Volatile fluorinated trimethylplatinum(IV) β-diketonates with pyridine: Synthesis, properties, and structure

Article abstract of DOI:10.1134/S1070328411080136

Volatile fluorinated trimethylplatinum(IV) β-diketonates with pyridine (CH₃)₃Pt(CH₃-CO-CH-CO-CF₃)Py (I) and (CH₃)₃Pt(CF₃-CO-CH-CO-CF₃)Py (II) obtained from trifluoroacetylacetone and hexafluoroacetylacetone were studied. The synthesis, elemental analysis data, and IR spectra were described. X-Ray diffraction analysis was performed and the crystal structure was determined; the geometric characteristics of complexes I and II were obtained. Both structures are monomeric molecular structures. The molecules in the crystal are connected only by weak van der Waals forces. The coordination polyhedron of platinum in I and II is a slightly distorted octahedron. The shortest Pt...Pt distances are 6.639 A (for I) and 6.254 A (for II). The average P-O, Pt-N, and P-C distances are 2.157, 2.182, and 2.030 A, respectively. The deviations of the bond angles at Pt atoms from ideal values of 90° do not exceed 4.8°.

Full text of DOI:10.1134/S1070328411080136

ISSN 1070ꢀ3284, Russian Journal of Coordination Chemistry, 2011, Vol. 37, No. 9, pp. 680–687. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © G.I. Zharkova, I.A. Baidina, I.K. Igumenov, 2011, published in Koordinatsionnaya Khimiya, 2011, Vol. 37, No. 9, pp. 681–688.
Volatile Fluorinated Trimethylplatinum(IV) βꢀDiketonates
with Pyridine: Synthesis, Properties, and Structure
G. I. Zharkova*, I. A. Baidina, and I. K. Igumenov
Nikolaev Institute of Inorganic Chemistry, Siberian Division, Russian Academy of Sciences,
pr. akademika Lavrent’eva 3, Novosibirsk, 630090 Russia
*
Eꢀmail: zharkova@mic.nsc.ru
Received December 22, 2010
Abstract—Volatile fluorinated trimethylplatinum(IV)
β
ꢀdiketonates with pyridine (CH ) Pt(CH –COꢀ
3 3 3
CH–COꢀCF )Py ( ) and (CH ) Pt(CF –CO–CH–CO–CF )Py (II) obtained from trifluoroacetylacetone
I
3
3 3
3
3
and hexafluoroacetylacetone were studied. The synthesis, elemental analysis data, and IR spectra were
described. XꢀRay diffraction analysis was performed and the crystal structure was determined; the geometric
characteristics of complexes and II were obtained. Both structures are monomeric molecular structures.
The molecules in the crystal are connected only by weak van der Waals forces. The coordination polyhedron
..
I
.
of platinum in I and II is a slightly distorted octahedron. The shortest Pt Pt distances are 6.639 Å (for I) and
6
.254 Å (for II). The average P–O, Pt–N, and P–C distances are 2.157, 2.182, and 2.030 Å, respectively. The
deviations of the bond angles at Pt atoms from ideal values of 90° do not exceed 4.8°.
DOI: 10.1134/S1070328411080136
The modern trends in the development of high size [9–11] volatile trimethylplatinum(IV) chelates
technology are tightly connected with ever increasing based on various fluorinated
ꢀdiketones and their
requirements to the composition and structure of adducts with donor ligands. These works were conꢀ
β
novel functional materials. The nanostructures and
nanolayers based on platinum metals find wide use in
various fields of microelectronics, catalysis, etc. [1, 2].
cerned with the conditions of synthesis, spectral charꢀ
acteristics, and the thermal stability of the complexes.
It was noted that trimethylplatinum(IV) compounds
MetalꢀOrganic
Chemical
Vapor
Deposition
are more volatile than analogous platinum(II)
tonates, which we had thoroughly studied. From the
structural standpoint, fluorinated ꢀdiketonates of triꢀ
βꢀdikeꢀ
(
(MOCVD) is one of the methods suitable for forming
materials with specified functional properties [3,4].
