Mixed-ligand silver(I) complexes containing bis[2-(diphenylphosphino)phenyl]ether and pyridyl ligands

Article abstract of DOI:10.1016/j.ica.2008.02.037

The reaction of [Ag₂(κ²-P,P′-DPEphos)₂(μ-OTf)₂] (1) (DPEphos = bis(2-(diphenylphosphino)phenyl]ether) with 1,10-phenanthroline (phen) and 4,4′-bipyridine in equimolar ratios afford, respectively, the mononuclear

Full text of DOI:10.1016/j.ica.2008.02.037

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Inorganica Chimica Acta 362 (2009) 271–276
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Note
Mixed-ligand silver(I) complexes containing
bis[2-(diphenylphosphino)phenyl]ether and pyridyl ligands
a,
a
b
*
Maravanji S. Balakrishna , Ramalingam Venkateswaran , Shaikh M. Mobin
a Phosphorus Laboratory, Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400 076, India
b National Single Crystal X-ray Diffraction Facility, Indian Institute of Technology Bombay, Mumbai 400 076, India
Received 13 December 2007; received in revised form 8 February 2008; accepted 19 February 2008
Available online 26 February 2008
Abstract
The reaction of [Ag2(j2-P,P0-DPEphos)2(l-OTf)2] (1) (DPEphos = bis(2-(diphenylphosphino)phenyl]ether) with 1,10-phenanthroline
(phen) and 4,40-bipyridine in equimolar ratios afford, respectively, the mononuclear complex [Ag(j2-P,P0-DPEphos)(phen)][OTf] (2) and
the coordination polymer [Ag(j2-P,P0-DPEphos)(l-4,40-bpy)]n[OTf]n (3). In complex 3, the silver atoms are bridged by 4,40-bipyridine
units to form a zigzag metallopolymer.
Ó 2008 Elsevier B.V. All rights reserved.
Keywords: Mixed-ligand silver complexes; DPEphos; Polypyridyl; Zigzag polymer; p-Stacking; Chelate mode of coordination
1. Introduction
2. Experimental
The coordination chemistry of large-bite bidentate
ligand, bis(2-(diphenylphosphino)phenyl) ether (DPEphos)
is extensively studied by Van Leeuwen and co-workers [1]
and others [2] due to its versatile coordination behavior
and its catalytic utility in a variety of organic transforma-
tions [3]. The tridentate nature of this ligand produces
interesting coordination architectures; often the ether-O
donor being hemilabile in nature. Recently we reported
the utility of DPEphos in ruthenium(II) [4], copper(I) [5]
and silver(I) complexes [6] and their reactivity and catalytic
applications of ruthenium derivatives. As a continuation of
our work on coordination chemistry [7] and catalytic appli-
cations [8] of phosphorus based ligands, herein we report
the mixed-ligand AgI complexes containing DPEphos and
pyridyl ligands such as phen and 4,40-bipyridine.
2.1. General considerations
All manipulations were performed under an atmosphere
of dry nitrogen using standard Schlenk techniques. All the
solvents were purified by conventional procedure and dis-
tilled under nitrogen prior to use. The ligand DPEphos
was prepared according to the published procedure [9].
The 1H and 31P{1H} NMR (d in ppm) spectra were
recorded using Varian 400 Mercury Plus spectrometer
operating at the appropriate frequencies using TMS and
85% H3PO4 as internal and external references, respec-
tively. Microanalyses were performed on a Carlo Erba
Model 1112 elemental analyzer. Electro-spray ionization
(EI) mass spectrometry experiments were carried out using
Waters Q-Tof micro-YA-105.
2.2. Syntheses
Synthesis of [Ag(j2-P,P0-DPEphos)(phen)][OTf] (2). A
solution of 1,10-phenanthroline (0.011 g, 0.063 mmol) in
CH2Cl2 (5 mL) was added dropwise to a stirring solution
*
Corresponding author. Tel.: +91 22 2576 7181; fax: +91 22 2576 7152/
2572 3480.
