Half-sandwich ruthenium-arene complexes with thiophen containing thiosemicarbazones: Synthesis and structural characterization

Article abstract of DOI:10.1016/j.jorganchem.2017.01.013

Novel conformationally rigid half-sandwich organoruthenium(II) complexes ([(η⁶-p-cymene)Ru(η¹-S-TSC¹)Cl₂], (1); [(η⁶-p-cymene)Ru(η¹-S-TSC²)Cl₂], (2) and [(η⁶-p-cymene)Ru(η²-N,S-TSC³)Cl]Cl, (3) have been synthesized from the reaction of [{(η⁶-p-cymene)RuCl}₂(μ-Cl)₂] with the respective thiosemicarbazones TSC¹(2-acetyl-5-chloro-thiophene thiosemicarbazone), TSC²(2-acetyl-5-methyl-thiophene thiosemicarbazone) and TSC³(3-thiophene aldehyde thiosemicarbazone) in a 1: 2 M ratio in methanol and all of the complexes have been characterized by elemental analysis, UV–Vis, FT-IR and¹H NMR spectroscopy. The crystal structures of TSC¹, TSC²and [(η⁶-p-cymene)Ru(η¹-S-TSC²)Cl₂], (2) have been determined by X-ray crystallography revealing that TSC¹and TSC², crystallized in the monoclinic space group P2₁/c and complex (2) show a distorted octahedral geometry around the ruthenium centre. The mononuclear complex adopts a typical three legged piano-stool geometry (a description commonly used for half–sandwich compounds) with the metal centre coordinated by two chlorides and a TSC ligand. The coordination geometry around Ru^IIatom is distorted octahedron with three sites occupied by the p-cymene ligand (with an ?⁶coordination mode) while the remaining three sites occupied by the S atom of the TSC ligand and two Cl atoms. The spectroscopic studies showed that TSC¹and TSC²are coordinated to the central metal as a monodentate ligand coordinating via the thiocarbonyl sulfur atom (C[dbnd]S) in complexes (1) and (2), whereas TSC³is coordinated to ruthenium as a bidentate ligand through azomethine nitrogen (C[dbnd]N) and sulfur atom in complex (3).

Full text of DOI:10.1016/j.jorganchem.2017.01.013

Accepted Manuscript
Half-sandwich ruthenium-arene complexes with thiophen containing
thiosemicarbazones: Synthesis and structural characterization
Pelin Köse Yaman, Betül Şen, Cansu Sonay Karagöz, Elif Subaşı
PII:
S0022-328X(17)30033-5
10.1016/j.jorganchem.2017.01.013
JOM 19770
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 30 May 2016
Revised Date: 27 July 2016
Accepted Date: 18 January 2017
Please cite this article as: P.K. Yaman, B. Şen, C.S. Karagöz, E. Subaşı, Half-sandwich ruthenium-
arene complexes with thiophen containing thiosemicarbazones: Synthesis and structural
characterization, Journal of Organometallic Chemistry (2017), doi: 10.1016/j.jorganchem.2017.01.013.
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Graphical Abstract

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Half-sandwich ruthenium-arene complexes with thiophen containing
thiosemicarbazones: Synthesis and structural characterization
Pelin Köse Yaman a, Betül Şen b, Cansu Sonay Karagöz c, Elif Subaşı a, *
aDepartment of Chemistry, Faculty of Science, Dokuz Eylül University, 35160 İzmir, Turkey
bDepartment of Physics, Faculty of Science, Dokuz Eylül University, 35160 İzmir, Turkey
cThe Graduate School of Natural and Applied Sciences, Dokuz Eylül University, 35160 İzmir, Turkey
* Corresponding author. Tel.: +90 232 301 8692; fax: +90 232 453 4188.
E-mail address: elif.subasi@deu.edu.tr
ABSTRACT
Novel conformationally rigid half-sandwich organoruthenium(II) complexes ([(η6-p-
cymene)Ru(η1-S-TSC1)Cl2], (1); [(η6-p-cymene)Ru(η1-S-TSC2)Cl2], (2) and [(η6-p-
cymene)Ru(η2-N,S-TSC3)Cl]Cl, (3) have been synthesized from the reaction of [{(η6-p-
cymene)RuCl}2(ꢀ-Cl)2] with the respective thiosemicarbazones TSC1 (2-acetyl-5-chloro-
thiophene thiosemicarbazone), TSC2 (2-acetyl-5-methyl-thiophene thiosemicarbazone) and
TSC3 (3-thiophene aldehyde thiosemicarbazone) in a 1: 2 M ratio in methanol and all of the
1
complexes have been characterized by elemental analysis, UV–Vis, FT-IR and H NMR
spectroscopy. The crystal structures of TSC1, TSC2 and [(η6-p-cymene)Ru(η1-S-TSC2)Cl2],
(2) have been determined by X-ray crystallography revealing that TSC1 and TSC2,
crystallized in the monoclinic space group P21/c and complex (2) show a distorted octahedral
geometry around the ruthenium centre. The mononuclear complex adopts a typical three
legged piano-stool geometry (a description commonly used for half–sandwich compounds)
with the metal centre coordinated by two chlorides and a TSC ligand. The coordination
geometry around RuII atom is distorted octahedron with three sites occupied by the p-cymene
ligand (with an ƞ6 coordination mode) while the remaining three sites occupied by the S atom
of the TSC ligand and two Cl atoms. The spectroscopic studies showed that TSC1and TSC2
are coordinated to the central metal as a monodentate ligand coordinating via the thiocarbonyl
sulfur atom (C=S) in complexes (1) and (2), whereas TSC3 is coordinated to ruthenium as a
bidentate ligand through azomethine nitrogen (C=N) and sulfur atom in complex (3).
Keywords: Ruthenium(II); arene complexes; Thiophen containing Thiosemicarbazones

