Experimental and theoretical studies on formal σ-bond metathesis of silyl tellurides with alkyl halides

Article abstract of DOI:10.1016/j.jorganchem.2006.05.066

Silyl tellurides reacted with alkyl halides under mild thermal conditions to give the corresponding alkyl tellurides and silylhalides in good to excellent yields. Substitution took place much faster in polar solvents, such as acetonitrile, than that in no

Full text of DOI:10.1016/j.jorganchem.2006.05.066

Journal of Organometallic Chemistry 692 (2007) 664–670
www.elsevier.com/locate/jorganchem
Experimental and theoretical studies on formal r-bond metathesis
of silyl tellurides with alkyl halides
a,
b
b
Shigeru Yamago *, Kazunori Iida , Jun-ichi Yoshida
a
Division of Molecular Materials Science, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka 558-8585, Japan
Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
b
Received 1 April 2006; received in revised form 21 May 2006; accepted 30 May 2006
Available online 5 September 2006
Abstract
Silyl tellurides reacted with alkyl halides under mild thermal conditions to give the corresponding alkyl tellurides and silyl halides in
good to excellent yields. Substitution took place much faster in polar solvents, such as acetonitrile, than that in non-polar solvents. After
removal of the volatile silyl halides and solvent under vacuum, the essentially pure divalent organotellurium compounds were obtained.
Theoretical calculations were performed to understand the reaction mechanism, and a stepwise pathway involving tetravalent organo-
tellurium intermediate was obtained. Since the intermediate as well as the rate-determining step leading to the intermediate from the reac-
tants possess highly polar character, they would be stabilized in polar solvents.
Ó 2006 Elsevier B.V. All rights reserved.
Keywords: Silyl tellurides; Organotellurium compounds; Theoretical study; Hypervalent compounds; Ligand coupling; r-Bond metathesis
1. Introduction
as we know, only a few examples have been reported so far
on the similar formal r-bond metathesis of organochalco-
gen compounds which proceeds under mild thermal condi-
tions. Ogura and coworkers reported that thermal reaction
of alkyl phenyl tellurides with halogens to give alkyl halides
and phenyl tellanyl halides [5]. We also reported the reac-
tion of sugar-derived divalent selenides and tellurides with
bromine produce alkyl bromide and corresponding selenyl-
and tellanyl-bromide, respectively [6]. These unique reac-
tivities of organochalcogenides compounds prompted us
to investigate the reaction of silyl tellurides and alkyl
halides in detail. Preliminary results have already been
reported [7], and we report here the full details of the stud-
ies including the theoretical calculations.
While silyl sulfides and silyl selenides have proved to be
valuable synthetic reagents [1], a little is known for the syn-
thetic use of silyl tellurides [2]. We have recently disclosed
trimethylsilyl phenyl telluride (1) and triethoxysilyl phenyl
telluride promote radical coupling reaction of carbonyl
compounds or imines with isonitriles and alkynes [3]. We
also found that 1 undergoes reductive bis-silylation of qui-
nones [4]. During the course to investigate the new reactiv-
ity of silyl tellurides, we found that they react with alkyl
halides in polar solvents to give alkyl phenyl tellurides
and silyl halides (Scheme 1).
Since two r-bonds, namely carbon–halogen bond in
alkyl halides and silicon–tellurium bond in silyl tellurides,
were substituted for new two r-bonds, namely carbon–tel-
lurium bond and silicon–halogen bond, this reaction can be
looked upon as a formal r-bond metathesis reaction. As far
2. Results and discussion
2.1. Synthesis of divalent organotellurium compounds using
group 14-metaltellurides
*
Corresponding author. Present address: Institute for Chemical
Effects of substituents on the silicon atom in silyl tellu-
rides have been firstly examined. The reaction of trimethyl-
Research, Kyoto University, Uji, Kyoto 611-0011, Japan.
E-mail address: yamago@scl.kyoto-u.ac.jp (S. Yamago).
