Tri-, hepta- and octa-nuclear Ag(i) complexes derived from 2-pyridyl-functionalized tris(amido)phosphate ligand

Article abstract of DOI:10.1039/c2dt30241a

Mild deprotonation of a 2-pyridyl (py)-functionalized phosphoric triamide [PO(NHpy)₃] in the absence of an external base was studied in the presence of various silver(i) salts. Interesting examples of octa- and hepta-nuclear Ag(i) complexes coordinated to imido and pyridyl groups were obtained when more reactive Ag(i) salts, such as AgClO₄ and AgBF ₄, were used, while the less reactive AgNO₃ reacts only with the peripheral pyridyl groups leading to a tri-nuclear cluster. Structural determination of these Ag(i) complexes show that sequential deprotonation of the ligand amino protons were achieved forming imido P(v) species analogous to the H₂PO₄^- and HPO₄^2- ions.

Full text of DOI:10.1039/c2dt30241a

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PAPER
Tri-, hepta- and octa-nuclear Ag(I) complexes derived from
2-pyridyl-functionalized tris(amido)phosphate ligand†
Arvind K. Gupta,a Alexander Steinerb and Ramamoorthy Boomishankar*a
Received 2nd February 2012, Accepted 31st May 2012
DOI: 10.1039/c2dt30241a
Mild deprotonation of a 2-pyridyl (py)-functionalized phosphoric triamide [PO(NHpy)3] in the absence
of an external base was studied in the presence of various silver(I) salts. Interesting examples of octa- and
hepta-nuclear Ag(I) complexes coordinated to imido and pyridyl groups were obtained when more
reactive Ag(I) salts, such as AgClO4 and AgBF4, were used, while the less reactive AgNO3 reacts only
with the peripheral pyridyl groups leading to a tri-nuclear cluster. Structural determination of these Ag(I)
complexes show that sequential deprotonation of the ligand amino protons were achieved forming imido
P(V) species analogous to the H2PO4− and HPO42− ions.
Introduction
Polyimido anions of the main group elements have been a topic
of interest for several research groups.1 These are isoelectronic
analogues of the common oxo anions and have been utilized as
ligands in coordination chemistry.2 In this context, phosphorus-
bound imido anions have received considerable attention.3 For
Fig. 1 N-analogues of various P(V) oxo anions.
example, the homoleptic imido analogues of the respective P(V)
oxo species H3PO4, H2PO4−, HPO4 and PO4 have been
obtained by the sequential deprotonation of the phosphonium
cation [(PhNH)4P]+ by n-butyllithium.4 Chivers and coworkers
have shown that tris(organoamino) phosphates of formula
(RNH)3PvE (E = NR′, O, S or Se) can be deprotonated with a
wide variety of organometallic bases, such as RLi, R2Zn, R2Mg
and R3Al (R is any alkyl or aryl group), generating interesting
examples of imido phosphate anions (Fig. 1). Formation of
multi-nuclear metal complexes have been envisaged in many of
these reactions, wherein the steric bulk on the imido ligands and
nature of the metal ions plays a vital role in controlling their
degree of oligomerization.5,6 Oxidation of some of these metal
complexes has been shown to form long-lived paramagnetic
radicals.7 In addition, metal complexes of several iminophos-
phoranes were implicated as catalytic systems for olefin oligo-
merization8 and polymerization,9 ring-opening polymerization
2−
3−
of lactides,10 hydroamination11 and transfer hydrogenation12
reactions. Previously, our group has been involved in synthesiz-
ing phosphonium cations of the formula [(RNH)4P]+, in the
presence of chloride, carboxylate and polyoxometalate anions,
in making designer supramolecular structures aided by hydrogen
bonding interactions.13 In view of the versatile coordination
abilities of the imino moiety, we were interested in looking at
imido P(V) ligands containing peripheral functional groups and
utilizing them for obtaining multi-metallic assemblies. In this
effort, we recently synthesized a tetra 2-pyridyl (py)-attached
phosphine imine [P(Npy)(NHpy)3] starting from the phos-
phonium salt [P(NHpy)4]Cl and showed that both of them
undergo deprotonation in presence of a silver salt (AgClO4),
yielding the homoleptic imido-phosphinate ion [P(Npy)2-
(NHpy)2]− (L1H2−) as a penta-nuclear [Ag5(L1H2)2]3+ com-
plex.14 In this paper, we report on the synthesis of two imido
P(V) species analogous to the dihydrogen phosphate [PO(Npy)-
(NHpy)2]− (LH2−) and mono hydrogen phosphate [PO(Npy)2-
(NHpy)]2− (LH2−) ions, as their octa-nuclear [Ag8(LH2)4]4+ (3)
and hepta-nuclear [Ag7(LH)3]+ (4) complexes, respectively.