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1. Introduction
Thiosemicarbazones (TSCs) are of considerable pharmacological interest since a number
of derivatives have shown a broad spectrum of biological properties. The wide range of
biological activities possessed by substituted TSCs and their metal complexes include
cytotoxic, antitumor, antibacterial and antiviral properties [1]. TSCs are versatile ligands as
they have a number of donor atoms which may coordinate in various ways [2]. Incorporation
of metals onto these ligands can result in alteration or enhancement of their biological activity
[3]. Many examples of pharmacological applications with TSCs and their metal complexes
have been evaluated for their antibacterial [4, 5], antifungal [6, 7], antiviral [8], antiamoebic
[9], antimalarial [10] and antitumor [11,12] activities. It is considered to be a reason for
biological activity that the TSC molecules to chelate with trace metals in biological system.
There has been much interest in the chemistry of half-sandwich arene ruthenium(II)
complexes since the development of useful synthetic precursors with the general formula
[RuCl2(η6-arene)]n [13-16]. Organometallic ruthenium compounds, which are particularly the
half of sandwich complexes, are emerging as a very promising class of anti-tumor and anti-
microbial agents. The geometry of these complexes provides a good scaffold for generating
new molecules by changing the coordinated arene, the chelated ligand and the chloride group
[17, 18]. As ligands, TSCs have more than one potential donor. Therefore, we tried to observe
the sites of substitution of these ligands to the metal center. We have already described, half-
sandwich (η6-p-cymene) ruthenium(II) complex [(η6-p-cymene)RuClTSCN-S]Cl and carbonyl
complexes
[Ru(CO)Cl(PPh3)2TSCN-S],
[Ru(CO)(PPh3)2(η3-O,N3,S-TSC1)],
[Ru(Cl)(CO)(PPh3)2(η2-N3,S-TSC2)] and [Ru(Cl)(CO)(PPh3)2(η2-N3,S-TSC3)] [19-20].
As part of our continued interest in the synthesis and structural aspects of ruthenium(II)
complexes, new conformationally rigid half-sandwich organoruthenium(II) complexes ([(η6-
p-cymene)Ru(η1-S-TSC1)Cl2], (1); [(η6-p-cymene)Ru(η1-S-TSC2)Cl2], (2) and [(η6-p-
cymene)Ru(η2-N,S-TSC3)Cl2], (3) have been synthesized from the reaction of [{(η6-p-
cymene)RuCl}2(ꢀ-Cl)2] with the respective thiosemicarbazones TSC1 (2-acetyl-5-chloro-
thiophene thiosemicarbazone), TSC2 (2-acetyl-5-methyl-thiophene thiosemicarbazone) and
TSC3 (3-thiophene aldehyde thiosemicarbazone) in a 1: 2 M ratio in methanol and all of the
1
complexes have been characterized by elemental analysis, UV–vis, FT-IR and H NMR
spectroscopy. The crystal structures of the novel ligands TSC1, TSC2 and the complex [(η6-p-
cymene)Ru(η1-S-TSC2)Cl2], (2) have been determined by X-ray crystallography.

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2. Experimental
2.1. Materials
Acetonitrile (ACN), benzene, petroleum ether, dichloromethane, methanol, ethanol, hexane
and silica gel were purchased from Merck and RuCl3.3H2O, α-Phellandrene were obtained
from Sigma-Aldrich. All chemicals used for the syntheses of TSCs were purchased from
Sigma-Aldrich as well. The precursor complex [{(η6-p-cymene)RuCl}2(ꢀ-Cl)2] was
synthesized following the literature method [21]. TSCn (n= 1-3) ligands were prepared by
reducing the Schiff bases [22].
2.2. Methods
Reactions were carried out under an oxygen-free argon atmosphere using Schlenk techniques.
All glassware was oven-dried at 120˚C. All solvents were dried and degassed using standard
techniques and stored under nitrogen until used [23]. Elemental analyses were carried out
using a LECOCHNS-O-9320 by Technical and Scientific Research Council of Turkey,
TUBITAK. IR spectra on a Varian 1000 FT spectrophotometer (KBr pellets) and UV–vis
Spectra Shimadzu Model 1800 spectrophotometer were recorded on samples at the Dokuz
1
Eylül University. H NMR spectra were recorded in CDCl3 on 500 MHz High Performance
Digital FT NMR at Ege University and chemical shifts were referenced to tetramethylsilane
(TMS).
2.3. Synthesis
2.3.1 Synthesis of TSC ligands (general procedure).
The preparative methods for TSCs were well described by Klayman et al. [24] and Scovill
[25]. The TSC1 and TSC2 were obtained from 2-acetyl-5-methylthiophene/2-acetyl-5-
chlorothiophene and thiosemicarbazide (1:1 M ratio) in absolute ethanol with addition of two
drops of sulfuric acid. The mixture was refluxed for 4 hour and then cooled. The solid was
precipitated, filtered and recrystallized from ethanol. TSC3 was synthesized according to the
literature [26].
2.3.1.1 2-Acetyl-5-chloro-thiophene thiosemicarbazone, (TSC1)
Yield : 1.2 g, 92%. mp : 175-180 °C. C7H8N3S2Cl: Calcd. C 35.9; H 3.5; N 17.9; S 27.4%;
found: C 35.6; H 3.6; N 17.9; S 27.5%. IR (KBr pellet), ʋmax/cm-1: 3223 (s) (NH2), 3151 (s)
1
(N–H), 1575 (s) (C=N), 1065 (m) (N-N), 839 (s) (C=S), 1108 (s) (CN,NCN). H NMR (400