Among the known volatile Pt(IV) compounds used
in CVD processes to obtain platinum coatings, platiꢀ
β
methylplatinum(IV) had not been studied before.
However, establishing the relationship between the
composition, structure, and thermal properties of
these compounds allows one to simplify the selection
of the most suitable precursors for CVD applications.
Analysis of the published data and the data from Camꢀ
bridge Crystallographic Data Centre (CCDC) conꢀ
firm the lack of structural studies of platinum(IV)
compounds of this type having practically valuable
num(IV) complexes with ꢀdiketones should be menꢀ
β
tioned first. Usually, platinum(IV) trialkyl comꢀ
pounds, most often, the most stable trimethylplatiꢀ
num iodide (CH ) PtI, are used as the starting
3
3
compounds [5]. Previously, it was known from the litꢀ
erature that trimethylplatinum(IV) forms dimeric
complexes with
CH–CO–R)]2, where R is a simple alkyl radical rangꢀ
ing from CH3 to C H [6, 7]. For example, in the properties.
β
ꢀdiketones given by [Me Pt(R–CO–
3
5
11
[
(CH ) Pt(Acac)] dimer, acetylacetone is a tridentate
3 3 2
As a continuation of our systematic research into
composition–structure–property” relationships of
ligand having, apart from the two donor oxygen atoms,
the third donor atom, namely, the middle ring carbon
“
volatile
describe the synthesis and Xꢀray diffraction study of
the crystal structure of volatile fluorinated ꢀdiketoꢀ
nates of trimethylplatinum(IV) with pyridine:
CH ) Pt(CH –CO–CH–CO–CF )Py and
II). These
ꢀdiketonates were not compounds were obtained from trifluoroacetylaceꢀ
reported in the literature. We were the first to syntheꢀ tone and hexafluoroacetylacetone, respectively.
βꢀdiketonates of noble metals, here we
atom, giving the bridging Pt⎯C bond, which forms the
γ
dimer. Due to low volatility, dimers of this type are less
suitable for CVD application than monomeric trimeꢀ
β
thylplatinum
tion of CF3 groups into chelating ligands facilitates the
volatility of complexes [8]. Before our studies, fluoriꢀ CH
nated trimethylplatinum
βꢀdiketonates. It is known that introducꢀ
(I)
3 3
3
3
)
Pt(CF
–CO–CH–CO–CF
)Py
3
(
3
3
3
β
680

VOLATILE FLUORINATED TRIMETHYLPLATINUM(IV)
β
ꢀDIKETONATES
681
EXPERIMENTAL
For C H F NO Pt
15
1
3
6
2
anal. calcd., %: C 29.6; H 2.8; F 21.7; N 2.6.
As the starting platinum(IV) compound, (CH ) PtI
III) was used.
3
3
Found, %:
С 29.7; H 2.6; F 21.5; N 2.3.
(
Synthesis of III. First, the Grignard reagent
–1
IR spectrum of II
(ν, cm ): 3080, 2963, 2898,
CH MgI was obtained from Mg powder (1.32 g,
3
2
1
816, 1638, 1607,1559, 1533, 1469, 1427, 1260, 1153,
090, 803, 758, 680, 584, 486, 401.
5
5 mmol) and CH3I (7.81 g, 55 mmol) in 50 mL of
anhydrous diethyl ether, then 60 mL of dry benzene
was added. Finely ground Na PtCl (1 g, 11 mmol),
The IR spectra of complexes
of 400–4000 cm were recorded on a Scimitar FTSꢀ
I
and II in the region
2
6
–1
which was thoroughly preꢀdehydrated in vacuum, was
quickly added at –20°С in an inert gas stream to the
vigorously stirred solution. The reaction mixture was
stirred in a constant inert gas stream for 2 h at 0°С; the
mixture gradually turned dark brown. The complex
was isolated from the reaction mixture into ice water
slightly acidified with HCl. The organic layer was sepꢀ
arated and the aqueous layer was repeatedly extracted
with hexane. The resulting compound was isolated by
evaporation of the solvent. Yield 0.61 g (75%). The
crystals of III are orangeꢀcolored, air stable, insoluble
in water but readily soluble in organic solvents.
