Heterocyclic-2-thione derivatives of silver(I): Synthesis, spectroscopy and structures of mono- and di-nuclear silver(I) halide complexes

Article abstract of DOI:10.1016/j.jorganchem.2013.08.020

The scarcely known chemistry of silver(I) halides with a series of heterocyclic thiones in acetonitrile (or methanol-acetonitrile) is described. Silver(I) chloride with a series of imidazolidine-2-thiones [C₃H ₅NS(N-R)] in the presence of one equivalent of PPh₃ with respect to the thione ligand has yielded chloro-bridged dinuclear complexes, [Ag₂(μ-Cl)₂(κ¹-S-C₃H ₅NS(N-R))₂(PPh₃)₂] (1, R = H; 2, R = Me; 3, R = Et), and in the presence of two equivalents of PPh₃, it has yielded mononuclear complexes, [Ag(κ¹-Cl) (κ¹-S-C₃H₅NS(N-R))(PPh₃) ₂] (4, R = Me; 5, R = Et). The n-propyl-imidazolidine-2-thione with silver(I) chloride formed only a mononuclear complex, [Ag(κ¹- Cl)(κ¹-S-C₃H₅NS(N-Prⁿ)) (PPh₃)₂] (6), in the presence of one or two equivalents of PPh₃. In contrast, silver(I) bromide with C₃H ₅NS(N-R) in the presence of one or two equivalents of PPh₃ with respect to the thione ligand has yielded bromide-bridged dinuclear complexes, [Ag₂(μ-Br)₂(κ¹-S-C ₃H₅NS(N-R))₂(PPh₃)₂] (7, R = Me; 8, R = Et; 9, R = Prⁿ). The related thio-ligands, namely, 1-methyl-imidazoline-2-thione and thiazolidine-2-thione with silver(I) bromide in the presence of one or two equivalents of PPh₃ have formed bromide bridged dimeric [Ag₂(μ-Br)₂(κ¹-S- C₃H₃NS(N-Me))₂(PPh₃)₂] (10) or mononuclear Ag(κ¹-Br)(κ¹-S-C ₃H₅NS₂)(PPh₃)₂] (11) complexes respectively. The 2,4-dithiouracil (C₄H₄N ₂S₂) with silver(I) chloride/bromide and PPh₃ has yielded hetero-bridged dinuclear complexes, [Ag₂(μ-S,S-C ₄H₃N₂S₂)(μ-X)(PPh ₃)₄] (X = Cl, 12; Br, 13) involving rupture of Ag-X bonds directly with a thio-ligand, a rare case of such rupture in metal-heterocyclic thione chemistry.

Full text of DOI:10.1016/j.jorganchem.2013.08.020

Journal of Organometallic Chemistry 745-746 (2013) 460e469
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Heterocyclic-2-thione derivatives of silver(I): Synthesis, spectroscopy
and structures of mono- and di-nuclear silver(I) halide complexes
,
a
b
c
c
Tarlok S. Lobana a , Razia Sultana , Ray J. Butcher , Jerry P. Jasinski , James A. Golen ,
*
Alfonso Castineiras d, Kevin Pröpper e, Francisco J. Fernandez f, M. Cristina Vega f
a Department of Chemistry, Guru Nanak Dev University, Amritsar 143 005, India
b Department of Chemistry, Howard University, Washington, DC 20059, USA
c Department of Chemistry, Keene State College, 229 Main Street, Keene, NH 03435-2001, USA
d Departamento de Quimica Inorganica, Facultad de Farmacia, Universidad de Santiago, 15782 Santiago, Spain
e University Goettingen, Dept. of Structural Chemistry, Tammannstrasse, 437077 Goettingen, Germany
f Department of Structural and Quantitative Biology, Center for Biological Research (C. I. BeCSIC), Ramiro de Maeztu 9, E-28040 Madrid, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
The scarcely known chemistry of silver(I) halides with a series of heterocyclic thiones in acetonitrile (or
Received 4 July 2013
Received in revised form
7 August 2013
methanoleacetonitrile) is described. Silver(I) chloride with
a series of imidazolidine-2-thiones
[C3H5NS(NeR)] in the presence of one equivalent of PPh3 with respect to the thione ligand has yiel-
ded chloro-bridged dinuclear complexes, [Ag2(
m
-Cl)2(
k
1-S-C3H5NS(NeR))2(PPh3)2] (1, R ¼ H; 2, R ¼ Me;
Accepted 9 August 2013
3, R ¼ Et), and in the presence of two equivalents of PPh3, it has yielded mononuclear complexes, [Ag(k1
-
Cl)(
k
1-S-C3H5NS(NeR))(PPh3)2] (4, R ¼ Me; 5, R ¼ Et). The n-propyl-imidazolidine-2-thione with silver(I)
Keywords:
Silver(I)
chloride formed only a mononuclear complex, [Ag(k k
1-Cl)( 1-S-C3H5NS(NePrn))(PPh3)2] (6), in the pres-
ence of one or two equivalents of PPh3. In contrast, silver(I) bromide with C3H5NS(NeR) in the presence
Imidazolidine-2-thione
Thiazolidine-2-thione
Imidazoline-2-thione
2,4-Dithiouracil
Triphenyl phosphine
of one or two equivalents of PPh3 with respect to the thione ligand has yielded bromide-bridged
dinuclear complexes, [Ag2(
related thio-ligands, namely, 1-methyl-imidazoline-2-thione and thiazolidine-2-thione with silver(I)
m
-Br)2(
k
1-S-C3H5NS(NeR))2(PPh3)2] (7, R ¼ Me; 8, R ¼ Et; 9, R ¼ Prn). The
bromide in the presence of one or two equivalents of PPh3 have formed bromide bridged dimeric [Ag2(
Br)2(
1-S-C3H3NS(NeMe))2(PPh3)2] (10) or mononuclear Ag( 1-Br)( 1-S-C3H5NS2)(PPh3)2] (11) com-
plexes respectively. The 2,4-dithiouracil (C4H4N2S2) with silver(I) chloride/bromide and PPh3 has yielded
hetero-bridged dinuclear complexes, [Ag2( -S,S-C4H3N2S2)(
m-
k
k
k
m
m
-X)(PPh3)4] (X ¼ Cl, 12; Br, 13) involving
rupture of AgeX bonds directly with a thio-ligand, a rare case of such rupture in metal-heterocyclic
thione chemistry.
Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction
activity against a wide variety of viruses [12,13]. The molecular
design and structural characterization of silver(I) complexes is
Coordination chemistry of heterocyclic thiones, bearing the
chemically active groups, eN(H)eC(]S)e 4 eN]C(eSH)e or e
N(H)eC(]S)eN(H)e 4 eN]C(eSH)eN(H)e, has been intensively
explored [1e8]. Silver(I) complexes with sulfur-containing ligands
have shown a wide range of applications in medicine, in analytical
chemistry, and in polymer industry [9,10]. The biomedical appli-
cations and uses of silver(I) complexes are related to their anti-
bacterial action [11]. Silver(I) complexes with heterocyclic thiones
were found to be cytotoxic against murine leukemia (L1210), and
human T-lymphocyte (Molt4/C8 and CEM) cells, and antiviral
therefore an intriguing aspect of metal-based drugs [14,15].
Coordination chemistry of copper(I) halides with several het-
erocyclic thioamides has been intensively explored unlike that of
silver(I) halides [1e6]. As regards silver(I) halides, the complexes
reported with PPh3 as co-ligand are enumerated as follows:
mononuclear [AgCl(
k
1-S-L)(PPh3)2] {L ¼ pyridine-2-thione, C5H5NS
[16], C3H5NS(NeH), R ¼ H, structure I; C3H3NS(NeMe), structure II,
and C3H5NS2, structure III [17]} halogen-bridged dimer [Ag2(m-
Br)2(
k
1-S-L)2(PPh3)2] (L ¼ pyrimidine-2-thione) [18] and sulfur-
bridged dimers [Ag2(
k
1-X)2(
m
-S-L)2(PPh3)2] {L ¼ C5H5NS, Cl, Br}
[19]. Without a co-ligand, a mononuclear [Ag(
H))3Cl] [20], [Ag2(
1-S-C3H5NS(NeH))6](SO4) [20], a few dinuclear
[Ag2( -S-C3H5NS(NeH))2(
1-S-C3H5NS(NeH))4](NO3)2 [20], Ag2(k1
S-C3H5NS(NeH))4( -Br)2] [20,21], and a few polynuclear [Ag(
1-S-
k
1-S-C3H5NS(Ne
k
m
k
-
* Corresponding author. Fax: þ91 183 2 258820.
m
k
E-mail addresses: tarlokslobana@yahoo.co.in, tslasr@gmail.com (T.S. Lobana).
