Silylated gallium and indium chalcogenide ring systems as potential precursors to ME (E=O, S) materials

Article abstract of DOI:10.2478/s11532-013-0255-y

The reaction of R₃M (M=Ga, In) with HESiR′₃ (E=O, S; R′₃=Ph₃, ⁱPr₃, Et₃, ^tBuMe₂) leads to the formation of (Me ₂GaOSiPh₃)₂ (1); (Me₂GaOSi ^tBuMe₂)₂ (2); (Me₂GaOSiEt ₃)₂ (3); (Me₂InOSiPh₃)₂ (4); (Me₂InOSi^tBuMe₂)₂ (5); (Me ₂InOSiEt₃)₂ (6); (Me₂GaSSiPh ₃)₂ (7); (Et₂GaSSiPh₃)₂ (8); (Me₂GaSSiⁱPr₃)₂ (9); (Et ₂GaSSiⁱPr₃)₂ (10); (Me ₂InSSiPh₃)₃ (11); (Me₂InSSi ⁱPr₃)_n (12), in high yields at room temperature. The compounds have been characterized by multinuclear NMR and in most cases by X-ray crystallography. The molecular structures of (1), (4), (7) and (8) have been determined. Compounds (3), (6) and (10) are liquids at room temperature. In the solid state, (1), (4), (7) and (9) are dimers with central core of the dimer being composed of a M₂E₂ four-membered ring. VT-NMR studies of (7) show facile redistribution between four- and six-membered rings in solution. The thermal decomposition of (1)-(12) was examined by TGA and range from 200 to 350 C. Bulk pyrolysis of (1) and (2) led to the formation of Ga₂O₃; (4) and (5) In metal; (7)-(10) GaS and (11)-(12) InS powders, respectively. [Figure not available: see fulltext.]

Full text of DOI:10.2478/s11532-013-0255-y

Cent. Eur. J. Chem. • 11(7) • 2013 • 1225-1238
DOI: 10.2478/s11532-013-0255-y
Central European Journal of Chemistry
Silylated gallium and indium chalcogenide
ring systems as potential precursors
to ME (E=O, S) materials
Research Article
Iliana E. Medina-Ramírez†, Cynthia Floyd,
Joel T. Mague, Mark J. Fink*
Department of Chemistry, Tulane University,
6823 Saint Charles Avenue,
New Orleans, LA 70118, USA
Received 22 December 2012; Accepted 15 March 2013
i
t
Abstract:
The reaction of R3M (M=Ga, In) with HESiR’3 (E=O, S; R’3=Ph3, Pr3, Et3, BuMe2) leads to the formation of (Me2GaOSiPh3)2 (1);
(Me2GaOSitBuMe2)2 (2); (Me2GaOSiEt3)2 (3); (Me2InOSiPh3)2 (4); (Me2InOSitBuMe2)2 (5); (Me2InOSiEt3)2 (6); (Me2GaSSiPh3)2
(7); (Et2GaSSiPh3)2 (8); (Me2GaSSiiPr3)2 (9); (Et2GaSSiiPr3)2 (10); (Me2InSSiPh3)3 (11); (Me2InSSiiPr3)n (12), in high yields at room
temperature. The compounds have been characterized by multinuclear NMR and in most cases by X-ray crystallography. The molecular
structures of (1), (4), (7) and (8) have been determined. Compounds (3), (6) and (10) are liquids at room temperature. In the solid state,
(1), (4), (7) and (9) are dimers with central core of the dimer being composed of a M2E2 four-membered ring. VT-NMR studies of (7)
show facile redistribution between four- and six-membered rings in solution. The thermal decomposition of (1)-(12) was examined by
TGA and range from 200 to 350oC. Bulk pyrolysis of (1) and (2) led to the formation of Ga2O3; (4) and (5) In metal; (7)-(10) GaS and
(11)-(12) InS powders, respectively.
Keywords: Group 13-16 precursors • Single source precursors • X-ray crystallography • TGA
© Versita Sp. z o.o.
presentedareviewfocusedonrecentdevelopmentsofthe
chemistry of metal thio and selenocarboxylates, in order
1. Introduction
Chemical investigations of compounds that contain a to remark the potential use of some of these compounds
combination of group 13-16 elements have recently as SSPs for making metal sulfide and selenide bulk
undergone resurgence due in part to their potential as materials, thin films, and nanoparticles [2]. Despite the
precursors to III-VI materials.The synthesis of compounds numerous advantages offered by SSPs, better synthetic
that may be used as precursors for the formation of such and reproducible methods have to be investigated for
materials by chemical vapor deposition (CVD) attracts controlled morphologies and stoichiometries before their
a great deal of time and effort. The preparation of III- exploitation in photovoltaic devices is possible.
VI semiconductor films has been successful due to the
Research in recent years has been focused on
use of ‘single-source precursors’ (SSPs). SSPs contain producing precursors that are safe to handle, yet are
all the desired elements in a single molecule. These volatile enough and reactive enough to decompose at
compounds have attracted much research interest low temperature [3]. Compounds that have direct M-E
due to the fact that this approach has the potential to bonds can be prepared in several ways. The chemistry of
control the film stoichiometry, to simplify the precursor new precursors is based on the fact that group 13 metal
delivery, and to gain better film homogeneity. SSPs are alkyls and halides act as strong Lewis acids, and hence
promising candidates for the production of thin films and readily complex to electron rich chalcogen-containing
nanoparticles with photovoltaic applications [1]. Vittal et al. ligands.
* E-mail: fink@tulane.edu
†Current address: Departamento de Química, Universidad Autónoma de Aguascalientes,
Avenida Universidad 940, Ciudad Universitaria, Aguascalientes 20131, Mexico
1225

