Studies of thermal decomposition of palladium(II) complexes with olefin ligands

Article abstract of DOI:10.1016/j.tca.2009.06.002

PdCl₂(VTMS)₂ (1)_, PdCl₂(PTMSA)₂ (2), PdCl₂(DMB)₂ (3) and PdCl₂(DADMS)₂ (4), where VTMS-trimethyl(vinyl)silane, DADMS-diallyldimethylsilane, PTMSA-1-phenyl-2

Full text of DOI:10.1016/j.tca.2009.06.002

Thermochimica Acta 495 (2009) 85–89
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Studies of thermal decomposition of palladium(II) complexes with olefin ligands
E. Szłyk∗, M. Barwiołek
Nicolaus Copernicus University, Faculty of Chemistry, 87 100 Torun´, xxx, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
PdCl2(VTMS)2 (1), PdCl2(PTMSA)2 (2), PdCl2(DMB)2 (3) and PdCl2(DADMS)2 (4), where VTMS–
trimethyl(vinyl)silane, DADMS—diallyldimethylsilane, PTMSA—1-phenyl-2-(trimethylsilyl)acetylene and
DMB–2,3-dimethyl-2-butene were prepared and thermal characteristic studied by TG/DTG/DTA tech-
niques. TG/IR method was used for the gas phase studies of ligands and complexes in the range 303–573 K.
MS–EI analysis data were applied for elucidation of the metallated species in the gas phase. Thermal anal-
ysis results indicate detachment of organic ligand in the first stage of decomposition, whereas the chlorine
molecule in the second stage. Metallic palladium was the final product of decomposition, what was con-
firmed by XRD analysis of the residues heated up to 1273 K. The metallic palladium was formed in the
temperature range 478–720 K, what make the complexes (1–4) a promising Chemical Vapour Deposition
(CVD) precursors. TG/IR spectra of all palladium(II) complexes revealed bands characteristic for appro-
priate ligands vibrations, what confirm the proposed mechanism of thermal decomposition. The MS
results indicate the palladium fragments detachment in the temperature range 321–548 K. The organic
and chlorine species were also observed.
Received 19 February 2009
Received in revised form 23 April 2009
Accepted 5 June 2009
Available online 16 June 2009
Keywords:
Palladium(II) compounds
Olefin ligands
TG/DTA/DTG
TG/IR
VT–MS
© 2009 Elsevier B.V. All rights reserved.
1. Introduction
other palladium(II) complexes with different allyl ligands e.g.
ethylene, butane, pentene, cyclooctene, styrene, isobutylene and
Palladium as a metal or silver–palladium powder pastes is
widely applied in production of many electronic components
such as diodes, transistors, integrated or hybrid circuits, mul-
tilayer ceramic capacitors, thick film resistors and conductors.
Silver–palladium alloys are employed for electrical contacts, relays
and switching systems in telecommunication equipment. Besides
that palladium layers are present in gas sensing electrodes, fil-
ters for hydrogen purification and, whereas complexes are used in
catalysis of many chemical processes. [1–9] Palladium in a form of
metallic layers can be prepared also by Chemical Vapour Deposition
(CVD) of volatile coordination or organometallic precursors. [8] The
part of search for CVD precursors must be focused on their thermal
properties, which are important for CVD operational parameters
and selection of the most promising precursor. Besides that data
from the thermal studies are used for determination of the pre-
cursors vaporization temperature, conditions of the transport in
the gas phase, and the decomposition mechanism on a substrate
surface.
