Complexes of palladium(II) and platinum(II) with 6-tert-butyl-2-thiouracil

Article abstract of DOI:10.1134/S1070363217010182

cis-Dihalogeno complexes of platinum(II) and palladium(II) with 6-tert-butyl-2-thiouracil have been synthesized. The mode of coordination of the ligand to metal ions was established by IR and NMR spectroscopy.

Full text of DOI:10.1134/S1070363217010182

ISSN 1070-3632, Russian Journal of General Chemistry, 2017, Vol. 87, No. 1, pp. 117–121. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © L.G. Golubyatnikova, R.А. Khisamutdinov, S.А. Grabovskii, N.N. Kabal’nova, Yu.I. Murinov, 2017, published in Zhurnal Obshchei
Khimii, 2017, Vol. 87, No. 1, pp. 123–127.
Complexes of Palladium(II) and Platinum(II)
with 6-tert-Butyl-2-thiouracil
L. G. Golubyatnikova*, R. А. Khisamutdinov,
S. А. Grabovskii, N. N. Kabal’nova, and Yu. I. Murinov
Ufa Institute of Chemistry, Russian Academy of Sciences, pr. Oktyabrya 71, Ufa, 450054 Russia
*
e-mail: hisam@anrb.ru
Received June 27, 2016
Abstract—cis-Dihalogeno complexes of platinum(II) and palladium(II) with 6-tert-butyl-2-thiouracil have
been synthesized. The mode of coordination of the ligand to metal ions was established by IR and NMR
spectroscopy.
Keywords: platinum(II), palladium(II), halogeno complexes, 6-tert-butyl-2-thiouracil
DOI: 10.1134/S1070363217010182
The interest to complexes of platinum and palla-
dium is due to their high cytostatic activity. The search
for new antitumor drugs, less toxic and more effective
than cis-dichlorodiaminoplatinum, based on the Pt(II)
and Pd(II) complex compounds is a state-of-the-art
problem. The synthesis and investigation of complexes
of platinum and palladium in which the ligands are
represented by biologically active compounds seems to
be the main direction of this search. One of the most
promising compounds for this purpose, in our opinion,
are thiouracils possessing high biological activity [1].
Some of thiouracil derivatives are widely used in
medical practice [2], and the complexes with noble
metals are promising as cancerostatics [3].
Scheme 1.
O
O
N
N
H H
N
CH3
C
CH3
C
S
S
CH3
H C
N
3
M
CH3
CH3
H Hlg
Hlg H
ligand substitution of acetonitrile or benzonitrile by the
molecules of ligand L at room temperature. The pro-
ducts are colored powders, insoluble in water, readily
soluble in DMSO and moderately, in chloroform,
ethanol, acetone, diethyl ether. The complexes, except
[
3
PtCl L ] (1), do not melt or decompose on heating to
2
2
To date numerous metal complexes of thiouracil
derivatives have been synthesized and their composi-
tion and structure with various metals like copper, iron,
cobalt, nickel, manganese, cadmium, vanadium [3–5],
as well as palladium, platinum and gold was studied
00°С.
The results of elemental analysis and some physico-
chemical properties of the ligand and its halogeno-
complexes with Pt(II) and Pd(II) are given in Table 1.
As can be seen from these data, the ratio Pd(Pt) : L in
the obtained complexes is equal to the ratio of the
[6]. However, the described chlorocomplexes of Pt(II)
and Pd(II) with thiouracil derivatives have trans-con-
figuration [7], while chlorocomplexes of cis-configura-
tion were not reported until now.
1
3
taken reagents. The data of С NMR spectra of ligand
L and its complexes with Pd(II) are presented in Table 2.
The goal of the present study is the synthesis of cis-
dichlorocomplexes of Pt(II) and Pd(II) with 6-tert-
butyl-2-thiouracil and the investigation of their structure
IR spectra of 6-tert-butyl-2-thiouracil, the pre-
cursors and halogenocomplexes are presented in Table 3.
Full assignment of the IR absorption bands of 2-thio-
uracil is given in [8]. The spectrum contains strong
(
Scheme 1).
