[Ag{S2CNR(C2H4OH)}] as Single-Source Precursor for Ag2S - Synthesis, Decomposition Mechanism, and Deposition Studies

Article abstract of DOI:10.1002/ejic.201403182

Silver(I) dithiocarbamates [Ag{S₂CNR(C₂H₄OH)}] (3a, R = Me; 3b, R = Bu) were accessible by the reaction of AgNO₃ with K{S₂CNR(C₂H₄OH)} (2a, R = Me; 2b, R = Bu). Alternatively, 3b could be prepared by the condensation of CS₂ and Ag₂O with NHBu(C₂H₄OH) (1b). The thermal behavior of 3 was studied by thermogravimetric (TG) analysis. A two-step decomposition process leads to the formation of α-Ag₂S, as evidenced by X-ray powder diffraction studies. A decomposition mechanism of 3a to form Ag₂S through the release of 3-methyloxazolidine-2-thione is discussed based on TG-MS, GC-MS, and NMR experiments. Because of the better solubility of 3b, this complex was tested for Ag₂S spin-coating deposition studies on different substrates (SiO₂/Si, TiN/SiO₂/Si, glass) with subsequent annealing at 450 °C under a N₂ atmosphere. Film thickness, composition, and morphology of the as-deposited films were determined by XRD, SEM, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy, which showed the formation of 200 nm thick, conformal, adherent, monoclinic α-Ag₂S layers.

Full text of DOI:10.1002/ejic.201403182

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DOI:10.1002/ejic.201403182
[Ag{S2CNR(C2H4OH)}] as Single-Source Precursor for
Ag2S – Synthesis, Decomposition Mechanism, and
Deposition Studies
Robert Mothes,[a] Alexander Jakob,[a] Thomas Waechtler,[b,c]
Stefan E. Schulz,[b,c] Thomas Gessner,[b,c] and Heinrich Lang*[a]
Keywords: Silver / S ligands / Thermal decomposition / Spin coating / Thin films
Silver(I) dithiocarbamates [Ag{S2CNR(C2H4OH)}] (3a, R =
GC–MS, and NMR experiments. Because of the better solu-
Me; 3b, R = Bu) were accessible by the reaction of AgNO3 bility of 3b, this complex was tested for Ag2S spin-coating
with K{S2CNR(C2H4OH)} (2a, R = Me; 2b, R = Bu). Alterna- deposition studies on different substrates (SiO2/Si, TiN/SiO2/
tively, 3b could be prepared by the condensation of CS2 and
Ag2O with NHBu(C2H4OH) (1b). The thermal behavior of 3
was studied by thermogravimetric (TG) analysis. A two-step
decomposition process leads to the formation of α-Ag2S, as
Si, glass) with subsequent annealing at 450 °C under a N2
atmosphere. Film thickness, composition, and morphology of
the as-deposited films were determined by XRD, SEM, en-
ergy-dispersive X-ray spectroscopy, and X-ray photoelectron
evidenced by X-ray powder diffraction studies. A decomposi- spectroscopy, which showed the formation of 200 nm thick,
tion mechanism of 3a to form Ag2S through the release of
conformal, adherent, monoclinic α-Ag2S layers.
3-methyloxazolidine-2-thione is discussed based on TG–MS,
ing,[20] and chemical vapor deposition[6,21] exist, and they
mainly comprise AgNO3 as a silver source and diverse
sulfur-containing species such as S8, H2S, CS2, Na2S,
Na2(S2O3), thioacetamide, thiourea derivatives, and poly-
phenylene sulfide as sulfur sources.[9–19]
Introduction
Among the three polymorphs of silver sulfide, the mono-
clinic low temperature modification α-Ag2S (acanthite) is a
I2–IV binary semiconductor with a bulk band gap of ap-
proximately 1 eV and a relatively high absorption coeffi-
cient (α = 104 cm–1) at ambient temperature.[1] In addition,
bulk α-Ag2S shows good photoelectric and thermoelectric
properties, which allow to use this material in diverse op-
tical and electronic devices, such as IR detectors, photocon-
ductors,[2] photosensitive materials for recording media,[3]
solar-selective coatings,[4] ion-selective electrode mem-
branes,[5] gas sensors,[6] and solid state memory devices.[7,8]
For the preparation of silver sulfide thin films, several
synthetic methodologies including chemical bath deposi-
tion,[9] spray pyrolysis,[1,10] thermal evaporation,[3,11,12]
molecular beam epitaxy,[13] sol–gel processes,[14] sulfur-
ization,[15] successive ionic-layer adsorption and reaction,[16]
electrodeposition,[17] electroless deposition,[18] electrochemi-
cal ion-exchange processes,[19] direct conversion, dip-coat-
Besides this classical synthesis approach, which has some
drawbacks,[6] the single-source-precursor approach, in
which the precursor molecules contain all the elements that
are required for the formation of the target material, shows
some advantages. These are, for example, excellent layer
uniformity, composition, and phase control, low cost, scal-
ability,[6] and facile development of metallic nanoparticles
in organic–inorganic hybrid matrices.[22] However, to the
best of our knowledge, there is only a limited number of
single-source precursors, such as [Ag(SC(O)Ph)]n,[20,23]
[Ag3((SPiPr2)6N3)]2,[21] and [Ag(S2CNEt2)]n,[6] described in
the literature for the generation of silver sulfide. This
prompted us to synthesize novel silver(I) dithiocarbamates
of the type [Ag{S2CNR(C2H4OH)}] (R = Me, Bu) and use
them as single-source precursors for the formation of sil-
ver(I) sulfide. The decomposition mechanism of these com-
plexes in the solid state is discussed as well.
