Thermal studies of Ag(I) complexes with triethylphosphine and perfluorinated carboxylates

Article abstract of DOI:10.1016/S0040-6031(98)00285-8

Silver(I) complexes with triethylphosphine and perfluorinated carboxylic acids residues of general formula [Et₃PAgOOCR]₂, where R=C₂F₅, C₃F₇, C₆F₁₃, C₇F

Full text of DOI:10.1016/S0040-6031(98)00285-8

Thermochimica Acta 315 (1998) 121±128
Thermal studies of Ag(I) complexes with triethylphosphine
and per¯uorinated carboxylates
*
I. èakomska , E. Szøyk, A. Grodzicki
Nicolaus Copernicus University, Department of Chemistry, 87 100 Toru nÄ , Poland
Received 30 October 1997; received in revised form 2 February 1998; accepted 3 February 1998
Abstract
Silver(I) complexes with triethylphosphine and per¯uorinated carboxylic acids residues of general formula
Et PAgOOCR] , where RˆC F , C F , C F , C F , C F , C F , C F and Et PAgOOC(CF ) COOAgPEt , were
[
3
2
2
5
3
7
6
13
7
15
8
17
9
19
6
5
3
2 3
3
synthesized. Thermal decomposition proceeded in two stages ± both exothermic processes corresponding to the elimination of
carboxylate and triethylphosphine residues. The ®nal product of the thermal decomposition was metallic silver. Analyses by
13
19 31
C, F, P NMR spectroscopy and vibrational spectra suggest trigonal coordination of Ag(I), the coordination sphere
consisting of unidentate triethylphosphine and bidentate carboxylates forming bridges between metal ions. # 1998 Elsevier
Science B.V.
Keywords: Ag(I) complexes; IR and NMR; per¯uorinated carboxylic acids; thermal analysis; triethylphosphine
1
. Introduction
of the bridging carboxylates [15±19], but in
Ph P) Ag(OOCH) the formate appeared to be uni-
(
3
2
Coordination compounds of the copper triad metals
dentate bonded [20] and a rare chelating carboxylate
was also found [21]. It was also interesting to study the
in¯uence of the chain length and the electronegativity
of the ¯uorine atoms on the thermal stability of the
Ag±O bond. As found earlier [22], the volatility of
have been extensively studied because of their possi-
ble applications as precursors in the Chemical Vapour
Deposition (CVD) of metal (Au, Ag) or oxide layers
(
Cu). The volatility of Ag(I) and Au(I) complexes with
oxygen bonded ligands (ꢀ-diketonates) [1±8]
prompted us to study analogous silver(I) complexes
with the same donor atoms and triethylphosphine
Ag(I) complexes with Ph P and per¯uorinated car-
3
boxylates is insuf®cient for CVD purposes, therefore,
triethylphosphine (Et P) was chosen. The main goals
3
(
Et P). Carboxylates have been chosen as oxygen
3
of our studies were the analysis of the thermal decom-
position processes, elucidation of decomposition reac-
tions mechanism and spectral characteristics of
[Et PAgOOCR] complexes, where RˆC F , C F ,
donor ligands which are able to bind a uni- or biden-
tate (chelating or bridging) mode, hence one may
expect multinuclear complexes [9±14]. Crystal
structures of Ag(I) complexes con®rmed the presence
3
2
2
5
5
3 7
C F ,
C F ,
C F ,
C F ,
C F
6
and
6
13
7
15
8
17
9
19
Et PAgOOC(CF ) COOAgEt . The temperatures of
3
2 3
3
the ®nal product formation will be discussed in
relation to a composition of complexes.
*
Corresponding author.: Fax: 00 48 56 6542477.
0040-6031/98/$19.00 # 1998 Elsevier Science B.V. All rights reserved
P I I S 0 0 4 0 - 6 0 3 1 ( 9 8 ) 0 0 2 8 5 - 8

