The volatile trimethylplatinum(IV) complexes: Effect of β-diketonate substituents on thermal properties

Article abstract of DOI:10.1016/j.poly.2020.114475

The series of trimethylplatinum(IV) complexes with a general formula (CH₃)₃Pt(L)Py: [L^? = β-diketonate ligand: (1) ^tBuC(O)CHC(O)C(OCH₃)(CH₃)₂) – L¹, (2) CF₃C(O)CHC(O)CC(CH₃)₂ (OCH₃)) – L², (3) CF₃C(O)CHC(O)C₄H₃S – ttfa, (4) CF₃C(O)CHC(O)^tBu – ptac, Py –pyridine] were synthesized with high yields using novel synthesis technique based on the interaction of (CH₃)₃PtI with an appropriate PbL₂. A number of methods including elemental analysis, IR and NMR spectroscopy, were used to identify the purity of complexes. Both 1 and 3 crystals are monoclinic, P2₁/n, Z = 4. The crystallographic parameters are: a = 9.3199(11)?, b = 16.1798(19)?, c = 14.1544(13)?, β = 90.090(4)°, V = 2134.4(4)?³ for 1; a = 10.5676(3)?, b = 17.1804(5)?, c = 12.0353(4)?, β = 90.7430(10)°, V = 2184.89(11)?³ for 3, respectively. The temperature dependences of saturated vapor pressure of the complexes were measured using Knudsen method giving logP = 17.3–6908/T, ΔT = 326–353 K and logP = 17.7–6793/T, ΔT = 303–333 K, for 1 and 4, respectively. The effect of substituents combination in L on thermal stability of (CH₃)₃Pt(L)Py vapors was studied using mass spectrometry. The energies of Pt[sbnd]N(Py) bonds of (CH₃)₃Pt(L)Py calculated using DFT approach were in the ranges of 78.97–92.73 and 73.32–83.09 kJ/mol depending on Py rings orientation.

Full text of DOI:10.1016/j.poly.2020.114475

Journal Pre-proofs
The volatile trimethylplatinum(IV) complexes: effect of β-diketonate substitu‐
ents on thermal properties
Svetlana I. Dorovskikh, Vladislav V. Krisyuk, Irina V. Mirzaeva, Vladislav
Yu. Komarov, Sergey V. Trubin, Asia E. Turgambaeva, Natalia B. Morozova
PII:
S0277-5387(20)30132-7
DOI:
Reference:
https://doi.org/10.1016/j.poly.2020.114475
POLY 114475
To appear in:
Polyhedron
Received Date:
Revised Date:
Accepted Date:
12 November 2019
28 January 2020
25 February 2020
Please cite this article as: S.I. Dorovskikh, V.V. Krisyuk, I.V. Mirzaeva, V. Yu. Komarov, S.V. Trubin, A.E.
Turgambaeva, N.B. Morozova, The volatile trimethylplatinum(IV) complexes: effect of β-diketonate substituents
on thermal properties, Polyhedron (2020), doi: https://doi.org/10.1016/j.poly.2020.114475
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The volatile trimethylplatinum(IV) complexes: effect of β-diketonate
substituents on thermal properties
Svetlana I. Dorovskikh 1,2*, Vladislav V. Krisyuk , Irina V. Mirzaeva , Vladislav Yu.
1
1,2
1
,2
1
1
1
Komarov , Sergey V. Trubin , Asia E. Turgambaeva , Natalia B. Morozova
1Nikolaev Institute of Inorganic Chemistry, SB RAS, Lavrentiev Ave. 3, 630090 Novosibirsk,
Russia
2
Novosibirsk State University, 2, Pirogova Str., 630090 Novosibirsk, Russia
Abstract
-
The series of trimethylplatinum(IV) complexes with a general formula (CH ) Pt(L)Py: [L =
3
3
t
1
β-diketonate ligand: (1) BuC(O)CHC(O)C(OCH )(CH ) ) – L , (2) CF C(O)CHC(O)CC(CH )
3 2
3
3 2
3
2
t
(
OCH )) – L , (3) CF C(O)CHC(O)C H S – ttfa, (4) CF C(O)CHC(O) Bu – ptac, Py –pyridine]
3 3 4 3 3
were synthesized with high yields using novel synthesis technique based on the interaction of
CH ) PtI with an appropriate PbL . A number of methods including elemental analysis, IR and
(
3
3
2
NMR spectroscopy, were used to identify the purity of complexes. Both 1 and 3 crystals are
monoclinic, P2 /n, Z = 4. The crystallographic parameters are: a = 9.3199(11)Å,
1
3
b = 16.1798(19)Å, c = 14.1544(13)Å, β = 90.090(4)º, V = 2134.4(4)Å for 1; a = 10.5676(3)Å,
3
b = 17.1804(5)Å, c = 12.0353(4)Å, β = 90.7430(10) º, V = 2184.89(11)Å for 3, respectively.
The temperature dependences of saturated vapor pressure of the complexes were measured using
Knudsen method giving logP = 17.3 – 6908/T, ΔT = 326-353 K and logP = 17.7 – 6793/T, ΔT =
3
03-333 K, for 1 and 4, respectively. The effect of substituents combination in L on thermal
stability of (CH ) Pt(L)Py vapors was studied using mass spectrometry. The energies of Pt–
3
3
N(Py) bonds of (CH ) Pt(L)Py calculated using DFT approach were in the ranges of 78.97-92.73
3
3
and 73.32-83.09 kJ/mol depending on Py rings orientation.
Keywords: trimethylplatinum(IV) β-diketonate complexes, vapor pressure, DFT calculations,
mass spectrometry, MOCVD.
*
corresponding author, e-mail: reter16@yandex.ru

