C,N-chelated diaminocarbene platinum(II) complexes derived from 3,4-diaryl-1H-pyrrol-2,5-diimines and cis-dichlorobis(isonitrile)platinum(II): Synthesis, cytotoxicity, and catalytic activity in hydrosilylation reactions

Article abstract of DOI:10.1016/j.jorganchem.2020.121435

The reaction of 3,4-diaryl-1H-pyrrol-2,5-diimines with cis-dichlorobis(isonitrile)platinum(II) affords the C,N-chelated diaminocarbene platinum(II) complexes, which have been fully characterized including molecular spectroscopy, single crystal X-ray diffr

Full text of DOI:10.1016/j.jorganchem.2020.121435

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C,N-chelated diaminocarbene platinum(II) complexes derived from 3,4-diaryl-1H-
pyrrol-2,5-diimines and cis-dichlorobis(isonitrile)platinum(II): Synthesis, cytotoxicity,
and catalytic activity in hydrosilylation reactions
Anastasiia M. Afanasenko, Tatiana G. Chulkova, Irina A. Boyarskaya, Regina M.
Islamova, Anton A. Legin, Bernhard K. Keppler, Stanislav I. Selivanov, Anatoly N.
Vereshchagin, Michail N. Elinson, Matti Haukka
PII:
S0022-328X(20)30337-5
DOI:
https://doi.org/10.1016/j.jorganchem.2020.121435
JOM 121435
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 11 April 2020
Revised Date: 4 July 2020
Accepted Date: 10 July 2020
Please cite this article as: A.M. Afanasenko, T.G. Chulkova, I.A. Boyarskaya, R.M. Islamova,
A.A. Legin, B.K. Keppler, S.I. Selivanov, A.N. Vereshchagin, M.N. Elinson, M. Haukka, C,N-
chelated diaminocarbene platinum(II) complexes derived from 3,4-diaryl-1H-pyrrol-2,5-diimines
and cis-dichlorobis(isonitrile)platinum(II): Synthesis, cytotoxicity, and catalytic activity in
hydrosilylation reactions, Journal of Organometallic Chemistry (2020), doi: https://doi.org/10.1016/
j.jorganchem.2020.121435.
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C,N-Chelated diaminocarbene platinum(II) complexes derived from 3,4-diaryl-1H-
pyrrol-2,5-diimines and cis-dichlorobis(isonitrile)platinum(II): synthesis, cytotoxicity,
and catalytic activity in hydrosilylation reactions
a
b,
b
Anastasiia M. Afanasenko, Tatiana G. Chulkova, * Irina A. Boyarskaya, Regina M.
b
c
c
b
Islamova, Anton A. Legin, Bernhard K. Keppler, Stanislav I. Selivanov, Anatoly N.
d
d
f
Vereshchagin, Michail N. Elinson, Matti Haukka
a
Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG
Groningen, The Netherlands.
b
Saint Petersburg State University, Institute of Chemistry, 7/9 Universitetskaya Nab., Saint
Petersburg, 199034 Russia.
c
Institute of Inorganic Chemistry, University of Vienna, Währinger Straße 42,1090 Vienna,
Austria.
d
N. D. Zelinsky Institute of Organic Chemistry, 47 Leninsky Prospect, Moscow, 119991
Russia.
f
Department of Chemistry, University of Jyväskylä, P.O. Box 35, FI-40014 Jyväskylä,
Finland.
*
Corresponding author.
E-mail address: t.chulkova@spbu.ru (T.G. Chulkova).
Highlights
Synthesis of C,N-chelated diaminocarbene platinum(II) complexes
C,N-Chelated diaminocarbene platinum(II) complexes as catalysts for the hydrosilylation of
unsaturated compounds
Luminescence of diaminocarbene platinum(II) complexes and silicone rubbers prepared using these
complexes
Cytotoxicity of diaminocarbene platinum(II) complexes against CH1/PA-1, SW480, and A549 cancer
cell lines
Graphical Abstract
1

ABSTRACT
The reaction of 3,4-diaryl-1H-pyrrol-2,5-diimines with cis-dichlorobis(isonitrile)platinum(II) affords
the C,N-chelated diaminocarbene platinum(II) complexes, which have been fully characterized
including molecular spectroscopy, single crystal X-ray diffraction and DFT calculations. The obtained
platinum(II) complexes are effective catalysts for the hydrosilylation of alkynes and alkenes. Thus, the
reaction of phenylacetylene with triethoxysilane leads to the formation of α- and β-(E)-vinylsilanes,
3
4
2
3
-1
generating TON’s in the range of 10 to 10 and TOF’s in the range of 10 to 10 h . Also, the cross-
linked silicones, possessing the luminescence properties, were obtained by the hydrosilylation reaction
of vinyl- and hydride-containing polysiloxanes. Additionally, the efficiency of diaminocarbene
platinum(II) complexes against CH1/PA-1, SW480, and A549 cancer cell lines has been demonstrated
by in vitro cytotoxicity studies.
Keywords: Anti-cancer activity, catalysis, diaminocarbene platinum(II) complexes, hydrosilylation,
luminescence.
1
. Introduction
In recent years, metal complexes bearing acyclic diaminocarbenes ([M]ADCs) [1,2] have emerged
as a new family of homogeneous catalysts to be a prominent alternative to well-investigated metal-N-
heterocyclic carbene ([M]NHCs) [3–5] species. Notwithstanding the structural and electronic
similarity to the NHCs, the greater steric control due to the wider N-C-N bond angles of acyclic
diaminocarbene ligands [6] as well as donor ability and the rotation freedom [7,8] ensure the high
stability of the corresponding metal complexes and foster various stages of the catalytic processes [2].
Easy-to-prepare metal-ADCs complexes synthesized by nucleophilic addition of N-nucleophiles to
coordinated isocyanides [9–11] have been successfully investigated as potential catalysts for several
organic transformations (cross-coupling, metathesis, cyclization reactions, etc.) [12–15]. However, as
far as it is known, examples of catalytic activities of the ADC-platinum(II) complexes for
hydrosilylation of unsaturated compounds are quite limited to date. Recently, the first examples of the
use of diaminocarbene platinum complexes derived from the reaction between cis-[PtCl (CN-R) ] and
2
2
hydrozones [16] or 3-iminoisoindolin-1-ones [17] as catalysts for hydrosilylation of unsaturated
compounds have been reported.
In this context, as a continuation of these studies on the application of platinum systems as
homogeneous catalysts for the hydrosilylation of unsaturated organic molecules, herein we have
presented on the synthesis, characterization, in vitro antitumor activity studies, and reactivity of series
of acyclic diaminocarbene complexes of Pt(II) for the hydrosilylation of both terminal alkynes and
alkenes.
2
. Results and discussion
2
.1.Synthesis and characterization of the ADC-platinum(II) complexes (3−5)
Compounds 3a−c, 4c, 5c have been obtained in 20-50% yields by stirring for 2 hours a mixture of
,4-diaryl-1H-pyrrol-2,5-diimine (aryl = phenyl (1a), 4-methylphenyl (1b), 4-methoxypheyl (1c)) and
3
2
2
cis-[PtCl (CNR ) ] (R = cyclohexyl (2a), tert-butyl (2b), 4-methoxypheyl (2c)) in chloroform at room
2
2
temperature (Scheme 1). 3,4-Diaryl-1H-pyrrol-2,5-diimines, containing electron-withdrawing
substituents (aryl = 4-fluorophenyl (1d), 4-chlorophenyl (1e), 4-bromophenyl (1f)), react more slowly
than the compounds with electron donor groups. Thus, employing diaryl-1H-pyrrol-2,5-diimines (1d−f)
as coupling partners, the reactions proceeded under reflux conditions for 5 hours with the formation of
the corresponding platinum complexes with yields of 12-22% (3d−f). Interestingly, the obtained
products have the same structure as the ADC-palladium(II) complexes derived from 3,4-diaryl-1H-
pyrrol-2,5-diimines and bisisocyanide palladium(II) complexes [18]. During the reaction, one
isocyanide ligand in 2a−c undergoes a nucleophilic attack by the imino group of 1a−f, whereas the
second one remains intact. The imino nitrogen atom of 1 is attached to the carbon atom of the
isocyanide group, whereas the nitrogen atom of the pyrrole ring coordinates to the metal center, thus
closing the five-membered metallocycle. As a result, monocarbene platinum(II) complexes were
obtained.
2