0022-328X/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.05.066

S. Yamago et al. / Journal of Organometallic Chemistry 692 (2007) 664–670
665
Table 2
R' TePh
+
X SiR3
R3Si TePh
1: R = Me
+
R'
X
MeCN
Reaction of 1 with 1-decylhalidesa
rt - 60 oC
Run n-Decylhalide Solvent
Temperature Time Yield
(°C)
(h)
(%)
Scheme 1. Reaction of silyl tellurides with alkyl halides.
1
2
3
4
5
6
7
8
9
n-C10H21Br
Acetonitrile
Acetonitrile
Pyridine
DMF
Ionic liquidc 60
THF
Toluene
Hexane
Acetonitrile
Acetonitrile
r.t.
60
60
60
12
12
3
3
3
3
3
3
24
24
25
100 (84)b
silyl phenyl telluride (1, R = Me, 1.0 equiv.) and benzyl
bromide in acetonitrile-d3 was monitored by H NMR at
1
88
63
37
0
0
room temperature. The reaction completed within 1 h,
and the formation of benzyl phenyl telluride and trimethyl-
silyl bromide was observed by 1H NMR. After solvent and
trimethylsilyl bromide were removed under reduced pres-
sure, virtually pure benzyl phenyl telluride was obtained
in quantitative yield (Table 1, run 1). The reactions of t-
butyldimethylsilyl phenyl telluride, triethoxysilyl phenyl
telluride, and tris(trimethylsilyl)silyl phenyl telluride with
benzyl bromide were slow at room temperature, but benzyl
phenyl telluride was eventually formed in moderate to
good yields after 24 h at room temperature (runs 2–4).
Low reactivity of these silyl tellurides compared to 1 might
be attributed to the steric bulkiness and/or electronic effects
of substituents on the silicon atom. We also examined the
reaction of trimethylgermyl phenyl telluride and trimethyl-
stannyl phenyl telluride. While the both reagents showed
lower reactivity than 1, benzyl phenyl telluride formed in
excellent yields after 24 h at room temperature (runs 5
and 6). We used 1 for the following studies due to its high
reactivity.
60
60
60
60
60
0
n-C10H21Cl
n-C10H21
87 (57)b
41 (23)b
10
a
I
Typical experimental procedures: a mixture of alkyl halide and 1
(1.0 equiv.) in acetonitrile was stirred at 60 °C. After removal of the vol-
atile materials under vacuum, the product was analyzed by 1H NMR.
b
Yield corresponding to the reaction at 60 °C for 3 h.
1-Butyl-3-methyl-1-imidazolium tetrafluoroborate was used.
c
The effects of leaving groups were also examined. We
surprisingly found that alkyl bromides were most reactive
followed by alkyl chlorides, and that alkyl iodides were
the least reactive. Thus, even though the reaction of n-decyl
chloride had not completed after 24 h at 60 °C, the desired
product formed in 87% yield (run 9). Conversely, only half
the amount of n-decyl iodide was converted to the product
under similar conditions (run 10).
The scope and efficiency of the present reaction are sum-
marized in Table 3. Benzyl halides are especially good sub-
strates, and several substituted benzyl chlorides reacted
with 1 to give the corresponding tellurides in quantitative
yields (runs 1–3). Substitution took place exclusively at
the sp3 carbon–chlorine bond over the sp2 carbon–chlorine
bond (runs 2 and 3). The secondary benzyl bromide also
afforded the desired product in good yield (run 4). Allyl
halides were equally good substrates, and gave the desired
products in excellent yields (runs 5–7). Primary alkyl bro-
mide and chloride were also quite reactive (runs 8 and 9).