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MHz, CDCl3), (δ:ppm): 8.59 (s, 1H, N–H), 8.10 (br, 2H, NH2), 2.22 (s, 3H, CH3-C=N). UV-
Vis (THF) (nm) (A): λ: 250 (0.79), 343 (1.87).
2.3.1.2 2-Acetyl-5-methyl-thiophene thiosemicarbazone, (TSC2)
Yield : 1.6 mg, 94%. mp : 165-170 °C. C8H11N3S2: Calcd. C 45.0; H 5.2; N 19.7; S 30.0%;
found: C 45.2; H 5.0; N 19.3; S 30.4%. IR (KBr pellet), ʋmax/cm-1: 3232 (s) (NH2), 3140 (m)
(N–H),1547 (s) (C=N), 1034 (m) (N-N), 840 (m) (C=S), 1102 (m) (CN, NCN). 1H NMR (400
MHz, CDCl3), (δ:ppm): 8.62 (s, 1H, N–H), 8.16 (br, 2H, NH2), 2.24 (s, 3H, CH3-C=N). UV-
Vis (THF) (nm) (A) : λ: 248 (0.82), 338 (2.14).
2.3.1.3 3-Thiophene aldehyde thiosemicarbazone, (TSC3)
Yield : 980 mg, 89%. mp : 158-165 °C. C6H7N3S2: Calcd. C 38.9; H 3.8; N 22.7; S 34.6%;
found: C 38.5; H 3.9; N 22.9; S 34.7%. IR (KBr pellet), ʋmax/cm-1: 3255 (w) (NH
), 3147 (m)
2
(N–H), 1530 (s) (C=N), 1038 (m) (N-N), 1055 (m) (N-N), 817 (s) (C=S), 1090 (m) (CN,
NCN). 1H NMR (400 MHz, CDCl3), (δ:ppm): 9.30 (s, 1H, N–H), 8.58 (br, 2H, NH2), 7.87 (s,
1H, HC=N). UV-Vis (THF) (nm) (A): λ: 315 (1.38).
2.3.2. Synthesis of the Ruthenium complexes (general procedure).
[{(η6-p-cymene)RuCl}2(ꢀ-Cl)2] was synthesized as described in the literature and the yield is
1.8-2.0g (78-87%) [21]. Complexes (1–3) were prepared by reacting [{(η6-p-
cymene)RuCl}2(ꢀ-Cl)2] with the respective thiosemicarbazone ligands TSC1, TSC2 and TSC3
were obtained in 78–83% yields. The methods employed are very similar and given in detail
as a representative example.
Thiosemicarbazone ligand (TSC1) (260 mg, 1.12 mmol) was dissolved in methanole (20 ml)
and was added to a stirred suspension of [{(η6-p-cymene)RuCl}2(µ-Cl)2] (340 mg, 0.56
mmol) in hot methanole (20 ml). Then, the resulting solution was refluxed under nitrogen
atmosphere for 4 hours. The reaction mixture was then cooled to room temperature, which
results in the formation of precipitate. The compound was filtered and the purity of the
complexes was checked by TLC. The products were recrystallized from CH2Cl2/hexane
mixture. Then it was dried in vacuum.
2.3.2.1 [(η6-p-cymene)Ru(η1-S-TSC1)Cl2], 1
Yield : 500 mg, 83%. mp : 138-140 °C. C17H19N3S2Cl2Ru: calcd. C 40.8; H 3.8; N 8.4; S
12.8%; found: C 40.9; H 3.6; N 8.8; S 12.4%. IR (KBr pellet), ʋmax/cm-1: 3249 (m) (NH2),

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3130 (w) (N-H), 1572 (s) (C=N), 1088 (m) (N-N), 801 (s) (C=S), 871, 754, 695 (m)
1
(thiophene ring). H NMR (400 MHz, CDCl3), (δ:ppm): 10.91 (s, 1H, N–H), 8.07 (br, 2H,
NH2), 6.08-7.59 (m, 2H, thiophen ring; ds, 4H, p-cymene ring), 2.96 (m, 1H, CH(CH3)2), 2.26
(s, 3H, CH3-C=N), 2.08 (s, 3H, CH3), 1.34 (d, 3H, CH(CH3)2), 1.12 (d, 3H, CH(CH3)2). UV-
vis (THF) (nm) (A): λ: 352(1.14).
2.3.2.2 [(η6-p-cymene)Ru(η1-S-TSC2)Cl2], 2
(TSC2) (852 mg, 4 mmol) and [{(η6-p-cymene)RuCI}2(µ-Cl)2] (1224 mg, 2 mmol) gave
1600 mg, 77% of compound 2 as orange powder.
Yield : 1600 mg, 77%. mp : 135-140 °C. C18H22N3S2ClRu: calcd. C 44.9; H 4.6; N 8.7; S
13.3%; found: C 44.7; H 4.9; N 8.3; S 13.7%. IR (KBr pellet), ʋmax/cm-1: 3253 (m) (NH
),
2
3147 (m) (N-H), 1546 (w) (C=N), 1051 (m) (N-N), 803 (s) (C=S), 870, 701, 662 (m)
1
(thiophene ring). H NMR (400 MHz, CDCl3), (δ:ppm): 10.81 (s, 1H, N–H), 8.17 (br, 2H,
NH2), 6.10-7.45 (m, 2H, thiophen ring; ds, 4H, p-cymene ring), 2.64 (1H, m, CH(CH3)2), 2.26
(s, 3H, CH3-C=N), 2.12 (s, 3H, CH3), 1.32 (d, 3H, CH(CH3)2), 1.21 (d, 3H, CH(CH3)2). UV-
vis (THF) (nm) (A): λ: 348 (0.64).
2.3.2.3 [(η6-p-cymene)RuCl(TSC3)]Cl, 3
(TSC3) (207 mg, 1.12 mmol) and [{(η6-p-cymene)RuCI}2(µ-Cl)2] (340 mg, 0.56 mmol) gave
400 mg, 73% of compound 3 as orange powder.
Yield : 400 mg, 73%. mp: 145-150°C. C16H18N3S2CIRu: calcd. C 42.4; H 4.0; N 9.3; S
14.2%; found: C 42.2; H 4.2; N 9.1; S 14.4%. IR (KBr pellet), ʋmax/cm-1: 3265 (w) (NH
),
2
3124 (w) (N-H), 1545 (s) (C=N), 1055 (m) (N-N), 798 (s) (C=S), 840, 798, 656 (m)
1
(thiophene ring). H NMR (400 MHz, CDCl3), (δ:ppm): 11.37 (s, H, N-H), 8.58 (br, 2H,
NH2), 8.35 (s, 1H, HC=N), 6.00-7.00 (m, 3H, thiophen ring; ds, 4H, p-cymene ring), 2.85
(1H, m, CH(CH3)2), 2.06 (3H, s, CH3), 1.11 (d, 6H, CH(CH3)2). UV-vis (THF) (nm) (A): λ:
296 (0.62); 326 (0,63).
2.4 Crystal structures determination and refinement
The suitable single crystals of the compounds were chosen for the crystallographic
study. The molecular structure of the compounds is determined by single crystal X-ray
diffraction. Single-crystal data were collected at 293(2) K by ω-scan technique, on an Agilent
Diffraction Xcalibur X-ray diffractometer with an Eos CCD area detector using graphite-
monochromated radiation MoKα (λ = 0.71073 Å) from a enhance X-ray source. The data

