Generation and detection of tellurane [10-Te-4(C4)] and selenurane [10-Se-4(C4)] having alkyl and aryl ligands

Article abstract of DOI:10.1016/j.tetlet.2005.09.148

Formation of 2,2′-biphenylylenedimethylselenurane and -tellurane was observed by the ¹H, ¹³C, ⁷⁷Se, and ¹²⁵Te NMR studies at low temperature, in the reactions of dibenzoselenophene Se-oxide and 2,2′-biphenylylenedibromotellurane with methyllithium. These hypervalent compounds were unstable and decomposed at room temperature to give the corresponding dibenzochalcogenophenes quantitatively.

Full text of DOI:10.1016/j.tetlet.2005.09.148

Tetrahedron
Letters
Tetrahedron Letters 46 (2005) 8091–8093
Generation and detection of tellurane [10–Te–4(C4)] and
selenurane [10–Se–4(C4)] having alkyl and aryl ligands
Soichi Sato,* Makoto Matsuo, Tsukasa Nakahodo,
Naomichi Furukawa and Tatsuya Nabeshima*
Department of Chemistry, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan
Received 2 June 2005; revised 20 September 2005; accepted 22 September 2005
1
Abstract—Formation of 2,20-biphenylylenedimethylselenurane and -tellurane was observed by the H, 13C, 77Se, and 125Te NMR
studies at low temperature, in the reactions of dibenzoselenophene Se-oxide and 2,20-biphenylylenedibromotellurane with methyl-
lithium. These hypervalent compounds were unstable and decomposed at room temperature to give the corresponding dibenzo-
chalcogenophenes quantitatively.
Ó 2005 Elsevier Ltd. All rights reserved.
Hypervalent compounds of main group elements have
attracted attention as a key compound for generation
of new functional molecules.1 Though r-tetracoordi-
nated chalcogen species (chalcogenuranes) [10–M–4,
M = S, Se, Te]2 are in general less stable than usual chal-
cogen species, which obey the octet rule, chalcogenuranes
can be stabilized by the strongly electronegative atoms
(oxygen, nitrogen, fluorine, etc.) and electron-withdraw-
ing ligands on the apical positions. Five-membered ring
also contributes the stabilization due to fixation of
the hypervalent structure (TBP configuration). Several
chalcogenuranes bearing only carbon ligands have been
reported, but most of the corresponding isolable com-
pounds have been stabilized by one or two five-mem-
bered ring connecting apical and equatorial positions.3
tried to prepare telluranes and sulfuranes bearing biphen-
ylylene and alkyl ligands, but they could not succeed
even in the detection of such telluranes and sulfur-
anes.6,11 Although hexacoordinated hypervalent chalco-
gen (VI) species, pertelluranes having alkyl and/or aryl
ligands recently have been reported by Morrison et al.
and Akiba et al.,7 the direct detection and isolation of
sulfurane and selenurane [10–M–4(C4), M = S, Se] hav-
ing at least one alkyl ligand have never been reported.
We, therefore, tried to synthesize and characterize the
hypervalent chalcogen compounds (IV) having alkyl
and aryl ligands. Here we report the first generation of
2,20-biphenylylenedialkylchalcogenuranes and their
reactivities.
In general, telluranes (IV) are more stable than the cor-
responding selenurane (IV) and sulfurane (IV). Thus, we
tried first to prepare 2,20-biphenylylenedimethyltellu-
rane (2a) [10–Te–4(C4)]. When 2.2 equimolar amounts
of MeLi (1.02 M, diethylether solution) were added to
a suspension of 2,20-biphenylylenedibromotellurane (1)
in anhydrous tetrahydrofuran-d8 (THF-d8) in an NMR
tube (/ 5 mm) under an argon atmosphere at ꢀ78 °C,
the mixture turned to a yellow homogeneous solution.
We have systematically studied the syntheses and char-
acterization of organo-chalcogenuranes [10–M–4(C4),
M = S, Se, Te], and have succeeded in detection and iso-
lation of the new chalcogenuranes having only carbon
ligands.4 However the ligands employed in the prepara-
tion of these chalcogenuranes (IV) have been restricted
to aryl groups. Gedridge et al. prepared tetramethyl-
and tetravinyl-telluranes as a hypervalent organotellu-
rium (IV) compound.5 Hellwinkel et al. and Hori et al.