1-Hexenyl-6-bromide did not give the cyclized product
(run 8), and this result suggests that a mechanism involving
free 1-hexenyl radical is unlikely [8]. Secondary alkyl bro-
mides were found to be moderately reactive (run 10), and
tertiary alkyl bromides resulted in low conversion (run
11). Aryl halides, such as phenyl bromide and iodide did
not react under similar conditions, whereas 2-pyridyl bro-
mide reacted to give the corresponding telluride in moderate
yield (run 12). This is probably because the strong directing
effect of the 2-pyridinyl group enhances the reactivity.
A synthetic advantage of the current method is the ease of
workup. Many of organotellurium compounds, in particu-
lar compounds having sp3-carbon tellurium bond, are
unstable under air or silica gel chromatography conditions,
and they are often used in the following step without purifi-
cation. As the side product formed in this reaction was the
volatile trimethylsilyl halides, the essentially pure products
could be easily obtained after removal of the silyl halides
and the solvent under vacuum. Therefore, the crude prod-
ucts could then be used for further synthetic transformations
The effects of solvent and leaving group were also inves-
tigated using 1 and n-decyl halides, and the results are sum-
marized in Table 2. The reaction of 1 with n-decyl bromide
in acetonitrile completed within 12 h at 60 °C to give n-
decyl phenyl telluride in quantitative yield (run 2). The for-
mation of trimethylsilyl bromide was also characterized by
1H NMR in the experiments carried out in acetonitrile-d3.
The progress of the reaction was found to be strongly influ-
enced by the polarity of the solvent. Thus, the reaction
took place efficiently in polar solvents, e.g., acetonitrile,
DMF, pyridine, and the ionic liquid (1-butyl-3-methyl-1-
imidazolium tetrafluoroborate), while no reaction occurred
in non-polar solvents, e.g., THF, toluene, and hexane
under similar conditions (runs 3–8). Acetonitrile was
selected as the solvent for the following investigations
due to its high volatility.
Table 1
Reaction of Group 14-metaltellurides with benzylbromide in acetonitrile-
a
d3
Run
Metaltelluride
Time (h)
Yield (%)b
1
2
3
4
5
6
a
Me3SiTePh (1)
t-BuMe2SiTePh
(EtO)3SiTePh
(Me3Si)3SiTePh
Me3GeTePh
1
24
24
24
24
24
100
82
77
45
88
91
Me3SnTePh
Typical experimental procedures: a mixture of benzylbromide and
metaltelluride (1.0 equiv.) in acetonitrile-d3 (ca. 0.5 M solution) was stir-
red at room temperature.
b
The yields were determined by 1H NMR of the crude mixture after
adding an internal standard.

666
S. Yamago et al. / Journal of Organometallic Chemistry 692 (2007) 664–670
Table 3
Synthesis of organotellurium compounds from organic halides and 1a
Run
RX
Temperature (°C)
Time (h)
Product
Yield (%)b
1
2
3
4
5
6
7
8
9
PhCH2Cl
r.t.
r.t.
r.t.
60
r.t.
r.t.
r.t.
60
3
PhCH2TePh (2)
100
100
100
72
98
100
90
o-ClC6H4CH2Cl
m-ClC6H4CH2Cl
PhCH(CH3)Br
H2C@CHCH2Br
H2C@CHCH2Cl
trans-PhCH@CHCH2Cl
CH2@CH(CH2)4Br
0.5
0.5
6
1.5
3
3.5
4
1.5
o-ClC6H4CH2TePh
m-ClC6H4CH2TePh
PhCH(CH3)TePh
H2C@CHCH2TePh
H2C@CHCH2TePh
trans-PhCH@CHCH2TePh
CH2@CH(CH2)4TePh
91
95c
r.t.