R2
Cl
R1
R1
R2
N
NH
NH
NH
A: CHCl , RT, 2 h
N
NH
3
B: CH CN, reflux, 5 h
3
N Pt
N R2
Cl Pt
Cl
N R2
Cl
NH2
R1
R1
1
2
1
1
1
1
1
1
a: R = H
2a: R = Cy
2
1
3
: R = Cy; R = H (a), CH (b),
3
1
2
b: R = CH
2b: R = t-Bu
3
CH O (c), F (d), Cl (e), Br (f)
3
1
2
c: R = CH O
2c: R = 4-CH OC H
2
1
3
3
6
4
4
: R = t-Bu; R = CH O (c)
3
1
d: R = F
2
1
5
: R = 4-CH OC H ; R = CH O (c)
3
6
4
3
1
e: R = Cl
1
f: R = Br
Scheme 1. Syntheses of ADC-platinum(II) complexes (3a−f, 4c, 5c).
+
The obtained diaminocarbene complexes 3−5 were fully characterized by elemental analysis, ESI -MS,
IR, 1D and 2D NMR spectroscopies. The NMR spectral assignment to 3a−f, 4c, 5c was performed on
1
1
the basis of signal intensities, chemical shifts and H, H-coupling constants as well as the results of
1
13
two-dimensional NMR measurements (COSY, NOESY, H, C-chemical shift correlation spectra
1
13
1
13
(
HSQC and HMBC)). For example, the correlations found in the COSY, H, C-HMBC, and H, C-
1
13
HSQC spectra of 3b correspond with the proposed structure (Fig. 1). In the H, C-HMBC spectrum
2
5b
17
(
Fig. S9) of 3b the observed cross-peak between signals of H (δ 9.93 ppm) and C (δ 140.9 ppm)
1
7
allows to identify signals of aromatic ring B. The correctness of signal C assignment is additionally
1
9
24
17
confirmed by the presence of cross-peak between H , H (δ 7.36 ppm) and C (δ 140.9 ppm). In the
2
3
7
COSY spectrum (Fig. S10) the cross-peaks between H (δ 4.53 ppm) and the nearest protons H , H (δ
.23−2.26 ppm/1.89−1.92 ppm), having the axial and equatorial orientations, respectively, are
observed. Thus, the presence of these cross-peaks assists the identification of cyclohexyl ring C.
Similar cross-peaks between H (δ 3.57 ppm) and axial/equatorial protons H , H (δ 1.55−1.63
ppm/1.83−1.87 ppm, respectively) define the cyclohexyl ring D.
2
2
7
28
32
Fig. 1. Structure of 3b.
1
1
16
In the fragment B of NOESY spectrum (Fig. S12), the cross-peak between H , H (δ 7.45 ppm) and
3
7
4
6
equatorial protons H , H and H , H (δ 1.89−1.92 ppm/1.83−1.87 ppm, respectively) is observed. The
presence of these spatial interactions does not contradict the data of X-ray analysis about the mutual
spatial arrangement of the rings B and C. In the fragment A of NOESY spectrum (Fig. S12), a direct
2
5b
29
31
interaction between H
(δ 9.93 ppm) and equatorial protons H , H (δ 1.55−1.63 ppm) of
cyclohexyl ring D is observed; the existence of this spatial interaction proves the existence of 3b
dimers in a chloroform solution. In the fragment B of NOESY spectrum (Fig. S12), the cross-peak
1
9
24
between signals of aromatic ring protons H , H (δ 7.36 ppm) and equatorial protons of cyclohexyl
29
31
fragment H , H (δ 1.55−1.63 ppm) is identified. These aforementioned direct interactions
additionally prove the correctness of signal assignment in the aromatic and aliphatic fragments.
The structure of 3b was additionally confirmed by single crystal X-ray diffraction (Fig. 2, Table S2).
3

Fig. 2. Molecular structure of 3b∙CH Cl at the 50% probability level.
2
2
The crystals of 3b suitable for X-ray diffraction were obtained by a slow evaporation of
dichloromethane at room temperature. 3b is crystallized in the monoclinic space group C2/c. The Pt
center has distorted square planar geometry. The cyclohexyl isocyanide ligand is located opposite to
the pyrrole ring. Earlier in our group similar ADC-platinum(II) complexes have been obtained via
coupling between 3-iminoisoindolin-1-one and bisisocyanide platinum(II) species, however, the
geometry of these complexes is different: the isocyanide ligand is located opposite to the
diaminocarbene fragment [19].
We assume whether one or another isomer is obtained probably depends on the stabilization of the
compound due to the formation of hydrogen bonds. In the case of platinum(II) complex with
iminoisoindolinone fragment, the product is stabilized via the NH⋅⋅⋅Cl hydrogen bond, whereas, the
structure of 3b is stabilized by two hydrogen bonds ((N4)H⋅⋅⋅Cl1 (2.32(7) Å) and (N1)H⋅⋅⋅Cl2 (2.28(7)
Å)). Indeed, according to our theoretical calculations, the obtained isomer of 3b (Fig. 2) is 22.3 kJ/mol
more stable than its other isomer 3b’. The optimized geometry of 3b is close to the structure obtained
by XRD. Also, the (NH)H⋅⋅⋅Cl(Pt) (2.308 Å) and (NCy)H⋅⋅⋅Cl(Pt) (2.433 Å) intramolecular hydrogen
bond lengths were calculated for 3b and 3b’, respectively. These data show that the (NH)H⋅⋅⋅Cl(Pt)
intramolecular hydrogen bond in 3b is stronger than the (NCy)H⋅⋅⋅Cl(Pt) bond in its isomer 3b’.
2
.2.Photophysical properties
The absorption and fluorescence properties of the synthesized compounds 3a–d, 4c, and 5c were
−
5
evaluated by UV−vis absorption and emission spectroscopies at a concentration of 2.5·10 M in
chloroform (Table 1). Compounds 3a–d, 4c, and 5c show the maximum absorbance at larger
wavelengths (λabs at 318−398 nm) (Table 1, Fig. S13) compared to those of 1a−d (λabs at 278−311 nm)
[
20]. The red-shift of the absorption maximum band can be explained by the formation of an extended
π conjugated system in the resulting metal complex structure. The presence of the donor substituents at
the phenyl rings of the 1H-pyrrol-2,5-diimine fragment leads to the red-shift of the absorption band
like in 1a−d.
Complexes 3a–d, 4c, and 5c exhibit fluorescence in the visible range of 493–572 nm (Table 1, Figs.
S14−15). As in the case of the absorption spectra, donor substituents at the phenyl rings of the
4