cyclohexene were characterized structurally. [13] These com-
plexesrevealeddimericstructureswith␲-bondedolefinmolecules,
whereas in palladium(II) acetylene complexes, an alkine lig-
ands were coordinated asymmetrically via triple bond. [14,15]
For CVD purposes MS spectra of many palladium(II) allylic com-
plexes were analyzed in search for metallated volatile particles
and many of them revealed the lack of such fragments. [16,17]
In the MS spectra of di-␮-chlorodiallylpalladium(II) and di-
␮-chlorodi(4-methoxy-1-methylpent-2-enyl)dipalladium(II) com-
plexes, fragments with palladium and chlorine atoms were
registered. [18–20] These properties suggest their future usage
as precursors for CVD of palladium layers. Moreover thermal
studies of the latter complexes suggested three stages decom-
position mechanism resulting in metallic palladium. [14,16] To
the best of our knowledge, the thermal properties of pal-
ladium(II) complexes with sillylated olefin ligands have not
been studied. Our previous studies suggested, that the pres-
ence of trimethylsillyl group improves the complex volatility.
[18,19] Therefore the purpose of this work was to study the
thermal properties of new Pd(II) complexes with the follow-
ing olefin ligands: 2,3-dimethyl-2-butene (DMB), 1-phenyl-2-
(trimethylsilyl)acetylene (PTMSA), diallyldimethylsilane (DADMS),
trimethylvinylsilane (VTMS), which can be tested as CVD precur-
sors. Volatile species evolved during thermal decomposition will be
characterized by TGA–IR and mechanism of decomposition process
will be discussed.
Palladium(II) dimeric precursors with bridging (␩3-allyl) lig-
ands: Pd(␩3-methyl-2-allyl)(acac); (acac-acetylacetone), [Pd(␩3-
methyl-2-allyl)Cl]2 or Pd(␩3-allyl)(hfacac); (hfacac-hexafluoro-
acetylacetone) have been used for CVD. [10–12] Besides that,
∗
Corresponding author. Tel.: +48 56 611 43 04, fax: +48 56 654 24 77.
E-mail address: eszlyk@chem.umk.pl (E. Szłyk).
0040-6031/$ – see front matter © 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.tca.2009.06.002

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E. Szłyk, M. Barwiołek / Thermochimica Acta 495 (2009) 85–89
2. Experimental
2.1. Materials
Results of spectroscopic and analytical data for new complexes
isolated in that way are listed below.
2.3.2.1. PdCl2(VTMS)2 (1). Elemental analysis calc/found
% for
PdCl2, inorganic salts and solvents of analytical grade were
purchased from POCh Gliwice (Poland), whereas trimethyl(vinyl)
silane–(CH3)3SiCHCH2 (VTMS)–97%, diallyldimethylsilane–CH2
CHCH2)2Si(CH3)2 (DADMS)–98%, 1-phenyl-2-(trimethylsilyl)ace-
tylene–C6H5C≡CSi(CH3)3 (PTMSA)–97%, 2,3-dimethyl-2-butene–
(CH3)2C C(CH3)2 (DMB)–98% from Aldrich.
C10H24Cl2Si2Pd: C 31.62/31.9, Pd 28.01/27.68, H 6.40/6.67; MS:
(T = 474 K, m/z) [CSi(CH3)]+ (57) R.I. 100%, Cl2 (71) R.I. 78%,
[Pd[(CH3)3SiCH CH]]+ (207) R.I. 44%, [PdCl[[(CH3)3Si]+ (221) R.I.
40%; 1H NMR (benzene-d6, ppm) 7.2 (HCCSi), 6.1, 6.8 (HC C), 0.08
(CH3);13CNMR(benzene-d6, ppm)142.1(HCSi);127.9(CH2), −0.38,
−1.4, −2.3 (CH3); IR (cm−1) 3075, 3047 ꢀ( CH2), 1511, 1540 ꢀ(C C),
848 ꢀ(Si C), 398, 365 ꢀ(Pd Cl). [21–25]
2.2. Instrumentation
2.3.2.2. PdCl2(PTMSA)2 (2). Elemental analysis calc/found % for
Thermal analysis (TG, DTG, DTA) was performed on a SDT 2960
TA analyzer. Decomposition processes were studied in a dynamic
atmosphere of dry nitrogen flowing at 60 ml/min, heating rate
5 ◦/min and heating range up to 1273 K, or heating rate 2.5 ◦/min,
and heating range up to 723 K. Samples (4–11 mg) were placed in
platinum crucible and measured against reference material–Al2O3.
