Sulfur bridging by acetophenone thiosemicarbazone in [Ag(μ-dppm)2(μ-SR)Ag(ONO2)](NO3) dimer with a new {Ag2(μ-P,P)2(μ-SR)} core

Article abstract of DOI:10.1016/j.inoche.2007.08.005

Acetophenone thiosemicarbazone (Haptsc) with silver(I) nitrate and Ph₂P-CH₂-PPh₂ (dppm) has formed a first example of triply hetero-bridged [Ag(μ-P,P-dppm)₂(μ-S-Haptsc)Ag(ONO₂)]NO₃ dimer with a short Ag?Ag contact of 2.9939(7) A?.

Full text of DOI:10.1016/j.inoche.2007.08.005

Available online at www.sciencedirect.com
Inorganic Chemistry Communications 10 (2007) 1307–1310
www.elsevier.com/locate/inoche
Sulfur bridging by acetophenone thiosemicarbazone
in [Ag(l-dppm)2(l-SR)Ag(ONO2)](NO3) dimer with a new
{Ag2(l-P,P)2(l-SR)} core
a,
a
b
Tarlok S. Lobana *, Sonia Khanna , Alfonso Castineiras
a
Department of Chemistry, Guru Nanak Dev University, Amritsar 143 005, India
Departamento De Quimica Inorganica, Facultad de Farmacia, Universidad de Santiago, 15782 Santiago, Spain
b
Received 11 July 2007; accepted 7 August 2007
Available online 15 August 2007
Abstract
Acetophenone thiosemicarbazone (Haptsc) with silver(I) nitrate and Ph2P–CH2–PPh2 (dppm) has formed a first example of triply
˚
hetero-bridged [Ag(l-P,P-dppm)2(l-S-Haptsc)Ag(ONO2)]NO3 dimer with a short Ag Æ Æ Æ Ag contact of 2.9939(7) A.
Ó 2007 Elsevier B.V. All rights reserved.
Keywords: Acetophenone thiosemicarbazone; Silver(I); Bis(diphenylphosphino)methane; Triply bridging; Asymmetrically coordinated
In literature, diphosphine complexes of silver(I) usually
adopt modes A–C having two or more than two P, P-
bridges (Chart 1) [1–7]. For example, mode A is shown
by bis(diphenylphosphino)methane in [(NO3)Ag(l-P,P-
dppm)2Ag(NO3)] [1]. Similarly, mode B is shown by
bis(diphenylphosphino)pentane in [Ag(l-P,P-dppp)2(l-
Cl)2Ag] [2]. Bis(diphenylphosphino)ferrocene shows coor-
dination mode C in [(HCOO)Ag(l-P,P-dppf)3Ag(HCOO)]
complex [3].
There are a few reports on silver(I)-thiosemicarbazone
chemistry, namely, the formation of a hexameric complex
[Ag6(HL)6] (HL = anion of salicylaldehyde thiosemicarba-
zone) with N2–S-bridging cum-S-bridging coordination
mode, and a few other complexes characterized by analyt-
ical data and spectroscopically [8]. As a part of our interest
in metal-thiosemicarbazone chemistry [9], it was desired to
explore Ag2(l-P,P)m cores (m = 1–3), bonded to thio-
semicarbazones.
tsc)-Ag(ONO2)]NO3 1. It has sulfur bridging across the
Ag2(l-P,P-dppm)2 core, and it represents a new coordina-
tion mode D in metal-thiosemicarbazone chemistry, which
is reported in this communication (Scheme 1).
Reaction of AgNO3 (0.025 g, 0.14 mmol) with one mole
of dppm (0.056 g, 0.14 mmol) in CH3CN (10 mL) at 40 °C,
followed by the addition of one mole of Haptsc ligand
(0.028 g, 0.14 mmol) in methanol (5 mL) under magnetic
stirring for 2 h, has formed compound, [Ag(l-P,P-dppm)2
(l-S-Haptsc)Ag(ONO2)]NO3 1. Its IR spectrum shows
the presence of m(N–H) bands at 3342 cmꢀ1 (due to
–N1H2 group), and 3165 cmꢀ1 (due to –N2H group), sup-
porting the interaction of thiosemicarbazone ligand with
silver(I) as a neutral ligand. A thioamide band, m(C@S) at
833 cmꢀ1 shifts to lower energy while m(C–N) bands at
999, 1024 cmꢀ1 show a shift to higher energy with respect
to the free Haptsc ligand {m(C@S), 844 cmꢀ1; m(C–N),
916, 962 cmꢀ1}. Medium to broad peaks are observed in
In a typical reaction, acetophenone thiosemicarbazone
was reacted with silver(I) nitrate and dppm, leading to
the formation of the dimer, [Ag(l-P,P-dppm)2(l-S-Hap-
the
region
1480–1605 cmꢀ1
corresponding
to
{dNH2 + m(C@N) + m(C@C)} vibrational modes, which
`
are at slightly higher energy regions vis-a-vis the free
ligand. Presence of characteristic m(P–CPh
) band at
1095 cmꢀ1 indicates the presence of coordinated dppm in
the complex, and it shifted to slightly higher energy region
*
Corresponding author. Fax: +91 183 2 258820.
E-mail address: tarlokslobana@yahoo.co.in (T.S. Lobana).
1387-7003/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2007.08.005