N
N
N
N
N
N
Cl
TePh
10
11
12
c-C6H11Br
t-BuBr
60
100
60
24
24
48
c-C6H11TePh
t-BuTePh
60
36
48
N
Br
N
TePh
a
Typical experimental procedures: a mixture of alkyl halide and 1 (1.0–1.1 equiv.) in acetonitrile (ca. 0.5 M solution) was stirred at the temperature
indicated in the Table. After removal of the volatile materials under vacuum, the product was analyzed by 1H and 13C NMR.
b
As the products formed were unstable under the conditions of silica gel chromatography, the yields were determined by 1H NMR of the crude mixture
after adding an internal standard.
c
Slight excess of 1 (1.5 equiv) was used.
as precursors for carbon-centered radicals [9], carbanions
[10], and carbocations [11].
way involving tetravalent tellurium intermediate, while
several attempts to locate the r-bond metathesis pathway
were so far unsuccessful.
2.2. Possible reaction pathways
Morokuma and coworkers already reported on the the-
oretical study on the reductive elimination reaction (the
ligand coupling reaction) of tetrahydrochalcogenide to
dihydrochalcogenide and hydrogen at the MP2 level of the-
ory [12]. They reported that the transition state of the equa-
torial–equatorial coupling is less polar and higher in energy
than that of the apical–equatorial coupling. Since the acti-
vation energies of two pathways are sufficiently large
(39 kJ/mol for tellurium) and the latter pathway should
be more stabilized in polar medium than the former, we
only calculated the apical–equatorial coupling pathway
throughout this study.
Three mechanisms would be envisaged to account for
the experimental results. The first is the nucleophilc attack
of phenyltellanyl anion or its equivalent derived from silyl
telluride to alkyl halides (Scheme 2a). In this mechanism,
polar solvent such as acetonitrile may coordinate to silicon
atom thus enhancing the nucleophilicity of the phenyltella-
nyl anion species. However, the reactivity of organoiodines
is usually highest followed by organobromines and then
organochlorides in the nucleophilic substitution reaction,
but the experimental data did not follow this reactivity
order. Therefore, we believe that this possibility would be
rigorously excluded.
2.3. Theoretical studies
The second is the r-bond metathesis involving four-cen-
tered transition state (Scheme 2b), and the third is the oxi-
dative addition/reductive elimination mechanism involving
tetravalent organotellurium intermediate or transition state
(Scheme 2c). Theoretical investigations revealed the exis-
tence of the oxidative addition/reductive elimination path-
The reactions of trihydrosilyl methyl telluride (2) and
methyl chloride, bromide, and iodide leading to dimethyl
telluride (6) and trihydrosilyl chloride, bromide, and
iodide, respectively, were selected as a model reaction.
Geometry optimizations were performed with the hybrid
B3LYP density functional [13] with a Hey–Wadt effective
core potential (ECP) and outermost valence electron basis
set (LANL2DZ) [14] for silicon, chlorine, bromine, tellu-
rium, and iodine and 6-31G(d) basis set [15] for hydrogen
and carbon. While the d polarization functions are impor-
tant for hypervalent species to obtain more accurate energy
values [16], we believe that the calculation without the
(a) Neucleophilic attack
σ
(c) Oxidative addition/
Reductive elimination.
(b) -Bond metathesis
R
Me3Si TePh
X
Me3Si
TePh
Me3Si TePh R
MeCN
X
R
X
Scheme 2. Possible reaction pathways.

S. Yamago et al. / Journal of Organometallic Chemistry 692 (2007) 664–670
667
d polarization would reasonably reproduce relative reactiv-
ity difference of alkyl halides towards silyl tellurides.
The reaction of 2 and methyl chloride was calculated to
proceed through two transition states 3 and 5, which lead
to tetravalent tellurium intermediate 4 and the products,
respectively. Transition state 3, namely oxidative addition
of methyl chloride to tellurium atom in 2 requires 203 kJ/
mol of activation energy leading to 4. This is an endother-
mic process, and intermediate 4 locates 48 kJ/mol of higher
in energy than the starting reactants. Subsequent reductive
elimination from 4 to 6 is highly exothermic (90 kJ/mol)
with low activation barrier (9 kJ/mol) through transition
state 5. The calculation clearly indicates that the oxidative
addition is the rate determining step. As the reaction of
alkyl chloride with trimethylsilyl phenyl telluride proceeded
at 60 °C for 1 day, the calculated activation energy of the
rate determining step seems to be in good agreement with
the experimental data. As the activation energy of the
reductive elimination is considerably low, this step should
proceed spontaneously from intermediate 4. The overall
reaction is 43 kJ/mol of exothermicity, which must be
responsible to drive the reaction (see Fig. 1).
character compared to the reactants and products.
