Rhodium(III), palladium(II), and platinum(II) complexes with 2-(2-hydroxybenzoyl)-N-methylhydrazinecarbothioamide: Syntheses, structures, and spectral characteristics

Article abstract of DOI:10.1134/S1070328414030063

The syntheses and spectral (IR, UV-VIS, XPS, and ¹H and ¹³C NMR) characteristics of the rhodium(III), palladium(II), and platinum(II) complexes with 2-(2-hydroxybenzoyl)-N-methylhydrazinecarbothioamide (HBMHCTA) are described. The co

Full text of DOI:10.1134/S1070328414030063

ISSN 1070ꢀ3284, Russian Journal of Coordination Chemistry, 2014, Vol. 40, No. 3, pp. 160–170. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © S.I. Orysyk, V.V. Bon, O.A. Zholob, V.I. Pekhnyo, V.V. Orysyk, Yu.L. Zborovskii, M.V. Vovk, 2014, published in Koordinatsionnaya Khimiya, 2014,
Vol. 40, No. 3, pp. 160–170.
Rhodium(III), Palladium(II), and Platinum(II) Complexes
with 2ꢀ(2ꢀHydroxybenzoyl)ꢀNꢀMethylhydrazinecarbothioamide:
Syntheses, Structures, and Spectral Characteristics
S. I. Orysyka, *, V. V. Bona, O. A. Zholoba, V. I. Pekhnyoa, V. V. Orysykb,
Yu. L. Zborovskiib, and M. V. Vovkb
a Vernadsky Institute of General and Inorganic Chemistry, National Academy of Sciences of Ukraine,
pr. akademika Palladina 32/34, Kiev, Ukraine
b Institute of Organic Chemistry, National Academy of Sciences of Ukraine, ul. Murmanskaya 5, Kiev, Ukraine
*eꢀmail: orysyk@ionc.kiev.ua
Received August 4, 2013
Abstract—The syntheses and spectral (IR, UVꢀVIS, XPS, and 1H and 13C NMR) characteristics of the rhodꢀ
ium(III), palladium(II), and platinum(II) complexes with 2ꢀ(2ꢀhydroxybenzoyl)ꢀNꢀmethylhydrazinecarꢀ
bothioamide (HBMHCTA) are described. The coordination of HBMHCTA to the central metal ion and its
intraligand rearrangement in the complex formation of rhodium(III) ions are studied. The structure of the
mixedꢀligand complex [Pd(H2L)PPh3] is determined by Xꢀray diffraction analysis.
DOI: 10.1134/S1070328414030063
INTRODUCTION
HBMHCTA with Rh3+, Pd2+, and Pt2+ ions, which
differ in electronic structure and coordination capacꢀ
ity, is an important stage in the development of the tarꢀ
geted synthesis of practically interesting complexes
with certain composition and structure.
Thiosemicarbazides are of special interest as comꢀ
plexing agents for transition and platinum group metꢀ
als. The introduction of additional functional groups
into the structures of thiosemicarbazides increases the
number of possible coordination modes. Thiosemiꢀ
carbazides are prototropic ligand systems and, hence,
they are coordinated as certain tautomeric forms,
depending on the nature of substituents and synthesis
conditions, upon the interaction with metal ions [1–
5]. In particular, 2ꢀ(2ꢀhydroxybenzoyl)ꢀNꢀmethylhyꢀ
drazinecarbothioamide (HBMHCTA, H4L) containꢀ
EXPERIMENTAL
Commercial RhCl3
⋅ 4H2O (39.51% Rh), PdCl2
(59.0% Pd), K2[PtCl4] (43.6% Pt), and PdCl2(PPh3)2
(24.0% Pd) were used as the starting metal salts for the
syntheses of the complexes.
Synthesis of HBMHCTA (H4L). Methyl isothiocyꢀ
anate (7.67 g, 0.105 mol) was added to a suspension of
salicylic acid hydrazide (15.21 g, 0.1 mol) in ethanol
(70 mL). The reaction mixture was refluxed in a water
bath for 1 h. After cooling, the crystalline product H4L
ing a series of nucleophilic functional groups (ОН
,
С=О, NН, C=S) and capable of participating in the
formation of donor–acceptor bonds with metal ions is
a promising complexing agent characterized by the
amidoimidol and/or thioneꢀthiol tautomerism. The
latter provides the coordination to the central metal
atom in different tautomeric forms. Depending on the
synthesis conditions and metal nature, the tautomers
can form coordination compounds of various compoꢀ
sitions, structures, and properties.
was filtered off, washed with ethanol cooled to 0°C and
diethyl ether, and recrystallized from ethanol. The
yield was 18.25 g (81%), mp = 214–215°C.
For C9H11N3O2S
The thiosemicarbazone complexes with Pd2+ ions
were shown [6] to be efficient catalysts in the Buchꢀ
wald–Hartwig amination and in carbon–carbon
bonding [7–10]. In addition, the complexes of thiꢀ
anal. calcd., %: C, 47.99; H, 4.90; N, 18.66; S, 14.22.
Found, %:
C, 47.89; H, 4.75; N, 18.93; S, 13.97.
