Synthesis and catalytic activity of semiconducting p-cymene ruthenium 1,3,4-thiadiazole and 1,2,4-triazole complexes

Article abstract of DOI:10.1080/15533174.2012.751421

The novel ruthenium(II) complexes containing 5-(pyridin-4-yl)-1,3,4- thiadiazol-2-amine(1) and 4-amino-5-(pyridin-4-yl)-4H-1,2,4-triazole-3-thiol (2) ligands were synthesized and characterized by UV-Vis, IR, NMR, and elemental analysis. The complexes have

Full text of DOI:10.1080/15533174.2012.751421

This article was downloaded by: [Massachusetts Institute of Technology]
On: 04 November 2014, At: 20:22
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House,
37-41 Mortimer Street, London W1T 3JH, UK
Synthesis and Reactivity in Inorganic, Metal-Organic,
and Nano-Metal Chemistry
Publication details, including instructions for authors and subscription information:
http://www.tandfonline.com/loi/lsrt20
Synthesis and Catalytic Activity of Semiconducting
p-Cymene Ruthenium 1,3,4-Thiadiazole and 1,2,4-
Triazole Complexes
Zafer Serbetci a
a Department of Chemistry, Faculty of Sciences and Art , Bingöl University , Bingöl , Turkey
Accepted author version posted online: 19 Mar 2013.Published online: 02 May 2013.
To cite this article: Zafer Serbetci (2013) Synthesis and Catalytic Activity of Semiconducting p-Cymene Ruthenium 1,3,4-
Thiadiazole and 1,2,4-Triazole Complexes, Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry,
43:8, 957-960, DOI: 10.1080/15533174.2012.751421
To link to this article: http://dx.doi.org/10.1080/15533174.2012.751421
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained
in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no
representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the
Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and
are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and
should be independently verified with primary sources of information. Taylor and Francis shall not be liable for
any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever
or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of
the Content.
This article may be used for research, teaching, and private study purposes. Any substantial or systematic
reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any
form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://
www.tandfonline.com/page/terms-and-conditions

Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 43:957–960, 2013
Copyright ꢀ Taylor & Francis Group, LLC
C
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2012.751421
Synthesis and Catalytic Activity of Semiconducting
p-Cymene Ruthenium 1,3,4-Thiadiazole and 1,2,4-Triazole
Complexes
Zafer Serbetci
¨
¨
Department of Chemistry, Faculty of Sciences and Art, Bingol University, Bingol, Turkey
EXPERIMENTAL
The novel ruthenium(II) complexes containing 5-(pyridin-4-
yl)-1,3,4-thiadiazol-2-amine(1) and 4-amino-5-(pyridin-4-yl)-4H-
1,2,4-triazole-3-thiol (2) ligands were synthesized and character-
ized by UV-Vis, IR, NMR, and elemental analysis. The complexes
have been employed as catalysts for the transfer hydrogenation of
acetophenone in the presence of KOH using 2-propanol as a hy-
drogen source at 82◦C. Moreover, the temperature dependence of
conductivity of the complexes was determined in the temperature
range of 303–373 K. The complex [Ru(1,2)(p-cymene)Cl2] exhibits
the semiconducting behavior, as the conductivity of the samples is
increased with the increase in temperature.
All manipulations were performed under argon using Stan-
dard Schlenk Techniques. All reagents were obtained from com-
mercial suppliers and used without further purification. Solvents
were dried by standard methods and distilled under argon before
use.