pyrroldiimine fragment generally cause red shift of the fluorescence emission bands. The fluorescence
spectra of 3a–d, 4c, and 5c have large Stokes shifts varied in the range of 174–185 nm. The measured
fluorescence lifetimes for 3a–d, 4c, and 5c are in the range of 10–13 ns (Table S1). Similarly to the
previously reported Pd analogues [18], all investigated diaminocarbene platinum complexes possess
low luminescence (the fluorescence quantum yields for 3a–d, 4c, and 5c vary in a range of 1-11%
(
Table S1)).
Table 1
-
5
Absorption and emission properties of 3a–d, 4c, and 5c in chloroform solution (2.5∙10 M).
Compound λ , nm (ε⋅10 , M cm )
-4
-1
-1
λ , nm
em
Stokes shift, nm
abs
3
3
3
3
4
5
*
a
b
c
d
c
318 (1.1)
493
505
571
530
572
567
175
176
181
177
174
185
268*, 329 (0.9)
268*, 390 (1.2)
353 (1.0)
268*, 398 (0.6)
270*, 382 (0.7)
c
the band appears as a shoulder, the position of the maximum is approximately determined
2
.3.In vitro cytotoxic activity
To date, a large number of studies on the cytotoxicity of NHC complexes with various metals have
been carried out [21,22]. Despite extensive studies on ADC complexes in organometallic chemistry
and catalysis, only a restricted array of anticancer applications have been reported so far for platinum,
palladium, and gold derivatives [23–25]. To assess the anticancer potential of the obtained acyclic
diaminocarbene platinum(II) complexes (3b, 4c, and 5c) their cytotoxic properties have been
evaluated in vitro on ovarian teratocarcinoma (CH1/PA-1), colon carcinoma (SW480) cell lines and
adenocarcinomic human alveolar basal epithelial cells (A549) (Fig. S18). The inhibitory potency of
the metal complexes on proliferation and viability of these cancer cells was characterized by using the
spectrophotometric MTT assay, the obtained data is summarized in Table 2.
Table 2
In vitro cytotoxic activity of platinum complexes in CH1/PA-1, SW480, and A549 cell lines (IC , µM,
5
0
9
6 h exposure).
3
b
4c
5c
Cisplatin[26]
0.14 ± 0.03
3.3 ± 0.4
CH1/PA-1
SW480
A549
13 ± 0.2
12 ± 1
26 ± 1
47 ± 2
37 ± 7
>80
15 ± 3
13 ± 2
33 ± 2
1.3 ± 0.4
Cytotoxicity of all complexes is in a low to average micromolar range. The complexes were shown to
effectively decrease the number of treated cancer cells. However, their efficiency is lower than shown
for established cytotoxic anticancer drug cisplatin in respective cell lines.
2
.4.ADC-Pt(II) catalysed hydrosilylation of phenylacetylene with triethoxysilane
1
H NMR studies of the reaction of phenylacetylene with triethoxysilane at 100°C in the presence of
catalytic amounts of the ADC-Pt(II) complexes evidenced that the studied catalysts promote the
hydrosilylation of phenylacetylene to (E)-triethoxy(styryl)silane (β-(E)-product) as a major product
and triethoxy(1-phenylvinyl)silane (α-product) as a minor product (Scheme 2). The formation of (Z)-
triethoxy(styryl)silane (β-(Z)-isomer) was not observed.
5

Scheme 2. Hydrosilylation of phenylacetylene.
In preliminary optimization of the reaction conditions, we revealed the influence of reaction time on
the yield and product ratio (Table 3).
Table 3
a, b
Optimization of the reaction conditions: effect of the reaction time.
Entry
α/β-(E)
product
ratio, %
-
Overall
yield, %
-
1
Time, h
TON
TOF,
-
h
1
2
0.5
1
0
-
2
2
2
2
2
61
21/79
23/77
26/74
27/73
1
1
1
1
2.2×10
4.6×10
6.0×10
7.4×10
4.1×10
4.9×10
5.3×10
5.8×10
2
2
2
3
4
5
2
73
80
87
2.5
3
a
-2
PhC≡CH (0.5 mmol, 1 equiv.), (EtO) SiH (0.5 mmol, 1 equiv.), catalyst 3c (5×10 mol%), toluene
0.2 mL). Yields were determined by H NMR spectroscopy using 1,2-dimethoxyethane as a
3
b
1
(
standard; the isomeric content was determined on the basis of the alkene coupling constants (see the
Supporting Information, p. S13).
While no alkenes were obtained for 0.5 h (Table 3, entry 1), which could be attributed to the induction
period of the catalyst [27], relatively good conversion of 61% for 1 h (Table 3, entry 2) and excellent -
8
7% for 3 h (Table 3, entry 5) were detected. Selecting appropriate reaction time (3 h), solvent
(
toluene) and reaction temperature (100 °C) for further study, the effect of catalyst loading was
evaluated (Table 4). Notably, with 0.1 mol% and 0.05 mol% loading of catalyst, excellent yields of
the corresponding alkenes were observed (93% and 87%, respectively). Importantly, the maximum
3
catalyst turnover number (TON) of 7.8×10 was achieved with 0.005 mol% loading of catalyst 3c
during 3 hours at 100 °C (Table 4, entry 3), however, the yield of the desired alkene products was
dropped to 39%.
Table 4
a, b
Optimization of the reaction conditions: effect of the catalyst loading.
Entry
Catalyst 3c
loading,
mol%
α/β-(E)
product
ratio, %
Overall
yield, %
-
1
Time, h
TON
TOF, h
2
2
1
2
3
0
.1
3
3
3
93
87
39
22/78
27/73
17/83
9
.3×10
3.1×10
5.8×10
2.6×10
-
2
3
2
2
3
5
5
×10
×10
17.4×10
-
3
7.8×10
a
b
PhC≡CH (0.5 mmol, 1 equiv.), (EtO) SiH (0.5 mmol, 1 equiv.), toluene (0.2 mL). Yields were
determined by H NMR spectroscopy using 1,2-dimethoxyethane as a standard; the isomeric content
was determined on the basis of the alkene coupling constants.
3
1
6

With the optimized reaction conditions at hand, the comparison of the catalytic activity of the acyclic
diaminocarbene platinum(II) complexes 3a−d, 4c, 5c as a function of the substituents in
diaminocarbene (Table 5) and 1H-pyrrol-2,5-diimine (Table 6) moieties was estimated in the model
system. To our delight, all acyclic diaminocarbene complexes of Pt(II) could be potentially used as
catalysts for the hydrosilylation reaction of terminal alkynes. Among the examined complexes, the
most active species (3b, 3c, 4c, 5c) were derived from the addition of 3,4-diaryl-1H-pyrrol-2,5-
1
diimines with donor substituents (R = CH O, CH ) to isocyanide complexes of platinum(II), with
3
3
2
bulky donor ligands (R = t-Bu, Cy, p-(CH O)C H ), whereas 3a and 3d possess lower activity. The
3
6
4
observed phenomenon could be attributed to the strong electron donation from the aminocarbenes,
derived from the aliphatic isocyanides and 1H-pyrrol-2,5-diimines, comprising donor substituents, to
2
the metal center, facilitating the oxidative addition of silane substrates. The nature of the substituent R
has practically no effect on the yield of reaction products.
Notably, the isomeric ratio of alkene products is essentially independent of the nature of the
substituents in the catalyst, namely, α- and β-(E)-products were observed in 1: 3 ratio.
Table 5
a, b
Effect of the substituents in diaminocarbene fragment.
Entry
α/β-(E)
product
ratio, %
27/73
Overall
yield, %
-
1
Catalyst
TON
TOF, h
2
2
2
2
1
2
3
3c
4c
5c
87
87
81
1
1
1
7.4×10
7.4×10
6.2×10
5.8×10
5.8×10
2
2
27/73
20/80
5.4×10
a
-2
PhC≡CH (0.5 mmol, 1 equiv.), (EtO) SiH (0.5 mmol, 1 equiv.), catalyst 3c, 4c, 5c (5
toluene (0.2 mL). Yields were determined by H NMR spectroscopy using 1,2-dimethoxyethane as
standard; the isomeric content was determined on the basis of the alkene coupling constants.
×
10 mol%),
3
b
1
Table 6
a, b
Effect of the substituents in 1H-pyrrol-2,5-diimine fragment.
Entry
α/β-(E)
product
ratio, %
23/77
Overall
yield, %
-
1
Catalyst
TON
TOF, h
2
2
2
2
2
1
2
3
4
3a
3b
3c
3d
79
90
87
74
1
1
1
1
5.8×10
8.0×10
7.4×10
4.8×10
5.3×10
6.0×10
5.8×10
2
2
2
21/79
27/73
23/77
4.9×10
a
-2
PhC≡CH (0.5 mmol, 1 equiv.), (EtO) SiH (0.5 mmol, 1 equiv.), catalyst 3a−d (5
toluene (0.2 mL). Yields were determined by H NMR spectroscopy using 1,2-dimethoxyethane as
standard; the isomeric content was determined on the basis of the alkene coupling constants.
×
10 mol%),
3
b
1
2
.5.ADC-Pt(II) catalysed curing of polysiloxanes
ADC-Pt(II) catalysed hydrosilylative cross-linking was studied on model α,ω-
di(vinyldimethylsiloxy)poly(dimethylsiloxane) (PDMS)/ trimethylsilyl-terminated
poly(dimethylsiloxane-co-ethylhydrosiloxane) (EHDMS) mixtures with catalysts 3b, 3d, and 5c
−
3
−5
(
10 −5⋅10 M) (Scheme 3).
7

