Complexes of palladium(II) with N-heterocyclic carbenes from adamantylimidazole as precatalysts for thiophene and imidazole arylation

Article abstract of DOI:10.1007/s11172-019-2664-3

Complexes of palladium(II) with N-heterocyclic carbenes of the PEPPSI-type were synthesized by the reaction of PdCl₂ with 1-adamantyl-3-(R-methyl)-1H-imidazolium salts. These complexes were used as productive precatalysts for substituted thioph

Full text of DOI:10.1007/s11172-019-2664-3

Russian Chemical Bulletin, International Edition, Vol. 68, No. 11, pp. 2039—2047, November, 2019
2039
Complexes of palladium(II) with N-heterocyclic carbenes
from adamantylimidazole as precatalysts for thiophene and imidazole arylation*
M. S. Denisov,a M. V. Dmitriev,b A. A. Gorbunov,a and V. A. Glushkova,b
аInstitute of Technical Chemistry, Perm Federal Scientific Center, Ural Branch of the Russian Academy of Sciences,
3 ul. Akad. Koroleva, 614013 Perm, Russian Federation.
Fax: +7 (342) 237 8262. Е-mail: denisov.m@itcras.ru
bPerm State National Research University,
5 ul. Bukireva, 614990 Perm, Russian Federation
Complexes of palladium(II) with N-heterocyclic carbenes of the PEPPSI-type were
synthesized by the reaction of PdCl2 with 1-adamantyl-3-(R-methyl)-1H-imidazolium salts.
These complexes were used as productive precatalysts for substituted thiophene and imidazole
arylation by C—H-activation.
Key words: N-heterocyclic carbenes, palladium, C—H-activation, arylation, imidazole,
thiophene.
N-Heterocyclic carbenes (NHC) and their metal
complexes occupy one of pivotal positions in the contem-
porary organometallic chemistry.1—4 Although in many
cases NHC are not inferior to phosphine ligands, they still
have not found wide practical application in cross coupling
reactions. A reason for this could probably be a relative
hydrolytic instability of NHC complexes.5 This problem
can be approached with the aid of a specific class of
NHC—Pd complexes, namely, so called PEPPSI com-
plexes (PEPPSI is Pyridine Enhanced Precatalysts: Pre-
paration, Stabilisation and Initiation).6—9 The latter are
used as precatalysts for various cross coupling reactions
including those of Suzuki10—12, Negishi13,14, Sono-
gashira15, as well as amination,16,17 and sulfenylation18
reactions. Studies have been reported on application of
these complexes in the reactions of С—Н-activation such
such complexes that can further withstand extraction in
methylene chloride—water system during their isolation.
The parent imidazolium salts were obtained by quat-
ernization of 1-adamantylimidazole with alkylation agents
such as iodomethane, 1-(chloromethyl)naphthalene, and
chlorodiphenylmethane (Scheme 1). Salts of 1-adaman-
tylimidazolium bearing methyl (1а), 1-naphthyl (1b), or
diphenylmethyl (1c) groups at the C(3) atom were syn-
thesized. The halide counterion was then replaced with
tetrafluoroborate one since the latter is not capable of
forming complexes with palladium atom.
Scheme 1
as synthesis of heterocycles19,20, arylation of phenols21
thiophenes22,23, pyrazoles24, oxazoles25, imidazoles26—29
,
,
and also benzyl group activation30. Recently, we have
synthesized novel unsymmetrically substituted PEPPSI-
type palladium(II) complexes and showed their possible
use as precatalysts in the reaction of С—Н-activation/
arylation of substituted thiophenes.23
The present work is aimed at the synthesis of novel un-
symmetrically substituted PEPPSI palladium(II) complexes
based on 1-adamantyl-1H-imidazole and study of their
catalytic activity in arylation of thiophenes and imidazoles.
Introduction of a bulky hydrophobic moiety (adamantyl,
naphthyl, benzhydryl) improves the hydrolytic stability of
i. MeI (2 equiv.), PhCH3, ~20 C, 24 h; ii. XCHR1R2 (1 equiv.),
MeCN, reflux, 4 h.
Compound
X
I
R1
H
R2
H
H
Yield (%)
195
157
1a
1b
1c
2a
2b
2c
Cl
Br
—
—
—
1-Naphthyl
Ph
Ph
H
H
179
100
181
173
* Based on the materials of the V International Scientific
Conference "Advances in Synthesis and Complexing" (April 22—26,
2019, Moscow, Russia).
H
1-Naphthyl
Ph
Ph
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2039—2047, November, 2019.
1066-5285/19/6811-2039 © 2019 Springer Science+Business Media, Inc.

2040 Russ. Chem. Bull., Int. Ed., Vol. 68, No. 11, November, 2019
Denisov et al.
PEPPSI complexes were synthesized according to the
known procedure23,31 comprising the one-pot NHC for-
mation from imidazolium salt followed by coordination
of the former with the solvated palladium(II). As auxiliary
ligands, pyridine, 3-methylpyridine and 4-methylpyridine
were used (Scheme 2). Unfortunately, we failed to obtain
complexes with 2-methylpyridine. This was probably
caused by steric hindrances as the reaction was terminated
at the step of formation of trans-dichlorobis(2-methylpyr-
idine)palladium(II) complex.32
spectroscopy and X-ray diffraction data. Signals of the
С(2) atom of imidazolium ring in the 13С NMR spectra,
disappearing in DEPT spectra, are found in the range of
δ 145—151 corresponding to the literature data23 for such
complexes (δ 143—146).
Complex 3a crystallizes in the centrosymmetric space
group of monoclinic syngony (Fig. 1). Adamantyl sub-
stituent in the molecule is disordered on two positions
with an occupancy of 0.61(2) : 0.39(2); minor disorder
component has been omitted in the Figure. In the crystal
molecules are connected in one-dimentional chains ex-
tended along the axis b, due to a nonclassical intermo-
lecular hydrogen bond C(2)—H(2)∙∙∙Cl(2) [1 – x, –0.5 + y,
1.5 – z]. Two crystallographically independent molecules
of complex 5c crystallize in the centrosymmetric space
group P–1 as a solvate with one molecule of acetonitrile
(Fig. 2 shows only one of the molecules). Independent
molecules of the complex are linked to each other via
intermolecular hydrogen bond C(2A)—H(2A)∙∙∙Cl(2)
[1 – x, 1 – y, 1 – z] (indices "A" designate atoms of the
second independent molecule).
Scheme 2
Using arylation of 2,3-diphenylthiophene with iodo-
benzene as an example, catalytic activity of complexes
3a—c was studied (Scheme 3). Results of this study are
given in Table 1. Reported data23 for complex 3d with
benzyl substituent and PEPPSI-IPr are given for com-
parison.6 Catalytic activity of palladium compounds
Pd[P(Ph)3]4 (see Ref. 34) and PdCl2 was tested for com-
parison under the same conditions. As illustrated in Table 1,
in the model reaction complex with naphthylmethyl sub-
stituent (3b) is more active whereas complexes bearing
methyl (3а) and diphenylmethyl (3с) substituents dem-
onstrate lower catalytic activity compared to that found
i. PdCl2 (1 equiv.), K2CO3 (5 equiv.), pyridine; ii. Picoline
(2 equiv.), MeCN.