1H NMR, , ppm: 2.88 d (3H, C9H3,
δ J = 4.5 Hz),
osemicarbazide derivatives with palladium and platiꢀ 6.90–6.96 m (2H, С5,7HAr), 7.45 t (1H, C6HAr,
J =
num have high biological activities (anticancer, antiꢀ 8.4 Hz), 7.87 d (1H, C8HAr,
malarial, antiviral, antiꢀinflammatory, fungicidal, NcH), 9.45 s (1H, NaH), 10.55 s (1H, NbH), 11.95
immunostimulating, and cardiotonic) and, hence, can (1H, OH). 13C NMR, , ppm: 31.40 C9, 115.14 C2,
J = 7.2 Hz), 8.13 s (1H,
s
δ
be considered as potent drugs [11–15]. Therefore, the 117.52 C6, 119.47 C5, 129.10 C7, 134.82 C5, 159.67 С3,
investigation of the complex formation of polydentate 169.02 С1, 182.42 С8
.
160

RHODIUM(III), PALLADIUM(II), AND PLATINUM(II) COMPLEXES
161
C5',7 ',6 '
Synthesis of [Rh(H3L)2]Cl (I)
. RhCl3 ⋅ 4H2O
HAr), 7.47
m
(1H, C6HAr), 7.88–7.98 m (3H,
C8,8'
(0.143 g, 0.5 mmol) was dissolved in ethanol (25 mL)
acidified with 4 N HCl (0.2 mL) at 35–40°C. A soluꢀ
tion of HBMHCTA (0.225 g, 1 mmol) in ethanol
(10 mL) was added with stirring to the obtained soluꢀ
tion for 3 min. The reaction mixture was refluxed for
30 min. The formed brown precipitate was filtered off,
washed with ethanol and diethyl ether, and dried in a
drying box above CaCl2. The yield was 0.158 g (54%),
HAr + 1H, NH), 8.87 s (1H, NcH), 10.79 s (1H,
NaH), 11.60 s (1H, b'H), 12.53 s (1H, OH).
N
13C NMR, , ppm: 30.6/31.8 C9, 115.5/118.1 С2,
δ
116.0/117.6 СAr, 119.5/120.4 СAr, 129.42/131.2 СAr,
131.3/134.8 СAr, 159.2/158.1 С3, 167.8/162.9 С1,
178.2/168.4 С8
.
Synthesis of [Pt(H2L)(H4L)] (IV)
. K2[PtCl4]
decomposition temperature
≥270°C.
(0.083 g, 0.2 mmol) was dissolved in water (10 mL) at
35–40°C, and the volume was brought with ethanol to
25 mL. A solution of HBMHCTA (0.095 g,
0.42 mmol) was added with stirring to the obtained
solution for 3 min. The reaction mixture was refluxed
for 15 min. The formed light green amorphous precipꢀ
itate was filtered off, washed with ethanol and diethyl
ether, and dried in a drying box above CaCl2. The yield
was 0.080 g (62%), decomposition temperature
For C18H20N6O4S2ClRh
anal. calcd., %: C,
H,
N,
S,
Cl,
Rh,
36.84; 3.43; 14.32; 10.93; 6.04; 17.53.
Found, %:
C, H, N, S, Cl, Rh,
36.59; 3.55; 13.99; 11.08; 5.73; 17.23.
1H NMR, , ppm: 2.96 d (3H, C9H3,
δ J = 4.5 Hz),
6.60–6.95 m (2H, С5,7HAr), 7.48 t (1H, C6HAr,
J =
≥265°С.
8.2 Hz), 7.96 d (1H, C8HAr,
NcH), 10.89 s (1H, NaH), 11.39 s (1H, NbH).
Synthesis of [Rh(KL’)3] (II) RhCl3 ⋅ 4H2O
J = 7.2 Hz), 8.76 s (1H,
For C18H20N6O4S2Pt
.
(0.143 g, 0.5 mmol) was dissolved in ethanol (25 mL)
at 35–40°C. A solution of HBMHCTA (0.225 g,
1 mmol) in a 0.1 N solution of KOH (30 mL) was
added with stirring to the obtained solution for 3 min.
The reaction mixture was refluxed for 60 min, and the
formed light brown precipitate was filtered off, washed
with ethanol and diethyl ether, and dried in a drying
box above CaCl2. The yield was 0.192 g (46%), decomꢀ
anal. calcd., %:
Found, %:
N, 13.06;
N, 12.76;
S, 9.95;
Pt, 30.31.
Pt, 29.89.
S, 10.21;
C9 '
1H NMR,
δ
, ppm: 2.90/2.96 dd (6H, C H3, H3,
= 14.7 Hz), 6.65 m (2H, С5,7HAr), 6.98
(3H,
(1H, C6HAr), 7.85–8.07 m
HAr + 1H, c'H), 8.88 s (1H, NсH),
J =
9
4.5,
J
m
C5',7 ',6 '
HAr), 7.08–7.46
m
C8,8 '
(3H, (3H,
N
position temperature ≥235°С.
10.78 s (1H, NаH), 11.60 s (1H, Nа'H), 11.87 s (1H,
For C27H21N9O3S3K3Rh
Nb'H), 12.11 s (1H, OH). 13C NMR,
δ, ppm:
anal. calcd., C, 38.79; H, 2.53; N, 15.08; S, 11.51; Rh, 12.31.
%:
30.7/31.4 C9, 115.0/115.8 С2, 117.2/119.0 СAr,
117.4/120.6 СAr, 129.0/131.5 СAr, 130.7/134.3 СAr,
Found, %: C, 39.02; H, 2.65; N, 14.92; S, 11.67; Rh, 12.67.
159.0/155.6 С3, 167.6/162.5 С1, 176.8/168.0 С8
.