0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2013.08.020

T.S. Lobana et al. / Journal of Organometallic Chemistry 745-746 (2013) 460e469
461
C3H5NS(NeH))(
m
-S-C3H5NS(NeH))Cl]n [22a], [Ag2(
m
-S-C3H3NS(Ne
1439(sh),
n
(CeN) þ
d
(CeH); 1186(s),
n
(C]S); 1108(w), 986(m),
Me))(m3-I)2]n [22b] and {Ag(C5H5NS)Cl}n complexes have been re-
ported. Further, coordination chemistry of 2,4-dithiouracil
(C4H4N2S2, structure IV) is limited and there are only a few struc-
turally characterized complexes of CoIII, TiIII, RuII and CuI [17,23,24].
In view of our interest in the development of coordination
chemistry of silver(I) halides, we have reported complexes with a
few heterocyclic thioamides [17,19] and related N, S-donor ligands,
namely, thiosemicarbazones [25]. In this paper, reactions of silver(I)
halides (X ¼ Cl, Br) with a series of heterocyclic-2-thiones as shown
in Chart 1 [structures I (R ¼ H, Me, Et, Prn), II, III and IV] have been
carried out in the presence of PPh3 as co-ligand and the resulting
complexes characterized using analytical data, IR and multinuclear
NMR spectroscopy (1H and 31P) and single crystal X-ray crystal-
lography (1e4, 6e13).
915(m), n d ppm): 7.79 (s, 1H, NH),
(PeCPh). 1H NMR data (CDCl3,
7.26e7.44 (m, 16H, PPh3 þ CHCl3). 3.73 (s, 4H, C4,5H).
2.2.2. [Ag2(m-Cl)2(k
1-S-C3H5NS(NeMe))2(PPh3)2] 2
It was prepared by the method used for complex 1 (Yield 67%,
mp. 161e164 ꢁC). Found: C, 51.18; H, 4.52; N, 5.38. Calc. for
C
45H48Ag2Cl2N4P2S2: C, 51.06; H, 4.54; N, 5.29%. IR absorptions (
cmꢀ1): 3178(m),
(NeH); 3065e2880(w), (CeH); 1513(s),
1478(sh), (CeH); 1192(m), (C]S); 1093(s), (PeCPh);
(CeN) þ
958(w), ppm): 9.14 (s, 1H, NH),
(NeCH3). 1H NMR data (CDCl3,
7.50e7.33 (m, 15H, PPh3), 3.70 (d, 4H, C4,5H), 3.10 (s, 3H, CH3).
n/
n
n
n
d
n
n
d
d
2.2.3. [Ag2(m-Cl)2(k
1-S-C3H5NS(NeEt))2(PPh3)2] 3
It was prepared by a method used for complex 1 (Yield 66%, mp.
165e167 ꢁC). Found: C, 51.35; H, 4.61; N, 5.14. Calc. for
C
46H50Ag2Cl2N4P2S2: C, 51.51; H, 4.66; N, 5.22%. IR absorptions (n/
2. Experimental section
cmꢀ1): 3202(m),
1478(sh),
(CeN) þ
NMR data (CDCl3,
C4,5H, NeCH2), 1.20 (t, 3H, CH3).
n
(NeH); 3051e2885(w),
n
(CeH); 1516(s),
n
d(CeH); 1187(m),
n
(C]S); 1094(s),
n
(PeCPh). 1H
2.1. Materials and techniques
d
ppm): 7.50e7.39 (m, 15H, PPh3), 3.63 (m, 6H,
Silver(I) halides were freshly prepared from AgNO3 and potas-
sium halides (X ¼ Cl, Br) in methanol and dried in vacuo. Imida-
zolidine-2-thione, thiazolidine-2-thione, 1-methyl-imidazoline-2-
thione and 2,4-dithiouracil were procured from Aldrich Chem-
icals Ltd. and used as such. The N-alkyl-imidazolidine-2-thiones (1-
methyl-imidazolidine-2-thione, 1-ethyl-imidazolidine-2-thione, n-
2.2.4. [AgCl(k
1-S-C3H5NS(NeMe))(PPh3)2] 4
To silver(I) chloride (0.025 g, 0.17 mmol) suspended in aceto-
nitrile was added solid PPh3 (0.091 g, 0.34 mmol), and the contents
were stirred for 24 h. The white solid formed was filtered and dried
in vacuo. To this solid suspended in chloroform was added solid 1-
methyl-imdazolidine-2-thione (0.020 g, 0.17 mmol) and the con-
tents were stirred until a clear solution was obtained, which was
allowed to evaporate at room temperature. The solid obtained was
dissolved in dichloromethane and acetonitrile mixture. Slow
evaporation of the solution resulted in colorless crystals of 4 (Yield
68%, mp. 165e167 ꢁC). Found: C, 61.40; H, 4.95; N, 3.62. Calc. for
propyl-imidazolidine-2-thione
and
n-butyl-imidazolidine-2-
thione) were prepared as per the literature methods [26]. The C,
H and N analyses were obtained with Thermoelectron FLASHEA
1112 CHNS analyzer. The IR spectra were recorded using KBr pellets
in the range 4000e400 cmꢀ1 on Varian 660-IR Fourier transform
infrared spectrophotometer. The melting points were determined
with a Gallenkamp electrically heated apparatus. The 1H NMR
spectra were recorded on a JEOL AL300 FT spectrometer at 300 MHz
in CDCl3 with TMS as the internal reference. The 31P NMR spectra
were recorded on BRUKER AVANCE II 400 spectrometer operating
at a frequency of 161.9 MHz using o-phosphoric acid as the external
reference set at zero position.
C
40H38AgClN2P2S: C, 61.26; H, 4.85; N, 3.57%. IR absorptions (n/
cmꢀ1): 3212m (br),
n
(NeH); 3066e2799(m),
n
(CeH); 1515(s),
1479(s),
996(w),
n
(CeN) þ
d
(CeH); 1180(m),
n
(C]S); 1093(m), n(PeCPh);
d
(NeCH3). 1H NMR data (CDCl3,
d ppm): 8.64 (s, 1H,
NH), 7.42e7.26 (m, 16H, PPh3 þ CHCl3), 3.61 (m, 4H, C4,5H), 3.08 (m,
3H, CH3).
2.2. Synthesis of complexes
2.2.5. [AgCl(k
1-S-C3H5NS(NeEt)(PPh3)2)] 5
2.2.1. [Ag2(m-Cl)2(k
1-S-C3H5NS(NeH))2(PPh3)2] 1
It was prepared by a method used for complex 4 (Yield 66%, mp.
151e154 ꢁC). Found: C, 61.55; H, 4.95; N, 3.62. Calc. for
C
To silver(I) chloride (0.025 g, 0.17 mmol) suspended in aceto-
nitrile was added solid PPh3 (0.045 g, 0.17 mmol) and the contents
were stirred for 24 h. The white solid formed was filtered and dried
in vacuo. To this solid suspended in chloroform was added solid
imdazolidine-2-thione (0.018 g, 0.17 mmol) and the contents were
stirred until a clear solution was obtained, which was allowed to
evaporate at room temperature. The solid obtained was dissolved in
dichloromethane and acetonitrile mixture. A slow evaporation of
the solution resulted in colorless crystals of complex 1 (Yield 70%,
mp. 163e165 ꢁC). Found: C, 49.54; H, 4.16; N, 6.07. Calc. for
41H40AgClN2P2S: C, 61.71; H, 5.01; N, 3.51%. IR absorptions (n/
cmꢀ1): 3202(m),
1478(m),
(CeN) þ
NMR data (CDCl3,
n
(NeH); 3050e2885(m),
n
(CeH); 1517(s),
n
d
(CeH); 1193(m),
d
PPh3 þ CHCl3). 3.58 (m, 6H, C4,5H, NeCH2), 1.17 (m, 3H, CH3).
n
(C]S); 1094(m),
n
(PeCPh). 1H
ppm): 8.60 (s, 1H, NH), 7.70e7.26 (m, 16H,
2.2.6. [AgCl(k
1-S-C3H5NS(NePrn)(PPh3)2)] 6
It was prepared by a method used for complex 1 (Yield 67%, mp.