Scheme 3. ADC-Pt(II) catalysed cross-linking of PDMS and EHDMS.
The catalytic activity was evaluated at 85°C owing to the identification of the curing time (τcuring
)
(
Table S3).
Investigating the dependence of curing time (τcuring) on the concentration of the platinum catalysts, we
observed the gradual decline of the reaction time with increasing catalyst concentration, for instance,
–
5
–3
for the curing using 3b at 5
×10 M takes 15 h (Table S3, entry 4) vs 8 h at 1×10 M (Table S3, entry
1
). Remarkably, we observed a clear correlation between the catalytic activity of the studied
complexes and their structure. Catalyst 5c exhibits the highest catalytic activity, which is probably due
to the presence of electron-donating methoxy-groups in its structure. Since it is known that the
increasing donor character of a ligand increases the electron density at the metal center and favors the
oxidative addition stage of the catalytic cycle. In contrast, complex 3d demonstrates lower catalytic
activity due to the large –I-effect of fluorine.
The obtained silicone formulations incorporate no structural defects, i.e. no bubbles and the surface of
the silicone rubbers is uniform.
Further, we evaluated the luminescence properties of the silicone rubbers prepared employing catalysts
3
a−d and 5c (Table 7).
Table 7. Luminescence properties of the silicone rubbers prepared using catalysts 3a−d and 5c
Catalyst
λex, nm
353
377
375
369
λ , nm
Stokes shift, nm
em
3
3
3
3
5
a
b
c
d
c
477
463
526
488
507
124
86
151
119
123
384
It is worth noting that the emission maxima for the silicone rubbers obtained using catalysts 3a−d and
c (Table 7 and Figure S16) are blueshifted compared with chloroform solutions of complexes 3a−d
5
and 5c (Table 1), respectively. The overall emission intensity for the cured silicone rubbers has
substantially decreased when compared to that of complexes 3a−d and 5c in solution. The quantum
yield cannot be carefully estimated for rubbers because of the complexity of calculations and polymer
self-absorption.
3
. Conclusion
In conclusion, we have successfully synthesized new ADC-Pt(II) complexes via the reaction of
bisisocyanide platinum(II) complexes and 3,4-diaryl-1H-pyrrol-2,5-diimines and applied them as
catalysts for the hydrosilylation of phenylacetylene. Employing optimized reaction conditions (toluene,
1
00 °C, 3 hours, 0.05 mol% catalyst loading), the target vinylsilanes were obtained in good to
excellent yields. It is crucial to mention that a limited number of the previously described
hydrosilylation reactions catalyzed by the Pt-(NHC) [27–30] and Pt-(ADC) [16,17] complexes require
a higher catalyst loading (0.1−1 mol%) or a longer reaction time (up to 48 hours). Also, the prepared
ADC-Pt(II) complexes can be used as catalysts for the cross-linking of polysiloxanes leading to
luminescent silicone rubbers.
8

Furthermore, we have revealed that the designed diaminocarbene platinum(II) complexes exhibit
photoluminescent properties strongly depending on the substituents in pyrroldiimine moiety and
demonstrate the promising potential as anticancer drugs.
4
. Experimental
4
.1.General considerations
All solvents were dried and purified by conventional methods and were freshly distilled under argon
shortly before use. Other reagents were used without further purification. The starting materials 3,4-
diaryl-1H-pyrrol-2,5-diimine (aryl = phenyl (1a), 4-methylphenyl (1b), 4-methoxypheyl (1c), 4-
2
2
fluorophenyl (1d), 4-chlorophenyl (1e), 4-bromophenyl (1f))[20,31,32] and cis-[PtCl (CNR ) ] (R =
2
2
Cy (2a), t-Bu (2b), 4-(CH O)C H (2c)) [27,28] were prepared as previously reported.
3
6
4
PDMS (the weight average molecular weight M = 80000, the number average molecular
w
weight M = 33800, 0.5 wt% of CH=CH ) and EHDMS (M = 8150, M = 4600, M /M = 1.8,
n
2
w
n
w
n
Si–H 0.7 wt%) were obtained according to the procedure [35].
–
1
FTIR spectra were recorded on Shimadzu FTIR-8400S (4000–400 cm ) and IRAffinity-1S (4000–300
–
1
1
13
1
1
13
cm ) spectrometers using KBr pellets. One-dimensional ( H, C{ H}) and two-dimensional ( H− C
1
13
HMBC, H− C HSQC, NOESY, COSY) NMR spectra were recorded on a Bruker-DPX 400
instrument at ambient temperature. Electrospray ionization mass spectra were obtained on a Bruker
micrOTOF spectrometer equipped with electrospray ionization (ESI) source using MeOH as the
solvent. The instrument was operated in both positive and negative ion modes using a m/z range of
+
5
0–3000. The capillary voltage of the ion source was set at -4500 V (ESI –MS) and the capillary exit
at ±(70–150) V. The nebulizer gas flow was 0.4 bar and drying gas flow 4.0 L/min. Elemental
analyses were measured on a Euro EA3028-НТ Element Analyzer system. The absorption spectra
were recorded on a Perkin–Elmer precision spectrophotometer Lambda 1050. The emission spectra,
excitation spectra, and measurements of the lifetimes of excited states were measured on a modular
spectrofluorimeter Fluorolog-3 (Horiba Jobin Yvon). Fluorescence lifetime measurements are based
on time-correlated single photon counting (TCSPC). Device also includes an integrating sphere
Quanta-φ with fiber optics which enables direct measurement of quantum yields of luminescence.
4
.2.Synthesis of Pt(II) complexes
Synthesis of complexes 3a−c, 4c, and 5c: A 50 mL flat-bottomed flask, equipped with a stirring
bar, was charged with 3,4-diaryl-1H-pyrrol-2,5-diimine (aryl = phenyl (1a), 4-methylphenyl (1b), 4-
2
2
methoxypheyl (1c),) (0.1 mmol), cis-[PtCl (CNR ) ] (R = Cy (2a), t-Bu (2b), 4-(CH O)C H (2c))
2
2
3
6
4
(
0.1 mmol), and 10 mL of anhydrous chloroform. The reaction mixture was stirred at room
temperature for 2 hours: the color of the reaction mixture was immediately changed to cherry-red.
After removal of the solvent under vacuum, the residue was washed with 10 mL of acetone. The
resulting solid was recrystallized from the mixture of dichloromethane and hexane (2:1) at room
temperature.
1
3
a: Yield 46%, orange crystals. H NMR (400 MHz, DMSO-d /CDCl ): δ 10.71 (br, 1H, NH), 9.74
6
3
(
br, 1H, NH), 7.54−7.34 (m, 10H, H−Ar), 4.45−4.39 (m, 2H, CH), 1.94−1.12 (m, 20H, –HC(CH ) ).
2 5
1
3
C NMR (101 MHz, DMSO-d ): δ 182.1, 174.2, 172.1, 140.3, 137.1, 137.0, 130.8, 130.5, 130.3,
6
1
30.2, 130.1, 129.7, 129.2, 128.9, 128.8, 128.6, 55.7, 54.9, 31.7, 31.4, 25.1, 24.9, 22.3. IR (KBr,
-1
selected bands, cm ): 3407 w ν(N-H), 2935 s, 2856 s ν(С -H), 2234 s ν(C≡N), 1687 m, 1618 m
ν(С=N), 1559 s ν(N−Сcarbene). HRMS (ESI ), m/z: 695.2235 [M−Cl] . C H ClN Pt Calcd. m/z:
sp3
+
+
30
35
5
6
4
3
95.2229. Anal. Calcd. for C H Cl N Pt⋅2CHCl (970.37): C, 39.61; H, 3.84; N, 7.22. Found: C,
30 35 2 5 3
0.14; H, 3.90; N, 7.34.
b: Yield 50%, orange crystals. H NMR (400 MHz, CDCl ): δ 11.22 (br, 1H, NCNH ), 9.93 (br, 1H,
1
1a
3
2
5b
25a
3
11
16
3
19
NH ), 8.34 (br, 1H, NH ), 7.45 (d, J = 8.0 Hz, 2H, H , H ), 7.36 (d, J = 8.0 Hz, 2H, H ,
H ), 7.29 (d, J = 8.0 Hz, 2H, H , H ), 7.15 (d, J = 8.0 Hz, 2H, H , H ), 4.53 (br, 1H,
CH NC), 3.57 (br, 1H, CH NC), 2.43 (s, 3H, CH in A ring), 2.39 (s, 3H, CH in B ring), 2.26−2.23
HH
23
HH
12
2
4
3
20
3
15
HH
HH
2
27
3
3
3
eq
ax
3
7
eq
7
28
32
eq
4
(
m, 2H, H at C , C ), 1.92−1.89 (m, 2H, H at C , C ), 1.87-1.83 (m, 4H, H at C , C ; H at C ,
6
ax
28
32
eq
29
31
ax
eq
5
ax
4
6
C ), 1.65-1.58 (m, 6H, H at C , C ; H at C , C ; H , H at C ), 1.31−1.23 (m, 6H, H at C , C ;
9