E-mail address: krishna@chem.iitb.ac.in (M.S. Balakrishna).
0020-1693/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2008.02.037

272
M.S. Balakrishna et al. / Inorganica Chimica Acta 362 (2009) 271–276
of 1 (0.050 g, 0.031 mmol) also in CH2Cl2 (10 mL) at room
temperature. After 4 h all the solvents were removed under
vacuum and the remaining white solid was recrystallized
from a 1:1 mixture of CH2Cl2 and Et2O. Yield: (0.056 g,
91%). M.p. >260 °C. Anal. Calc. for C49H36O4P2AgF3SN2
requires: C, 60.31;H, 3.72; N, 2.87; S, 3.29. Found: C,
60.37;H, 3.64; N, 2.98; S, 3.21%. dH (400 MHz, CDCl3)
6.81–7.32 (28H, m, Ph), 7.75 (2H, m, phen), 8.00 (2H, s,
phen), 8.50 (2H, dd, phen), 8.75 (2H, dd, phen). dP
2.3. X-ray crystallography
Single crystal of each compounds 2 and 3 suitable for X-
ray crystal analysis was mounted on a glass fiber with
epoxy resin. Crystal data for 2: C49H36AgF3N2O4P2S
ꢀ
(Mw = 975.67),
M
Triclinic, P1, a = 10.9310(7),
˚
b = 12.333(2), c = 16.9611(10) A, a = 90.723(9)°, b =
3
˚
99.418(5)°, c = 108.853(11)°, V = 2129.5(4) A , T =
150(2) K, Z = 2, qcalc = 1.522 g cmꢀ3, l (Mo Ka) = 0.659
mmꢀ1, F(000) = 992, reflections measured 31089, 12263
unique [Rint = 0.023], R1 = 0.0288, wR2 = 0.0758. Crystal
data for 3: C49H40AgCl3F3N2O4P2S (Mw = 1086.05), Tri-
109
107
(162 MHz, CDCl3) ꢀ8.4 (2d,
J
¼ 422 Hz; J
¼
AgP
AgP
367:5Hz). MS (EI): m/z 825.18 [MꢀOTf]+.
Synthesis of [Ag(j2-P,P0-DPEphos)(l-4,40-bpy)]n[OTf]n
(3). The procedure is similar to that of 2, using 1
(0.060 g, 0.038 mmol) and 4,40-bipyridine (0.012 g,
0.075 mmol). Complex 3 was recrystallized by using
CH2Cl2/Et2O mixture. Yield: (0.054 g, 76%). M.p.
>260 °C. Anal. Calc. for C47H36O4P2AgF3SN2 requires:
C, 59.32; H, 3.81; N, 2.94; S, 3.37. Found: C, 59.43;H,
3.88; N, 2.94; S, 3.41%. dH (400 MHz, CDCl3) 6.68–7.42
(28H, m, Ph), 7.57 (4H, m, bpy), 8.71 (4H, m, bpy). dP
(162 MHz, CDCl3) ꢀ10.2 (d, JAgP = 462.2 Hz). dP
˚
ꢀ
clinic, P1, a = 9.7780(12), b = 16.147(4), c = 16.211(5) A,
a = 89.47(2)°, b = 103.855(16)°, c = 105.407(16)°,
3
˚
V = 2391.7(10) A , T = 150(2) K, Z = 2, qcalc = 1.530 g
cmꢀ3, l (Mo Ka), mmꢀ1 = 0.754, F(000) = 1118, reflec-
tions measured 23383, 8393 unique [Rint = 0.063],
R1 = 0.0519, wR2 = 0.1262. Unit cell determination and
data collection of all the compounds were collected on
Oxford Diffraction XCALIBUR-S CCD system using
˚
Mo-Ka radiation (k = 0.71073 A). The structure was
(162 MHz, 233 K, CDCl3) ꢀ10.4 (2d, J1A0g9P ¼ 431 Hz;
solved and refined by full-matrix least-squares techniques
of F2 using the SHELX-97 (SHELXL program package) [10].