–
1
Pt(II) and Pd(II) complexes with 6-tert-butyl-2-
thiouracil (L) were synthesized using the method of
bands in the range 3224–3029 cm belonging to
1
3
ν(N H) and ν(N H) stretching vibrations. A strong
1
17

1
18
GOLUBYATNIKOVA et al.
Table 1. Elemental composition of 6-tert-butyl-2-thiouracil and its complexes
Found, %
Comp.
Calculated, %
М : L
Formula
OS
no.
С
H
S
N
М
Hlg
С
H
S
N
М
Hlg
L
1
2
3
52.6 6.6 17.3 15.1
С
8
Н
12
N
2
52.2
30.3
35.2
30.2
6.6
3.8
4.4
3.8
17.4 15.2
10.1 8.8 30.7 11.2
1:2
1:2
1:2
30.2 3.0 9.6 8.7 29.4 11.0 С16
Н
Н
Н
24Cl
24Cl
2
N
N
4
4
O
O
2
2
PtS
PdS
PdS
2
35.0 4.2 11.7 10.3 26.6 14.7 С16
30.0 3.5 10.1 8.7 19.0 27.9 С16
2
2
11.8 10.3 25.6 13.1
10.1 8.8 19.3 25.2
24Br
2
N
4
O
2
2
13
Table 2. С NMR parameters (ppm) for 6-tert-butyl-2-thiouracil and its complexes with Pd(II)
O
H
N3 4
8
5
6
CH3
2
1
S
N
H
7C CH
3
9
CH
3
10
8
10
7
2
4
5
6
Comp. no. Parameter
C –С
C
С
С
С
С
L
δ
27.77
27.23
0.54
34.94
34.68
0.26
176.95
161.63
160.34
1.29
100.98
163.80
163.03
0.77
2
δ
174.00 (br)
2.95
102.41 (br)
–1.43
Δδ
δ
3
27.23
0.54
34.65
0.29
175.09 (br)
1.86
160.42
1.21
103.12 (br)
–2.14
163.14
0.66
Δδ
–
1
–1
band at 1682 cm corresponds to stretching vibrations
region at 362 and 354 cm belonging to stretching
vibrations of the Pt–Cl bond is indicative of the forma-
tion of the cis-isomer.
4
–1
ν(C =O), the band at 1542 cm , to symmetric bending
vibrations of the N C N group of atoms. It is known
that characteristic band of the C =S bond stretching
3
2
1
2
The obtained complex Pt(II) 1 is insoluble in
solvents usually used for recording NMR spectra. It is
soluble in DMSO-d , but in the solution the resolvation
with liberation of ligand L occurs, therefore, the
–
1
vibrations appears at 1160 cm [4]. However, our
calculations of the vibrational spectrum of ligand L,
consistent with calculations of other authors [9],
suggest that this band comes from bending scissor
6
13
С
1
2
3
–1
NMR spectrum of complex 1 could not be registered.
vibrations δ(N C N ). The band at 952 cm refers to
2
complex vibrations ν(C =S) and planar bending
The absence of strong absorption band of the
ν(С≡N) stretching vibrations at 2230 cm in the
spectrum of complex 1 as compared to the spectrum of
2
1
6
–1
–1
vibrations δ(С N C ), and the band at 754 cm , to the
2
out-of-plane vibrations ν(C =S). The absence in the IR
spectrum of ligand L of the absorption bands at
its precursor PtCl (CH CN) is indicative of complete
2 3 2
–
1
2
600 cm [ν(SH)] suggests that the compound exists
substitution of acetonitrile molecules by the molecules
of the ligand. The presence of two absorption bands at
in the thione form.
