Syntheses and crystal structures of the homoleptic [Et4N][M(SC6H4Me-p)4] (M = Ga, In) and [Et4N][Ga(SePh)4]

Article abstract of DOI:10.1016/j.molstruc.2009.07.010

Treatment of [Et₄N][GaCl₄] with four equivalents of NaQR in methanol afforded the substitution complexes [Et₄N][Ga(QR)₄] (QR = SC₆H₄Me-p 1, QR = SePh 3), while the indium analogues [Et

Full text of DOI:10.1016/j.molstruc.2009.07.010

Journal of Molecular Structure 936 (2009) 15–18
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Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Syntheses and crystal structures of the homoleptic [Et4N][M(SC6H4Me-p)4]
(M = Ga, In) and [Et4N][Ga(SePh)4]
b
Yan-Gong Han a, Chao Xu a, Taike Duan a, Qian-Feng Zhang a, , Wa-Hung Leung
*
a Institute of Molecular Engineering and Applied Chemistry, Anhui University of Technology, Ma’anshan, Anhui 243002, PR China
b Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Treatment of [Et4N][GaCl4] with four equivalents of NaQR in methanol afforded the substitution complexes
[Et4N][Ga(QR)4] (QR = SC6H4Me-p 1, QR = SePh 3), while the indium analogues [Et4N][In(SC6H4Me-p)4] (2)
was prepared by the reaction of InCl3ꢀ3H2O and NaSC6H4Me-p in the presence of [Et4N]ClꢀxH2O. The struc-
tures of these three complexes, as determined by single-crystal X-ray diffraction, feature well-separated
cations and anions with the metal centers of the anions tetrahedrally coordinated to four thiolate or selen-
olate ligands. The thermal stability of the three complexes was studied by thermal gravimetric analysis.
Crown Copyright Ó 2009 Published by Elsevier B.V. All rights reserved.
Received 18 May 2009
Accepted 14 July 2009
Available online 19 July 2009
Keywords:
Synthesis
Crystal structure
Indium-thiolate complex
Gallium-thiolate complex
Gallium-selenolate complex
1. Introduction
2. Experimental
Many indium thiolates and selenolates have been synthesized,
owingtotheirpotentialapplicationformaterialsassingle-sourcepre-
cursors [1–3]. However, the analogues of gallium complexes with
thiolate and selenolate ligands have not been well explored [4,5].
Although solid-state gallium chalcogenide compounds have come
underincreasinginvestigationinthepasttwodecades[6–8], thereac-
tivities and structures of soluble gallium compounds have not been
extensively studied. There are several literatures concerning neutral
homoleptic gallium alkylthiolate and arylthiolate compounds, for
examples, a series of Ga(SR)3 compounds were obtained from reac-
tions of GaCl3 and Me3SiSR, or from GaPh3 with RSH (R = Me, Et,
n-Pr, i-Pr, Ph, CH2Ph) [9,10]. Monomeric three-coordinate gallium
Ga[Q(2,4,6-t-Bu3C6H2)]3 (Q = S, Se) were formed mainly due to the
bulkythiolateandselenolate[11].Thefour-coordinategalliumanions
[Ga(SR)4]ꢁ (R = Me, Et, i-Pr, Ph, 2,3,5,6-Me4C6H, 2,4,6-i-Pr3C6H2) were
isolated from the reactions of (NH4)[GaCl4] with four equivalents of
the corresponding thiolate ligands [12,13]. Likewise, the anionic in-
dium selenolates [In(SePh)4]ꢁ and [In(SePh)3(SeH)]ꢁ were synthe-
sized from the above similar reactions of gallium complexes and
structurally characterized by Ibers [14]. However, no analogue of gal-
lium-tetraselenolates [Ga(SeR)4]ꢁ has been reported to date. Herein
we report the synthesis and molecular structures of the homoleptic
compounds with tetrahedral gallium coordination, [Et4N][Ga
(SC6H4Me-p)4] and [Et4N][Ga(SePh)4].
2.1. Materials and measurements
All syntheses were performed in oven-dried glassware under a
purified nitrogen atmosphere using standard Schlenk techniques.