[a] Technische Universität Chemnitz, Faculty of Natural Sciences,
Institute of Chemistry, Inorganic Chemistry,
09107 Chemnitz, Germany
E-mail: heinrich.lang@chemie.tu-chemnitz.de
https://www.tu-chemnitz.de/chemie/anorg/
[b] Technische Universität Chemnitz,
Results and Discussion
Center for Microtechnologies,
Silver(I) dithiocarbamato complexes of the type
[Ag{S2CNR(C2H4OH)}] (3a, R = Me; 3b, R = Bu) were
synthesized by the reaction of stoichiometric amounts of
AgNO3 and K{S2CNR(C2H4OH)} (2a, R = Me;[24] 2b, R
09107 Chemnitz, Germany
[c] Fraunhofer Institute for Electronic Nano Systems,
09126 Chemnitz, Germany
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201403182.
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Scheme 1. Synthesis of silver(I) dithiocarbamato complexes 3a and 3b.
= Bu) in a mixture of acetonitrile and ethanol (1:100, v/v) impurities), which agrees well with theoretical percentages
at low temperature (Scheme 1 and Exp. Sect.). The potas- calculated for the formation of Ag2S (Exp. Sect.). From this
sium salts necessary therefore, 2a and 2b, were prepared by figure it can also be seen that 3b starts to decompose at a
treating the secondary amines NHR(C2H4OH) (1a, R = temperature 40 °C lower than that observed for 3a, and 3b
Me; 1b, R = Bu) with an excess of carbon disulfide in an possesses a broader decomposition temperature range. The
ethanol solution of potassium hydroxide. Whereas 3a only resulting TG residues were analyzed by XRPD, which con-
dissolves in DMSO, complex 3b is soluble in most of the firmed the formation of crystalline α-Ag2S and traces of
common organic solvents, for example, dichloromethane. elemental silver (Figure 1, right).
This allows to synthesize 3b in a more elegant way by the
condensation reaction of CS2 and Ag2O in the presence of
1b (Scheme 1 and Exp. Sect.).
Dithiocarbamate 2b is a colorless, solid material soluble
in polar solvents like alcohols or water. The solids 3a and
3b differ, however, significantly in their properties. Whereas
3a is off-white and insoluble in most of the common sol-
vents (see above), complex 3b is of bright-yellow color and
dissolves, for example, in dichloromethane, tetrahydrofuran,
or short-chained alcohols. Another apparent characteristic
of 3b is that it is hygroscopic. Compared to 3b, complex 3a
is much more sensitive to light and decomposes within days
by forming silver.
Figure 1. Left: TG traces (N2, flow rate: 60 mLmin–1; heating rate:
10 Kmin–1) of 3a and 3b. Right: XPRD patterns of the TG residues
of 3a and 3b (α-Ag2S, black: [JCPDS 14–0072]; Ag, grey: [JCPDS
04–0783]).
Compounds 2b, 3a, and 3b were characterized by ele-
mental analysis, FT-IR spectroscopy, 1H and 13C{1H}
NMR spectroscopy, and high-resolution ESI-TOF mass
spectrometry. In addition, thermogravimetry (TG), TG–
MS, and GC–MS studies were carried out (Exp. Sect.).
The IR spectra of 2b, 3a, and 3b are characterized by
prominent absorptions typical for the dithiocarbamato
Nomura et al. stated in previous reports that, for exam-
ple, copper(II) dithiocarbamates containing ω-hydroxy
functionalities release 3-methyloxazolidine-2-thione through
a cyclocondensation–elimination pathway, as illustrated in
Figure 2.[26]
units with vibration bands at approximately 1500 (ν
)
˜
C–N
and 1100 cm–1 (νC–S) (Exp. Sect.).[25] As expected, the
˜
hydroxy functionality gives rise to a broad band at
3350 cm–1.