150e153 ꢁC). Found: C, 61.95; H, 5.10; N, 3.48. Calc. for
C
42H42AgClN2P2S: C, 62.11; H, 5.17; N, 3.45%. IR absorptions (
cmꢀ1): 3092(w),
(NeH); 3051e2871(m), (CeH); 1511(s),
1479(sh), (CeH); 1186(m), (C]S); 1094(m), (PeCPh).
(CeN) þ
n/
C
21H21AgClN2PS: C, 49.70; H, 4.14; N, 5.52%. IR absorptions (
n/
cmꢀ1): 3150(m),
n
(NeH); 3040e2865(w), (CeH); 1509(s),
n
n
n
n
d
n
n
1H NMR data (CDCl3,
d ppm): 7.43e7.26 (m, 16H, PPh3, CHCl3). 3.61
(m, 4H, C4H, NeCH2), 3.49 (t, 2H, C5H), 1.55 (m, 2H, eCH2), 0.87 (t,
6
4
5
5
5
4
4
1
NH
5
3H, CH3).
1
1
NR
N1H
HN3
HN 3
NMe
3S
4
2
3
2.2.7. [Ag2(m-Br)2(k
1-S-C3H5NS(NeMe))2(PPh3)2] 7
2
2
2
N
S
S
To silver(I) bromide (0.025 g, 0.13 mmol) suspended in aceto-
nitrile was added solid PPh3 (0.070 g, 0.26 mmol) and the contents
were stirred for 24 h. The white solid formed was filtered and dried
in vacuo. To this solid suspended in chloroform was added solid
1-methyl-imdazolidine-2-thione (0.016 g, 0.13 mmol) and the
H
S
II
S
S
I
IV
III
Chart 1. Various thio-ligands used.

462
T.S. Lobana et al. / Journal of Organometallic Chemistry 745-746 (2013) 460e469
CH3CN
[AgX(PPh3)n]
X
AgX
+
nPPh3
N-R
S
Ph3P
Ag
Ag
X
a
PPh3
S
R-N
CHCl3
2 ( R = Me) 3 ( R= Et)
[AgX(PPh3)n]
1 ( R = H)
+
S
N-R
7 ( R = Me) 8 ( R = Et) 9 ( R = Prn)
10
b
X
CHCl3
6 (R = Prn)
Ag
4 (R = Me) 5 (R = Et)
PPh3
PPh3
11
S
R-N
=
N-R
HN
N-R
S
HN
NMe
HN
S
S
S
S
11
1- 9
10
Scheme 1. Formation of complexes 1e11.
contents were stirred until a clear solution was obtained, which
was allowed to evaporate at room temperature. The solid obtained
was dissolved in dichloromethane and acetonitrile mixture. A slow
evaporation of the solution resulted in colorless crystals of 7 (Yield
69%, mp. 170e173 ꢁC). Found: C, 46.77; H, 3.94; N, 5.10. Calc. for
2.2.10. [Ag2(m-Br)2(k
1-S-C3H3NS(NeMe))2(PPh3)2] 10
It was prepared by a method used for 7 (Yield 67%, mp. 163e
165 ꢁC). Found: C, 47.65; H, 3.81; N, 5.14. Calc. for C39H35AgClNP2S2:
C, 46.80; H, 3.72; N, 4.96%. IR absorptions (
H); 3052e2883(w), (CeH); 1514(s), 1479(s),
920(m), (C]S); 1093(w), (PeCPh); 748(s),
(NeCH3). 1H NMR data
, ppm; CDCl3): 7.52e7.39 (m, 15H, PPh3). 6.75 (t, 1H, C4H), 6.64 (t,
1H, C5H), 3.54 (s, 3H, NeCH3).
n
/cmꢀ1): 3243(s),
n
(Ne
n
n
(CeN) þ
d(CeH);
C
21H21AgBrN2PS: C, 46.64; H, 4.06; N, 4.95%. IR absorptions (
cmꢀ1): 3243(m),
(NeH); 3051e2883(m), (CeH); 1514(s),
1479(sh), (CeH); 1186(m), (C]S); 1114(s), (PeCPh);
(CeN) þ
945(w), ppm): 8.16 (s, 1H, NH),
(NeCH3). 1H NMR data (CDCl3,
7.49e7.32 (m, 15H, PPh3), 3.69 (m, 4H, C4,5H), 3.10 (s, 3H, CH3).
n
/
n
n
d
n
n
(d
n
d
n
n
d
d
2.2.11. [Ag(
k
1-Br)( 1-S-C3H5NS2)(PPh3)2] 11
k
It was prepared by a method used for 4 (Yield 72%, mp. 170e
2.2.8. [Ag2(
m
-Br)2(
k
1-S-C3H5NS(NeEt))2(PPh3)2] 8
173 ꢁC). Found: C, 56.54; H, 4.05; N, 1.62. Calc. for C39H35AgBrNP2S2:
It was prepared by a method used for complex 7 (Yield 71%, mp.
C, 56.31; H, 4.21; N,1.68%. IR absorptions (n
/cmꢀ1): 3052(m), 3008e
158e160 ꢁC). Found: C, 47.54; H, 4.41; N, 4.82. Calc. for
2811(m),
1093(m),
n
(NeH);
n
(CeH); 1527(s), 1479(s),
n
(CeN) þ
d
(CeH);
ppm):
C
46H52Ag2Br2N4P2S2: C, 47.48; H, 4.47; N, 4.82%. IR absorptions (
n
/
n
(PeCPh); 996(m),
n
(C]S). 1H NMR data (CDCl3,
d
cmꢀ1): 3237(m),
1477(sh),
(CeN) þ
n
(NeH); 3050e2883(w),
n
(CeH); 1514(s),
9.72 bs (1H, NH), 7.43e7.26 (m, 16H, PPh3 þ CHCl3), 3.47 (t, 2H,
n
d
(CeH); 1187(m),
n(C]S); 1093(m),
n
(PvCPh). 1H
C4H), 3.94 (t, 2H, C5H).
NMR data (CDCl3,
d
ppm): 8.45 (s, 1H, NH), 7.50e7.24 (m, 16H,
PPh3 þ CHCl3), 3.61 (m, 6H, C4,5H, NeCH2), 1.19 (m, 3H, CH3).
2.2.12. [Ag2(m-S,S-C4H3N2S2)(m-Cl)(PPh3)4] 12
To silver(I) chloride (0.025 g, 0.17 mmol) suspended in aceto-
nitrile was added solution of 2,4-dithiouracil in methanol (0.025 g,
0.17 mmol) and the contents were stirred for 48 h. To the yellow
precipitates formed was added solid PPh3 (0.091 g, 0.17 mmol) and
2.2.9. [Ag2(m-Br)2(k
1-S-C3H5NS(NePrn))2(PPh3)2] 9
It was prepared by a method used for 7 (Yield 69%, mp. 140e
142 ꢁC). Found: C, 48.53; H, 4.50; N, 4.62. Calc. for
C
48H54Ag2Br2N4P2S2: C, 48.46; H, 4.54; N, 4.71%. IR absorptions (
cmꢀ1): 3235(m),
(NeH); 3053e2882(w), (CeH); 1513(s),
1477(sh), (CeH); 1184(m), (C]S); 1093(m), (PeCPh).
(CeN) þ
n/
n
n
Table 1
n
d
n
n
31P NMR data (CDCl3,
d
in ppm) of complexes.
Dd dC dL
1H NMR data (CDCl3,
d ppm): 8.50 bs (1H, NH), 7.51e7.29 (m, 15H,
PPh3), 3.67 (m, 4H, C4H, NeCH2), 3.47 (t, 2H, C5H), 1.60 (m, 2H, CH2),
Complex
dP
¼
ꢀ
Dd
¼
dC
ꢀ
dL
Remarks
(second species)
0.92 (t, 3H, CH3).