NMR spectra were recorded at 297 K on a Bruker
300 MHz Ultrashield TM NMR spectrometer at 300 MHz (1H),
75.48 MHz (13C) (Inonu University, Turkey). Organic carbon,
hydrogen, nitrogen, and sulfur contents were determined using
a Leco CHNS-932 analyzer (Inonu University, Turkey). Melting
points were determined using an ELECTROTHERMAL 9100
melting point detection apparatus (Firat University, Turkey) and
are uncorrected. Infrared spectra were measured with a Perkin-
Elmer Spectrum One FTIR system and recorded using a univer-
sal ATR sampling accessory within the range 550–4000 cm−1
(Bingol University, Turkey). GC measurements for catalytic ex-
periments were performed using a Younglin Acme 6100 GC
instrument (C¸ anakkale Onsekiz Mart University, Turkey) with
a HP5 cap. The dimeric complex [Ru(p-cymene)Cl2]2 was
synthesized by the reported[13,14] method. A Shimadzu 3600
UV-VIS-NIR spectrophotometer was used to record the elec-
tronic spectra (Bingol University, Turkey). The dimeric com-
plex [Ru(p-cymene)Cl2]2 was synthesized by the reported[13,14]
method. The electrical resistances of the samples were measured
by two probe method using a KEITHLEY 6517A electrometer
(Firat University, Turkey).
Keywords 1, 3, 4-thiadiazole ligand, 1, 2, 4-triazole ligand, ruthe-
nium complexes, transfer hydrogenation of ketones,
organometallic semiconductor
INTRODUCTION
Electrical properties of metal complexes depend on their ge-
ometric shape, crystal structure and metal-ligand interaction.[1,2]
Semiconductor properties of synthesized ruthenium complexes
are investigated considering the -N, -S bonded interactions in the
aromatic chain of its ligands and the metal-ligand interactions.
Thus, the contribution of ruthenium complexes to the semicon-
ductor technology is targeted. Conductivity measurements of
complexes were synthesized by pellet.[3–5]
In addition to their economic importance and contribution to
the quality of life, catalyst is interesting for the subtlety with
which they go about their business.[6] Many studies during the
last decade have been designed to identify a good Ru(II) catalyst
for transfer hydrogenation of ketones.[7,8] Ruthenium(II) com-
plexes with properties of a catalyst increases the importance of
every day.[10–12] Synthesized complexes have been employed as
catalysts for the TH of acetophenone derivatives.
Materials and Syntheses
Synthesis of 5-(pyridin-4-yl)-1,3,4-thiadiazol-2-amine (1)
L1 was synthesized according to literature.[15] 1H NMR (δ,
DMSO-d6): 7.50 (s, 2H, NH2), 7.68 (dd, J = 5.23, 1.83, 2H),
Ar.C-CH, 8.70 (d, J = 5.86, 2H, Ar. N-CH). IR(cm-1): 3220,
3170, 3110, 3000, 1621.
Synthesis of 4-amino-5-(pyridin-4-yl)-4H-1,2,4-triazole-3-thiol
(2)
L2 was synthesized according to literature.[16] 1H NMR (δ,
DMSO-d6): 14.02 (br, 1H, SH), 8.74 (dd, J = 6.23, 1.47, 2H,
pyridyl H3, H5), 7.99 (dd, J = 6.23, 1.47, 2H, pyridyl H2, H6),
Received 18 October 2012; accepted 16 November 2012.
Address correspondence to Zafer Serbetci, Bingo¨l University, Fac-
ulty of Sciences and Art, Department of Chemistry, 12000 Bingo¨l,
Turkey. E-mail: z serbetci@hotmail.com
957

958
Z. SERBETCI
5.84 (br, 2H, NH2); 13C NMR (d, DMSO-d6): 168.4, 150.9,
148.1, 133.6, 122. IR(cm-1): 3380, 3200, 3090, 3000, 2925,
2762, 2560.