Silylated gallium and indium chalcogenide ring
systems as potential precursors to ME (E=O, S) materials
A number of early reports described the synthesis of silyl derivatives facilitates the alkane elimination
and the chemical and physical properties of these reaction to form the corresponding metal-chalcogen
compounds. These reports provide details on several organometallic derivatives. Second, the identity of R
methods for the synthesis of such compounds and some in (HXSiR’3) may be readily varied to alter the physical
studies on the chemical reactivity but little information properties of the precursors. Third, the decomposition
on their structures, behavior in solution, or deposition. (elimination-condensation chemistry) of silanethiolato
In 1995, Oliver et al. started a systematic study about precursors occurs with lower activation barriers
the solid-state structures and the aggregation states of (e.g. dehalosilylation, dehydrosilylation) during their
these derivatives in solution [4].
conversion to semiconducting group III-VI materials. All
A number of group 13 oxide and chalcogenide these factors strongly motivate us into the research of
complexes have been developed as reliable sources these precursors.
for the deposition of group 13 oxides and chalcogenide
Here, we report on the synthesis, characterization
films. The list includes metal alkoxide complexes [5], and thermal decomposition of (R2MESiR’3)n complexes.
alkyl metal β-diketonates [6], alkyl metal chalcogenates
[7–9], monothiocarbamates [10], monothiocarboxylates
2. Experimental procedure
[11], dialkyldithio- and dialkyldiselenocarbamates
[12,13]
and
dialkyldiselenophosphinatocomplexes
[14]. The combination of In(Se2CNMenHex)3 and 2.1. General procedures
Cu(Se2CNMenHex)2 has led to the production of ternary All the reactions were undertaken under dry, oxygen-free
semiconducting materials such as CuInSe2 [12,13].
argonusingavacuumlineandstandardinert-atmosphere
Reports on compounds based on silicon-containing techniques [28].All of the glassware used in the synthetic
ligands are very scarce. It was in 1971 that Charov et al. work was oven dried at 140oC. Hexane, pentane, THF,
[15] first reported the use of silicon-containing ligands to diethyl ether, C6H6, C7H8, C6D6 and C7D8 were dried with
prepare group 13-16 organometallic complexes. More Na/benzophenone under nitrogen, and distilled prior
recent reports include the use of these silicon-containing to use. CH2Cl2 and CD2Cl2 were dried with CaH2 under
ligands as precursors to group 13-15 materials. nitrogen, and distilled prior to use. Trimethylgallium,
Numerous reports from Wells et al. clearly demonstrate triethylgallium and trimethylindium were purchased
the advantages in the use of silylated compounds as from Strem and used without purification. HSSiPh3,
precursor materials [16–18]. Deposition of GaAs, HSSiiPr3 were purchased from Aldrich and used without
GaP, and GaSb at low temperatures were possible purification. 1H, 13C and 29Si, NMR spectra were recorded
with the use of these precursors. Some silylamido and on either a Varian Inova 400 MHz or a Bruker 300 MHz
silylphosphanylcomplexesofgalliumhavebeenreported at ambient temperature. Variable temperature NMR (VT-
recently [19,20]. Recent efforts in this area have led to NMR) experiments were calibrated with methanol. VT-
the isolation and structural characterization of numerous NMR was performed with a computer-controlled variable
trimethylsilyl chalcogenolates metal (Cu [21], Ag [22], Zn temperature accessory. Solvent peaks were used to set
[23], Fe [24]) complexes that present unique chemical 1H and 13C chemical shifts, and external TMS was used
properties. These compounds have been shown to be to set 29Si shifts. Mass spectral data were collected by
valuable in the formation of structurally characterized Georgia Institute of Technology. Elemental analysis was
nanoclusters and nanoparticles. It has been recently performed by Schwarzkopf Microanalytical Lab. Melting
been shown that the chemistry of silylated metal points are uncorrected.
compounds can be exploited on a modified mesoporous
surface to form binary ME (M=Cd, Zn; E=S,Se,Te) and 2.2. X-ray structure determination
ternary CdxZn1-xE (E=S,Se) nanomaterials within the The crystals were mounted in a CryoloopTM with a drop
host framework [25,26].
of Paratone oil and placed in the cold nitrogen stream
In our group, there is a keen interest on siloxides of the KryoflexTM attachment of the Bruker APEX CCD
and silanechalcogenolato derivatives of the group 13 diffractometer. Diffraction data were collected on a
metals, as molecular precursors for III-VI materials. The Siemens SMART CCD area detector diffractometer
rationale for employing silicon-based ligands is multiple. (graphite monochromator, Mo-Kα, λ=0,7107 Å, ω-scans,
First, the E−H (E=O, S) hydrogen in silyl derivatives T=173 K) using the SMART software [29]. Data reduction
reacts rapidly at room temperature with trialkyl metal andfinalunitcellrefinementswerecarriedoutwithSAINT+
derivatives. Arnold et al. demonstrated that silyl thiol, [30]. The program SADABS [31] was used to perform
silyl selenol and silyl tellurol are 100 times more acidic combined area detector scaling an empirical absorption
than their alkyl counterparts [27]. The increased acidity correction based on equivalent reflections. The structures
1226