Com-
pound
3a
R1
R2 R3
R4
t
T/C Yield (%)
H
H
H
H
H
H
H
5 h
5 h
5 h
65
80
80
51
63
34
77
27
41
39
46
3b
1-Naphthyl
3c
Ph
Ph
H
Ph Me
H
H
Ph
H
Me
H
H
H
Me
Me
Me
4b
1-Naphthyl
50 min 65
4c
Ph
5 h
5 h
5 h
5 h
65
65
80
80
Table 1. Catalytic activity of palladium compounds in arylation
of 2,3-diphenylthiophene with iodobenzene
5a
H
1-Naphthyl
Ph
H
H
H
5b
5c
Precatalyst
Conversion of
Yield of 6*
We failed to develop reaction conditions to obtain
PEPPSI complex from compound 1а and 3-methyl-
pyridine. The known procedure33 to synthesize PEPPSI
complexes with bromide and iodide ligands starting from
palladium(II) acetate and excess of potassium halide proved
to be inapplicable for salts 1а and 1с since only the forma-
tion of bispyridine complex was observed. During the
reaction progress, in some experiments palladium black
was formed; in this case the process was terminated prior
to the standard time (5 h). Control of temperature (from
65 to 80 С) and reaction time (from 50 min to 5 h) based
on the appearance of palladium black serves to rise sig-
nificantly the yields of the complexes and decrease the
duration of the synthesis (as in the case of compound 4b,
obtained in 50 min).
2,3-diphenylthiophene*
%
3a
3b
3c
3d
4b
4c
5а
5b
97
99
99
98
97
83
96
94
95
100
96
95
45
14
55
84
46
59
43
36
46
62
39
69
58
41
0
5c
PEPPSI-IPr
Pd[P(Ph)3]4
PdCl2
3b (PhBr in place of PhI)
3b (PhCl in place of PhI)
0
Composition and structure of complexes 3—5 were
confirmed by elemental analysis, 1Н and 13С NMR
* GC-MS data.

Thiophene and imidazole arylation
Russ. Chem. Bull., Int. Ed., Vol. 68, No. 11, November, 2019
2041
C(2)
C(4)
N(1)
C(3)
Cl(2)
C(12)
C(1)
N(2)
C(16)
Pd(1)
C(5)
C(10)
N(3)
C(13)
C(17)
C(11)
C(6)
C(7)
Cl(1)
C(15)
C(18)
C(14)
C(9)
C(19)
C(8)
Fig. 1. Мolecular structure of complex 3a. Тhermal ellipsoids are set at the 30% probability level.
C(21)
C(22)
C(18)
C(26)
C(23)
C(25)
C(17)
C(2)
N(1)
C(3)
C(13)
C(12)
C(24)
C(19)
C(20)
N(2)
Cl(2)
C(14)
C(1)
C(11)
C(16)
C(6)
C(4)
C(15)
Pd(1)
C(27)
C(5)
Cl(1)
C(10)
N(3)
C(7)
C(28)
C(31)
C(9)
C(8)
C(29)
C(30)
C(32)
Fig. 2. Мolecular structure of complex 5c. Тhermal ellipsoids are set at the 30% probability level.

2042 Russ. Chem. Bull., Int. Ed., Vol. 68, No. 11, November, 2019
Denisov et al.
for benzyl substituent (3d). The features described are also
observed for picolinic complexes 4b,c and 5a—c. In our
earlier study negligible response of the catalytic behavior
of complexes to the transfer from pyridine to picoline was
noted.23 By contrast, in the present study a decrease in
activity was observed. When passing to 3-methylpyridine,
this decrease was much more pronounced than in the case
of 4-methylpyridine. Complex 3b was superior in activity
to the known catalysts such as PEPPSI-IPr,6 Pd[P(Ph)3]4
(see Ref. 34), and PdCl2. Using catalytic reactions with
complex 3b as an example, it was demonstrated that chloro-
benzene and bromobenzene are unsuitable as arylating
agents — these substrates do not enter arylation reaction.
N(3)
C(9)
C(8)
C(6)
C(5)
C(4)
C(7)
C(1)
N(1)
C(10)
N(2)
C(11)
C(3)
C(2)
Fig. 3. Molecular structure of compound 7. Thermal ellipsoids
are set at the 50% probability level.
compound 7 was the single arylation product.36 These
experiments revealed that 2-methylimidazole did not
undergo arylation under given conditions. Structure of
compound 7 (Fig. 3) is identical to the previously pub-
lished one.35 Similar to arylation of 2,3-diphenylthio-
phene, PEPPSI complex with naphthylmethyl substituent
(3b) was high active catalyst at 130 С.
Scheme 3
Scheme 4
Ad is 1-adamantyl.
i. Cat (2 mol.%), pivalic acid (30 mol.%), Cs2CO3 (2.5 equiv.),
dimethylacetamide (DMA), reflux, 3 h.
Table 2 shows data obtained in arylation of 1-methyl-
imidazole with p-bromobenzonitrile proceeding with as
low as 0.5 mol.% of palladium 3a—d (Scheme 4). Since
at 110 С conversion was ~50%, all experiments were also
performed at 130 С. Arylation proceeded involving С(5)
atom of 1-methylimidazole similar to the previously
reported process.35 In contrast to the literature data,
i. Cat (0.5 mol.%), pivalic acid (30 mol.%), K2CO3 (2 equiv.),
DMA, 110—130 C, 10 h.
Although studying the nature of the catalyst was not
among the purposes of our work, taking into account the
literature data37—40 and the reaction conditions, it can be
assumed that catalysts represent nanoparticles of palla-
dium(0) or their clusters stabilized by N-heterocyclic
carbene ligands.
Table 2. Catalytic activity of complexes 3a—d in combination
of p-bromobenzonitrile with 1-methyl-1Н-imidazole
To summarize, the procedure to obtain adamantyl-
substituted Pd-PEPPSI complexes through the reaction
between PdCl2 and 1-adamantyl-3-methyl-1Н-imid-
azolium salts and pyridine (or picolines) has been im-
proved. Complexes of Pd-PEPPSI with imidazole NHC-
ligands were for the first time studied as precatalysts in
arylation of 1-methyl-1Н-imidazole via С—Н-activation.