Intermediate 4 is most polar among them; the tellurium
atom bears 0.77 positive charge and negative charges
are localized mainly on the chloride atom (À0.59) and
the apical carbon atom (À0.23). The observed charge dis-
tributions are in good agreement with the well known
character of hypervalent heteroatom compounds bearing
electron negative apical ligand [16]. As both the
transition states and intermediate should be stabilized
in a polar solvent, the calculated charge distributions
are consistent with the experimentally observed solvent
effects.
The reactions of 2 with methyl bromide and methyl
iodide were also calculated, and similar transition states
and tetravalent tellurium intermediates were obtained in
both cases (Figs. 2 and 3). Transition states 7 and 10 lead-
ing to intermediates 8 and 11, respectively, are calculated to
be higher in energy than transition state 9 and 12 leading to
the final products, respectively. Therefore, the oxidative
addition is also the rate determining steps in both cases.
The transition states and intermediates also possess consid-
erable polar character compared to the reactants and prod-
ucts. Therefore, these reactions should be also strongly
accelerated in a polar solvent.
Mulliken charge analyses indicate that transition states
3 and 5 as well as intermediate 4 possess highly polar
Fig. 1. Geometry (A, °) and relative energies (total energy + ZPE, kJ/mol) of the reactants, TSs, intermediate, and products for the reaction of methyl
chloride with 2. Mulliken charges of the heavy atoms are shown as italic.
Fig. 2. Geometry (A, °) and relative energies (total energy + ZPE, kJ/mol) of the reactants, TSs, intermediate, and products for the reaction of methyl
bromide with 2. Mulliken charges of the heavy atoms are shown as italic.

668
S. Yamago et al. / Journal of Organometallic Chemistry 692 (2007) 664–670
Fig. 3. Geometry (A, °) and relative energies (total energy + ZPE, kJ/mol) of the reactants, TSs, intermediate, and products for the reaction of methyl
iodide with 2. Mulliken charges of the heavy atoms are shown as italic.
The calculated activation energy of the rate determining
step is lowest in the reaction of methyl bromide followed by
that of methyl iodide and then methyl chloride, though the
differences are very small. Therefore, several factors, e.g.,
charge distributions, would also contribute the reactivity
difference of halogen atoms in polar solvent, and more
studies are obviously needed to clarify this point.
ment, and are reported in parts per million (d) from tetra-
methylsilane. IR spectra were recorded on a Shimadzu
FTIR-8200, and are reported in cmÀ1. FAB-MS spectra
were recorded on JEOL IMS-300 spectrometer. 3-Nitrob-
enzyl alcohol was used as a matrix for FAB-MS.
4.2. Materials
3. Conclusion
Unless otherwise noted, materials obtained from com-
mercial suppliers were used without further purification.
Ethereal solvents were distilled from benzophenone ketyl
immediately under argon atmosphere before use. Benzyl-
phenyl telluride, allyl phenyl telluride, and cimnamyl phenyl
telluride were identified by comparison of its 1H NMR
spectrum with that reported in the literature because of sen-
sitivity to oxidation. Trimethylsilyl phenyl telluride (1)
[2a,17], tris(trimethylsilyl)silyl phenyl telluride [18], trim-
ethylgermyl phenyl telluride [2a], and trimethylstannyl phe-
nyl telluride [2a] were prepared according to the literature
method. These metal tellurides are moisture sensitive, but
they can be stored for long period under inert atmosphere.