Gaseous products of the thermal decomposition were detected by
a FT IR Bio–Rad Excalibur spectrometer equipped with a TA ana-
lyzer equipment, heated to 493 K, for gases evolved from a SDT 2960
TA analyzer. Powder X-ray diffraction data for residues of the ther-
mal analysis were obtained with a Philips X’PERT diffractometer
using Cu K␣ radiation. Variable temperature mass spectra (VT–MS)
were measured in the temperature range 303–573 K with a Finni-
gan MAT 95 mass spectrometer using EI technique. 1H and 13C
NMR spectra in benzene-d6 were collected with a Varian Gemini
200 MHz spectrometer using TMS as the standard. IR spectra in the
range 4000–400 cm−1 were recorded on a PerkinElmer 2000 FT IR
spectrometer using KBr discs. Palladium was determined gravimet-
rically, after complex mineralization, whereas C, H, by elemental
analysis performed on Vario Macro CHN Elementar Analysensys-
teme GmbH. [17]
Cl2C22H28Si2Pd: C 50.23/50.81, Pd 20.23/20.6, H 5.36/5.42; MS:
(T = 321 K, m/z) [Si(CH)3]+ (73) R.I. 44%, [PdSi(CH3)3]2 (315) R.I.
+
7%, [PdSiC]+ (147) R.I. 98% [C6H5CCH2]+ (103) R.I. 100%; 1H NMR
(benzene-d6, ppm) 7.30, 7.36, 7.49 (CHaromatic), 0.07 (CH3), 13C NMR
(benzene-d6, ppm) 131, 127, 121 (CHaromatic), 96 (C≡CSi), 50 (CSi),
3.2 (CH3); IR (cm−1) 2963 ꢀ(CH3), ꢀ(CHaromatic), 1986 ꢀ(C≡C), 851
ꢀ(Si C), 332, 354 ꢀ(Pd Cl). [21–25]
2.3.2.3. PdCl2(DMB)2 (3). Elemental analysis calc/found
% for
Cl2C12 24Pd: 41.69/41.2., Pd 30.78/30.5, 6.99/6.38; MS:
H
C
H
(T = 548 K, m/z) [C4H9]+ (57) R.I. 100%, Cl2 (71) R.I. 62%,
[PdC4H6Cl]+ (195) R.I. 34%, [PdCl[(CH3)2C C(CH3)H]]+ (212) R.I.
79%, [Pd3[(CH3)2C C(CH3)2]2] (487) R.I. 10%; 1H NMR (benzene-
d6, ppm) 2.2. (CH3); 13C NMR (benzene-d6, ppm) 128 (C C), 23
(CH3); IR (cm−1) 2996 ꢀ(CH3), 1510, 1540 ꢀ(C C), 311, 354 ꢀ(Pd Cl).
[21–25]
2.3.2.4. PdCl2(DADMS)2 (4). Elemental analysis calc/found % for
Cl2C16H32Si2Pd: C 41.96/42.21, Pd 23.23/24.56, H 7.04/7.47; MS:
(T = 389 K, m/z) [CH2 CH CH2]+ (41) R.I. 38%, Cl2 (71) R.I. 58%,
[Si(CH)3]+ (73) R.I. 35%, [CH2CHCHCH2Si(CH3)3]+ (99) R.I. 40%,
[PdCH2CHCH2]+ (173) R.I. 72%, [Pd(CH2CHCH2)SiH(CH3)2]+ (207)
R.I. 63%, [PdCl2]+ (247) R.I. 38%. [Pd2CH2CHCH2Si]+. (369) R.I. 41%;
1H NMR (benzene-d6, ppm) 7.30, 7.36, 7.49 ( CH), 0.07 (CH3),
13C NMR (benzene-d6, ppm) 134 (CH), 113 (CH2), 22 (CH2), −4.2
(SiCH2); IR (cm−1) 3016, 3049 ꢀ( CH2), 1510 ꢀ(C C), 885 ꢀ(Si C),
398, 343 ꢀ(Pd Cl) [21–25].