These anions were generated in situ in the reactions involving
[PO(NHpy)3] (1) and the Ag(I) salts containing (ClO4−) and
(BF4−) anions. We also observed the formation of a tri-nuclear
aDepartment of Chemistry, Mendeleev Block, Indian Institute of Science
Education and Research (IISER), Pune, Dr. Homi Bhabha Road, Pune
411008, India. E-mail: boomi@iiserpune.ac.in; Fax: +91 2025908186
bDepartment of Chemistry, University of Liverpool, Crown Street,
Liverpool L69 7ZD, United Kingdom
†Electronic supplementary information (ESI) available: Selected bond-
lengths and angles, H-bonding table, 31P-NMR spectra, PXRD patterns
and addtional figures. CCDC 865262–865265 and 882870 for 1·C7H8,
2, 3 and 4. For ESI and crystallogrphic data in CIF or other electronic
format see DOI: 10.1039/c2dt30241a
[Ag3(LH3)2]3+ complex
2
in the reaction of
1
with
AgNO3 where phosphoric triamide 1 acts as a neutral (LH3)
ligand.
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Scheme 1 Reaction conditions for the preparation of the Ag(I) clusters.
Fig. 2 (a) The molecular structure of 2·3H2O showing the interaction
between the two tri-cationic motifs. Solvated water molecules have been
omitted for clarity. The central projection of the anti-clockwise (b) and
clockwise (c) rotation of the ligand arms in 2·3H2O.
Results and discussion
Synthesis
+1.5 (in addition to the free ligand peak at δ −4.9) indicating the
presence of both [PO(Npy)(NHpy)2]− and [PO(Npy)2(NHpy)]2−
ions, albeit in different ratios (Fig. S2, ESI†). These observations
point to the fact that both anionic species were formed in solu-
tion in the reactions involving 1 and AgClO4 or AgBF4. The
ESI-MS studies of the crystalline samples of 2, 3 and 4 in metha-
nol provided confirmation of the presence of the parent clusters
in solution (Fig. S3, ESI†). Thus, for 2 and 4, we observed
peaks at m/z 972.9 and 1726.5, corresponding to the species
[Ag3(LH3)2]3+ and [Ag7(LH)3]+, respectively. Similarly for 3, a
The precursor ligand 1, [PO(NHpy)3], was synthesized according
to our previously reported procedure, which involves the reaction
of POCl3 with an excess of 2-aminopyridine in refluxing
toluene.14 Spurred on by our earlier observation on the formation
of a homoleptic [P(Npy)2(NHpy)2]− ion, we set out to test the
mild deprotonation of 1 in the presence of various Ag(I) salts.
Accordingly, 1 was treated separately with an excess of AgOAc,
AgNO3, AgClO4, AgBF4, AgPF6, AgOTf and AgSbF6 under
similar reaction conditions. Typically, the reaction procedure
involves the slow diffusion of a solution of the Ag(I) salt in
methanol (methanol–water mixture in the cases of AgOAc and
AgNO3) to a solution of 1 in a methanol–chloroform–toluene
mixture. Crystalline products were obtained in three instances
where formation of 2·3H2O, 3·5CH3OH·3H2O and 4·H2O as col-
ourless crystals was observed within two weeks (Scheme 1). The
single crystal X-ray analysis showed the mono- and di-anions of
the type b and c (Fig. 1) were formed in the reactions involving
AgClO4 and AgBF4 salts, respectively. Whereas, deprotonation
of the ligand protons was not observed in the structure of 2
obtained in the reaction of 1 with AgNO3. The 31P-NMR (in
d6-DMSO) spectra of the metal complexes 2 (δ −5.2), 3 (δ +1.5)
and 4 (δ +9.3) are progressively shifted downfield and closely
match the literature reported values for the similar amido and
imido P(V) species. The 31P-CP-MAS NMR of the crystalline
samples of 2, 3 and 4 show less pronounced shifts than the
solution spectra and give single peaks centred at δ −2.08,
−1.78 and −0.95, respectively (Fig. S1, ESI†). In order to
understand the preferential formation of mono and di-anions
series of peaks at m/z 540.9, 759.1 and 1186.7 were observed,
n+
corresponding to {[Ag8(LH2)4](ClO4)4 − n
}
ions (n = 4, 3, 2).