Whereas 1H NMR spectroscopy is less informative (Exp.
Sect.), 13C{1H} NMR studies can be used for monitoring
the progress of the formation of 3a and 3b, which is ac-
companied by a distinctive shift to higher field of the reso-
nances of the quaternary carbon atoms [213.9 (for 2a),
213.6 (for 2b), 203.7 (for 3a), 206.2 ppm (for 3b)].
Figure 2. Possible thermal decomposition of [Cu{S2CNMe-
(C2H4OH)}2], as described by Nomura et al. in reference[26b]
.
To verify the applicability of this mechanism for the sil-
TG studies were carried out to gain initial information ver(I) dithiocarbamato complexes shown herein, TG analy-
about the thermal behavior of 3a and 3b in the solid state. sis coupled with mass spectrometry (i.e., TG–MS) was car-
The corresponding TG traces are shown in Figure 1. This ried out by using [Ag{S2CNMe(C2H4OH)}] (3a). The TG–
figure also includes the X-ray powder diffraction (XRPD) MS traces, the thermogravimetric trace, its first derivative,
pattern of the TG residue (α-Ag2S). In Figure 1 it can be and the ion-current curves of the corresponding mass-to-
seen that both complexes undergo a two-step decomposi- charge ratios (m/z) are shown in Figure 3. This figure also
tion process with a mass loss of 48.1 (for 3a, 0.1% devia- contains the respective DSC (differential scanning calorime-
tion) and 58.0% (for 3b, 0.7% deviation, attributed to C try) trace of 3a.
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sulfur isotope pattern (not shown), which indicates the for-
mation of COS+, CH2NS+, and C2H4S+, respectively. The
isotope pattern for m/z = 76 (not depicted) confirms only
the formation of the monosulfur fragments CH2NOS+,
+
C2H6NS+, or C2H4OS+, whereas CS2 can be ruled out.
The m/z values assigned to the fragments detected during
decomposition of 3a (Figure 3) correspond to the release of
3-methyloxazolidine-2-thione and are further evidence for
the decomposition path proposed by Nomura and co-
workers (Figure 2).[26]
To corroborate this TG–MS finding, we additionally car-
ried out further investigations. Therefore, complex 3a was
maintained in a horizontal tube furnace under typical TG
conditions (N2 gas flow, heating rate: 10 Kmin–1), and vola-
tile decomposition products were collected in a liquid-nitro-
gen-cooled condensation trap. The trapped volatiles were
analyzed by (GC–MS) and NMR spectroscopy. From these
studies, a total of four compounds could be detected, three
of which could be unequivocally identified (Figure 4).
GC–MS studies in combination with 1H and 13C{1H}
NMR spectroscopy revealed the formation of compounds
I–IV, as shown in Figure 4 (Exp. Sect.). These data confirm
that for the (β-hydroxyethyl)methyldithiocarbamate 3a, sil-
ver sulfide was formed through a cyclocondensation–elimi-
nation pathway (Scheme 2).
Figure 3. Top: TG and DSC traces (Ar, flow rate: 60 mLmin–1;
heating rate: 5 Kmin–1) of 3a. Bottom: Selected mass fragments
observed during decomposition of 3a. [m/z = 15 (CH3+), 30
(CH2O+, C2H6+), 32 (S+), 44 (CH2NO+, C2H6N+) 48 (CH6NO+),
60 (COS+, CH2NS+), 64 (C4H2N+), 76 (CH2NOS+, C2H6NS+,
C2H4OS+)].
The m/z values and the corresponding fragments are
given in the caption of Figure 3. The first decomposition
step occurs between 140 and 180 °C, and it yields typical
The main decomposition path is most probably the re-
fragments with m/z = 60 (COS+, CH2NS+) and 76 lease of 3-methyloxazolidine-2-thione (I) to form [AgSH]
(CH2NOS+, C2H6NS+, C2H4OS+). Characteristic for the [Scheme 2, reaction pathway i]. Consecutively, molecule I
following decomposition step (180–230 °C) is the increase is able to undergo a rearrangement affording 3-methyl-1,3-
of the ion current of fragments with m/z = 32 (S+), 44 thiazolidin-2-one (II) (Scheme 2), as described for oxazolid-
(CH2NO+, C2H6N+), 48 (CH6NO+), and 60 (COS+, ine-2-thiones (derivatives of I), which form 1,3-thiazolidin-
CH2NS+). Between 230–400 °C, fragments with m/z = 15 2-ones (derivatives of II) in basic milieu, for example, in
(CH3+) and 30 (CH2O+, C2H6+) could be detected, which reference[28]. The in situ formed [AgSH] can further react
point to the formation of carbon–hydrogen fragments. with itself to give Ag2S [elimination of H2S, reaction path
Characteristic for m/z = 60 is the appearance of the typical ii], or it can react with another molecule of 3a to produce
Figure 4. Top left: gas chromatogram of the collected products obtained upon pyrolysis of 3a.[27] Top right: Corresponding mass spectra.