Ga2O3, InCl3ꢀ3H2O, p-thiocresol (HSC6H4Me-p), and PhSeSePh were
purchased from Alfa Chemical Company and were used as sup-
plied. All other reagents and solvents were used without further
purification. [NH4][GaCl4] was prepared according to the literature
method [15]. All elemental analyses were performed using a Per-
kin-Elmer 2400 CHN analyzer. Infrared spectra were recorded on
a Digilab FTS-40 spectrophotometer with the use of pressed KBr
pellets. Positive FAB mass spectra were recorded on a Finnigan
TSQ 7000 spectrometer. 1H NMR spectra were recorded on a Bruker
ALX 300 spectrometer operating at 300 MHz and with reference to
SiMe4 (1H). Thermogravimetric analysis (TGA) was performed by
using a Delta TGA instrument.
2.2. Preparation of [Et4N][Ga(SC6H4Me-p)4] (1)
To a solution of [Et4N][GaCl4] (171 mg, 0.50 mmol) in methanol
(10 ml) was added dropwise NaSC6H4Me-p (292 mg, 2.00 mmol) in
10 ml of methanol with stirring. The mixture was stirred at room
temperature for 30 min. Fine white solids were observed. The
precipitates were collected by suction filtration and washed twice
with 10 ml portions of diethyl ether. White air-stable solids were
obtained and further recrystallized from DMF/diethyl ether to give
colorless block crystals of 1 in five days. Yield: 301 mg, 87%. IR
* Corresponding author. Tel./fax: +86 555 2312041.
E-mail address: zhangqf@ahut.edu.cn (Q.-F. Zhang).
0022-2860/$ - see front matter Crown Copyright Ó 2009 Published by Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2009.07.010

16
Y.-G. Han et al. / Journal of Molecular Structure 936 (2009) 15–18
(KBr, cmꢁ1): (C–S) 648 (m). 1H NMR (DMSO-d6, ppm): d 1.01 (s,
m
Table 1
Crystal data and structure refinement for complexes [Et4N][Ga(SC6H4Me-p)4] (1),
[Et4N][In(SC6H4Me-p)4] (2), [Et4N][Ga(SePh)4] (3).
12H, CH3 in Et4N), 2.14 (s, 12H, CH3), 2.93 (t, 8H, CH2 in Et4N),
6.72–7.16 (m, 16H, Ph). MS (FAB): m/z 562 (M+ꢁ[Et4N]). Anal.
Calcd. for C36H48NS4Ga: C, 62.4; H, 6.98; N, 2.02. Found: C, 62.2;
H, 6.94; N, 1.99%.
Complex
1
2
3
Formula
Formula weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
b (°)
V (Å3)
C36H48NS4Ga
692.71
Monoclinic
Cc
22.5014(4)
10.6150(2)
15.8714(3)
103.614(1)
3684.41(12)
4
C36H48NS4In
737.81
Monoclinic
Cc
22.6647(4)
10.5550(2)
16.0707(3)
103.399(1)
3739.88(12)
4
C32H40NSe4Ga
824.21
Monoclinic
P21/c
12.1527(3)
12.9180(3)
21.4221(4)
93.679(1)
3356.09(11)
4
2.3. Preparation of [Et4N][In(SC6H4Me-p)4] (2)
To a slurry solution of InCl3ꢀ3H2O (138 mg, 0.50 mmol) and
[Et4N]ClꢀxH2O (86 mg, 0.50 mmol) in methanol (15 ml) was added
dropwise NaSC6H4Me-p (292 mg, 2.00 mmol) in 10 ml of methanol
with stirring. The mixture was stirred at room temperature for
15 min, during which time a fine white solid gradually separated
from the solution. The precipitates were collected by suction filtra-
tion and washed twice with 10 ml portions of diethyl ether. White
air-stable solids were obtained and further recrystallized from
DMF/diethyl ether to give colorless block crystals of 2 in three
Z
Dcalcd. g cmꢁ3
Temperature, K
F(0 0 0)
1.249
296(2)
1464
0.998
1.310
296(2)
1536
0.879
1.631
296(2)
1624
5.179
l
(Mo K
a
) mmꢁ1
No. reflections measured
No. unique reflections
No. observed reflections
No. parameters
17534
6078
3471
379
17796
7408
6400
379
33377
7689
5199
344
days. Yield: 283 mg, 78%. IR (KBr, cmꢁ1):
m
(C–S) 641 (m). 1H
NMR (DMSO-d6, ppm): d 1.05 (s, 12H, CH3 in Et4N), 2.12 (s, 12H,
CH3), 2.90 (t, 8H, CH2 in Et4N), 6.71–7.25 (m, 16H, Ph). MS (FAB):
m/z 607 (M+ꢁEt4N]). Anal. Calcd. for C36H48NS4In: C, 58.6; H,
6.56; N, 1.90. Found: C, 58.4; H, 6.52; N, 1.87%.