ax
29
31
ax
eq
30
13
1
8
25
H at C , C ; H , H at C ). C NMR (101 MHz, CDCl ): δ 183.8 (C ), 179.4 (C ), 170.8 (C ),
3
17
21
13
9
20
23
11
16
19
24
1
1
40.9 (С ), 140.8 (С ), 140.6 (С ), 138.2 (С ),130.3 (С , C ), 130.1 (С , C ), 129.7 (C , C ),
12
15
10
18
2
27
28
32
3
7
4
29.2 (C , C ), 126.5 (C ), 125.1 (C ), 58.3 (C ), 55.4 (C ), 31.7 (C , C ), 31.2 (C , C ), 25.3 (C ,
6
29
31
5
30
22
14
1
C ), 24.8 (C , C ), 22.9 (C , C ), 21.6 (C ), 21.5 (C ). The full assignment of the signals in H and
1
3
1
13
1
13
C NMR spectra was performed using H− C HMBC, H− C HSQC, NOESY, COSY NMR
techniques (Figs. 9S−12S). IR (KBr, selected bands, cm ): 3168 w ν(N–H), 2934 s, 2857 w
ν(С −H), 2235 s ν(C≡N), 1608 s ν(С=N), 1564 s ν(N−С
M−Cl] . C H ClN Pt Calcd. m/z: 723.2542. Anal. Calcd. for C H Cl N Pt⋅CH Cl (844.60): C,
-1
+
). HRMS (ESI ), m/z: 723.2539
sp3
carbene
+
[
32 39 5 32 39 2 5 2 2
4
3
9
6.93; H, 4.89; N, 8.29. Found: C, 47.13; H, 4.93; N, 8.34.
1
c: Yield 46%, red crystals. H NMR (400 MHz, CDCl ): δ 11.22 (br, 1H, NH), 11.13 (br, 1H, NH),
3
3
3
3
.90 (br, 1H, NH), 7.54 (d, J = 8.0 Hz, 2H, H−Ar), 7.43 (d, J = 8.0 Hz, 2H, H−Ar), 7.01 (d, J = 8.0
3
Hz, 2H, H−Ar), 6.86 (d, J = 8.0 Hz, 2H, H−Ar), 4.53 (br, 1H, –HC(CH ) ), 3.89 (s, 3H, OCH ), 3.86
2
5
3
1
3
(
s, 3H, OCH ), 3.63 (s, 1H, –HC(CH ) ), 2.30−1.23 (m, 20H, CH ). C NMR (101 MHz, CDCl ): δ
3 2 5 2 3
1
5
84.2, 179.6, 171.0, 161.3, 161.1, 139.5, 137.0, 131.8, 131.5, 121.9, 120.4, 115.1, 114.0, 58.2, 55.2,
-1
5.5, 55.4, 31.7, 31.2, 30.9, 25.3, 24.8, 22.8. IR (KBr, selected bands, cm ): 3433 s ν(N–H), 2924 w
+
ν(С −H), 2214 s ν(C≡N), 1609 s ν(С=N), 1514 s ν(N−С
). HRMS (ESI ), m/z: 755.2419
sp3
carbene
+
[
M−Cl] . C H ClN O Pt Calcd. m/z: 755.2440. Anal. Calcd. for C H Cl N O Pt (791.67): C,
32 39 5 2 32 39 2 5 2
4
4
8.55; H, 4.97; N, 8.85. Found: C, 48.18; H, 4.93; N, 8.75.
1
c: Yield 45%, red crystals. H NMR (400 MHz, CDCl ): δ 11.01 (br, 1H, NH), 10.63 (br, 1H,
3
3
3
NCNH), 9.95 (br, 1H, NH), 7.81 (d, J = 8.0 Hz, 2H, H−Ar), 7.30 (d, J = 8.0 Hz, 2H, H−Ar), 7.03 (d,
3
3
J = 8.0 Hz, 2H, H−Ar), 6.84 (d, J = 8.0 Hz, 2H, H−Ar), 3.90 (s, 3H, OCH ), 3.84 (s, 3H, OCH ),
3
3
-1
1
.64 (s, 9H, t-Bu), 1.55 (s, 9H, t-Bu). IR (KBr, selected bands, cm ): 3423 s ν(N–H), 2928 w, 2831 w
+
ν(С −H), 2220 m ν(C≡N), 1707 m, 1603 s ν(С=N), 1502 s ν(N−С
). HRMS (ESI ), m/z:
sp3
carbene
+
7
03.2046 [M−Cl] . C H ClN O Pt Calcd. m/z: 703.2127. Anal. Calcd. for C H Cl N O Pt⋅CH Cl
28 35 5 2 28 35 2 5 2 2 2
(
824.53): C, 42.24; H, 4.52; N, 8.49. Found: C, 42.42; H, 4.54; N, 8.54.
1
5
7
3
c: Yield 21%, red crystals. H NMR (400 MHz, CDCl ): δ 10.88 (br, 1H, NH), 9.38 (br, 1H, NH),
3
.81−7.76 (m, 4H, H−Ar), 7.54−7.50 (m, 4H, H−Ar), 6.89−6.80 (m, 8H, H−Ar), 3.89 (s, 3H, OCH ),
3
-1
.85 (s, 3H, OCH ), 3.83 (s, 3H, OCH ), 3.76 (s, 3H, OCH ). IR (KBr, selected bands, cm ): 3443 m
3
3
3
ν(N–H), 2932, 2835 w ν(С −H), 2199 m ν(C≡N) 1709 m, 1603 s ν(С=N), 1506 s ν(N−Сcarbene).
sp3
+
+
HRMS (ESI ), m/z: 803.1707 [M−Cl] . C H ClN O Pt Calcd. m/z: 803.1712. Anal. Calcd. for
3
4
31
5
4
C H Cl N O Pt (839.62): C, 48.64; H, 3.72; N, 8.34. Found: C, 48.33; H, 3.71; N, 8.27.
34
31
2
5
4
Synthesis of complexes 3d−f: A 5 mL round-bottomed flask was equipped with a stirring bar and
charged with cis-[PtCl (CNCy) ] (2a) (0.1 mmol) and 3,4-diaryl-1H-pyrrol-2,5-diimine (aryl = 4-
2
2
fluorophenyl (1d), 4-chlorophenyl (1e), 4-bromophenyl (1f)) (0.1 mmol). Anhydrous acetonitrile (4
mL) was added and the solution was stirred under reflux conditions for 5 hours. Volatiles were
evaporated under vacuum. The resulting solid was rinsed with acetone (1 mL) and recrystallized from
the mixture of acetone and chloroform (1:2).
1
3
1
4
2
d: Yield 23%, red crystals. H NMR (400 MHz, CDCl ) δ 10.86 (br, 1H, NH), 10.51 (br, 1H, NH),
3
0.08 (br 1H, NH), 7.51−7.42 (m, 4H, H−Ar), 7.05−6.95 (m, 4H, H−Ar), 4.28 (br, 1H, –HC(CH ) ),
.08 (br, 1H, –HC(CH ) ), 2.08−1.38 (m, 20H, CH ). IR (KBr, selected bands, cm ): 3431 m ν(N–H),
932 m, 2854 w ν(С −H), 2224 s ν(C≡N), 1601 m ν(С=N), 1512 w ν(N−С
m/z: 731.2037 [M−Cl] . C H ClF N Pt. Calcd. m/z: 731.2040.
e: Yield 22%, orange crystals. H NMR (400 MHz, CDCl ) δ 11.84 (s, 1H, NH), 11.12 (s, 1H, NH),
.92 (s, 1H, NH), 7.47 (d, J = 8.8 Hz, 2H, H−Ar), 7.44 (d, J = 8.8 Hz, 2H, H−Ar), 7.40 (d, J = 8.8
Hz, 2H, H−Ar), 7.35 (d, J = 8.8 Hz, 2H, H−Ar), 4.50−4.41 (m, 1H, –HC(CH ) ), 3.57 (s, 1H, –
HC(CH ) ), 2.12−1.27 (m, 20H, CH ). IR (KBr, selected bands, cm ): 2932 s ν(С −H), 2226 s
2
5
-1
2
5
2
+
). HRMS (ESI ),
sp3
+
carbene
3
0
33
2
5
1
3
9
3
3
3
3
3
2
5
-1
2
5
2
sp3
+
+
ν(C≡N), 1688 m ν(С=N), 1546 s ν(N−Сcarbene). HRMS (ESI ), m/z: 763.1421 [M−Cl] . C H Cl N Pt.
Calcd. m/z: 763.1449; 795.1683 [M+CH OH] . C H Cl N OPt. Calcd. m/z: 795.1711. Anal. Calcd.
30
33
3
5
+
3
31 37
3
5
for C H Cl N Pt⋅CH Cl (885.44): C, 42.05; H, 3.98; N, 7.91. Found: C, 42.13; H, 4.01; N, 7.94.
3
0
33
4
5
2
2
1
3
f: Yield 12%, orange crystals. H NMR (400 MHz, CDCl ) δ 11.93 (br, 1H, NH), 11.24 (br, 1H,
NH), 9.92 (br, 1H, NH), 7.64 (d, J = 8.4 Hz, 2H, H−Ar), 7.52 (d, J = 8.4 Hz, 2H, H−Ar), 7.37 (d, J
3
3
3
3
3
=
8.4 Hz, 2H, H−Ar), 7.34 (d, J = 8.4 Hz, 2H, H−Ar), 4.46 (s, 1H, –HC(CH ) ), 3.50 (s, 1H, –
2 5
1
0