Introduction
MOCVD (Metal-Organic Chemical Vapor Deposition) and related methods are the promising
techniques to produce Pt-containing materials widely utilized as catalysts of dehydrogenation
and many other reactions [1-4], electro- or photocatalysts of hydrogen generation and
decarboxylation reactions [4-8], fuel cells [9-10], protective layers [11], electrodes [12], and so
on. Our latest reports demonstrated a high potential of MOCVD to produce Pt coatings with
enhanced surfaces on the pole tips of endocardial electrodes [13, 14].
The success in obtaining a target film by MOCVD depends significantly on the thermal
characteristics of an initial compound (precursor). Indeed, the temperature intervals of the
MOCVD process can be correctly determined only from the data on the precursor volatility and
stability in the solid phase under the transport conditions and features of the precursor vapor
fragmentation [15]. On the other hand, the metal coordination environment significantly affects
the thermal properties of an appropriate compound. The establishment of compound structure –
thermal properties correlations is a key to both choice of the appropriate precursor and
optimization of the deposition of Pt-based materials with the required characteristics.
Among platinum MOCVD precursors, trimethylplatinum derivatives are the most demanded
ones due to their quite high volatility and wide deposition temperature window [16, 17]. While
the trimethylplatinum(IV) cyclopentadienyl derivatives are the well-characterized precursors
used for depositing conformal coatings, their closest analogues, namely, trimethylplatinum
β-diketonate
complexes
with
the
general
formula
(CH ) Pt(L)Q
(L
–
3
3
β-diketonate ligand, Q – neutral ligand) are not widely used because of limited information on
their thermal characteristics.
In general, there are two possibilities to regulate the thermal behavior of (CH ) Pt(L)Q: via
3
3
changing L or via the Q ligand. In our previous report, the advantages of using a strong donor Q
ligand have been demonstrated [18-23]. The use of the Py group instead of weak donor H O
2
-
resulted in obtaining fluorine-free (CH ) Pt(L)Py (L = MeC(O)CHC(O)Me – acac,
3
3

t
t
BuC(O)CHC(O) Bu) – thd). On the other hand, we synthesized and characterized some
-
(
CH ) Pt(L)Py complexes, including (CH ) Pt(L)Py (L = CF C(O)CHC(O)CF – hfac,
3
3
3 3
3
3
CF C(O)CHC(O)Me – tfac), to determine their suitability for MOCVD applications. In the
3
1
present
work,
we
describe
new
L1
fluorine-free
(CH ) Pt(L )Py
(1)
3
3
(tBuC(O)CHC(O)C(CH ) (OCH ))
–
and (CH ) Pt(L)Py
(2)
with
3
2
3
3 3
2
(
CF C(O)CHC(O)CC(CH ) (OCH ) – L , (3) with CF C(O)CHC(O)C H S – ttfa, (4) with
3 3 2 3 3 4 3
t
CF C(O)CHC(O) Bu – ptac) complexes obtained by a novel synthesis technique. The effect of
3
the substituents combination in L on the thermal characteristics (volatility and stability on
heating) of (CH ) Pt(L)Py complexes and the energy of the weakest Pt–Py bond were studied.
3
3
2
. Experimental
2
.1. Materials
The initial [(CH ) PtI] (solid, orange) is available reagent provided by JSC “Krastsvetmet”
3
3
4
(
www.krastsvetmet.ru, 95 %). In addition, the elemental analysis: Anal. Calcd. for PtC H I (%):
3 9
C, 9.98; H, 2.47. Found: C, 10.30; H, 2.50 was done. The Pb β-diketonates were synthesized and
purified according the procedures described in [24-26]. The commercially available Py
(“Reachem”, 99 %) was used without additional purification. The synthetic procedures were
conducted in dry benzene.
2
.2. Synthesis and identification
Compounds 1-4 were synthesized similarly by the reaction of [(CH ) PtI] (1g, 2.7 mmol)
3
3
4
with the appropriate lead complex PbL (1.4 mmol) in the presence of Py (0.2 mL, 2.7 mmol).
2
The refluxing of the reaction mixture for 2 hours led to the precipitation of an orange solid
(
PbI ). The precipitate was separated and the solution was evaporated in air, giving a crude
2
product. The crude products were purified by vacuum sublimation in a gradient tube oven (P~
-2
1
0 Torr and T = 70–90°C), yielding crystalline complexes 1, 4. Oily complexes 2 and 3 were