1
Bottom left: H NMR spectrum (in CDCl3). Bottom right: 13C{1H} NMR spectrum (in CDCl3). [I (+), m/z = 117; II (#), m/z = 117; III
(*) m/z = 133; IV (x), m/z = 130 (not identified)].
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Scheme 2. Proposed decomposition mechanism of 3a.
[AgOH] along with molecule III [Scheme 2, reaction path
iii]. The thus produced silver hydroxido species can either
react with 3a, with itself, or with [AgSH] to generate Ag2S
or a mixture of Ag2S and Ag2O [Scheme 2, reaction path-
ways iv and v], and the silver oxide decomposes to produce
elemental silver along with free oxygen[29] [Scheme 2, reac-
tion pathway vi]. However, the minor amount of silver,
found by, for example, XRPD studies, indicates that reac-
tion pathways iii–vi are of minor importance.
Deposition and Layer Characterization
For the deposition of silver sulfide formed from 3a and
3b by using the spin-coating methodology, we choose 3b
as a precursor, because this compound possesses a higher
solubility than 3a, which only dissolves in dimethyl sulfox-
ide, and in addition, it is more stable to air and light. In a
typical deposition study, 3b was dissolved in tetra-
hydrofuran (5 mmol, 5 mL) and dispensed onto pre-cleaned
substrate wafers such as SiO2/Si, TiN/SiO2/Si, or amorph-
ous quartz (for more details see the Exp. Sect.). The as-
deposited layers were immediately transferred to a tube fur-
nace and processed under typical TG conditions (vide su-
pra; N2 atmosphere, heating rate of 10 Kmin–1, annealing
at 450 °C for 60 min under N2 atmosphere) to produce the
respective silver(I) sulfide coatings (vide infra).
Figure 5. X-ray powder diffractograms of silver sulfide films de-
posited on glass (top), TiN/SiO2/Si (middle), and SiO2/Si (bottom)
by spin-coating and annealing at 450 °C of 3b. (α-Ag2S, [JCPDS
14–0072]; intensities and reflection positions differ according to the
substrate.).
and [Ag(S2CNEt2)]n as deposition precursors.[6,21] The layer
thickness is 200 nm, as evidenced from cross-section SEM
(Figure 6). The scotch tape test proved good adhesion of
the layers on the substrate material.
The resulting dark, lustrous layers were characterized by
XRPD, which showed the formation of monoclinic α-Ag2S
(JCPDS 14-0072) (Figure 5).
The surface morphology and composition of the de-
posited thin silver sulfide films were examined by scanning
electron microscopy (SEM) and energy-dispersive X-ray
spectroscopy (EDX). From the SEM micrographs shown in
Figure 6 it can be seen that layers obtained from 3b on a
SiO2/Si substrate exhibit a rough, conformal surface featur-
ing some pinholes. This is in good agreement with the
Figure 6. Left: SEM image (magnification 10000ϫ) of an α-Ag2S
film deposited on Si/SiO2 by using 3b as the precursor. Right: cross-
section SEM image (magnification 100000ϫ) of the 200 nm α-Ag2S
morphology of coatings obtained from {Ag3[(SPiPr2)6N3]}2 film.
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Table 1. XPS results of thin films deposited on SiO2/Si and TiN/SiO2/Si by using 3b as spin-coating precursor.