1308
T.S. Lobana et al. / Inorganic Chemistry Communications 10 (2007) 1307–1310
S
H
N
C
C2= N
R
N1H2
H3C
AgNO3
+
Ph2PCH2PPh2
+
P
P
S
NO3
O2NO
Ag
Ag
P
P
2.994(1) Å
1
Scheme 1.
P
P
P
P
Cl
Cl
O
O
Ag
Ag
Ag
Ag
O
N
N
O
O
O
P
P
P
P
(A)
P
(B)
R
+
Fig. 1. Structure of complex 1 with atomic numbering scheme. Selected
bond lengths (A) and angles (°): Ag(1)–Ag(2) 2.9939(7), Ag(1)–S(1)
P
P
P
˚
P
P
S
2.6282(18), Ag(1)–P(11) 2.4612(7), Ag(1)–P(41) 2.4500(17), Ag(2)–S(1)
2.5971(18), Ag(2) ꢀP(31) 2.4375(17), Ag(2)–P(21) 2.4575(17), S(1)–C(18)
1.704(7), Ag(2) –O(11) 2.462(5), P(41)–Ag(1)–P(11) 128.47(6), P(41)–
Ag(1)–S(1) 107.29(6), P(11)–Ag(1)–S(1) 114.55(6), P(31)–Ag(2)–P(21)
132.56(6), P(31)–Ag(2)–O(11) 109.14(14), P(21)–Ag(2)–O(11) 88.85(12),
P(31)–Ag(2)–S(1) 110.78(6), P(21)–Ag(2)–S(1) 109.76(6), O(11)–Ag(2)–
S(1) 97.38(14), C(18)–S(1)–Ag(2) 100.2(2), C(18)–S(1)–Ag(1) 105.8(3),
Ag(2)–S(1)–Ag(1) 69.91(5).
O2NO
Ag
Ag
Ag
P
Ag
OHCO
OCHO
P
P
P
(C)
(D)
Chart 1.
with respect to the free ligand (1091 cmꢀ1). The coordi-
nated and ionic nitrate bands in the complex appear at
1605, 1384 and 1304 cmꢀ1 and could not be assigned sepa-
rately due to various other bands in this region [10]. In
order to resolve the bonding by nitrate and to establish
the geometry around silver atoms, single crystal structure
determination has been carried out.
The crystal structure of complex 1 shows the presence of
two silver(I) atoms bridged by two dppm and one aceto-
phenone thiosemicarbazone ligands, resulting in a triply
bridged dinuclear complex [Ag(l-P,P-dppm)2(l-S-Hap-
tsc)Ag(ONO2)]NO3 1 (Fig. 1). Compound 1 has one unid-
entate NOꢀ3 coordinating to one Ag(I) center and the
second NOꢀ3 is outside the coordination sphere. Further,
compound 1 has two asymmetrically coordinated silver(I)
centers, one is three coordinated and second is four coordi-
nated. It is known that the complex of silver(I) nitrate with
dppm is dinuclear [(NO3)Ag(l-P,P-dppm)2Ag(NO3)] [1]
and has P, P bridges along with chelating nitrates. The for-
mation of 1 may be treated as sulfur bridging across Ag(l-
P,P-dppm)2Ag core of [(NO3)Ag(l-P,P-dppm)2Ag(NO3)]
with simultaneous movement of one nitrate outside the
coordination sphere.
In complex 1, the bond angles around one of the silver
atoms, 107.29(6)–128.47(6)° support a distorted trigonal
planar geometry with the P(41)–Ag(1)–S angle being the
smallest (107.29(6)°) and the P(41)–Ag(1)–P(11) being the
largest angle (128.47(6)°). The second silver atom exhibits
a distorted tetrahedral geometry as the bond angles range
from 88.85(12)° to 110.78(6)°. The P–Ag–P0 bond angles
in 1 are nonlinear resulting in the folding of the central
Ag2P4 core across Agꢁ ꢁ ꢁAg axis. The introduction of sulfur
bridging across Ag2P4 core bends P–Ag–P0 angles to
128.47(6)° and 132.56(6)°, shorter than 138.3(1)° in the
compound [(NO3)Ag(l-P,P-dppm)2Ag(NO3)] [1].
Two Ag and one S atoms form an isosceles triangle
{S–Ag–Ag, 54.56(4)°, 55.53(4)°, S–Ag–S, 69.91(5)°}, bring-
˚
ing the Agꢁ ꢁ ꢁAg contact to 2.9939(7) A, less than twice the
˚
sum of radius of silver(I), (3.4 A) [11]. This distance is
˚
shorter than 3.085(1) A in [(NO3)Ag(l-P,P)2Ag(NO3)] [1].
The S–Ag–S bond angle of 69.91(5)° is slightly shorter than
72–74° in sulfur bridged complex [Ag(CN)2(etu)2]n (et =
2-imidazolidinethione) [11].
Two molecules of dppm bridge the Ag atoms with Ag–P
˚
bond distances in the range, 2.437–2.461 A. The Ag–P
˚
bond distances are slightly longer than ca. 2.417–2.436 A