-
1
HC(CH ) ), 2.18−1.28 (m, 20H, CH ). IR (KBr, selected bands, cm ): 3394 m ν(N–H), 2934 s, 2857
2
5
2
+
m ν(С −H), 2220 s ν(C≡N), 1572 s ν(С=N), 1542 s ν(N−С
). HRMS (ESI ), m/z: 851.0428
sp3
carbene
+
[
M−Cl] . C H Br ClN Pt. Calcd. m/z: 851.0439. Anal. Calcd. for C H Br Cl N Pt (889.40): 40.51;
30 33 2 5 30 33 2 2 5
H, 3.74; N, 7.87. Found: 40.31; H, 3.73; N, 7.80.
4
.3.General procedure for catalytic hydrosilylation of phenylacetylene
In a 5 mL round-bottomed flask equipped with a stirring bar, a solution of the selected catalyst in
-4
chloroform (2.5×10 M) was charged. The reaction flask was plugged with septum, placed into a pre-
heated oil bath at 60°C and purged with argon until complete removal of chloroform. Further, a
solution of phenylacetylene (51 mg, 0.5 mmol) and triethoxysilane (82 mg, 0.5 mmol) in anhydrous
toluene (0.2 mL) was added and the reaction mixture was stirred at 100°C. After the reaction
completion, 1,2-dimethoxyethane (7.2 mg, 0.08 mmol, used as an internal standard) was added and the
1
crude mixture was analyzed by H NMR spectroscopy. Quantifications were performed upon
integration of the selected peaks of the product against peaks of 1,2-dimethoxyethane.
4
.4.Catalytic tests in polymeric systems
The cross-linking system consisted of two components: A and B.
Component A: the calculated amount of the catalyst was diluted in CH Cl and added to
2
2
PDMS, where later the mixture was stirred and dried under vacuum at RT to remove the
solvent.
Component B: EHDMS and PDMS were mixed and carefully stirred.
The amounts required were calculated for the specific ratio of hydride and vinyl groups (3:1) in
the reaction mixture.
To 0.5 ml of component A 0.5 ml of component B was added and stirred for 30 seconds. The
mixture was then placed into a thermostat at 85 °C until a dry cured product was obtained. The
−
3
−
5
−1
total catalyst concentration in the resulting silicone rubber was 1.0 × 10 –5.0 × 10 mol⋅L .
The curing time (τcuring) was measured as the time passed from mixing components A and B to
the moment when cured rubber is obtained [30,31]. Curing times were measured as dry-to-
touch and dry-through times according to ASTM D1640 [38], the both methods results are
similar to each other. Measurements were carried out five times for each sample, duplicate
determinations agreed within ±10%.
4
.5.X-ray structure determination
The crystals of 3b⋅CH Cl were obtained by a slow evaporation of solvent at room temperature. The
2
2
crystal of compound 3b⋅CH Cl was immersed in cryo-oil, mounted in a nylon loop, and analysed at a
2
2
temperature of 170 K. The X-ray diffraction data were collected on an Agilent Technologies Excalibur
Eos and Supernova Atlas diffractometers. The structure has been solved by the direct methods and
refined by means of the SHELXL–97 program [39] incorporated in the OLEX2 program package [40].
The carbon-bound H atoms were placed in calculated positions and were included in the refinement in
the ‘riding’ model approximation, with U (H) set to1.5U (C) and C–H 0.96 Å for CH groups,
iso
eq
3
U (H) set to1.2U (C) and C–H 0.93 Å for the CH groups, and U (H) set to 1.2U (N) and N–H 0.86
iso
eq
iso
eq
Å for the NH groups Empirical absorption correction was applied in CrysAlisPro program complex
41] using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.
[
The crystal structure and crystallographic details are given in Table S2. Crystal data have been
deposited at the Cambridge Crystallographic Data Centre (CCDC) with deposition number
CCDC 1983029 for 3b
⋅CH Cl .
2 2
4
.6.Computational details
The full geometry optimization and total energy calculations have been carried out at the DFT
hybrid level of theory using Becke's three parameter hybrid exchange functional in combination with
the gradient-corrected correlation functional of Lee, Yang, and Parr (B3LYP)[36,37,38,39] and
1
1

standard basis 6-31+G(d,p) for light atoms and pseudopotential CEP 1-21G [46] for palladium using
the Gaussian 03 program package [47].
4
.7.Cell lines and cultivation conditions
The cytotoxicity tests were performed on three human cancer cell lines. CH1/PA-1 cells were kindly
provided by Lloyd R. Kelland (CRC Centre for Cancer Therapeutics, Institute of Cancer Research,
Sutton, UK). SW480 (human adenocarcinoma of the colon), A549 (human non-small cell lung cancer)
were obtained from Brigitte Marian (Institute of Cancer Research, Department of Medicine I, Medical
2
University of Vienna, Austria). Cell monolayer adherent cultures were grown in 75 cm culture flasks
(
1
Starlab, Germany) in complete medium [i.e., minimal essential medium (MEM) supplemented with
0% heat-inactivated fetal bovine serum (Biowest, France), 1 mM sodium pyruvate, 1% nonessential
amino acids from 100× ready-to-use stock and 4 mM L-glutamine (all purchased from Sigma-Aldrich,
Austria)]. Cell cultures were incubated at 37 °C in a moist atmosphere containing 5% CO2.
4
.8.Cytotoxicity tests in cancer cell lines
The cytotoxic activity in vitro was determined by means of colorimetric microculture MTT assay
MTT = 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide). For this purpose, cells
(
were harvested from culture flasks by trypsinization and seeded into 96-well plates (Starlab, Germany)
3
3
3
in densities of 1×10 cells/well (CH1/PA-1), 2×10 cells/well (SW480) and 3×10 cells/well (A549) in
volume of 100 μL/well. Cells were allowed to settle and resume proliferation for 24 h before exposure
to the drugs. Stock solutions of each complex were prepared in DMSO, appropriately diluted in
complete MEM medium (not to exceed 0.5% DMSO concentration on cells) and instantly added to the
plates (100 μL/well). After continuous exposure for 96 h, drug solutions were replaced with 100
µL/well of a 1:6 MTT/RPMI 1640 solution (MTT solution, 5 mg/mL of MTT reagent in phosphate-
buffered saline; RPMI 1640 medium, supplemented with 10% heat-inactivated fetal bovine serum and
4
mM L-glutamine). After incubation for 4 h, the medium/MTT mixtures were removed, and the
formazan crystals formed by viable cells were dissolved in DMSO (150 μL/well). Optical densities
were measured at 550 nm with a microplate reader (ELx808 Absorbance Microplate Reader, Bio-Tek,
USA), using a reference wavelength of 690 nm to correct for unspecific absorption. The quantity of
viable cells was expressed in relation to untreated control and 50% inhibitory concentrations (IC50)
were calculated from concentration-effect curves by interpolation. Evaluation is based on means from
at least three independent experiments, each comprising triplicate per concentration level.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships
that could have appeared to influence the work reported in this paper.
Acknowledgments
A part concerning to synthesis, photophysical properties, and catalytic activity of the ADC-
platinum(II) complexes was supported by the Government of Saint Petersburg (grant N 4ntd-19 from
1
5.11.2019, T.G.C.). A part on photophysical properties of silicone rubbers was supported by the
Russian Science Foundation (project 20-19-00256, R.M.I.). The authors are grateful to
Academician V. Yu. Kukushkin (Saint Petersburg State University) for fruitful discussions. The
authors also thank the Centre for Optical and Laser Materials Research, Centre for Chemical Analysis
and Materials Research, Cryogenic Department, and Centre of Magnetic Resonance (all belong to
Saint Petersburg State University) for physicochemical measurements.
Appendix A. Supplementary data
Supplementary data to this article can be found online at
References
[
1]
L.M. Slaughter, Acyclic aminocarbenes in catalysis, ACS Catal. 2 (2012) 1802–1816.
doi:10.1021/cs300300y.
1
2

