Novel multi-chalcogen ring systems with three different chalcogen atoms: Synthesis, structure and redox property of five-membered trichalcogenaheterocycles

Article abstract of DOI:10.1039/b205445k

The molecular structure of novel five-membered trichalcogenaheterocycles with three different chalcogen atoms, sulfur, selenium and tellurium, has been determined by crystallographic studies.

Full text of DOI:10.1039/b205445k

Novel multi-chalcogen ring systems with three different chalcogen atoms:
synthesis, structure and redox property of five-membered
trichalcogenaheterocycles†
Satoshi Ogawa,*a Satoko Yoshimura,a Noriyoshi Nagahora,a Yasushi Kawai,b Yuji Mikatac and Ryu
Sato*a
a Department of Chemical Engineering, Faculty of Engineering, Iwate University, Morioka 020-8551, Japan.
E-mail: ogawa@iwate-u.ac.jp; Fax: +81-19-621-6327; Tel: +81-19-621-6934
b Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
c
KYOUSEI Science Center, Nara Women’s University, Nara 630-8506, Japan
Received (in Cambridge, UK) 6th June 2002, Accepted 17th July 2002
First published as an Advance Article on the web 29th July 2002
The molecular structure of novel five-membered trichalco-
genaheterocycles with three different chalcogen atoms,
sulfur, selenium and tellurium, has been determined by
crystallographic studies.
different chalcogen atoms, sulfur, selenium and tellurium. The
sulfur and tellurium atoms at the 1- and 3-positions are almost
coplanar with the benzene ring, while the selenium atom at the
The unusual 7p electron structure of certain five-membered
rings has allowed the construction of a unique, reversible one-
electron redox system.1 Recently, we reported reversible one-
electron redox responses by the use of 4,7-disubstituted benzo-
trichalcogenoles containing sulfur and/or selenium atoms and
found by EPR spectroscopy that their radical cation salts
obtained on treatment with one-electron oxidant had unusual 7p
frameworks.2 However, to date, five-membered trichalcoge-
noles with a tellurium atom or atoms have not been obtained due
to their instability and/or to synthetic limitations.3 On the other
hand, incorporation of a tellurium atom in the five-membered
ring is expected to significantly enhance their electron-donating
ability and lead to a new field of molecular device.4 Herein we
present the synthesis and structural determination by X-ray
crystallographic analysis on the novel trichalcogenoles contain-
ing different chalcogen atoms with multi-chalcogen linkages.
An elegant approach to the synthesis of trichalcogenoles
containing a heavier chalcogen, tellurium, consisted of the
transmetallation of titanacycle having two Cp* units as the
synthetic intermediate. We synthesized 2-isopropyl-5-methox-
ybenzenethiol, which has two ortho-directing groups, methoxy
and mercapto groups, at appropriate positions by a sequence of
methylation, double bromination, selective mono-debromina-
tion and sulfurization of commercially available 4-isopropyl-
Scheme 1 Reagents and conditions: i, (a) K2CO3, acetone (b) MeI; ii, Br2–
Fe, CCl4; iii, (a) n-BuLi, Et2O (b) H+/H2O; iv, (a) Mg, THF (b) S8 (c) H+/
H2O; v, (a) Mg, THF (b) Se (c) H+/H2O; vi, (a) n-BuLi, TMEDA (b) S8, Se,
or Te (c) Cp*2TiCl2, THF.
5
phenol. 2,2-Bis(h -pentamethylcyclopentadienyl)-4-isopropyl
7-methoxy-1,3,2-benzothiatelluratitanole,asyntheticequivalent
of unstable ortho-benzenedichalcogenol with sulfur and tellu-
rium, was prepared in moderate yield by ortho-lithiation,
addition of elemental tellurium and protection with the
corresponding titanocene dichloride with two Cp* units
(Scheme 1). Although the physical and spectroscopic data for
titanacycles 1a–f are in perfect agreement with those of the
proposed structures, one of the solid-state structures, 1b, was
confirmed by X-ray crystallographic analysis (Fig. 1).‡
Transformation into trichalcogenole 2a–d was successfully
carried out, namely, by the reaction of the titanole with
electrophiles containing one sulfur or selenium unit, sulfur
dichloride or selenium oxychloride (Scheme 2). The successful
incorporation of sulfur–tellurium and selenium–tellurium link-
ages is significant since the tellurium-containing five-mem-
bered trichlcogenoles have not been isolated.
The crystal structures of thiaselenetellurole 2b and dis-
elenatellurole 2d were confirmed by X-ray crystallographic
analyses.‡ Fig. 2 shows the ORTEP view of 2b that has three
Fig. 1 Molecular structure of 1b (hydrogen atoms omitted for clarity).
Selected bond distances (Å) and angles (°): Ti(2)–Se(3) 2.553(2), Ti(1)–
S(1) 2.428(3), S(1)–C(8) 1.77(1), Se(3)–C(9) 1.89(1); Se(3)–Ti(2)-S(1)
81.80(9), Ti(2)–Se(3)–C(9) 94.9(4), Ti(2)–S(1)–C(8) 103.4(4); Ti(2)–
Se(3)–C(9)–C(8) 32.3(10), Ti(2)–S(1)–C(8)–C(9) 228.5(9).
† Electronic supplementary information (ESI) available: satisfactory char-
acterizing data for all the new compounds. Typical experimental procedure,
physical and spectroscopic data of all the new compounds and ORTEP view
of 2d. See http://www.rsc.org/suppdata/cc/b2/b205445k/
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CHEM. COMMUN., 2002, 1918–1919
This journal is © The Royal Society of Chemistry 2002