1
22
I. èakomska et al. / Thermochimica Acta 315 (1998) 121±128
2
. Experimental
where mass of sample was 80 mg); the reference
material was Al O .
2
3
Per¯uorinated carboxylic acids (98±99%) and Et3P
99%, 1M solution in tetrahydrofuran) were purchased
The IR spectra were obtained using a Perkin±Elmer
2000 FTIR spectrometer in KBr discs, over the 400±
(
from Aldrich and AgNO analytical grade from POCh
�
1
� 1
4000 cm range. Below 400 cm polyethylene discs
were used. Spectra obtained in KBr were compared
with the same obtained in nujol mull with the same
data acquisition parameters and they appeared to be
3
Gliwice (Poland). All reactions were carried out under
argon. Solvents were puri®ed and dried by standard
methods. Complexes were synthesized by reacting
�
1
[
C F , C F , C F , C F and AgOOC(CF ) COOAg
RCOOAg]2 [23], where RˆC F , C F , C F ,
identical in the 1000±1700 cm range. NMR spectra
were recorded on a Varian Gem 200 MHz spectro-
2
5
3
7
6 13
7
15
8
17
9
19
6
5
2 3
13
with Et P. Et P (0.004 mol) in tetrahydrofuran was
3
meter. Samples were dissolved in CDCl . C spectra
3
3
19
31
were recorded at 50 MHz, F at 188 MHz and P at
mixed with ethanol solution, or suspension in the case
of the chain above C F , of [RCOOAg] (0.002 mol).
13
81 MHz. Reference were tetramethylsilane for C,
31
6
13
2
1
9
31
The reaction was stirred in the dark until a clear
solution was formed, which after evaporation on
vacuum line gave a colourless oil. Silver was deter-
mined argentometrically, after previous complex
mineralization. C and H were determined by elemen-
tal semi-microanalysis. The results of elemental ana-
lyses were as follows (% calc/found):
CCl F for F and 85% H PO for P. P NMR
3 3 4
spectra in CDCl3 were run at temperature 300 K
�
3
and concentration 1Â10 M.
Powder X-ray diffraction data were obtained on
a Dron 1 (USSR) diffractometer using CuKꢁ,
ꢂˆ0.1524 nm.
C18H30F10O4P2Ag2; Agꢀ27:7=27:6†;
3
. Results and discussion
Cꢀ27:8=27:7†; Hꢀ3:9=3:5†;
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
3
.1. Thermal analysis
C20H30F34O4P2Ag2; Agꢀ24:6=24:4†;
Cꢀ27:4=27:4†Hꢀ3:5=3:4†;
C26H30F26O4P2Ag2; Agꢀ18:3=18:0†;
Cꢀ26:5=26:2†; Hꢀ2:6=2:4†;
The results of the thermal analysis performed in
nitrogen are listed in Table 1. Decomposition pro-
cesses started in the 383±423 K range as an exotherm
followed by another one (Fig. 1). The exotherms are
connected with the mass loss on TG curve which
corresponds to exclusion of carboxylate and triethyl-
phosphine residues in two overlapping stages. How-
ever, from DTG curve analysis it is evident that both
dissociate in two subsequent processes. Because the
onset of the second reaction coincide with the ®nal
temperature of the ®rst one, we were unable to ®nd the
initial temperature of the second stage of decomposi-
tion reaction. The similar phenomenon was observed
for Ag(I) salts with non¯uorinated carboxylates [24±
C H F O P Ag ; Agꢀ16:9=16:6†;
28
30 30
4
2
2
Cꢀ26:3=26:0†; Hꢀ2:4=2:0†;
C30H30F34O4P2Ag2; Agꢀ25:7=25:4†;
Cꢀ26:1=26:0†; Hꢀ2:2=2:0†;
C H F O P Ag ; Ag14:6=14:4†;
32
30 38
4
2
2
Cꢀ26:0=25:9†; Hꢀ2:1=1:9†;
C26H30F10O4P2Ag2; Agꢀ24:7=24:4†;
Cꢀ35:7=35:2†; Hꢀ3:5=3:0†;
2
6] and Ag(I) complexes with the identical carbo-
C H F O P Ag ; Agꢀ31:3=31:0†;
xylates and triphenylphosphine [22] or trimethyl-
phosphine [27]. The onset temperatures of the ®rst
exotherm can be taken as a measure of the Ag±O
17
30
6
4
2
2
Cꢀ29:6=29:2†; Hꢀ4:4=4:0†:
0
Thermal analysis was carried out on a MOM
OD-102 Derivatograph, Paulik and Paulik (Hungary).
The atmosphere over the sample was nitrogen, heating
strength in [R PMOOCR ] type complexes [22].
3
2
The lowest onset temperature, observed for
[Et PAgOOCC F ] is 15 K higher than for the ana-
logous complex with Ph P [22]. The low stability
3
6 9 2
�
1
,
range was up to 773 K, the heating rate 2.5 K/min
mass of sample 50 mg (except [Et PAgOOCC F ] ,
3
3
8 17 2
of Ag±O bond can be explained by the stronger ꢃ