purified by column chromatography on a silica gel (CAS 112926-00-8, pore size 150 Å, 200-425
mesh) using a chloroform-hexane mixture as an eluent.
The yield of 1 was 95%, white solid, m.p. 82–83°C. Found, %: С, 44.27; H, 6.09, N 2.44. For
-1
PtC H O N calculated, %: С, 44.01; H, 6.41, N 2.70. IR (KBr; υ/cm ): υ(C–H) 3098 (m), 3003
1
9
33
3
(
m), 2987 (m); ν(O–CH ) 2832(m); υ(C=О + С=С) 1592 (s), 1501 (m), 1489 (s); δ(H–C–H)
3
1
1
447 (m), 1375 (s); υ(Pt–C, Pt–N, Pt–O) 650-520. H NMR (25 C, 500 MHz, CDCl ,
3
δ, ppm): δ=1.01 [3H, Pt–CH , J
= 74Hz], δ=1.00 [3H, Pt–CH , J
= 74Hz], δ=0.77 [3H, Pt–
Pt-H
3
Pt-H
3
CH , J
= 72Hz], δ=1.11 s [9H, C(CH ) ], δ=1.24 s [3H, CαCH ], δ=1.33 s [3H, CαCH ],
3 3 3 3
3
Pt-H
δ=3.12 s [3H, OCH ], δ=5.68 s [1H, Cγ–H], δ=7.38 m [2H, Py], δ=7.83 t.t. [1H, Py], δ=8.50 m
3
1
3
[
2H, Py]; С NMR (25 C, 125.76 MHz, CDCl δ, ppm): δ=-12.9 [CH –Pt, J
= 763 Hz],
C–Pt
3
3
δ=-12.6 [(CH –Pt, J
= 763 Hz)], δ=-9.6 [CH –Pt, J
= 720Hz],δ=24.6 [(C(OCH )(СH ) –
3
C–Pt
3
C–Pt
3
3 2
)
], δ=24.7 [(C(OCH )(СH ) –)], δ=28.3 [(C(СH ) –)], δ=41.0 [(C(СH ) –)], δ=51.2 [(OCH )],
3
3 2
3 3
3 3
3
δ=80.6 [(C(OCH )],δ=89.5 [(C H),J = 29 Hz], δ=124.9[Py, C-2, C-6, JC–Pt = 10 Hz],δ=137.5
C–Pt
3
γ
[
Py, C-4], δ=148.6 [Py, C-3, C-5], δ=190.2 [(OCH )(CH ) –CO], δ=196.1 [(C(СH ) –CO]; 195Pt
3 3 2 3 3
NMR (107.3 MHz, CDCl ), δ, ppm: -1910.2. EI MS (70eV): m/z (%) (CH ) Pt(L )Py (for 195Pt):
1
3
3 3
+
+
+
+
5
–
18(9) [M] , 489(9) [M – C H ] , 439(12) [M – Py] , 424(21) [M – Py – CH ] , 409(14) [M – Py
2 5 3
+
+
+
1 +
C H ] , 383(52) [M – Py – C H )] , 366(29) [M – Py – C H O)] , 319(31) [M – (L )] , 303(21)
2
6
4
8
4
9
+
+
+
+
+
[
C Н PtPy] , 289(12) [CН PtPy] , 274(12) [PtPy] , 240(100) [(CH ) Pt] , 223(19) [C H Pt] ,
2 5 3 3 3 2 4
+
2
09(10) [CH Pt] .
2
The yield of 2 was 93%, light yellow oil. Found, %: С 36.18; H 4.89; N 2.72; F 11.08. For
-1
C H NO F Pt calculated, %: С, 36.23; H, 4.56, N 2.64, F 10.74. IR (KBr; υ/cm ): υ(C–H)
1
6
24
3 3
3
1
105 (w), 3091 (w), 2967 (m); υ(O–CH ) 2895 (s); υ(C=О + С=С) 1617 (s), 1591 (w), 1540 (w),
3
512 (s); δ(H–C–H) 1450 (m), 1365 (s); υ(C–F) 1255 (m), 1184 (m), 1138 (s); υ(Pt–C, Pt–N, Pt–
1
O) 635-423. H NMR (25 C, 500 MHz, CDCl ): δ=0.85 [(3H, Pt–CH , J
= 71 Hz)], δ=1.14
3
3
Pt-H
[
(3H, Pt–CH , J
= 76 Hz)], δ=1.17[(3H, Pt–CH , J
= 76 Hz)],δ=1.25 s [3H, CαCH3],
Pt-H
3
Pt-H
3
δ=1.34 s [3H, CαCH ], δ=3.12 s [3H, OCH ], δ=5.95s [ Cγ–H], δ=7.44 m [ (2H, Py)], δ=7.88
3
3