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collection, cell refinement and data reduction were performed using the CrysAlisPro program
[27]. Solution, refinement and analysis of the structures were done using the OLEX2 system
[28]. The crystal structures were solved by the direct method using the SHELXS [29] and
refined by full-matrix least squares method based on F2 against all reflections using the
SHELXL [30]. All non-hydrogen atoms were refined anisotropically. The crystal structure
positions of hydrogen atoms were treated as riding atoms. Geometrical calculations were
performed using PLATON [31]. The figures were made using ORTEP [32] and OLEX2 [28].
Details of the data collection conditions and the parameters of the refinement process are
given in Table 1.
3. Results and discussion
3.1 Synthesis
Novel conformationally rigid half-sandwich organoruthenium(II) complexes of the general
formula ([(η6-p-cymene)Ru(η1-S-TSC1)Cl2], (1); [(η6-p-cymene)Ru(η1-S-TSC2)Cl2], (2) and
[(η6-p-cymene)Ru(η2-N,S-TSC3)Cl]Cl, (3) have been prepared by reacting [{(η6-p-
cymene)RuCl}2(µ-Cl)2] with the respective TSC ligands TSCn (n=1-3) in a 1:2 molar ratio in
1
methanol. For the structural characterization FT-IR spectra, UV–Vis spectra and H NMR
spectra were used and the corresponding data are given in experimental section.
All of the complexes were isolated in medium yields and are well enough stable in air
and light. The analytical data given in experimental section for the complexes are in a good fit
with the formula recommended. The complexes are soluble in general organic solvents such
as dichloro methane and chloroform. Several attempts have been made to get the single
crystals of all the complexes but it has been ineffective except complex (2). The spectroscopic
data and the single crystal X-ray studies of TSC1, TSC2 and the complex (2) reasonably
support the formulas of the compounds.
3.2 Analytical Data
The analytical data for the ligands and complexes (1–3) are summarized in the
experimental section. The stoichiometry of the ligands and their complexes has been
confirmed by elemental analyses. The analytical data for the complexes are in good

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agreement with the formula proposed and the spectroscopic data are given in the experimental
section. The spectroscopic data fairly supports the formula of the compounds.
3.3 Infrared Spectra
The FT-IR spectra of the free ligands were compared with those of the metal complexes in
order to study the binding modes of the TSC ligand to the ruthenium metal. The main
stretching frequencies of TSCn (n=1-3) and Ru(II) complexes (1-3) are given in the
experimental section.
TSCs are shown with general formula, [R1R2C2N3N2(H)C1(S)N1R3R4], can coordinate in a
number of different manners. Most commonly they bind as either of two tautomeric forms, a
neutral thione form or the anion from the thiol form. Infrared spectroscopy was used to
confirm coordination as the thione form in (1-3). FT-IR spectra of the free ligands were
compared with the complexes to confirm the coordination of the ligand to ruthenium.
The highest frequency bands at 3223-3255 cm−1 region in spectra of the ligands are assigned
to υasym and υsym of terminal NH2. These bands are present in the spectra of the complexes (1-
3) at 3249-3265 cm-1 region, indicating non-involvement of this group in coordination. A
strong band at 3151 cm−1, (TSC1); 3140 cm−1, (TSC2) and 3147 cm−1, (TSC3) attributed to
υ(N–H) of –NH–N=C in spectra of free ligands are present with altered frequencies in the
spectra of metal complexes at 3130 cm−1, (1); 3147 cm−1, (2); and 3124 cm−1, (3) as shown in
the literature [33].
The absorptions due to C=N of the free ligands at 1575 cm−1 (TSC1), 1547 cm−1 (TSC2),
and 1530 cm−1 (TSC3) were observed in the FT-IR spectra. Coordination of the
thiosemicarbazone ligands to ruthenium ion through azomethine nitrogen is expected to
change the electron density in the azomethine and thus alters υ(C=N) band frequency after
complexation, indicating coordination of azomethine nitrogen to ruthenium ion [34].
However, the υ(C=N) bands observed at 1572 cm−1 and 1546 cm−1, in complex (1) and (2),
respectively remained unchanged. Co-ordination of the TSC3 to the ruthenium ion through

