Synthesis, crystal structure and thermal behavior of dimethylgold(III) derivatives of salicylaldimine Schiff bases - Novel precursors for gold MOCVD applications

Article abstract of DOI:10.1016/j.jorganchem.2008.04.028

Dimethylgold(III) complexes with salicylaldimine Schiff bases of general formula Me₂Au(Sal{double bond, long}N-R) (R = methyl (1), iso-propyl (2), or cyclohexyl (3)) have been synthesized in a single step reaction from dimethylgold(III) iodide [Me₂AuI]₂ and N-substituted salicylaldimines. Single-crystal X-ray studies provide evidence of mononuclear four-coordinated complexes with square-planar coordination geometry. The temperature dependences of saturated vapour pressure of complexes have been studied by the Knudsen effusion method with mass spectrometric analysis of the composition of the gas phase. The thermodynamic parameters of the sublimation process ΔH^o_T and ΔS^o_T have been calculated. Thermal decomposition of the vapour of compounds has been studied by means of high temperature mass spectrometry in a vacuum, and by-products have been determined. All of these complexes show good volatility and thermal stability. For complex 2, which is more volatile and low-melting, pulse MOCVD experiments have been carried out at substrate temperatures lower than 200 °C. The deposited gold nanoparticles (5-15 nm) have been investigated by means of SEM and AFM.

Full text of DOI:10.1016/j.jorganchem.2008.04.028

Journal of Organometallic Chemistry 693 (2008) 2572–2578
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis, crystal structure and thermal behavior of dimethylgold(III) derivatives
of salicylaldimine Schiff bases – Novel precursors for gold MOCVD applications
a
a
a
Aleksandr A. Bessonov a,b, , Natalia B. Morozova , Nikolay V. Gelfond , Pyotr P. Semyannikov ,
*
Iraida A. Baidina a, Sergey V. Trubin a, Yuriy V. Shevtsov a, Igor K. Igumenov a
a Nikolaev Institute of Inorganic Chemistry of Siberian, Branch of Russian Academy of Sciences, Lavrentiev Avenue 3, Novosibirsk 630090, Russia
b Novosibirsk State University, Novosibirsk, Russia
a r t i c l e i n f o
a b s t r a c t
Article history:
Dimethylgold(III) complexes with salicylaldimine Schiff bases of general formula Me2Au(Sal@N–R)
(R = methyl (1), iso-propyl (2), or cyclohexyl (3)) have been synthesized in a single step reaction from
dimethylgold(III) iodide [Me2AuI]2 and N-substituted salicylaldimines. Single-crystal X-ray studies pro-
vide evidence of mononuclear four-coordinated complexes with square-planar coordination geometry.
The temperature dependences of saturated vapour pressure of complexes have been studied by the
Knudsen effusion method with mass spectrometric analysis of the composition of the gas phase. The
thermodynamic parameters of the sublimation process DHoT and DSTo have been calculated. Thermal decom-
position of the vapour of compounds has been studied by means of high temperature mass spectrometry in
a vacuum, and by-products have been determined. All of these complexes show good volatility and thermal
stability. For complex 2, which is more volatile and low-melting, pulse MOCVD experiments have been car-
ried out at substrate temperatures lower than 200 °C. The deposited gold nanoparticles (5–15 nm) have
been investigated by means of SEM and AFM.
Received 15 February 2008
Received in revised form 8 April 2008
Accepted 22 April 2008
Available online 30 April 2008
Keywords:
Organogold(III) precursors
X-ray structure
Vapour pressure
Thermal decomposition
Gold MOCVD
Gold nanoparticles
Ó 2008 Elsevier B.V. All rights reserved.
1. Introduction
ever, the study of gold MOCVD processes has been somewhat lim-
ited by the lack of suitable precursors [7]. The most popular
Gold nanomaterials have important applications in optical
devices [1–3], solar cells [4], and for nano and microelectronics
[5–8]. Other applications include use gold nanoparticles as cata-
lytic systems for epoxidation of propylene, and CO oxidation at
low temperature when deposited with high dispersion on the sur-
face of TiO2, Fe2O3, and Al2O3 [9–12]. Moreover, catalytic activity of
Au catalysts strongly depends on formation conditions and particle
size [13–15]. Among various deposition methods under consider-
ation, metal organic chemical vapour deposition (MOCVD) attracts
more attention because it allows us to obtain gold coatings as ul-
tra-fine particles [9], thin films [16,17], and gold crystals [18,19].
Chemical vapour deposition of volatile organometallic compounds
is widely used for formation of metallic and oxide coatings on dif-
ferent substrates. Depositions on surfaces of solids with highly
developed porous structures are being considered as a valuable
method for the preparation of catalysts with high dispersion of ac-
tive components [10]. Besides that, the MOCVD method allows
effective control of the size of the forming gold particles [10]. How-
precursors for the MOCVD of gold coatings are dimethylgold(III)
b-diketonates [20–22]. On a base of our experience, these com-
plexes are air, moisture and light sensitive, and suffer from poor
stability during storage [23,24]. That’s why the search for and
investigation into alternative precursors of gold MOCVD is an
important problem. Earlier, we investigated dimethylgold(III) car-
boxylates as precursors for the production of gold films. Volatility
and thermal properties of these compounds were studied [25,26].