Anal. Calcd. for C18H24N5Cl2SRu (%): C, 42.0; H, 4.7; N, 13.6;
S, 6.2. Found (%): C, 41.6; H, 4.2; N, 13.0; S, 6.3.1H NMR (δ,
DMSO-d6): 8.69–8.74 (m, CH, 2H), 8.18 (d, J = 6.6, CH,
1H), 7.97 (d, J = 6.6, CH, 1H), 5.78 (dd, J = 17.5, 6.6, CH,
2H), 5.75 (dd, J = 17.5, 6.6, CH, 2H), 2.84–2.77 (m, -CH,
1H), 2.07 (s,CH3, 3H), 1.15 (d, J = 7.0, CH3, 6H). 13C NMR
(δ, DMSO-d6): 18.4, 22.0, 30.4, 86.0, 86.9, 100.6, 106.9, 120.3,
123.4, 126.6, 129.3, 151.0. IR(cm-1): 1603(νC N).
Synthesis of [Ru(L1)(p-cymene)Cl2](1a)
Ru-p-cymene dimer (306 mg, 0.5 mmol) was added to a
THF solution (5 mL) of 1 ligand (178 mg, 1.0 mmol). The
color of mixture immediately turned from brown to yellow. The
reaction mixture was stirred at room temperature for 2 h. The
precipitate was filtered off, washed with THF and filtered off
again, to remove un-reacted 1. The residue was dissolved in
CH2Cl2 (5 mL) and then precipitated with diethyl ether (10 mL)
to give the dark yellow solid with. Yield: 1.95 g, 91%. mp
225◦C. Anal. Calcd. for C18H23N4Cl2SRu (%): C, 43.3; H, 4.6;
N, 11.2; S, 6.4. Found (%): C, 41.8; H, 4.1; N, 11.4; S, 6.2. 1H
(δ, DMSO-d6): 7.60 (s, NH2, 2H), 8.90 (d, J = 6.3, Ar.C-CH,
2H), 8.63 (d, J = 5.1, Ar. N-CH, 2H) 5.58 (d, J = 5.9, CH,
2H), 5.39 (d, J = 5.9, CH, 2H) 2.80–2.84 (m, CH, 1H), 2.08
(s, -CH3, 3H) 1.75 (s, C(CH3)2, 6H). 13C NMR (δ, DMSO-d6):
18.4, 22.0, 30.5, 86.0, 86.8, 100.6, 106.9, 120.7, 138.3, 116.0,
154.5, 170.3. IR(cm-1): 1604(νC N).
RESULTS AND DISCUSSION
Synthesis and Characterization of RuII Complexes
[Ru2(p-cymene)2Cl4] reacts with pyridine-based ligands in
(1a, 2a) THF at room temperature in (Scheme 1) and the re-
sulting air-stable heteroleptic mononuclear complexes can be
isolated. Synthesized complexes were soluble in most organic
solvents and were fully characterized by elemental analysis and
spectroscopic methods.
All complexes gave 1H- and 13C-NMR spectra corresponding
to the proposed formulations. Despite many attempts, X–ray
quality crystals of 1a and 2a were not obtained. Therefore, the
stereochemistry of the complexes was determined on the basis
1
of H- and 13C-NMR spectra, which exhibited the expected
Synthesis of [Ru(L2)(p-cymene)Cl2](2a)
1
Ru-p-cymene dimer (306 mg, 0.5 mmol) was added to a singlet resonances. In the H-NMR spectra, Me-Ph-CH(Me)2
THF solution (5 mL) of 2 ligand (193 mg, 1.0 mmol). The protons for 1a and 2a were observed as a singlets at 2.09 ppm
color of mixture immediately turned from brown to yellow. The for both complexes. Me-C6H4-CH(Me)2 protons were observed
reaction mixture was stirred at room temperature for 2 h. The as doublet at 1.85–1.21 ppm in 1a and as multiplets at 1.18 and
precipitate was filtered off, washed with THF and filtered off 1.28 ppm in 2a Me-C6H4-CH(Me)2 protons for 1a and 2a were
again, to remove un-reacted 2. The residue was dissolved in observed as multiplets at 2.81–2.86 ppm and 2.80–2.88 ppm,
CH2Cl2 (5 mL) and then precipitated with diethyl ether (10 mL) respectively. Me-C6H4-CH(Me)2 protons for 1a and 2a were
to give the yellow solid with. Yield: 1.95 g, 91%. mp 235◦C. observed as multiplets at 5.77–5.84 ppm for both complexes.