By the example of catalytic arylation of 2,3-diphenylthio-
phene with complex 3b it has been demonstrated that novel
complexes Pd-PEPPSI bearing adamantyl-substituted
ligands can be superior to their known23 analogs in catal-
ytic activity. Ease of synthesis and high catalytic activity
(in terms of С—Н-activation) of Pd-PEPPSI complexes
with 1-adamantyl-3-methyl(1-naphthyl)-substituted li-
Precatalyst
T/С
Conversion of
Yield of 7*
p-bromobenzonitrile*
%
3a
3b
3c
3d
110
130
110
130
110
130
110
130
58
87
30
91
55
78
39
55
27
41
15
87
20
40
16
25
* GC-MS date.

Thiophene and imidazole arylation
Russ. Chem. Bull., Int. Ed., Vol. 68, No. 11, November, 2019
2043
adamantane); 2.15 (s, 6 H, 3 2-СН2 of adamantane); 2.22 (br.s,
3 H, 3 3-СН of adamantane); 6.16 (s, 2 Н, CH2); 7.11 (t, 1 H,
СН of imidazole, J = 1.6 Hz); 7.40—7.49 (m, 3 H, 2 3,6-СH of
naphthalene, СН of imidazole); 7.55 (ddd, 1 H, 7-СН of naphth-
alene, J1 = 8.2 Hz, J2 = 7.2 Hz, J3 = 1.4 Hz); 7.69 (d, 1 H, 2-СН
of naphthalene, J = 6.8 Hz); 7.83 (d, 1 H, 4-СН of naphthalene,
J = 4.4 Hz); 7.83 (d, 1 H, 5-СН of naphthalene, J = 4.8 Hz);
8.24 (d, 1 H, 8-СН of naphthalene, J = 8.0 Hz); 11.10 (s, 1 Н,
2-СН of imidazole). 13С NMR, δ: 29.3; 35.10; 42.6; 50.7; 60.4;
118.3; 121.3; 123.0; 125.3; 126.3; 127.5; 128.8; 128.8; 129.2;
130.3; 131.1; 133.8; 135.8.
gand enable their application in catalytic arylation via
С—Н-activation of substituted thiophenes and imidazoles
to be considered.
Experimental
1Н and 13С spectra were recorded in CDCl3 on a Bruker
Avance Neo 400 (400 and 100 MHz) spectrometer; chemical
shifts are given relatively to an internal standard: for 1Н NMR
spectra HMDS was used, for 13С NMR spectra the residual
proton signals of deuterated solvent were used as references
(δ 77.0). IR spectra were obtained on a Bruker FT-IR VERTEX
80v Fourier spectrometer (in a thin film obtained by evaporation
of a substance solution in chloroform directly on the NaCl glass
(hereinafter, CHCl3) or in suspension in paraffin oil). The elec-
tron impact mass spectra (70 eV) were recorded on an Agilent
Technologies 6890N/5975B apparatus, capillary column НР-5ms,
300000.25 mm, 0.25 m, vaporization temperature 260—290 С,
temperature programming in the range 20—40 C min–1, helium
as a carrier-gas, 1 mL min–1. Melting points were determined
on a PTP-2 instrument. Elemental analysis (C, H, N) was per-
formed on a CHNS VARIO EL CUBE apparatus (Germany).
Silicagel 60 (Alfa Aesar, 0.032—0.070 mm) was used for column
chromatography. Benzhydryl bromide, PdCl2, 1-chloromethyl-
naphthalene, 3-picoline, 4-picoline, 1-methylimidazole, and
2-methylimidazole (Alfa Aesar, Great Britain); pyridine (reagent
grade), acetonitrile (extra pure), rectified ethanol, K2CO3 (re-
agent grade), petroleum ether (40—70 С), iodomethane (reagent
grade), ethyl acetate (reagent grade), acetone (reagent grade),
methylene chloride (reagent grade, stabilized with 0.5% methanol),
2,3-diphenylthiophene (reagent grade), p-bromobenzonitrile
(reagent grade), chlorobenzene (reagent grade), bromobenzene
(reagent grade), iodobenzene (reagent grade), and phenanthrene
(reagent grade) of domestic production were used. 1-Adamantyl-
1Н-imidazole41 and Pd[P(Ph)3]4 (see Ref. 42) were obtained
according to the previously reported procedures.
1-Adamantyl-3-(diphenylmethyl)-1Н-imidazolium bromide
monohydrate (1с). Yield 0.83 g (79%), pale-yellow powder, m.p.
255—257 С (EtOAc). Found (%): C, 66.06; H, 6.10; N, 6.79.
C26H29BrN2•Н2O. Calculated (%): C, 66.81; H, 6.68; N, 5.99.
IR (suspension in paraffin oil), ν/cm–1: 3182; 3162; 3142; 3089;
3050; 2787; 2745; 2718; 2686; 2611; 1584; 1567; 1538; 1498;
1345; 1311; 1273; 1252; 1204; 1181; 1168; 1147; 1114; 1103;
1084; 1029; 1002; 996; 880; 859; 828; 801; 761; 705; 654; 643;
1
637; 621; 614; 593; 519. Н NMR, δ: 1.74 (br.s, 6 H, 3 4-СН2
of adamantane); 2.23 (br.s, 6 Н, 3 2-СН2 of adamantane); 2.26
(br.s, 3 Н, 3 3-СН of adamantane); 7.14 (s, 1 Н, СН of imid-
azole); 7.25—7.30 (m, 4 Н, 4 СН, m-Ph); 7.31—7.34 (m, 6 Н,
4 СН, o-Ph, 2 CH, p-Ph); 7.58 (br.s, 1 Н, СН); 8.02 (s, 1 Н,
СН of imidazole); 10.59 (s, 1 Н, 2-СН Ar). 13С NMR, δ: 29.3; 35.1;
42.6; 60.8; 65.8; 119.0; 120.9; 128.3; 128.9; 129.0; 135.5; 136.9.
Synthesis of tetrafluoroborates 2a—c (general procedure).
A suspension of an imidazolium salt (2.25 mmol) in ethanol
(10 mL) was heated until complete dissolution. To a clear solu-
tion, a solution of ammonium tetrafluoroborate (2.5 mmol) in
water (5 mL) was added and the resulting solution was left for
evaporation in a fume hood. Crystals of salts 2а—c precipitated
were filtered off and dried.
1-Adamantyl-3-methyl-1Н-imidazolium tetrafluoroborate
semihydrate (2а). Yield 0.705 g (quantitative), white or pale-
yellow crystals, m.p. 171—172 С. Found (%): C, 53.91; H, 6.22;
N, 8.76. C14H21BF4N2•0.5H2O. Calculated (%): C, 53.70;
H, 7.08; N, 8.59. IR (СHCl3), ν/cm–1: 3425; 3382; 3166; 3113;
3069; 2915; 2864; 1570; 1558; 1451; 1368; 1345; 1312; 1284;
1261; 1245; 1191; 1166; 1106; 1070; 1045; 1034; 998; 841; 829;
815; 772; 750; 659; 638; 618; 521; 419. 1Н NMR, δ: 1.78 (t, 6 H,
3 4-CH2 of adamantane, J = 2.8 Hz); 2.17 (d, 6 H, 3 2-СН2 of
adamantane, J = 3.2 Hz); 2.29 (s, 3 H, 3 3-СН of adamantane);
4.01 (s, 3 Н, CH3); 7.45 (t, 1 H, СН of imidazole, J = 1.8 Hz);
7.49 (t, 1 H, СН of imidazole, J = 2.0 Hz); 8.99 (s, 1 Н, 2-СН
of imidazole). 13С NMR, δ: 28.9; 34.8; 35.91; 42.0; 59.9; 118.2;
123.3; 133.7.