2.3. Synthesis
2.3.1. Synthesis of dichlorobis(benzonitrile)palladium(II)
(PdCl2(C6H5CN)2)
Bezonitrile 20 ml (0.2 mol) was added to 0.5 g (2.82 mmol) of
palladium(II) chloride. The reaction mixture was heated (T = 383 K),
stirred for 2 h and filtered. Next, 80 ml petroleum ether at room
temperature was added to the filtrate and the yellow precipi-
tate was isolated and washed with petroleum ether. [13,20] 1H
NMR (benzene-d6, ppm) 7.3–7.5 (C6H5), 13C NMR (benzene-d6,
ppm) 112 (CCN), 116 (CN), 129, 132, 133 (C6H5). IR (cm−1) 2230
ꢀ(CN), 1492 ꢀ(C Caromatic), 1449 ꢀ(C Caromatic), 768 ꢀ(CHaromatic),
648 ꢀ(CHaromatic), 388, 358 ꢀ(Pd Cl).
3. Results and discussion
3.1. Thermal analysis
Thermal properties of the studied compounds are important for
the assessment of their usage in CVD of palladium layers. The onset
of decomposition process and temperature of metallic palladium
formation are the two factors which determine CVD procedure
parameters, hence these are determined by analysis of thermoan-
alytical curves. Results of DTA, TG and DTG curves analysis for two
sets of thermograms registered up to 773 K and 1273 K are listed in
Table 1.
DTA curve of complex (1) revealed two endothermic effects over
298–343 K and 398–463 K (Fig. 1, heating range 773 K), whereas
third one exhibit slightly marked endothermic process (max. 682 K)
and mass loss 11.1% on TG curve.
Analysis of the DTG curve indicates three processes with
maxima at 320, 442 K and 682 K and TG mass loss 8.0%, 38.8%
and 11.1% respectively. In the case of PdCl2(VTMS) (1) in the
first step two methyl group from VTMS ligand were detached.
The results of the thermal analysis have been verified by TG–IR
analysis of gaseous products of the complexes decomposition
(over 290–470 K), where bands from methyl C H stretching
(2800–2900 cm−1) were observed. In the second step the rest of
VTMS molecules evolves. Summary mass loss for three effects
2.3.2. Synthesis of palladium(II) complexes
Described procedure is a general way of complexes synthe-
sis with studied ligands: Freshly prepared PdCl2(C6H5CN)2 (0.05 g,
1.3 × 10−4 mol) was dissolved in 20 ml of benzene in the Schlenk
tube and trimethyl(vinyl)silane (VTMS) (275 ␮l, 1.9 × 10−4 mol) was
added via septum and the reaction mixture was stirred for 12 h
at room temperature. Afterwards mixture was filtered and sol-
vent removed under vacuum at 273 K, living brown oily product
of PdCl2(VTMS)2, which was unstable on the air. All obtained prod-
ucts had an oily consistence. They have been purified by dissolving
in hexane. Unreacted olefins and solvent were removed on vac-
uum line. The composition was conformed by the CHN elemental
analysis results and IR spectra analysis. In the IR spectra bands
from solvent and free ligand stretching vibrations have not been
observed. The reaction between olefin or initial complex with
obtained product has not been noticed in the IR and NMR spec-
tra. The results of these analysis confirmed purity of the product
without solvent and ligand.

E. Szłyk, M. Barwiołek / Thermochimica Acta 495 (2009) 85–89
87
Table 1
Palladium(II) complexes thermoanalytical data.