Salicylaldimine class of ligands have been chosen in reported stud-
ies because of there are some advantages in stabilization of dim-
ethylgold(III) using mixed oxygen nitrogen ligand sphere (N,O-
coordination) [27]. The use of more stable volatile precursors will
allow to improve gold MOCVD procedure. Moreover, the studies
of thermal behavior of gold compounds in solid state and gas
phase, mechanisms of interaction of precursor vapour with hot
surface can be very useful at choosing of MOCVD parameters.
The deposition temperature might be found on the basis of thermal
decomposition of precursor vapour, the evaporator temperature –
from measurements of vapour pressure of precursor. Investigations
of thermal properties and volatility of precursors play an important
role in gold MOCVD development.
* Corresponding author. Address: Nikolaev Institute of Inorganic Chemistry of
Siberian Branch of Russian Academy of Sciences, Lavrentiev Avenue 3, Novosibirsk
630090, Russia. Tel.: +7 383 3309556; fax: +7 383 3309489.
This paper reports the synthesis, structure and thermal proper-
ties of dimethylgold(III) derivatives of salicylaldimine Schiff bases
Me2Au(Sal@N–R), where R = Me (1), Pri (2), or Cy (3). Compounds
E-mail address: bessonov@che.nsk.su (A.A. Bessonov).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.04.028

A.A. Bessonov et al. / Journal of Organometallic Chemistry 693 (2008) 2572–2578
2573
have been characterized by elemental analysis, mass spectrometry,
X-ray, IR, and 1H NMR spectroscopy. Complexes 1 and 3 were de-
scribed earlier [28], but there were not details in structure and
thermal behavior. Dimethylgold(III) salicylaldimine chelates are
air and moisture stable and don’t require special conditions for
storage. The compounds are soluble in most common organic sol-
vents, have low-melting points and evaporate almost quantita-
tively at low temperatures in a vacuum. Our investigations report
that dimethylgold(III) complexes with N-substituted salicylaldi-
mines are viable precursors for MOCVD of gold materials.
The yield of complex 2 was 90%, m.p. 78–79 °C. Dimethyl-
gold(III) N-iso-propyl-salicylaldiminate (2) has been prepared for
the first time. Spectral data for 2: IR (m, cmÀ1) (C–H)(Au–CH3)
2977 m, 2907 m; (C@N) 1624 vs; (C–O) 1174 m, 1150 m, 1127
m. 1H NMR d 0.94 (s, 3H, Au–CH3), d 1.22 (s, 3H, Au–CH3), d 1.35
(d, 6H, CH3), d 4.35 (m, 1H, N–CH), d 6.55–7.40 (4H, ArH), d 8.24
(s, 1H, N@C–H). Anal. Calc. for C12H18AuNO: C, 37.0; H, 4.7; N,
3.6. Found: C, 37.2; H, 4.6; N, 3.6%.
The yield of complex 3 was 85%, m. p. 111–112 °C (lit. data
114 °C [28]). Spectral data for 3: IR (m, cmÀ1) (C–H)(Au–CH3)
2921 s, 2853 m; (C@N) 1618 vs; (C–O) 1189 m, 1143 m, 1128 w.
1H NMR d 0.92 (s, 3H, Au–CH3), d 1.21 (s, 3H, Au–CH3), d 1.35–
2.04 (10H, CH2), d 3.82 (m, 1H, N–CH), d 6.53–7.40 (4H, ArH), d
8.20 (s, 1H, N@C–H). Anal. Calc. for C15H22AuNO: C, 42.0; H, 5.2;
N, 3.3. Found: C, 42.1; H, 5.2; N, 3.4%.
2. Experimental
2.1. General information and materials
Dimethylgold(III) iodide [Me2AuI]2 was prepared from KAuCl4
(P98%) using the method [29]. Salicylaldimines HSal@N–R
(R = methyl, iso-propyl, or cyclohexyl) were synthesized from sali-
cylaldehyde (Fluka, purum, P98%) and alkylamines (Merck, pur-
iss., P99%) by the literature procedure [30]. All reactions were
carried out using Schlenk techniques.
2.3. X-ray crystallography
X-ray powder pattern diffraction data were collected on a
DRON-3M diffractometer using Cu Ka-radiation in 2h angles range
of 5–50° at 296 K. X-ray diffraction data reveal a monophase sys-
tem for complexes 1–3. Single-crystal X-ray studies were per-
Elemental analyses were performed on a Carlo Erba 1106
instrument. IR spectra were recorded in KBr on a FT-IR Scimitar
FTS 2000. 1H NMR spectra were recorded on an MSL Bruker 300
spectrometer; with CDCl3 as solvent. Melting points were deter-
mined by Kofler m.p. apparatus.