1
3
t.t.[(1H, Py)], δ=8.48 m [ (2H, Py)]; С NMR (25 C, 125.76 MHz, CDCl ): δ=-12.1 [CH –Pt,
3
3
JC–Pt = 768 Hz],δ=-11.4 [(CH –Pt, J
= 772 Hz)], δ=-8.8 [CH –Pt, J
= 712 Hz],δ=23.8
3
C–Pt
3
C–Pt
[
(C(OCH )(СH ) –)],δ=51.5[(OCH )], δ=80.9 [(C(OCH )],δ=92.71 [(CγH), J
= 26 Hz)],
3
3 2
3
3
C–Pt
δ=118.8 [(CF –), J = 287 Hz], δ=125.4[Py, C-2, C-6, JC–Pt = 10 Hz],δ=138.0 [Py, C-4],
3
C-F
1
9
δ=148.4 [Py, C-3, C-5], δ=168.3 [(CF –CO, J
= 31 Hz)], 198.6 [(C(СH ) –CO)]; F NMR
3 3
3
C–F
1
95
(
(
(
[
470.6 MHz, CDCl ), δ, ppm: -75.07; Pt NMR (107.3 MHz, CDCl ), δ, ppm: -1927.3. EI MS
3
3
2
195
+
+
70eV): m/z (%) (CH ) Pt(L )Py (for Pt): 530(13) [M] , 500(25) [M – C H )] , 319(100) [M –
3
3
2
6
2
+
+
+
+
+
L )] , 303(61) [C Н PtPy] , 289(68) [CН PtPy] , 274(68) [PtPy] , 240(71) [(CH ) Pt] , 223(57)
2
5
3
3 3
+
+
C H Pt] , 209(36) [CH Pt] .
2
4
2
The yield of 3 was 92%, light green liquid (crystalls can be grown at cooling to 270K).
Found, %: С 36.00; H 3.16; N 2.55; F 10.81, S 6.11. For C H NSO F Pt calculated, %: С
1
6
18
2 3
-
1
3
2
1
5.56; H 3.36; N 2.59; F 10.55; S 5.93. IR (KBr; υ/cm ): υ(C–H) 2953 (w), 2892 (w), 2967 (m),
814 (s); υ(C=О + С=С) 1595 (s), 1584 (sh), 1533 (s), 1484 (w); υ(S=С) 1410 (s), δ(H–C–H)
1
349 (s), 1342 (s); υ(C–F) 1255 (m), 1194 (m), 1132 (s); υ(Pt–C, Pt–N, Pt–O) 685-423. H NMR
(
25 C, 500 MHz, CDCl ): δ=0.96 [(3H, Pt–CH , J
= 70 Hz)], δ=1.19 [(3H, Pt–CH , J
=
Pt-H
3
3
Pt-H
3
7
6 Hz)], δ=1.24[(3H, Pt–CH , J
= 76 Hz)],δ=6.042 [s, Cγ–H], δ=7.10 s [H, (C H S)],
Pt-H 4 3
3
δ=7.43m [(2H, Py)], δ=7.60 s [H, (C H S)],δ=7.70 s [H, (C H S)], δ=7.85t.t [ 1H, Py], δ=8.56m
4
3
4
3
1
3
[
(2H, Py)]; С NMR (25 C, 125.76 MHz, CDCl ): δ=-11.9 [CH –Pt, J
= 773 Hz], δ=-11.3
3
3
C–Pt
[
(CH –Pt, J
= 773 Hz)], δ=-8.8 [CH –Pt, J
= 712 Hz], δ=91.5 [(CγH), JC–Pt = 25 Hz)],
3
C–Pt
3
C–Pt
δ=118.9 [(CF –), J = 286 Hz], δ=125.4 [Py, C-2, C-6, JC–Pt = 10 Hz], δ=128.2 [(C H S)],
3
C-F
4
3
δ=129.2 [(C H S)], δ=132.0 [(C H S)], δ=138.0 [Py, C-4], δ=145.6 [(C H S)],δ=148.4 [Py, C-3,
3
4
3
4
3
4
1
9
C-5], δ=167.9 [(CF –CO, J = 32 Hz)], 178.0 [(C H S)–CO)]; F NMR (470.6 MHz, CDCl ),
3
C–F
3
4
3
δ, ppm: -74.98; 195Pt NMR (107.3 MHz, CDCl ), δ, ppm: -1928.7.
3
The yield of 4 was 95% light green solid, m.p. 95–97°C. Found, %: С 37.48; H 4.79; N 2.62;
F 11.11. For C H NO F Pt calculated, %: С 37.35; H 4.67; N 2.66; F 10.82. EI MS (70eV):
1
6
24
2 3
1
95
+
+
+
m/z (%) (CH ) Pt(ptac)Py (for Pt): 514(20) [M] , 486(23) [M - C H ] , 435(20) [M – Py] ,
3
3
2
4

+
+
+
4
19(26) [M – Py – CH )] , 377(26) [M – Py – C H ] , 319(64) [M – (ptac)] , 303(79)
4 4 10
+
+
+
+
+
[
C Н PtPy] , 289(55) [CН PtPy] , 274(58) [PtPy] , 240(100) [(CH ) Pt] , 223(42) [C H Pt] ,
2 5 3 3 3 2 4
+
2
09(28) [CH Pt] .
2
2
.3. Methods
The C, H, N, S, F analysis of compounds was performed on CARLO-ERBA-11008 elemental
analyzer. IR spectra were recorded as KBr disc on a SCIMITAR FTS 2000 spectrometer at room
-1
195
19
13
1
temperature in the region of 4000–400 cm . Pt, F, C and H NMR experiments on the
samples dissolved in CDCl placed in 5 mm NMR tubes were performed on the Bruker Avance
3
III 500 MHz spectrometer. 195Pt NMR shifts were referenced to external Na PtCl in D O. C
13
2
6
2
1
19
and H shifts were referenced to external tetramethylsilane standard. F shifts were referenced to
external CFCl3.
2
.4. Single-crystal X-ray analysis
Crystals of 1 suitable for X-ray analysis were grown by vacuum sublimation, whereas the
crystals of 3 were obtained at cooling appropriate C H solution to –30°C. The unit cell
6
12
parameters and experimental diffraction intensities were measured via Bruker Apex Duo four-circle
diffractometer with a 2D CCD detector using graphite monochromated MoKα radiation at 150 K
[
27]. The structures were solved by SHELXT [28] and refined by SHELXL [29] assisted with Olex2
GUI [30] in anisotropic approximation for ordered non-H atoms atomic displacement parameters
ADP). Non-H atoms from disordered residues of the structure 1 were refined isotropically with a
(
number of geometrical and ADP restrictions. The positions of H atoms were determined
geometrically and refined in a rider model. Crystallographic data for the studied phases have been
deposited with the Crystal data and structural refinement details are summarized in Table 1. CCDC
1954673 (for 1) and 1954674 (for 3) contain the supplementary crystallographic data for this paper.