Compound
Heat effect
a*
Temperature range (K)
DTGmax (K)
a*
Mass loss (%)
found
Evolved moiety
2VTMS
b*
a*
b*
b*
calcd
53.3
PdCl2(VTMS)2 (1)
endo
endo
endo
endo
endo
endo
endo
298–343
398–463
650–720
300–340
430–500
680–740
790–910
320
442
682
329
465
695
842
53.7
PdCl2(PTMSA)2 (2)
endo
exo
endo
endo
endo
endo
endo
exo
330–375
450–543
590–632
634–723
360–410
490–595
650–760
810–830
352
472
629
687
385
525
732
863
66.7
13.2
66.4
13.5
2C6H5C CSi(CH3)3
Cl2
PdCl2(DMB)2 (3)
endo
endo
endo
endo
endo
endo
345–423
430–523
608–748
410–460
460–520
680–770
417
438
693
426
476
730
49.5
9.7
48.6
10.1
2(CH3)2C C(CH3)2
Cl2
PdCl2(DADMS)2 (4)
endo
endo
exo
endo
endo
endo
endo
endo
298–318
323–388
408–471
650–700
710–750
290–320
400–480
590–740
310
350
427
673
721
303
445
668
59.7
14.7
59.7
15.5
2DADMS
Cl2
(a*) heating range 773 K, heating rate 2.5 ◦/min, (b*) heating range 1273 K, heating rate 5 ◦/min
very close to calculated for two VTMS molecules (cal. 53.3%, found
53.7%). Palladium was formed above 641 K what is evident from
DTG curve. The process of chlorine detachment was conformed by
MS spectrum, where the chlorine isotope pattern signal (m/z 71, R.I.
78%) was observed at T = 474 K.
The differences of TG curves for compound (1) (Figs. 1 and 2)
result from various conditions during thermal decomposition pro-
cesses. In both cases the decomposition processes were studied in
a dynamic atmosphere of dry nitrogen flowing at 60 ml/min, but
in the first case the heating rate was 2.5 ◦/min, and heating range
up to 773 K, whereas in the second the heating rate was 5 ◦/min,
heating range up to 1273 K. The different measurement conditions
caused various shape of the TG and DTA curves. [26] Similar phe-
nomenon has been observed on the thermograms of all studied
(1–4) complexes.
Thermogram of (2) (Fig. 3) exhibits four DTG peaks with maxima
at 352, 472, 631 and 687 K, which on TG curve reveal there stages
with 14.1, 26.6, and 13.2% sample mass loss. The total mass loss
(66.7%) corresponds with the detachment of PTMSA (cal. 66.4%).
Further TG analysis indicates reduction of the sample mass (13.2%),
what originate from Cl2 molecule dissociation (cal.13.5%).
The palladium metal was formed above 720 K. Analysis of the
DTA curve is more informative from the thermogram measured at
higher heating rate (5 ◦/min), than for 2.5 ◦/min, where the curve
does not present distinct exo- or endotherms. On both curves at the
beginning (up to 441 K) only change of sample heat capacity can be
Fig. 1. TGA-DTA traces of PdCl2(VTMS)2 (1), heating range 773 K.
(57.9%) correspond to the detachment of two VTMS molecules and
partial dissociation of chlorine (difference between 57.9 and 53.3%).
Detachment of chlorine is evident on the thermogram registered
up to 1273 K (Fig. 2), where two peaks on DTG (max. 695 K and
842 K) correspond to 25.2% mass loss on TG curve, leaving metallic
palladium (lack of mass loss on TG above 700 K).
This thermogram is even more informative about detachment
of VTMS, because summary mass loss for the two first stages is
Fig. 2. TGA-DTA curves of PdCl2(VTMS)2 (1), heating range to 1273 K.
Fig. 3. TGA-DTA curves of PdCl2(PTMSA)2 (2).