T.S. Lobana et al. / Inorganic Chemistry Communications 10 (2007) 1307–1310
1309
in [(NO3)Ag(l-P,P-dppm)2Ag(NO3)] [1]. Neutral acetophe-
none thiosemicarbazone ligand bridges across Ag(l-
P,P)2Ag core via its sulfur atom, with Ag–S bond distance
of Haptsc, and dppm ligands (d 7.00–7.69 ppm). Methyl pro-
tons of Haptsc ligand show a single signal at d 2.22 ppm.
Methylene protons of dppm ligands appear as a pair of dou-
blets at d 3.21, 3.60 ppm. Further, the 31P NMR spectrum of
1 shows two signals at d, ꢀ106.2 ppm, and d, ꢀ109.7 ppm
with coordination shifts (dcomplex ꢀ dligand) of 24.01 and
20.5 ppm, respectively, supporting the presence of two
non-equivalent phosphorous atoms in the complex.
˚
of 2.6282(18), 2.5971(18) A. These Ag–S bond distances are
˚
longer than 2.573(1)
A
in [Ag(pymtH)(PPh3)2]NO3
(pymtH = pyrimidine-2-thione) [12]. The nitrate is coordi-
nated to silver atom in 1 via one of its oxygen atoms with
˚
a bond distance of 2.462(5) A, comparable with Ag–O dis-
˚
tance of 2.416(5) A, but shorter than second Ag–O distance
In conclusion, complex 1 reveals a new coordination
core {Ag2(l-P,P)2(l-SR)} in metal-thiosemicarbazone
chemistry. In literature, modes close to 1 are shown by
heterocyclic thioamides with dppm as a coligand, as
in [Rh2(CO)2(l-S–L)(l-P,P-dppm)2]Cl Æ CH2CL2 (L = 1,3-
˚
of 2.689(6) A in [(NO3)Ag(l-P,P-dppm)2Ag(NO3)] [1]. It
may be noted that bridging of Ag(l-P,P-dppm)2Ag core
by sulfur atom of Haptsc has brought Ag–Ag contact close
˚
to 2.9939(7) A, less than twice the sum of radius of silver(I),
(3.4 A) [13].
thiazolidine-2-thione),
[Cu2(l-S–L)2(l-P,P-dppm)(g1-P-
(L = 6-tertbutyl-dimethylsilylpyridine-2-thione)
˚
The imino hydrogen (–N2H) is engaged in strong intra-
dppm)]
[14–16].
molecular hydrogen bonding with the coordinated oxygen
2
˚
atom (–N Hꢁ ꢁ ꢁONO2, 2.51 A) as well as with the non-coor-
Compound 1: Mp 190–192 °C, yield: 0.050 g, 52%. C, H,
N, analysis for C59H55Ag2N5O6P4S: C, 54.38; H, 4.22; N,
5.38. Found: C, 54.28; H, 4.16; N, 5.13. Main IR peaks
(KBr, cmꢀ1): m(N–H), 3342 m (–NH2) 3165m (–NH);
d(NH2) + m(C@N) + m(C–C), 1541s, 1483s; m(C@S) + m(C–
N), 1024s, 999s, 833s (thioamide moiety); 1095 m(P–CPh).
1H NMR data (d, ppm; CDCl3), 10.53 (s, N2H), 8.75 (sb,
–N1H2), 7.00–7.69 (m, Ph + –N1H2), 3.21, 3.60 (d, –CH2),
2.22 (s, CH3). 31P NMR data (d, ppm, CDCl3), ꢀ106.2,
ꢀ109.7 ppm, Dd(dcomplex ꢀ dligand) = 24.01, 20.5 ppm (31P
NMR spectra were recorded by taking TMP {(MeO)3P}
as external reference taken at zero position).
2
˚
dinated oxygen atom (–N Hꢁ ꢁ ꢁONO2, 2.14 A) of the
bonded nitrate group (Fig. 2). On the other hand, one
hydrogen atom of amino group (–N1H2) is engaged in
strong intramolecular hydrogen bonding with the azome-
1
3
˚
thine nitrogen (–HN Hꢁ ꢁ ꢁN , 2.23 A) and inter-molecular
H-bonding with two oxygen atoms of the non-coordinated
1
˚
nitrate group (–HN Hꢁ ꢁ ꢁO, 2.48, 2.56 A) while the second
hydrogen atom forms a strong intermolecular hydrogen
bonding with one oxygen atom of the second non-coordi-
1
˚
nated nitrate group (–HN Hꢁ ꢁ ꢁO, 2.29 A), forming an
eight membered cavity in the center. These interactions
result in the formation of a hydrogen-bonded tetramer.
The 1H NMR spectrum of compound 1 in CDCl3 (polar
solvent) shows the –N2H signal at d 10.53 ppm, which is
upfield relative to the free ligand. A single signal at d
8.75 ppm, is observed for –N1H2 proton, while second signal
is obscured by the multiplet signals due to the phenyl protons
Crystallographic data for 1: C59H55Ag2N5O6P4S,
˚
M = 1301.76, monoclinic, a = 25.057(2) A, b = 15.3627
˚
˚
(14) A, c = 31.365(3) A, a = 90°, b = 98.4040(10)°, c = 90°,
3
˚
V = 11944.1(18) A , T = 100(2) K, space group C2/c (No.
15),
q
calcd = 1.448 g cmꢀ3
,
Z = 8, l(Mo-Ka) = 0.850
mmꢀ1, 62,522 reflections measured on a Bruker X8 Kappa
Fig. 2. Packing diagram of complex 1.