1-Adamantyl-3-methyl-1Н-imidazolium iodide (1а)43. To
a solution of 1-adamantyl-1Н-imidazolium (607 mg, 3 mmol)
in toluene (30 mL) iodomethane (0.37 mL, 6 mmol) was added,
and the reaction mixture was stirred for 1 day. The precipitate
was filtered off and washed with cold ethyl acetate. Yield 1.032 g
(95%), grey powder. 1Н NMR, δ: 1.80 (t, 6 H, 3 4-СH2 of ada-
mantane, J = 3.2 Hz); 2.25 (d, 6 H, 3 2-СH2 of adamantane,
J = 3.2 Hz); 2.33 (s, 3 H, 3 3-СН of adamantane); 4.21 (s, 3 Н,
Me); 7.47 (t, 1 H, СН of imidazole, J = 1.8 Hz); 7.50 (t, 1 Н,
СН of imidazole, J = 1.8 Hz); 10.11 (td, 1 Н, 2-СН of imidazole,
J1 = 1.6 Hz, J2 = 0.4 Hz). 13C NMR, δ: 28.9; 34.8; 36.8; 42.5;
60.4; 117.8; 123.0; 135.0.
Synthesis of compounds 1b,c (general procedure). A solution
of 1-adamantylimidazole (0.45 g, 2.25 mmol) and arylhalide
(2.25 mmol) in acetonitrile (5 mL) was heated under reflux for
4 h. Then, the solvent was distilled off. The solid residue was
washed with a small amount of ethyl acetate and dried.
1-Adamantyl-3-(1-naphtylmethyl)-1Н-imidazolium chloride
monohydrate (1b). Yield 0.488 g (57%), white powder, m.p.
166—168 С (EtOAc). Found (%): C, 73.16; H, 7.00; N, 6.87.
C24H27ClN2•H2O. Calculated (%): C, 72.62; H, 7.36; N, 7.06.
IR (suspension in paraffin oil), ν/cm–1: 3391; 3046; 2915; 2854;
2464; 1598; 1545; 1513; 1451; 1360; 1308; 1253; 1152; 1104;
1053; 810; 785; 751; 660. 1Н NMR, δ: 1.70 (s, 6 H, 3 4-СН2 of
1-Adamantyl-3-(1-naphthylmethyl)-1Н-imidazolium tetra-
fluoroborate monohydrate (2b). Yield 0.817 g (81%), colorless
crystals, m.p. 220—221 С. Found (%): C, 64.42; H, 5.96;
N, 6.27. C24H27BF4N2•Н2О. Calculated (%): C, 64.30; H, 6.52;
N, 6.25. И IR (suspension in paraffin oil), ν/cm–1: 1552; 1423;
1
1364; 1172; 1149; 1067; 1053; 815; 794; 786; 616. Н NMR, δ:
1.67 (s, 6 H, 3 4-СН2 of adamantane); 2.07 (s, 6 Н, 3 2-СН2 of
adamantane); 2.17 (s, 3 Н, 3-СН of adamantane); 5.83 (s, 2 Н,
СН2); 7.07 (s, 1 H, СН of imidazole); 7.30 (s, 1 H, СН of imid-
azole); 7.40—7.48 (m, 2 H, 2 3,6-СН of naphthalene); 7.53
(t, 1 H, 7-СН of naphthalene, J = 7.2 Hz); 7.58 (d, 1 H, 2-СН
of naphthalene, J = 7.2 Hz); 7.83 (d, 1 H, 4-СН of naphthalene,
J = 6.8 Hz); 7.85 (d, 1 H, 2-СН of naphthalene, J = 7.2 Hz);
7.97 (d, 1 H, 8-СН of naphthalene, J = 8.4 Hz); 9.04 (s, 1 Н,

2044 Russ. Chem. Bull., Int. Ed., Vol. 68, No. 11, November, 2019
Denisov et al.
2-СН of imidazole). 13С NMR, δ: 29.4; 35.2; 42.3; 50.9; 60.6;
118.4; 121.9; 122.5, 125.6; 126.5; 127.8; 128.3; 129.0; 129.4;
130.5; 131.1; 133,6; 133.9.
naphthalene, J = 5.7 Hz); 7.78 (br.s, 1 H, 4-СН of pyridine);
7.88 (dd, 1 Н, 4-СН of naphthalene, J1 = 7.2 Hz, J2 = 1.8 Hz);
7.91 (d, 1 Н, 5-СН of naphthalene, J = 7.5 Hz); 8.28 (d, 1 H,
8-СН of naphthalene, J = 7.5 Hz); 9.04 (br.s, 2 H, 2 2,6-СН of
pyridine). 13С NMR, δ: 29.6; 35.5; 37.7; 42.2; 43.9; 118.3; 119.5;
123.9; 124.0; 124.2; 124.4; 125.7; 126.8; 128.9; 129.3; 130.6;
127.4; 138.0; 148.7; 149.0; 151.0.
1-Adamantyl-3-(diphenylmethyl)-1Н-imidazolium tetrafluoro-
borate (2с). Yield 0.739 g (73%), small colorless needle-shaped
crystals, m.p. 197—198 С. Found (%): C, 68.32; H, 5.90;
N, 5.53. C26H29BF4N2. Calculated (%): C, 68.43; H, 6.41;
N, 6.14. IR (suspension in paraffin oil), ν/cm–1: 3163; 3141;
3103; 3065; 3054; 3035; 1562; 1546; 1494; 1365; 1347; 1313;
1287; 1260; 1191; 1154; 1115; 1065; 1047; 1033; 927; 855; 755;
698; 658; 648. 1Н NMR, δ: 1.76 (t, 6 H, 3 4-СН2 of adamantane,
J = 3.0 Hz); 2.18 (t, 6 H, 3 2-СН2 of adamantane, J = 3.2 Hz);
2.28 (br.s, 3 H, 3 3-СН of adamantane); 7.13 (t, 1 H, СН of
imidazole, J = 2.0 Hz); 7.22—7.27 (m, 4 H, 4 m-СНAr); 7.28
(br.s, 1 H, CH); 7.33—7.42 (m, 6 H, 6 o,p-СНAr); 7.57 (t, 1 H,
СН of imidazole, J = 1.8 Hz); 9.03 (t, 1 H, 2-СН of imidazole,
J = 1.6 Hz). 13С NMR, δ: 29.0; 34.7; 41.9; 60.5; 66.4; 118.4;
121.0; 127.8; 128.7; 128.8; 133.7; 136.2.