1H NMR,
δ
, ppm: 2.88 m (3H, C9H3), 6.67
m
(1H,
Synthesis of [Pd(H2L)(PPh3)] (V). A solution of
C5HAr), 7.04
m
(1H, C7HAr), 7.97–8.07 m (2H,
HBMHCTA (0.022 g, 0.098 mmol) in ethanol
(20 mL) was carefully added to a solution of
PdCl2(PPh3)2 (0.044 g, 0.062 mmol) in chloroform
(20 mL) in such a way that mixing of the chloroform
and ethanol phases would be prevented. The mixture
was kept in a closed lightꢀproof vessel for 3 weeks. The
reaction product was formed as yellow plateꢀlike single
crystals. The yield was 0.025 g (67%), decomposition
C6,8HAr).
Synthesis of [Pd(H2L)(H4L)] (III). PdCl2 (0.097 g,
0.55 mmol) was dissolved in a mixture of ethanol
(25 mL) and 4 N HCl (0.2 mL) at 35–40°C. A soluꢀ
tion of HBMHCTA (0.248 g, 1.1 mmol) in ethanol
(10 mL) was added with stirring to the obtained soluꢀ
tion for 3 min. The reaction mixture was refluxed for
15 min, and the formed amorphous fleshꢀcolored preꢀ
cipitate was filtered off, washed with ethanol and
temperature ≥301°С.
diethyl ether, and dried in a drying box above CaCl2
The yield was 0.235 g (77%), decomposition temperaꢀ
ture 255
.
For C27H24N3O2PSPd
anal. calcd., %:
Found, %:
N, 7.09;
N, 6.97;
S, 5.41;
S, 5.28;
Pd, 17.97.
Pd, 17.78.
≥
°С.
For C18H20N6O4S2Pd
anal. calcd., %: N, 15.14;
S, 11.55;
S, 11.32;
Pd, 19.18.
Pd, 18.87.
1H NMR,
δ
, ppm: 2.86 d (3H, C9H3,
J
= 4.2 Hz),
Found, %:
N, 15.45;
6.90–6.97 m (3H, С5,7HAr and PPh3), 7.25
m (2Н,
PPh3), 7.42–7.65 m (13Н, PPh3, C6HAr), 7.88 d (1H,
C9 '
1H NMR,
δ
, ppm: 2.89/2.94 dd (6H, C H3, H3,
J =
9
C8HAr,
NaH).
J
= 8.1 Hz), 8.14 br.m (1H, NcH), 9.49 s (1H,
4.5, J m (3H,
= 14.7 Hz), 6.58 m (2H, С5,7HAr), 6.98
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 40
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162
ORYSYK et al.
Table 1. Crystallographic data and the main refinement paꢀ
The UVꢀVIS spectra of the complexes were
recorded on a Specord ꢀ40 spectrophotometer
(50000–11000 cm–1) in quartz cells with
= 0.1 cm.
rameters for complex
Parameter
V
М
l
Value
0.15
IR spectra were detected on a Specord M80 spectroꢀ
1
photometer (KBr pellets). H and 13C NMR spectra
Crystal size, mm
Crystal system
Space group
0.35
×
× 0.05
were measured on Varian VXR (300 MHz) and Bruker
Avance DRXꢀ500 (125.75 MHz) spectrometers in
DMSOꢀd6 with tetramethylsilane.
Xꢀray photoelectron spectra (XPS) were obtained
on an ESꢀ2402 spectrometer with PHOIBOSꢀ100ꢀ
Triclinic
P
1
a
, Å
, Å
9.9053(2)
12.0524(3)
12.2174(3)
SPECS energy analyzer ( МgКα 1253.6 eV, 200 W,
10–7 Pa). The spectrometer was equipped with an
IQEꢀ11/35 ion gun and FGꢀ15/40 slow electron gun
for the compensation of surface charging effects. The
spectra were calibrated by the C1 line (Ep = 285.0 eV).
The Pd3 spectra were decomposed to pairs of comꢀ
ponents with the parameters Id3/2 Id5/2 = 0.66, Еp
(3 3/2–3d5/2 = 4.6 and 5.3 eV, respectively. The full
width at the half height (FWHH) of the line was 1.2
and 1.0 eV, respectively. For the S2 level, Ip1/2 Ip3/2
0.5, FWHH = 1.2 eV, and p(2 1/2–2p3/2 = 1.0 eV.
The N1 spectra were decomposed to components
P =
b
2
×
c
, Å
, deg
, deg
, deg
α
64.8300(10)
81.1300(10)
67.4410(10)
1218.98(5)
2
s
β
d
/
Δ
γ
d
)
V
Z
, Å3
p
p
/
=
ΔЕ
)
ρcalcd, g/cm–3
, mm–1
1.613
s
with FWHH = 1.3 eV. The composition was perꢀ
formed using the Gauss–Newton method. The surꢀ
face areas of the components were determined after
background subtraction according to the Shirley
method.
The electrophoregrams of solutions of the comꢀ
plexes were obtained on chromatography paper strips
at a voltage of 280–300 V for 25–30 min. A 0.8 N soluꢀ
tion of lithium chloride (ethanol–water) served as a
supporting electrolyte [16].
μ
0.944
F(000)
600
θ
range, deg
1.84–30.57
Index range
–14
≤ h ≤ 14,
–17
≤
k
≤
17, –17 ≤ l ≤ 17
Number of all reflections/indeꢀ 34138/7411 (0.0476)
pendent (Rint
)
Reflections with
Number of refined parameters
Goodnessꢀofꢀfit (F 2
I
> 4
σ
(
I
)
6216
325
Xꢀray diffraction analysis. Unit cell parameters and
a threeꢀdimensional array of reflection intensities for a
)
1.047
single crystal of complex
SMART APEX II diffractometer (MoKα radiation,
= 0.71073 Å, graphite monochromator) at 173(1) K.