1
2
3
4
5
6
7
9
10
11
12
13
13.62
19.10
34.75
35.08
9.25
15.69
10.00
34.00
12.60
15.28
7.10
e
Single species
Two species
Two species
Single species
Single species
Single species
Two species
Single species
Single species
Single species
Two species
Two species
4.64, 29.30
3.40, 29.63
3.78
10.22
4.54
6.40, 28.59
7.13
10.58
2.42
2.62, 29.20
2.70, 29.33
10.09
8.85
e
N
e
e
2
S
N
H
CH3CN - CH3OH
HN
1S
+
2AgX
11.87
e
+
4PPh3
1
2
-2HX
N
H
Ag
Ag
S
S
e
PPh3
X
Ph3P
e
PPh3
PPh3
8.12
8.20
34.70
34.80
Scheme 2. Dithiouracilates of silver(I), X ¼ Cl, 12; Br, 13.

T.S. Lobana et al. / Journal of Organometallic Chemistry 745-746 (2013) 460e469
463
Table 2
Crystallographic data for complexes 1e4, 6e13.
1
2
3
4
Empirical formula
Formula weight
T(K)
C42H42Ag2Cl2 N4P2S2
C44H46Ag2Cl2N4P2S2
1043.55
173(2)
Triclinic
P-1
9.226(1)
10.180(1)
13.253(1)
78.590(4)
76.163(4)
69.983(5)
1126.44(1)
1
C46H50Ag2Cl2N4P2S2
1071.60
170(2)
Triclinic
P-1
9.176(1)
10.3026(1)
13.473(1)
80.514(7)
75.593(8)
69.996(10)
1154.8(2)
1
C40H38AgClN2P2S
784.04
123(2)
Monoclinic
P21/c
14.3440(2)
10.236(2)
24.799(1)
90
92.018(1)
90
3638.77(9)
4
1.431
0.804
1015.50
295(2)
Monoclinic
P21/n
8.855(1)
15.748(1)
15.452(1)
90
97.853(6)
90
2134.4(2)
2
Crystal system
Space group
ꢀ
a(A)
ꢀ
b(A)
ꢀ
c(A)
a
(ꢁ)
(ꢁ)
b
g
(ꢁ)
3
ꢀ
V (A )
Z
Dcalcd (g cmꢀ3
)
1.580
1.251
1.538
1.187
1.541
1.160
m
(mmꢀ1
)
Total reflections
Unique reflections, Rint
R (reflections)
R1
17,962
8112, 0.0456
10,234
5788, 0.0125
11,764
6479, 0.0295
39,833
18,259, 0.0284
0.0518 (5267)
0.0980 (8112)
0.0277 (5078)
0.0783 (5788)
0.0372 (5234)
0.0950 (6479)
0.0368 (14,826)
0.0780 (18,259)
wR2
6
7
8
Empirical formula
Formula weight
T(K)
C
42H42AgClN2P2S
C44H46Ag2Br2N4 P2S2
1132.47
173(2)
C46H52Ag2Br2N4P2S2
1162.54
295(2)
812.10
170(2)
Crystal system
Space group
Triclinic
P-1
Triclinic
P-1
Triclinic
P-1
ꢀ
a(A)
10.415(1)
13.036(1)
15.075(1)
76.858(6)
81.323(6)
76.605(6)
1928.4(2)
2
9.358(1)
10.259(1)
13.313(1)
77.368(8)
75.297(9)
69.256(10)
1144.3(2)
1
9.371(1)
10.432(1)
13.504(1)
80.323(5)
75.154(5)
69.947(6)
1193.94(12)
1
ꢀ
b(A)
ꢀ
c(A)
a
(ꢁ)
(ꢁ)
b
g
(ꢁ)
3
ꢀ
V (A )
Z
Dcalcd (g cmꢀ3
)
1.399
0.761
1.643
2.798
1.617
2.684
m
(mmꢀ1
)
Reflections collected
Unique reflections, Rint
R (reflections)
R1
18,550
9923, 0.0196
10,324
5882, 0.0185
16,844
9665, 0.0375
0.0312 (8598)
0.0816 (9923)
0.0295 (5012)
0.0789 (5882)
0.0654 (5058)
0.1965 (9665)
wR2
9
10
11
Empirical formula
Formula weight
T(K)
C
48H54Ag2Br2N4P2S2
C44H42Ag2Br2N4P2S2
1128.44
295(2)
C39H35AgBrNP2S2
831.52
296(2)
1188.57
295(2)
Crystal system
Space group
Triclinic
P-1
Triclinic
P-1
Monoclinic
P21/c
13.987(3)
10.459(2)
24.806(5)
90
95.03(3)
90
3614.9(13)
8
ꢀ
a(A)
9.640(1)
10.5045(3)
13.4030(5)
80.299(3)
75.033(4)
70.554(4)
1231.27(9)
1
9.379(1)
10.273(1)
13.383(1)
77.297(6)
75.270(7)
69.366(7)
1154.92(15)
1
ꢀ
b(A)
ꢀ
c(A)
a
(ꢁ)
(ꢁ)
b
g
(ꢁ)
3
ꢀ
V (A )
Z
Dcalcd (g cmꢀ3
)
1.603
2.604
1.622
2.772
1.528
7.901
m
(mmꢀ1
)
Reflections collected
Unique reflections, Rint
R (reflections)
R1
15,636
8124, 0.0267
21,255
11,535, 0.0742
65,346
5541, 0.0341
0.0395 (6102)
0.0950 (8124)
0.0576 (3852)
0.1463 (11,535)
0.0226 (5437)
0.0586 (5541)
wR2
12
13
Empirical formula
Formula weight
T(K)
C76H63Ag2ClN2P4S2
1443.47
100(2)
C76H63Ag2BrN2P4S2
1487.93
100(2)
Crystal system
Space group
Triclinic
P-1
11.976(1)
14.057(1)
Triclinic
P-1
11.998(1)
14.106(1)
ꢀ
a(A)
ꢀ
b(A)
(continued on next page)

464
T.S. Lobana et al. / Journal of Organometallic Chemistry 745-746 (2013) 460e469
Table 2 (continued )
12
13
ꢀ
c(A)
a
19.928(1)
97.961(5)
91.637(3)
96.251(5)
3299.5(5)
2
19.963(1)
98.070(2)
91.384(2)
96.122(2)
3323.6(3)
2
(ꢁ)
(ꢁ)
b
g
(ꢁ)
3
ꢀ
V (A )
Z
Dcalcd (g cmꢀ3
)
1.453
0.840
1.487
1.395
m
(mmꢀ1
)
Reflections collected
Unique reflections, Rint
R (reflections)
R1
282,780
15,097, 0.0522
149,552
13,064, 0.0531
0.0734 (15,063)
0.1913 (15,097)
0.0698 (8984)
0.1136 (13,064)
wR2
the contents were stirred until reaction solution becomes clear. The
slow evaporation of the solution resulted in yellow prismatic
crystals of 12 (Yield 68%, mp. 170e172 ꢁC). Found: C, 63.42; H, 4.22;
N, 2.05. Calc. for C76H63Ag2ClN2P4S2: C, 63.18; H, 4.36; N, 1.94%. IR
silver(I) once bonded to PPh3 and the thio-ligand, as in the former
procedure, yielded the stable complexes which were crystallized
from CH2Cl2eCH3CN mixture (1:1 v/v). Thus silver(I) chloride with
C3H5NS(NeR) and PPh3 has yielded mononuclear complexes for
R ¼ H [17], Me (4), Et (5) and Prn (6) as well as dinuclear complexes
for R ¼ H (1), Me (2) and Et (3). Surprisingly for R ¼ Prn, silver(I)
chloride has formed only mononuclear complex 6 in the presence
of one or two equivalents of PPh3 with respect to the thione ligand.
Interestingly, silver(I) bromide with C3H5NS(NeR) and PPh3 only
formed dinuclear complexes for R ¼ Me (7), Et (8) and Prn (9) in the
presence of one or two equivalents of PPh3.
absorptions (
1542e1478(s),
Ph).
n
/cmꢀ1): 3046(m),
(CeN) þ (CeH); 1125(s),
n
(NeH); 3005e2928(w),
n
(CeH);
n
d
n
(C]S); 1094(m), n
(Pe
C
2.2.13. [Ag2(m-S,S-C4H3N2S2)(m-Br)(PPh3)4] 13
It was prepared by the same method as used for complex 12
(Yield 70%, mp. 155e157 ꢁC). Found: C, 61.37; H, 4.20; N, 1.94. Calc.
for C76H63Ag2BrN2P4S2: C, 61.29; H, 4.23; N,1.88%. IR absorptions (
cmꢀ1): 3046(m),
(NeH); 3010e2926(w), (CeH); 1545e1479(s),
(CeN) þ (CeH); 1123(s), (C]S); 1095(m), (PeCPh).