We have demonstrated that several group14-metal tellu-
rides, especially trimethylsilyl phenyl telluride (1), react
with organic halides to give the corresponding organotellu-
rium compounds and group 14-metal halides in good to
excellent yields. After the volatile metal halides and solvent
are removed under reduced pressure, the essentially pure
organotellurium compounds can be easily obtained. Since
many of the organotellurium compounds are unstable
under purification conditions, this method would provide
a new and practical synthetic route to divalent organotellu-
rium compounds.
Theoretical calculations revealed that the reaction pro-
ceeds through oxidative addition/reductive elimination
pathway involving highly polarized tetravalent organotel-
lurium intermediate. This reaction pathway is rather insen-
sitive to the nature of halogen atom of alkyl halides, and
the oxidative addition of alkyl halides on the tellurium
atom of silyl telluride is the rate determining step in all
cases. While more studies are needed, we believe that the
current work provides a new insight into the reactivity of
hypervalent chalcogen species.
4.3. t-Butyldimethylsilylphenyltelluride
Phenyllithium (52.9 mL, 1.04 M solution in diethyl
ether, 55 mmol) was slowly added to a suspension of tellu-
rium powder (6.38 g, 50 mmol) in 50 mL of THF over
20 min at room temperature. The resulting mixture was
stirred for 20 min until tellurium powder was completely
disappeared. A THF solution of t-butyldimethylsilyl chlo-
ride (8.29 g, 55 mmol) was added at room temperature,
and the resulting solution was stirred for 18 h at this tem-
perature followed by 3 h at 50 °C. The solvent was
removed under reduced pressure, followed by distillation
under reduced pressure (bp. 90.0–91.2 °C/0.1 mmHg) to
give the title compound as slightly yellow oil in 54 % yield
4. Experimental
4.1. General
1H and 13C NMR spectra were measured on Varian
Gemini 2000 (300 MHz for 1H and 75 MHz for 13C) instru-
(8.64 g, 27.0 mmol). H NMR (300 MHz, CDCl3) 0.43 (s,
1
6H), 0.10 (s, 9H), 7.08–7.14 (m, 2H), 7.26–7.31 (m, 1H),

S. Yamago et al. / Journal of Organometallic Chemistry 692 (2007) 664–670
669
7.75–7.79 (m, 2H); 13C NMR (75 MHz, CDCl3) – 1.35,
4.9. o-Chrolobenzylphenyltelluride
19.20, 26.70, 127.29, 128.79, 141.61.
1H NMR (300 MHz, CD3CN) 4.24 (s, 2H), 6.97–7.12
(m, 3H), 7.16–7.23 (m, 2H), 7.28–7.31 (m, 2H), 7.66 (d,
J = 7.8 Hz, 2H); 13C NMR (75 MHz, CD3CN) 10.33,
113.88, 128.39, 129.32, 129.64, 130.70, 130.97, 131.50,
140.61, 140.93.
4.4. Triethoxysilylphenyltelluride
Phenyllithium (1.04 M in cyclohexane/ether, 106 mL,
110 mmol) was slowly added to a suspension of tellurium
powder (12.8 g, 100 mmol) in THF (100 mL) over 30 min
at room temperature, and the resulting mixture was stirred
for 1 h. Chlorotriethoxysilane (21.9 g, 110 mmol) was
added dropwisely over 15 min at room temperature, and
the resulting mixture was stirred for 2 h. Solvent was
removed under reduced pressure followed by distillation
(bp. 83–109 °C/0.55 mmHg) afforded the title compound
in 62% yield (22.8 g) as orange oil. IR (neat) 1476, 1435,
4.10. m-Chrolobenzylphenyltelluride
1H NMR (300 MHz, CD3CN) 4.16 (s, 2H), 6.98–7.33
(m, 7H), 7.63 (d, J = 6.9 Hz, 2H); 13C NMR (75 MHz,
CD3CN) 11.65, 113.92, 127.40, 128.22, 129.59, 130.73,
130.87, 131.31, 134.74, 139.08, 140.67, 145.52.