trans-Dichloro(1-adamantyl-3-(diphenylmethyl)imidazol-2-
yliden)(pyridin)palladium(II) (3с). To a solution of palladium(II)
chloride (127 mg, 0.72 mmol) in boiling pyridine (5 mL) cooled
to 80 C, compound 2c (329 mg, 0.72 mmol), and then potas-
sium carbonate (279 mg, 2.15 mmol) were added. The reaction
mixture was stirred for 5 h at 80 С. Pyridine was evaporated in
vacuo, the bottom residue was washed with water and recrystal-
lized from acetonitrile. Yield 0.165 mg (34%), yellow crystals,
m.p. 208—210 С (MeСN). Found (%): C, 59.85; H, 4.82;
N, 7.15. C31H33Cl2N3Pd. Calculated (%): C, 59.58; H, 5.32;
N, 6.72. IR (CHCl3), ν/cm–1: 3063; 3030; 2984; 2911; 2853; 1605;
1496; 1485; 1449; 1419; 1405; 1360; 1343; 1307; 1256; 1218;
1200; 1180; 1165; 1104; 1072; 1046; 1032; 841; 827; 813; 753;
727; 693; 666; 649. 1Н NMR, δ: 1.85 (qd, 6 Н, 3 4-СН2 of ada-
mantane, J1 = 17.2 Hz, J2 = 0.8 Hz); 2.37 (s, 3 Н, 3 3-СН of
adamantane); 2.91 (d, 6 Н, 3 2-СН2 of adamantane, J = 2.8 Hz);
6.86 (d, 1 Н, СН of imidazole, J = 2.4 Hz); 7.18 (d, 1 Н, СН of
imidazole, J = 2.4 Hz); 7.30—7.40 (m, 12 H, 10 СН Ar 2 3,5-CH
of pyridine); 7.74 (tt, 1 H, 4-СН of pyridine, J1 = 7.6 Hz,
J2 = 1.6 Hz); 8.67 (s, 1 H, CH); 8.95 (dt, 2 H, 2 2,6-СН of
pyridine, J1 = 4.8, J2 = 1.6 Hz). 13С NMR, δ: 29.6; 35.5; 43.9;
59.6; 68.6; 118.8; 119.7; 123.9; 127.5; 127.9; 127.9; 128.6; 137.2;
138.6; 147.1; 151.1.
trans-Dichloro[1-adamantyl-3-(1-naphthylmethyl)imidazol-
2-yliden](3-methylpyridin)palladium(II) polyhydrate (4b). Pal-
ladium(II) chloride (177 mg, 1 mmol), 3-methylpyridine (0.178 mL,
2 mmol), imidazolium salt 2b (379 mg, 1 mmol), and potassium
carbonate (415 mg, 3 mmol) were suspended in acetonitrile
(10 mL). The reaction mixture was stirred for 50 min at 65 С.
The solvent was distilled off in vacuo. The bottom residue was
dissolven in dichloromethane (25 mL), the resulting suspension
was washed with saturated NaCl solution (50 mL). Organic
layer was separated, dried over MgSO4, and purified by column
chromatography on silica gel, eluting with dichloromethane.
Dichloromethane was evaporated to a final volume of 10 mL,
and the product was precipitated with petroleum ether. Yield
509 mg (77%), yellow powder, m.p. 139—140 С. Found (%):
C, 54.64; H, 5.09; N, 5.54. C30H33Cl2N3Pd•2.5Н2О. Calculat-
ed (%): C, 54.76; H, 5.82; N, 6.39. IR (CHCl3), ν/cm–1: 3140;
3106; 2985; 2910; 2853; 1608; 1599; 1583; 1512; 1483; 1454;
1422; 1398; 1373; 1360; 1339; 1325; 1306; 1256; 1242; 1213;
1198; 1172; 1130; 1106; 1063; 1030; 829; 809; 793; 785; 755;
722; 699; 688; 666; 544; 419. 1Н NMR, δ: 1.82 (q, 6 H, 3 4-СН2
of adamantane, J = 10.6 Hz); 2.34 (br.s, 6 Н, 3-СН3 of picoline
+ 3 3-СН of adamantane); 2.84 (s, 6Н, 3 2-СН2 of adamantane);
6.34 (s, 1 H, СН of imidazole); 6.53 (s, 2 Н, CH2); 6.95 (s, 1 H,
СН of imidazole); 7.21 (t, 1 H, 5-СН of pyridine, J = 6.4 Hz);
7.45—7.55 (m, 4 H, 3 3,6,7-СН of naphthalene + 4-СН of
pyridine); 7.62 (d, 1 Н, 2-СН of naphthalene, J = 7.2 Hz); 7.88
(t, 2 H, 4,5-СН of naphthalene, J = 8.2 Hz); 8.28 (d, 1 H, 8-СН
of naphthalene, J = 8.4 Hz); 8.83 (br.s, 2 H, 2 2,6-СН of pyrid-
ine). 13С NMR, δ: 18.4; 30.0; 35.9; 44.4; 54.2; 59.7; 118.7; 119.9;
123.9; 124.5; 125.3; 126.2; 127.3; 128.5; 129.4; 129.7; 130.1;
131.9; 133.9; 134.4; 138.4; 145.8; 148.7; 151.5.
trans-Dichloro(1-adamantyl-3-methylimidazol-2-yliden)(pyr-
idin)palladium(II) semihydrate (3а). Palladium(II) chloride (177 mg,
1 mmol), compound 2а (304 mg, 1 mmol), and potassium carb-
onate (415 mg, 3 mmol) were suspended in pyridine (10 mL).
The reaction mass was stirred for 5 h at 65 С. Pyridine was
evaporated in vacuo. Bottom residue was dissolved in dichloro-
methane (25 mL), washed with saturated NaCl solution (50 mL),
and dried over MgSO4. The product was isolated by column
chromatography on silica gel (dichloromethane—methanol,
9 : 1), and crystallized from acetonitrile. Yield 0.244 g (51%),
yellow crystals, m.p. 248—249 С (MeCN). Found (%): C, 47.43,
H, 5.21, N, 8.33. C19H25Cl2N3Pd•0.5Н2О. Calculated (%):
C, 47.37; H, 5.44; N, 8.72. IR (CHCl3), ν/cm–1: 3134; 3097;
3070; 2977; 2909; 2854; 1606; 1487; 1449; 1402; 1361; 1346;
1306; 1260; 1238; 1208; 1181; 1105; 1079; 1047; 1019; 830; 756;
1
731; 709; 691; 665. Н NMR, δ: 1.81 (q, 6 H, 3 4-СН2 of ada-
mantane, J = 9.8 Hz); 2.32 (s, 3 H, 3 3-СН of adamantane);
2.81 (d, 6 H, 3 2-СН2 of adamantane, J = 2.4 Hz); 4.32 (s, 3 H,
СН3); 6.91 (d, 1 Н, СН of imidazole, J = 2.0 Hz); 7.11 (d, 1 H,
СН of imidazole, J = 2.4 Hz); 7.32 (t, 2 H, 2 3,5-СН of pyridine,
J = 6.8 Hz); 7.73 (t, 1 H, 4-СН of pyridine, J = 7.6 Hz);
9.00 (d, 2 H, 2 2,6-СН of pyridine, J = 4.8 Hz). 13С NMR,
δ: 30.1; 36.0; 39.3; 44.52; 59.8; 119.0; 122.2; 124.4; 137.8;
151.5; 153.3.