The absorption corrections were done by multi-scan and
all the data were corrected for Lorentz and polarization
effects. The non-hydrogen atoms were refined with aniso-
tropic thermal parameters. All the hydrogen atoms were
geometrically fixed and allowed to refine using the riding
model.
107
AgP
J
¼ 374:3 Hz).
Ph2
P
N
N
Ag
O
OTf
P
Ph2
3. Results and discussion
2
3.1. Metal complexes
1,10-Phenanthroline
DCM
The reaction between AgOTf with DPEphos in 1:1
molar ratio at room temperature produces a colorless crys-
talline solid of [Ag2(j2-P,P0-DPEphos)2(l-OTf)2] (1) in
good yield [6]. Although the triflate units anchor the sil-
ver(I) centers to stabilize complex 1, they are labile and
can be easily substituted with P- and N-donors. The
CF3
O
S
Ph2
Ph2
O
P
O
P
Ag
Ag
O
1/2
O
O
O
P
Ph2
O
mixed-ligand
complexes
[Ag(j2-P,P0-DPE-
P
Ph2
phos)(phen)][OTf] (2) and [Ag(j2-P,P0-DPEphos)(l-4,40-
bipy)]n[OTf]n (3) are synthesized in good yield by the reac-
tion of 1 with 1,10-phenanthroline and 4,40-bipyridine in
1:2 molar ratio at room temperature, respectively (Scheme
1). The 31P{1H} NMR spectrum of complex 2 at room tem-
perature consists of a pair of doublets centered at
S
F3C
1
4,4'-Bipyridine DCM
N
n
109
AgP
107
ꢀ8.4 ppm with J
and J
couplings of 422 and
AgP
1
368 Hz, respectively. The H NMR signals corresponding
to 1,10-phenanthroline are observed at 7.75, 8.00, 8.50
and 8.75 ppm with relative intensities. The EI mass spec-
trum of complex 2 shows molecular ion peak at m/z
825.18 [M]+ with appropriate isotopic pattern. The polynu-
clear silver(I) complex 3 presents phosphorus-31 signal at
ꢀ10.2 ppm as a broad doublet at room temperature,
whereas at ꢀ40 °C, it splits into two doublets centered at
Ph2
P
N
Ag
O
OTf
n
N
P
Ph2
N
3
109
AgP
107
Scheme 1.
ꢀ10.4 ppm with J
and J
couplings of 431 and
AgP

M.S. Balakrishna et al. / Inorganica Chimica Acta 362 (2009) 271–276
273
374 Hz, respectively, which is in agreement with the same
reported for analogous complexes of AgI containing two
phosphorus- and two nitrogen-donors [11,12]. The struc-
tures of complexes 2 and 3 have been confirmed by single
crystal X-ray crystallography. The coordination polymer
[Ag(j2-P,P0-DPEphos)(l-4,40-bpy)]n[OTf]n (3) is stable in
dry solvent medium. The presence of a trace amount of
moisture in the solution facilitates disproportionation reac-
tion to produce [Ag(j2-P,P0-DPEphos)2][OTf] and [Ag(l-
4,40-bpy)4]n[OTf]n. The former one was identified from its
31P NMR spectrum [6]. The polymeric compound [Ag(l-
4,40-bpy)2]n[OTf]n [13] has been obtained as an insoluble
white precipitate and identified from microanalysis.
3.2. Crystal structures of complexes 2–3
Perspective views of the molecular structures of com-
pounds 2 and 3 with the atom numbering schemes are
shown in the caption of Figs. 1–4, while selected bond
lengths and bond angles appear below the corresponding
figures.