Ligands. See Supplementary.
n
/
Other thio-ligands, namely, C3H3NS(NeMe) when reacted with
silver(I) chloride in the presence of two equivalents of PPh3 with
respect to the thione ligand gave a mononuclear complex,
n
n
n
d
n
n
[AgCl(C3H3NS(NeMe))(PPh3)2] [17]. Similar reaction of silver(I)
bromide with C3H3NS(NeMe) and one or two equivalents of PPh3
has formed only dinuclear complex 10, and this activity is in line
with the behavior noted above with C3H5NS(NeR) thio-ligands.
Thiazolidine-2-thione (C3H5NS2) with silver(I) chloride is known
to form a tetrahedral complex, [AgCl(C3H5NS2)(PPh3)2] [17], and
unlike behavior noted for silver(I) bromide above, this thio-lgand
has formed a mononuclear complex 11 in the presence of one or
two equivalents of PPh3 with respect to the thione ligand. Scheme 1
shows preparation of complexes and their possible structures
(confirmed using X-ray crystallography vide infra).
Due to the lack of solubility of the dithiouracil as well as of
silver(I) halides in acetonitrile, the procedure adopted for the
preparation of complexes 1e11 was not applicable here. Thus
complexes 12 and 13 were prepared by the reaction of 2,4-
dithiouracil in methanol with a silver(I) halide suspended in
acetonitrile followed by stirring of the contents for about 48 h. The
resulting light yellow precipitate were reacted with PPh3 which
gave crystalline products (molar ratio was 1:1:1). Here the thio-
ligand removed one halogen per two silver(I) halide moieties and
bridged two silver(I) ions via S,S-donor atoms and the remaining
halogen formed the second bridge. Scheme 2 shows the formation
of complexes 12 and 13.
2.3. X-ray crystallography
The single crystals of compounds 1e4, 6e13 were mounted on
glass fibers and the data were collected using Xcalibur R (1, 4, 8e
10), Xcalibur Eos (2, 3, 6, 7) and Bruker APEX-II CCD (11), Bruker X8
Kappa APEXII (12, 13) diffractometers, each equipped with a
ꢀ
graphite monochromator and Mo-K
a
radiation (
l
¼ 0.71073 A). The
unit cell dimensions and intensity data were measured at 123(2)
(4), 295(2) (1, 8e10), 173(2) (2, 7), 170(2) (3, 6), 296(2) (11), 100(2)
(12, 13) K. The data were processed (data collection, refinement and
reduction) with CrysAlis Pro (1e4, 6e10), and corrected for ab-
sorption using spherical harmonics. The data were processed with
APEX2 (data collection) [27] and SAINT (cell refinement, data
reduction) for complexes 11e13 and corrected for absorption using
SADABS [28]. The structures were solved by the direct methods
using the program SHELXS-97, and refined by the full matrix least
square based on F2 with anisotropic thermal parameters for the
non-hydrogen atoms using SHELXL-97 and SHELXTL (molecular
graphics) [29]. The crystallographic data are given in Table 2.
3. Results and discussion
3.1. Comments on synthetic aspects
3.2. Infrared and NMR spectroscopy
In the preparation of silver(I) halide mixed-ligand complexes 1e
11, a silver(I) halide was first reacted with the PPh3 ligand in
acetonitrile followed by removal of the solvent and the resulting
solid was reacted with the thio-ligand in chloroform. However,
when a thio-ligand, C3H5NS(NeH) was reacted with silver(I) chlo-
ride in acetonitrile, a white solid was obtained and to this solid the
addition of PPh3 in the same solvent did not yield the mixed ligand
complex, rather a known cubane [AgCl(PPh3)]4 was obtained (the
addition of chloroform did not help in the latter procedure). The
The IR spectra of complexes 1e13 reveal the presence of both
the thio-ligands and triphenyl phosphine (see Experimental
section). In complexes 1e13, the
n(NeH) peaks appear in the
range 3046e3237 cmꢀ1 and reveal that the ligands are neutral in
complexes 1e11 and as uninegative anions in 12 and 13 (X-ray
crystallography vide infra). The most significant bands due to n(Ce
S) lie in the range 1180e1193 cmꢀ1 in complexes 1e9; in the region
920e996 cmꢀ1 in 10 and 11 and in the region 1123e1125 cmꢀ1 in
complexes 12 and 13. The presence of triphenyl phosphine is

T.S. Lobana et al. / Journal of Organometallic Chemistry 745-746 (2013) 460e469
465
Table 3
Bond lengths (A) and angles ( ) for compounds 1e4, 6e13.
supported by its characteristic
n
(PeCPh) bands in the range, 1093e
ꢁ
ꢀ
1114 cmꢀ1
.
The proton NMR spectra of complexes (experimental) reveal the
presence of characteristic groups, namely, eNH, eNR, CH2, CH, and
PPh3 and these groups generally appear at positions low field/
different positions relative to those of the ligands (see
Supplementary). For instance, the eNH groups show a broad signal
in the ligands and move to low field in their complexes (range,
7.79e9.72 ppm). Similarly, the C4,5H protons of free C3H5NS(NeH)
Halogen-bridged
dimmers
1
2
3
AgeS
AgeP
AgeCl
AgeCl*
2.5105(8)
2.4520(7)
2.6907(7)
2.7028(7)
1.696(3)
2.5211(6)
2.4394(5)
2.6591(6)
2.7207(6)
1.692(2)
2.515(1)
2.427(1)
2.635(1)
2.662(1)
1.701(2)
3.442(1)
116.71(2)
109.71(2)
112.15(2)
108.31(2)
109.50(2)
98.94(2)
CeS
Ag/Ag
PeAgeS
PeAgeCl
PeAgeCl*
SeAgeCl
SeAgeCl*
CleAgeCl*
AgeCleAg*
AgeSeC
697(2)
3.402(2)
ligand appear as a singlet at
field at
d 3.59 ppm which shifted to the low
130.07(3)
105.86(2)
109.45(2)
104.82(3)
106.98(2)
93.401(2)
86.599(2)
109.06(10)
116.77(2)
107.01(2)
111.14(2)
109.28(2)
109.93(2)
101.56(2)
78.44 (1)
108.66(8)
d
3.79 ppm in its complex 1. In other complexes, the C4H and
C5H protons appeared as a set of the multiplets. The proton signals
of PPh3 in complexes appeared as multiplets in the region, 7.26e
7.70 ppm.
Table 1 shows the 31P NMR data of complexes. Mononuclear
complexes, 4e6 and 11, exist as single species in the solution state
in line with the solid state behavior (vide infra) and coordination
shifts fall in the range, 7.10e15.69 ppm. Further, the coordination
shifts of dinuclear complexes 1, 9 and 10 lie in the range, 12.60e
19.10 ppm and these dimers exist in the solution as single species.
Dimers, 2, 3, 7, 12 and 13 showed the presence of more than one
species in solution whose nature is not well understood.
81.06(2)
108.72(9)
7
8
9
10
AgeS
AgeP
AgeBr
AgeBr*
CeS
Ag/Ag
2.5271(7)
2.4509(6)
2.7970(5)
2.7448(5)
1.694(2)
2.5257(13)
2.5270(7)
2.4484(6)
2.7323(3)
2.7704(4)
1.691(2)
3.3495(4)
115.09(2)
110.306(17)
111.199(17)
110.665(18)
103.95(2)
105.012(10)
74.989(10)
109.05(17)e
110.19(9)
2.5343(9)
2.4562(8)
2.7502(5)
2.8017(5)
1.690(4)
2.4433(10)
2.7247(6),
2.7591(6)
1.702(4)
3.421(1)
3.474(1)
3.350(1)
PeAgeS
PeAgeBr
PeAgeBr*
SeAgeBr
SeAgeBr*
BreAgeBr*
AgeBreAg*
AgeSeC
115.68(2)
106.718(18)
110.205(19)
108.27(2)
111.384(19)
103.767(13)
76.233(13)
109.13(8)
115.86(4)
111.06(3)
110.91(3)
109.70(3)
106.84(4)
101.398(18)
78.603(18)
109.05(17)
115.39(3)
110.35(3)
107.14(2)
111.37(3)
108.32(3)
103.480(15)
76.520(15)
109.13(13)
3.3. Crystal and molecular structures
The crystal data of complexes 1e4, 6e13 are given in Table 2,
and the bond parameters are given in Table 3. Complexes 1, 4 and 11
crystallized in the monoclinic crystal system with the space groups
P21/n (1) and P21/c (4,11), while other complexes (2, 3, 6e10,12, 13)
crystallized in the triclinic crystal with the space group P-1.