The saturated vapour pressure of complexes 1–3 was measured
by the Knudsen effusion procedure combined with mass spectro-
metric analysis of the gas phase composition. Detailed descriptions
of the measurement method, calibration procedure and experi-
mental technique are presented in [31]. The temperature ranges
were 58–87 °C for 1, 48–78 °C for 2, and 65–111 °C for 3. The ther-
modynamic parameters of the sublimation process DHoT and DSTo
have been calculated from the temperature dependencies of satu-
rated vapour pressure.
formed on
a
Bruker-Nonius X8Apex (Mo Ka-radiation)
instrument [32]. Crystals of 1–3 (pale yellow needles) were grown
from the hexanes solution at À10 °C. The structure was determined
using the SHELXTL program and refined using full-matrix least-
squares. All non-hydrogen atoms were refined anisotropically,
whereas hydrogen atoms were placed at the calculated positions
and included in the final stage of refinements with fixed parame-
ters. Crystallographic refinement parameters of complexes 1–3
are summarized in Table 1. The atomic coordinates and selective
bond distances and angles of these complexes are presented in
(Tables 4 and 5 Supplementary material).
2.4. Pulse MOCVD experiments
Mass spectra were obtained on a MI-1201 spectrometer; the en-
ergy of ionizing electrons was 35 eV. The vapour temperature of
the complexes was 70 °C (1), 60 °C (2), and 90 °C (3).
The thermal decomposition process of the vapour of com-
pounds 1 and 2 on a heated surface was studied by means of high
temperature mass spectrometry. The precursors were transferred
to the gas phase at a temperature of 100 °C for 1, and 80 °C for 2.
Detailed descriptions of the method and set-up can be found in
[27].
Scanning electron microscopy (SEM) was carried out using a
JSM-6700F. The morphology of gold nanoparticles samples depos-
ited by pulse MOCVD technique was examined by a Solver Pro (NT-
MDT) atomic force microscope (AFM).
A horizontal hot wall pulse MOCVD system was used for depo-
sitions on silicon substrates. The apparatus for depositions is
drawn schematically in Fig. 1. MOCVD depositions of gold nano-
particles were performed under O2 flow from the precursor 2.
Silicon (100) discs 0.5 mm thick and 40 mm in diameter were used
as substrates. The substrate temperature was controlled in the
190–200 °C range. The base pressure of the reactor was maintained
below 10À2 Torr.
Deposition of gold particles was carried out in the following
cycle manner: (1) The reactor was vacuumed to residue pressure
of 10À2 Torr. (2) The vacuum valve was closed, then the valve on
the line, connecting the vapourizer with the reactor, was opened
and a portion of precursor vapour was injected into the system un-
der the force of saturated vapour pressure. The time of injection
was 5 s. (3) The oxygen valve was opened until the pressure in
the reactor became ꢀ7 Torr. (4) After introduction of oxygen, the
system was kept up for 15 s. Then the vacuum valve was opened
and a new deposition cycle was started.
2.2. Synthesis of complexes
[Me2AuI]2 and NaHCO3 were added to a methanol solution of
the equimolar amount of HSal@N–R. The mixture was stirred in ar-
gon flow at room temperature for 7 h. The methanol was removed
in vacuo and the residue was redissolved in hexane. The hexanes
solution was filtered and the volatile components were removed
in vacuo. The substance was purified by recrystallization from hex-
ane at À10 °C and the pale yellow crystals were formed.
The yield of complex 1 was 84%, m.p. 101–103 °C (lit. data
103 °C [28]). Spectral data for 1: IR (m, cmÀ1) (C–H)(Au–CH3)
2977 m, 2915 m; (C@N) 1633 vs; (C–O) 1188 m, 1152 m, 1124
m. 1H NMR d 1.02 (s, 3H, Au–CH3), d 1.23 (s, 3H, Au–CH3), d 3.63
(s, 3H, N–CH3), d 6.56–7.40 (4H, ArH), d 8.19 (s, 1H, N@C–H). Anal.
Calc. for C10H14AuNO: C, 33.2; H, 3.9; N, 3.9. Found: C, 33.4; H, 4.0;
N, 3.8%.
For deposition of gold nanoparticles, 20 cycles were carried out.