I. èakomska et al. / Thermochimica Acta 315 (1998) 121±128
123
Table 1
Results of thermal analysis
Complex
Heat effect
Temperature (K)
Weight loss (in %)
Detached
groups
a
b
c
T
i
T
m
T
f
calc.
found
1
2
3
4
5
6
7
8
[Et
[Et
[Et
[Et
[Et
[Et
[Et
3
3
3
3
3
3
3
PAgOOCC
PAgOOCC
PAgOOCC
PAgOOCC
PAgOOCC
PAgOOCC
PAgOOCC
2
3
6
7
8
9
6
F
F
F
F
F
F
F
5
]
]
2
2
Exo
Exo
Exo
Exo
Exo
Exo
Exo
Exo
423
403
413
418
413
388
383
403
478
458
453
473
453
458
463
458
528
501
493
553
523
513
506
683
72.3
75.4
79.6
83.1
80.9
85.4
75.3
68.8
71.9
75.0
79.4
83.0
81.2
85.2
74.8
69.0
C
C
C
C
C
C
C
C
3
4
6
8
8
F
F
F
F
F
5
O
O
2
‡Et
3
3
P
P
7
6
2
‡Et
13
15
17
19
]
2
]
2
]
2
]
2
13
15
17
O
2
2
2
‡Et
3
3
3
P
O
O
‡Et
‡Et
P
P
10 19
F
O
2
‡Et
3
P
5
]
2
7
F
4
O
O
2
4
‡Et
3
Et
3
PAgOOC(CF
2
)
3
COOAgPEt
3
5
F
6
‡2Et
3
P
a
b
c
Initial temperature.
Maximum temperature.
Final temperature.
electron acceptor character of the penta¯uorophenyl
ring compared with the per¯uorinated aliphatic chain.
The Ag±O bond became less covalent than in other
complexes and the thermal stability of Ag±O bond
decreased. The highest onset temperature (423 K) of
the decarboxylation process has been found for
dimeric. The total mass loss corresponds to the
dissociation of carboxylate and 2 mol of triethyl-
phosphine.
The second step of decomposition reaction corre-
sponds to the detachment of Et P. The dissociation of
3
Et P proceeds immediately after decarboxylation that
3
[
Et PAgOOCC F ] . Most probably, this is an effect
3
enables the determination of onset temperatures
(Fig. 1). The ®nal product of the decomposition pro-
cesses is metallic silver, which is evident from the
analysis of TG curves and the ®nal product powder
diffractograms examination. Observed lines for metal-
lic silver (0.2352, 0.2026, 0.1179, 0.1444, 0.1233 nm)
correspond to those reported in Powder Diffraction
File [28]. The lowest temperature of silver formation
(493 K) was found for [Et PAgOOCC F ] , that
2 5 2
of ꢄ electron donor properties of triethylphosphine,
and short per¯uorinated chain that causes the lower
polarization of Ag±O bond and enhances its stability.
The complexes with the short aliphatic chain (C , C )
revealed lower onset temperatures of the ®rst step than
the analogous Ag(I) complexes with Ph P [22]. The
2
3
3
weaker stabilization of Ag±O bond in the presence of
Et P, than Ph P, can be related to the ꢄ electron donor
3
3
3
6 13 2
properties of triethylphoshine. The decrease of M±O
bond stability was also found for copper triad com-
plexes with the analogous ligands [22,27]. The results
of thermal analysis conclude that stabilisation of
Ag±O bond is in¯uenced by the electron donor accep-
tor properties of tertiary phosphines. The steric factor
has less profound impact because strong ꢃ electron
acceptor ligand (triphenylphosphine), despite steric
hindrances, stabilises Ag±O bond more effectively
than less bulky and weak ꢃ electron acceptor, such
as triethylphosphine. Thermal decomposition of
Eq. (8) proceeds in a similar way as the majority
of the discussed complexes. Decomposition of
initial temperature (403 K) is identical to the
hepta¯uorobutyrate complex. This feature can be
related to the same amount of carbon atoms in the
aliphatic chain and the fact that both complexes are
makes this complex promising precursor for CVD
purposes. The surprisingly high temperature of
silver formation (553 K) was found for
[Et PAgOOCC F ] , but still it is in the range accep-
table for CVD purposes (max. 620 K). The highest
temperature of metal formation (683 K) was detected
for Eq. (8) which is out of the range acceptable for
CVD precursors. The temperatures of the ®nal product
formation for remaining complexes, Eqs. (1)±(7), are
lower (in 493±523 K range). Temperatures of silver
formation in the studied complexes are ca. 150 K
lower than for the respective Ag(I) complexes with
3
7 15 2
identical per¯uorinated acids and Ph P [22]. The
3
presented series of complexes decomposed in a way
characteristic for silver(I) carboxylates and copper
triad complexes with tertiary phosphines. Silver(I)
salts with aliphatic and aromatic carboxylates also