Hetero-bridged
dimmers
12
13
3.3.1. Mononuclear [Ag(k
1-S-HL)(PPh3)2X] complexes (4, 6, 11)
Ag1eS1
Ag1eCl1
Ag1eP1
Ag1eP2
Ag / Ag
Ag2eS2
Ag2eCl1
Ag2eP3
2.547(1)
2.632(2)
2.451(1)
2.470(1)
5.028(1)
2.599(4)
2.596(2)
2.385(2)
2.456(3)
Ag1eS1
Ag1eBr1
Ag1eP1
Ag1eP2
Ag / Ag
Ag2eS2
Ag2eBr1
Ag2eP3
2.556(2)
2.742(1)
2.442(2)
2.472(2)
5.148(1)
2.526(2)
2.736(1)
2.435(2)
Figs. 1e3 depict molecular geometries of mononuclear com-
plexes 4, 6 and 11 along with their numbering schemes respec-
tively. In each of these complexes, the silver atom is bonded to two
P atoms of Ph3P ligands, one S atom of a thio-ligand and one
halogen atom (4, 6, Cl; 11, Br). The AgeS bond distances, 2.637(1)
ꢀ
(4), 2.721(1) (6) and 2.683(1)
A
(11) are longer than that
1-S-C3H5NS(Ne
H))(PPh3)2Cl] 14 [17], but are smaller than the expected AgeS single
ꢀ
{2.603(1) A} observed in analogous complex, [Ag(
k
Ag2eP4
CeS
Ag2eP4
2.514(2)
1.729(5), 1.744(9)
CeS
1.704(8); 1.789(10)
114.57(6)
107.99(6)
103.39(5)
97.35(4)
P1eAg1eS1
P2eAg1eS1
P1eAg1eCl1
P2eAg1eCl1
S1eAg1eCl1
P1eAg1eP2
Ag2eCl1eAg1
P3eAg2eS2
P4eAg2eS2
P3eAg2eCl1
P4eAg2eCl1
S2eAg2eCl1
P3eAg2eP4
AgeSeC
114.60(4)
107.79(4)
103.40(6)
99.57(5)
102.49(5)
125.15(4)
148.21(8)
113.93(8)
114.60(9)
104.77(6)
95.88(7)
P1eAg1eS1
P2eAg1eS1
P1eAg1eBr1
P2eAg1eBr1
S1eAg1eBr1
P1eAg1eP2
Ag2eBr1eAg1
P3eAg2eS2
P4eAg2eS2
P3eAg2eBr1
P4eAg2eBr1
S2eAg2eBr1
P3eAg2eP4
AgeSeC
104.81(5)
125.09(6)
140.06(4)
116.34(7)
118.12(7)
103.64(5)
89.71(6)
102.61(6)
120.66(7)
108.9(2); S1
114.2(4) S2
104.58(5)
117.81(7)
110.6(3; S1
118.2(3) S2
Monomers
4 (Cl)
6 (Cl)
11 (Br)
AgeS1
AgeX
AgeP1
AgeP2
2.637(1)
2.570(1)
2.467(1)
2.477(1)
1.700(1)
105.90(1)
114.15(1)
110.71(1)
98.09(1)
105.43(1)
121.37(1)
108.36(5)
2.721(1)
2.5751(5)
2.455(1)
2.475(1)
1.702(2)
105.78(2)
105.70(2)
109.55(2)
111.05(2)
97.89(2)
123.51(2)
100.48(7)
2.683(1)
2.659(1)
2.469(1)
2.478(1)
1.680(3)
106.24(3)
108.66(3)
112.50(2)
101.78(2)
104.46(2)
121.94(3)
109.63(9)
CeS
P1eAgeS1
P2eAgeS1
P1eAgeX
P2eAgeX
S1eAgeX
P2eAgeP1
AgeSeC
Fig. 1. Molecular structure of [AgCl(k
1-S-C3H5NS(NeMe))(PPh3)2] 4.
The significance of asterisk shows center of symmetry.

466
T.S. Lobana et al. / Journal of Organometallic Chemistry 745-746 (2013) 460e469
11 > 4 > 6. The geometry around each metal center is distorted
tetrahedral.
3.3.2. Halogen-bridged dinuclear [Ag2(m-X)2(k
1-S-L)2(PPh3)2]
complexes (1e3, 7e10)
Figs. 4e6 depict molecular structures of the chloro-bridged
dinuclear complexes 1e3, while Figs. 7e10 depict those of the
bromo-bridged dinuclear complexes, 7e10. In these complexes,
each Ag atom is bonded to one S atom of a thio-ligand, one P atom
of Ph3P and two bridging halogens (Cl, 1e3; Br, 7e10). In the
dinuclear complexes 1e3, it can be seen from Table 3 that the
variation of the substituents at one nitrogen atom of the thio-
ligands, C3H5NS(NeR) marginally affected the AgeS and AgeP
bond distances, however, the AgeCl distances of Ag(m-Cl)2Ag cores
were affected to somewhat greater extent. The shorter AgeCl bond
distances are noted for R ¼ ethyl at N atom in complex 3. The AgeS
bond distances are shorter while AgeP distances are similar to
those in the mononuclear complexes, 4 and 6. Owing to the
halogen-bridging in 1e3, the AgeCl distances are expectedly much
longer than in the mononuclear complexes 4 and 6 with terminal
halogens. The angles around each Ag metal center suggest distorted
tetrahedral geometry. The AgeCl bond distances and the AgeCleAg
Fig. 2. Molecular structure of [AgCl(k
1-S-C3H5NS(NePrn))(PPh3)2] 6.
and CleAgeCl angles of the Ag(
m-Cl)2Ag core reveal that the central
cores of the dimers 1e3 deviate from a square. The AgeSeC angles
lie in the range, 108.66(8)e109.06(10) and are typical of the
bonded heterocyclic thione ligands [1e6].
k
1-S
ꢀ
bond distance of 2.78 A [30]. It may be noted that the AgeS bond
distances increase with the variation of R at N in the order: 6
(Prn) > 4 (Me) > 14 (H). The AgeS bond distance observed in
silver(I) bromide complex 11 is shorter than that found in 6. The
AgeP bond distances (Table 3) of 4, 6 and 11 are comparable but
The bonding pattern of the bromo-bridged dinuclear complexes
7e10 (Figs. 7e10) is similar to that of the chloro-bridged complexes
1e3. The AgeS and AgeP distances in 7e9 are similar to those
found in 1e3, except in complex 10 which has relatively longer Age
S/AgeP distances. The variation of the substituents (R) at one ni-
trogen atom of a thio-ligand, C3H5NS(NeR) marginally affected the
AgeS and AgeP bond distances. However, the AgeBr distances of
ꢀ
somewhat longer than in 14 {2.452(1), 2.445(1) A} [17]. The AgeCl
ꢀ
bond distances, 2.570(1) 4 aꢀnd 2.575(1) A 6, are less than the sum of
the ionic radii of Agþ and Cl , 2.75 A [30]. The AgeBr bond distance
ꢀ
ꢀ
Ag(m-Br)2Ag cores were affected to a greater extent. Owing to the
of 2.659(1)ꢀA in complex 11is less than the sum of the ionic radii of
Agþ and Br , 2.90 A [30], and longer than that {2.631(1) A} observed
in similarly bonded bromide in the sulfur-bridged dimeric complex,
ꢀ
ꢀ
bromo-bridging in 7e10, the AgeBr distances are much longer than
in the mononuclear bromide complex 11. The angles around each
Ag metal center suggest a distorted tetrahedral geometry. The Age
SeC angles lie in the range, 109.05(17)e110.19(9) which are close to
those found in complexes 1e3.
[Ag2Br2(
m
-S-C5H5NS)2(PPh3)2] (C5H5NS ¼ pyridine-2-thione) [19].