3. Results and discussion
3.1. Synthesis
In paper [28], compounds 1 and 3 were earlier synthesized from
thallium salts of salicylaldimines and [Me2AuI]2 with 62% and 52%
yields accordingly. We offered a modified procedure with N-alkyl-
salicylaldimine as ligand source. The synthetic method, including
reaction of [Me2AuI]2 with the corresponding HSal@N–R, gives

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A.A. Bessonov et al. / Journal of Organometallic Chemistry 693 (2008) 2572–2578
Table 1
Crystal data and structure refinement parameters for complexes 1, 2 and 3
1
2
3
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
A (Å)
B (Å)
C (Å)
a (°)
b (°)
C
10H14AuNO
C12H18AuNO
389.25
100(2)
C15H22AuNO
429.30
150(2)
Monoclinic
P21/c
11.8472(4)
8.9313(2)
14.2890(5)
90
106.788(1)
90
1447.49(8)
4
1.970
10.152
361.19
150(2)
Rhombic
Aba2
16.016(3)
18.656(4)
6.961(1)
90
90
90
2080.0(7)
8
2.307
Triclinic
ꢀ
P1
7.142(1)
8.896(2)
10.259(2)
109.36(3)
93.69(3)
96.32(3)
607.7(2)
2
c (°)
Volume (Å3)
Z
DCalc (g/cm3)
Absorption coefficient (mmÀ1
F(000)
2.122
12.079
366
)
14.106
1344
824
Crystal size (mm)
Crystal color
H Range (°)
Index ranges
Reflections collected
0.70 Â 0.22 Â 0.18
Pale yellow
3.35–32.60
0.26 Â 0.08 Â 0.05
Pale yellow
2.12–28.33
0.05 Â 0.30 Â 0.04
Pale yellow
2.72–27.47
À24 6 h 6 20, À28 6 k 6 27, À10 6 l 6 6 À9 6 h 6 9, À11 6 k 6 11, À13 6 l 6 13 À15 6 h 6 14, À76 k 6 11, À17 6 l 6 18
10574
5264
10756
Independent reflections [Rint
Data/restraints/parameters
Goodness-of-fit on F2
]
3162 [0.0268]
3162/1/131
1.044
4540 [0.0180]
4540/143/290
1.106
3318 [0.0218]
3318/0/229
1.030
Final R indices [I > 2r(I)]
R1 = 0.0164
wR2 = 0.0366
R1 = 0.0194
wR2 = 0.0372
R1 = 0.0496
wR2 = 0.1365
R1 = 0.0541
wR2 = 0.1400
8.645 and À2.344
R1 = 0.0192
wR2 = 0.0448
R1 = 0.0233
wR2 = 0.0459
1.666 and À0.765
R indices (all data)
Largest difference in peak and hole (e/Å3) 1.273 and À1.611
Fig. 1. Scheme of pulse MOCVD apparatus.
the products Me2Au(Sal@N–R). This method allows removal of the
stage of production of thallium derivatives of salicylaldimines.
With our method, yields of products were 84–90%. It should be
noted that compound 2 was synthesized and characterized for
the first time.
have a slightly distorted square-planar configuration formed by
oxygen and nitrogen atoms of salicylaldimine ligand and two car-
bon atoms of methyl groups. The average Au–O bond in 1 (2.082 Å)
is longer than similar bonds found in 2 (2.075 Å) and 3 (2.071 Å),
while the average Au–N distances (2.118 Å) are slightly smaller
than in 2 (2.125 Å) and 3 (2.124 Å) (Table 2). Au–CH3 bond length
is typical for dimethylgold(III) derivatives – 2.039 and 2.031 Å for 1
and 3 accordingly [34] although in one of the independent com-
plexes, 2, this value is larger (2.070 Å) (Table 2). Angle °AuN in
complexes 1 and 2 has the same value (91.2°), while in 3 this angle
is 90.6°. Molecules of 1 are planar with accuracy of 0.027 Å (with
the exception of hydrogen atoms of methyl groups). Crystal mole-
cules are packed in infinite stacks along the Z axis with AuÁ Á ÁAu
3.2. X-ray single crystal structure
The compounds’ structures are molecular, formed from neutral
molecules (CH3)2Au(Sal@N–R). The crystal structure of relative
compound, dimethylgold(III) N-phenylsalicylaldiminate (R = phe-
nyl), was published earlier [33]. Structures of complexes 1, 2 and
3 are shown in Figs. 2–4, correspondingly. Gold atoms in molecules

A.A. Bessonov et al. / Journal of Organometallic Chemistry 693 (2008) 2572–2578
2575
pyl hydrogens. AuÁ Á ÁAu distance between neighbour molecules in
stack is 3.835 Å. Molecules of complex 3, with the exception of
atoms of cyclohexyl ring, are also planar with accuracy of
0.014 Å. AuÁ Á ÁAu distance between neighbour molecules is
4.660 Å. Increasing of AuÁ Á ÁAu distance in the unit cell of 3 in com-
parison with 1 and 2 is going on due to insertion of more large sub-
stituents in the ligand (Table 2).
Distances between centres of stacks in 1 are >7.75 Å, the short-
est intermolecular distances HÁ Á ÁH in the crystal are about 2.40 Å.
In complex 2, intermolecular interactions °Á Á ÁH type in stacks are
estimated as 2.53–3.37 Å. The structure of 3 has a lamellar charac-
ter; molecules are packed in layers (100) with distances of 11.34 Å
to each other. °Á Á ÁH distances between molecules 3 are equal to
2.52 and 3.53 Å.
