On the reactions of the tetraindium cluster In4[C(SiMe3)3]4: Insertion of the monomeric fragments InC(SiMe3)3 into chalcogen-chalcogen bonds

Article abstract of DOI:10.1016/j.jorganchem.2009.01.034

Treatment of the tetraindium cluster In₄[C(SiMe₃)₃]₄ (1) with diaryl dichalcogenides Aryl-E-E-Aryl (E = S, Se and Te) afforded the corresponding RIn(E-Aryl)₂ [R = C(SiMe₃)₃] comp

Full text of DOI:10.1016/j.jorganchem.2009.01.034

Journal of Organometallic Chemistry 694 (2009) 1918–1921
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
On the reactions of the tetraindium cluster In4[C(SiMe3)3]4: Insertion
of the monomeric fragments InC(SiMe3)3 into chalcogen–chalcogen bonds
a
b,
Clovis Peppe a, , Fabiano Molinos de Andrade , Werner Uhl
*
*
a Laboratório de Materiais Inorgânicos, Departamento de Química, Universidade Federal de Santa Maria, Santa Maria-RS 97105-900, Brazil
b Institut für Anorganische und Analytische Chemie, Universität Münster, D-48149 Münster, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
Treatment of the tetraindium cluster In4[C(SiMe3)3]4 (1) with diaryl dichalcogenides Aryl-E-E-Aryl (E = S,
Se and Te) afforded the corresponding RIn(E-Aryl)2 [R = C(SiMe3)3] compounds by insertion of the mono-
meric fragments InR into the chalcogen–chalcogen bonds. The dimeric formula units adopt different con-
formations in the solid state (Ci vs. C2 h).
Received 8 January 2009
Accepted 19 January 2009
Available online 24 January 2009
Ó 2009 Elsevier B.V. All rights reserved.
Keywords:
Indium
Sulfur
Selenium
Tellurium
Heterocycles
1. Introduction
hydrochalcogenation of terminal alkynes, alkynols and aminoalky-
nes with XIn(EPh)2 (X = Br, I; E = S, Se, Te] [26–29], Pd(0) catalyzed
For many years, cyclopentadienyl derivatives [1–6] and the
monomeric compound with the crowded o-terphenyl ligand
C6H3-2,6-Trip2 (Trip = –C6H2-2,4,6-i-Pr3) [7] were the only well
characterized organanometallic indium(I) compounds. About a
decade ago, the first alkylindium(I) derivative, In4[C(SiMe3)3]4
(1), was obtained by the reaction of InBr with LiC(SiMe3)3. In con-
trast to the cyclopentadienyl compounds it exhibits strong In-In
bonding interactions and has an almost undistorted tetrahedral
cluster of four indium atoms in an oxidation state of +I [8,9]. Com-
pound 1 is soluble in hydrocarbons and is applicable as a facile
source of monomeric InR fragments [R = C(SiMe3)3] in a number
of unprecedented and remarkable chemical reactions [10–18].
For instance, novel indium(III) chalcogenides were obtained
through the complete oxidation of the cluster atoms by elemental
chalcogens or suitable chalcogen atom donors to give heterocub-
ane-type molecules In4R4E4 (E = O, S, Se, Te) [8,19–21]. Reactions
with phenylchalcogen bromides, H5C6-E-Br (E = Se, Te), affor-
ded the dimeric chalcogenolates [PhE(R)InBr]2 (E = Se, Te) [10].