–
1
3
36 and 322 cm in the IR spectrum of complex 1,
It is known that the synthesis of PtCl (СН СN) by
the method described in [10] without heating gives the
complex of the cis-configuration, and with heating to
5°С, its trans-isomer [11]. The IR spectrum of the
lacking in the spectrum of the ligand points to the
formation of chlorocomplex of Pt(II) of cis-con-
figuration. These bands, according to the literature data
for the spectra of chlorocomplexes of Pt(II) with
neutral ligands (dialkyl sulfides, derivatives of
pyridine, imidazole, benzotriazole, etc.) [12, 13], are
due to the ν(Pt–Cl) stretching vibrations in complexes
2
3
2
7
complex PtCl (СН СN) which we synthesized at room
2
3
2
temperature is similar to those described in [10]. The
presence of two strong absorption bands in the far
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 1 2017

COMPLEXES OF PALLADIUM(II) AND PLATINUM(II) WITH 6-tert-BUTYL-2-THIOURACIL
119
–
1
Table 3. Characteristic absorption bands (cm ) in the IR spectra of 6-tert-butyl-2-thiouracil and its chlorocomplexes with
Pt(II) and Pd(II)
Absorption band
L
1
2
3
1
ν(N H)
3224 v.s
3136 v.s
3180 w
3120 w
3200 sh
3121 w
3253 v.s
3100 v.s
3
ν(N H)
ν(С≡N)
4
ν(С =О)
1682 s
1622 s
1680 s
1614 s
1689 v.s
1623 s
1700 v.s
1622 s
5
6
ν(С =С )
1
615 s
3
2
1
δ(N C N ) in thioamide group
1542 s
1160 s
952 m
754 m
1544 s
1166 s
940 w
735 w
380 w
1547 s
1176 s
940 w
1550 v.s
1163 s
940 m
735 w
314
1
2
3
Scissor vibrations δ(N C N ) in thioamide group
2
2
1
6
Mixed vibrations ν(С =S) and δ(С N C )
2
Out-of-plane vibrations ν(С =S)
759 w, br
ν(Pt–S)
ν(Pd–S)
314 sh
310 sh
ν(Pt–Cl)
ν(Pd–Cl)
336 m
322 m
348 m
320 m
ν(Pd–Br)
266 s
244 m
of the cis-PtCl L type of С symmetry. A weak
[19, 20] it is stated that the compound has the cis-
2
2
2v
1
–
absorption band at 380 cm , also absent in the
spectrum of the ligand, corresponds to the ν(Pt–S)
stretching vibrations, which proves coordination of the
ligand to the metal ion via the sulfur atom of the
thioamide group [14]. As compared to the IR spectrum
of the ligand, in the spectrum of complex 1 due to the
complex formation the combined absorption band
configuration, since it shows in the IR spectrum two
–
1
absorption bands ν(Pd–Сl): 388 and 358 cm [19],
–
1
–1
367 and 325 cm [21], 334 and 315 cm [22].
Therefore, there is no unambiguous assignment of
absorption bands of the Pd–Cl stretching vibrations in
the IR spectrum of cis-(bis-benzonitrile)dichloro-
palladium(II). The IR spectrum of its precursor shows
2
2
1
6
–1
–1
ν(C =S) + δ(С N C ) at 952 cm is shifted to the far
strong absorption bands at 369 and 324 cm . These
–
1
2
–1
region by 12 cm , and the ν(C =S) band at 754 cm ,
by 19 cm .
bands can be assigned to the stretching vibrations
ν(Pd–Сl), since in the spectrum of (bis-benzonitrile)
dibromopalladium(II), which we also synthesized, they
are lacking.
–
1
As a starting reagent for the synthesis of Pd(II)
complexes, (bis-benzonitrile)dichloropalladium(II) was
employed. This compound is a classical labile complex
in which the molecules of benzonitrile are easily
replaced by the molecules of sulfur- and nitrogen-
containing organic compounds. It is widely used as a
precursor in coordination chemistry as well as in the
synthesis of organopalladium complexes. Some
researchers believe the complex to be the trans-isomer
1
3
In the С NMR spectra of Pd(II) complexes 2 and
2
4
5
3
the signals of atoms С , С , С are shifted with
respect to the spectrum of the ligand (Table 2), the
largest shift being observed for the carbon atom of the
thiocarbonyl group. The signals of all carbon atoms except
5
atom C are shifted upfield upon complex formation.