1
Structure of the product 2a was identified by the H,
13C, 125Te NMR experiments at low temperature8
(Scheme 1).
Keywords: Hypervalent; Tellurane; Selenurane; Sulfurane; Ligand
coupling reaction; Pseudorotation.
1
The H and 13C NMR spectra of the product 2a in the
*
Corresponding authors. Tel./fax: +81 29 853 4527 (S.S.); tel./fax:
+81 29 853 4507 (T.N.); e-mail addresses: sato@chem.tsukuba.ac.jp;
nabesima@chem.tsukuba.ac.jp
aromatic region revealed that the two benzene rings on
the biphenylylene group are equivalent. In the 1H
0040-4039/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2005.09.148

8092
S. Sato et al. / Tetrahedron Letters 46 (2005) 8091–8093
2.2 equiv
MeLi
Te
THF / -78 ˚C
Br
Br
1
X
r.t.
1.0 equiv
X
Me3SiOTf
MeLi
Me
Me
2.2 equiv
2a (X = Te)
2b (X = Se)
3 (X = Te)
5 (X = Se)
7 (X = S)
THF / -90 ˚C
X
O
4 (X = Se)
6 (X = S)
Scheme 1. Preparation of chalcogenuranes having alkyl and aryl ligands.
NMR two doublet and two triplet peaks assigned to the
aromatic rings were observed. A set of six peaks in 13C
NMR clearly indicates that there is one kind of benzene
rings.9 Interestingly, the 1H signal of the methyl protons
on 2a appeared at 1.67 ppm together with satellite
selenophene Se-oxide (4) reacted with 2.2 equimolar
amounts of MeLi (1.02 M, diethylether solution) in the
presence of trimethylsilyl triflate (Me3SiOTf) in anhy-
drous tetrahydrofuran-d8 in an NMR tube (/ 5 mm)
under an argon atmosphere at ꢀ90 °C. The mixture
turned to a pale yellow homogeneous solution. This
product 2b was characterized by the 1H, 13C, 77Se
NMR experiments at ꢀ90 °C.8
peaks due to 1H–125Te spin–spin coupling (2JH–Te
=
36.0 Hz) as shown in Figure 1. The integral ratio of
these satellite peaks and the total peaks is nearly equal
to the natural abundance of 125Te atoms. Furthermore,
the proton non-decoupled 125Te signal of 2a in THF-d8
appeared at 154 ppm as a septet due to a spin–spin
coupling between the tellurium and the hydrogen nuclei
of the two methyl groups (2JTe–H = 36.0 Hz). The 2JTe–H
value is nearly the same with that of Me4Te (34.0 Hz).5
These results suggest that the two methyl ligands com-
bine directly with the central tellurium atom and the
pseudorotation of 2a took place rapidly on the NMR
time scale at low temperature.10
1
The H and 13C NMR spectra of the compound 2b in
the aromatic region supported equivalence of the two
benzene rings in the biphenylylene group. These signal
patterns were similar to those of 2a. The methyl pro-
tons on 2b appeared as a main peak at 1.74 ppm
together with the satellite peaks due to spin–spin cou-
pling between the hydrogen and the selenium nuclei
(2JH–Se = 17.5 Hz) in 1H NMR (Fig. 2). Intensity of
the satellite peaks depended on the natural abundance
of the 77Se nucleus. The proton non-decoupled 77Se sig-
nal of 2b appeared at 210 ppm as a septet due to 77Se–1H
spin–spin coupling (2JSe–H = 17.5 Hz). Consequently,
the two methyl ligands are considered to be located
directly on the central selenium atom and pseudorota-
tion in 2b occurred faster compared to the NMR time
Next, we tried to prepare the 2,20-biphenylylenedimeth-
ylselenurane (2b) [10–Se–4(C4)]. A suspension of dibenzo-
Figure 1. Proton non-decoupling 125Te NMR (126 MHz, THF-d8,
ꢀ78 °C) (left) and 1H NMR (400 MHz, THF-d8, ꢀ78 °C) (right) of 2a.
Figure 2. Proton non-decoupling 77Se NMR (76 MHz, THF-d8,
ꢀ90 °C) (left) and 1H NMR (400 MHz, THF-d8, ꢀ90 °C) (right) of 2b.