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azomethine nitrogen atom is changed the electron density in the azomethine link and thus
alters the υ (C=N) absorption frequency about 15 cm-1 at 1545 cm−1, in complex (3).
Coordination via the thiocarbonyl sulfur atom is inferred by the following observations.
The free ligands display υ(C=S) absorption at 839 cm−1 (TSC1), 840 cm−1 (TSC2) and 817
cm−1 (TSC3). This band is also present in the low frequency region in the spectra of the
complexes at 801 cm−1 (1), 803 cm−1 (2) and 798 cm−1 (3). The downward (C=S) band shift
(19-38 cm-1) in the complexes provides evidence for coordination of thiocarbonyl sulfur atom
for all of the complexes [35, 36]. No bands near 2570 cm-1 due to υ(C-SH) suggesting that these
ligands remain in the thione form in the solid-state in complexes (1-3). FT-IR spectra of the
complexes show that TSC1and TSC2 are coordinated to the central metal as a monodentate
ligand coordinating via the thiocarbonyl sulfur atom (C=S) in complexes (1) and (2), whereas
TSC3 is coordinated to ruthenium as a bidentate ligand through azomethine nitrogen (C=N)
and sulfur atom in complex (3).
The υ(N–N) bands of TSCs are at 1065 cm-1 (TSC1), 1034 cm-1 (TSC2) and 1038 cm-1
(TSC3). The increase in frequency of these bands 1088 cm-1 (1), 1051 cm-1 (2), 1055 cm-1
(3) in the spectra of all the complexes respectively provides evidence for either the
coordination via the azomethine nitrogen [37] as in complex (3) or H-bonding between NH
and Cl atoms as seen from the X-ray crystallographic structure of complex (2). These two
reasons may change the stretching frequency of N-N bond. The bands observed at 871, 754,
695 cm-1 for complex (1); 870, 701, 662 cm-1 for complex (2) and 840, 798, 656 cm-1 for
complex (3) are attributed to the thiophene ring deformation modes in the ligands. These
thiophene ring deformation vibrations are not affected in the complexes [38].
3.4 1H NMR spectra
1
The ligand-to-metal bonding is further supported by H NMR spectra. The TSC ligands
and the complexes are very soluble in CHCl3 and so their NMR spectra were obtained in
1
CDCl3. The H NMR spectral results obtained for TSCn and n=1–3 in CDCl3 with their
assignments are given in the experimental section.
In the spectrum of complex (3), sharp singlets at 8.35 ppm has been assigned to
azomethine proton (–HC=N). The positions of azomethine signal in the complexes are shifted
to a lower field compared to free ligands at 7.87 ppm (TSC3), indicating coordination through
the azomethine nitrogen. A downfield shift is observed for these signals compared to the free
ligands upon coordination to ruthenium, suggesting coordination of the metal to the

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azomethine nitrogen atom as the signal becomes more deshielded in each case. This is also
observed for similar arene ruthenium (II) thiosemicarbazone complexes [39, 40].
The absence of the signal at 4.00 ppm that can be ascribed to –SH is consistent with the
idea that in solution, as in the solid state, TSCs exist as the thione tautomer in the complexes
(1-3) [41]. The singlet signal due to the methyl (CH3-C=N) on the ligands (TSC1-TSC2) are
observed at 2.22 ppm and 2.24 ppm respectively, these signals shifts slightly towards lower
field in complexes (1) and (2) at 2.26 ppm.
The isopropyl methines are found as multiplets at 2.96 ppm, in (1); 2,64 ppm, in (2) and
2.85 ppm, in (3). The isopropyl methyls are occured as two doublets at 1.34 and 1.12 ppm, in
(1) and 1.32 and 1.21 ppm, in (2), whereas only as a doublet at 1.11 ppm, in (3). The singlet
signal due to the methyl on the rings are observed at 2.08 ppm, in (1); 2.12 ppm, in (2) and
1
2.06 ppm, in (3). In the H NMR spectra of complex (1) and (2) the loss of symmetry is
evidenced by the appearance of sets of doublets in the region of 5.50- 7.50 ppm accounting
for the protons of the p-cymene rings. The methyl substituents of the isopropyl group are
observed as two distinct doublets in the aliphatic region of the spectra, which further confirms
the loss of symmetry as the two methyl groups are non-equivalent. These doublets belong to
the methyl protons are observed at 1.34 and 1.12 ppm for complex (1) and 1.32 and 1.21 ppm
for complex (2). The loss of symmetry of the arene rings in complex (1) and (2) suggests that
these complexes have similar modes of coordination. The p-cymene protons resonate at
frequencies typically seen for this group [42].
The NH2 signals in the complexes attributed to the ligand are practically unchanged from
the free ligands. The NH2 group generates broad signal at 8.07 ppm, in (1); 8.17 ppm, in (2)
and 8.58 ppm (3). Resonances of terminal NH2 in (1-3) are seen in the same positions as in
ligand spectra confirming the non-involvement of this group in coordination. A signal for the
1
hydrazinic NH protons at 8.59 ppm (TSC1), 8.62 ppm (TSC2), and 9.30 ppm (TSC3) in H
NMR spectra of the ligands are present in NMR spectra of the complexes; 10.91 ppm (1),
10.81 ppm (2), and 11.37 ppm (3) with gradual downfield shifts.
All the other protons resonate in regions commonly expected. The 1H NMR spectra of the
complexes (1-3) are essentially direct combination of the signals from the ligands plus those
from the p-cymene moiety. In the 1H NMR spectra of complexes (1-3) all indications are that
the ligands remain neutral form (as evidenced by the presence of the NH protons). Multiplets
are observed at around 6.60–7.93 ppm in all the complexes and have been assigned to the
aromatic protons of p-cymene ring and thiophen of the thiosemicarbazone ligands.
Furthermore, in all the complexes largest ꢁδ are observed for the protons that are located