1
24
I. èakomska et al. / Thermochimica Acta 315 (1998) 121±128
3 8 17 2 3 2 3
Fig. 1. Thermal decomposition of Ag(I) complexes: (A) [Et PAgOOCC F ] (mass of sample was 80 mg); (B) Et PAgOOC(CF ) COOAg-
PEt ; (a) TG-, (b) DTG-, (c) DTA- (d) T-curves.
3
decomposed to metallic silver in a two-step process
endo- followed by exotherm) and decarboxylation
was not exactly separated from dealkylation. Per-
uorinated carboxylates, in relation to non¯uorinated
one, do not change the decomposition mechanisms but
diminish the stability of Ag±O. The lowest stabilisa-
tion of the Ag±O bond was found for the per¯uori-
nated aromatic carboxylates whereas the highest for
(
¯

I. èakomska et al. / Thermochimica Acta 315 (1998) 121±128
125
the one with the short per¯uorinated chain. This effect
3.2. NMR spectral studies
suggests that in Ag(I) complexes with carboxylates the
electron accepting substituents would stabilise the
coordination sphere. The Ag±O bond stability also
depends on the electronic properties of tertiary phos-
phines rather than steric factors and changes in the
following sequence: Me P<Et P<Ph P. Silver forma-
1
3
19 31
Chemical shifts for the C, F, P resonances of
31
complexes are listed in Table 2. Single P resonance
band appeared in the 9.5±13.4 ppm range, i.e. 27.6±
13
31.6 ppm up®eld in relation to free Et P [29]. The
3
C
resonances of COO group revealed the most indicative
changes imposed by coordination to Ag(I). The sig-
nals are shifted down®eld 0.6±2.7 ppm in comparison
to RCOOH (except Eqs. (1) and (8)) but it is dif®cult
3
3
3
tion temperatures found for the studied complexes
below 620 K) are suf®cient for application to the
compounds in CVD as silver precursors.
(
Table 2
19 31
C, F, P NMR spectra analysis (in ppm)
13
13
C
19
F
31
P
Complex
a
b
c
ꢅCOO
Á
1
C(2)F
2
Á
2
ꢅ
Á
3
1
2
3
4
5
6
7
8
[Et
[Et
[Et
[Et
[Et
[Et
[Et
3
3
3
3
3
3
3
PAgOOCC
PAgOOCC
PAgOOCC
PAgOOCC
PAgOOCC
PAgOOCC
PAgOOCC
2
3
6
7
8
9
6
F
F
F
F
F
F
F
5
]
]
2
162.5
163.1
161.3
163.0
162.9
161.3
163.4
163.8
� 0.8
0.9
� 41.5
� 49.3
� 38.7
� 38.2
� 38.6
� 39.3
3.4
0.3
3.0
3.3
3.0
2.2
Ð
13.1
13.0
13.4
13.0
13.3
13.5
12.4
9.5
31.2
31.1
31.5
31.1
31.4
31.6
30.5
27.6
7
2
13
15
17
19
]
]
]
]
2
2
2
2
0.6
2.5
2.7
1.2
d
d
5
]
2
� 0.9
Ð
Ð
Et
3
PAgOOC(CF
2
)
3
COOAgPEt
3
� 38.0
Ð
a
b
c
d
ꢅCOO(complex)� ꢅCOO(acid)
ꢅC(2)F (complex)� ꢅC(2)F (acid)
ꢅ(complex)� ꢅ(Et P); ꢅ(Et P)ˆ� 18.1 ppm
ꢅCF (complex): m: � 84.5 (ꢅmˆ� 2.0); o: � 63.1 (ꢅoˆ� 4.3); p: � 77.4 (ꢅpˆ� 8.7)
ꢅmˆꢅm CF(complex)� ꢅm CF(acid); ꢅoˆꢅo CF(complex)� ꢅo CF(acid); ꢅpˆꢅp CF(complex)� ꢅp CF(acid); mˆmeta, oˆortho, pˆpara
2
2
3
3
13
3 2 5 2
Fig. 2. C NMR spectrum of [Et PAgOOCC F ] .