V were obtained on a Bruker
R1
,
,
wR2
wR2 (all reflections)
Δρmin
Å–3
(
I
≥
4
σ
(
I
))
0.0323, 0.0685
0.0432, 0.0738
0.640/–0.696
λ
R1
The structure was solved by a direct method and
refined for F2 by the fullꢀmatrix leastꢀsquares method
using the SHELXTL program package [17]. The
hydrogen atoms bound to the nitrogen atoms were
revealed from the difference electron density synthesis
and refined without restraints imposed by geometric
and thermal parameters. The hydrogen atoms bound
to the C atoms were specified in geometrically idealꢀ
ized positions according to the hybridization of
the accompanying carbon atom and refined using the
riding model with Uiso = 1.5Ueq in the case of the
CH3 group and Uiso = 1.2Ueq in all other cases. The
main Xꢀray diffraction data are given in Table 1.
Δρmax
/
, e
The elemental compositions of the complexes were
determined by electronꢀprobe Xꢀray microanalysis
(VRAꢀ30 spectrometer, 45 kV, W anode, membrane
diameter 7 mm, samples in KBr pellets). The relative
intensity of the PdKα lines was 04085 (03660, 0.0676),
and the probable uncertainty for the background was
≤0.0100. The relative intensity of the BrKα line was
1.647 0.005, and the probable uncertainty for the
background was 0.0015. The program for the calculaꢀ
tion of analytical line intensities by the method of relaꢀ
tionship equations to fundamental parameters was
applied to determine the quantitative characteristics.
Elemental analyses were carried out in parallel using
the classical methods: nitrogen was determined by the
Dumas method, chlorine and sulfur were determined
using the volumetric method after the combustion of a
weighed sample in oxygen, and carbon and hydrogen
were determined according to Pregle’s method.
The full set of data for compound V was deposited with
the Cambridge Crystallographic Data Centre
(no. 800401; deposit@ccdc.cam.ac.uk or http://
www.ccdc. cam.ac.uk).
RESULTS AND DISCUSSION
The complexes were synthesized by the reactions of
the components on heating in an ethanol solution
according to the scheme
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 40
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RHODIUM(III), PALLADIUM(II), AND PLATINUM(II) COMPLEXES
163
O
H
H
N
N
N
H
S
O
S
Rh
Cl
O
H
H
N
O
N
H
N
N
H
N
N
S
HO
H
H
+MCl
2
O
M : L = 1 : 2, pH 2
M
O
[Rh(H3L)2]Cl (I)
S
M : L = 1 : 2, pH 3
+RhCl · 4H O
N
3
2
N
N
H
H
5
O
[M(H2L)(H4L)]
4
OH
6
7
M = Pd (III
M = Pt (IV
)
S
H
9
3
c
)
a
2
N
1
b
N
N
8
H
H
O
(H4L)
+KOH, Et
M : L = 1 : 2, pH 9
–H O
2
P
+Pd(PPh ) Cl
3 2
2
M : L = 1 : 1.5
Pd
O
O
S
OH
N
N
N
N
H
H
N
N
[Pd(H2L)PPh3] (V)
SK
(HL')
KS
O
N
N
N
O
N
SK
N
Rh
N
O
N
N
N
SK
[Rh(HL')3] (II
)
Scheme.
The reaction of HBMHCTA with rhodium trichloꢀ similar conditions, K [PtCl ] and PdCl form comꢀ
2
4
2
ride at pH 3 and the reactant ratio M : L = 1 : 2 plexes III and IV containing two ligand molecules,
afforded complex with the tridentate coordination one of which is coordinated to the metal ion by the triꢀ
I
mode of the ligand and formation of fiveꢀ and sixꢀ dentateꢀchelating mode, and another ligand is coordiꢀ
membered chelate metallocycles through the sulfur, nated by the monodentate mode only by the sulfur
nitrogen, and oxygen atoms of the C=S and NH funcꢀ atom of the carbothioamide group as described earlier
tional groups and deprotonated OH group. Under [1, 18]. The competitive functional C=O group is not
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164
ORYSYK et al.
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
ε
3.0
1
32700
3
2.5
2.0
1.5
1.0
0.5
0
41200
33000
32000
29050
24000
31500
48000
40000
16000 ν
, cm–1
2
24330
1
35000
30000
25000
20000
15000
ν
, cm–1
Fig. 1. UVꢀVIS spectra of HBMHCTA and the rhodium complexes in С Н ОН: (1) HBMHCTA, (2) I, and (3) II.
2
5
involved in the donor–acceptor interaction with the
π* transition of the C=O carbonyl group. The preꢀ
metal ions because of a sterically more favorable dominant effect of this transition compensates the
arrangement of other functional groups.
effect of the
n
→ π
29050 cm–1. As a result, the π → π
*
transition of the C=S group at
transition can be
*
The reaction of HBMHCTA with RhCl3 · 4H2O at
pH 9 results in the formation of complex II including
three molecules of 2ꢀ(5ꢀmercaptoꢀ4ꢀmethylꢀ4Hꢀ
identified only after the decomposition of the specꢀ
trum to Gaussian components.
[1,2,4]triazolꢀ3ꢀyl)phenol Sꢀpotassium salt (HL)
formed due to the cyclization of HBMHCTA in an
alkaline medium, being consistent with published data
[19].