I. E. Medina-Ramírez et al.
were solved using direct methods and difference Fourier 3030(m), 2965(s), 2916(w), 1965(w), 1894(w),1824(w),
techniques, and were refined against F2 data using the 1590(m), 1491(m), 1427(s), 1206(m), 1117(s), 1000(w),
SHELXTL [32,33]. All non-hydrogen atoms were refined 843(s), 746(s), 700(s), 597(m), 547(s), 509(s). Anal.
anisotropically. Hydrogen atoms were added inidealized Calcd forC40H42Si2O2Ga2: C: 64.03%;H: 5.64%. Found:
positions with fixed isotropic temperature factors.
C: 64.12%;H: 5.64%.
(Me2GaOSiMe2tBu)2 (2) Trimethylgallium,1.0 mL
(10mmol), in 10 mL of benzene was added dropwise
2.3. Thermal analysis
Thermogravimetric analyses were performed on a TA via an addition funnel to a solution of dimethyl-tert-
Instruments 2950 HR TGA. Argon carrier gas at a flow butylsilanol, 1.6 mL (10 mmol), in 15 mL of benzene.
rate of 40 cc min-1 was used unless otherwise indicated. After stirring for several hours, the benzene was
Samples of thephenyl derivatives were quickly loaded distilled off and thick oil was left behind. After being put
into a platinum pan under argon flow and heated at 10oC under vacuum for several hours, a white solid was left,
min-1 from 30 to 1000oC. In the case of the more volatile 1.58 g, 68%, mp 45oC. The solid was further purified
and reactive samples, compounds (2), (5), (8), (9) and by vacuum sublimation from the melt, 47oC per 0.04
(12) were loaded into aluminum pans in a nitrogen- mmHg. 1H NMR (C6D6, δ, ppm): 0.84(s, 9H, tBu) 0.02(s,
filled MBraun dry box. An aluminum lid with a pinhole 6H, SiCH3) -0.01(s, 6H, GaCH3); 13C{1H}: (C6D6, δ, ppm):
was crimped to the pan in the dry box and the whole 25.76(CCH3), 18.31(CCH3), -2.15(GaC), -2.47 (SiC);
assembly containing the sample was placed in a sample 29Si{1H}: (C6D6, δ, ppm): 22.95; IR (cm-1, KBr pellet)
vial. The vial containing the pan assembly was quickly 2957(s), 2860(m), 1471(m), 1420(w), 1260(m),1200(m),
taken to the TGA where the pan assembly was removed 980(w), 841(s), 780(m), 750(m), 670(m), 600(m), 503(s).
from the vial and placed on the TGA pan under an argon Anal. Calcd for C16H42Si2O2Ga2: C: 41.59%; H: 9.16%.
flow at 10oC min-1 from 30 to 500oC. The TGA balance Found: C: 41.37%; H: 8.94%.
was previously tared with an empty aluminum pan and
(Me2GaOSiEt3)2 (3) Triethylsilanol, 1.6 mL
lid assembly. Melting points were measured in sealed (10 mmol), was dissolved in 20 mL benzene in a 100 mL
tubes with an electrothermal melting point apparatus. Schlenk flask. Trimethylgallium, 1.0 mL (10 mmol), in
X-ray powder diffraction studies were carried out by a 15 mLbenzene was subsequently added dropwise to the
Scintag XDS 2000 diffractometer using monochromated silanol solution with stirring. The reaction mixture was
CuKα radiation, excited at 43 kV and 38 mA. The allowed to stir several hours to ensure complete reaction.
samples were mounted flat and scanned from 6 to 64o The benzene was then distilled off and the remaining
in a step size of 0.02o with a count rate of 1.2 seconds. liquid put under vacuum and Kugelrohr distilled. The
Pyrolysis experiments were performed by placing the colorless product was isolated at 85oC per 0.05mmHg,
1
sample in an evacuated flame sealed ampoule and 2.10 g, 91% yield. H NMR (C6D6, δ, ppm): 0.89(t, 9H,
heating the ampoule to 400oC for 1 h in a muffle furnace. CH2CH3) 0.50 (q, 6H, CH2) -.06 (s, 6H, GaCH3); 13C{1H}:
Gallium oxide powders were placed in a quartz crucible (C6D6, δ, ppm): 6.65 (CH2CH3), 6.40(CH2), -3.01(GaC);
annealed at 1000oC for 1 h in a muffle furnace.
29Si{1H}: (C6D6, δ, ppm): 22.78; IR (cm-1, neat on KBr
(Me2GaOSiPh3)2 (1) Trimethylgallium, 1.0 mL plates) 2957(s), 2913(m), 2880(s), 1458(w), 1414(w),
(10 mmol), in 10 mL benzene was dropwise added to 1240(m), 1206(m), 1004(m), 970(w), 841(s), 743(s),
triphenylsilanol, 2.7458 g (9.9 mmol), in 35 mL benzene 590(m), 513(s); MS(EI) M+ -15 calc. 445.1000244, found
in a 100 mL Schlenk flask. After stirring for several 445. 099976. Anal. Calcd for C16H42Si2O2Ga2: C: 41.59%
hours, the benzene was removed under vacuum until H: 9.16%. Found: C: 41.58%; H: 9.34%.
the volume was around 10 mL. Approximately 7 mL
(Me2InOSiPh3)2 (4)Trimethylindium, 1.6 g (10 mmol),
of hexane were added until seed crystals formed. The in 10 mL of benzene was added dropwise to a solution of
mixture was put into the refrigerator for 12 hours at a triphenylsilanol,2.7458g(9.9mmol),in30mLofbenzene
temperature of 0oC, in order to complete crystallization. contained in a 100 mL Schlenk flask. After stirring for
The crystals were filtered under argon and washed with several hours, the benzene was removed under vacuum
cold hexane. A white solid, 2.84 g, 77%, mp 165oC, was until the volume was around 10 mL. Approximately 7 mL
isolated. Several milligrams of solid were dissolved of hexane were added until seed crystals formed. The
in benzene and allowed to vapor diffuse with hexane mixture was put into the refrigerator for 12 hours at a
over several days to grow a crystal suitable for X-ray temperature of 0oC, in order to complete crystallization.
1
analysis. H NMR (C6D6, δ, ppm): 7.74 (m, 6H, Ph), The product precipitated from the reaction mixture and
7.13(m, 9H, Ph), -0.21(s, 6H, CH3); 13C{1H}: (C6D6, δ, was recrystallized from benzene/hexane. Yield: 75%,
ppm): 135.81, 135.16, 130.15, 127.85, -1.76; 29Si{1H}: 3.2 g. mp: 167oC. Several milligrams of solid were
(C6D6, δ, ppm): -8.04; IR (cm-1, KBr pellet) 3069(s), dissolved in benzene and allowed to vapor diffuse with
1227

