3Si)2(Me2-
SiBr)CLiꢀ2THF, 3, exists as ion pairs in solution.
(
)
H
H
3
III
These coupling constants differ significantly from those of 1.
3.2.4. 29Si{1H} NMR
Investigations on the potential of 2 and 3 as ligand transfer re-
agents towards transition metal ions are in progress and will be re-
ported later.
The proton-decoupled 29Si{1H}NMR spectrum of compound 2
(Fig. 4) recorded in C6D6 solution at 300 MHz shows resonances
at d – 0.3 assigned to the SiMe3 silicon and d 13.7 for the SiMe2 sil-
icon. There is a marked change in the chemical shift of SiMe2 signal
in compound 2 relative to compound 1. The SiMe2 silicon reso-
nance in compound 2 is associated with 77Se satellites (intensities
1:6:1, Fig. 4). The coupling constant 1J(29Si77Se) 108.4 Hz is in good
agreement with the reported values for other related compounds
[36].
Supplementary material
CCDC 861028 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cam-
bridge Crystallographic Data Centre (CCDC), 12 Union Road, Cam-
bridge CB2 1EZ, UK (Fax: +44 1223 336033).
3.2.5. 77Se{1H} NMR
The 77Se{1H} NMR of compound 2 (Fig. 5) shows a single reso-
nance at d 112.3 ppm. The observed chemical shift is in good agree-
ment with related selenium compounds [36]. The chemical shift of
diphenyl diselenide is at d 459.7 ppm. This indicates that the ob-
served compound is free from diselenide impurity.
The analytical and multinuclear NMR data suggest that the phe-
nylselenolatodimethylsilylbis(trimethylsilyl)methane has the dis-
torted tetrahedral structure with the SePh group away from the
central carbon atom and silicon atom retains their tetrahedral
configuration.
Acknowledgements
We are grateful to the University Grants Commission, New Del-
hi for financial assistance (No. F.12-132/2001(SR-I) and for the
award of a Research Fellowship to S.Y. We acknowledge the help
of Dr. A. Abdul-Sada and Dr. A.G. Avent in recording mass and
NMR spectra, respectively, Dr. J.D. Smith for useful discussion
and referees for constructive comments.
References
3.3. Synthesis and properties of [(Me3Si)2(Me2SiSePh)CLiꢀ2THF] (3)
[1] L.S. Bartell, W.F. Bradford, J. Mol. Struct. 37 (1977) 113.
[2] H.B. Burgi, L.S. Bartell, J. Am. Chem. Soc. 94 (1972) 5236.
[3] T. Fjeldberg, R. Seip, M.F. Lappert, A.J. Thorne, J. Mol. Struct. 99 (1983) 295.
[4] B. Beagley, R.G. Pritchard, C. Eaborn, S.S. Washburne, Chem. Commun. (1981)
710.
The new bulky ligand [(Me3Si)2(Me2SiSePh)CH] has been metal-
lated with methyllithium as well as lithium diisopropylamide
(LDA) in THF. Using LDA instead of MeLi essentially makes the
[5] B. Beagley, R.G. Pritchard, J. Mol. Struct. 84 (1982) 129.

144
S.K. Gupta et al. / Journal of Molecular Structure 1018 (2012) 137–144
[6] P.T. Brain, M. Mehta, D.W.H. Rankin, H.E. Robertson, C. Eaborn, J.D. Smith, A.D.
[22] K. Yoon, D.Y. Son, J. Organomet. Chem. 545 (1997) 185.
[23] J. Lee, M. Brewer, M. Berardini, J.G. Brennan, Inorg. Chem. 34 (1995) 3215.
[24] G.M. Sheldrick, SHLEX-97, ‘‘Programme for solution and refinement of crystal
structures’’, University of Gottingen, Germany, 1997.
Webb, J. Chem. Soc., Dalton Trans. (1995) 349.
[7] P.T. Brain, M. Mehta, D.W.H. Rankin, H.E. Robertson, C. Eaborn, J.D. Smith, A.D.
Webb, J. Chem. Soc., Dalton Trans. (1995) 975.
[8] C.A. Morrison, D.W.H. Rankin, H.E. Robertson, C. Eaborn, A. Farook, P.B.
Hitchcock, J.D. Smith, J. Chem. Soc., Dalton Trans. (2000) 4321.