An analysis of the UVꢀVIS spectra of complex
I
showed that the lowꢀfrequency spectral range contains
shoulderꢀlike absorption bands at 24330, 26200, and
27600 cm–1 characterizing the 1A1
→ , →
1T1 1A1 1T2
g g
g
electron transitions [20] in the Rh3+ ion,grespectively,
The reaction of HBMHCTA with PdCl2(PPh3)2 in
and the ligandꢀtoꢀmetal chargeꢀtransfer (LMCT)
chloroform gives mixedꢀligand complex
V in which
transitions Rh
and 31500 cm–1 are caused by the chargeꢀtransfer
transition N Rh and intraligand → π transitions
→ S. Other absorption bands at 30250
the HBMHCTA molecule, as in compounds III and
IV, is coordinated to the palladium atom by the tridenꢀ
tateꢀcyclic mode through the sulfur atom of the C=S
group and through nitrogen and oxygen of the deproꢀ
tonated NH and OH groups, respectively.
→
n
*
of the C=O group [21–23]. This character of the specꢀ
trum of the complex is caused by its octahedral strucꢀ
ture and the appearance of the corresponding chroꢀ
mophores [Rh–S], [Rh–N], and [Rh–O] due to the
coordination of the ligand to metal.
Complex
I containing the chloride anion in the
external sphere can dissociate in an aqueous solution
to form the complex cation, which was established by
electrophoresis on paper [16]. The movement of the
colored spot towards the cathode confirms a positive
charge of the complex ion.
The absorption band of the d–d transition in the
Rh3+ ion of complex II appears at 22900 cm–1. The
next two absorption bands are due to the intraligand
1
The UVꢀVIS, IR, XPS, and H and 13C NMR
LMCTT and the n → π* transition of the C=N groups
of the triazole fragment formed by the intraligand
rearrangement and the appearance of the correspondꢀ
ing chromophore [Rh–N] at 32700 cm–1 [22].
spectra of H4L and complexes I–V were studied in
order to establish the coordination mode of the ligand
and the shape of the coordination node.
The highꢀfrequency region of the UVꢀVIS specꢀ
An analysis of the UVꢀVIS spectra of complexes III
trum of HBMHCTA contains an intense band of π → and V in a dimethylformamide solution shows that the
π*
transitions in the benzene ring at 41200 cm–1 absorption in the frequency range from 26150 to
(Fig. 1). In addition, the broadened absorption band 26400 cm–1 is caused by the spinꢀallowed d–d transiꢀ
with a maximum at 33000 cm–1 characterizes the π → tions between the ground energy level 1A1 and 1A2
,
g
g
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RHODIUM(III), PALLADIUM(II), AND PLATINUM(II) COMPLEXES
165
ε
4.0
3
ε
2.5
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
33700
32200
2.0
1.5
1.0
0.5
0
32200
1
28450
26150
2
ν
, cm–1
38
36
34
32
30
28
26
24
22
, cm–1
20
10–3
ν
×
Fig. 2. UVꢀVIS spectra of complexes III–V in dimethylformamide: (1) III, (2) IV, and (3) V.
which are characteristic of the planarꢀsquare shape of
the coordination node of Pd(II) [23] (Fig. 2). No
The IR spectrum of HBMHCTA exhibits the
ν
(C=O) stretching vibration band at 1640 cm–1 and
the broad band at 3200 cm–1 caused by
ν(N–H)
d⎯d
spinꢀallowed transition for the Pt2+ ion is
stretching vibrations [1, 26]. The vibrations of the
hydroxyl group joined by the intramolecular hydrogen
bond appear as a narrow band at 3370 cm–1, and asymꢀ
observed in the spectrum of complex IV, because this
transition is overlapped with the → π transition of
the C=S chromophore group of the ligand at
28300 cm–1 [23
26].
n
*
metric and symmetric ν(CH) stretching vibrations of
⎯
the methyl group appear as lowꢀintensity absorption
bands at 3000 and 2970–2950 cm–1. The bond vibraꢀ
In the highꢀfrequency spectral range, the intense
absorption bands at 28300–29500, 32200–
tions δas(NH), νs(NCS), δ(N–C–N), and ν(C=S)
33700 cm–1
(
III
, V
) and 31200–32200, 35500 cm–1
bonds are manifested in the frequency range from
1700 to 800 cm–1. The absorption bands at 1600–
1300 cm–1 are caused by vibrations of the benzamide
group, those at 1300–1000 cm–1 are due to vibrations
of the thioureide fragment, and the bands at 745 cm–1
are resulted from the C–H bending vibrations of the
aromatic ring.
(
IV) are due to the charge transfer in the intraligand
n
π → π
→ π*
transitions of the C=S/C=O groups and the
transitions of the benzene ring [1, 2, 18, 20,
*
27–29] and LMCTT [1, 2, 18, 28, 29]. The presented
frequency range exhibits the absorption band of the
LMCTT S
28450 cm–1
→
M at 28300 cm–1
(
III
, IV) and
(
V), which is related to the participation
The absorption bands of functional groups of the
of the C=S group of the ligand in coordination to the
central metal ion. The positions of the absorption
bands at 33000–35000 and 26400 cm–1 indicate the
formation of a chromophore consisting of the Pd, S,
O, and N atoms.
ligand in the IR spectra of complexes
I, III, and IV
undergo the following shifts (cm–1): 1605
→
→
→
1585
1505
1372
917
(
(
(
(
Δν = 20), 1560
Δν = 30), 1490
Δν = 22); 1280
→
→
→
1540 (Δν = 20); 1535
1520 (Δν = 30); 1350
1225 (Δν = 55); 885
→
Thus, the experimental UVꢀVIS spectral data show
that HBMHCTA in complexes I–V is coordinated to
the central metal ion simultaneously through the
donating atoms of nitrogen (NHamide), sulfur (C=S),
and oxygen of the deprotonated OH group to form the
octahedral (for the rhodium complexes) and square
(for the palladium and platinum complexes) coordiꢀ
nation modes.