Silylated gallium and indium chalcogenide ring
systems as potential precursors to ME (E=O, S) materials
hexane over several days to grow a crystal suitable for
(Et2GaSSiPh3)2 (8) Triethylgallium, 1.1 mL
X-rayanalysis.Anal. CalcdforC40H42Si2O2In2:C:57.15%; (10 mmol) in 10 mL of toluene was dropwise added to
H: 5.03% Found: C: 57.06%; H: 4.95%. 1H NMR (C6D6): a solution of triphenylsilanethiol, 2.928 g (9.9mmol), in
0.0 (s, In−CH3), 7.3 (m, 9H), 7.9 (m, 6H). 13C{1H}: NMR 30 mL of toluene contained in a 100 mL Schlenk flask.
(C6D6, δ, ppm): 0.0 (In(CH3)2), 131.7 (aryl), 137.2 (aryl), After stirring for several hours, the toluene was removed
138.8 (aryl). 29Si{1H}: NMR (C6D6, δ, ppm): -14.5.
(Me2InOSiMe2tBu)2 (5) Trimethylindium, 1.6
under vacuum until the volume was around 15 mL.
The flask was put in the refrigerator for 12 hours at a
g
(10 mmol), was dissolved in 20 mL benzene in a temperature of 0oC. The product precipitated from the
100 mL Schlenk flask. Dimethyl-tert-butylsilanol, 1.6 mL reaction mixture and was recrystallized from toluene/
1
(10 mmol), in 10 mL of benzene was added dropwise hexane. Yield: 70%. H NMR (C7D8, δ, ppm): 1.07 (t,
to the indium solution with stirring. The reaction mixture CH2CH3, 6H), 0.654 (quart, CH2CH3, 4H), JHH=6.6Hz;
was allowed to stir for 12 hours to make sure reaction 7.92 (o, 6H), 7.7 (m, 6H), 7.75 (p, 3H). 13C{1H}: NMR
was complete. Benzene was removed under vacuum (C6D6, δ, ppm): 11.02 (CH2CH3), 10.1 (CH2CH3), 136
until the volume was around 10 mL. Approximately 20 (aryl), 135.62 (aryl), 135 (aryl), 130.3 (aryl). 29Si{1H}
mL of pentane were added and the solution was cooled NMR: (C6D6, δ, ppm): -2.35.
to 0oC. A white solid, 2.6 g, 93%, mp 45oC, was isolated.
(Me2GaSSiiPr3)2 (9) Trimethylgallium, 1.0 mL
1H NMR (C6D6, δ, ppm): 0.13(s, In−CH3), 0.21 (s, (10 mmol), in 10 mL pentane was dropwise added to a
Si−CH3), 1.0 (s, Si−tBu). 13C{1H}: NMR (C6D6, δ, ppm): solution of triisopropylsilanethiol, 2.16 mL (9.9 mmol),
-2.1 (In(CH3)2), -1.7 (Si−(CH3)2), 18.5 (Si−C(CH3)3), 26.1 in 25 mL of pentane contained in a 100 mL Schlenk
(Si−C(CH3)3). 29Si{1H}: NMR (C6D6, δ, ppm): 15.5.
flask. After stirring for several hours, the pentane was
(Me2InOSiEt3)2 (6) Trimethylindium, 1.6 g (10 mmol), removed under vacuum until the volume was around
was dissolved in 29 mL benzene in a 100 mL Schlenk 15 mL. Product precipitated from solution at -40oC. Yield:
flask. Triethylsilanol, 1.6 mL (10 mmol), in 10 mL of 65%. 1H NMR (C6D6, δ, ppm): 0.0 (s, GaCH3, 6H), 0.97
benzene was added dropwise to the indium solution (d, CH(CH3)2, 18H), 1.11 (sept., CH(CH3)2, 3H): 13C{1H}:
with stirring. The reaction mixture was allowed to stir NMR(C6D6, δ, ppm): 1.0 (GaCH3), 21.6 (CH(CH3)2),
several hours to make sure reaction was complete. 14.07 (CH(CH3)2). 29Si{1H}: NMR(C6D6, δ, ppm):
Benzene was removed under vacuum. Pentane was 30.64.
added and the solution was cooled to -70oC to isolate the
(Et2GaSSiiPr3)2 (10) Triethylgallium, 1.1 mL
product. The product was washed with pentane several (10 mmol), in 10 mL of pentane was dropwise added to a
times at -70oC and pumped under vacuum to remove solution of triisopropylsilanethiol, 2.16 mL (9.9 mmol), in
solvent. Isolation and purification were difficult and total 25 mL of pentane contained in a 100 mL Schlenk flask.
exclusion of solvent was not possible. 1H NMR (δ, ppm): Pentanewasremovedbydistillation.Theviscousproduct
0.85 (t, CH2CH3), 0.37 (q, CH2CH3), -0.019 (s, InCH3); was purified by first washing with pentane at -70oC and
13C{1H}: 6.985 (CH2CH3), 6.711 (CH2CH3), -3.067 (InC); then by vacuum distillation, oil bath at 70oC; boiling
1
29Si{1H}: -21.971.
point 75oC (< 10−3 mmHg). Yield: 70%. H NMR (C6D6,
(Me2GaSSiPh3)2 (7) Trimethylgallium, 1.0mL δ, ppm): 0.8 (unresolved multiplet), 1.0 (d, CH(CH3)2),
(10mmol), in 10mL toluene was dropwise added to a 1.3 (m, CH(CH3)2): 13C{1H}: NMR (C6D6, δ, ppm): 10.2
solution of triphenylsilanethiol, 2.928 g (9.9mmol), in (GaCH2CH3), 11.7 (GaCH2CH3), 22.5 (CH(CH3)2), 14.39
30 mL of toluene contained in a 100 mL Schlenk flask. (CH(CH3)2). 29Si{1H} NMR(C6D6, δ, ppm): 30.37.
After stirring for several hours, the toluene was removed
(Me2InSSiPh3)3 (11) Trimethylindium, 1.6
g
under vacuum until the volume was around 15mL. (10 mmol), in 1 mL benzene was dropwise added to
The flask was put in the refrigerator for 12 hours at a a solution of triphenysilanethiol, 2.928 g (9.9 mmol),
temperature of 0oC. The product precipitated from the in 30 mL of benzene contained in a 100 mL Schlenk
reaction mixture and was recrystallized from toluene/ flask. After stirring for several hours, the benzene was
hexane. Yield: 95%. Several milligrams of solid were removed under vacuum until the volume was around
dissolved in toluene and allowed to vapor diffuse with 15 mL. The flask was put in the refrigerator for 12 hours at
hexane over several days to grow a crystal suitable a temperature of 0oC. The product precipitated from the
for X-ray analysis. Anal. Calcd for C40H42Si2S2Ga2: C: reaction mixture and was recrystallized from benzene/
1
61.4%; H: 5.41%. Found: C: 60.6%; H: 5.51%. 1H NMR hexane. Yield: 91%, 3.7g. H NMR (C6D6, δ, ppm): 0.0
(C7D8, δ, ppm): 0.0 (s, Ga−CH3, 7.94 (o, 6H), 7.72 (m, (s, InCH3, 6H), 7.2 (m, 9H), 7.9 (m, 6H). 13C{1H} NMR
6H), 7.77 (p, 3H). 13C{1H}: NMR (C6D6, δ, ppm): 1.21 (C6D6, δ, ppm): 11.02 (CH2CH3), 10.1 (CH2CH3), 136
(Ga(CH3)2), 136.03 (aryl), 135.62 (aryl), 134.7 (aryl), (aryl), 135.62 (aryl), 135 (aryl), 130.3 (aryl). 29Si{1H}
130.4 (aryl) . 29Si{1H}: NMR (C6D6, δ, ppm): -2.44.
NMR(C6D6, δ, ppm): -2.35.
1228