In complexes 2 and 3, AgI atoms possess distorted tetra-
hedral geometry containing a chelating DPEphos ligand
and two nitrogen atoms from pyridyl ligands. Among the
two Ag–P bond distances in complexes 2 (2.4279(4) and
Fig. 1. Molecular structure of complex 2. Thermal ellipsoids are drawn at
50% probability level. Hydrogen atoms, phenyl rings attached to
phosphorus and uncoordinated solvent molecules have been omitted for
˚
˚
2.5242(5) A) and 3 (2.4179(14) and 2.5075(13) A), one is
˚
clarity. Selected bond distances (A) and bond angles (°): Ag1–N2 2.340(1),
short and the other is long. The Ag1–N1 and Ag1–N2
Ag1–P2 2.4279(4), Ag1–P1 2.5242(5), Ag1–N1 2.393(1), S1–O2 1.447(2),
S1–C49 1.815(3), F3–C49 1.285(3); N2–Ag1–P2 137.04(4), N2–Ag1–P1
106.93(3), P2–Ag1–P1 114.06(1), N2–Ag1–N1 70.90(5), P2–Ag1–N1
116.18(3), P1–Ag1–N1 95.06(4).
˚
bond distances in complex 2 are 2.340(1) and 2.393(1) A,
respectively, with a marginal difference of approximately
˚
0.05 A. In contrast, the Ag–N bond distances in complex
Fig. 2. Solid state structure of complex 2 showing intermolecular offset p-stacking interaction between two phen ligands of adjacent molecules.

274
M.S. Balakrishna et al. / Inorganica Chimica Acta 362 (2009) 271–276
Fig. 3. Molecular structure of complex 2. Thermal ellipsoids are drawn at 30% probability level. Hydrogen atoms, counter ions and uncoordinated solvent
˚
molecules have been omitted for clarity. Selected bond distances (A) and bond angles (°): Ag1–N1 2.352(4), Ag1–N2 2.368(4), Ag1–P2 2.4179(14), Ag1–P1
2.5075(13), S1–O2 1.431(4), N1–Ag1–N2 91.85(15), N1–Ag1–P2 119.35(9), N2–Ag1–P2 122.45(12), N1–Ag1–P1 104.69(11), N2–Ag1–P1 101.40(11), P2–
Ag1–P1 113.51(5), O2–S1–O3 114.36(32).
Fig. 4. Solid state packing pattern of complex 3. The counter ions, hydrogen atoms and uncoordinated solvent molecules have been omitted for clarity.
˚
˚
3 are almost similar, i.e., 2.352(4) and 2.368(4) A. The bite
is 3.82 A from the centroid of the C4C5C6C7C11C12 por-
angle of DPEphos ligand in complexes 2 and 3 are
114.057(15)° and 113.51(5)°, respectively, which are almost
identical. The bite angles of 1,10-phenanthroline ligands in
complex 2 is 70.90(5)°. Interestingly, the 1,10-phenanthro-
line group involves in intermolecular offset p-stacking
interactions [14] with another 1,10-phenanthroline ligand
of the neighboring molecule as shown in Fig. 2. The cen-
troid of the C1N1C12C2C3C4 portion of the phen ligand
tion of the phen ligand in the molecule at 1 ꢀ x, ꢀy, 2 ꢀ z
˚
and the offset of the latter from the former is 0.74 A (the
line joining the centroids makes an angle of 78.8°. with
the plane of the latter ring). There is also a p-stacking
between the phenyls C43–C48 in the molecules at x, y, z
and 1 ꢀ x, 1 ꢀ y, 2 ꢀ z with a centroid–centroid distance
˚
˚
of 3.66 A, and an offset of 0.73 A (the cent–cent line makes
an angle of 78.6° with the plane of the ring)

M.S. Balakrishna et al. / Inorganica Chimica Acta 362 (2009) 271–276
275
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The distance between two 1,10-phenanthroline planes is
˚
˚
3.361 A, which is approximately 0.25 A less than the anal-
ogous CuI complex [Cu(j2-P,P0-DPEphos)(phen)][BF4] in
the literature [9]. In complex 3, the 4,40-bipyridine units
are almost planar and bind as bridging ligands between
two silver(I) atoms and the chain grows as a one-dimen-
sional zigzag polymer as shown in Fig. 4. The Ag–N bond
distances in complex 3 are almost similar, i.e., 2.352(4) and
(c) S.-M. Kuang, P.E. Fanwick, R.A. Walton, Inorg. Chem. 41 (2002)
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0
˚
2.368(4) A. Both the 4,4 -bipyridine units sit on inversion
centers and are very close to being planar overall. The C–
C–C–C torsion angles about the central C–C bonds are
0.21° for the N1–N10 ligand and 1.9° for the N2–N20
ligand.