Surface composition [mol-%] Layer composition [mol-%]
Ag3d
S2p
O1s
C1s
K2p
Ag3d
S2p
O1s
C1s
K2p
SiO2/Si
TiN/SiO2/Si
41.2
34.0
11.5
12.8
18.0
15.5
24.1
32.6
5.2
5.2
56.2
61.5
20.5
21.8
14.6
10.5
3.2
3.0
5.5
3.2
The composition of the appropriate Ag2S films was de- layer significantly less (ca. 3%). The high carbon content
termined by EDX measurements, which show the charac- on the surface results most likely from hydrocarbon surface
teristic pattern of silver and sulfur (Figures S2 and S3, Sup- contaminations, which are due to exposure to air prior to
porting Information). In addition, the presence of silicon, the XPS analysis. In contrast, oxygen impurities were found
carbon, and oxygen atoms was observed. These elements on the surface (18% SiO2, 16% TiN) as well as in smaller
originate most probably from the substrate material. For amounts in the Ag2S layer itself (15% SiO2, 11% TiN). The
this reason, the energy of the electron beam was reduced potassium impurity is most probably related to the
from 10 to 5 keV to reduce the penetration depth. As a synthetic methodology applied (on the surface and in the
result thereof, a significant reduction of the silicon and oxy- layer: 5.2 and 5.5% for SiO2, 5.2 and 3.2% for TiN) (Exp.
gen signals was found. Analogously, for the TiN coated Sect.).
substrates the elements titanium and nitrogen were de-
tected.
The significant reduction in the carbon content after
3 min of argon sputtering (Table 1) can also be understood
X-ray photoelectron spectroscopy (XPS) was addition- from the C 1s peak disappearance in Figure 7, whereas for
ally performed to gain further information about the film potassium, the signal intensity remains approximately con-
composition. Concentration quantification was done by stant, and this leads to the conclusion that potassium atoms
using standard single-element sensitivity factors. For each are embedded in the layer.
sample, two individual measurements were carried out. The
The Ag 3d5/2 peak was determined at 368.37 eV (for
first was performed on the sample surface prior to any pre- SiO2/Si) and 368.5 eV (for TiN/SiO2/Si) (Figure 7). These
treatment. Thereafter, the sample surface was sputtered peak positions can neither be assigned to elemental silver
with Ar ions to remove surface contaminants (Ar, 4 keV, (368.26 eV) nor to pure silver sulfide (368.00–368.20 eV)
3 min). For each individual measurement, the following but rather to Ag2O (368.40 eV) and Ag2SO4 (368.40 eV),
spectra or spectral regions were recorded: survey (0– respectively.[30] The S 2p3/2 peak maxima were found at
1200 eV), C 1s (270–300 eV), Ag 3d (360–385 eV), S 2p 161.5 eV (for SiO2/Si) and at 161.6–161.7 eV (for TiN/SiO2/
(150–180 eV). For all depositions on SiO2/Si substrates and Si) (Figure 7). Because a binding energy between 160.7 and
TiN-coated SiO2/Si substrates, significant signals character- 161.9 eV is expected for Ag2S,[30] a correlation to the deter-
istic for silver and sulfur appeared. Additionally, oxygen, mined peak position is obvious, whereas the formation of
carbon, and potassium were detected (Table 1). Carbon Ag2SO4 (168.4 eV) can be ruled out. In summary, the Ag
contaminations were present primarily at the surface (SiO2, 3d5/2 and S 2p3/2 peak positions suggest that the layers con-
about 24%; TiN, about 33%), whereas they appeared in the sist of a mixture of Ag2S and Ag2O.[29]
Figure 7. XPS detail spectra on the surface (grey lines) and after Ar sputtering (black lines) of thin films deposited on SiO2/Si (top) and
TiN/SiO2/Si (bottom) by using 3b as a precursor complex.
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SEM, was applied to determine the chemical composition of the
coatings. XPS measurements were carried out by using a PREVAC
Conclusions
Silver dithiocarbamates [Ag{S2CNR(C2H4OH)}] (R = XPS system with a VG Scienta EW 3000 analyzer and a MX650
X-ray source producing monochromatic Al-Kα radiation. The de-
termined peak positions were compared to the NIST XPS Data-
base.[30]
Me, Bu) were synthesized by the reaction of AgNO3
with the respective potassium salt. Alternatively, for
[Ag{S2CNBu(C2H4OH)}], a more elegant route was used,
namely, the condensation of CS2 and Ag2O with the respec-
tive secondary amine. TG–MS, GC–MS, and NMR studies
of [Ag(S2CNMe(C2H4OH))] confirm the thermally induced
release of five-membered heterocycles (3-methyloxazolid-
ine-2-thione, 3-methyl-1,3-thiazolidin-2-one, 3-methylthi-
azolidine-2-thione) during formation of silver sulfide. With
soluble [Ag(S2CNBu(C2H4OH))] as a new single-source
precursor, spin-coating–annealing experiments on different
substrates resulted in the generation of dark lustrous α-
Ag2S layers, which were characterized by XRPD, SEM,
EDX, and XPS. These measurements revealed the forma-
tion of approximately 200 nm thick adherent films of a mix-
ture of Ag2S and Ag2O.