ACCEPTED MANUSCRIPT
close to the coordinating atoms. So, the deshielding effect of the metal is apparent to such
protons [43].
3.5 Electronic spectra
The electronic spectra of the ligands and its copmlexes were recorded in THF. The spectra of
free ligands showed two types of bands at 314-343 and 248-250 nm. The probable assigment
for these bands are due to the n-π* (thiosemicarbazones) and π-π* (thiophene) transitions.
The ground state of Ru (II) is 1A1g, arising from the t62g configuration in an octahedral
environment. Excited state corresponding to the t5 e1 configuration are 3T1g, 3T2g, 1T1g and
2g
g
1T2g. Hence four bands, corresponding to the transitions 1A1g
1T1g and 1A1g 1T2g are possible, in order of increasing energy. The electronic spectra of
Ru(II) complexes show several absorptions in the ultraviolet region. Bands at 296-351 nm in
all Ru(II) complexes may be assigned to Ru (4dπ)
π* (imine) transitions. The pattern of
3T1g, 1A1g 3T2g, 1A1g
the electronic spectra of all the complexes indicate the presence of an octahedral geometry
around ruthenium (II) ion [44].
3.6. Description of the crystal structures
3.6.1 Crystal structure of TSC1and TSC2
The compounds, TSC1 and TSC2, crystallized in the monoclinic space group P21/c; their
molecular structures are illustrated in Fig. 3 and 4, respectively. TSC2 comprises two
crystallographically independent molecules (A and B) in the asymmetric unit. The
corresponding bond lengths and bond angles of molecules A and B of TSC2 agree well with
each other and are within normal ranges.
The thiophene rings (S4/C10–C13 in molecule A of TSC2, S6/C18–C21 in molecule B of
TSC2 and S2/C3–C6 in TSC1) are reasonably planar, the maximum deviation from planarity
being 0.006 (5), 0.018 (5) and 0.004 (1) Å for atoms C12, C20 and C3, respectively. The two
endocyclic C–S bonds lengths, C10–S4 and C13–S4 in A; C18–S6 and C21–S6 in B and C3–
S2 and C6–S2 in (I), are 1.723 (7) and 1.708(8) Å; 1.707(7) and 1.698(8) Å and 1.721(2) and
1.710(2) Å, respectively. These distances are in good agreement with a related compound [45-
47].
The TSC fragment in molecule A and B is almost planar with the maximum deviation
0.0386 and 0.0577 Å, respectively, and in TSC1 maximum deviation is 0.0547 Å. The TSC
group adopts an extended conformation, which can be seen from the torsion angle value of

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S3/C8/N5/N6=172.9(4)o in molecule A, S5/C16/N8/N9=–169.4(5)° in molecule B and
S1/C1/N2/N3= –169.7(2)° in TSC1. This conformation enables the formation of an
intramolecular N–H···N hydrogen bond. The exocyclic C–S distances, C8–S3 and C16–S5 in
both A and B are 1.690(6) Å, respectively, and in TSC1 distance C1–S1 is 1674(2) Å, confirm
their significant double-bond character [48]. The N–N bond lengths are 1.364 (7) and 1.370
(7) Å in molecules A and B, respectively, of compound TSC1, and 1.377(3) Å in compound
TSC2. These bond lengths are very close to that reported for a similar TSC compound [49-51].
Likewise, in compound TSC1, the C6–Cl1 bond length is comparable with those in related
structures [52, 53]. In all three compounds, the molecular structure is stabilized by a cyclic
intramolecular N–H···N hydrogen bonds which generate S(5) ring motifs (Table 2) [54].
In the crystal of compound TSC1, molecules are linked by pairs of N–HꢂꢂꢂS hydrogen
bonds, forming inversion dimmers with an R2 (8) ring motif (Table 2 and Fig. 5). The dimers
2
are linked by πꢂꢂꢂπ interaction [Cg1ꢂꢂꢂCg1i= 3.8330(3) Å, inter-planar distance=3.6174 Å,
slippage 1.267 Å, where Cg1 is the centroid of the S2/C3–C6 ring; symmetry code: (i) x, 3/2 -
y, 1/2+z], forming ribbons lying parallel to plane
.
In the compound TSC2, the molecules labeled as A are linked via bifurcated N–HꢂꢂꢂS and
C–HꢂꢂꢂS hydrogen bonds, forming A–A dimers with two R1 (7) ring motifs, and R2 (8) and
2
2
R2 (14) ring motifs. The molecules labeled as B is also involved in intermolecular N8–
2
H8ꢂꢂꢂS5i2 hydrogen bonds, resulting in R2 (8) centrosymmetric dimers. In addition to these,
2
the dimers are packed by pairs of N–H···S hydrogen bonds interactions forming
centrosymmetric rings with set-graph motif R2 (8) and resulting in the formation of a two-
2
dimensional network extending along [100], (Fig. 6). The crystal packing is further stabilized
by intermolecular C15–H15BꢂꢂꢂCg1 and C23–H23AꢂꢂꢂCg2 interactions into supramolecular
chains running along the c axis. Cg1 and Cg2 are the centres of gravity of thiophene rings
S4/C10–C13 and S6/C18–C21, respectively. Details of these interactions are given Table 2.
3.6.2 Crystal structure of the Complex (2)
The title compound adopts a typical three legged piano-stool geometry (a description
commonly used for half–sandwich compounds) with the metal centre coordinated by two
chlorides and a TSC ligand. The coordination geometry around RuII atom is distorted
octahedron with three sites occupied by the p–cymene ligand (with an ƞ6 coordination mode)
while the remaining three sites occupied by the S atom of the TSC ligand and two Cl atoms
(Fig. 7). The distorted octahedral geometry is evident from the bond angles given in Table 3.