I. E. Medina-Ramírez et al.
(Me2InSSiiPr3)n
(12)
Triisopropylsilanethiol,
Compounds (1), (2), (4), (5), (7), (8), (9), (11) and
1.073 mL, (5 mmol), in 10 mL of pentane was dropwise (12) have been isolated as colorless, transparent
added to a solution of trimethylindium, 0.8 g (5mmol), in crystals that are both air- and moisture-sensitive. They
15 mL of pentane contained in a 50 mL Schlenk flask, are soluble in hydrocarbon solvents such as benzene,
at 0oC. Pentane was removed under vacuum. Product and toluene, and in the donor solvents such as diethyl
was purified by recrystallization in pentane at -30oC. ether and tetrahydrofuran. Compound (3) is a colorless
mp. 45oC.Yield: 78%, 1.3 g. 1H NMR (CD2Cl2, δ, ppm): liquid. The liquid triethylsiloxy gallium compound
0.183 (s, methyl region), 1.106 (d, CH(CH3)2), 1.205 decomposes in the open atmosphere to an insoluble
(sept., CH(CH3)2). 13C{1H}: NMR (CD2Cl2, δ, ppm) -0.144 white solid over several minutes, while compounds (1)
(InCH3), 14.216. 29Si{1H} NMR (CD2Cl2, δ, ppm): 29.02. and (2) decompose more slowly to white insoluble solids.
Anal. Calcd for C22H54InS2Si2: C: 39.52%; H: 8.14%. Compound (6) is a dense white liquid that is difficult to
Found: C: 39.15%; H:8.03%.
isolate and purify. Compound (9) decomposes over a
period of few minutes in the solid state on exposure to
air. Compound (10) is a colorless liquid. Physical and
spectroscopic properties of (1)-(12) are summarized in
Table 1.
3. Results and discussion
The melting point of these complexes shows the role
of the organic ligands in the modification of their physical
properties. An increase in the alkyl chain attached to
the metal lowers the melting point; the silyl substituent
potentially adds a unique degree of high volatility and
hydrocarbon solubility to the molecule. General 1H, 13C,
and 29Si NMR parameters for the individual compounds
are listed in the experimental section. The 1H NMR shifts
for the methyl gallium groups and the methyl indium
groups are in agreement with other related compounds
[3,34]. The room temperature 1H NMR spectra indicate
a highly symmetric structure, with only one set of peaks
for the siloxy substituents and singlets for the methyl
groups bonded to the metal.
3.1. Gallium and indium siloxides
The silanols (HOSiR’3; R’=Ph, Et, R’3= Me2tBu,Et) and
the silanethiols (HSSiR3; R’=Ph, iPr) react rapidly at room
temperature with trialkylgallium (Me, Et) and trimethyl
indium compounds in a 1:1 stoichiometry, liberating the
alkane and affording the corresponding siloxides and
silanethiolato complexes of gallium and indium, in high
yield according to the general reaction scheme of the
following equation:
R3M+HESiR’3 → (1/n)(R2MESiR’3)n+ RH
M=Ga,In; E=O,S
1: M=Ga; R=Me; R’=Ph; yield: 77%
Crystals of (1) and (4) were grown from a benzene/
hexane (1:1) solution at 0oC. Parameters from the crystal
structure determination of (1) and (4) are presented
in Table 2. Compounds (1) and (4) are dimeric in the
solid state with planar M2O2 rings. An ORTEP diagram
of the molecular unit for (1) is shown in Fig. 1, and the
molecular unit for (4) is shown in Fig. 2. Both crystals
are triclinic and belong to the space group P-1. As with
most other group 13-oxygen four-membered rings;
[Ga(µ−OCMe2Et)(OCMe2Et)2]2 [2], [Me2In(acac)]2 [5],
[In(µ−OR)(OR)2]2 [4], (tBu2InOEt)2 [35]; the ring is planar,
but not square. The M−O−M bond angle is 97.4(2)o for
gallium and 100.62(4)o for indium, while the O−M−O
angle is 82.6(2)o for gallium and 79.38(4)o for indium.
Important bond lengths and angles are summarized in
Table 3.
2: M=Ga; R=Me; R’=Me2tBu; yield: 68%
3: M=Ga; R=Me; R’=Et; yield: 91%
4: M=In; R=Me; R’=Ph; yield: 75%
5: M=In; R=Me; R’3=Me2tBu; yield: 94%
6: M=In; R=Me; R’=Et; yield: not quantified
7: R=Me; M=Ga; R’=Ph; yield: 95%
8: R=Et; M=Ga; R’=Ph; yield: 75%
9: R=Me; M=Ga; R’=iPr; yield: 75%
10: R=Et; M=Ga; R’=iPr; yield: 70%
11: R=Me; M=In; R’=Ph; yield: 91%
12: R=Me; M=In; R’=iPr; yield: 78%
The Ga(1)−O−Ga bond angle in (1) is smaller than
other known Ga2O2 compounds such as (H2GaOtBu)2,
([tBu2Ga(OOtBu)]2 and (tBu2GaOH)3; but is larger than
the Ga−E−Ga bond angles where oxygen is replaced
by sulfur or phosphorous. The gallium siloxide (1) has a
Ga2O2 ring that is closer to being square than the gallium
1229

Silylated gallium and indium chalcogenide ring
systems as potential precursors to ME (E=O, S) materials
Table1. Summary of physical and spectroscopic properties of compounds (1)-(12).
Compound
Appearance
mp oC
29Si{1H} NMR
1H NMR (C6D6) δR2M
(1) (Me2GaOSiPh3)2
(2)(Me2GaOSitBuMe2)2
(3) (Me2GaOSiEt3)2
(4) (Me2InOSiPh3)2
(5) (Me2InOSitBuMe2)2
(6) (Me2InOSiEt3)2
White solid
White solid waxy
Liquid
165
-8.04
22.95
22.78
-14.5
15.5
-0.21
-0.01
-0.1
0.0
45
-
168
45
White solid
White solid waxy
Liquid
0.1
-
-21.9
-2.44
-0.02
0.0
(7) (Me2GaSSiPh3)2
Colorless solid
195-196
0.65 (CH2, quart), 1.07 (CH3, t),
JHH=6.61Hz
(8) (Et2GaSSiPh3)2
Colorless solid
156-157
-2.35
(9) (Me2GaSSiiPr3)2
(10) (Et2GaSSiiPr3)2
(11) (Me2InSSiPh3)2
(12) (Me2InSSiiPr3)2
White solid waxy
Liquid
47-48
-
30.64
30.37
-2.35
29.02
0.153
0.8(unresolved multiplet)
White solid
158
45
0.0
White solid waxy
0.18
C1
C2
Ga
O
Si
O
Si
Ga
C2
C1
Figure 1. ORTEP diagram of (1) with H-atoms omitted for clarity. Thermal ellipsoids are drawn at the 40% probability level. The crystallographic
center of symmetry lies at the center of the four-membered Ga O ring.
2
2
alkoxides [36], but is not perfectly square as the one sulfur-containing analogs (7) [41] and (8) [42] where
encountered for [Ar’GaO]2 [37]. In contrast to aluminum the triphenylsilyl groups are in trans configuration.
and gallium, not many examples of the heavier group For indium, the sulfur-containing analogue has a six-
13 analogues of these oxides have been isolated. membered (InS)3 ring in a skew-boat conformation [43].
The coordination geometry at the indium center is Since the delocalization of the oxygen lone pair over the
tetrahedral. The In−O distance [2.1815(11) Å] and the metal and silicon atoms would contribute to the planarity,
In−O−In angle [100.62(4)o] are similar to those found the sulfur lone pair electrons are not as well delocalized.
for other In2O2 cores [38-40], and the In−C bond length A comparison of bond angles around oxygen and sulfur
[2.1348(19)Å] is in the region previously observed for in other gallium dimeric systems shows that oxygen is
In−C bonds(2.09-2.25 Å).
usually planar, with the sum of the bond angles near
The silicon atoms also lie in the plane with the metal 360o. Sulfur atoms are closer to tetrahedral, with the
and oxygen atoms. This is in contrast to the gallium sum of the bond angles less than 327o.
1230