2
000 spectrometer (KBr pellets).
XꢀRay diffraction. The single crystals of comꢀ
pounds
hexane at
I
and II were prepared from their solutions in
. The unit cell parameters and the experꢀ
0°С
imental intensities for crystal structure solution were
measured on a BrukerꢀNonius X8Apex fourꢀcircle
automated diffractometer (twoꢀcoordinate CCD
detector, Mo
monochromator,
K
radiation,
λ
= 0.71073 Å, graphite
scan mode). The structures
and II were solved by the direct method and refined
α
ϕ
ꢀ
and
ω
I
in the fullꢀmatrix anisotropic approximation. The
hydrogen atoms were specified geometrically and
Synthesis of I and II. Fluorinated trimethylplatiꢀ included in the refinement in the anisotropic approxiꢀ
num(IV)
ꢀdiketonates with pyridine were syntheꢀ mation together with nonꢀhydrogen atoms.
sized by the following procedure. Complex III (1 g,
.8 mmol) was dissolved in 50 mL of benzene. A soluꢀ experiment details are presented in Table 1, the interꢀ
tion of the potassium salt of the corresponding ligand atomic distances and bond angles are in Table 2. All
5.6 mmol) in 20 mL of 96% ethanol was added to the calculations were performed using the SHELXꢀ97
orange solution, and dry AgF (2.8 mmol) was added. program package (Bruker AXS Inc., 2004) [12]. The
The reaction mixture was stirred at 40–50°С until the Xꢀray diffraction patterns of
and II were fully
solution became colorless and AgI and KF precipiꢀ indexed based on the single crystal investigation data.
tated. The precipitate was filtered off, the solution was The atom coordinates and other parameters of and II
β
The crystallographic characteristics and Xꢀray
2
(
I
I
evaporated to dryness, the dry residue was dissolved in are deposited with the Cambridge Crystallographic
chloroform, dry pyridine (5.6 mmol) was added, and Data Centre (nos. 792536 for I and 791909 for II);
the solution was refluxed for 1 h. The solvent and the deposit@ccde.cam.ac.uk.
excess of pyridine were evaporated on a water bath at
reduced pressure. The dry residue was extracted with
hexane. The product isolated from hexane was puriꢀ
RESULTS AND DISCUSSION
fied by sublimation under reduced pressure. The yields
of complexes and II are 90–92%.
As the starting compounds for the synthesis of volꢀ
atile platinum(IV) ꢀdiketonates, we chose the most
stable trimethylplatinum iodide III. This complex was
I
β
Compound is a light yellow crystalline solid
I
first obtained [5] in a yield of not more than 20% by
(
mp = 40–41°C).
the reaction of the Grignard reagent CH MgI with
3
PtCl4. Later, the synthetic routes to III from various
chloro derivatives of platinum(IV) complexes were
studied [13]. However, the highest yield (52–55%) was
For C H F NO Pt
18
13
3
2
anal. calcd., %: C, 33.0; H, 3.8; F,12.0; N, 3.0.
Found, %: С, 33.1; H, 3.6; F, 12.3; N, 3.2.
attained in the reaction of Na PtCl6 with Grignard
2
reagent [14]. As a result of numerous experiments, we
improved this method for the synthesis of III. We
changed the order of mixing the reactants: the platiꢀ
num salt thoroughly preꢀdehydrated in vacuum was
–1
IR spectrum of
815,1617, 1516, 1474, 1449, 1364, 1287, 1137, 1068,
63, 781, 754, 692, 615,492,422.
I
(
ν
, cm ): 3078, 2961, 2902,
2
8
added to the Grignard reagent rather than vice versa
.
The optimal reactant and solvent ratios and the reacꢀ
Compound II is a light green crystalline solid tion temperature and time regimes were selected.
mp = 54–56°C). Thus, this method of the synthesis allowed the yield of
(
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 37
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682
ZHARKOVA et al.