So, by X-ray data it is shown that changing of the alkyl substi-
tuent at the nitrogen atom in dimethylgold(III) salicylaldimine
chelates provides minimal influence on the geometry of coordina-
tion centre and closest bond distances. Although the character of
packing of molecules in crystal varies, it has an influence on the
thermal properties of complexes. Insertion of larger substituents
decreases the compound density (Table 2) and increases distances
between gold atoms of neighbour molecules in stacks. In Table 2,
some comparative crystallographic parameters and geometric
characteristics of complexes 1–3 are shown.
Fig. 2. Plot of complex 1 showing the atom numbering scheme for the core atoms.
3.3. Mass spectra
Analysis of mass spectra has shown that vapour of compounds
1–3 consists of molecular forms. The main ions in mass spectrum
of
1 –
[Me2AuSal@N–Me]+ (Irel = 43%) and [AuSal@N–Me]+
(Irel = 100%); 2 – [Me2AuSal@N–Pri]+ (Irel = 52%) and [AuSal@N–
Pri]+ (Irel = 100%); 3 – [Me2AuSal@N–Cy]+ (Irel = 34%), [AuSal@N–
Cy]+ (Irel = 100%), and [Sal@N–Cy]+ (Irel = 15%). The same data were
observed for salicylaldimine class of ligands earlier [28]. The pro-
cess of fragmentation of molecular ions is similar for all com-
pounds. The molecular ion becomes a fragment after elimination
of methyl groups and the ligand.
Fig. 3. Plot of complex 2 showing the atom numbering scheme for the core atoms.
In the investigated temperature ranges (58–87 °C for 1,
48–78 °C for 2, and 65–111 °C for 3), the relative intensity of the
ion peaks in the mass spectra of complexes 1–3 remains un-
changed. This evidences that the vapours of complexes are ther-
mally stable in these temperature ranges.
3.4. Volatility studies
The Knudsen effusion procedure with mass spectrometric anal-
ysis of the composition of gas phase was used to measure the tem-
perature dependencies of the saturated vapour pressure (P–T
dependencies) of complexes 1–3 (Fig. 5). Based on the P–T depen-
dencies, the thermodynamic parameters of the sublimation pro-
cess were calculated (Table 3). Temperature dependences of
vapour pressure are presented in Fig. 5, and thermodynamic data
as the equation lg(P, Torr) = A À B/(T, K), DHoT and DSTo are shown
in Table 3. Statistical processing of the experiments was based on
the vapour pressure measured at several values of temperature.
The P–T curves show that compound 2 is the most volatile in the
investigated temperature range. Substitution of the methyl group
in 1 by cyclohexyl in the salicylaldimine ligand (compound 3) causes
a decrease of the volatility within the studied temperature range
(Fig. 5). Complex 3 has considerably lower volatility than 1 and 2.
Such a difference is likely to be connected with the effects of crystal
packing of the complexes. The volatility row of investigated dimeth-
ylgold(III) complexes with salicylaldimine Schiff bases is (for
P = 10À3 Torr): 2 (61 °C) > 1 (70 °C) > 3(96 °C) (Table 3, Fig. 5).
We compared vapour pressure of complexes 1–3 and other
dimethylgold(III) precursors used for gold MOCVD (Fig. 5):
Fig. 4. Plot of complex 3 showing the atom numbering scheme for the core atoms.
distance of 3.492 Å and AuAuAu angle of 170.6°. The angle between
normal to the plane of molecule 1 and stack axis is 12.2°. Molecules
2 are planar with accuracy of 0.084 Å, with the exception of isopro-

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A.A. Bessonov et al. / Journal of Organometallic Chemistry 693 (2008) 2572–2578
Table 2
Compared X-ray characteristics of complexes 1, 2 and 3
Complex
V/Z (Å3)
qmeas (g/cm3)
d (Å)
Au–O
Au–N
Au–C(Me)
AuÁ Á ÁAu in layer
N–C(R)
1
2
3
260.0
303.8
361.9
2.307
2.122
1.970
2.082
2.075
2.071
2.118
2.125
2.124
2.039
2.050
2.031
3.492
3.835; 4.570
4.660
1.469
1.490
1.487
200
180
160
140
120
100
80
Temperature,˚C
127
0.0
112
97
84
72
60
50
40
30
21
1
b
c
6
-0.5
-1.0
-1.5
-2.0
5
10-1
10-2
10-3
10-4
10-5
a
4
d
e
7
8
-2.5
-3.0
-3.5
-4.0
-4.5
-5.0
60
40
2
1
20
3
0
100
120
140
160
180
200
220
240
260
2.5
2.6
2.7
2.8
2.9
3.0
3.1
3.2
3.3
3.4
Temperature,˚C
1000/(T, K)
Fig. 6. Temperature dependence of intensities of ion peaks at decomposition of 1
vapour; main ions: (a) – [AuSal@N–Me]+ (331 m/z), (b) – [CH2Sal@N–Me]+ (148 m/z),
(c) – [HSal@N–Me]+ (135 m/z), (d) – [C2H5Sal@N–Me]+ (163 m/z), (e) – [Sal@N–Me]+
(134 m/z).