I. E. Medina-Ramírez et al.
Table2. Crystal data and structure refinement for (1), (4), (9) and (7).
Compound
(4)
(1)
(9)
(7)
Empirical formula
Formula weight
Crystal system
Space group
C40H42In2O2Si2
840.56
C40H42Ga2O2Si2
750.36
C22H54Ga2S2Si2
578.39
C40H42Ga2S2Si2
782.48
Triclinic
Triclinic
P1
Monoclinic
P21/n (No. 14)
Triclinic
P1
P1 (No. 2)
Unit cell
dimensions
a [Å]
b [Å]
c [Å]
8.8205(6)
9.5990(6)
13.1037(9)
9.591(2)
12.964(3)
8.846(3)
9.1183(5)
9.0036(5)
18.3012(10)
8.9667(6)
13.7580(9)
16.2507(11)
α [deg]
β [deg]
γ [deg]
69.2940(10)
73.1500(10)
64.4000(10)
105.42(2)
115.87(2)
70.30(2)
90
94.9730(10)
90
102.0000(10)
95.0880(10)
103.0100(10)
Volume (Å3)
923.48(11)
2
922.5(4)
1
1496.83(14)
2
1891.2(2)
2
Z
Density (calculated)
[g cm-3]
1.511
1.346
1.351
1.558
1.283
2.027
1.374
2.027
Absorption
coefficient [mm-1]
F(000)
424
0.04×0.20×0.22
100
388
0.33×0.26×0.13
100
616
0.05×0.25×0.27
100
808
0.35×0.28×0.23
100
Crystal size [mm]
Temperature (K)
Radiation MoKα [Å]
0.71073
0.71073
0.71073
0.71073
Θ range for data
1.7 to 28.3
1.69 to 25.07
2.2 to 28.3
1.29 to 28.31
collection [o]
Tot., Uniq. Data, R
(int)
8289, 4278, 0.013
3504, 3287, 0.0292
12942, 3585, 0.022
17058, 8802, 0.015
Observed data
[I>2σ(I)]
4122
3504
3204
8115
Data, parameters
4278, 210
3287, 210
3585, 135
3585, 135
Final R1, wR2
[I>2σ(I)]
0.0192, 0.0508
0.1214, 0.1953
0.0222, 0.0581
0.0280, 0.0699
Goodness-of-fit
1.06
1.03
1.07
1.062
on F2
3.2. Silanethiolato complexes of Gallium and
solution. In order to explore this possibility, the effects of
temperature and concentration on (7) were evaluated.
Variable-temperature and variable-concentration
NMR studies were conducted. The chemical shift of the
methyl groups on the (CH3)2Ga moiety was found to be
temperature-dependent. Results are presented in Fig. 3.
At temperatures below 10oC, we observe two chemical
shifts that correspond to the dimer-trimer species (the
resonance for the dimer and trimer are assigned on
the basis of a comparison of chemical shifts reported
for (Me2AlSSiPh3)2) [29]. In order to corroborate that
the solution equilibrium presented by (7) corresponds
to a redistribution rather than a conformational process,
an additional study was carried out in which the
concentration of (7) was varied. The experiment was
carried at a constant temperature of -20oC. Results are
presented in Fig. 4. The data from this study show that
Indium
Details regarding general synthetic aspects, physical
properties and NMR characterization of silanethiolato
complexes were presented in the previous section. The
1
room temperature H NMR spectrum of (7) shows a
broadened line (δ= 0ppm) for the methyl groups attached
to gallium, suggesting fluxionality in the molecule. Earlier,
Taghiof [44] reported that aluminum thiolates establish
equilibria between different aggregates (most commonly
dimers and trimers) and conformations (syn and anti) in
hydrocarbon solutions. The dynamic behavior of (7) in
solution was investigated.
Although in the solid state, (7) shows the presence
of a puckered (GaS)2 core with anti orientation of the
bridging ligands, there exists a possibility that (7)
may exhibit redistribution or conformation equilibria in
1231

Silylated gallium and indium chalcogenide ring
systems as potential precursors to ME (E=O, S) materials
Table 3. Selected bond lengths [Å] and angles [deg] for (1) and (4), and for (7) and (9). Symmetry transformations used to generate equivalent
atoms: −x, −y+1, −z+2.
Bond lengths(Å)
C40H42Ga2O2Si2 (1)
C40H42In2O2Si2 (4)
M-C(2)
1.929(8)
1.933(8)
1.968(4)
1.978(4)
1.651(4)
1.968(4)
2.1348(19)
2.1373(19)
2.1815(11)
2.1939(11)
1.6370(11)
2.1940(11)
M-C(1)
M-O(1)
M-O
Si-O
O-M
Bond Angles(deg)
C(2)-M-C(1)
C(2)-M-O(1)
C(1)-M-O(1)
C(2)-M-O
127.1(4)
110.9(3)
137.21(9)
107.53(6)
107.33(6)
103.07(6)
107.06(7)
79.38(4)
109.9(3)
106.4(3)
C(1)-M-O
110.9(3)
O(1)-M-O
82.6(2)
Si-O-M(1)
130.7(2)
128.16(6)
129.99(6)
100.62(4)
C22H54Ga2S2Si2(9)
1.9616(15)
1.9605(15)
2.3974(4)
2.4113(4)
2.1732(5)
2.4113(4)
Si-O-M
130.3(2)
M(1)-O-M
97.4(2)
Bond lengths(Å)
Ga(1)-C(1)
Ga(1)-C(2)
Ga(1)-S(2)
Ga(1)-S(1)
S(1)-Si(1)
C40H42Ga2S2Si2 (7)
1.9546(17)
1.9597(17)
2.4094(4)
2.4363(4)
2.1461(5)
S(1)-Ga
Bond angles (deg)
C(1)-Ga(1)-C(2)
C(1)-Ga(1)-S(2)
S(2)-Ga(1)-S(1)
C(3)-Ga(2)-S(2)
S(2)-Ga(2)-S(1)
Si(1)-S(1)-Ga(2)
Si(1)-S(1)-Ga(1)
Ga(2)-S(1)-Ga(1)
125.94(8)
113.77(6)
87.144(14)
113.57(5)
87.592(14)
119.09(2)
114.882(19)
90.163(14)
119.40(7)
116.52(5)
87.820(13)
105.80(5)
87.820(13)
122.509(18)
115.628917)
92.180(13)
dimers predominate in diluted solution, whereas trimers different temperatures can be obtained by integration of
predominate in concentrated solutions (2(Me2GaSSiPh3)3 the resonances; from here, the equilibrium constant can
↔3(Me2GaSSiPh3)2).
be determined. Our results and additional results from
Thermodynamic and activation energy parameters a number of related systems are given in Table 4 for
were calculated from variable-temperature NMR data. comparison. Some interesting generalizations can be
The ratio of the concentration of these species at drawn from the thermodynamic parameters encountered
1232