[
2]
V.P. Boyarskiy, K. V. Luzyanin, V.Y. Kukushkin, Acyclic diaminocarbenes (ADCs) as a
promising alternative to N-heterocyclic carbenes (NHCs) in transition metal catalyzed organic
transformations, Coord. Chem. Rev. 256 (2012) 2029–2056. doi:10.1016/j.ccr.2012.04.022.
[
[
[
[
[
3]
4]
5]
6]
7]
H. V. Huynh, The Organometallic Chemistry of N-Heterocyclic Carbenes, John Wiley & Sons,
Inc., Chichester, UK, 2017.
H.V. Huynh, Electronic Properties of N-Heterocyclic Carbenes and Their Experimental
Determination, Chem. Rev. 118 (2018) 9457–9492. doi:10.1021/acs.chemrev.8b00067.
S.P. Nolan, ed., N-Heterocyclic carbenes: effective tools for organometallic synthesis, Wiley-
VCH: Weinheim, 2014.
R.W. Alder, P.R. Allen, M. Murray, A.G. Orpen, Bis(diisopropylamino)carbene, Angew.
Chemie Int. Ed. English. 5 (1996) 1121–1123. doi: 10.1002/anie.199611211.
E.L. Rosen, M.D. Sanderson, S. Saravanakumar, C.W. Bielawski, Synthesis and study of the
first N-aryl acyclic diaminocarbene and its transition-metal complexes, Organometallics. 26
(
2007) 5774–5777. doi:10.1021/om7007925.
[
8]
9]
M.S. Collins, E.L. Rosen, V.M. Lynch, C.W. Bielawski, Differentially substituted acyclic
diaminocarbene ligands display conformation-dependent donicities, Organometallics. 29 (2010)
3
047–3053. doi:10.1021/om1004226.
[
[
[
[
R.A. Michelin, A.J.L. Pombeiro, M.F.C. Guedes da Silva, Aminocarbene complexes derived
from nucleophilic addition to isocyanide ligands, Coord. Chem. Rev. 218 (2001) 75–112.
10] K.V. Luzyanin, A.J.L. Pombeiro, Carbene complexes derived form metal-bound isocyanides,
in: V. Nenajdenko (Ed.), Wiley-VCH, 2012: pp. 531–550.
11] V.P. Boyarskiy, N.A. Bokach, K. V. Luzyanin, V.Y. Kukushkin, Metal-mediated and metal-
catalyzed reactions of isocyanides, Chem. Rev. 115 (2015) 2698–2779. doi:10.1021/cr500380d.
12] M.A. Kinzhalov, K. V. Luzyanin, V.P. Boyarskiy, M. Haukka, V.Y. Kukushkin, ADC-based
palladium catalysts for aqueous suzuki-miyaura cross-coupling exhibit greater activity than the
most advantageous catalytic systems, Organometallics. 32 (2013) 5212–5223.
doi:10.1021/om4007592.
[
13] K. V. Luzyanin, A.G. Tskhovrebov, M. Carolina Carias, M. Fátima C Guedes Da Silva, A.J.L.
Pombeiro, V.Y. Kukushkin, Novel Metal-mediated (M = Pd, Pt) coupling between isonitriles
and benzophenone hydrazone as a route to aminocarbene complexes exhibiting high catalytic
activity (M = Pd) in the Suzuki-Miyaura reaction, Organometallics. 28 (2009) 6559–6566.
doi:10.1021/om900682v.
[
[
14] R.S. Chay, K. V. Luzyanin, Evaluation of catalytic properties of aminocarbene species derived
from the integration between 3-iminoisoindolin-1-ones and palladium-bound isonitriles in
Suzuki-Miyaura cross-coupling, Inorganica Chim. Acta. 380 (2012) 322–327.
doi:10.1016/j.ica.2011.09.047.
15] R.S. Chay, K. V. Luzyanin, V.Y. Kukushkin, M.F.C. Guedes Da Silva, A.J.L. Pombeiro, Novel
palladium-aminocarbene species derived from metal-mediated coupling of isonitriles and 1,3-
diiminoisoindoline: Synthesis and catalytic application in Suzuki-Miyaura cross-coupling,
Organometallics. 31 (2012) 2379–2387. doi:10.1021/om300020j.
[
[
16] B.G.M. Rocha, E.A. Valishina, R.S. Chay, M.F.C. Guedes Da Silva, T.M. Buslaeva, A.J.L.
Pombeiro, V.Y. Kukushkin, K. V. Luzyanin, ADC-metal complexes as effective catalysts for
hydrosilylation of alkynes, J. Catal. 309 (2014) 79–86. doi:10.1016/j.jcat.2013.09.003.
17] R.S. Chay, B.G.M. Rocha, A.J.L. Pombeiro, V.Y. Kukushkin, K. V. Luzyanin, Platinum
Complexes with Chelating Acyclic Aminocarbene Ligands Work as Catalysts for
1
3