In all of these cases, a major peak at m/z 433.0 was observed
matching the smallest fragment [Ag(LH3)]+. In addition, signals
corresponding to several prominent fragment ions, with different
Ag to ligand ratios, were found in all of these spectra.
Crystal structures
The compound 2·3H2O crystallized in the chiral monoclinic
space group P21. The asymmetric unit consists of two crystallo-
graphically independent tri-cationic cluster cores, six nitrate
anions and six molecules of water. The Ag(I) cations in 2·3H2O
are found in a two-coordinate environment and are bonded to
pyridyl nitrogens from two different ligands (Fig. 2a). The
Ag–N distances in 2·3H2O range from 2.14(2) to 2.203(17) Å,
and the N–Ag–N angles are between 168.0(6) and 177.4(8)°.
The cationic motif can be viewed as a trigonal bipyramidal cage
structure, in which the three Ag(I) centres form the equatorial
plane and the two P-atoms take up the axial sites. The average
Ag–Ag separation within the cluster is 6.050 (3) Å, closely
matching other [Ag3L2]3+ cages containing relatively bulky
tripodal ligands.15 Each [Ag3(LH3)2]3+ unit in 2·3H2O offers
−
(LH2 and LH2−) in reactions of Ag(I) salts, we separately
treated 1 (0.031 mmol) with an excess of AgClO4 (0.280 mmol)
and AgBF4 (0.298 mmol) in d6-DMSO (2 mL) under stirring
conditions. The 31P-NMR of the reaction mixture in each of
these reactions after three days showed two peaks at δ +9.3 and
9754 | Dalton Trans., 2012, 41, 9753–9759
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Fig. 3 (a) Aview of the octa-nuclear cluster in 3·5CH3OH·3H2O; (b) a
closer view of one of the four π–π stacked triads.
suitable binding pockets for three nitrate anions, which are held
closer to the cationic cluster via H-bonding interactions with the
amino protons. Furthermore, two of the three Ag(I) ions in each
tri-cationic cluster make long contacts with the nitrate oxygens
(av. Ag–O distance: 2.706(2) Å) that are housed at the adjacent
cluster unit leading to a 1D-chain structure. While the [Ag3L2]3+
type cages are well-documented for many tripodal N-donor
ligands,15,16 formation of such a molecule in the present
instance is driven by the relative reactivities of the Ag(I) salts.
The ligand moieties in 2·3H2O are C3-symmetric and resemble
the “Trie Cassyn” symbol of the Isle of Man flag. While one of
the ligands in a given [Ag3(LH3)2]3+ unit shows a clockwise
rotation (Δ) of its pyridyl arms, that of the other one shows an
anti-clockwise rotation (Λ) (Fig. 2b and c). Hence, each of the
tri-cationic motifs in the crystal structure of 2·3H2O is a
racemate.
3·5CH3OH·3H2O crystallized in the monoclinic space group
C2/c. The molecular core is comprised of the tetra-cationic
cluster of eight Ag(I) ions, which are held together by four
anionic (LH2−) ligands. The charge balance is restored by the
presence of four perchlorate anions that are disordered over five
positions. Each of the four anionic ligands of type b (Fig. 1)
binds to four Ag(I) ions through one imido and three pyridyl
nitrogens. All of the eight Ag(I) centres in 3·5CH3OH·3H2O
are involved in a linear coordination, in which two of them,
Ag1 and Ag2, are located inside the cluster core and bonded
solely with the imido groups. Thus, Ag1 is bonded to N3 and
N9 and Ag2 is bonded to N6 and N12, respectively. The remain-
ing six Ag(I) ions are situated along the corners of the cluster, as
two triangular units, and interact with the pyridyl nitrogens
(Fig. 3a). While the average Ag–Nimino distance in
3·5CH3OH·3H2O is 2.114(4) Å, the Ag–Npyridyl contacts are
found between 2.152(5) and 2.220(5) Å. The P–Nimino distances
(av. 1.605(4) Å) are marginally shorter than the other P–Namino
distances (av. 1.667(4) Å) indicating the delocalized nature
of the anionic charge inside the cluster. There are three short
Ag–Ag contacts viz., Ag1–Ag5: 2.752(6), Ag1–Ag2: 2.908(6)
and Ag2–Ag3: 2.764(6), connecting the two inner (Ag1 and
Ag2) and two outer (Ag3 and Ag5) cations. The phosphoryl
oxygens are intra-molecularly hydrogen bonded in a concerted
manner to one of the amino protons of the adjacent
imido phosphate ligands. The remaining amino groups are
Fig. 4 (a) The molecular structure of the hepta-nuclear cluster in
4·H2O; (b) an inner view of the Ag7 core; (c) formation of a 2D-hexa-
gonal sheet structure aided by H-bonding interactions.