This data can be obtained free of charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/structures.
2
.5. Thermo-chemical measurements
The thermal properties of the 1–4 complexes in the condensed phase were studied by means
of TG-DTA using NETZSCH STA 409 PC/PG device. The experiments were performed in a
–
1
–1
helium flow (30 mL min ) with a heating rate of 10°C min in the range temperature of 25–
4
00°C, portion weight 6-7 mg, the standard open crucibles were used.
The temperature dependences of saturated vapor pressure of 1 and 4 complexes were
measured by the Knudsen effusion method using mass spectrometric technique according to the
procedure described elsewhere [36]. The partial pressure of saturated vapor of studied complexes
was obtained from the following equation:
(1)
Here m – mass of the compound evaporated during whole experiment, I is the ion peak intensity,
i
measured at the established temperature T , S – Klausing coefficient for the effusion orifice, M
i
eff
–
~
molecular mass. The error of measurement of the partial pressure of saturated vapor was
10%. The experimental data of 1 and 4 are summarized in the Supporting information. The
thermodynamic parameters (H , S °) of sublimation processes of the complexes were
Т*
Т*
calculated from equations logP(Torr) = A – B/T(K) obtained from experimental data
Appendices).
(
2
.6. Mass spectrometric study
A time-of-flight mass spectrometer equipped with a specially designed input system imitating
a miniature CVD reactor was used to analyze the gas phase [32]. Approximately 1-2 mg of the

compound was placed in an open glass ampoule and kept at constant temperatures of 130, 105,
o
9
4 C for 1, 2, and 4, respectively, in the evaporator under dynamic vacuum conditions. The
o
vaporized compound enters into the reactor heated at a rate of 5 /min. The reactant gas (O ) was
2
fed directly to the reactor. Pressure in the reactor was about 100 Pa. The gas phase mixture was
transferred continuously from the reactor to the mass spectrometer ion source through the 0.2
mm effusive orifice. Ionization was performed by electrons with energy of ca. 70 eV.
Experimental data were obtained as full-range mass spectra recorded every 2 min.
2
.7. DFT calculations
All calculations were performed with the ADF2017 program suit [33] using a DFT approach
combining the Perdew-Burke-Ernzerhof (PBE) [34] functional and the all-electron set of Slater-
type triple-ζ basis functions with an additional set of polarization functions (TZP/ADF). Scalar
relativistic effects were included via the Zeroth Order Regular Approximation (ZORA) approach
[35]. Solvation effects were included via the conductor-like screening model (COSMO)
approach as implemented in ADF [36]. For each compound, the energy of the Pt–N bond was
calculated as the difference between the energies of the formation (with correction for zero-point
vibration energies) of the optimized structure of the compound and the sum of energies of the
formation of pyridine and the compound without the pyridine ligand. For all the optimized
structures, the absence of imaginary frequencies indicates that the structures are indeed the local
minima on the corresponding potential energy surfaces.
3
. Results and Discussion
3
.1. Synthesis and crystal structures of (CH ) Pt(L)Py
3
3
Trimethylplatinum compounds are typically synthesized by interaction of [(CH ) PtI] with
3
3
4
appropriate ligands giving octahedral platinum complexes [37]. In our previous report, a series of
CH ) PtLPy complexes was synthesized using the strategy based on the isolation of
(
3
3

intermediates (CH ) PtLH O or [(CH ) PtL] which further interacted with Py giving the target
3
3
2
3 3
2
products [18, 23]. The efficiency of this synthetic approach depends mainly on a yield of an
appropriate intermediate. Moreover, the combination of substituents in the L ligand affected the
yields. Indeed, the fluorine-containing (CH ) PtLPy complexes were obtained with yields of 88-
3
3
9
2%, while the yields of the fluorine-free analogues reached 95%. Hence, the alternative
synthesis technique based on following reaction (Scheme 1) was proposed.
The use of Pb(L) as a source of L improves the efficiency of the ligand exchange
2
reaction due to the formation of insoluble solid PbI . Moreover, the high solubility of Pb(L) in
2
2
benzene allows us to exclude the use of an excess of L and AgF reagents. The absence of a
reducing agent such as ethanol excludes Pt-black formation and so leads to an increase in the
yields of (CH ) PtLPy complexes.
3
3
The advantages of the proposed approach were confirmed on the example of complex 4.
Hence, this complex has been obtained with a yield of 95%, whereas its yield did not exceed
8
8% in [23]. In addition, three novel complexes were synthesized using the new technique.
Hence, the presented technique is a simple and universal way to synthesize (CH ) PtLPy with
3
3
yields up to 95%.
According to the single crystal X-ray diffraction data, both 1 ([(CH ) PtL Py]) and 3
1
3
3
(
[(CH ) Pt(ttfa)Py]·n-C H ) compounds crystallized in the monoclinic space group P2 /n. The
3 3 6 14 1
structures of both complexes 1 and 3 are formed by neutral molecules located in general
positions, while the platinum cations have an octahedral Pt(C O N) coordination core. In the
3
2
structures of complexes 1 and 3, the platinum atoms coordinate three carbon atoms (С1–С3) of
methyl groups, two oxygen atoms (O21–O22) of the β-diketonate ligand, and the nitrogen atom
(N11) of the pyridine ligand (Fig. 1).
Methyl ligands lie on one face of the coordination polyhedron (fac-isomer). The molecules of
both complexes are chiral due to the asymmetry of the β-diketonate ligand (various terminal
substituents). However, both enantiomers with ratio 1:1 are present in the structure of 1 and 3.