Fig. 5. Temperature dependencies of saturated vapour pressure for (1) – Me2Au-
(Sal@N–Me), (2) – Me2Au(Sal@N–Pri), (3) – Me2Au(Sal@N–Cy), (4) – Me2Au(ba)
[10], (5) – Me2Au(tta) [35], (6) – Me2Au(bfa) [36], (7) – Me2Au(kaa) [10], and (8) –
Me2Au(acac) [10].
140
b
120
Me2Au(ba) (4)
– dimethylgold(III) 1-phenyl-1,3-butanedionate
(Knudsen method) [10], Me2Au(tta) (5) – dimethylgold(III) 1,1,1-
trifluoro-4-(2-thienyl)-1,3-butanedionate (flow method) [35],
Me2Au(bfa) (6) – dimethylgold(III) 1,1,1-trifluoro-4-phenyl-1,3-
butanedionate (flow method) [36], Me2Au(kaa) (7) – dimethyl-
gold(III) 2-imino-4-pentaneonate (Knudsen method) [10], and
Me2Au(acac) (8) – dimethylgold(III) 2,4-pentanedionate (Knudsen
method) [10]. Complexes 1 and 2 reveal volatility similar to 5
and 6 (Fig. 5). Precursors 7 and 8 are more volatile compounds than
1 and 2 in the studied temperature ranges. Complex 3 has vapour
pressure close to 4 (Fig. 5). Thus, dimethylgold(III) salicylaldimine
chelates show sufficient volatility for their applications as MOCVD
precursors.
100
a
80
c
60
40
d
20
e
0
100
120
140
160
180
200
220
Temperature,˚C
3.5. Thermal decomposition
Fig. 7. Temperature dependence of intensities of ion peaks at decomposition of 2
vapour; main ions: (a) – [AuSal@N–Pri]+ (359 m/z), (b) – [Sal@N–C2H5]+ (148 m/z),
(c) – [HSal@N–Pri]+ (163 m/z), (d) – [CH2Sal@N–Pri]+ (177 m/z), and (e) – [C2H5-
Sal@N–Pri]+ (191 m/z).
Thermolysis of vapour of complexes 1 and 2 on hot surface as
more volatile and perspective MOCVD precursors was studied in
a vacuum by high temperature mass spectrometry (Figs. 6 and
7). From the analysis of temperature dependences of relative inten-
sities of main ion peaks in mass spectra of thermolysis products,
the temperatures of beginning of decomposition of complexes in
gas phase were determined. In our experimental conditions,
thermodecomposition of molecules in gas state on heated surface
is started at a temperature higher than 120 5 °C for 1 and
110 5 °C for 2 (Figs. 6 and 7). Exchange of methyl group of salicyl-
Table 3
Thermodynamics parameters of sublimation processes of complexes 1–3
Complex
m.p. (°C)
Number of points
lg(P, Torr) = A À B/(T, K)
Temperature range (°C)
DHoT (kJ molÀ1
)
DSoT (J molÀ1 KÀ1
)
A
B Â 10À3
1
2
3
101–103
78–79
111–112
4
5
9
15.9 0.1
15.6 0.4
16.9 0.3
6.48 0.04
6.21 0.14
7.35 0.12
58–87
48–78
65–111
123.9 0.8
118.8 2.7
140.6 2.2
250.0 1.9
243.2 7.6
268.1 5.7

A.A. Bessonov et al. / Journal of Organometallic Chemistry 693 (2008) 2572–2578
2577
aldimine ligand in 1 to iso-propyl results in decreasing of the
temperature of beginning of decomposition of complex 2 vapour.
The main volatile organic products of thermolysis of complex 1
are HSal@N–Me, MeSal@N–Me, and EtSal@N–Me. Thermodecom-
position products of vapour of compound 2 have similar composi-
tion: HSal@N–Pri, MeSal@N–Pri, and EtSal@N–Pri. The data
obtained provide arguments about the same scheme of thermode-
composition of vapour of complexes 1 and 2 on hot surface. It was
suggested as:
thermodecomposition, oxygen as co-precursor does not affect the
mechanism of decomposition of the precursor on the surface of
substrate, but allows decreasing of the carbon content as impuri-
ties. We selected complex 2 as the precursor simply because of
its higher volatility and lower melting point. Parameters of MOCVD
experiments were selected on the basis of analysis of volatility data
and thermal properties of the precursor. The temperature of Si
substrate in the range 190–200 °C was selected on the basis of
thermodecomposition data of complex 2 vapour (in this range
CH3
O
Au CH3
O
N
CH3
C
H
R
N
R
C
H
CH2
CH3
O
CH3
CH3
CH3
Au
N
O
O
O
- Auads
O
C2H5
Δ
Au CH3
Au CH3
Au CH3
gas
C
H
R
N
R
N
R
N
R
N
R
C
H
C
H
C
H
C
H
O
ads
ads
gas
O
H
N
N
R
C
H
R
R = CH3, CH(CH3)2
C
H
H3C
H3C
Au
ads
Among the main products of thermolysis of complexes, there are
salicylaldimine Schiff bases and their derivatives. This indicates the
consecutive cleavage of methyl groups and ligand with the forma-
tion of metal gold. The methyl groups migrate from gold to ligand
in adsorbed state on surface. For other dimethylgold(III) derivatives
it was observed a formation of ethane at thermodecomposition of
vapour [25,27]. Besides that, in solution Me2Au(acac) also decom-
poses with loss of ligand and methyl groups, which is indicated
by the presence of ethane and acetylacetone among the main prod-
ucts of decomposition [37]. In case salicylaldimine derivatives C2H6
was not found among volatile organic products of thermolysis.