88
E. Szłyk, M. Barwiołek / Thermochimica Acta 495 (2009) 85–89
allyl)(hfacac) and Pd(␩3-methyl-2-allyl)(hfacac). The high purity
palladium films (>99% Pd) from those complexes by using different
reactive gases, have been obtained. [10,11–28]. The decomposi-
tion temperatures were relatively high: 603–643 K and vacuum
10−2 Torr. [28] Studied compounds (1–4) decomposed to metallic
palladium over 478–720 K, what in comparison to the above refer-
enced palladium complexes [10,11,28] make them promising CVD
precursors. Important parameters for CVD of metallic palladium
such as low initial temperature of the thermal decomposition pro-
cess (298 K for 1 and 4) and ambient pressure of the measurement
are also in favor of the studied complexes.
3.2. TG-IR spectra
Analysis of the IR spectra of the gases evolved during the
thermal decomposition of PdCl2(VTMS)2 (1) suggests the presence
Fig. 4. TGA-DTA curves of PdCl2(DADMS)2 (4).
of trimethyl(vinyl)silane (ꢀ( CH) − 2966 cm−1
,
ꢀ(C C) − 1511,
1540 cm−1, ꢀ(Si C) − 847 cm−1) in the gas phase over 290–470 K.
Below 290 K and above 470 K these bands were not observed, what
indicates the absence of VTMS in the gas phase. The latter is in
agreement with the mass loss observed on TG curve (52.66%) and
endotherm on DTA curve. IR spectra of the uncoordinated VTMS
revealed bands at 2956 ꢀ( CH), 1405 ꢀ(C C), 836, 851, 859 ꢀ(Si C)
cm−1. Observed coordination shift of the ꢀ( CH) − 2966 cm−1 band
towards higher frequency, in the gas phase, in comparison to the
spectrum of free VTMS, suggests shorter double bonds distances
in the gas phase. TG/IR spectra of the PdCl2(PTMSA)2 (2) below
noted. First exotherm revealed maximum at 472 K, whereas the sec-
ond weak endotherm maximum at 629 K (1273 K range) was found.
Such behavior is different from the compound (1), what can be
explained by the ligand structure and coordination way of PTMSA.
Compound (3) reveals different DTG curve in comparison to (1),
because two peaks in the range 345–450 K are poorly separated and
onlytotalmasslosscanbecalculated(49.5%), whichcanbeassigned
to 2 DMB molecules detachment (cal. 48.6%). Second DTG peak cor-
responds to 9.7% mass loss, what can be related to half chlorine
molecule (cal. 10.1%) dissociation, followed by metallic palladium
formation at 685 K.
Thermogram of (4) (Fig. 4) over 873 K presents on TG curve con-
tinuous mass loss, starting from 304 K to 471 K, whereas the first
exothermic stage can be observed on DTA curve (305 K).
The mass loss corresponds to 59.5% (cal. 59.7%), which is in
good accordance with the DADMS dissociation. Further sample
mass reduction is connected with the chlorine molecule detach-
ment (found 14.7%; cal. 15.5%) and palladium formation at 690 K.
For all complexes detachment of chlorine was conformed by MS
results, where peaks characteristic for chlorine isotope pattern with
high relative intensity [(Cl2 m/z (71)] were detected in the range
389–548 K.
Metallic palladium was the final product of the thermal
decomposition for complexes (1–4), what is evident from TG cal-
culations from thermograms measured to 1273 K (cal./found Pd%:
(1) 28.4/29.8, (2) 32.9/32.4, (3) 20.1/20.1, (4) 23.5/23.9). Besides
that XRD studies of the residues in the crucible were performed
and observed diffractogram lines (0.2230, 0.1940, 0.1370, 0.1170,
0.1097 nm) correspond to metallic palladium (Powder Diffraction
File) [27].