Rint
0.0428
0.0155
0.0370
R1a, wR2b (I > 2
r
(I))
0.0468, 0.1019
0.0979, 0.1209
1.019
0.0268, 0.0664
0.0335, 0.0703
1.017
0.0292, 0.0663
0.0590, 0.0766
0.941
R1a, wR2b (all data)
GoFc
Flack value
0.00(0)
+0.307, ꢁ0.210
0.00(0)
+0.354, ꢁ0.244
–
Final diff. peaks (e Åꢁ3
)
+0.368, ꢁ0.391
2.4. Preparation of [Et4N][Ga(SeC6H5)4] (3)
P
P
a
R1 = jjF0j ꢁ jFcjj= jF0j;
P
P
2
2 1=2
wR2 = ½ wðjF20j ꢁ jFc2jÞ = wjF20j ꢂ
;
b
c
To a slurry of [Et4N][GaCl4] (171 mg, 0.50 mmol) in methanol
(10 ml) was added dropwise NaSePh (358 mg, 2.00 mmol) (pre-
pared in situ by the reaction of PhSeSePh and NaBH4 in a 1:2 mol
ratio) in 10 ml of methanol with stirring. The mixture was stirred
at room temperature for 30 min. Fine white solids were observed.
The solution was cooled to 0 °C and the precipitates were collected
by filtration and then washed twice with 10 ml portions of diethyl
ether. White air-stable solids were obtained and further recrystal-
lized from DMF/diethyl ether to give colorless block crystals of 3 in
P
2
1=2
GoF = ½ wðjF0j ꢁ jFcjÞ =ðNobs ꢁ NparamÞꢂ
.
reaction of InCl3ꢀ3H2O and NaSC6H4Me-p in the presence of
[Et4N]ClꢀxH2O. The analogous selenolate derivative of gallium
[Et4N][Ga(SePh)4] (3) was prepared from similar reaction of
[Et4N][GaCl4] with four equivalents of NaSePh. White crystalline
thiolate and selenolate complexes [M(SR)4]ꢁ (M = Ga, In) were sta-
ble in both solid-state and solution. Both complexes were soluble
in DMSO and DMF, and slight soluble THF and MeCN, but poorly
soluble in common solvents. The infrared spectra of complexes 1
and 2 display the characteristic C–S stretching vibration of the
coordinated thiolate ligands at 648 and 641 cmꢁ1. The C–Se
stretching vibration at 562 cmꢁ1 in the IR spectrum indicated the
presence of selenolate ligands in complex 3. The 1H NMR spectra
of three complexes display the typical multiple peaks in the ranges
d 6.70–7.40 ppm, which were assigned to the protons of the phenyl
moiety. The molecular ions corresponding to [Ga(SC6H4Me-p)4]ꢁ,
[In(SC6H4Me-p)4]ꢁ and [Ga(SePh)4]ꢁ can be observed at m/z 562,
607 and 694 in the mass spectra of 1, 2 and 3, with their character-
istic isotopic distribution patterns.
a week. Yield: 297 mg, 63%. IR (KBr, cmꢁ1): (C–Se) 562 (m). 1H
m
NMR (DMSO-d6, ppm): d 1.03 (s, 12H, CH3 in Et4N), 2.94 (t, 8H,
CH2 in Et4N), 6.91–7.35 (m, 20H, Ph). MS (FAB): m/z 694
(M+ꢁ[Et4N]). Anal. Calcd. for C32H40NSe4Ga: C, 46.6; H, 4.89; N,
1.70. Found: C, 46.2; H, 4.85; N, 1.66%.
2.5. X-ray crystallographic study
The structures of [Et4N][Ga(SC6H4Me-p)4] (1), [Et4N][In(SC6H4Me-
p)4] (2), and [Et4N][Ga(SePh)4] (3) were determined by the single-
crystal X-ray diffraction technique. Diffraction data were collected
on a Bruker SMART Apex CCD diffractometer with Mo-K
a radiation
(k = 0.71073 Å) at 296 K using an scan mode. The collected frames
x
Crystal structures of 1, 2, and 3 have been determined by X-ray
diffraction study. All crystal structures consist of discrete [Et4N]+
cations and its corresponding complex anions. In all structures,
the [Et4N]+ cations exhibit normal bond distances and angles. The
were processed with the software Saint [16]. The data was corrected
for absorption using the program Sadabs [17]. Structures were solved
byDirectMethodsandrefinedbyfull-matrixleast-squaresonF2 using
the Shelxtl software package [18]. All non-hydrogen atoms were re-
finedanisotropically.The positionsof all hydrogen atoms were gener-
ated geometrically (Csp3–H = 0.96, Csp2–H = 0.93 Å) and included in
the structure factorcalculationswithassignedisotropicdisplacement
parameters but were not refined. The Flack parameter values of 1 and
2 indicate that the correct enantiomorphs have been selected in both
structures. Further details of the data determination, crystal data and
structure refinement parameters are summarized in Table 1.