Table 1. Crystallographic data and Xꢀray experiment details for complexes
I
and II
Value
Parameter
I
II
M
472.37
273(2)
526.35
150(2)
T, K
System
Monoclinic
Triclinic
Space group
P2 /n
1
P1
a
, Å
, Å
, Å
, deg
, deg
, deg
7.4618(3)
17.5425(6)
11.4282(4)
90
9.7564(3)
16.9091(6)
21.4192(6)
69.9360(10)
89.1770(10)
81.646(2)
3281.50(18)
8
b
c
α
β
93.9130(10)
90
γ
V
Z
ρ
μ
, Å3
1492.45(9)
4
(calcd.), g/cm3
2.102
2.131
, mm–1
9.434
8.619
Mo
F(000)
896
1984
Crystal size, mm
Measurement range,
Range of indices
Ihkl measured
0.02
2.93–36.28.
12, –29 16, –18
18449
×
0.02
×
0.02
0.28
1.90–30.51.
13, –24 24, –29
34834
×
0.04
×
0.04
θ, deg
–11
≤
h
≤
≤
k
≤
≤
l
≤
14 –13
≤
h
≤
≤
k
≤
≤
l ≤ 30
Ihkl independent
7121 (Rint = 0.0200)
19704 (Rint = 0.0226)
Number of reflections with Ihkl > 2
σ
(
I
)
15657
841
6173
253
Number of refined parameters
2
hkl
1.057
1.024
GOOF for
F
R
R
factor (
I
> 2
σ
(
I
)
R1 = 0.0183, wR2 = 0.0387
R1 = 0.0242, wR2 = 0.0397
1.598/–0.938
R1 = 0.0280, wR2 = 0.0596
R1 = 0.0432, wR2 = 0.0596
1.368/–1.012
factor (all reflections)
Residual electron density (max/min), e
/Å3
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VOLATILE FLUORINATED TRIMETHYLPLATINUM(IV)
β
ꢀDIKETONATES
683
Table 2. Bond lengths and bond angles in complexes
I
and II (the mean values are in parentheses)
I
II
Bond
d, Å
Pt–CH3
Pt–O
Pt–N
N–C
2.025(2)–2.036(2) 2.030
2.153(1), 2.157(1) 2.155
2.022(4)–2.038(4) 2.030
2.153(3)–2.168(2) 2.161
2.165(3)–2.197(3) 2.181
1.334(4)–1.342(4) 1.376
1.352(8)–1.385(5) 1.376
1.249(4)–1.261(4) 1.255
1.384(5)–1.402(5) 1.394
1.522(5)–1.533(5) 1.528
1.244(7)–1.327(5) 1.302
2.184(1)
1.342(2), 1.349(2) 1.346
1.378(3)–1.387(3) 1.383
C–C
1
.259(2), 1.273(2)
.426(2), 1.379(2)
.500(2), 1.531(2)
O–C
1
C–C
γ
1
C–CMe
C–F
1.332(2)–1.342(2) 1.338
Angle
ω, deg
OPtO
88.81(5)
85.23(9)–93.69(8) 89.46
III to be increased to 75%. A study of the structure of water molecule are formed. Thus, fluorinated
βꢀdikeꢀ
III was reported [15].
tonates of trimethylplatinum do nor form dimers
through Pt–C bonding, as has been the case for trimꢀ
sis of trimethylplatinum chelates, we expected the forꢀ ethylplatinum chelates with phenyl or alkyl substituꢀ
While using fluorinated
β
ꢀdiketones for the syntheꢀ
γ
mation of dimeric chelates similar, for example, to triꢀ ents in the
methylplatinum acetylacetonate [(СH ) Pt(Acac)]2,
as the trifluoromethyl group should not create steric
hindrance for the dimer formation [16]. However, it
β
ꢀdiketonate ligand. Apparently, the
increase in the electronegativity of the terminal
diketonate radical entails the growth of the positive
charge of the ligand ꢀС atom and, hence, the probaꢀ
3
3
βꢀ
γ
was found in the experiments that fluorinated ꢀdikeꢀ
tones do not form dimeric complexes. An obligatory
condition for the formation of a monomeric fluoriꢀ
β
bility of formation of the Pt–C bond decreases, thus
enabling binding of platinum to other donor moleꢀ
γ
nated
ꢀdiketonate of trimethylplatinum is the presꢀ cules. Note that water adds to the chelate complex
β
ence of donor molecule, for example, H O, in the molecule only in the case of fluorinated
β
ꢀdiketones.