Change of the relative intensity of gold-containing ion peak
[AuSal@N–Me]+ for 1 (Fig. 6a) and [AuSal@N–Pri]+ for 2 (Fig. 7a) al-
lows us to trace the decomposition rate of precursor vapours. In
such experimental conditions, complex 1 demonstrates a lower
rate of thermolysis than 2 (Figs. 6 and 7). Gold-containing frag-
ments are absent among the decomposition products of complex
2 even at 210 5 °C: in the case of precursor 1 this is only at
260 5 °C (Figs. 6 and 7). So, thermodecomposition of vapour
phase of complex 2 occurs more quickly. Introduction of oxygen
into the reactor does not lead to substantial change of the decom-
position mechanism and kinetics of the process. Oxidation of the
decomposition product was observed, and results in the absence
of carbon in thermolysis products.
there is absence of gold-containing ions in mass spectra, Fig. 7).
The size of deposited gold particles alters in the range of 5–
15 nm, as was measured by the SEM and AFM technique (Figs. 8
and 9). As shown in Figs. 8 and 9, gold nanoparticles were depos-
ited with even distribution on the surface of silicon substrate. A
further increase in the temperature to 210 °C results in further
increase of particle concentration on the surface. Particle size is
also about 10 nm.
3.6. Pulse MOCVD depositions
The MOCVD experiments were conducted on a horizontal hot
wall reactor using complex 2 as the gold source reagent and
oxygen as a co-precursor. As was shown in the investigation of
Fig. 8. SEM of gold nanoparticles deposited on Si substrate at 190–200 °C.

2578
A.A. Bessonov et al. / Journal of Organometallic Chemistry 693 (2008) 2572–2578
Appendix A. Supplementary material
CCDC 678139, 678140 and 678141 contain the supplementary
crystallographic data for 1, 2 and 3. These data can be obtained free
of charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif. Supplementary data associ-
ated with this article can be found, in the online version, at
doi:10.1016/j.jorganchem.2008.04.028.
References
[1] J. Kashammer, P. Wohlfart, J. Weiß, C. Winter, R. Fischer, S. Mittler-Neher, Opt.
Mater. 9 (1998) 406–410.
[2] L. Armelao, D. Barreca, G. Bottaro, A. Gasparotto, S. Gross, C. Maragno, E.
Tondello, Coord. Chem. Rev. 250 (2006) 1294–1314.
[3] I.C.S. Carvalho, F.P. Mezzapesa, P.G. Kazansky, O. Deparis, M. Kawazu, K.
Sakaguchi, Mater. Sci. Eng. C 27 (2007) 1313–1316.
[4] Y.-F. Lu, M. Takai, S. Nagamoto, K. Kato, S. Namba, Appl. Phys. A 54 (1992) 51–
56.
[5] M. Jubber, J.I.B. Wilson, J.L. Davidson, P.A. Fernie, P. John, Appl. Surf. Sci. 43
(1989) 74–80.
[6] T.H. Baum, P.B. Comita, Thin Solid Films 218 (1992) 80–94.
[7] T.T. Kodas, M.J. Hampden-Smith, The Chemistry of Metal CVD, VCH, Weinheim,
New York, Basel, Cambridge, Tokyo, 1994.
[8] C. Schoßler, A. Kaya, J. Kretz, M. Weber, H.W.P. Koops, Microelectron Eng 30
(1996) 471–474.
Fig. 9. AFM of gold nanoparticles deposited on Si substrate at 190–200 °C.
[9] M. Okumura, K. Tanaka, A. Ueda, M. Haruta, Solid State Ion. 95 (1997) 143–149.
[10] P.P. Semyannikov, B.L. Moroz, S.V. Trubin, G.I. Zharkova, P.A. Pyryaev, M.Yu.
Smirnov, V.I. Bukhtiyarov, J. Struct. Chem. 47 (2006) 458–464.
[11] M. Haruta, Catal. Today 36 (1997) 153–166.
4. Conclusions
[12] G.J. Hutchings, Catal. Today 72 (2002) 11–17.
This study shows that dimethylgold(III) complexes with salicyl-
aldimine Schiff bases are viable MOCVD precursors to gold materi-
als. These compounds are stable during storage and have a good
volatility. On the basis of X-ray data, it is shown than exchange
of substituent at donor nitrogen atom in ligand have great impact
on the character of packing and so on resulting in differences of
thermal properties. Thus, complex 2 has the highest volatility
among the presented compounds, while the introduction of cyclo-
hexyl in molecules dramatically decreases the volatility. Besides,
vapour of complex with iso-propyl group has lesser thermal stabil-
ity in comparison with N-methylsubstituted salicylaldiminate
although mechanism and by-products of thermolysis are similar.