structures of the anions, [Ga(SC6H4Me-p)4]ꢁ in
1 and [In(-
SC6H4Me-p)4]ꢁ in 2, are shown in Figs. 1 and 2, respectively. The
anions in 1 and 2 have a distorted tetrahedral geometry which
were similar to those the gallium-thiolate anions [i-Pr4N][Ga(SEt)4]
[12], and [Et4N][Ga(SPh)4] [12] and indium-thiolate anions
[Ph4P][In(S-t-Bu)4] [19] and [Me4N][In(SC6H3Me2-2,6)4] [20]. The
Ga–S bond lengths in 1 range from 2.254(2) to 2.291(2) Å (av.
2.273(2) Å), which are in good agreement with those in [(i-
Pr)2NH2][Ga(S-i-Pr)4] (av. 2.2678(6) Å) [13], [i-Pr4N][Ga(SEt)4] (av.
2.264(3) Å) [12], and [Et4N][Ga(SPh)4] (av. 2.257(3) Å) [12]. The
S–Ga–S bond angles in 1 vary from 97.06(7) to 117.31(9)°, which
were expected for distorted tetrahedral coordination environment,
which are comparable to those in [(i-Pr)2NH2][Ga(S-i-Pr)4] (from
97.10(2) to 118.22(2)°) [13] and [Et4N][Ga(S-Ph)4] (from 101.6(1)
to 114.2(1)°) [12]. Similarly, the In –S bond lengths in 2 range from
3. Results and discussion
Treatment of [Et4N][GaCl4] with four equivalents of
NaSC6H4Me-p in methanol afforded the substitution complex
[Et4N][Ga(SC6H4Me-p)4] (1) in a yield of 87%. The indium ana-
logues [Et4N][In(SC6H4Me-p)4] (2) was prepared similarly by the

Y.-G. Han et al. / Journal of Molecular Structure 936 (2009) 15–18
17
Fig. 3. View of the [Ga(SePh)4]ꢁ anion in 3 showing the atom numbering scheme.
Thermal ellipsoids are 40% equiprobability envelops, with hydrogen atoms omitted.
Selected bond lengths (Å) and angles (°): Ga(1)–Se(1) 2.4052(4), Ga(1)–Se(2)
2.4069(4), Ga(1)–Se(3) 2.4013(4), Ga(1)–Se(4) 2.3963(4); Se(1)–Ga(1)–Se(2)
106.126(15), Se(3)–Ga(1)–Se(1) 111.855(15), Se(3)–Ga(1)–Se(2) 110.610(14),
Se(4)–Ga(1)–Se(3) 106.221(15), Se(4)–Ga(1)–Se(1) 109.127(14), Se(4)–Ga(1)–
Se(2) 112.992(15).
Fig. 1. View of the [Ga(SC6H4Me-p)4]ꢁ anion in 1 showing the atom numbering
scheme. Thermal ellipsoids are 40% equiprobability envelops, with hydrogen atoms
omitted. Selected bond lengths (Å) and angles (°): Ga(1)–S(1) 2.262(2), Ga(1)–S(2)
2.2544(18), Ga(1)–S(3) 2.2830(17), Ga(1)–S(4) 2.2913(17); S(2)–Ga(1)–S(1)
117.31(9), S(2)–Ga(1)–S(3) 115.65(8), S(1)–Ga(1)–S(3) 97.06(7), S(2)–Ga(1)–S(4)
98.84(7), S(1)–Ga(1)–S(4) 113.15(8), S(3)–Ga(1)–S(4) 115.95(7).
are probably due to the steric crowding of the bulky phenyl rings.
The Ga–Se bond lengths ranging from 2.3963(4) to 2.4069(4) Å (av.
2.4024(4) Å) in
Ph2)2N}2][GaCl4] (av. 2.4059(8) Å) [21], but slightly shorter that
those in [Ga(Se2PiPr2)2( -Se2PiPr2)2] (av. 2.4200(4) Å) with chelat-
ing GaSe2 bite angle [22].