S. Sato et al. / Tetrahedron Letters 46 (2005) 8091–8093
8093
scale even at low temperature.10 Thus we could
References and notes
succeeded in the direct detection of 2,20-biphenylylene-
dimethylselenurane 2b by low temperature NMR experi-
ments. As far as we know, this is the first detection of
selenurane [10–Se–4(C4)] containing alkyl ligands.
1. (a) Hayes, R. A.; Martin, J. C. Sulfurane Chemistry. In
Organic Sulfur Chemistry: Theoretical and Experimental
Advances; Bernardi, F., Csizmadia, I. G., Mangini, A.,
Eds.; Elsevier: Amsterdam, 1985; pp 408–483, and refer-
ences cited therein; (b) Bergman, J.; Engman, L.; Siden, J.
Tetra- and Higher-valent (Hypervalent) Derivatives of
Selenium and Tellurium. In The Chemistry of Organic
Selenium and Tellurium Compounds; Patai, S., Rappoport,
Z., Eds.; John Wiley and Sons: New York, 1986; Vol. 1,
pp 517–558 (see also references cited therein); (c) Chem-
istry of Hypervalent Compounds; Akiba, K.-y., Ed.; Wiley-
VCH: New York, 1999; (d) The Organic Chemistry of
Tellurium; Irgolic, K. J., Ed.; Gordon and Breach: New
York, 1974; pp 234–241 (see also references cited therein);
(e) Hoffmann, R.; Howell, J. M.; Rossi, A. R. J. Am.
Chem. Soc. 1976, 98, 2484–2492.
Trost et al. and Hori et al. have reported the generation
and reactivities of 2,20-biphenylylene diaryl sulfuranes
[10–S–4(C4)].11 They prospected that these sulfuranes
should have a configuration similar to that of products
2a,b. Immediate ligand coupling reactions of 2,20-biphen-
ylylene diaryl sulfuranes usually proceed at room tem-
perature to afford the corresponding o-terphenyl aryl
sulfide derivatives quantitatively. On the other hand,
both products 2a,b decomposed to give only dibenzotel-
lurophene 3 or dibenzoselenophene 5 quantitatively,
which are probably produced by the ligand coupling
reaction without a ring-opening of dibenzochalcogeno-
phene moiety. The other corresponding ligand coupling
product of 2a,b, ethane, could not be detected by NMR
experiments at room temperature.11e
2. Michalak, R. S.; Wilson, S. R.; Martin, J. C. J. Am. Chem.
Soc. 1984, 106, 7529–7539.
3. (a) Wittig, G.; Fritz, H. Liebigs Ann. Chem. 1952, 577, 39–
46; (b) Hellwinkel, D.; Fahrbach, G. Liebigs Ann. Chem.
1968, 712, 1–20; (c) Hellwinkel, D.; Fahrbach, G. Liebigs
Ann. Chem. 1968, 715, 68–73; (d) Hellwinkel, D. Ann. NY
Acad. Sci. 1972, 192, 158–166; (e) Smith, C. S.; Lee, J.-S.;
Titus, D. D.; Ziolo, R. F. Organometallics 1982, 1, 350–354.
4. (a) Sato, S.; Takahashi, O.; Furukawa, N. Coord. Chem.
Rev. 1998, 176, 483–514; (b) Furukawa, N.; Sato, S. In
Organosulfur Chemistry: Topics in Current Chemistry; Page,
P. C. B., Ed.; Springer: Berlin, 1999; Vol. 205, pp 89–129.
5. Gedridge, R. W., Jr.; Harris, D. C.; Higa, K. T.; Nissan,
R. A. Organometallics 1989, 8, 2817–2820.
Furthermore, we tried to prepare the 2,20-biphenylylene-
dimethylsulfurane (2c, X@S) [10–S–4(C4)] using di-
benzothiophene S-oxide 6 according to a method
similar to that for the corresponding selenurane 2b.
However, the corresponding sulfurane 2c could not be
detected by NMR experiments even at ꢀ90 °C, and only
dibenzothiophene 7 as a final product was observed by
NMR experiments at room temperature.11d,e
6. Hellwinkel, D.; Fahrbach, G. Chem. Ber. 1968, 101, 574–
584.