Indium(III) chalcogenolates obtained from indium monohalides
and diphenyl dichalcogenides [22] have been extensively applied
in organic synthesis to generate carbon–chalcogen bonds. Reac-
tions of interest include: ring opening reactions of epoxides with
IIn(EPh)2 (E = S, Se) to the corresponding b-hydroxy selenides
[23] and sulfides [24], ring opening reactions of aziridines with
IIn(SePh)2 to selenocysteine derivatives and selenotreonine [25],
coupling between IIn(EPh)2 (E = S, Se) with vinyl bromides to
vinylic chalcogenides [30], condensations of IIn(EPh)2 (E = S, Se)
with alkyl and acyl halides for the synthesis of unsymmetrical
chalcogenides [31,32]. Some of these reactions are highly stereose-
lective, particularly those leading to vinylic chalcogenides. In order
to gain a better insight into the properties of these reagents, we
started to investigate oxidative reactions involving the tetraindi-
um cluster 1 to generate organoelement indium(III) chalcogeno-
lates. We discuss here the insertion of monomeric fragments InR
into the chalcogen–chalcogen bonds of Aryl-E-E-Aryl (E = S, Se, Te).
2. Results and discussion
2.1. Synthesis of [RIn(l-EAryl)EAryl]2 (Aryl = C6H5, E = S (2), Se (3), Te
(4); Aryl = p-Me-C6H4, E = Te, 5)
Hexane solutions containing 1 equiv. of the tetraindium cluster
1 and 4 equiv. of the corresponding diaryl dichalcogenide (Eq. (1))
were heated under reflux until the characteristic violet color of the
cluster disappeared after about 45 min. Colorless crystals of the
product 2 (92% yield) precipitated directly from the reaction mix-
ture after cooling to room temperature; compounds 3 (89%) and
5 (41%) were obtained as yellow single crystals by adding cyclo-
pentane to the reaction mixtures and cooling to ꢀ20 °C. We were
not able to grow single crystals of compound 4, which was isolated
as a yellow powder in 43% yield after concentration of the hexane
solution at room temperature.
* Corresponding authors. Tel.: +55 55 3220 8868; fax: +55 55 3220 8031.
E-mail address: peppe@quimica.ufsm.br (C. Peppe).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.01.034

C. Peppe et al. / Journal of Organometallic Chemistry 694 (2009) 1918–1921
1919
R
In
n-C6H14
R
+
4 Aryl-E-E-Aryl
In
Δ, 45 min
In
In
R
R
1
R = C(SiMe3)3
Aryl
ð1Þ
E
Aryl-E
R
E-Aryl
In
In
2
R
E
Aryl
Aryl = C6H5, E = S, 2; E = Se, 3; E = Te, 4;
5
Aryl = p-Me-C6H4, E = Te,
2.2. Spectroscopic and structural characterization of compounds 2–5
Fig. 2. Molecular structure of 3. The thermal ellipsoids are drawn at the 50%
probability level. Methyl groups and phenyl hydrogen atoms are omitted. Impor-
tant bond lengths (pm) and angles (°): In1–Se1 2.7525(8), In1–Se2 2.7312(9), In1–
Se3 2.554(1), In2–Se1 2.7601(9), In2–Se2 2.7311(9), In2–Se4 2.553(1), In1–Se1–In2
91.83(2), In1–Se2–In2 92.92(2), Se1–In1–Se2 79.26(2), Se1–In2–Se2 79.13(2).
NMR (1H and 13C) studies in benzene-d6 or toluene-d8 solutions
revealed the equivalence of the aryl groups of the arylchalcogeno-
lato ligands. In all cases only four resonances were detected in the
13C NMR spectra for phenyl carbon atoms which may indicate the
existence of monomeric entities RIn(E-Aryl)2 in solution. A fast ex-
change may occur between bridging and terminal chalcogenolato
groups, however, we did not observe any alteration upon cooling.