The chelate Pt–O bonding distances (Table 2) vary from typical values [18-22] within 0.01 Å.
The main differences are observed for the equatorial pairs of Pt–CH distances (2.027(4)–
3
2
.016(5) Å for 1 and 2.027(3)–2.031(3) Å for 3) due to the asymmetry of the β-diketonate
t
ligand. The substituents (- Bu and -CMe OMe) in the structure of complex 1 are in eclipsed
2
conformations. The packing of molecules in 1 is strongly conditioned by hydrogen bonds
between the oxygen atom of the methoxy group and Py hydrogen atoms of the neighboring
molecules. These H…OMe contacts organize the molecules into zigzag chains directed along the
b-axis (Fig.2).
A number of intermolecular Van der Waals contacts in crystal structure of 3 provides the
formation of channels along the a direction filled with solvate molecules (Fig.3).
The walls of these channels are formed by Py and chelate rings of the ligands. The framework
structure is essentially stabilized by a π-π stacking interaction between the chelate rings of
diketonate ligands and the C H S-substituent (3.50 Å) and by T-stacking between the hydrogen
4
3
atoms of the C H S-substituent and the Py π-system (a distance from H27 to the Py plane is 2.86
4
3
Å). In addition, there is a system of contacts between hydrogen atoms of thiophene substituents
or methyl ligands with fluorine atoms of CF substituents. Note that the π-π stacking between Py
3
ligands, previously detected for some (CH ) Pt(L)Py complexes [21, 22], is not observed in
3
3
either 1 or 3.
Hence, the comparison of (CH ) Pt(thd)Py [20] with 1 and (CH ) Pt(tfac)Py [21], 4 [22] with
3
3
3 3
3
indicates that the introduction of C(CH ) OCH or C H S-substituents into L significantly
3 2 3 4 3
alters the intermolecular contacts and results in the specific packing of molecules in the
complexes.
3
.2 Thermal behavior of (CH ) Pt(L)Py in the condensed phase
3 3
To estimate the applicability of complexes 1-4 as MOCVD precursors, their thermal
characteristics in the condensed phase were studied by TG-DTA. The obtained TG-DTA data on

complexes 1-4 were compared with those for the related (CH ) Pt(L)Py complexes [23] (Fig. 4).
3
3
Among the complexes studied, only 4 vaporized almost without decomposition (mass loss
3%), while complex 1 vaporized with partial decomposition (mass loss 73%). Hence, the
9
introduction of the C(CH ) (OCH ) group into L has a negative effect on the thermal stability of
3
2
3
(
CH ) Pt(L)Py. Indeed, for 1, complete decomposition to Pt powder in helium corresponds to a
3 3
mass loss of 62 %. In the case of 2 and 3, there are two stepwise processes, namely,
decomposition of complexes with Py releasing (mass loss 15 and 14 %) and evaporation of the
residue (total mass loss 93-95%). Clear endothermic effects at 82 and 95°C in DTA curves are
associated with the melting of 1 and 4, respectively.
There are two parallel processes: evaporation or decomposition (probably starting with Py
removal) that can occur on heating (CH ) Pt(L)Py complexes. In our previous report the degree
3
3
of (CH ) Pt(L)Py decomposition increased in the following order: hfac < tfac <ptac (4)< thd <
3
3
acac due to a decrease in the Lewis acidity of the Pt(IV) center that weakens its bonding with Py
23]. The tendency of Py loss is noticed firstly for complexes 2 and 3 from TG-DTA.
[
Interestingly, both complexes evaporate almost without decomposition after the Py loss. While
the fluorine-free complexes could form dimers [(CH ) PtL] , an example of the formation of
3
3
2
similar dimers has been unknown for the fluorine-containing analogues. Moreover, the dimer
formation is forbidden for (CH ) Pt(hfac)Py and (CH ) Pt(tfac)Py due to intramolecular F–H–Cγ
3
3
3 3
contacts [21]. These contacts do not form if one of the CF groups is replaced by either C H S or
3
4
3
t
the Bu substituent (complexes 3 and 4, respectively), thus enabling the formation of an
oligomeric structure [(CH ) PtL] at the Py loss. One the other hand, the absence of
3
3
n
intermolecular interactions between π-systems of Py ligands in the crystal may lead to a decrease
in the thermal stability of 1, 3 as well as (CH ) Pt(acac)Py complexes [20].
3
3
The experimental measurements of the p-T dependence and the thermodynamic parameters of
sublimation processes for complexes 1 and 4 are listed in Table 3.

-2
In the series of (CH ) Pt(L)Py (Fig. 5) the saturated vapor pressure at 345 K reached: 6.5·10
3
3
-3
-3
-4
Тоrr (L = hfac), 2.5·10 Тоrr (L = tfac), 2·10 Тоrr (L = ptac, complex 4), 8·10 Тоrr (L = thd),
-4
-4
1
5
·10 Тоrr (L = acac), and 2·10 Тоrr (L = L , complex 1).
This data are in a good agreement with the TG-DTA data, both following the same order of
2
1
volatility: hfac > tfac > ptac ~ ttfa ~ L > thd > acac > L . The introduction of one СF group into
3
2
1
L (L = ptac vs. thd, L vs. L ) led to a ~2.5-fold increase in the volatility of (CH ) Pt(L)Py, while
3
3
t
1
the replacement of one Bu group by -C(CH ) OCH (L = thd vs. L ) decreased four times the
3
2
3
volatility of the complexes.
3
.3 Thermal behavior of (CH ) Pt(L)Py in the gas phase
3 3
To evaluate the evaporation stability and thermolysis onset temperature of the compounds we
performed MS experiments by tracking changes of gas phase composition during the
programmed heating of 1, 2 and 4 vapors in a miniature hot wall low pressure MOCVD reactor
built in the time-of-flight mass analyzer. All the compounds have good evaporation stability,
which was confirmed by the reproducibility of mass spectra after a few cycles of heating and
cooling of the samples in the evaporator and by the absence of considerable changes in the
sample appearance after the experiments. For comparison, water-containing complexes
(
CH ) Pt(L)H O indicated relatively poor evaporation stability since after the similar MS
3 3 2
experiments a black precipitate was found in the evaporator [18]. During continuous monitoring
of the gas phase composition on heating in the reactor, the temperature dependences of ion peak
+
intensities were obtained. Fig.6 shows curves for the most intense fragmentary [(CH ) Pt] ion
3
3
for each complex studied.
The onset temperature of heterogeneous decomposition in the presence of oxygen is about
o
o
1
1
50 C and 160 C for 2 and 4, respectively, while for the fluorine-free complexes it is 130-
o
40 C for 1 and (CH ) Pt(acac)Py [23]. In the absence of oxygen, the trend is the same:
3
3
fluorinated precursor vapors are more stable. The maximum degree of decomposition appeared