In conclusion, we reported that the formation of 2,20-
biphenylylenedimethyltellurane 2a and -selenurane 2b
having alkyl and aryl ligands was detected in the reac-
tions of the corresponding precursors 1 and 4 with meth-
yllithium by various NMR spectroscopies at low
temperature. In each chalcogenurane (IV), pseudorota-
tion between two ligands on the central atom should
take place rapidly on the NMR time scale even under
low temperature and chalcogenuranes 2 decomposed
at room temperature to give the corresponding dibenzo-
chalcogenophenes quantitatively. Further studies are in
progress to detect and isolate novel chalcogenanes hav-
ing other carbon ligands.
7. (a) Haaland, H.; Verne, H. P.; Volden, H. V.; Morrison,
J. A. J. Am. Chem. Soc. 1995, 117, 7554–7555; (b) Blake, A.
J.; Pulham, C. R.; Greene, T. M.; Downs, A. J.; Haaland,
A.; Verne, H. P.; Volden, H. V. J. Am. Chem. Soc. 1994,
116, 6043–6044; (c) Miyasato, M.; Minoura, M.; Yama-
moto, Y.; Akiba, K.-y. Chem. Lett. 2002, 288–289.
8. 2,20-Biphenylylenedimethyltellurane (2a); 1H NMR
(400 MHz, THF-d8, ꢀ78 °C) d 1.67 (s, with satellite peaks:
JH–Te = 36.0 Hz, 6H), 7.29 (t, J = 8.0 Hz, 2H, 4-ArH), 7.37
(t, J = 8.0 Hz, 2H, 5-ArH), 7.62 (d, J = 8.0 Hz, 2H, 3-ArH),
8.10 (d, J = 8.0 Hz, 2H, 6-ArH). 13C NMR (100 MHz,
THF-d8, ꢀ78 °C) d 20.7, 122.9, 128.6, 129.4, 132.0, 139.4,
144.6. 125Te NMR (126.3 MHz, THF-d8, ꢀ78 °C) d 154
(sept, JTe–H = 36.0 Hz, relative to Me2Te). 2,20-Biphenyl-
1
ylenedimethylselenurane (2b); H NMR (400 MHz, THF-
d8, ꢀ90 °C) d 1.74 (s, with satellite peaks: JH–Se = 17.5 Hz,
6H), 7.38 (t, J = 8.0 Hz, 2H, 4-ArH), 7.45 (t, J = 8.0 Hz,
2H, 3-ArH), 7.96 (d, J = 8.0 Hz, 2H, 3-ArH), 8.23 (d,
J = 8.0 Hz, 2H, 6-ArH). 13C NMR (100 MHz, THF-d8,
ꢀ90 °C) d 23.7, 123.8, 125.6, 126.9, 127.7, 139.3, 140.3. 77Se
17.5 Hz, relative to Me2Se). The 1H and 13C NMR chemical
shifts of both products 2a,b were assigned by the cross peaks
observed in the two dimensional NMR spectra.
Acknowledgments
This work was supported by the Ministry of Education,
Science, Sports, and Culture, Japan [Grant-in-Aid for
Scientific Research on Priority Areas: Grant No.
09239104, Grant-in-Aid for Scientific Research (B):
Grant No. 11440186, and Grant-in-Aid for Encourage-
ment of Young Scientists: Grant No. 10740286], and the
Fund of Tsukuba Advanced Research Alliance (TARA)
project (University of Tsukuba).
NMR (76 MHz, THF-d8, ꢀ90 °C) d 210 (sept, JSe–H
=
9. Sato, S.; Furukawa, N. Chem. Lett. 1994, 889–892.
10. Ogawa, S.; Sato, S.; Erata, T.; Furukawa, N. Tetrahedron
Lett. 1992, 33, 1915–1918.
11. (a) LaRochelle, R. W.; Trost, B. M. J. Am. Chem. Soc.
1971, 93, 6077–6086; (b) Harrington, D.; Weston, J.;
Jacobus, J.; Mislow, K. J. Chem. Soc., Chem. Commun.
1972, 1079–1080; (c) Hori, M.; Kataoka, T.; Shimizu, H.;
Miyazaki, M. Chem. Lett. 1972, 515–520; (d) Trost, B. M.;
Arndt, H. C. J. Am. Chem. Soc. 1973, 95, 5288–5298; (e)
Hori, M.; Kataoka, T.; Shimizu, H.; Miyagaki, M. Chem.
Pharm. Bull. 1974, 22, 2020–2029.
Supplementary data
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.tetlet.
2005.09.148.