Only the mass spectrum of compound 2 revealed higher masses
than calculated for the monomeric formula unit RIn(E-Aryl)2 in
accordance with the association observed for the solid phase. In
all other cases the highest masses correspond to those of the
monomeric formula units. The molecular structures of compounds
2, 3 and 5 are depicted in Figs. 1–3, respectively. They are dimeric
in the solid state containing four-membered In2E2 heterocycles. A
centrosymmetric structure with the bulky alkyl groups on different
sides of the inner ring might be expected as the most favorable one
for these heterocycles, but only 2 adopts the corresponding confor-
mation (Ci symmetry). In contrast, both bulky tris(trimethyl-
silyl)methyl groups are on the same side of the inner heterocycle
Fig. 3. Molecular structure of 5. The thermal ellipsoids are drawn at the 50%
probability level. Methyl groups and phenyl hydrogen atoms are omitted. Impor-
tant bond lengths (pm) and angles (°): In1–Te1 2.948(1), In1–Te2 2.939(1), In1–Te3
2.7632(9), In2–Te1 2.9298(8), In2–Te2 2.8981(9), In2–Te4 2.7646(9), In1–Te1–In2
87.26(2), In1–Te2–In2 88.02(2), Te1–In1–Te2 81.94(2), Te1–In2–Te2 82.97(2).
(C2v symmetry) in compounds 3 and 5. Both terminal chalcogeno-
lato ligands and the phenyl rings attached to the bridging chalco-
gen atoms occupy the opposite side. Molecular symmetry causes
a planar heterocycle in 2, while the inner rings are strongly folded
in 3 and 5 with angles between the normals of the respective InSe2
planes of 41.06(3)° and 45.97(2)°, respectively. By this folding the
steric repulsion between the bulky alkyl groups is considerably
diminished, following the example of dimeric hydrazides which
behave similarly [33,34]. However, the indium atoms approach
to relatively short distances of 3.96 and 4.06 Å. A similar transan-
nular In–In distance (4.00 Å) results already for the planar hetero-
cycle of 2 which is caused by the relatively short In–S bonds.
Folding and formation of a hypothetical C2v isomer of 2 may be
Fig. 1. Molecular structure of 2. The thermal ellipsoids are drawn at the 40%
probability level. Methyl groups and phenyl hydrogen atoms are omitted. Impor-
tant bond lengths (pm) and angles (°): In1–S1 2.452(1), In1–S2 2.626(1), In1–S20
2.561(1), In1–S2–In10 101.10(3), S2–In1–S2– 78.89(3); In10 and S20 generated by
1 ꢀ x, 1 ꢀ y, ꢀz.

1920
C. Peppe et al. / Journal of Organometallic Chemistry 694 (2009) 1918–1921
prevented by a further approach of the indium atoms and, hence,
an enhanced electrostatic repulsion. The terminal In–E bond
lengths are 2.452(1), 2.554 (av.) and 2.764 (av.) Å in 2, 3 and 5,
respectively, while expectedly the bond lengths to the bridging
chalcogen atoms are lengthened to 2.594, 2.744 and 2.929 Å on
average. These values correspond well to those reported previously
[10–18,35–40]. All bridging chalcogen atoms adopt a trigonal pyra-
midal coordination sphere. Compounds similar to 2, 3 and 5 with
arylchalcogenolato ligands in terminal and bridging positions at
indium(III) centers are rare.
1023m, 686m, 676m, 654m. MS (EI, 70 eV): m/z (%, only the most
intense peak,
M
based on the dimer): 788 (0.5)
1/2M+ + InSC6H5, 679 (1) 1/2M+ + In, 564 (5) 1/2M+, 455 (100)
1/2M+ ꢀ SC6H5.
3.3. [RIn(SePh)(l-SePh)]2 (3) [R = C(SiMe3)3]
Yield: 296 mg (94%, based on 0.12 mmol of 1); pale yellow crys-
tals precipitated upon addition of cyclopentane to the n-hexane
solution and cooling of the resulting solution to ꢀ20 °C. M.p. (ar-
gon sealed capillary): 190–192 °C. 1H NMR (C6D6, 400 MHz,
298 K): d = 8.38 (4H, m, ortho-H of phenyl), 7.69 (4H, m, meta-H
of phenyl), 6.92 (2H, m, para-H of phenyl), 0.28 (27H, s, SiMe3).