1
1391, 1165, 1076, 1017, 997, 785, 733, 693, 486, 455; H
4.11. Allylphenyltelluride
NMR (300 MHz, CDCl3) 1.19 (t, J = 7.1 Hz, 9H), 3.85
(q, J = 7.0 Hz, 6H), 7.07–7.16 (m, 2H), 7.20–7.30 (m,
1H), 7.72–7.82 (m, 2H); 13C NMR (75 MHz, CDCl3)
17.61, 59.65, 104.27, 127.37, 129.13, 140.22.
1H NMR (300 MHz, CD3CN) 0.32 (s, 9H), 0.33 (s, 9H),
7.13 (d, J = 8.7 Hz, 1H), 7.31–7.49 (m, 3 H), 7.73–7.79 (m,
1H), 8.01–8.08 (m, 1H); 13C NMR (75 MHz, CDCl3) 0.39,
0.68, 121.59, 122.00, 122.14, 123.99, 125.32, 127.59, 129.60,
130.30, 140.57, 141.81.
4.5. Typical experimental procedure for the synthesis of
organotellurium compounds from alkyl halides and
trimethylsilylphenyltelluride (1). Synthesis of n-
decylphenyltelluride
4.12. Cimnamylphenyltelluride [22]
1H NMR (300 MHz, CDCl3) 3.76 (d, J = 8.1 Hz, 2H),
5.96 (d, J = 15.6 Hz, 1H), 6.44 (dt, 1H), 7.10–7.37 (m,
8H) 7.70–7.76 (m, 2H).
A solution of n-decyl bromide (68.1 mg, 0.30 mmol) and
1 (83.3 mg, 0.30 mmol) in acetonitrile (1.0 mL) was stirred
at 60 °C for 12 h. After the solvent was removed under
reduced pressure, the product was obtained in 100% yield
(45.5 mg) as yellow oil. The product was sufficiently pure
as judged by NMR spectroscopy. As the product was unsta-
ble toward air, further purification was not attempted. IR
4.13. Computational study
All theoretical calculations were carried out with GAUSS-
IAN 98 program [23]. Geometry optimizations were per-
formed with the hybrid B3LYP density functional [13]
with a Hey-Wadt effective core potential (ECP) and outer-
most valence electron basis set (LANL2DZ) [14] for chlo-
rine, bromine, iodine, silicon, and tellurium and 6-31G(d)
[15] basis set for carbon and hydrogen. Intrinsic reaction
coordinate (IRC) analysis [24] was performed near the
transition structure at the same level. Atomic charges were
derived from Mulliken population analysis of the Kohn–
Sham orbitals.
1
(KBr) 1455, 1277, 1192, 887; H NMR (300 MHz, CDCl3)
2.17 (s, 2H); 13C NMR (75 MHz, CDCl3) 102.54, 113.37,
128.82, 151.34; HRMS (FAB) m/z: Anal. Calc. for
C16H26Te (M)+, 348.1097. Found 348.1097%.
4.6. Benzylphenyltelluride [19]
1H NMR (300 MHz, CD3CN) 4.25 (s, 2H), 7.06–7.13
(m, 8H), 7.65 (d, J = 9 Hz, 2H); 13C NMR (75 MHz,
CD3CN) 0.77, 124.52, 144.61.
Acknowledgement
4.7. c-Hexylphenyltelluride [20]
This work is partly supported from a Grant-in-Aid Sci-
entific Research from the Ministry of Education, Culture
and Sports.
1H NMR (300 MHz, CDCl3) 0.26 (s, 9H), 0.31 (s, 9H),
6.77 (s, 2H); 13C NMR (75 MHz, CDCl3) 0.07, 0.67,
120.06, 126.57, 143.29, 149.01.
References
4.8. tert-Butylphenyltelluride [21]
[1] (a) W.P. Weber, Silicon Reagents for Organic Synthesis, Springer-
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