´
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4. Conclusions
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(2003) 12104;
In summary, the silver(I) complexes [Ag(j2-P,P0-DPE-
phos)(phen)][OTf] (2) and [Ag(j2-P,P0-DPEphos)(l-4,40-
bpy)]n[OTf]n (3) have been synthesized and structurally
characterized. Often, the 4,40-bipyridine units in coordina-
tion polymers are not coplanar but are twisted about the
C–C bond. The presence of extended conjugation between
metal and coplanar 4,40-bipyridine units induce the con-
ducting properties [15,16]. Hence, complex 3 may serve as
a good example for conducting metallopolymers in which
all the pyridyl rings of 4,40-bipyridine units are coplanar,
thus providing a conjugation through metal and bipyridine
units. Further work to look into these aspects is in
progress.
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(2001) 2615;
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(l) J.P. Wolfe, M.A.J. Rossi, Am. Chem. Soc. 126 (2004) 1620;
(m) R. Venkateswaran, M.S. Balakrishna, S.M. Mobin, Eur. J. Inorg.
Chem. (2007) 720.
[4] R. Venkateswaran, J.T. Mague, M.S. Balakrishna, Inorg. Chem. 46
(2007) 809.
[5] R. Venkateswaran, M.S. Balakrishna, S.M. Mobin, H.M. Tuononen,
Inorg. Chem. 46 (2007) 6335.
[6] M.S. Balakrishna, R. Venkateswaran, S.M. Mobin, Polyhedron 27
(2008) 899.
Acknowledgements
[7] (a) C. Ganesamoorthy, M.S. Balakrishna, P.P. George, J.T. Mague,
Inorg. Chem. 46 (2007) 848;
We are grateful to the Department of Science and Tech-
nology (DST), New Delhi, for funding. We also thank
Department of Chemistry and National Single Crystal X-
ray Diffraction Facility, IIT Bombay, for instrument facil-
ities. We are thankful to Prof. Joel T. Mague, Tulane Uni-
versity, for useful suggestions on structural aspects.
(b) M.S. Balakrishna, J.T. Mague, Organomeallics 26 (2007)
4677;
(c) P. Chandrasekaran, J.T. Mague, M.S. Balakrishna, Inorg. Chem.
44 (2005) 7925;
(d) P. Chandrasekaran, J.T. Mague, M.S. Balakrishna, Organome-
tallics 24 (2005) 3780;
(e) P. Chandrasekaran, J.T. Mague, M.S. Balakrishna, Inorg. Chem.
45 (2006) 5893;
Appendix A. Supplementary material
(f) M.S. Balakrishna, R. Panda, J.T. Mague, J. Chem. Soc., Dalton
Trans. (2002) 4617;
(g) M.S. Balakrishna, R. Panda, J.T. Mague, Polyhedron 22 (2003)
587.
CCDC 643888 and 643889 contain the supplementary
crystallographic data for 1. These data can be obtained free
of charge from The Cambridge Crystallographic Data Cen-
tre via www.ccdc.cam.ac.uk/data_request/cif. Supplemen-
tary data associated with this article can be found, in the
online version, at doi:10.1016/j.ica.2008.02.037.
[8] (a) S. Priya, M.S. Balakrishna, S.M. Mobin, R. McDonald, J.
Organomet. Chem. 688 (2003) 227;
(b) B. Punji, J.T. Mague, M.S. Balakrishna, Dalton Trans. (2006)
1322;
(c) B. Punji, C. Ganesamoorthy, M.S. Balakrishna, J. Mol. Catal. A:
Chem. 259 (2006) 78;
(d) B. Punji, J.T. Mague, M.S. Balakrishna, J. Organomet. Chem. 691
(2006) 4265;
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