13C NMR (C6D6, 100 MHz, 298 K): d = 138.48, 135.89, 129.70,
128.86 (all phenyl), 25.01 (In–C), 6.29 (SiMe3). IR (cmꢀ1, paraffin,
CsBr): 1574m, 1257m, 1248m, 1066m, 1020m, 999m, 686m,
666m, 652m. MS (EI, 70 eV, both most intense peaks, M based on
the dimer): m/z (%): 658 (1), 660 (1) 1/2M+; 501 (60), 503 (100)
1/2M+ ꢀ SeC6H5.
3. Experimental
All procedures were carried out under purified argon. n-Hexane
and cyclopentane were dried over LiAlH4. In4[C(SiMe3)3]4 (1) was
prepared according to a literature procedure [2]. Diphenyl dichalc-
ogenides (chalcogen = sulfur, selenium and tellurium) were ob-
tained from commercial sources and used as purchased.
3.1. Synthesis of [RIn(E-Aryl)(l-E-Aryl)]2, general procedure
3.4. [RIn(TePh)(l-TePh)]2 (4) [R = C(SiMe3)3]
About 200 mg of 1 (0.14 mmol) and 4 equiv. of the correspond-
ing diaryldichalcogenide (0.56 mmol) were dissolved in n-hexane
(40 mL). The solutions were heated under reflux for 45 min, until
the color changed from violet to pale yellow. Small quantities of
colorless solids precipitated, which were filtered off. The products
2–5 were isolated from the reaction mixtures as described below.
Yield: 201 mg (44%, based on 0.15 mmol of 1); a pale yellow
powder precipitated upon concentration and cooling of the n-hex-
ane solution to ꢀ20 °C. M.p. (argon sealed capillary): 106–108 °C.
1H NMR (C6D6, 400 MHz, 298 K): d = 8.24 (4H, m, ortho-H of phe-
nyl), 7.86 (4H, m, meta-H of phenyl), 6.95 (2H, m, para-H of phe-
nyl), 0.30 (27H, s, SiMe3). 13C NMR (C6D6, 100 MHz, 298 K):
d = 141.02, 129.97, 128.32, 127.11 (all phenyl), 5.72 (SiMe3), InC
not detected. IR (cmꢀ1, paraffin, CsBr): 1570m, 1256m, 1015m,
997m, 687m, 652m. MS (EI, 70 eV, M based on the dimer): m/z
(%): 523 (1), 525 (1), 527 (1) 1/2M+ ꢀ C(SiMe3)3; 408 (65), 410
(91), 412 (80) Te2(C6H5)2.
3.2. [RIn(SPh)(l-SPh)]2 (2) [R = C(SiMe3)3]
Yield: 292 mg (93%, based on 0.14 mmol of 1); colorless crystals
spontaneously precipitated from the solution at 25 °C. M.p. (argon,
sealed capillary): 233 °C (dec.). 1H NMR (toluene-d8, 400 MHz,
298 K): d = 8.18 (4H, pseudo-d, ortho-H of phenyl), 7.05 (4H, pseu-
do-t, meta-H of phenyl), 6.95 (2H, pseudo-t, para-H of phenyl),
0.26 (27H, s, SiMe3). 13C NMR (toluene-d8, 100 MHz, 298 K):
d = 134.9, 129.96, 129.57, 127.45 (all phenyl), 23.2 (InC), 6.1
(SiMe3). IR (cmꢀ1, paraffin, CsBr): 1579m, 1404w, 1260m, 1078m,
3.5. [RIn(TeC6H4CH3)(l-TeC6H4CH3)]2 (5) [R = C(SiMe3)3]
Yield: 206 mg (51%, based on 0.16 mmol of 1); yellow crystals
precipitated upon addition of cyclopentane to the reaction mixture
Table 1
Crystal data and structure refinement of 2, 3 and 5.