atoms. The sulfur–selenium and selenium–tellurium bond
lengths are similar to those of acyclic molecules.5
Analysis of the cyclic voltammetric responses is diagnostic
for an essentially electrochemically reversible anodic step.
Cyclic voltamograms of 2b and 2d in acetonitrile at 20 °C under
argon atmosphere exhibited quasi-reversible redox waves (2b:
Epa = 0.39 V, Epc = 0.25 V; 2d: Epa = 0.36 V, Epc = 0.26 V)
versus Ag/0.01 mol dm23 AgNO3 (scan rate 100 mV s21). As
expected, incorporation of a heavier chalcogen, tellurium,
lowered oxidation peaks compared with sulfur or selenium
analogues,2 which could be explained by the ionization
potential arising from energy of the highest occupied molecular
orbital.6
In conclusion, we have shown that new redox active
trichalcogenaheterocycles with sulfur, selenium and tellurium
can be prepared from dichalcogenatitanacycles. Further studies
on reactions of mixed chalcogen ring systems are under way.
Scheme 2 Reagents and conditions: i, SCl2, THF; ii, SeOCl2, THF.
Notes and references
‡
Crystal data for 1b: C30H42OSSeTi, M = 577.58, orthorhombic, a =
10.109(4), b = 14.855(4), c = 18.680(4) Å, V = 2805(1) Å3, Z = 4, T =
296 K, space group P212121 (no. 19), Dc = 1.367 g cm23, m(Cu-Ka) =
49.04 cm21, 5630 reflections measured, 2852 unique (Rint = 0.107), 307
parameters, R = 0.055, Rw = 0.085 (on 1834 observed data [I > 3s(I)]).
CCDC 187544.
Crystal data for 2b: C10H12OSSeTe, M = 386.82, monoclinic, a =
7.373(2), b = 16.563(3), c = 10.046(2) Å, b = 94.66(2)°, V = 1222.7(5)
Å3, Z = 4, T = 294 K, space group P21/a (no. 14), Dc = 2.101 g cm23
,
m(Mo-Ka) = 55.5 cm21, 2420 reflections measured, 2240 unique (Rint
=
0.008), 176 parameters, R = 0.021, Rw = 0.037 (on 1926 observed data [I
> 1.50s(I)]). CCDC 187545.
Crystal data for 2d: C10H12OSe2Te, M = 433.72, monoclinic, a =
7.389(3), b = 16.581(3), c = 10.165(2) Å, b = 93.14(3)°, V = 1243.6(6)
Å3, Z = 4, T = 296 K, space group P21/a (no. 14), Dc = 2.316 g cm23
,
m(Mo-Ka) = 82.1 cm21, 2467 reflections measured, 2282 unique (Rint
=
0.013), 176 parameters, R = 0.033, Rw = 0.039 (on 2192 observed data [I
> 0.00s(I)]). CCDC 187546.
See http://www.rsc.org/suppdata/cc/b2/b205445k/ for crystallographic
data in .cif or other electronic format.
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Fig. 2 Molecular structure of 2b. Selected bond distances (Å) and angles (°):
Te(3)–Se(2) 2.5306(5), Se(2)–S(1) 2.2218(9), Te(3)–C(8) 2.101(3), S(1)–
C(9) 1.779(3); Se(2)–Te(3)–C(8) 86.16(8), Se(2)–S(1)–C(9) 99.68(10),
Te(3)–Se(2)–S(1) 90.54(3), Te(3)–C(8)–C(9) 121.2(2), S(1)–C(9)–C(8)
119.6(2); S(1)–Se(2)–Te(3)–C(8) 35.98(7), Te(3)–Se(2)–S(1)–C(9)
242.83(9), Se(2)–S(1)–C(9)–C(8) 36.8(2), Se(2)–Te(3)–C(8)–C(9)
225.8(2), Te(3)–C(8)–C(9)–S(1) 24.4(3).
5 I. Hargittai and B. Rozsonzai, in The Chemistry of organic selenium and
tellurium compounds, Vol. 1, eds. S. Patai and Z. Rappoport, John Wiley
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6 Unpublished results from our laboratory. The data will be discussed in a
full paper.
2-position lies out of this plane (S(1)–Se(2)–Te(3)–C(8)
35.98(7), Te(3)–Se(2)–S(1)–C(9) 242.83(9)). The distorted
geometry of the five-membered ring implies the presence of
lone-pair–lone-pair repulsion of three divalent chalcogen
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