Reagents: All starting materials were obtained from commercial
suppliers and used without further purification. K[S2CNMe-
(C2H4OH)] (2a) was prepared according to a published pro-
cedure.[24]
Synthesis of Potassium Dithiocarbamate Salts K[S2CNR(C2H4OH)]
(compounds 2a[24] and 2b): The appropriate secondary amine (1a or
1b) (105 mmol) was added to an ethanol solution (500 mL) of KOH
(5.6 g, 100 mmol). To the cooled mixture (ice bath) was added
dropwise an ethanol solution (100 mL) of CS2 (6.04 mL, 15.23 g,
200 mmol). After stirring for 5 h at ambient temperature, the reac-
tion mixture was concentrated under reduced pressure, and dry di-
ethyl ether was added until precipitation reached completion. Sub-
sequently, 2a and 2b were filtered, washed with diethyl ether (3ϫ
50 mL), and dried in an oil-pump vacuum.
In comparison to studies with [Ag3{(SPiPr2)6N3}]2 re-
ported by Panneerselvam et al.[21] and with [Ag(S2CNEt2)]n
reported by Hussain et al.[6], the silver sulfide layers pro-
duced herein, which were processed at similar temperatures,
are more dense and uniform but also show some minor in-
homogeneity in their composition.
Synthesis of K[S2CNBu(C2H4OH)] (2b): Compound 2b was ob-
tained as a colorless solid soluble in ethanol and methanol.
Crystallization from an ethanol/diethyl ether mixture (ratio 10:1, v/
v, 10 mL) at 25 °C afforded colorless single crystals of 2b, yield
21.97 g (95 mmol, 95% based on 1b), m.p. 124 °C. C7H14KNOS2
(231.42): calcd. C 36.33, H 6.10, N 6.05; found C 36.00, H 6.07, N
5.93. IR (KBr): ν = 3325 (O–H), 2943, 2924, 2864 (C–H), 1458 (C–
˜
1
3
N) cm–1. H NMR (CD3OD): δ = 4.79 (s, 1 H, OH), 4.22 (t, JHH
= 6 Hz, 2 H, NCH2CH2OH), 4.14–4.08 [m, 2 H, NCH2(CH2)2-
CH3], 3.89 (t, JHH = 6 Hz, 2 H, NCH2CH2OH), 1.77–1.71 (m, 2
Experimental Section
3
General: All reactions were carried out under an argon or nitrogen
atmosphere by using standard Schlenk techniques. Tetrahydrofuran
and acetonitrile were purified by distillation from sodium/benzo-
phenone ketyl; dichloromethane was purified by distillation from
calcium hydride.
H, NCH2CH2CH2CH3), 1.38–1.30 [m, 2 H, N(CH2)2CH2CH3],
3
0.95 [t, JHH = 7 Hz, 3 H, N(CH2)3CH3] ppm. 13C{1H} NMR
(CD3OD): δ = 213.6 (s, S2CN), 61.2 (s, NCH2CH2OH), 56.5/56.2
[s/s, NCH2CH2OH/NCH2(CH2)2CH3], 30.0 (s, NCH2CH2CH2-
CH3), 21.1 [s, N(CH2)2CH2CH3], 14.3 [s, N(CH2)3CH3]. HRMS
(ESI-TOF, neg. mode): calcd. for [M – K]– 192.0511; found
192.0515.