trans-Dichloro(1-adamantyl-3-(1-naphthylmethyl)imidazol-
2-yliden)(pyridin)palladium(II) (3b). A solution of palladium(II)
chloride (127 mg, 0.72 mmol) in boiling pyridine (5 mL) was
cooled to 80 C, and compound 1b (273 mg, 0.72 mmol), and
then potassium carbonate (279 mg, 2.15 mmol) were added
thereto. The reaction mixture was stirred for 5 h at 80 С. Pyridine
was evaporated in vacuo, the bottom residue was dissolved in
THF (200 mL), and passed through the layer of silica gel. Yield
272 mg (63%), yellow powder, m.p. 145—149 С. Found (%):
C, 58.31; H, 5.26; N, 6.47. C29H31Cl2N3Pd. Calculated (%):
C, 58.16; H, 5.22; N, 7.02. IR (suspension in paraffin oil),
ν/cm–1: 3047; 2983; 2908; 2852; 1604; 1566; 1511; 1448; 1422;
1397; 1359; 1306; 1216; 1172; 1104; 1071; 808; 792; 783; 756;
688; 665. 1Н NMR, δ: 1.77—1.90 (m, 6 H, 3 4-СН2 of adaman-
tane); 2.35 (s, 3 H, 3 3-СН of adamantane); 2.85 (br.s, 6 H,
3 2-СН2 of adamantane); 6.36 (d, 1 Н, СН of imidazole,
J = 2.1 Hz); 6.53 (s, 2 Н, CH2); 6.97 (d, 1 H, СН of imidazole,
J = 2.1 Hz); 7.33 (m, 2 H, 2 3,5-СН of pyridine); 7.47—7.55
(m, 3 Н, 3 3,6,7-СН of naphthalene); 7.63 (d, 1 Н, 2-СН of

Thiophene and imidazole arylation
Russ. Chem. Bull., Int. Ed., Vol. 68, No. 11, November, 2019
2045
trans-Dichloro[1-adamantyl-3-(diphenylmethyl)imidazol-2-
yliden](3-methylpyridin)palladium(II) semihydrate (4c). Palla-
dium(II) chloride (181 mg, 1.02 mmol), 3-methylpyridine
(0.199 mL, 2.04 mmol), salt 2c (466 mg, 1.02 mmol), and potas-
sium carbonate (423 mg, 3.06 mmol) were suspended in aceto-
nitrile (10 mL). The reaction mixture was stirred for 5 h at 65 С;
the solvent was evaporated in vacuo. The bottom residue was
dissolved in dichloromethane (25 mL), washed with saturated
NaCl solution (50 mL), and dried over MgSO4. Complex was
purified by column chromatography on silica gel, eluting with
dichloromethane. The product was precipitated with petroleum
ether. Yield 171 mg (27%), yellow powder, m.p. 164—165 С.
Found (%): C, 59.35; H, 5.36; N, 5.72. C32H35Cl2N3Pd•0.5Н2О.
adamantane); 2.33 (dt, 3 H, 3 3-СН of adamantane, J1 = 4.8 Hz,
J2 = 2.4 Hz); 2.35 (s, 3 Н, СН3); 2.84 (d, 6 H, 3 2-СН2 of ada-
mantane, J = 2.4 Hz); 6.34 (d, 1 H, СН of imidazole, J = 2.0 Hz);
6.52 (s, 2 Н, CH2); 6.95 (d, 1 H, СН of imidazole, J = 2.0 Hz);
7.13 (dd, 2 H, 2 3,5-СН of pyridine, J1 = 6.0 Hz, J2 = 1.5 Hz);
7.45—7.55 (m, 3 H, 3 3,6,7-СН of naphthalene); 7.61 (dd, 1 H,
2-СН of naphthalene, J1 = 6.4 Hz, J2 = 0.9 Hz); 7.87 (dd, 1 H,
4-СН of naphthalene, J1 = 8.0 Hz, J2 = 1.6 Hz); 7.89 (d, 1 H,
5-СН of naphthalene, J = 8.0 Hz); 8.28 (dd, 1 H, 8-СН of
naphthalene, J1 = 8.4 Hz, J2 = 1.2 Hz); 8.86 (dd, 2 H, 2 2,6-СН
of pyridine, J1 = 5.2 Hz, J2 = 1.6 Hz). 13С NMR, δ: 21.0;
30.0; 35.9; 44.4; 54.2; 59.7; 118.7; 119.9; 124.5; 125.3; 125.3;
126.2; 127.2; 128.5; 129.4; 129.7; 130.1; 131.9; 133.9; 145.9;
149.8; 150.8.
Calculated (%): C, 59.31; H, 5.60; N, 6.48. IR (CHCl3), ν/cm–1
:
3063; 3031; 2948; 2910; 2853; 1496; 1483; 1453; 1419; 1405;
1360; 1343; 1307; 1255; 1200; 1180; 1165; 1130; 1105; 1032; 841;
827; 794; 752; 727; 696; 665; 649. 1Н NMR, δ: 1.81 (qd, 6Н,
3 4-СН2 of adamantane, J1 = 10.7 Hz, J2 = 1.2 Hz); 2.31—2.35
(m, 6 H, CH3 of picoline + 3 3-СН of adamantane); 2.40 (d, 6 Н,
3 2-СН2 of adamantane, J = 2.4 Hz); 6.81 (d, 1 Н, СН of imid-
azole, J = 2.0 Hz); 7.13 (d, 1 Н, СН of imidazole, J = 2.0 Hz);
7.16 (dd, 1 H, 5-СН of picoline, J1 = 7.6 Hz, J2 = 5.6 Hz);
7.29—7.38 (m, 10 H, Ph); 7.49 (d of heptetes, 1 H, 4-СН of
picoline, J1 = 7.6 Hz, J2 = 0.4 Hz); 8.63 (s, 1 Н, СНPh2);
8.68—8.71 (m, 2 H, 2 2,6-СН of picoline). 13С NMR, δ: 18.4;
30.1; 36.0; 44.4; 60.1; 69.1; 119.1; 120.1; 123.8; 127.9; 128.4;
129.1; 134.3; 138.3; 139.21; 148.0; 148.7; 151.6.
trans-Dichloro[1-adamantyl-3-(diphenylmethyl)imidazol-2-
yliden](4-methylpyridin)palladium(II) (5c). To a solution of pal-
ladium(II) chloride (0.72 mmol) in boiling acetonitrile (5 mL)
cooled to 80 C, 4-methylpyridine (3 mmol) and compound 2c
(273 mg, 0.72 mmol) were added, followed by potassium
carbonate (279 mg, 2.15 mmol). The reaction mixture was stirred
for 5 h at 80 С. Then, the solvent was distilled in vacuo.