Δν = 32), 815
→ 842 (Δν = 27). The ν(OH) absorpꢀ
tion band of the hydroxy group is absent from the
spectra of complexes II, and because of its deproꢀ
tonation and formation of the M–O covalent bond.
I,
V
The ν(OH) vibrations for complexes III and IV are
observed at 3400 cm–1, which is associated with the
monodentate coordination mode of the second thiꢀ
osemicarbazide molecule. The lowꢀfrequency range of
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166
ORYSYK et al.
Table 2. Binding energies for the main lines and components in the N1
s
, S2
p
3/2, Rh3
d
5/2, and Pd3
d
2/5 spectra
Cl2p, eV
Compound
H4L
N1
s
, eV
S2
p
, eV
Rh3
d
5/2, eV
Pd3 5/2, eV
d
400.4
(400.1, 400.5, 401.2)
162.4
163.7
163.6
163.3
I
400.7
(400.2, 400.7, 401.3)
310.6
310.3
198.2
II
400.9
(400.1, 400.8, 401.2)
III
400.75
338.3
(400.1, 400.7, 401.2)
these spectra exhibits an absorption band at 240– Rh3d5/2 by 0.35 eV only compared to that for comꢀ
272 cm–1 characteristic of stretching vibrations of the pound II. Under the synthesis conditions of
M
← S bond. The character of the IR spectra of comꢀ complex II, an alkaline medium results in ligand
plexes III and IV is identical, indicating in favor of the cyclization to form the triazole ring (scheme), due to
same coordination of the ligand to the central metal which the carbonyl group is absent in complex II. For
ion.
complexes III and V, Eb Pd3d5/2 = 338.15 and
338.05 eV, which completely corresponds to the divaꢀ
lent state of palladium ions.
The intense broadened band at 1593 cm–1 in the
spectrum of complex II is caused by the superposition
of several absorption bands corresponding to the
vibrations of the C–C bond of the aromatic ring and
The decomposition of the N1
osemicarbazide to components gave three values of Eb
N1 : 400.1, 400.6, and 401.2 eV corresponding to
three nonequivalent states of the nitrogen atoms. The
main N1 line consists of one band b N1 = 400.4 eV
s spectral lines of thiꢀ
ν
(C=N) of the heterocycle. At the same time, the
s
broad intense absorption band at 1100 cm–1 caused by
planar bending vibrations of the C–H bond of the aroꢀ
matic ring is more pronounced compared to the correꢀ
sponding absorption band at 1111 cm–1 in the starting
HBMHCTA, which is due to the conjugation of the
phenol fragment with the triazole heterocycle. The
s
E
s
corresponding to the protonated states of each nitroꢀ
gen atom in the ligand molecule. In the case of formaꢀ
tion of complex
unchanged, whereas in complex II
400.9 eV ( bN1 = 0.5 eV). The value of one of the
components also increases (Table 2), indicating in
favor of the formation of the M N(L) coordinaꢀ
I,
Eb N1
s
of the main line remains
E
bN1 increases to
s
ν(OH) absorption band is absent from the spectrum of
ΔE
s
complex II because of its deprotonation and formaꢀ
tion of the Rh–O bond. In addition, the lowꢀfreꢀ
quency range contains a new doublet band at 615 cm⎯
1
tion bond via the donor–acceptor mechanism. The
nitrogen atom of the heterocycle participates in comꢀ
plex formation, and its donor–acceptor interaction
responsible for the transformation of C=S into
(C
spectral characterization of complex II
⎯
S)– [30], which is one of the key moments in the
.
with the metal results in an increase in
Eb N1s.
The XPS method makes it possible to determine
both the valent state of the central atom and the nature
of its donor environment. The values of binding enerꢀ
gies of the internal electron levels (Eb) of various platꢀ
inum group metals allow one to determine the characꢀ
ter of chemical bonds in coordination compounds
with a high reliability [31, 32].
In rhodium complexes
Rh3d5/2 are 310.6 and 310.25 eV, which corresponds to
the trivalent state of the rhodium ion. The difference
(ΔEb Rh3d5/2 = 0.35 eV) in Eb Rh3d5/2 of the comꢀ
plexes is due to different characters of ligand coordiꢀ
nation. It is known that the ligands having accepting
groups of atoms (F, NO2, CO) withdraw the electron
density from the central atom, thereby favoring an
increase in Eb of the metal.
The decomposition of the N1 spectral line of comꢀ
s
plex III also gives three components of
Eb N1s: 400.1
,
400.75, and 401.2 eV. The value of Eb of the main N1
s
line increased to 400.75 eV, which is by 0.35 eV higher
than that of uncoordinated thiosemicarbazide. This
indicates in favor of Pd
N(L) bond formation. It
I and II, the values of Eb
should be noted that the covalent radius of Pd2+ is
longer than that of Rh3+. This favors a stronger Pd–N
interaction compared to Rh–N in complex
I
and,
probably, results in an increase in
Eb N1s.
The energy characteristics of the S2
p
lines in the
spectra of the initial ligand and complexes also differ.
The shift of the S2 line of complexes I–III towards
higher energies by 1.3–0.9 eV possibly indicates that
p
Complexes
ligand nature. In complex
C=O accepting group, which can increase of the Eb S2
metal to 1 eV. However, this group does not participate near the system of conjugated bonds of the triazole
in coordination, thus favoring an increase in Eb ring with the aromatic ring.
I
and II differ in both coordination and the sulfur atom participates in coordination bonding.