in the mass spectrum by intensity of the initial compound peaks close to background value,
o
which is reached at T> 190 and 210 C for 1 and 2, 4, respectively. From the obtained
temperature dependences of the gas phase composition it follows that in-vacuum thermolysis of
the compounds proceeds through the removal of Py and then L. In the presence of oxygen, the
organic part of the compound is readily oxidized, yielding carbon oxides and water as the main
gaseous products.
In addition, DFT calculations of the molecular structures in the gas phase and the energies of
Pt–N bonds (EPt-N) were performed for complexes 1–4 and a series of similar (CH ) Pt(L)Py
3 3
complexes (L = acac, thd, tfac, hfac). For each complex, we have found two conformers (Conf1
and Conf2) that differ in the pyridine ring orientation (Fig. 7). In all cases, Conf1 is slightly more
stable than Conf2 (about 5 – 9 kJ/mol).
Table 4 lists the optimized Pt-N distances and bond energies for all optimized structures.
One may see that the bonding energies do not correlate with the lengths of Pt–N bonds, however,
there is a certain trend that the Pt-Py bonding energy increases when terminal CF groups are
3
introduced into L. Indeed, the introduction of each CF group increases the EPt-N by ~5-6 kJ/mol,
3
while the other substituents produce a minimum effect on bonding energy values. This agrees
1
3
with the C NMR data for complexes 1-3, where the signals of pyridine C2 and C6 atoms
nearest to the Pt atom) of non-fluorinated complex 1 (124.9 ppm) are slightly shifted upfield in
comparison with fluorinated complexes 2 and 3 (125.4 ppm).
(
4
. Conclusion
A new synthesis technique based on the ligand exchange reaction between (CH ) PtI and
3
3
-
1
2
PbL (L = R C(O)CHC(O)CR ligand) has been used to produce the series of (CH ) Pt(L)Py
2
3 3
1
2
1
t
2
complexes with various combinations of R , R substituents: (1) with R = Bu, R =
1
2
1
2
1
(
CH ) (OCH )), (2) (R = CF , R = (CH ) (OCH )), (3) (R = CF , R = C H S), (4) (R = CF ,
3
2
3
3
3 2
3
3
4
3
3
2
t
R = Bu) in a high yield. The synthesis procedure does not require such precautions as the
Schlenk technique, using of dry solvents is sufficient. The purity and monomeric structure of the

complexes was confirmed by the elemental analysis, IR and NMR spectroscopy, and mass
spectrometry. The compound structure – thermal properties correlations in the series of
(
CH ) PtLPy complexes were proposed. The introduction of C(CH ) OCH or C H S
3 3 3 2 3 4 3
substituents into the ligand leads to the specific packing of molecules of the complexes, resulting
in the lowering of the stability of complexes on heating in the condense phase. The measurement
of the temperature dependence of the (CH ) Pt(L)Py vapor pressure allowed us to examine their
3
3
volatility with respect to the ligand structure. The calculated energies of the weakest Pt–Py bonds
in the (CH ) Pt(L)Py complexes indicated the increasing stability of complex vapors when -CF
3
3
3
groups were introduced into the ligand. Based on the MS study, the type of the substituent in the
ligand does not affect the thermolysis mechanism of (CH ) PtLPy vapor, which proceeded
3
3
through the removal of Py and then L.
Summarizing the results of the characterization of the series of Pt(IV) complexes, we
conclude on the positive effects of the CF group in L on both volatility and evaporation stability
3
of (CH ) PtLPy complexes which are feasible for CVD/ALD processing of Pt based film
3
3
o
materials at substrate temperatures less than 210 C. The obtained results allow to expand the
range of platinum precursors limited by bis(acethylacetonato)platinum and
trimethylplatinum(IV) cyclopentadienyls. The (CH ) PtLPy precursor properties and simple
3
3
synthesis procedure make fluorinated (CH ) Pt(L)Py complexes good alternative to
3
3
trimethylplatinum(IV) cyclopentadienyl analogues and their utilization opens perspective to
fabrication new type platinum based materials.
5
. Acknowledgements
The work on synthesis and identification of (CH ) Pt(L)Py complexes was supported by the
3
3
Russian Science Foundation project №. 18-73-00052 "MOCVD of formation of platinum-
containing coatings on elements of medical devices"