2
3
5
Formula
C44H74In2Si6S4
193(2)
C44H74In2Si6Se4
153(2)
C48H82In2Si6Te4
153(2)
Temperature (K)
Crystal system
Space group [43]
a (Å)
b (Å)
c (Å)
Monoclinic
P21/n (no. 14)
13.7490(8)
12.9662(6)
15.907(1)
90
108.594(4)
90
2687.7(3)
2
Monoclinic
P21/c (no. 14)
19.112(3)
12.042(2)
24.767(4)
90
91.358(3)
90
5699(2)
4
Triclinic
ꢀ
P1 (no. 2)
10.509(3)
13.937(4)
22.016(7)
100.734(6)
95.638(6)
104.470(6)
3032(2)
a
(°)
b (°)
(°)
c
V (10ꢀ30 m3)
Z
2
Dcalc (g cmꢀ3
)
1.396
1.176
1.535
3.518
1.717
2.794
l
(mmꢀ1
)
Crystal size (mm)
Radiation
0.25 ꢁ 0.12 ꢁ 0.12
0.27 ꢁ 0.12 ꢁ 0.06
0.18 ꢁ 0.12 ꢁ 0.06
Mo Ka; graphite monochromator
Theta range (°)
Index ranges
1.71 6 h 6 26.21
ꢀ17 6 h 6 16
ꢀ16 6 k 6 15
ꢀ19 6 l 6 19
3518 (0.0502)
2900
1.64 6 h 6 31.43
ꢀ27 6 h 6 27
ꢀ17 6 k 6 16
ꢀ35 6 l 6 35
17447 (0.0750)
11039
1.50 6 h 6 30.04
ꢀ14 6 h 6 14
ꢀ19 6 k 6 19
ꢀ30 6 l 6 30
17445 (0,0404)
12181
Independent reflections (Rint
Reflections observed
Parameters
)
263
578
563
R =
wR2 = {
R
||Fo| ꢀ |Fc||/
R
|Fo|[I > 2
r
(I)]
0.0357
0.0944
0.470/ꢀ0.478
0.0718
0.0465
0.1044
1.376/ꢀ1.602
R
w(|Fo|2 ꢀ |Fc|2)2/
R
|Fo|2}1/2 (all data)
0.1853
Maximum/minimum residual (1030 e mꢀ3
)
3.085a/ꢀ1.262
a
a
At the indium atoms.

C. Peppe et al. / Journal of Organometallic Chemistry 694 (2009) 1918–1921
1921
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1H NMR (C6D6, 400 MHz, 298 K): d = 7.99 (4H, m, ortho-H of phe-
nyl), 6.79 (4H, m, para-H of phenyl), 2.01 (6H, s, Me of p-tolyl),
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(SiMe3), InC not detected. IR (cmꢀ1, paraffin, CsBr): 1559m,
1260m, 1246m, 1184m, 1007m, 673m, 652m. MS (EI, 70 eV, three
most intense peaks, M based on the dimer): m/z (%): 551 (1), 553
(2), 555 (2) 1/2 M+ ꢀ C(SiMe3)3; 436 (70), 438 (100), 440 (90)
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3.6. Crystal structure determinations of compounds 2, 3 and 5
Single crystals were obtained as described before. The crystallo-
graphic data were collected with a BRUKER apex diffractometer.
The structures were solved by direct methods and refined with
the program SHELXL-97 [41,42] by a full-matrix least-squares meth-
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showed a disorder of the phenyl group attached to the terminal
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4. Supplementary material
CCDC 709974, 709975 and 709976 contain supplementary crys-
tallographic data for 2, 3 and 5. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Acknowledgment
[37] M.L. Cole, D.E. Hibbs, C. Jones, N.A. Smithies, J. Chem. Soc., Daltons Trans.
(2000) 545.
C.P. thanks CNPq for grants, and F.M.A. for the award of a schol-
arship. We are further grateful to the Deutsche Forschungsgeme-
inschaft and the Fonds der Chemischen Industrie for generous
financial support.
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