1310
T.S. Lobana et al. / Inorganic Chemistry Communications 10 (2007) 1307–1310
[6] S. Kitagawa, M. Kondo, S. Kawata, S. Wada, M. Maekawa, M.
Munakata, Inorg. Chem. 34 (1995) 1455.
[7] E.Lozano,M.Nieuwenhuyzen,S.L.James,Chem.Eur.J.7(2001)2644.
[8] (a) L.A. Ashfield, A.R. Cowley, J.R. Dilworth, P.S. Donnely, Inorg.
Chem. 43 (2004) 4121;
APEXII diffractometer unique 12,282 (Rint = 0.0524). The
final R1 0.0672 was for 7030 reflections [I > 2r(I)] and wR2
was 0.1658.
Acknowledgement
(b) T.S. Lobana, G. Bhargava, V. Sharma, M. Kumar, Ind. J. Chem.
42A (2003) 309.
[9] (a) T.S. Lobana, S. Khanna, R.J. Butcher, A.D. Hunter, M. Zeller,
Polyhedron 25 (2006) 2755;
Financial support from CSIR, New Delhi, to one of us
(Sonia) is gratefully acknowledged.
(b) T.S. Lobana, Rekha, A. Castineiras, Inorg. Chem. Commun. 8
(2005) 1094;
Appendix A. Supplementary material
(c) T.S. Lobana, Rekha, R.J. Butcher, A. Castineiras, E. Bermejo,
P.V. Bharatam, Inorg. Chem. 45 (2006) 1535;
(d) T.S. Lobana, Rekha, R.J. Butcher, Transit. Metal. Chem. 29
(2004) 291;
(e) T.S. Lobana, G. Bawa, Ray J. Butcher, B.-J. Liaw, C.W. Liu,
Polyhedron 25 (2006) 2897.
CCDC 653471 contains the supplementary crystallo-
graphic data for compound 1. These data can be obtained
free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data _request/cif. Supple-
mentary data associated with this article can be found, in
the online version, at doi:10.1016/j.inoche.2007.08.005.
[10] K. Nakamoto, Infrared and Raman Spectra of Inorganic and
Coordination Compounds, Fifth ed., Wiley-Interscience Publication,
New York, 1997.
[11] F.B. Stocker, D. Britton, V.G. Young Jr., Inorg. Chem. 39 (2000) 3479.
[12] P. Aslanidis, P. Karagiannidis, P.D. Akrivos, B. Krebs, M. Lage,
Inorg. Chim. Acta 254 (1997) 277.
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