3 are comparable with those in [Ga{(SeP-
g
In order to examine the thermal stability of the homolepic com-
plexes, thermal gravimetric analyses (TGA) were carried out be-
tween 30 and 600 °C in static atmosphere of air. Complexes 1
and 2 were stable at 148 °C. Further increasing in temperature
caused decomposition of the complexes. The loss of the organic
cations occurred simultaneously. For 1, a single-step weight loss
was observed between 155 and 325 °C, which is attributed to the
release of the thiolate ligands and leaving Ga2S3 as a yellow pow-
der (observed 16.8%, calculated 17.0%). The decomposition temper-
ature of 2 is almost the same as that of 1. A weight loss of 49.8%
(calculated 51.0%) was observed from 160 to 315 °C corresponding
to the loss of one organic cation and two p-MeC6H4Sꢁ ligands per
formula unit. Further weight loss was observed at 320 °C, and
the remaining yellow powdery product was In2S3 (observed
22.2%, calculated 22.1%). The selenolate complex 3 lost ca. 77% of
its mass from 175 to 330 °C, leaving yellow powder residue which
was microanalyzed to show an average ratio of Ga:Se of 2:3. The
three homoleptic complexes proved to be potentially a single-
source precursor for nano-crystalline gallium(indium)–sulfur(sele-
nium) materials [23]. Further study of this aspect will be carried
out.
Fig. 2. View of the [In(SC6H4Me-p)4]ꢁ anion in 2 showing the atom numbering
scheme. Thermal ellipsoids are 40% equiprobability envelops, with hydrogen atoms
omitted. Selected bond lengths (Å) and angles (°): In(1)–S(1) 2.4593(9), In(1)–S(2)
2.4536(9), In(1)–S(3) 2.4484(10), In(1)–S(4) 2.4445(12); S(2)–In(1)–S(1) 116.12(4),
S(3)–In(1)–S(1) 100.51(3), S(4)–In(1)–S(1) 111.95(4), S(3)–In(1)–S(2) 113.95(4),
S(4)–In(1)–S(3) 116.75(5), S(4)–In(1)–S(2) 98.44(3).
2.446(1) to 2.459(1) Å and the S–In–S bond angles in 2 vary from
98.44(3) to 116.12(4)°, which are compared with those in the re-
lated tetrahedral [In(SR)4]ꢁ complexes such as [Ph4P][In(S-t-Bu)4]
(In–S 2.451(3)–2.489(3) Å and S–In–S 103.8(1)–114.6(1)°) [19]
and [Me4N][In(SC6H3Me2-2,6)4] (In–S 2.450(2)–2.473(2) Å and S–
In–S 107.34(4)–111.49(4)°) [20].
4. Supplementary material
The structure of the anion, [Ga(SePh)4]ꢁ, of 3 is shown in Fig. 3.
The [Ga(SePh)4]ꢁ anion is isostructural to the indium analogue
[In(SePh)4]ꢁ. Examples of the homoleptic gallium-selenolate com-
plexes with tetrahedral coordination geometry are [Ga{(SeP-
Crystal data (excluding structure factors) for the structure anal-
yses have been deposited with the Cambridge Crystallographic
Data Centre as supplementary publication numbers CCDC-
738145 (1), CCDC-731846 (2) and CCDC-731847 (3). These data
can be obtained free of charge via www.ccdc.cam.ac.uk/conts/
retrieving.html (or from the Cambridge Crystallographic Data Cen-
tre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-
033; or deposit@ccdc.cam.ac.uk).
Ph2)2N}2][GaCl4] [21] and [Ga(Se2PiPr2)2( -Se2PiPr2)2] [22]. The
g
gallium(III) center is tetrahedrally coordinated to four PhSeꢁ li-
gands. The Se–Ga–Se bond angles in 3 are in the range of
106.22(2)–112.99(2)°, slightly distorted from tetrahedral which

18
Y.-G. Han et al. / Journal of Molecular Structure 936 (2009) 15–18
[8] P. Vaqueiro, J. Solid State. Chem. 179 (2006) 302.
Acknowledgements
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This project was supported by the Natural Science Foundation
of China (20871002) and National Basic Research Program of China
(973 Program, 2008CB617605). Q.-F. Zhang thanks the Program for
New Century Excellent Talents in University of China (NCET-06-
0556) for the assistance.
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