The bottom residue was washed with water. The product was
purified by recrystallization from acetonitrile. Yield 0.210 mg
(46%), yellow crystals, m.p. 140—141 С (MeCN). Found (%):
C, 60.22; H, 5.08; N, 7.14. C32H35Cl2N3Pd. Calculated (%):
C, 60.15; H, 5.52; N, 6.58. IR (CHCl3), ν/cm–1: 3063; 3031;
2983; 2910; 2853; 1619; 1497; 1451; 1419; 1406; 1360; 1341;
1307; 1255; 1231; 1212; 1200; 1179; 1165; 1104; 1073; 1033; 842;
812; 752; 728; 694; 666; 649. 1Н NMR, δ: 1.77 (td, 6 Н, 3 4-СН2
of adamantane, J1 = 9.3 Hz, J2 = 2.4 Hz); 2.28 (s, 3 H, CH3);
2.37 (s, 3 Н, 3 3-СН of adamantane); 2.80 (d, 6 Н, 3 2-СН2 of
adamantane, J = 1.6 Hz); 7.29 (d, 1 Н, СН of imidazole,
J = 2.4 Hz); 7.30—7.40 (m, 12 H, 10 СНAr + 2 3,5-СН of
pyridine); 7.66 (d, 1 Н, СН of imidazole, J = 2.4 Hz); 8.55
(s, 1 H, СН); 8.65 (d, 2 H, 2 2,6-СН of pyridine, J = 6.0 Hz).
13С NMR, δ: 20.5; 29.5; 35.4; 43.5; 59.2; 68.6; 120.2; 121.0;
125.5; 127.8; 128.3; 128.8; 139.1; 147.2; 150.2 150.4.
trans-Dichloro[1-adamantyl-3-methylimidazol-2-yliden]-
(4-methylpyridin)palladium(II) (5а) was obtained similarly to complex
4с from palladium(II) chloride (177 mg, 1 mmol), 4-methyl-
pyridine (0.187 mL, 2 mmol), compound 2а (304 mg, 1 mmol),
and potassium carbonate (415 mg, 3 mmol). Yield 0.202 g (41%),
yellow powder, m.p. 244—258 С (decomp.). Found (%): C, 48.11;
H, 5.33; N, 7.85. C20H27Cl2N3Pd•0.5Н2О. Calculated (%):
C, 48.45; H, 5.69; N, 8.48. IR (CHCl3), ν/cm–1: 3136; 3106;
2983; 2910; 2853; 1619; 1503; 1454; 1404; 1360; 1347; 1326;
1307; 1259; 1230; 1208; 1180; 1105; 1070; 1035; 830; 811; 754;
1
711; 687; 665; 501; 492. Н NMR, δ: 1.80 (q, 6 H, 3 4-СН2 of
2,3,5-Triphenylthiophene (6)44. To DMA (6 mL), 2,3-di-
phenylthiophene (236.3 mg, 1 mmol), iodobenzene (0.11 mL,
2 mmol), Cs2CO3 (815 mg, 2.5 mmol), pivalic acid (31 mg,
30 mol.%), and precatalyst (2 mol.%) were added. The suspen-
sion was heated under reflux for 3 h. Then, to the suspension
cooled to ~20 C, phenanthrene (31.2 mg) was added as an
internal standard. An aliquot (0.2 mL) was adjusted with CH2Cl2
to a volume of 2 mL, and filtered. GC-MS analysis was performed.
The reaction mixture was extracted with ethyl acetate (2Ѕ25 mL),
washed with saturated NaCl solution, and dried over MgSO4.
The products were purified by column chromatography on silica
gel (eluent was petroleum ether, 40—70 С), and then recrystal-
lized from ethanol. To calibrate GC-MS for quantitative analy-
sis, solvents were used prepared from quantities of 2,3-diphenyl-
thiophene, 2,3,5-triphenylthiophene (6), and phenanthrene.
2,3,5-Triphenylthiophene (6) is a yellow powder, m.p. 106—107 C
(EtOH). 1Н NMR, δ: 7.34—7.18 (m, 14 H, Ar); 7.58 (d, 2 H,
Ar, J = 7.6 Hz). MS, m/z (Irel (%)): 313 [M + 1]+ (26), 312
[М]+ (100), 311 [M – H]+ (13), 278 [M – H2S]+ (12), 121
[C7H5S]+ (10).
adamantane, J = 10.0 Hz); 2.31 (t, 3 H, 3 3-СН of adamantane,
J = 8.8 Hz); 2.35 (s, 3 H, СН3); 2.80 (s, 6 H, 3 2-СН2 of ada-
mantane); 4.31 (s, 3 H, СН3 of picoline); 6.90 (d, 1 H, СН of
imidazole, J = 1.6 Hz); 7.09—7.13 (m, 3 H, СН of imidazole
2 3,5-СН of pyridine); 8.81 (d, 2 H, 2 2,6-СН of pyridine,
J = 6.0 Hz). 13С NMR, δ: 20.9; 30.1; 36.0; 39.2; 44.5; 59.7;
118.9; 122.1; 125.2; 149.7; 150.8; 152.6.
trans-Dichloro[1-adamantyl-3-(1-naphthylmethyl)imidazol-
2-yliden](4-methylpyridin)palladium(II) (5b). To a solution of
palladium(II) chloride (0.72 mmol) in boiling acetonitrile (5 mL)
cooled to 80 C, and 4-methylpyridine (3 mmol), compound 1b
(273 mg, 0.72 mmol) were added, followed by potassium carbon-
ate (279 mg, 2.15 mmol). The reaction mixture was stirred
for 5 h at 80 С. Then, the solvent was distilled in vacuo. The
bottom residue was dissolved in THF (200 mL) and passed
through silica gel. The solvent was distilled off. The product was
purified by recrystallization from acetone. Yield 0.182 g (39%),
yellow powder, m.p. 118—120 С (acetone). Found (%): C, 57.57;
H, 5.47; N, 6.86. C30H33Cl2N3Pd. Calculated (%): C, 58.79;
H, 5.43; N, 6.86. IR (CHCl3), ν/cm–1: 3069; 3046; 2982; 2909;
2852; 1618; 1597; 1582; 1511; 1502; 1448; 1423; 1397; 1306;
1255; 1211; 1195; 1172; 1070; 1033; 994; 792; 783; 753; 722;
687; 665; 634. 1Н NMR, δ: 1.76—1.88 (m, 6 H, 3 4-СН2 of
4-(1-Methyl-1Н-imidazo-5-yl)benzonitrile (7)45,35. To DMA
(4 mL), p-bromobenzonitrile (182.0 mg, 1 mmol), 1-methyl-
imidazole (0.16 mL, 2 mmol), K2CO3 (276 mg, 2 mmol), piv-
alic acid (31 mg, 30 mol.%), and precatalyst 3a—d (0.5 mol.%)

2046 Russ. Chem. Bull., Int. Ed., Vol. 68, No. 11, November, 2019
Denisov et al.