I. E. Medina-Ramírez et al.
C1
C2
O
Si
Si
In
C2
C1
Figure 2. ORTEP diagram of (4) with H-atoms omitted for clarity. Thermal ellipsoids are drawn at the 30% probability level.
t
d
o
o
-20C
30 C
t
d
o
18 C
o
-30 C
d
t
d
t
o
o
-40 C
10 C
d
d
t
t
o
o
-50C
0 C
t
t
d
d
o
o
-10 C
-60 C
0. 1
0.0
-0.1
0.1
0.0
-0.1
Figure 3. VT-1H NMR for (Me2GaSSiPh3)2.
for (7). First, the value 1.236 of Keq at room temperature trimer is enthalpically favored and predominates at low
indicates that concentration of the different aggregates temperatures. The origin of the favorable enthalpy is
is nearly equivalent. The exchange between them takes likely due to ring strain found for the dimers but not for
place at a rate faster than the NMR timescale, giving the trimers. At room temperature, a balance between the
rise to a single broad resonance for both aggregates entropy and enthalpy terms leads to a small negative
at room temperature. The large positive value for ∆So ∆Go value and an equilibrium constant near unity.
is in agreement with the formation of a greater number
VT-NMR data for (8) shows that ethyl resonances
of molecules going from trimers to dimers. Second, the are not temperature-dependent. The increased bulk of
1233

Silylated gallium and indium chalcogenide ring
systems as potential precursors to ME (E=O, S) materials
the organic substituents bound to gallium favor dimeric pentane at -40oC. The parameters from the crystal
aggregates in solution. These observations are in structure determination of (7) and (9) are presented in
accordance with Oliver [3] and Beachley [41].
Crystals of (7) were grown from a toluene/hexane
(1:1) solution at 0oC. Crystals of (9) were grown from system, and (9) was in the monoclinic cell system.
Table 2.
Compound (7) was found to be in the triclinic cell
Both compounds have a dimeric structure with a Ga2S2
d
central core. An ORTEP diagram of the molecular unit
for (7) is shown in Fig. 5 and the molecular unit for (9) is
shown in Fig. 6. Compound (7) and compound (9) differ
t
mainly in the shape of the central ring which is flat in (9)
but bent in (7).
o
-20 C
The molecular structures for the aluminum and
[ ]=0.03 M
indium analogues of (7) were previously determined.
The aluminum and gallium thiolates, show (MS)2
d
ring cores, whereas the indium derivative, has a six-
t
membered (InS)3 ring in a skew-boat conformation.
The bridging groups in these compounds are found in
the anti conformation. The sulfur atom is pyramidal.
[ ] =0.05M
o
The butterfly conformation of (7) compares with that
-20 C
observed in (Et2GaSSiPh3)2 [29], [Me2GaS(C6F5)]2 [45]
and [I2GaS(iPr)]2 [46]. The planar conformation of (9)
compares with that observed in [tBu2Ga(µ−SH)]2 [47],
t
d
[Ph2GaSEt]2 [48], and{Ph2GaS[Sn(C6H11)3]}2 [49]. The
geometry around the gallium atom is normal for this type
of compounds and can be best described as distorted
[ ]=0.12 M
o
tetrahedral. Selected bond lengths and angles are given
-20 C
in Table 3.
0.10
0.05
0.00
-0.05
-0.10
-0.15
A
3.3. TGA measurements
Thermal stability and thermal decomposition behavior
of complexes (1), (2), (4), (5), (11) and (12) were
1
Figure 4. H NMR for (Me2GaSSiPh3)2 as a function of precursor
concentration
.
Figure 5. ORTEP diagram of (7) with H-atoms omitted for clarity. Thermal ellipsoids are drawn at the 30% probability level.
1234

I. E. Medina-Ramírez et al.
C5
C7
C3
C4
C6
Si
C1
C11
C8
C10
C9
S
Ga
C2
Figure 6. ORTEP diagram of (9) with H-atoms omitted for clarity. Thermal ellipsoids are drawn at the 30% probability level.
Table 4. Thermodynamic parameters for the equilibrium process, 2 trimer ←→ 3 dimer, in selected (R2MER’)n systems.
Compound
Keq 25oC
∆HokJmol-1
∆SoJmol-1
∆GokJmol-1
(Me2AlSMe)n
0.4
180.0
31.0
1.236
44.5
0.6
23.1
11.5
70.0
81.5
12.8
8.5
(Me2AlSeMe)n
(Me2AlSSiPh3)n
5.8
220
9.4
(Me2GaSSiPh3)2 (7)
(Me2AlS−2−FC6H4)n
(Me2AlS−2,6−C6H3)n
50.9(34)
68.0
172(13)
260.0
85.0
-0.5255
1.5
26.5
2.2
investigated by thermogravimetric analysis (TGA) and shows that the decomposition of (1) occurs as a multi-
pyrolysis experiments under an atmospheric pressure step process. The main event of weight loss occurs
of argon. A detailed study of the thermal behavior of within a temperature range of 220-400oC. It may be
gallium silane thiolates (7)-(10) was previously reported possible that this mass loss is associated to the loss
[50]. TGA was used to monitor the loss of sample mass of SiPh3 ligands, nevertheless the percent of mass lost
as function of temperature. In order to elucidate the (60%) is lower than the theoretical mass percent in the
mechanism of precursor fragmentation, an evolved molecule (69%). A second step of mass loss followed.
gas analysis using TGA-MS was performed. As pointed The rate of mass loss in this step is slower than the one
out before [46], analyses of the evolved gases was observed. The temperature range for the second event
not possible due to condensation of the gases before of mass loss goes from 425-650oC. The residual weight
reaching the detector. Bulk pyrolysis of the compounds at the end of the experiment (20.5%) is slightly lower than
yielded residues that were characterized by XRD. the theoretical weight for the formation of GaO (22.8%).
Results are summarized in Table 5.
Compound (2) decomposes at lower temperature than
The TGA results for the siloxide derivatives show (1). The weight loss is complete around 200oC. There
that in general, complexes that contain (−SiPh3) is only 9% residual weight by the end of the experiment
substituents on the group 16 atom decomposed at (500oC). The TGA for (2) was carried out under different
higher temperatures compared to the (−SitBuMe2) conditions to try to minimize the loss of sample due to
derivatives. The thermal behavior of (3) and (6) could sublimation. The results obtained show no significant
not be evaluated by TGA due to the fast event of mass differences.
loss observed for such complexes. The TGA curve of
In order to determine the composition of the inorganic
(Me2GaOSiPh3)2 (1) is presented in Fig. 7. The plot products produced by thermolysis of (1) and (2), bulk
1235