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The six-membered ring of the p-cymene is almost planar, with a maximum deviation of -
0.020 (4) Å (C20) and an overall r.m.s. deviation of 0.0126 Å. The dihedral angle between the
p-cymene ring (C17–C22) and the isopropenyl group (C23–C25) planes is 75.90 (0.27)o.
The Ru–C(ring) distances are in the range 2.1364 (1)–2.2414 (1) Å and agree well with
those reported for similar structures [55,56]. The distance between the RuII ion and the least-
squares plane of the p-cymene aromatic ring is 1.6703 (1) Å, which is very close to that
reported in other (p-cymene)ruthenium(II) complexes [57, 58]. Defining X as the centroid of
the aromatic ring, the Cl1—Ru1—X, Cl2—Ru1—X and S3—Ru1—X angles are 126.85,
125.73 and 129.00o, respectively.
The two Ru–Cl bond distances are slightly different [2.4215(2) and 2.4324 (2) Å], longer
than those of previously reported structures [59-61]. The bond lengths in the coordinated TSC
ligand are nearly similar in free TSC ligand. Besides, the bond angles in the TSC moiety
shows significant changes on coordination.
The molecular structure is stabilized by N4–H4AꢂꢂꢂN6 and N5–H5ꢂꢂꢂCl1 intramolecular
interactions, which generate S(5) and S(6) ring motifs, respectively. In the crystal packing,
both chloro ligands are involved in H-bonded interaction with the NH2 moieties of a
neighbouring molecule, thus forming a symmetry-related dimeric structure (Table 4). These
interactions combine to link the molecules into zigzag chains of rings which run parallel to the
b axis (Fig. 8).
4. Conclusion
This paper describes the synthesis, structural and spectral characterization of thiophene
containing TSC1-3 ligands and their half-sandwich ruthenium (II) arene complexes ([(η6-p-
cymene)Ru(η1-S-TSC1)Cl2], (1); [(η6-p-cymene)Ru(η1-S-TSC2)Cl2], (2) and [(η6-p-
cymene)Ru(η2-N,S-TSC3) Cl]Cl, (3). The crystal structures of TSC1, TSC2 and [(η6-p-
cymene)Ru(η1-S-TSC2)Cl2], (2) have been determined by X-ray crystallography revealing
that TSC1 and TSC2, crystallized in the monoclinic space group P21/c and complex 2 show a
distorted octahedral geometry around the ruthenium centre. The mononuclear complex adopts
a typical three legged piano-stool geometry with the metal centre coordinated by two
chlorides and a TSC ligand. The coordination geometry around RuII atom is distorted
octahedron with three sites occupied by the p-cymene ligand (with an ƞ6 coordination mode)
while the remaining three sites occupied by the S atom of the TSC ligand and two Cl atoms.
The spectroscopic studies showed that TSC1and TSC2 are coordinated to the central metal as a

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monodentate ligand coordinating via the thiocarbonyl sulfur atom (C=S) in complexes (1) and
(2), whereas TSC3 is coordinated to ruthenium as a bidentate ligand through azomethine
nitrogen (C=N) and sulfur atom in complex (3). Althoug N,S-coordination mode is the most
common for thiosemicarbazone ligands, unusual monodentate coordination mode of TSC1and
TSC2 in complex (1) and (2) are shown in this paper. In the spectral data of the complexes all
indications are that the TSC ligands remain neutral form.
Acknowledgments
The authors also acknowledge Dokuz Eylul University for the use of the Agilent Xcalibur Eos
difractometer (purchased under University Research Grant No: 2010.KB.FEN.13). Thanks to
Assist. Prof. Dr. Muhittin Aygün for single crystal X-Ray analysis at Physics Department, in
Dokuz Eylul University. This study was supported by project number 2015.KB.FEN.018
from Dokuz Eylul University Rectorship, Scientific Research Project Coordination Center.
We gratefully thank the Graduate School of Natural and Applied Sciences, Dokuz Eylul
University, EBILTEM, Ege University for NMR analysis, and TUBITAK, for elemental
analysis.
Supplementary material
CCDC 1478649, 1478648 and 1478647 contains the supplementary crystallographic data for
the ligand (TSC1) and ligand (TSC2) and complex (1), respectively. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
(+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
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Fig. 1. Thiosemicarbazones (TSC1-3)

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Fig. 2. Ru(II) complexes (1-3
Fig. 3. The molecular structure and atom-numbering scheme for the title compound TSC1.
Displacement ellipsoids are shown at the 50% probability level.

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Fig. 4. The molecular structure of the two independent molecules (A and B) of compound
TSC2, showing the atom labelling. Displacement ellipsoids are drawn at the 50%
probability level.
Fig. 5. A partial view along the c axis of the crystal packing of compound TSC1, showing
the N–H ꢂꢂS hydrogen bonds (dashed lines), which result in the formation of inversion
dimers with an R2 (8) ring motif. Symmetry code as in Table 2.
2

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Fig. 6. A partial view along the b axis of the crystal packing of compound (II), showing
the N–H···S and C–H···S hydrogen bonds (dashed lines), which result in the formation of
two R1 (7)motifs, and three R2 (8) motifs and R2 (14) ring motif. H atoms not involved in
2
2
2
hydrogen bonding have been omitted for clarity. Symmetry code as in Table 2.
Fig. 7. The molecular structure and atom-numbering scheme for the complex (2).
Displacement ellipsoids are drawn at the 40% probability level. The 6-binding mode of the
p-cymene ligand is represented by a heavy dashed line between the Ru atom and the
centroid of the aromatic ring.