Firststageonsettemperaturessuggestlowerstabilityofcomplex
(1) and (4), whereas all of them decompose to palladium at temper-
atures over 478–720 K, what can be promising parameter for CVD
of palladium. However both compounds (1 and 4) can be tested
as CVD precursors for metallic palladium because of the initial
decomposition temperatures below 300 K. Noted temperatures of
palladium formation reveals the following order PdCl2((DAMDS)2
(4) < PdCl2(VTMS)2 (1) < (3) PdCl2((DMB)2 < PdCl2((PTMSA)2 (2).
When data for (1) are related to complexes: (2), (3) and (4)
(Figs. 3 and 4) it is evident that compound (1) and (4) have similar
onset of the first effect ca. 298 K.
730 K exhibit characteristics bands: ꢀ(CHaromatic) − 3071 cm−1
,
ꢀ(C C) − 2300 cm−1
,
ꢀ(Si C) − 851 cm−1
,
which are sifted
towards higher frequencies in comparison to IR spectrum of
free PTMSA (ꢀ(C C) − 2185 cm−1
,
ꢀ(Si C) − 820 cm−1
) except
ꢀ(CHaromatic) − 3080 cm−1
.
These bands indicate 1-phenyl-
2(trimethylsilyl)acetylene presence in the gaseous phase during
thermal decomposition. Above 730 K in the TG/IR spectra in the
region 600–1100 cm−1 and 1800–2600 cm−1 absorption bands
from C CSi(CH3)3 fragments were not observed, what can be
related to the completion of ligand detachment process.
For PdCl2(DMB)2 (3) in the temperature above 380 K alkene
absorption bands ꢀ(CH3) − 3080 cm−1 and ꢀ(C C) − 1648 cm−1
were registered. [21–25] These fragments were noted also in MS,
(T = 548 K, [C4H9]+ (57) R.I. 100%) and can be assigned to ligands
fragmentation. The IR spectra of the free DMB revealed bands at
(ꢀ(CH3) = 2970, 3000 cm−1, ꢀ(C C) = 1675 cm−1, which upon coor-
dination were shifted towards higher frequencies.
In the TG/IR spectra of (4) the characteristic bands for
diallyldimethylsilane
above
300 K
(ꢀ( CH) − 2966 cm−1
,
ꢀ(C C) − 1650 cm−1
,
ꢀ(Si C) − 815 cm−1
) have been detected,
whereas in free DADMS bands at (ꢀ( CH) − 2900, 3000, 3180 cm−1
,
ꢀ(C C) − 1620 cm−1, ꢀ(Si C) − 895 cm−1)werenoted. Thepresence
of these bands indicate the beginning of the DADMS detachment
above 300 K.
Comparing the results of the TG/IR spectra analysis of all palla-
dium(II) complexes it can be noted, that the ligand molecules were
detachedinthefirststageofthethermalprocessfollowedbyrelease
of the chlorine molecule in the second stage.
3.3. Mass spectra analysis
Variable temperature EI-MS spectra were recorded in the range
303–573 K in order to detect the metallated species in the gas phase,
which is the major feature determining usage of complexes as CVD
precursors. These fragments should be stable during transport in
the gas phase in CVD equipment and adsorb on the substrate sur-
face. In MS spectrum of (1) (at 474 K) the following most intensive
ions: [CSi(CH3)]+ R.I. 100%, Cl2 R.I. 78%, [Pd[(CH3)3SiCH CH]]+ R.I.