Silylated gallium and indium chalcogenide ring
systems as potential precursors to ME (E=O, S) materials
of (Me2InOSiPh3)2 (4) shows a uniform mass loss as the
temperature is taken up to 1000oC with a heating rate of
10oC/min under argon. There is a major stage of mass
loss and it occurs in a narrow temperature range from
250oC to 360oC. The residual mass at the end of this
event of mass loss is 41% which correlates to the loss
of the SiPh3 substituents. The temperature of maximum
mass loss is 265oC, which is close to that observed for the
gallium analogous compound (270oC); this observation
supports that this event may correspond to the loss of
the triphenylsilyl groups. The second step of mass loss
shows an onset temperature of 595oC. This step may
correspond to the loss of alkyl groups attached to the
metal. The residual mass at the end of the experiment
is lower (27 vs. 31.1%) than the theoretical percentage
for the formation of InO, but it is in agreement to the
formation of indium metal (27.3%).
10 0
80
60
40
20
79.5%
x
0
200
400
600
800
o
Temperat ur e( C)
Figure 7. TGA curve for (Me2GaOSiPh3)2 (1). Heat rate 10oC min-1
under argon.
The XRD spectrum of the pyrolysis products from
precursors (4) and (5) corresponds to indium metal
(tetragonal, JCDPS #05-0642). Trace amount of cubic
In2O3 (JCDPS #65-3170) were also observed. XRD data
indicates that the formation of In metal is important and
therefore explains the higher than expected weight loss
observed by TGA. The deposition of In2O3 films from
these precursors may be possible using O2 as a carrier
gas, since it was shown that they decompose cleanly at
low temperatures.
As it was noticed above, a detailed study on the
thermal behavior of complexes (7)-(10), was previously
presented [50]. The complexes decompose from 200-
350oC to give the hexagonal phase of GaS. The ethyl
gallium derivatives were found to undergo an initial
loss of ethylene followed by a second unresolved
mode of decomposition. In contrast, the methyl gallium
10 0
80
60
x
91.1%
40
20
0
0
100
20 0
300
400
500
o
Temp er at ure( C)
Figure 8. TGA curve for (Me2GaOSit BuMe2)2 (2). Heat rate 2oC min-1
under argon.
pyrolysis of these complexes was carried out, and the derivatives decompose in one uniform stage to give
resulting powders were characterized by XRD. Typically, hexagonal gallium sulfide. Isopropylsilyl derivatives
the precursor was sealed under vacuum in a Pyrex were in general more volatile and decomposed at
ampoule which was then placed in a muffle furnace at lower temperatures than the triphenylsilyl derivatives.
400oC for 1 h. After cooling to room temperature, the
TGA data for (11) and (12) is in agreement with the
ampoules were open and the solid metal oxides were data for the gallium analogous. Results are summarized
washed with benzene and allowed to dry. The color of in Table 5. The resulting powders from the bulk pyrolysis
the powders produced was dark gray for both precursors. of compounds (11) and (12) were characterized by
The XRD analysis of the powders prepared at 400oC XRD. The diffraction features of the powder resulting
showed the presence of amorphous material since no from the pyrolysis of (11), correspond to indium metal,
well-defined peaks are observed in the XRD pattern. multiple phases of InxSy and amorphous material. In
Since the peaks were extremely broad, these powders contrast, the diffraction features of the powder resulting
were annealed by heating them up to a 1000oC for 1 h from the pyrolysis of (12) showed sharp peaks that
on a quartz crucible. The powders turned colorless and correspond to indium metal (tetragonal, JCDPS#05-
the XRD showed sharp features that correspond to the 0642) and indium sulfide (InS) (orthorhombic, JCDPS
reference spectrum of monoclinic Ga2O3 (JCDPS #43- #86-0637). Compound (11) was found not suitable as
1012).
precursor to indium sulfide, but the alternate compound
The indium siloxides exhibited a similar thermal (12), decomposes cleanly at low temperatures resulting
behavior to gallium siloxide analogues. The TGA curve in pure crystalline In and InS.
1236

I. E. Medina-Ramírez et al.
Table 5. Summary for thermal decomposition of (1)-(12). Residual mass and composition of solid residue. Decomposition temperatures (Tdec) are
defined as the temperature at which half of the sample’s eventual weight loss occurs.
Compound
TGA results
Pyrolysis product
(by XRD)
Decomposition
Residual weight
Obsvd. Calcd. (%)
range and (Tdec)/oC
(1) (Me2GaOSiPh3)2
(2) (Me2GaOSitBuMe2)2
(4) (Me2InOSiPh3)2
250-380(300)
75-220 (142)
230-600(280)
20.5
22.8
Ga2O3
Ga2O3
9.0
37.1
31.1
27.3
47.4
41.5
26.0
24.3
35.2
32.1
33.6
26.3
43.9
34.34
for InO
for In
27.0
27.0
35.5
35.5
28.9
26.9
29.7
28.0
38.0
38.0
38.5
38.5
In (tetragonal)
(5) (Me2InOSitBuMe2)2
225-400(230)
for InO
for In
In (tetragonal)
(7) (Me2GaSSiPh3)2
(8) (Et2GaSSiPh3)2
(9) (Me2GaSSiiPr3)2
(10) (Et2GaSSiiPr3)2
(11) (Me2InSSiPh3)3
140-440(338)
120-507(348)
113-352(306)
95-256(198)
200-450(352)
GaS (amorphous)
GaS (hexagonal)
GaS (hexagonal)
GaS (hexagonal)
In (tetragonal)
for InS
for In
InS (multiple phases)
In (tetragonal)
(12) (Me2InSSiiPr3)n
172-330(305)
for InS
for In
InS (orthorhombic)
4. Conclusions
Acknowledgement
A series of indium and gallium siloxide complexes We thank Dr. Al Hepp for invaluable discussions and
and silanethiolato complexes were prepared and encouragement.WealsothankOAI/NASA,theLouisiana
characterized by various spectroscopic and physical Board of Regents, NASA (NCC-946) through the Tulane
techniques. These compounds are versatile for Institute for Macromolecular Science and Engineering,
tailoring chemical and physical properties at the and NSF (0092001) for financial support.
molecular level. Changing the substituents attached
to the metal or to the silicon atom can easily modify
the physical properties of these compounds.
For (7), VT NMR studies showed that in solution, (7)
Supplementary Materials
undergoes rapid reversible interconversion between Supplementary crystallographic data are available from
dimer to trimer. The gallium siloxides, gallium the CCDC, Union Road, Cambridge CB2 1EZ, UK on
silanethiolates and indium silanethiolates complexes request quoting the deposition numbers CCDC 931603
tend to decompose to their core elements at low - 931606 (fax: +44 1223 336 033; e-mail: deposit@ccdc.
temperatures.
cam.ac.uk).
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