, the ligand contains the The increase in the S2 line in complex II by Eb
= 1.2 eV is due to the position of the sulfur atom
I
p
Δ
p
Δ
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RHODIUM(III), PALLADIUM(II), AND PLATINUM(II) COMPLEXES
167
(a)
(b)
Δ
, ppm
5
Δ
, ppm
5
6
7
8
9
6
7
8
9
10
10
11
12
13
14
15
11
12
13
14
15
12 11 10
, ppm
9
8
7
6
5
4
3
12 11 10
, ppm
9
8
7
6
5
4
3
Δ
Δ
1
1
Fig. 3. COSY H– H NMR spectra for (a) HBMHCTA and (b) complex III
.
The value of Eb Cl2
which unambiguously indicates its outꢀofꢀsphere group is observed.
p
for complex
I is 198.2 eV, ring undergo downfield shifts and no signal of the OH
arrangement [31, 32]. No Cl2 lines were detected for
other complexes, indicating that complexes II and III
contain no chlorine.
p
The 1H NMR spectra of complexes III and IV conꢀ
tain signals from two nonequivalent CH3 groups with
δ
= 2.89, 2.94 ppm in III and 2.90, 2.95 ppm in IV, as
well as two sets of signals with the multiplicity characꢀ
1
The H NMR spectrum of ligand H4L exhibits a
teristic of orthoꢀsubstituted benzene rings. The signals
doublet signal from protons of the СН3 group with a
chemical shift of 2.88 ppm. The range from 6.90 to
7.88 ppm contains signals from four protons of the
from the N(c)H protons are at
δ = 7.92, 8.87 ppm for
III and 8.01, 8.80 ppm for IV. This double set of sigꢀ
nals in the spectra of complexes III and IV indicates
the mixedꢀtype coordination of two ligand molecules
to the central metal atom.
benzene ring. The signal from the N(c)H proton (
δ =
8.13 ppm) was identified using nondiagonal crossꢀ
peaks in the 2D COSY 1Н–1Н NMR spectrum [33]
1
(Fig. 3). Other lowꢀfield signals with δ 9.45, 10.55, and
The H NMR spectrum of complex
V consists of
11.95 ppm correspond to the N(а)H, N(b)H, and ОН
signals from the protons of triphenylphosphine in the
coordination sphere of the complexes and from
HBMHCTA, except for two singlets of the N(b)H and
ОН groups.
protons, respectively [34, 35].
1
The H NMR spectrum of complex
I exhibits a
considerable downfield shift of all signals from the
protons of the NH groups, which is caused by metalꢀ
A comparison of the 13C NMR spectra of comꢀ
locycle formation. The absence of the signal from the plexes III and IV also indicates the identical coordinaꢀ
OH group in the spectrum indicates the deprotonation tion mode of the ligands in both compounds. As in the
of this group and formation of the Rh–O bond. Unlike 1H NMR spectra, the doubled number of signals comꢀ
the spectrum of compound I, the lowꢀfield of the specꢀ pared to the number of nonequivalent carbon atoms in
trum of complex II contains no signals from protons of the reactant molecule was observed, indicating the
all NH and CH groups, confirming the cyclization of mixedꢀtype coordination of two ligand molecules in
thiosemicarbazide and thiazole ring formation in each complex. For the carbon atom of the C=S group
complex formation. To confirm the formation of the in HBMHCTA,
triazole ring, HBMHCTA cyclization was carried out also exhibits signals at 178.2 and 168.4 ppm for III and
under the conditions similar to those for the synthesis at 176.8 and 167.9 ppm for IV. The values of δ 13
of
of complex II. The cyclization gave ligand HL', whose one of sets of signals from the carbon atoms of the aroꢀ
matic system differ insignificantly from the correꢀ
δ = 182.4 ppm. This spectral range
С
1H NMR spectrum is similar to that of complex II
,
except for the signal from the SH group, which is sponding signals of H4L, indicating the monodentate
absent from the spectrum of the complex because of coordination of one of the ligand molecules [1]. On
the formation of potassium salt. In addition, in the the contrary,
δ for the second set of signals for the corꢀ
spectrum of complex II, the signals of the aromatic responding carbon nuclei of the aromatic ring are
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 40
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168
ORYSYK et al.
scopic studies confirm the structures of complexes III
and IV shown in the scheme.
Complex studied by Xꢀray diffraction analysis
crystallizes with one ligand molecule in the symmetriꢀ
cally independent part (Fig. 4). The palladium atom
forms a weakly distorted square environment with a
molecule of ligand H2L coordinated through the triꢀ
dentate mode and supplemented by the tripheꢀ
nylphosphine molecule. The deviation from the rootꢀ
meanꢀsquare plane of the Pd(1)O(2)N(2)S(1)P(1)
coordination node is 0.0153 Å. The Pd–O, Pd–N,
C(18)
C(19)
C(20)
C(21)
V
C(17)
C(12)
C(13)
C(14)
C(16)
C(11)
C(10)
C(23)
C(26)
C(15)
O(2)
P(1)
C(5)
C(4)
C(6)
C(7)
C(22)
C(27)
C(24)
C(25)
Pd(1)
Pd–S, and Pd–P bond lengths in complex V (Table 3)
correspond to the published data for compounds of
this type [36, 37].