In the IR spectrum of complex 2, the nitrile group
[
15, 16] because of the presence of one strong
absorption band, which in the spectrum of the
–
1
absorption band of stretching vibrations ν(Pd–Сl)
appearing, according to different authors, at 320 cm
precursor PdCl (PhCN) appears at 2288 cm , is
2
2
–
1
lacking, thus indicating complete replacement of two
molecules of benzonitrile by the molecules of the
–
1
–1
[17], 368 cm or 338 cm [18]). In other works
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 1 2017

1
20
GOLUBYATNIKOVA et al.
ligand. The absorption bands corresponding to the
ν(N –H) and ν(N –H) vibration are shifted to the far
4,4-dimethyl-3-oxopentanoic acid and purified by
crystallization from 5% aqueous ethanol. Yield 46%,
1
3
1
region with respect to those in the spectrum of the
colorless needle crystals, mp 173°С. H NMR spectrum,
–
1
5
ligand by 15–20 cm , and the stretching and bending
δ, ppm: 1.20 s (9H, CH ), 5.62 s (1H, HC ), 11.77 s
3
4
5
6
1
3
15
1
vibrations of the tert-butyl group ν(С =О), ν(С =С ),
(1H, HN ), 12.34 s (1H, HN ). N{ H} NMR spectrum
(DMSO-d , 50 MHz), δ, ppm: 154.4 (N ), 180.4 (N ).
3
2
1
–1
1
3
δ(N C N ), and δ(СH ), to the near region by 5–7 cm .
The bending vibrations band δ(N C N ) at the thio-
3
6
1
2
3
As a precursor for the synthesis of chlorocomplex
of Pt(II) with 5-tert-butyl-2-thiouracil we used cis-bis-
amide group is also shifted to high-frequency region
–
1
2
by 16 cm , the bands of combined vibrations ν(С =S) +
(
acetonitrile)dichloroplatinum(II) PtCl (CH CN) , which
2
1
6
–1
2 3 2
δ(С N C ), to the far region by 12 cm , and the
was obtained by the known procedure [11]. Chloro-
and bromocomplex of Pd(II) were synthesized from
the preprepared (bis-benzonitrile)dichloropalladium(II)
absorption bands of the out-of-plane stretching vibra-
2
–1
tions ν(С =S) at 754 cm broadened. The absorption
–
1
bands at 348 and 320 cm can be assigned, respec-
tively, to asymmetric and symmetric stretching vibra-
tions of the ν(Pd–Cl) band (complex of the cis-PdCl2L2
type, С symmetry) [23].
PdCl (PhCN)
and (bis-benzonitrile)dichloropalla-
2
2
dium(II) PdBr (PhCN) by the known procedures [19, 26].
2
2
As solvents, acetone (analytical purity grade), hexane
pure), ethanol and chloroform (both chemically pure),
2
v
(
For unambiguous assignment of the Pd–Cl absorp-
tion band in the spectrum of complex 2 we have
synthesized its analog, PdBr L (3). The IR spectrum
acetonitrile (analytically pure), acetonitrile (special
purity) were used.
2
2
–1
of 3 in the range 4000–600 cm is similar to that of
chlorocomplex 2. In the far region of the spectrum of 3
Complex 1, cis-[PtCl
L ]. 0.15 g (0.42 mmol) of
2 2
cis-[PtCl (CH CN) ] was dissolved at stirring in
2
3
2
–
1
a strong absorption band appears at 265 cm
25 mL of dry acetone. To the obtained solution, 10 mL
of the solution of 0.1562 g (0.84 mmol) of the ligand
in acetone was added. The formed transparent yellow
solution was stirred for 2 h. To the reaction mixture
belonging to stretching vibrations ν(Pd–Br) [24].
–
1
The band at 314 cm in the spectrum of complex 2
apparently corresponds to stretching vibrations
ν(Pd–S). The whole set of the spectral data allows to
assume that the formation of complex 2 is due to
thecoordination of the ligand to Pd(II) via the sulfur
atom of the thioamide group.
2
0 mL of hexane was added for complete precipitation
of the complex. The formed yellow precipitate was
filtered off, washed with hexane (3×20 mL), and dried
at room temperature. Yield 0.28 g (97.0 %), mp 157°C.