44%, [PdCl[[(CH3)3Si]+ R.I. 40% were detected. Below this tempera-
Reported Pd(␩3-allyl)2 and Pd(␩3-methyl-2-allyl)2, Pd(␩3-
allyl)(Cp) complexes were studied as precursors of thin films of
palladium by CVD method. [8] It has been observed that Pd(␩3-
allyl)2 and Pd(␩3-methyl-2-allyl)2 complexes revealed slight
palladium layers contamination by C(<1%) (deposition process at
523 K under medium vacuum 10–4 Torr). [10,11,28] Better volatility
revealed Pd(␩ 3-allyl)(acac), Pd(␩ 3-methyl-2-allyl)(acac), Pd(␩3-

E. Szłyk, M. Barwiołek / Thermochimica Acta 495 (2009) 85–89
89
ture low intensive peaks containing only organic fragments (VTMS
4. Conclusions
R.I. 16% and [CSi(CH3)]+ R.I 100%) were observed. The presence
of organic and chlorine species indicate detachment of VTMS and
chlorine molecules and complex decomposition in the temperature
range 358–474 K. MS spectra of (2) in the range 321–521 K exhibit
the following peaks from olefinic and organometallic species:
Thermal analysis of the complexes (1–4) indicated the metallic
palladium as the final product of the thermal decomposi-
tion, what was evident from TG calculations on thermograms
measured to 1273 K and XRD studies of the residues in the
crucible (Powder Diffraction File) [27]. First stage onset temper-
atures suggest lower stability of complex (1) and (4), whereas
all of them decompose to palladium at temperatures over
478–720 K, what can be promising parameter for CVD of palla-
dium. Analysis of TG/IR spectra of all palladium(II) complexes
indicate the ligand molecules detachment. The VT-MS spectra
revealed fragments containing palladium species in the range
321–548 K. Noted temperatures of palladium formation reveals
the following order PdCl2(DAMDS)2 (4) < PdCl2(VTMS)2 (1) < (3)
PdCl2(DMB)2 < PdCl2(PTMSA)2 (2).
[Si(CH)3]+ (R.I. 44% at 321 K and 50% at 490 K), [PdSi(CH3)3]2 (R.I.
+
7% at 321 K and 4% at 490 K), [PdSiC]+ (R.I. 98% at 321 K and 8% at
490 K). However the spectrum at 321 K present [C6H5CCH2]+ R.I.
100% as the most intensive signal. Such fragments indicate simul-
taneous detachment and fragmentation of PTMSA over 321–490 K.
It can be noted, that the intensity of metal bonded peaks exhibit
reduced relative intensity along the temperature increase. The lat-
ter suggests decomposition of the organometallic fragments and
metallic palladium formation, similarly to processes observed on
TG and DTG curves. In the case of (3) at 548 K peaks which include
metallated species revealed the following data: [PdC4H6Cl]+ R.I.
34%, [PdCl[(CH3)2C C(CH3)H]]+ R.I. 79%, [Pd3[(CH3)2C C(CH3)2]2]
R.I. 10%. Besides that the intensive peaks from organic species were
noted as well: [C4H9]+ R.I. 100% and Cl2 R.I. 62%. Below 548 K frag-
ments with palladium species were not registered, only line from
[CH3CH2CCl]+ (R.I. 28%) ion was detected.
Acknowledgement
Authors wish to thank Polish State Committee for Scientific
Research for a Grant: PBZ-KBN-118/T09/11/2004.
MS spectra of (4) reveal peaks from organic fragments
[CH2 CH CH2]+ (R.I. 38% at 447 K and R.I. 40% at 389 K), [Si(CH)3]+
(R.I. 35% at 447 K and R.I. 52% at 389 K), [CH2CHCHCH2Si(CH3)3]+
(R.I. 40% at 447 K and R.I. 56% at 389 K), while organometallic
fragments: [PdCH2CHCH2]+ (R.I. 72% at 389 K and 98% at 447 K,
[Pd(CH2CHCH2)SiH(CH3)2]+ (R.I. 63% at 389 K and 84% at 447 K)
were noted over 389–447 K. Moreover at 389 K dipalladium ion
([Pd2CH2CHCH2Si]+) has been observed. Similar dipalladium
species were noted in MS of di-␮-chlorodiallylodipalladium(II)
[C6H5PdCl]2. [15] Above results demonstrate, that compounds
(1–4) can be used for the deposition of palladium layers by
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tca.2009.06.002
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