Table 3. Selected crystallographic parameters and results of refinement of structures 3a, 5c, and 7
Parameter
3a
5c
7
Molecular formula
C
19H25Cl2N3Pd
472.72
2(C32H35Cl2N3Pd)•C2H3N
C11H9N3
183.21
М
1318.91
295(2)
T/K
System
295(2)
295(2)
Monoclinic
P21/c
14.347(2)
14.2736(16)
10.4159(15)
90.00
Triclinic
Monoclinic
P21/c
13.666(4)
7.272(2)
9.965(3)
90.00
–
Space group
P1
12.2467(8)
16.1196(9)
16.7547(11)
97.363(5)
a/Å
b/Å
c/Å
α/deg
β/deg
110.905(16)
90.00
107.521(6)
97.375(5)
107.91(4)
90.00
γ/deg
V/Å3
1992.6(5)
4
3079.0(3)
942.3(5)
Z
2
4
dcalc/g cm–3
1.576
1.423
1.291
μ/mm–1
1.206
0.804
0.081
F(000)
960
1356
384
Crystal size/mm
Scattering angles, 2θ/deg
Indices of refraction
0.550.300.14
6.46 < 2θ < 58.57
–19 ≤ h ≤ 13,
–18 ≤ k ≤ 13,
–11 ≤ l ≤ 13
11578
4677 (Rint = 0.0304)
4677/238/318
1.063
0.580.310.26
4.38 < 2θ < 58.69
–13 ≤ h ≤ 16,
–21 ≤ k ≤ 20,
–22 ≤ l ≤ 22
27041
14217 (Rint = 0.0288)
14217/0/715
1.061
0.600.350.24
6.42 < 2θ < 58.92
–18 ≤ h ≤ 17,
–6 ≤ k ≤ 9,
–13 ≤ l ≤ 13
4402
2213 (Rint = 0.0293)
2213/0/129
1.035
Number of reflection collected
Number of independent reflections
Number of data/restrictions/parameters
Goodness-of-fit on F2
R-factors [I  2σ (I)]
R1 = 0.0503,
wR2 = 0.1413
R1 = 0.0614,
wR2 = 0.1509
1.55/–0.83
R1 = 0.0370,
wR2 = 0.0894
R1 = 0.0506,
wR2 = 0.0988
0.742/–0.864
R1 = 0.0522,
wR2 = 0.1252
R1 = 0.0732,
wR2 = 0.1436
0.204/–0.164
R-factors (all reflections)
Residual electron density/e Å–3, ρmax/ρmin
were added. The suspension was stirred for 10 h at 110 or 130 С.
Then, to the suspension cooled to ~20 C, phenanthrene
(18.3 mg) was added as an internal standard. An aliquot (0.2 mL)
was adjusted with CH2Cl2 to a volume of 2 mL, filtered and
analyzed by GC-MS technique. The reaction mixture was ex-
tracted with CH2Cl2 (2Ѕ25 mL), washed with saturated NaCl
solution, and dried over MgSO4. The products were purified by
column chromatography on silica gel, eluting first with dichloro-
methane, and then with a CH2Cl2—MeOH (15 : 1, v/v) mixture.
Compound 7 is yellow-brown crystals, m.p. 131—132 С (CH2Cl2).
To calibrate GC-MS for quantitative analysis, solvents were used
prepared from quantities of p-bromobenzonitrile, 4-(1-methyl-
1Н-imidazo-5-yl)benzonitrile, and phenanthrene. 1Н NMR, δ:
3.77 (s, 3 Н, СН3); 7.21 (s, 1 Н, 4-Н of imidazole); 7.51 (dt, 2 Н,
Ar, J1 = 8.4, J2 = 1.4 Hz); 7.58 (s, 1 Н, 2-Н of imidazole); 7.71
(dt, 2 Н, Ar, J1 = 8.4 Hz, J2 = 1.4 Hz). MS, m/z (Irel (%)): 184
[M + 1]+ (14), 183 [М]+ (100), 155 [M – CH2N]+ (13), 128
[M – C2H3N2]+ (12), 114 [M – C3H5N2]+ (10).
of 1). Empirical absorption corrections were introduced.
Structures were solved using SHELXS (see Ref. 46) and refined
by full-matrix least-squares calculations against F2 in anisotropic
approximation for all non-hydrogen atoms using SHELXL (see
Ref. 47) software with graphical interface OLEX2.48 Hydrogen
atoms were placed to calculated positions and refined using
a riding model. Main crystallopraphic parameters and results of
structure refinement of structures 3а and 5с are summarized in
Table 3. Structure of salt 2а was also confirmed by the X-ray
diffraction analysis, however due to the strong disordering of an
anion it was not possible to achieve acceptable divergence factors.
The X-ray crystallographic data were deposited with the
Cambridge Crystallographic Data Centre as a cif file with num-
bers CCDC 1910036 (complex 3а) and 1910037 (complex 5с).
The structure of compound 7 has been deposited earlier and had
the deposition number CCDC 1837277. These data are free
available and can be requested at www.ccdc.cam.ac.uk.
Structural studies. Crystals of salt 2a were obtained by re-
crystallization from ethanol—water mixture; crystals of com-
plexes 3a and 5с were grown by a slow evaporation of their solu-
tions in MeCN. X-ray diffraction analysis of salt 2a as well as
complexes 3а and 5с was performed on a Xcalibur Ruby dif-
fractometer according to a standard procedure (Mo-Kα-radiation,
graphite monochromator, ω-scanning with an incremental step
Analytical, spectroscopic, and biological studies were
performed at the "Research of Materials and Substances"
Center of Collective Use of the Perm Federal Reseach Center
of the Ural Branch of the Russian Academy of Sciences.
The authors also express their gratitude to I. А. Bori-
sova for registration of IR spectra, to О. А. Maiorova for

Thiophene and imidazole arylation
Russ. Chem. Bull., Int. Ed., Vol. 68, No. 11, November, 2019
2047
recording 1Н and 13С NMR spectra, and to А. V. Khari-
tonova for performing elemental analysis.
The work was financially supported by the Russian
Foundation for Basic Research (Project No. 17-03-00456-a).
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Received April 17, 2019;
in revised form June 21, 2019;
accepted August 5, 2019