Instruments: FT-IR spectra were recorded with a Thermo Nicolet
IR 200 spectrometer. NMR spectra were recorded with a Bruker
Avance III 500 spectrometer (500.3 MHz for 1H, 125.7 MHz for
13C{1H} and 202.5 MHz for 31P{1H} spectra). Chemical shifts are
reported in δ (parts per million) downfield from tetramethylsilane
(δ = 0.0 ppm) with the solvent as a reference signal 1H NMR:
CDCl3, δ = 7.26 ppm; CD3OD, δ = 3.31 ppm; [D6]DMSO, δ =
2.50 ppm. 13C{1H} NMR: CDCl3, δ = 77.16 ppm; CD3OD, δ =
49.00 ppm; [D6]DMSO, δ = 39.52 ppm. Melting points were deter-
mined by using a Gallenkamp MFB 595 010 M melting point appa-
ratus. Microanalyses were performed with a C, H, N analyzer
FlashAE 1112 instrument (Thermo Company). High-resolution
mass spectra were recorded with a Bruker Daltonik micrOTOF-
QII spectrometer. TG experiments were performed with a Mettler
Toledo TGA/DSC1 1100 system with an UMX1 balance. TG–MS
experiments were performed with a Mettler Toledo TGA/DSC1
1600 system equipped with a MX1 balance coupled to a Pfeifer
Vacuum MS Thermostar GSD 301 T2 mass spectrometer. X-ray
powder diffraction patterns of all samples were measured with a
STOE-STADI-P diffractometer by using Cu-Kα radiation (40 kV,
40 mA) and a Ge(111)-monochromator. Spin-coating experiments
were carried out by using a nitrogen-purged Laurell WS-400-6NPP
equipment. Thermal treatment of the as-spin-coated samples was
carried out with a Carbolite MTF 12/38/400 tube furnace. The sur-
face morphology was investigated by field-emission scanning elec-
tron microscopy by using a ZEISS Supra60 SEM. EDX analysis,
carried out by using a Bruker Quantax 400 system attached to the
Synthesis of [Ag{S2CNMe(C2H4OH)}] (3a): To 2a (950 mg,
5 mmol) in ethanol (100 mL) was added dropwise at 0 °C a solution
of AgNO3 (849 mg, 5 mmol) in an acetonitrile/ethanol mixture
(2.5 mL/25 mL). Afterwards, the resulting suspension was stirred
at ambient temperature for 4 h. Precipitated 3a was filtered off,
washed subsequently with water, ethanol, and diethyl ether, (each
3ϫ 50 mL) and dried in an oil-pump vacuum. Complex 3a was
obtained as an off-white solid, which is insoluble in water and com-
mon organic solvents, except dimethyl sulfoxide, yield 1.27 g
(4.92 mmol, 98% based on 2a), m.p. 175 °C (dec.). C4H8AgNOS2
(258.11): calcd. C 18.61, H 3.12, N 5.43; found C 18.75, H 3.05, N
5.29. IR (KBr): ν = 3338 (O–H), 2959, 2853 (C–H), 1480 (C–N),
˜
1104 (C–S) cm–1. 1H NMR ([D6]DMSO): δ = 4.90 (s, 3JHH = 5 Hz,
3
1 H, OH), 4.09 (t, JHH = 6 Hz, 2 H, NCH2CH2OH), 3.74 (p.q,
3JHH = 6 Hz, 2 H, CH2CH2OH), 3.55 (s, 3 H, NCH3) ppm.
13C{1H} NMR ([D6]DMSO): δ = 203.7 (s, S2CN), 61.0 (s,
CH2CH2OH), 58.2 (s, NCH2CH2OH), 46.7 (s, NCH3) ppm. TG
(10 Kmin–1, N2: 60 mLmin–1): υs = 140 °C, υf = 380 °C, Δm =
51.9%. Residue calcd. 48.0% (1/2 Ag2S); found 48.1%. HRMS
(ESI-TOF, pos. mode): calcd. for [2M – Ag]+ 406.9140; found
406.9098.
Synthesis of [Ag{S2CNBu(C2H4OH)}] (3b)
Method A: To AgNO3 (1.70 g, 10 mmol) dissolved in acetonitrile
(5 mL) was added dichloromethane (100 mL) in a single portion.
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The resulting colorless suspension was cooled to 0 °C, and there-
after 2b (2.31 g, 10 mmol) was added in a single portion. The reac-
tion mixture was stirred at this temperature for 3 h, and then all
volatiles were removed in an oil-pump vacuum, yield 2.79 g
(9.3 mmol, 93% based on AgNO3).
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Method B: Ag2O (2.37 g, 10 mmol) and 1b (6.2 mL, 5.79 g,
25 mmol) were suspended in dichloromethane (100 mL) and cooled
to 0 °C, and a solution of CS2 (15.1 mL, 19.04 g, 250 mmol) in
dichloromethane (50 mL) was added dropwise. After stirring the
reaction mixture for 10 h at ambient temperature, it was filtered
through a pad of Celite. After removing all volatiles in a vacuum
and washing the residue with diethyl ether (3ϫ 50 mL), complex
3b was obtained as a yellow solid, which is soluble in, for example,
dichloromethane, acetone, and ethanol, yield 2.67 g (8.9 mmol,
89% based on Ag2O), m.p. 110 °C (dec.). C7H14AgNOS2 (300.19):
calcd. C 28.01, H 4.70, N 4.67; found C 27.96, H 4.66, N 4.64. IR
[7]
[8]
[9]
(KBr): ν = 3368 (O–H), . 2954, 2928, 2869 (C–H), 1480 (C–N),
˜
1
3
1110 (C–S) cm–1. H NMR (CDCl3): δ = 4.15 (t, JHH = 5.4 Hz, 2
H, NCH2CH2OH), 4.07 (p.q, H/2 H, NCH2CH2/nBu,
CH2CH2OH), 3.43 (br. s, H, OH), 1.77 (p.quint, H,
2
1
2
3
NCH2CH2CH2CH3), 1.34 [p.sext, JHH = 7.4 Hz, 2 H, N(CH2)2-
3
CH2CH3], 0.94 [t, JHH = 7.4 Hz, 3 H, N(CH2)3CH3] ppm.