Hydrosilylation of Alkynes, ACS Omega. 3 (2017) 863–871. doi:10.1021/acsomega.7b01688.
[
18] D. V. Boyarskaya, E. Bulatov, I.A. Boyarskaya, T.G. Chulkova, V.A. Rassadin, E.G.
Tolstopjatova, I.E. Kolesnikov, M.S. Avdontceva, T.L. Panikorovskii, V. V. Suslonov, M.
Haukka, Syntheses and Structures of a Series of Acyclic Diaminocarbene Palladium(II)
Complexes Derived from 3,4-Diaryl-1H-pyrrol-2,5-diimines and Bisisocyanide Palladium(II)
Complexes, Organometallics. 38 (2019) 300−309. doi:10.1021/acs.organomet.8b00725.
[
[
19] K. V. Luzyanin, A.J.L. Pombeiro, M. Haukka, V.Y. Kukushkin, Coupling between 3-
Iminoisoindolin-1-ones and Complexed Isonitriles as a Metal-Mediated Route to a Novel Type
of Palladium and Platinum Iminocarbene Species, Organometallics. 27 (2008) 5379–5389.
doi:10.1021/om800517c.
20] A.M. Afanasenko, D.V. Boyarskaya, I.A. Boyarskaya, T.G. Chulkova, Y.M. Grigoriev, I.E.
Kolesnikov, M.S. Avdontceva, T.L. Panikorovskii, A.I. Panin, A.N. Vereshchagin, M.N.
Elinson, Structures and photophysical properties of 3,4-diaryl-1H-pyrrol-2,5-diimines and 2,3-
diarylmaleimides, J. Mol. Struct. 1146 (2017) 554−561. doi:10.1016/j.molstruc.2017.06.048.
[
[
[
21] L. Mercs, M. Albrecht, Beyond catalysis: N-heterocyclic carbene complexes as components for
medicinal, luminescent, and functional materials applications, Chem. Soc. Rev. 39 (2010)
1
903–1912. doi:10.1039/b902238b.
22] R. Jazzar, M. Soleilhavoup, G. Bertrand, Cyclic (Alkyl)- And (Aryl)-(amino)carbene Coinage
Metal Complexes and Their Applications, Chem. Rev. 120 (2020) 4141–4168.
doi:10.1021/acs.chemrev.0c00043.
23] T. V. Serebryanskaya, M.A. Kinzhalov, V. Bakulev, G. Alekseev, A. Andreeva, P. V.
Gushchin, A. V. Protas, A.S. Smirnov, T.L. Panikorovskii, P. Lippmann, I. Ott, C.M. Verbilo,
A. V. Zuraev, A.S. Bunev, V.P. Boyarskiy, N.A. Kasyanenko, Water soluble palladium(ii) and
platinum(ii) acyclic diaminocarbene complexes: Solution behavior, DNA binding, and
antiproliferative activity, New J. Chem. 44 (2020) 5762–5773. doi:10.1039/d0nj00060d.
[
24] B. Bertrand, A.S. Romanov, M. Brooks, J. Davis, C. Schmidt, I. Ott, M. O’Connell, M.
Bochmann, Synthesis, structure and cytotoxicity of cyclic (alkyl)(amino) carbene and acyclic
carbene complexes of group 11 metals, Dalt. Trans. 46 (2017) 15875–15887.
doi:10.1039/c7dt03189k.
[
[
25] S. Montanel-Pérez, R. Elizalde, A. Laguna, M.D. Villacampa, M.C. Gimeno, Synthesis of
Bioactive N-Acyclic Gold(I) and Gold(III) Diamino Carbenes with Different Ancillary Ligands,
Eur. J. Inorg. Chem. 2019 (2019) 4273–4281. doi:10.1002/ejic.201900606.
26] Y.Y. Scaffidi-Domianello, A.A. Legin, M.A. Jakupec, A. Roller, V.Y. Kukushkin, M. Galanski,
B.K. Keppler, Novel Oximato-Bridged Platinum(II) Di- and Trimer(s): Synthetic, Structural,
and in Vitro Anticancer Activity Studies, Inorg. Chem. 51 (2012) 7153–7163.
doi:10.1021/ic300148e.
[
[
[
[
27] M. Poyatos, A. Maisse-François, S. Bellemin-Laponnaz, L.H. Gade, Coordination chemistry of
a modular N,C-chelating oxazole-carbene ligand and its applications in hydrosilylation
catalysis, Organometallics. 25 (2006) 2634–2641. doi:10.1021/om060166u.
28] J.J. Hu, F. Li, T.S. Andy Hor, Novel Pt(II) Mono- and Biscarbene Complexes: Synthesis,
Structural Characterization and Application in Hydrosilylation Catalysis Jian, Organometallics.
2
8 (2009) 1212–1220. doi:10.1016/j.jorganchem.2008.10.048.
29] G.F. Silbestri, J.C. Flores, E. De Jesús, Water-soluble N-heterocyclic carbene platinum(0)
complexes: Recyclable catalysts for the hydrosilylation of alkynes in water at room
temperature, Organometallics. 31 (2012) 3355–3360. doi:10.1021/om300148q.
30] C. Lu, S. Gu, W. Chen, H. Qiu, Platinum(ii) complexes with polydentate N-heterocyclic
carbenes: Synthesis, structural characterization and hydrosilylation catalysis, Dalt. Trans. 39
1
4

(
2010) 4198–4204. doi:10.1039/b924587a.
[
[
31] A. Cook, R. Linstead, Phthalocyanines. Part XI . The preparation of octaphenylporphyrazines
from diphenylmaleinitrile, J. Chem. Soc. (1937) 929–933. doi: 10.1039/JR9370000929.
32] T.F. Baumann, A.G.M. Barrett, B.M. Hoffman, Porphyrazine Binaries: Synthesis,
Characterization, and Spectroscopy of a Metal-Linked Trinuclear Porphyrazine Dimer, Inorg.
Chem. 36 (1997) 5661–5665. doi:10.1021/ic9701367.
[
[
33] F. Bonati, G. Minghetti, New isocyanide complexes of platinum(II), J. Organomet. Chem. 24
(
1970) 251–256. doi:10.1016/S0022-328X(00)91586-9.
34] A.G. Tskhovrebov, K. V. Luzyanin, M. Haukka, V.Y. Kukushkin, Synthesis and
characterization of cis-(RNC)2PtII species useful as synthons for generation of various
(
aminocarbene)Pt II complexes, J. Chem. Crystallogr. 42 (2012) 1170–1175.
doi:10.1007/s10870-012-0371-0.
[
[
35] M.J. Owen, The Polysiloxanes, Silicon. 8 (2016) 617–618. doi:10.1007/s12633-015-9306-7.
36] J. Li, J. Peng, Y. Deng, C. Ma, G. Zhang, Y. Bai, G. Lai, Synthesis of platinum acetylide
complexes and their application in curing silicone rubber by hydrosilylation, Appl. Organomet.
Chem. 26 (2012) 461–466. doi:10.1002/aoc.2881.
[
37] I. Kownacki, B. Marciniec, K. Szubert, M. Kubicki, M. Jankowska, H. Steinberger, S.
Rubinsztajn, Tris(triorganosilyl)phosphites-New ligands controlling catalytic activity of Pt(0)
complex in curing of silicone rubber, Appl. Catal. A Gen. 380 (2010) 105–112.
doi:10.1016/j.apcata.2010.03.041.
[
[
[
38] J. Koleske, ed., Paint and Coating Testing Manual: 15th. ed of the Gardner-Sward Handbook.,
1
5th. ed., ASTM International, 2012, West Conshohocken, PA.
39] G.M. Sheldrick, A short history of SHELX., Acta Crystallogr. A. 64 (2008) 112–22.
doi:10.1107/S0108767307043930.
40] O. V. Dolomanov, L.J. Bourhis, R.J. Gildea, J.A.K. Howard, H. Puschmann, OLEX2ꢀ: a
complete structure solution, refinement and analysis program , J. Appl. Crystallogr. 42 (2009)
3
39–341. doi:10.1107/s0021889808042726.
[
[
41] CrysAlisPro, Agilent Technologies, Version 1.171.36.20 (Release 27 06 2012).
42] A.D. Becke, Density-functional thermochemistry. III. The role of exact exchange, J. Chem.
Phys. 98 (1993) 5648–5652. doi:10.1063/1.464913.
[
[
[
[
[
43] P.J. Stephens, F.J. Devlin, C.S. Ashvar, C.F. Chabalowski, M.J. Frisch, Theoretical calculation
of vibrational circular dichroism spectra, Faraday Discuss. 99 (1994) 103–119.
doi:10.1039/FD9949900103.
44] P.J. Stephens, F.J. Devlin, C.F. Chabalowski, M.J. Frisch, Ab Initio calculation of vibrational
absorption and circular dichroism spectra using density functional force fields, J. Phys. Chem.
9
8 (1994) 11623–11627. doi:10.1021/j100096a001.
45] C. Lee, W. Yang, R.G. Parr, Development of the Colle-Salvetti correlation-energy formula into
a functional of the electron density., Phys. Rev. B. 37 (1988) 785–789. doi:
1
0.1103/PhysRevB.37.785.
46] W.J. Stevens, M. Krauss, H. Basch, P.G. Jasien, Relativistic compact effective potentials and
efficient shared-exponent basis-sets for the 3rd-row, 4th-row and 5th-row atoms, Can. J. Chem.
7
0 (1992) 612–630. doi: 10.1139/v92-085.
47] P.J.A. Frisch, M.J. Trucks, G.W. Schlegel, H.B. Scuseria, G.E. Robb, M.A. Cheeseman, J.R.
Montgomery, J.A. Vreven Jr., T. Kudin, K.N. Burant, J.C. Millam, J.M. Iyengar, S.S. Tomasi,
1
5

J. Barone, V. Mennucci, B. Cossi, M. Scalmani, G. Rega, N. Petersson, Gaussian 03, (2003).
1
6

Declaration of interests
☒
The authors declare that they have no known competing financial interests or personal relationships
that could have appeared to influence the work reported in this paper.
☐
The authors declare the following financial interests/personal relationships which may be considered
as potential competing interests:
Best regards,
Tatiana G. Chulkova
(on behalf of the authors)