Complex 2, cis-[PdCl L ]. 0.1438 g (0.37 mmol) of
2
2
Therefore by the reaction of the Pd(II) and Pt(II)
precursors with 6-tert-butyl-2-thiouracil we have first
prepared chlorocomplexes of the cis-configuration. The
formation of complexes was established to occur via
the coordination of the thione sulfur atoms of the thio-
uracil ring to Pd(II) and Pt(II). Neither nitrogen nor
oxygen atoms of the ligand are involved in the complex
formation.
cis-[PdCl (PhCN) ] was dissolved in 10 mL of
2
2
chloroform. To the obtained solution, 10 mL of the
ethanol solution of 0.1382 g (0.75 mmol) of the ligand
was added. After stirring for 1 h the formed bright-
orange precipitate was filtered off, washed with hexane
3×20 mL) to remove the remained benzonitrile, and
dried at room temperature. Yield 0.16 g (80.0 %).
(
Complex 3, cis-[PdBr L ]. 0.2027 g (0.43 mmol) of
2
2
EXPERIMENTAL
[
PdBr (PhCN) ] was dissolved in 10 mL of chloroform
2 2
IR spectrum was calculated by the М06-2X/MG3S
at stirring. To the obtained solution, 10 mL of the
ethanol solution of 0.1581 g (0.86 mmol) of the ligand
was added. After stirring for 3 h, dark-red precipitate
was gradually formed, which was filtered off, washed
with hexane (3×20 mL), and dried at room
temperature. Yield 0.23 g (96.0 %).
method. IR spectra were recorded on a Specord M80
–
1
spectrophotometer in the range 4000–230 cm
mineral oil, KRS-5). NMR spectra were registered on
a Bruker Avance III spectrometer with working
(
1
13
frequency 500.13 MHz ( H), 125.47 MHz ( C) and
1
5
5
0.58 MHz ( N) in DMSO-d . Melting points were
6
ACKNOWLEDGMENTS
determined on a Boetius heating device.
-tert-Butyl-2-thiouracil was obtained by the
known procedure [25] from thiourea and ethyl ester of
5
This work was financially supported by the Russian
Science Foundation (grant no. 16-15-00141) and the
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 1 2017

COMPLEXES OF PALLADIUM(II) AND PLATINUM(II) WITH 6-tert-BUTYL-2-THIOURACIL
121
Program of Department of Chemistry and Science
Materials of Russian Academy of Sciences, with the
use of equipment of the Center for Joint Usage
50532006000700011
13. Ferraro, J.R., Low-Frequency Vibrations of Inorganic
and Coordination Compounds, New York: Plenum Press,
1
971.
“
Chemistry” of Ufa Institute of Chemistry of the
1
4. Shaheen, F., Badashah, A., Gielen, M., Marchio, L.,
Russian Academy of Sciences.