SCH. 1. Synthesis of 1a and 2a.

SEMICONDUCTING P-CYMENE RUTHENIUM
959
TABLE 1
Catalytic activity for transfer hydrogenation of ketones
catalyzed by Ru(II) complexesa
OH
O
HO
0.01 mmol RuII
0.1 mmol KOH
O
+
R
+
R
82 °C
Entry
Substrate
Catalyst
Conversion (%)
96 (26)b
56
O
1
2
1a
2a
CH3
O
O
3
4
1a
2a
98
63
FIG. 1. The electronic absorption spectra 1a and 2a, recorded in 5 × 10–5
M
CH3
CH3
CH3
CH3OH (color figure available online).
F
Py-Ho and –Hm protons for 1a were observed as doublets in a
2:2 ratio at 8.63 ppm and 8.90 ppm, respectively. On the other
hand, Py-Ho and –Hm protons for 2a were observed as doublets
in a 2:2 ratio at around 8.74–8.69 ppm and 8.18 ppm. From
13C-NMR spectra, while sp3-hybridized carbon peaks observed
as three singlets, sp2- hybridized carbon peaks observed as nine
singlets for both complexes 1a and 2a.
5
6
1a
2a
95
59
Cl
O
7
8
1a
2a
95
55
Br
UV–Vis Spectra
O
9
10
1a
2a
78
29
The electronic transition for all the complexes were recorded
in methyl alcohol solution. The absorption spectra of complexes
1a and 2a mainly consist of two resolved bands in the range
200–600 nm.
The absorption spectra of the two Ru(II) complexes are char-
acterized by intense π - π∗ ligand transitions in the UV and
metal-to -ligand charge transfer (MLCT) transition in the visi-
ble region[17]. Figure 1 showed the absorption spectra of 1a and
2a in methyl alcohol solutions. For metal-ligand charge transfer
complexes 1a and 2a in the range 350–500 nm and 250–300 nm
transitions between the ligands is observed for the π-π∗.[18,19]
CH3
H3C
O
11
12
O
1a
2a
42
11
CH3
aReactions were carried out at 82◦C using 1 mmol substrate with
0.01 mmol RuII in 5 mL of 2-propanol for 0.5 h. bReactions were carried
out at 25◦C using 1 mmol substrate with 0.01 mmol RuII in 5 mL of
2-propanol for 1 h.
Catalytic Studies
The complexes 1a and 2a have been tested as catalyst in
the transfer hydrogenation (TH) of ketones with KOH in 2-
propanol under argon atmosphere to ascertain to most optimum
conditions (Table 1). Catalytic experiments were carried out un-
der identical conditions to allow comparison of results. Very
rapid conversions are achieved at 82◦C. The catalytic conver-
sions become notably slower when the temperature is decreased.
In general, although both catalysts were effective for TH of ke-
tones, 1a is much more active catalyst than 2a. RuII complexes
are more efficient catalyst for electron withdrawing substituent
such as F-, Cl-, and Br- on the para position of the aryl ring
of the acetophenone derivatives. These results are consistent
with other researchers.[20,21] When the electron donating group
is introduced at the aryl ring of the ketone, catalytic activity
decreases. A plausible mechanism has been proposed for the
previously described results (Figure 2).
FIG. 2. Proposed mechanism for transfer hydrogenation of arylketones cat-
alyzed Ruthenium complexes in the presence of KOH in 2-propanol.

960
Z. SERBETCI
4-dithiobiurets and 1,5-diaryl-substituted 2-thiobiurets and their semicon-
1.6x1010
ducting properties J. Chern., Eng. Data 1980, 25, 173–175.
5. Yakuphanoglu, F.; Sekerci, M.; Evin, E. The determination of the conduc-
tion mechanism andoptical band gap of fluorescein sodium salt. Phys. B
2006, 382, 21–25.