[9] C. Eaborn, J.D. Smith, J. Chem. Soc., Dalton Trans. (2001) 1541.
[10] C. Eaborn, J.D. Smith, Coord. Chem. Rev. 154 (1996) 125.
[11] C. Eaborn, K. Izod, J.D. Smith, J. Organomet. Chem. 500 (1995) 89.
[12] A.G. Avent, D. Bonafoux, C. Eaborn, M.S. Hill, P.B. Hitchcock, J.D. Smith, J. Chem.
Soc. Dalton Trans. (2000) 2183.
[13] C. Eaborn, F. Adam, P.B. Hitchcock, J.D. Smith, Organometallics 16 (1997) 503.
[14] F.I. Aighbirhio, N.H. Buttrus, C. Eaborn, S.H. Gupta, P.B. Hitchcock, J.D. Smith,
A.C. Sullivan, J. Chem. Soc., Dalton Trans. (1992) 1015.
[25] L.J. Farrugia, J. Appl. Cryst. 30 (1997) 565.
[26] W. Uhl, M. Pohlmann, R. Wartchow, Angew. Chem. Int. Ed. Engl. 37 (1998) 961.
[27] W. Uhl, S.U. Keimling, K.W. Klinkhammer, W. Schwarz, Angew Chem. Int. Ed.
Engl. 36 (1997) 64.
[28] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination
Compounds, fifth ed., Wiley, New York, 1997.
[29] C. Eaborn, P.B. Hitchcock, P.D. Lickiss, J. Organomet. Chem. 252 (1983) 281.
[30] S.S. Al-Juaid, C. Eaborn, P.B. Hitchcock, M.S. Hill, J.D. Smith, Organometallics 19
(2000) 3224.
[31] E. Lukevics, O. Pudova, R. Sturkovich, Molecular Structure of Organosilicon
Compounds, Ellis Horwood, Chichester, 1989. p. 235.
[15] F. Adam, C. Eaborn, P.B. Hitchcock, J.D. Smith, Chem. Commun. (1996) 741.
[16] S.S. Al- Juaid, C. Eaborn, S. El- Hamruni, A. Farook, P.B. Hitchcock, J.D. Smith, M.
Hopman, W. Clegg, K. Izod, P. O’Shaughnessy, J. Chem. Soc., Dalton Trans.
(1999) 3267.
[32] H.W. Mitzel, J. Riede, H. Schmidbaur, Acta Crystallogr. Sect. C 52 (1996) 980.
[33] S.W. Gurkova, A.I. Gusev, V.A. Sharapov, T.K. Gar, H.V. Alexeev, J. Struct. Chem.
20 (1979) 302.
[17] A.G. Avent, D. Bonafoux, C. Eaborn, S.K. Gupta, P.B. Hitchcock, J.D. Smith, J.
Chem. Soc., Dalton Trans. (1999) 831.
[34] U. Schubert, C. Steib, J. Organomet. Chem. 238 (1982) C1.
[35] N. Wiberg, C.M.M. Finger, H. Auer, K. Polborn, J. Organomet. Chem. 521 (1996)
377.
[36] H. Duddeck, Nucl. Magn. Reson. Spectrosc. 1 (1995) 27.
[37] E.J. Hawrelak, F.T. Ladipo, Organometallics 18 (1999) (1804).
[38] A.G. Avent, C. Eaborn, P.B. Hitchcock, G.A. Lawless, P.D. Lickiss, M. Mallien, J.D.
Smith, A.D. Webb, B. Wrackmeyer, J. Chem. Soc., Dalton Trans. (1993) 3259.
[18] S.K. Gupta, C. Eaborn, P.B. Hitchcock, J.D. Smith, in: R. Bohra (Ed.), Advances in
Metallo-Organic Chemistry, RBSA Publishers, Jaipur, 1999, p. 267.
[19] S.K. Gupta, A. Kelkar, Main Group Chemistry 4 (2005) 201.
[20] D.A. Antonov, C. Eaborn, J.D. Smith, P.B. Hitchcock, E. Molla, V.I. Rozenberg,
W.A. Stanczyk, A. Kowalewska, J. Organomet. Chem. 521 (1996) 109.
[21] D. Seyferth, H. Lang, Organometallics 10 (1991) 551.