2
reaction medium. This molecule occupies the sixth
Pyridine, which is a stronger base, easily displaces
water from these monomeric complexes. Note also
that initially, we used only the potassium salts of
coordination site of platinum in the monomeric
diketonate complex. This is why we failed to obtain
fluorinated ꢀdiketonates of trimethylplatinum in
anhydrous solvents. Upon the addition of some water
in the reaction medium (it is sufficient to use 96% ethꢀ
β
ꢀ
β
ligands (KLF) for the synthesis of fluorinated
βꢀdiketꢀ
onates. In this case, the yield of the target products did
anol), monomeric fluorinated complexes containing a not exceed 50%.
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684
ZHARKOVA et al.
C(3M)
C(1M)
C(2M)
Pt(1)
C(1)
N(1)
O(2)
F(2)
O(1)
C(6)
C(8)
C(2)
C(10)
C(5)
C(7)
C(9)
C(3)
C(4)
F(1)
F(3)
Fig. 1. Structure of the complex Pt(CH ꢀCOꢀCHꢀCOꢀCF )Py (I).
3
3
By using silver ions, we were able to prepare fluoriꢀ 1.8°. In the
nated ꢀdiketonates of trimethylplatinum(IV) in up to between O–C, С–С
2% yield. side of different substituents are 0.014, 0.047, and
.031 Å, respectively. In the CF3 group, the C–Fmean
βꢀdiketonate ligand, the differences
β
γ, and С–СМеbond lengths on the
9
0
The IR spectra of
distance is 1.34 Å. The folding angle of the chelate ring
of platinum bonding to
along the ⋅⋅⋅ line reaches 14.7°, the intramolecular
I
and II confirm the chelate type
βꢀdiketone. The C–H and Pt–
O
O
–1
СН3 stretching vibrations occur at 3000–2800 cm .
F(1)⋅⋅⋅ contact is 2.39 Å. The mean C–N and C–C
H
γ
Characteristic C–O and C–C vibrations of the chelate
bond lengths in the pyridine molecule are 1.34 and
.38 Å, respectively. The angle between the normals to
the Py and ꢀdiketonate ligand planes is 91°
–1
ring occur at 1650–1450 cm . The (Pt–C) vibrations
1
–
1
account for the less intense bands at 500–600 cm
[
β
.
–1
17]. The bands at 400–1800 cm for pyridine vibraꢀ
tions are difficult to analyze due to the large number of
The packing of structural units in the crystal of
absorption bands corresponding to the chelate ring. along the axis is shown in Fig. 2. The complex moleꢀ
cules are packed in the crystal with minimum Pt⋅⋅⋅Pt
for II) were assigned to pyridine =C–H stretching distances of 6.639–7.462 Å. The ⋅⋅⋅ intermolecular
bands [18]. contacts are 2.65–2.86 Å long.
I
x
–1
–1
The weak bands at 3078 cm (for I) and 3080 cm
(
H F
The molecular structure of compound The structure of compound II is also molecular,
I consists of
neutral complexes (СН ) Pt(tfac)Py (Fig. 1). The platꢀ being composed of neutral (СН ) Pt(Hfac)Py comꢀ
3
3
3 3
inum atom is coordinated by two oxygen atoms of the plexes. The structure comprises four crystallographiꢀ
unsymmetric ligand, by the pyridine nitrogen atom, cally independent complexes with similar structures.