1
26
I. èakomska et al. / Thermochimica Acta 315 (1998) 121±128
to relate these values with the way of COO coordina-
tion (Fig. 2). Down®eld shift can be explained by the
lower negative charge on carbon in COO group caused
it is dif®cult to correlate the direction and the magni-
19
1
3
tude of C, and F chemical shifts with the way of
coordination.
19
by the presence of electronegative ¯uorine atoms.
F
NMR (Fig. 3) has been also affected by the Ag±O
bond formation but the changes were observed only
for the signals of C(2)F group (Table 2), which upon
3.3. IR spectral analysis
Carboxylates can coordinate to metal ions in a
number of ways, such as uni- or bidentate (chelating
or bridging) [30±32], that can be concluded from the
IR spectra analyses. For this purpose, correlations
2
coordination are shifted down®eld (0.3±3.4 ppm) in
relation to free acids. The NMR results gave evidences
of Et P and carboxylates binding to the central ion, but
3
1
9
Fig. 3. F NMR spectrum of [Et
3
7 15 2
PAgOOCC F ] .
Table 3
�
1
Characteristic absorption bands in IR spectra (in cm
)
a
b
Complex
ꢆ
asCOO
ꢆ
s
COO
Á
1
Á
2
ꢆAg±P
ꢆAg±O
1
2
3
[Et
3
[Et
3
[Et
3
PAgOOCC
PAgOOCC
PAgOOCC
2
3
6
F
F
F
5
]
]
2
2
1667
1683
1688
1416
1399
1397
252
284
291
268
272
272
225
224
225
326
322
333
7
13
]
2
198
4
5
6
7
8
[Et
[Et
[Et
[Et
3
3
3
3
PAgOOCC
PAgOOCC
PAgOOCC
PAgOOCC
7
8
9
6
F
F
F
F
15
17
19
]
]
]
2
2
2
1681
1681
1662
1656
1669
1406
1407
1406
1396
1412
275
254
256
260
257
272
272
276
201
Ð-
218
216
222
217
220
317
327
330
316
326
5 2
]
3 2 3 3
Et PAgOOC(CF ) COOAgPEt
a
ꢆ
ꢆ
asCOO� ꢆ
asCOO� ꢆ
s
COO (in complex).
COO (in sodium salt).
b
s

I. èakomska et al. / Thermochimica Acta 315 (1998) 121±128
127
�
1
Fig. 4. IR spectrum of [Et PAgOOCC F ] in the range 475±175 cm .
3 6 13 2
between the mode of carboxylate linkage and COO
group stretching frequencies have been applied. The
calculated (as ± asymmetric, s ± symmetric) parameter
for the complexes is in favour of bridging carboxylates
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[
[
[
[
[
[
[
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3
2 5 2
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1
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�
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�
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�
1
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(

1
28
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