The bond angles around each silver atom vary in the range, 98.00e
123.50ꢁ with PeAgeP being the largest angle in view of the steric
effect of Ph3P ligands. Further, the AgeSeC angle at sulfur is
shortest in 6 and largest in 11, that is it varies in the order:
3.3.3. Hetero-bridged dinuclear [Ag2(m-X)(m-k k
1S, 1S-C4H3N2S2)
(PPh3)4 complexes (12, 13)
In complex [Ag2(
bonded to two P atoms of two PPh3 ligands and one
During the reaction, the dithiouracil deprotonates one eNH
m-Cl)(m-S,S-C4H4N2S2)(PPh3)4], 12, each Ag is
m-Cl atom.
Fig. 3. Molecular structure of [Ag(
k
1-Br)(
k
1-S-C3H5NS2)(PPh3)2] 11.
Fig. 4. Molecular structure of [Ag2(m-Cl)2(k
1-S-C3H5NS(NeH))2(PPh3)2] 1.

T.S. Lobana et al. / Journal of Organometallic Chemistry 745-746 (2013) 460e469
467
Fig. 7. Molecular structure of [Ag2(m-Br)2(k
1-S-C3H5NS(NeMe))2(PPh3)2] 7.
largest as usual. In the eight membered ring, the Ag1eCleAg2 angle
of 148.21(8)ꢁ is largest as compared to the other angles observed.
The bonding pattern for complex 13 is same as that of complex 12.
The C(11)eS(1) and C(15)eS(2) bond distances of 1.704(8) and
Fig. 5. Molecular structure of [Ag2(m-Cl)2(k
1-S-C3H5NS(NeMe))2(PPh3)2] 2.
ꢀ
1.789(10) A in 13 suggest that there is a significant variation in the
CeS bond distances in the two cases.
hydrogen and as anion it binds to two different Ag atoms through
its two S donor atoms, thus completing a central eight membered
3.4. The CeS bond distances, nature of bridging in dimers and
Ag/Ag contacts
ꢀ
metallacyclic ring (Fig. 11). The Ag1eS1 bond distance of 2.547(1) A
ꢀ
is somewhat shorter than Ag2eS2 bond distance of 2.599(4) A,
ꢀ
while the Ag1eCl1 bond distance (2.632(2) A) is longer than Ag2e
ꢀ
The CeS bond distances of 1.700(10), 1.702(2) and 1.680(3)) A
respectively observed in mononuclear complexes, 4, 6 and 11 are
significantly longer than the C]S double bond distance of 1.62 A
[31], but shorter than a CeS single bond distance of 1.81 A [31]
suggesting partial double bond character in the CeS bond. Simi-
larly in the halogen-bridged dimers 1e3 and 7e10, the CeS bond
ꢀ
Cl1 bond distance (2.596(2) A). Further, the AgeP bond distances
are longer with Ag1 and shorter with Ag2. The C(11)eS(1) and
ꢀ
ꢀ
C(15)eS(2) bond distances of 1.729(5) and 1.744(9) A suggest that
ꢀ
Ag1 is bonded to the thione sulfur and Ag2 is bonded to the thiolate
sulfur of the dithiouracilate anion. Further, the angles around Ag1
and Ag2 vary in the range 95e125ꢁ with PeAgeP angles being the
Fig. 6. Molecular structure of [Ag2(
m
-Cl)2(
k
1-S-C3H5NS(NeEt))2(PPh3)2] 3.
Fig. 8. Molecular structure of [Ag2(m-Br)2(k
1-S-C3H5NS(NeEt))2(PPh3)2] 8.

468
T.S. Lobana et al. / Journal of Organometallic Chemistry 745-746 (2013) 460e469
Fig. 11. Molecular structure of [Ag2(
Supplementary Fig S1 for13).
m-Cl)(m-S,S-C4H4N2S2)(PPh3)4] (12)(see
Fig. 9. Molecular structure of [Ag2(
m
-Br)2(
k
1-S-C3H5NS(NePrn))2(PPh3)2] 9.
ratio of 2:1 favored halogen-bridging (15). In the dimers 1e3, 7e10
distances lie in the range 1.690(4)e1.702(4)ꢁ (Table 4) and these are
similar to the terminally bonded thio-ligands in 4, 6 and 11. Inter-
with C:N ratio of 3:2 or 3:1, all favored halogen-bridging. As regards
2,4-dithiouracil, each sulfur binds to one Ag metal center in k
1-S
mode only (12, 13) and does not bridge two Ag metals unlike that in
pyridine-2-thione complexes 16 and 17. A plausible explanation for
the behavior as highlighted above is attributed to the reduction in
Lewis basicity of exo-cyclic sulfur when a ring contains two elec-
tronegative nitrogen atoms, i.e. low C:N ratio. This makes sulfur
more electronegative by contracting charge around sulfur nucleus.
It paves way for bridging by the halogens in various complexes
discussed above. Alternatively, it can be argued that the halogen
bridges existing in silver(I) halides (polymeric) are not cleaved
by thio-ligands when C:N ratio is low. The trend pertains to the
mixed ligand complexes with a thione and a PPh3 ligand as given in
Table 4 and the C:N ratio considered is of the ring carbons ands
nitrogens only.
estingly, in bromo-bridged dimer of pyrimidine-2-thione, [Ag2(m-
Br)2(
k
1-S-L)2(PPh3)2] 15 (L ¼ pyrimidine-2-thione) [18], the CeS
distance was 1.689(4), similar to those values in the above
mentioned dimers. The CeS distances observed in sulfur-bridged
dinuclear [Ag2X2(
16, Br, 17) [19] are longer as anticipated.
m
-S-L)2(PPh3)2] complexes (L ¼ C5H5NS; X ¼ Cl,
From Table 4, some interesting observations about the type of a
bridge between two Ag metal centers in the mixed ligand com-
plexes under study made are given as follows. It is found that the
thio-ligand, namely, pyridine-2-thione (16, 17) with a C:N ratio of
5:1 favored sulfur-bridging, while pyrimidine-2-thione with C:N
The rupture of the silver-halogen bonds as found in the dinu-
clear 12 and 13 complexes is attributed to the geometric positions
of the sulfur atoms which in their bid to bind to two Ag metals
centers knock out one halogen while second halogen is retained
which acts as a bridge. This leads to an unusual eight membered
ring formed by two Ag, one halogen, two sulfur, two carbons and
one nitrogen atoms. It is observed that dimers 2, 3, 7e10 have
ꢀ
Ag/Ag distances in the range, 3.350(1)e3.474(1) A, which are close
ꢀ
to twice the sum of van der Waals radius of Ag atom, 3.40 A [30,31];
dimer 1 has Ag/Ag distance of 3.697(2). All these distances are
much shorter than those found in dimers 12, 13, 16 and 17
ꢀ
{3.821(10e5.148(1)) A, Table 4}. The shortest Ag/Ag distances
Table 4
A comparative account of some important distances.
ꢀ
ꢀ
CeS, A
Ag/Ag, A
Type of bridge
[Ref]
1
2
3
7
8
9
10
12
13
15
16
17
1.693(3)
1.692(2)
1.701(2)
1.694(2)
1.702(4)
1.691(2)
1.690(4)
1.729(5); 1.744(9)
1.704(8); 1.789(10)
1.689(4)
1.722(2)
1.717(2)
3.697(2)
3.402(2)
3.442(1)
3.421(1)
3.474(1)
3.350(1)
3.438(1)
5.028(1)
5.148(1)
e
Ag(
Ag(
Ag(
Ag(
Ag(
Ag(
Ag(
Ag(
Ag(
Ag(
Ag(
Ag(
m
m
m
m
m
m
m
m
m
m
m
m
-Cl)2Ag
-Cl)2Ag
-Cl)2Ag
-Br)2Ag
-Br)2Ag
-Br)2Ag
-Br)2Ag
This work
This work
This work
This work
This work
This work
This work
This work
This work
[18]
-Cl)(k
1S,
1S,
k
1S)2 Ag
k
1S)2 Ag
-Br)(
k
-Br)2Ag
-S)2Ag
-S)2Ag
3.844(1)
3.821(1)
[19]
[19]
Fig. 10. Molecular structure of [Ag2(m-Br)2(k
1-S-C3H3NS(NeMe))2(PPh3)2] 10.