and by three three methyl carbon atoms. The PtC NO2 The Pt coordination polyhedra are slightly distorted
3
coordination unit is a slightly distorted octahedron. octahedra. The structure of one of the complexes II is
The Pt–Omean distance is 0.029 Å shorter than the Pt– shown in Fig. 3. The mean Pt–O, Pt–N, and Pt–CH3
Nmean distance. The Pt–CH bonds are 2.030 Å and bond lengths are 2.160, 2.181, and 2.030 Å, respecꢀ
3
the chelate OPtO bond angle is 88.8°. Two triangular tively. The deviations of the cis bond angles at Pt from
faces (С3 and О N) of the platinum octahedron are the ideal values of 90
°
do not exceed 4.8°. The planes
2
nearly parallel, the angle between their planes being of two triangular faces of the Pt octahedra are nearly
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 37
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VOLATILE FLUORINATED TRIMETHYLPLATINUM(IV)
β
ꢀDIKETONATES
685
0
z
x
y
Fig. 2. Packing of the complexes in structure
I
along the
x
axis.
parallel, the dihedral angles not exceeding 2.4°. In the
symmetric ligand of this complex, the mean O–C, С– ethylplatinum(IV) compounds showed that fluoriꢀ
, С–СМе, and C–F bond lengths are 1.255, 1.394,
.528, and 1.302 Å, respectively. The mean value for
the chelate OPtO angle is 89.46°. The folding angles of
the chelate rings at the ⋅⋅⋅ lines are 4.0°–8.2°. All
intramolecular ⋅⋅⋅ contacts in complex II are
2.3 Å. The average bond lengths of the pyridine molꢀ
Thus, our study dealing with the synthesis of trimꢀ
С
1
γ
nated ꢀdiketones do not form dimeric complexes. A
β
condition for the formation of monomeric complexes
is the presence of a donor molecule in the reaction
mixture able to occupy the sixth coordination site at
the platinum atom. An Xꢀray diffraction study of volaꢀ
tile trimethylplatinum(IV) complexes with fluorinated
O
O
F
H
γ
~
ecule in structure II are the same as in
between the normals to the pyridine and
ligand planes is 72.7°–90°
I
β
. The angle
ꢀdiketonate
β
ꢀdiketones was carried out for the first time. The
crystal structures and the geometric characteristics of
complexes and II were determined. Both structures
.
I
The projection of structure II onto the xy plane is
shown in Fig. 4. The structure is layered, F and H
atoms of the terminal substituents being located on the
layer surfaces. The minimum values for the intermoꢀ
are molecular and monomeric, the molecules in the
crystal being linked by only weak van der Waals forces.
The platinum coordination polyhedron is a slightly
distorted octahedron; the shortest Pt⋅⋅⋅Pt distances are
lecular
.58 Å, and 2.38 Å. The shortest Pt⋅⋅⋅Pt distances
between the centers of the complexes are in the range Pt–N, and Pt–C bond lengths are 2.157, 2.182, and
from 6.254 to 6.517 Å. 2.030 Å.
F
⋅⋅⋅F, F ⋅⋅⋅H
, and
Н
⋅⋅⋅Н contacts are 2.87 Å,
6
.639 Å (for I) and 6.254 Å (for II). The mean Pt–O,
2
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686
ZHARKOVA et al.
F(2)
F(1)
C(4)
F(3)
C(2)
C(3)
O(2)
F(4)
C(11M)
F(6)
C(5)
C(1)
C(12M)
O(1)
Pt(1)
F(5)
C(11)
N(1)
C(13M)
C(12)
C(15)
C(14)
C(13)
Fig. 3. Structure of the complex (CH ) Pt(CF ꢀCOꢀCHꢀCOꢀCF )Py (II).
3
3
3
3
0
z
x
y
Fig. 4. Projection of structure II onto the xy plane.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 37
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VOLATILE FLUORINATED TRIMETHYLPLATINUM(IV)
β
ꢀDIKETONATES
687
ACKNOWLEDGMENTS
10. Zharkova, G.I., Igumenov, I.K., and Zemskov, S.V.,
Koord. Khim., 1983, vol. 9, no. 6, p. 845.
The authors are grateful to N.V. Kuratiev for perꢀ
forming Xꢀray diffraction analysis.
1
1. Igumenov, I.K., Zharkova, G.I., Isakova, V.G., and
Zemskov, S.V., Teoreticheskaya i prikladnaya khimiya
β
ꢀdiketonatov metallov (Theoretical and Applied
Chemistry of Metal ꢀDiketonates), Moscow: Nauka,
985, p. 36.
β
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