So, introduction of various substituents in ligand of dimethyl-
gold(III) complex allows modifying of thermal properties and vol-
atility of compounds in a wide range.
Dimethylgold(III) derivatives of salicylaldimine Schiff bases can
be used in gold MOCVD at deposition temperatures lower than
200 °C with better mass transport properties and thermal behavior
than used gold b-diketonates derivatives. Although optimization of
the deposition conditions and investigation of obtained gold mate-
rials will be necessary in the future, the thermal behavior and vol-
atility characteristics of precursors make them attractive
candidates for gold MOCVD processes.
[13] M. Valden, X. Lai, D.W. Goodman, Science 281 (1998) 1647–1650.
[14] M. Haruta, M. Date, Appl. Catal. A: Gen. 222 (2001) 427–437.
[15] M.S. Chen, D.W. Goodman, Science 306 (2004) 252–255.
[16] U. Hiroto, S. Noriyasu, S. Masamitsu, T. Masatuki, O. Katsumi, JP 06-101046,
Mitsubishi Materials Corp., 1994, Appl. No. 04-274966.
[17] H. Masataka, EP 0571713A2, Fujitsu Limited 1993, Appl. N 931023808.
[18] T.H. Baum, C.R. Jones, J. Vac. Sci. Technol. B 4 (1986) 1187–1191.
[19] T.T. Kodas, T.H. Baum, P.B. Comita, J. Cryst. Growth 87 (1988) 378–382.
[20] T.H. Baum, C.R. Jones, Appl. Phys. Lett. 47 (1985) 538–540.
[21] C.E. Larson, T.H. Baum, R.L.J. Jackson, Electrochem. Soc. 134 (1987) 266.
[22] E. Feurer, H. Suhr, Appl. Phys. A44 (1987) 171–175.
[23] G.I. Zharkova, I.K. Igumenov, S.V. Zemskov, Koord. Khim. 6 (1980) 720–723.
[24] G.I. Zharkova, G.I. Tyukalevskaya, I.K. Igumenov, S.V. Zemskov, Koord. Khim. 14
(1988) 1362–1367.
[25] A.A. Bessonov, I.A. Baidina, N.B. Morozova, P.P. Semyannikov, S.V. Trubin, N.V.
Gelfond, I.K. Igumenov, J. Struct. Chem. 48 (2007) 282–288.
[26] A.A. Bessonov, N.B. Morozova, N.V. Gelfond, P.P. Semyannikov, S.V. Trubin,
Yu.V. Shevtsov, Yu.V. Shubin, I.K. Igumenov, Surf. Coat. Technol. 201 (2007)
9099–9103.
[27] P.P. Semyannikov, V.M. Grankin, I.K. Igumenov, G.I. Zharkova, J. Phys. IV 5
(1995) 213–220.
[28] K.S. Murray, B.E. Reichert, B.O. West, J. Organomet. Chem. 61 (1973)
451–456.
[29] A.A. Bessonov, N.B. Morozova, N.V. Kuratieva, I.A. Baidina, N.V. Gelfond, I.K.
Igumenov, Russ. J. Coord. Chem. 34 (2008) 70–77.
[30] M. Dennstedt, J. Zimmermann, Chem. Ber. 21 (1888) 1553–1554.
[31] P.P. Semyannikov, I.K. Igumenov, S.V. Trubin, T.P. Chusova, Z.I. Semenova,
Thermochim. Acta 432 (2005) 91–98.
[32] Bruker AXS Inc., APEX2 (Version 1.08), SAINT (Version 7.03), SADABS (Version 2.11)
and SHELXTL (Version 6.12), Bruker Advanced X-ray Solutions, Madison,
Wisconsin, USA, 2004.
[33] A.A. Bessonov, A.I. Smolentsev, I.A. Baidina, N.B. Morozova, Acta Crystallogr.
E63 (2007) m3154.
Acknowledgements
[34] S. Shibata, K. Lijima, T.H. Baum, J. Chem. Soc., Dalton Trans. (1990)
1519–1520.
[35] U. Hiroto, S. Noriyasu, S. Masamitsu, O. Katsumi, JP 05-320170. Mitsubishi
Materials Corp., 1993, Appl. No. 04-274929.
[36] U. Hiroto, S. Noriyasu, S. Masamitsu, T. Masayuki, O. Katsumi, JP 05-331176.
Mitsubishi Materials Corp. 1993, Appl. 1 04-274967.
[37] R.B. Klassen, T.H. Baum, Organometallics 8 (1989) 2477–2482.
The authors thank the Russian Science Support Foundation for
financial support. Anton I. Smolentsev provided technical assis-
tance with the crystal structure determinations. SEM and AFM
analyses were carried out by Dr. V.S. Danilovich and N.G.
Semerikov.