T.S. Lobana et al. / Journal of Organometallic Chemistry 745-746 (2013) 460e469
4326e4334;
469
3.350(1)e3.474(1) are found when the five membered rings have
(c) P.J. Cox, A. Kaltzoglou, P. Aslanidis, Inorg. Chim. Acta 359 (2006) 3183e3190;
(d) A. Kaltzoglou, P.J. Cox, P. Aslanidis, Inorg. Chim. Acta 358 (2005) 3048e3056;
(e) P. Aslanidis, P.J. Cox, S. Divanidis, P. Karagiannidis, Inorg. Chim. Acta 357
(2004) 1063e1076.
alkyl substituent at one N-atom of the ring.
4. Conclusion
[8] (a) T.S. Lobana, R. Sharma, R. Sharma, S. Mehra, A. Castineiras, P. Turner, Inorg.
Chem. 44 (2005) 1914e1921;
In the synthesis of complexes 1e11, it was found that Ag(I) be
first bonded to PPh3 in acetonitrile and after removal of the solvent,
it be bonded to the thione sulfur in chloroform. The C:N ratio of a
heterocyclic ring (excluding the substituent at N) appeared to affect
the nature of bridging between two metals. The thio-ligand sub-
stituents affected silveresilver distances. Finally, the rupture of the
silverehalogen bonds by a thio-ligand (dithiouracil in the present
case) and the formation of an eight membered metallacyclic ring
are rare features encountered in metaleheterocycilic thione
chemistry. This study makes a significant contribution to silver(I)
halideeheterocyclic thione chemistry by reporting twelve new
silver(I) complexes which are structurally characterized.
(b) T.S. Lobana, R. Sharma, G. Hundal, R.J. Butcher, Inorg. Chem. 45 (2006)
9402e9409;
(c) T.S. Lobana, R. Sharma, R. Sharma, R.J. Butcher, Z. Anorg. Allg. Chem. 634
(2008) 1785e1790;
(d) T.S. Lobana, R. Sultana, G. Hundal, A. Castineiras, Polyhedron 28 (2009)
1573e1577;
(e) T.S. Lobana, R. Sultana, A. Castineiras, R.J. Butcher, Inorg. Chim. Acta 362
(2009) 5265e5270;
(f) T.S. Lobana, R. Sultana, G. Hundal, R.J. Butcher, Dalton Trans. 39 (2010)
7870e7872;
(g) T.S. Lobana, R. Sultana, R.J. Butcher, Dalton Trans. 40 (2011) 11382e11384.
[9] B. Krebs, G. Hengel, Angew. Chem. Int. Ed. Engl. 30 (1991) 769e788.
[10] P.G. Blower, J.R. Dilworth, Coord. Chem. Rev. 76 (1987) 121e185.
[11] M. Wruble, J. Am. Pharm. Assoc. Sci. Ed. 32 (1943) 80e82.
[12] M.N. Xanthopoulou, S.K. Hadjikakou, N. Hadjiliadis, M. Kubicki, S. Skoulika,
T. Bakas, M. Baril, I.S. Butler, Inorg. Chem. 46 (2007) 1187e1195.
[13] P.C. Zachariadis, S.K. Hadjikakou, N. Hadjiliadis, S. Skoulika, A. Michaelides,
J. Balzarini, E.D. Clercq, Eur. J. Inorg. Chem. (2004) 1420e1426.
[14] K. Nomiya, Y. Kondoh, H. Nagano, M. Oda, J. Chem. Soc. Chem. Commun.
(1995) 1679e1680.
[15] K. Nomiya, S. Takahashi, R. Noguchi, J. Chem. Soc. Dalton Trans. (2000)
2091e2097.
[16] P. Karagiannidis, P. Aslanidis, S.C. Kokkou, C.J. Cheer, Inorg. Chim. Acta 172
(1990) 247e251.
[17] R. Sultana, T.S. Lobana, R. Sharma, A. Castineiras, T. Akitsu, K. Yahagi,
Y. Aritake, Inorg. Chim. Acta 363 (2010) 3432e3441.
[18] P.J. Cox, P. Aslanidis, P. Karagiannidis, S.K. Hadjikakou, Inorg. Chim. Acta 310
(2000) 268e272.
[19] T.S. Lobana, R. Sharma, R.J. Butcher, Polyhedron 27 (2008) 1375e1380.
[20] (a) G.A. Bowmaker, N. Chaichit, C. Pakawatchai, B.W. Skelton, A.H. White,
Dalton Trans. (2008) 2926e2928;
Acknowledgments
Financial assistance from UGC(SAP) and CSIR New Delhi is
gratefully acknowledged. JPJ acknowledges the NSF-MRI program
(grant No. CHE1039027) for funds to purchase the X-ray diffrac-
tometer. MCV acknowledges the support by the EC project Complex
INC (Framework Programme 7 (FP7) under grant agreement no.
279039) and Comunidad de Madrid project Complemento-CM
(S2010/BMD-2316).
Appendix A. Supplementary material
(b) G.A. Bowmaker, N. Chaichit, C. Pakawatchai, B.W. Skelton, A.H. White, Can.
J. Chem. 87 (2009) 161e170.
[21] L.P. Bataglia, A.C. Bonamartini, M. Nardelli, Croat. Chem. Acta 57 (1984)
545e563.
[22] (a) A. Beheshti, W. Clegg, N.R. Brooks, F. Sharafi, Polyhedron 24 (2005)
435e441;
CCDC 911388e911399 for compounds 1e4, 6e13 respectively
contain the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
(b) M. Hong, W. Su, R. Cao, W. Zhang, J. Lu, Inorg. Chem. 38 (1999)
600e602.
[23] (a) K. Yamanari, Y. Kushi, A. Fuyuhiro, S. Kaizaki, J. Chem. Soc. Dalton Trans.
(1993) 403e408;
Appendix B. Supplementary data
(b) D.R. Corbin, L.C. Francesconi, D.N. Hendrickson, G. Stucky, J. Chem. Soc.
Chem. Commun. (1979) 248;
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.jorganchem.2013.08.020.
(c) C. Landgrafe, W.S. Sheldrick, J. Chem. Soc. Dalton Trans. (1996) 989e998.
[24] P. Aslanidis, P.J. Cox, A. Kaltzoglou, A.C. Tsipis, Eur. J. Inorg. Chem. (2006)
334e344.
[25] T.S. Lobana, S. Khanna, R. Sharma, G. Hundal, R. Sultana, M. Chaudhary,
R.J. Butcher, A. Castineiras, Cryst. Growth Des. 8 (2008) 1203.
[26] J.A. Garcia-Vazquez, A. Sousa-Pedrares, M. Carabel, J. Romero, A. Sousa,
Polyhedron 24 (2005) 2043e2054.
[27] Bruker, APEX2 Software. V2.0e1, Bruker AXS Inc., Madison, Wisconsin, USA,
2005.
[28] G.M. Sheldrick, SADABS. Program for Empirical Absorption Correction of Area
Detector Data, University of Goettingen, Germany, 1997.
[29] G.M. Sheldrick, Acta Crystallogr. A 64 (2008) 112e122.
[30] J.E. Huheey, E.A. Keiter, R.L. Keiter, Inorganic Chemistry: Principles of Struc-
ture and Reactivity, fourth ed., Harper Collins, New York, 1993.
[31] L. Pauling, The Nature of the Chemical Bond, third ed., Cornell University
Press, New York, 1960.
References
[1] E.S. Raper, Coord. Chem. Rev. 61 (1985) 115e184.
[2] E.S. Raper, Coord. Chem. Rev. 153 (1996) 199e255.
[3] E.S. Raper, Coord. Chem. Rev. 129 (1994) 91e156.
[4] E.S. Raper, Coord. Chem. Rev. 165 (1997) 475e567.
[5] P.D. Akrivos, Coord. Chem. Rev. 213 (2001) 181e210.
[6] J.A. Garcia-Vazquez, J. Romero, A. Sousa, Coord. Chem. Rev. 193 (1999)
691e745.
[7] (a) D. Kovala-Demertzi, P. Tauridou, U. Russo, M. Gielen, Inorg. Chim. Acta 239
(1995) 177e183;
(b) C. Vetter, C. Wagner, J. Schmid, D. Steinborn, Inorg. Chim. Acta 359 (2006)