1a sample
2a sample
1.4x1010
1.2x1010
1.0x1010
8.0x109
6.0x109
4.0x109
2.0x109
6. Shriver, D.F.; Atkins, P.W. Inorg. Chem. 1999, 585.
7. Dayan, O.; Cetinkaya, B. Mono- and binuclear ruthenium (II) complexes
containing pyridine-2,6-diimine (Pydim) ligands: synthesis, characteriza-
tion and catalytic activity in the transfer hydrogenation of acetophenone. J.
Mol. Catal. A–Chem. 2007, 271, 134–141.
8. Cetin, A.; Dayan, O. Transfer hydrogenation of acetophenone catalyzed by
in situ generated 2,6-bis(5-thioxo-4,5-dihydro-1,2,4-triazole-3-yl)pyridine-
ruthenium(II) complexes. Chin. J. Chem. 2009, 27, 1–10.
9. Clercq, B.D.; Verpoort, F. A new class of ruthenium complexes contain-
ing Schiff base ligands as promising catalysts for atom transfer radical
polymerization and ring opening metathesis polymerization. J. Mol. Catal.
A–Chem. 2002, 180, 67–76.
20
40
60
80
100
120
Temperature (oC)
10. Clercq, B.D.; Verpoort, F. Synthesis and evaluation of a new class of
ruthenium-based catalytic systems for atom transfer radical addition and
enol ester synthesis. J. Organomet. Chem. 2003, 672, 11–16.
11. Aydemir, M.; Baysal, A.; Meric, N.; Gu¨mgu¨m, B. New ac-
tive ruthenium(II) complexes based N3,N3ꢁ-bis(diphenylphosphino)-2,2ꢁ-
bipyridine-3,3ꢁ-diamine and P,Pꢁ-diphenylphosphinous ester ligands for
transfer hydrogenation of aromatic ketones by propan-2-ol acid-P,Pꢁ-
[2,2ꢁ-bipyridine]-3,3ꢁ-diyl. J. Organomet. Chem. 2009, 694, 2488–
2492.
12. Bennett, M.A.; Smith, A.K. Arene ruthenium(II) complexes formed by
dehydrogenation of cyclohexadienes with ruthenium (III) trichloride. J.
Chem. Soc., Dalton Trans. 1974, 233.
13. Bennett, M.A.; Huang, T.N.; Matheson, T.W.; Smith, A.K. (η6-
hexamethylbenzene) ruthenium complexes. Inorg. Synth. 1982, 21, 74.
14. Cetin, A.; Cansız, A. Synthesis characterization of some compounds includ-
ing rings of 1,3,4-oxadiazoale, 1,3,4-thiadiazole, and 1,2,4-triazol. Fırat
University Graduate School of Natural and Applied Sciences Department
of Chemistry, Elazig, Turkey, 2004.
FIG. 3. Plots of electrical resistance vs. temperature of the samples.
Semiconductive Properties
Figure 3 shows the curves of electrical resistance of the sam-
ples. As seen in Figure 2, the electrical resistance of the samples
is decreased up to 70◦C and then is increased with tempera-
ture. The electrical conductivity of 2a sample is higher than that
of 1a sample. The difference in electrical conductivities of the
samples is resulted from the chemical structure. The obtained
results indicate that the studied samples exhibit the semicon-
ductive properties.
CONCLUSIONS
In this work, we reported the preparation and characterization
of novel Ru(II) complexes (1a and 2a) containing pyridine-
based ligands and their catalytic activities for the hydrogen
transfer reaction of acetophenone derivatives with the use of
2-propanol in the presence of KOH. Catalytic reactions show
that 1a is more efficient catalyst than 2a for TH of simple ke-
tones. The efficiency of the catalyst seems to depend on the
ligands of complexes and the substituents of acetophenone.