C(3)
C(2)
O(1)
C(8)
S(1)
C(1)
N(2)
The values of contiguous angles in the coordination
environment of palladium range from 86.04(5)° to
92.03(5)° (Table 3), which can be due to the steric
influence of the metallocycle and the bulky tripheꢀ
N(1)
C(9)
N(3)
nylphoshine molecule. Molecule
V includes two plaꢀ
nar metallocycles Pd(1)O(2)C(4)C(3)C(2)N(2) (the
deviation from the rootꢀmeanꢀsquare plane is
0.0402 Å) and Pd(1)N(2)N(1)C(1)S(1) (the deviation
from the rootꢀmeanꢀsquare plane is 0.0293 Å) conjuꢀ
gated at the N(2) atom and forming a dihedral angle of
Fig. 4. Molecular structure of complex
V (ellipsoids are
presented with 50% probability).
noticeably shifted compared to the spectrum of H4L
,
6.45(7)°. The H2L molecule contains a conjugated
which confirms the coordination of the second ligand
molecule through the chelate metallocycle. This coorꢀ
dination is also favored by a decrease in the intensity of
system of double bonds, which are difficult to be localꢀ
ized on the basis of the geometric parameters. The
C(1)–S(1), C(1)–N(1), C(1)–N(3) and C(2)–O(1),
C(2)–N(2) bond lengths (Table 3) correspond to the
published data for sesquialteral bonds between the
the narrow ν
(OH) signals at 3370 cm–1 in the IR specꢀ
tra of complexes III and IV, which is a result of the
participation of hydroxyl groups in the formation of
intramolecular hydrogen bonds. Thus, the spectroꢀ
corresponding atoms. In crystal structure
V
, the moleꢀ
…
(N O 2.824(2) Å, angle NHO
cules are joined by the hydrogen bonds N(1)–
#1
…
H(1N) O(1)
140(2)°) and
2.783(2) Å, angle NHO 153(2)
the centrosymmetric dimers (Fig. 5).
#1
…
–
…
N(3)–H(3N) O(1)
(
N O
z
Table 3. Bond lengths and bond angles in the structure of
°
); #1
x
+ 2, –
y
, – for
complex
Bond
Pd(1)–N(2) 2.0099(17) N(2)Pd(1)O(2) 90.72(6)
Pd(1)–O(2) 2.0143(16) N(2)Pd(1)S(1) 86.04(5)
V
d
, Å
Angle
ω, deg
Thus, we synthesized complexes I–V, whose
molecular structures were determined from the data of
elemental analyses and UVꢀVIS, IR, XPS, and 1H and
13C NMR spectroscopy. Rhodium cationic complex
I
with the tridentateꢀcyclic coordination of two moleꢀ
cules of the organic ligand and formation of the octaꢀ
hedral coordination node RhS2O2N2 was isolated from
an acidic medium (pH 3) at the molar ratio M : L =
1 : 2.
Pd(1)–S(1) 2.2612(6) O(2)Pd(1)S(1) 176.15(5)
Pd(1)–P(1) 2.2698(5) N(2)Pd(1)P(1) 175.90(5)
C(1)–S(1)
C(2)–O(1)
C(4)–O(2)
C(1)–N(1)
C(1)–N(3)
1.725(2)
1.265(2)
1.307(3)
1.322(3)
1.329(3)
O(2)Pd(1)P(1)
S(1)Pd(1)P(1)
92.03(5)
91.098(19)
In an alkaline medium (pH 9) at M : L = 1 : 2,
HBMHCTA undergoes cyclization with triazole ring
formation. The latter participates in coordination to
the central metal ion, resulting in the formation of
complex II and the sixꢀmembered metallocycle, as
N(1)C(1)N(3) 118.23(19)
N(1)C(1)S(1) 120.17(16)
N(3)C(1)S(1) 121.60(17)
C(1)N(1)N(2) 120.33(17)
C(2)N(2)N(1) 113.23(17)
C(2)N(2)Pd(1) 131.38(14)
N(1)N(2)Pd(1) 115.38(12)
O(1)C(2)N(2) 120.40(19)
O(1)C(2)C(3) 120.91(18)
N(2)C(2)C(3) 118.65(18)
N(1)–N(2) 1.397(2)
C(2)–N(2) 1.329(3)
well as the octahedral node RhO3N3
.
The coordination compounds of palladium (III
)
and platinum (IV) with the mixedꢀtype (tridentate and
monodentate) coordination modes of the ligand were
isolated at pH 2 and reactant ratio M : L = 1 : 2. This
specific feature of the coordination of HBMHCTA to
the central metal ion appears in the 1H and 13C NMR
spectra as a double set of all 1H and 13C signals.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 40
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RHODIUM(III), PALLADIUM(II), AND PLATINUM(II) COMPLEXES
169
N(3A)
O(1)
N(1A)
N(1)
N(3)
O(1A)
Fig. 5. Centrosymmetric dimers in crystal structure
V (hydrogen bonds are designated by dashed lines).
14. Hernandez, W., Paz, J., Vaisberg, A., et al., Bioinorg.
Chem. Appl. 2008, vol. 2008, doi:
10.1155/2008/690952
The molecular structures proposed for
,
complexes III and IV are indirectly confirmed by the
result of the Xꢀray diffraction analysis of complex
V in
which the HBMHCTA molecule is coordinated
according to the tridentate mode proposed for comꢀ
15. KovalaꢀDemertzi, D., Millerb, J.R., Kourkoumeliꢀ
sa, N., et al., Polyhedron, 1999, vol. 18, p. 1005.
plexes III and IV
.
16. Lederer, M., An Introduction to Paper Electrophoresis,
Amsterdam: Elsevier, 1957.
17. SHELXTL, Madison (WI, USA): Bruker AXS Inc.,
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33. Braun, S., Kalinowski, H.O., and Berger, S., 150 and
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Translated by E. Yablonskaya
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 40
No. 3
2014