13C{1H} NMR (CDCl3):
δ = 204.4 (s, S2CN), 60.1 (s,
CH2CH2OH), 59.1/58.8 [s/s, NCH2(CH2)2CH3/NCH2CH2OH],
28.9 (s, NCH2CH2CH2CH3), 20.2 [s, N(CH2)2CH2CH3], 13.9 [s,
N(CH2)3CH3] ppm. TG (10 Kmin–1; N2, 60 mLmin–1): υs
=
100 °C, υf = 430 °C, Δm = 58.1%. Residue calcd. 41.3% (1/2 Ag2S);
found 41.9%. HRMS (ESI-TOF, pos. mode): calcd. for [2M – Ag]+
491.0102, found 491.0079; calcd. for [4M – 3Ag]+ 875.0999, found
875.1113.
[10]
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Pyrolysis of 3b: Thermal treatment of 3b (0.9 g, 3 mmol) was car-
ried out in a horizontal tube furnace (Carbolite MTF 12/38/400)
under TG conditions (N2 atmosphere, heating rate of 10 Kmin–1
up to 450 °C). All volatile decomposition products were collected
in a liquid-nitrogen-cooled condensation trap. The trapped volatiles
were analyzed by 1H and 13C{1H} NMR spectroscopy. I: 1H NMR
3
(CDCl3): δ = 3.79 (t, JHH = 5 Hz, 2 H, NCH2), 2.98 (t, JHH
=
[12]
[13]
[14]
[15]
[16]
5 Hz, 2 H, OCH2), 2.60 (s, 3 H, NCH3) ppm. 13C{1H} NMR
(CDCl3): δ = [NC(S)O] not found, 58.1 (NCH2), 52.2 (OCH2), 34.1
1
3
(NCH3) ppm. II: H NMR (CDCl3): δ = 3.54 (t, JHH = 7 Hz, 2
3
H, NCH2), 3.19 (t, JHH = 7 Hz, 2 H, SCH2), 2.79 (s, 3 H, NCH3)
ppm. 13C{1H} NMR (CDCl3): δ = 172.1 [NC(O)S], 50.5 (NCH2),
1
31.6 (NCH3), 25.3 (SCH2) ppm. III: H NMR (CDCl3): δ = 4.05
3
3
(t, JHH = 8 Hz, 2 H, NCH2), 3.22 (t, JHH = 8 Hz, 2 H, SCH2),
3.18 (s, 3 H, NCH3) ppm. 13C{1H} NMR (CDCl3): δ = 196.4
[NC(S)S], 58.9 (NCH2), 36.7 (NCH3), 27.0 (SCH2) ppm. IV: 1H
NMR (CDCl3): δ = 4.20, 3.82, 3.46 ppm. 13C{1H} NMR: δ = 211,
61.1, 57.5, 43.4 ppm.
[17]
Supporting Information (see footnote on the first page of this arti-
cle): Supporting information includes additional SEM images,
EDX data, and XPS survey spectra.
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Acknowledgments
The authors gratefully acknowledge the Fonds der Chemischen In-
dustrie (FCI) and the Deutsche Forschungsgemeinschaft (DFG)
(IRTG, GRK 1215 - Materials and Concepts for Advanced Inter-
connects) for generous financial support. Cornelia Kowol is
thanked for performing the SEM and EDX measurements and
Prof. Michael Mehring and Dr. Maik Schlesinger for XRPD mea-
surements.
[21]
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pyrolysis of 3a. Because of continuous inert gas flow during
the thermal treatment in the tube furnace, the more volatile
Received: December 12, 2014
Published Online: ᭿
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FULL PAPER
Single-Source Precursors
R. Mothes, A. Jakob, T. Waechtler,
S. E. Schulz, T. Gessner, H. Lang* ... 1–9
[Ag{S2CNR(C2H4OH)}] as Single-Source
Precursor for Ag2S – Synthesis, Decompo-
sition Mechanism, and Deposition Studies
The synthesis, thermal behavior, and de-
composition mechanism of [Ag{S2CNR-
(C2H4OH)}] (R = Me, Bu) is discussed. Its
application as a single-source spin-coating
precursor for thin-film α-Ag2S fabrication
is reported.
Keywords: Silver / S ligands / Thermal de-
composition / Spin coating / Thin films
Eur. J. Inorg. Chem. 0000, 0–0
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