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Fig. 8. Part of the crystal structure of complex (2) showing the formation of hydrogen-
bonded dimers running parallel to the [010] direction. H atoms not involved in hydrogen
bonding have been omitted for clarity. Symmetry code as in Table 4.
Table 1
Crystal data and structure refinement parameters for the Compound TSC1, Compound TSC2 and Complex (2).
TSC1
TSC2
2
Chemical formula
Formula weight
Temperature (K)
Space group
C7H8ClN3S2
233.73
C8H11N3S2
213.32
C18H25Cl2N3RuS2
519.50
293(2)
293(2)
293(2)
P21/c
P21/c
Pbca
Crystal system
monoclinic
5.5637(4), 25.2322(16)
7.4806(6)
monoclinic
orthorhombic
15.3842(9), 12.5628(6),
22.7967(15)
14.9578(12), 28.511(2),
5.6542(4)
a, b, c (Å)
α, β, γ (o)
90, 104.221(8), 90
90, 93.956(7), 90
90, 90, 90
4405.9(4)
8
Cell volume (Å3)
Formula unit cell Z
ρcalc (g/cm3)
1017.97(13)
4
2405.5(3)
8
1.525
480.0
0.741
1.178
896.0
1.566
F(000)
2112.0
1.151
Absorption coefficient ꢀ (mm-
0.406
1
)

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Crystal size (mm3)
Diffractometer
0.5805×0.3742×0.221
Xcalibur, Eos
0.695×0.271×0.111
0.35×0.283×0.134
Xcalibur, Eos
MoKα / λ = 0.71073
13189
Xcalibur, Eos
MoKα / λ = 0.71073
4900
Radiation/Wavelength (Å)
Reflections measured
MoKα / λ = 0.71073
3994
-6 ≤ h ≤ 3, -31 ≤ k ≤ 22,
-9 ≤ l ≤ 9
-18 ≤ h ≤ 18, 0 ≤ k ≤ 35, -16 ≤ h ≤ 18, -14 ≤ k ≤ 14,
Range of h, k, l
0 ≤ l ≤ 7
-26 ≤ l ≤ 25
Data/Restraints/Parameters
2067/0/119
4900/0/239
3758/0/240
R1=0.0393, wR2=0.0950
R
1=0.0478,
wR2=0.0568
1=0.0950,
R1 =0.1108,
wR2=0.3541
Final R indexes [I>=2σ (I)]
R1=0.0542, wR2=0.1024
R
R1 =0.1566,
wR2=0.3774
Final R indexes [all data]
wR2=0.0655
Goodness-of-fit on F2
1.063
1.278
0.922
Largest diff. peak/hole (e Å-3)
0.34/ -0.27
1.51/ -0.53
0.55/ -0.52
Table 2:
Hydrogen-bond geometry for TSC1 and TSC2 (Å, o)
D – H ··· A
D – H
0.86
H ··· A
2.28
D ··· A
D – H ··· A
N1 – H1A ꢂꢂꢂ N3
N1 – H1B ꢂꢂꢂ S1ii
2.6338(2)
3.4443(3)
105
176
0.86
2.59
N4 – H4A ꢂꢂꢂ N6
N4 – H4B ꢂꢂꢂ S5
N5 – H5 ꢂꢂꢂ S3i1
C15 – H15AꢂꢂꢂS3i1
N7 – H7A ꢂꢂꢂ N9
N7 – H7B ꢂꢂꢂ S3
N8 – H8 ꢂꢂꢂ S5i2
0.86
0.86
0.86
0.96
0.86
0.86
0.86
2.20
2.45
2.61
2.81
2.27
2.67
2,79
2.5558(2)
3.2904(3)
3.4668(3)
3.4643(3)
2.6166(2)
3.4899(3)
3.6136(3)
105
167
173
126
104
161
161

ACCEPTED MANUSCRIPT
C15–H15CꢂꢂꢂCgi3
C15–H15BꢂꢂꢂCgi4
0.96
0.96
2.80
2.83
3.6962(3)
3.6962(3)
156
140
Symmetry codes: (ii) -1-x, 1-y, 1-z; (i1) -x, 1-y, 1-z; (i2) 1-x, 1-y, -z; (i3) x, y, 1+z,
(i4) x, y, -1+z.

Table 3 :
Selected geometric parameters for complex 2 (Å, o).
ACCEPTED MANUSCRIPT
Ru1 – S3
S3 – C8
S4 – C10
S4 – C13
N4 – C8
N5 – N6
N5 – C8
2.422(1)
1.700(5)
1.719(5)
1.713(5)
1.309(5)
1.379(5)
1.343(8)
Cl1 – Ru1 – Cl2
Cl1 – Ru1 – S3
S3 – Ru1 – Cl2
N4 – C8 – S3
88.38(5)
89.17(5)
83.97(5)
120.8(4)
121.6(4)
92.0(3)
N5 – C8 – S3
C13 – S4 – C10
Table 4:
Hydrogen-bond geometry for Complex 2.
D – H ··· A
D – H
0.86
0.86
0.86
0.86
H ··· A
D ··· A
D – H ··· A
N6 – C9
1.277(6)
N6 – N5– C8– S3
178.0(3)
N4 – H4A ꢂꢂꢂ N6
2.28
2.42
2.60
2.49
2.6307(2)
105
143
131
152
N5 – H5 ꢂꢂꢂ Cl1
3.1472(2)
3.2276(2)
3.2729(2)
N4 – H4A ꢂꢂꢂ Cl1*
N4 – H4B ꢂꢂꢂ Cl2*
Symmetry codes: (*) 3/2-x, -1/2+y, z

ACCEPTED MANUSCRIPT
Highlights
•
•
•
Preparation of thiosemicarbazones TSCn (1-3).
Synthesis of organoruthenium(II) complexes (1-3) with TSCs.
Characterization by elemental analysis, UV–Vis, FT-IR, 1H NMR, single crystal X-ray
diffraction spectroscopy.