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[

Table 1. Crystal data and structural refinement for 1 and 3 ([(CH ) Pt ttfaPy]·n-C H ).
3
3
6
14
Identification code
Empirical formula
Formula weight, g/mol
Temperature, K
Crystal system
Space group
a, Å
1
3
C H NO Pt
C H F NO PtS
19 25 3 2
1
9
33
3
518.55
150(2)
583.55
150(2)
monoclinic
monoclinic
P2 /n
P2 /n
1
1
9.3199(11)
16.1798(19) / 90.090(4)
14.1544(13)
2134.4(4)
10.5676(3)
17.1804(5) / 90.7430(10)
12.0353(4)
b, Å / β, °
c/Å
Volume, Å3
2184.89(11)
4
Z
4
3
ρ , g/cm
calc
1.614
1.774
μ, mm–1
6.588
6.555
F(000)
1024.0
1132.0
Crystal size, mm3
0.13 × 0.07 × 0.05
MoKα (λ = 0.71073)
3.8…54.7
0.17 × 0.15 × 0.06
MoKα (λ = 0.71073)
4.1…59.2
Radiation
2
θ range for data collection, °
Index ranges for h / k / l
Reflections collected
Independent reflections
R / R
–11…11 / –20…15 / –18…12 –14…12 / –21…23 / –15…16
11259
4756
15356
6134
0.0239 / 0.0356
4756 / 16 / 214
1.021
0.0296 / 0.0431
6134 / 0 / 248
1.015
int
σ
Data / restraints / parameters
Goodness-of-fit on F2
Final R / wR indexes for I≥2σ (I)
for all data
Largest diff. peak / hole, e·Å–3
0.0290 / 0.0555
0.0419 / 0.0589
1.03 / –0.87
0.0298 / 0.0585
0.0484 / 0.0638
1.26 / –1.05
1
2

Table 2. The main bond distances and chelate angles of 1 and 3
1
(
CH ) Pt(L )Py
1
(CH ) Pt(ttfa)Py
3
3
3
3 3
Bond
Å
Bond
Å
Pt1-O21
Pt1-O22
Pt1-N11
Pt1-C1
Pt1-C2
Pt1-C3
O21-C22
O22-C24
C22-C23
C23-C24
2.124(3)
2.121(3)
2.155(3)
2.026(4)
2.027(4)
2.017(4)
1.264(5)
1.266(5)
1.396(5)
1.394(6)
°
Pt1-O21
2.146(2)
2.151(2)
2.170(3)
2.028(4)
2.027(3)
2.031(3)
1.270(4)
1.270(4)
1.356(4)
1.426(4)
°
Pt1-O22
Pt1-N11
Pt1-C1
Pt1-C2
Pt1-C3
O21-C22
O22-C24
C22-C23
C23-C24
Angle
Angle
O21-Pt1-N11
O22-Pt1-O21
O22-Pt1-N11
C1-Pt1-O21
C1-Pt1-O22
C1-Pt1-C2
C2-Pt1-O21
C2-Pt1-N11
C3-Pt1-O22
C3-Pt1-N11
C3-Pt1-C1
86.50(13)
90.30(11)
86.72(12)
91.81(17)
91.21(16)
89.24(19)
90.81(16)
92.86(16)
89.26(16)
92.73(17)
88.9(2)
O21-Pt1-N11
O22-Pt1-O21
O22-Pt1-N11
C1-Pt1-O21
C1-Pt1-O22
C1-Pt1-C2
C2-Pt1-O21
C2-Pt1-N11
C3-Pt1-O22
C3-Pt1-N11
C3-Pt1-C1
87.24(10)
89.69(8)
86.21(10)
91.00(13)
91.80(13)
88.87(16)
90.45(13)
93.12(14)
91.66(13)
91.63(14)
90.18(16)
88.18(15)
C3-Pt1-C2
89.6(2)
C3-Pt1-C2

Table 3. Thermodynamic parameters of sublimation process for (CH ) Pt(L)Py complexes
3
3
Compound
logP(Torr) = A – B/T(К)
HT*
kJ/mol
So
J/mol*K
T*
ΔT, K
A
B
1
4
17.3
17.7
6908
6793
132.1±1.8
129.9±2.5
272.5±5.3
284.2±7.7
326–353
309–343

Table 4. Optimized Pt–N distances (Å) and bond energies (kJ/mol) of (CH ) Pt(L)Py complexes
3
3
Conf1
EPt-N, kJ/mol
Conf2
Pt–N, Å EPt-N, kJ/mol
L
R1
R2
Pt–N, Å
2.216
2.222
2.220
2.220
2.213
2.216
2.218
2.226
L1
L2
ttfa
ptac
acac
thd
tBu
CF3
CF3
CF3
CH3
tBu
C(CH ) OCH
78.97
85.57
86.33
86.01
80.11
79.25
86.37
92.73
2.236
2.242
2.238
2.239
2.225
2.235
2.228
2.239
73.88
78.28
78.32
78.44
73.32
73.56
78.19
83.09
3
2
3
3
C(CH ) OCH
3 2
C H S
4
3
tBu
CH3
tBu
tfac
hfac
CF3
CF3
CH3
CF3

Scheme 1. Reaction scheme for the synthesis of (CH ) PtLPy complexes
3
3
Figure 1. The structures of 1(a) and 3(b) molecules showing 50% probability ellipsoids.
Figure 2. The crystal packing of 1 molecules. One chain is shown in van der Waals radii.
Figure 3. The crystal packing of 3 molecules (solvate molecules are marked as dark pink, the
sites of intermolecular π-π contacts are marked by yellow spheres)
Figure 4. TG curves of (CH ) Pt(L)Py complexes
3
3
Figure 5. p-T dependences of (CH ) Pt(L)Py complexes
3
3
+
Figure 6. Temperature dependence of intensity of [(CH ) Pt] – fragmentary peak from
3
3
(
CH ) PtLPy for compounds 1, 2 and 4.
3 3
Figure 7. The two typical conformers of (CH ) PtLPy complexes illustrated on the example of
3
3
(
CH ) Pt(acac)Py
3 3