de Vos, D., and Khosa, M.K., Appl. Organomet. Chem.,
2
007, vol. 21, no. 8, p. 626. doi 10/1002/aoc.1227
REFERENCES
. Tang, P. and Li, N.C., J. Inorg. Nucl. Chem., 1963,
vol. 25, p. 720. doi 10.1016/0022-1902(63)80163-3
. Ali, A. and Livingstone, S.E., Coord. Chem. Rev., 1974,
1
5. Tsvetkova, I.B., Matveeva, V.G., Doluda, V.Y., By-
kov, A.V., Sidorov, A.I., Schennikov, S.V., Sulman, M.G.,
Valetsky, P.M., Stein, B.D., Chun-Hsing, Chen,
Sulman, E.M., and Bronstein, L.M., J. Mat. Chem.,
1
2
3
2
012, vol. 22, p. 6441. doi 10.1039/C2JM30634D
vol. 13, p. 102. doi 10.1016/S0010-8545(00)80253-2
1
6. Olmstead, M.M., Wei, P., Ginwalla, A.S., and Balch, A.L.,
Inorg. Chem., 2000, vol. 39, p. 4555. doi 10.1021/
ic0000597
. Jayabharathi, J., Thanikachalam,V., Jayamoorthy, K.,
and Perumal, M.V., Spectrochim. Acta (A), 2012,
vol. 97, p. 6. doi 10.1016/j.saa.2012.05.017
. Masoud, M.S., Ibrahim, A.A., Khalil, E.A., and El-
Marghany, A., Spectrochim. Acta (A), 2007, vol. 67,
p. 662. doi 10.1016/j.saa.2006.07.046
. Masoud, M.S., Amira, M.F., Ramadan, A.M., and El-
Ashry, G.M., Spectrochim. Acta (A), 2008, vol. 69,
p. 230. doi 10.1016/j.saa.2007.03.039
. El-Morsy, F.A., Jean-Claude, B.J., Butler, I.S., El-
Sayed, S.A., and Mostafa, S.I., Inorg. Chim. Acta, 2014,
vol. 423, p. 144. doi 10.1016/j.ica.2014.07.031
1
1
1
2
7. Muhyedeen, B.R.J. and Drea, A., J. Multifunct. Mater.
4
5
6
7
8
9
&
Photosci., 2014, vol. 5, no. 1, p. 1.
8. Nawrot-Modranka, J. and Nawrot, E., Acta Poloniae
Pharm. Drug Research, 2007, vol. 63, no. 5, p. 429.
9. Szłyk, E. and Barwiołek, M., Thermochim. Acta, 2009,
vol. 495, p. 85. doi 10.1016/j.tca.2009.06.002
0. Zaghal, M.H., Bani Saeed, M.S., Hamid, A.A., and
Ali, B.F., Synth. React. Inorg. Metal-Org. Nano-Metal
Chem., 2015, vol. 45, p. 164. doi 10.1080/
1
5533174.2013.819895
. Gutiérrez, M.D., Lуpez, R., Romero, M.A., and Salas, J.M.,
Can. J. Chem., 1988, vol. 66, p. 249. doi 10.1139/v88-
2
2
2
2
1. Hughes, M.N. and Rutt, K.J., Spectrochim. Acta. (A),
1
8
971, vol. 27, no. 6, p. 924. doi 10.1016/0584-8539(71)
0171-X
0
42
. Yadav, R.A., Yadav, P.N.S., and Yadav, J.S., Proc.
Indian Acad. Sci. (Chem. Sci.), 1988, vol. 100, no. 1,
p. 69. doi 10.1007/BF02839530
. Rosy, P.J. and Kalyanasundharam, S., Intern. Lett.
Chem. Phys. Astronomy, 2015, vol. 49, p. 74. doi
2. Berg, R.W. and Rasmussen, K., Spectrochim. Acta (A),
1
8
973, vol. 29, no. 2, p. 319. doi 10.1016/0584-8539(73)
0076-5
3. Boixassa, A., Pons, J., Solans, X., Fontbardia, M., and
Ros, J., Inorg. Chim. Acta, 2004, vol. 357, no. 3, p. 827.
doi 10.1016/j.ica.2003.10.001
4. Sampathkumaran, E.V., Paulose, P.L., Grover, A.K.,
Nagarajan, V., and Dhar, S.K., Curr. Sci., 1987, vol. 56,
no. 6, p. 252.
1
0.18052/www. scipress.com/ILCPA.49.74
1
1
1
0. Weil, T., Spaulding, L., and Orchin, M., J. Coord.
Chem., 1971, vol. 1, p. 25. doi 10.1080/
0
0958977108070740
1. Fanizzi, F.P., Intini, F.P., Maresca, L., and Natile, G.,
J. Chem. Soc. Dalton Trans., 1990, no. 1, p. 199. doi
25. Anderson, G.W., Halverstadt, I.F., Miller, W.H., and
Roblin, R.O., Jr., J. Am. Chem. Soc., 1945, vol. 67,
no. 12, p. 2197. doi 10.1021/ja01228a042
1
0.1039/DT9900000199
2. de Almeida, M.V., Chaves, J.D.S., Soares Fontes, A.Р.,
Cesar, E.T., and Gielen, M., J. Braz. Chem. Soc., 2006,
vol. 17, no. 7, p. 1266. doi 10.1590/S0103-
26. Frye, H., Kuuian, E., and Viebrock, J., Z. Naturforschg.,
1965, vol. 20, p. 269.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 1 2017