The complexes [Ru(L1–2)(p-cymene)Cl2] exhibits the con-
ducting behavior, as the conductivity of the samples is increased
with the increase in temperature. In the 2a and 1a study of the
catalytic complex, the complex activity were found to be higher
than the yield.
15. Cetin, A. Accelerated synthesis of novel accelerated synthesis of novel
1,2,4-triazolo[3,4-b] [1,3,4] thiadiazepines under microwave irradiation.
Heterocyclic 2006, 68, 1901–1907
16. Liu, Y.J.; Zenga, C.H.; Huang, H.L.; He, L.X.; Wu, F.H. Synthesis, DNA-
binding, photocleavage cytotoxicity and antioxidant activity of ruthe-
nium (II) polypyridyl complexes. Eur. J. Med. Chem. 2010, 45, 564–
571
17. Nakajima, K.; Ishibashi, S.; Inamo, M.; Kojima, M. Thermal and
photo substitution reactivity and crystal structures of tridentate Schiff
base–ruthenium(II) complexes containing phosphorus or sulfur donor
atoms. Inorg. Chim Acta 2001, 325, 36–44
18. Pearson, P.; Bond, A.M.; Deacon, G.B.; Forsyth, C.; Spiccia, L. Syn-
thesis and characterisation of bis(2,2’-bipyridine)- (4-carboxy-40-(pyrid-
2-ylmethylamido) 2,2’-bipyridine)-ruthenium(II) di(hexafluorophosphate):
comparison of spectroelectrochemical properties with related complexes.
Inorg. Chim. Acta 2008, 361, 601–612
19. Aydemir, M.; Durap, F.; Baysal, A.; Meric, N.; Buldag˘, A.; Gu¨mgu¨m,
¨
REFERENCES
B.; Ozkar, S.; Yıldırım, L.T. Novel neutral bis(phosphinite) bridged dinu-
1. Yakuphanoglu, F. Photovoltaic properties of the organic–inorganic pho-
todiode based on polymer and fullerene blend for optical sensors. Sens.
Actuators, A 2008, 141, 383–389.
2. Singh, N.; Gupta, S. Solid state electrical conductance properties of some
new bimetallic salts and heterometallic coordination polymers derived
from bis (1-ethoxycarbonyl-1-cyanoethylene-2,2-dithiolato) cuprate(II)
ion. Synth. Met. 1999, 107, 167–174.
3. Singh, N.; Singh, V.K. Electrical properties of complex bimetallic
salts [M(N–N)3]2+[Cu(MNT)2]2- and heterobimetallic AgI–CuII/HgII–CuII
bis(maleonitriledithiolato) bridged coordination polymers. Int. J. Inorg.
Mater. 2000, 2, 167–175.
4. Srivastava, K.P.; Srivastava, G.P.; Arya, S.K.; Madhok, K.L. Synthe-
sis of niobium pentachloride complexes with 1,5-diaryl-substituted 2,
clear ruthenium(II) arene complexes and their application in transfer hy-
drogenation of aromatic ketones: X-ray structure of a new Schiff base,
N3,N3ꢁ-di-2-hydroxybenzylidene-[2,2’]bipyridinyl-3,3ꢁ-diamine. J. Mol.
Catal. A–Chem. 2010, 326, 75–81.
20. Faller, J.W.; Lavoie, A.R. Catalysts for the asymmetric transfer-
hydrogenation of ketones derived from (L)-prolinamide and
(cymeneRuCl2)2 or (Cp∗RhCl2)2. Organometallics 2001, 20, 5245–
5247.
21. Pelagatti, P.; Carcelli, M.; Calbiani, F.; Cassi, C.; Elviri, L.; Pelizzi, C.; Riz-
zotti, U.; Rogolino, D. Transfer hydrogenation of acetophenone catalyzed
by half-sandwich ruthenium (II) complexes containing amino amide lig-
ands. Detection of the catalytic intermedidates by electrospray ionization
mass spectrometry. Organometallics 2005, 24, 5836–5844.