hydrogen bonded to either perchlorate anions or the
solvated molecules (Fig. S6a, ESI†). Furthermore, the twelve
pyridyl rings of the four (LH2−) ligands, situated along the
cluster rims, form a set of four π–π stacked triads. Within
a given triad the inter-ligand π–π interaction is stronger
(av. 3.721(2) Å) than that of the intra-ligand (av. 4.098(2) Å)
interaction (Fig. 3b). Formation of a 3D-supramolecular assem-
bly was also observed as the outer Ag(I) centres form weak con-
tacts with disordered perchlorates and solvent molecules
(Fig. S6b, ESI†).
The crystal structure of 4·H2O was solved in the chiral hexa-
gonal space group R3. The asymmetric unit consists of one third
of the molecule where the ligand (LH2−) and two Ag(I) ions
(Ag1 and Ag2) take up the general positions. The third unique
Ag(I) centre, labelled Ag3, the tetrafluoroborate anion and the
water molecules sit at the three fold axis of symmetry and have
one third occupancies each (Fig. 4a). Each of the three ligands in
4·H2O is bonded to five Ag(I) ions through its two imido
(N1 and N2) and three pyridyl (N12, N22 and N32) nitrogens.
Three different types of coordination are found for the Ag(I) ion
in 4·H2O: an almost linear coordination for Ag1 (N1 and N12*),
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a tetra-coordination for Ag2 (N1, N2, N2** and N32) and a
nearly planar tri-coordination for Ag3 (N22, N22* and N22**).
While N1 forms the shorter (Ag1–N1: 2.140(7) Å) and the
longer (Ag2–N1: 2.697(7) Å) contacts to Ag(I) ions, N2 interacts
with two Ag2 ions at moderate distances (Ag2–N2: 2.286(7) Å
and Ag2*–N2: 2.393(7) Å). The Ag–Npyridyl distances are
similar to 2·3H2O and 3·5CH3OH·3H2O and range from
2.139(8) Å (Ag1–N12) to 2.331(16) Å (Ag2–N32). It is worth-
while to note the arrangement of seven Ag(I) ions in 4·H2O,
where the three crystallographically unique Ag centres are
located in different layers. While the first and second layers
contain the respective triangular arrays of Ag1 and Ag2 ions,
Ag3 forms the third layer and serves as the capping unit
(Fig. 4b). Thus, the structure of the cationic Ag7 core can be
viewed as a mono-capped distorted prism, in which the two tri-
angular units of Ag1 and Ag2 deviate by an angle of 11.9°. The
Ag–Ag distances in 4·H2O are found between 2.899(12) (Ag2–
Ag3) and 3.219(13) (Ag1–Ag1*) Å and compares closely to
those found in metallic silver (2.88 Å).17 In the solid-state the
molecules are arranged in the form of a 2D-hexagonal sheet
through hydrogen bonding interactions (Fig. 4c). The cationic
core consists of three Lewis-acidic NH sites that are bonded to
three anionic BF4 units through N–H⋯F H-bonding interactions.
In addition, the water molecules, disordered over three sites,
interact with the phosphoryl oxygens from the neighbouring
clusters.
Although there are a number of reports pertaining to the struc-
tures of hepta- and octa-nuclear Ag(I) clusters,18,19 most of them
have been obtained in the presence of soft chalcogen (S or Se)
or π-donor ligands. To the best of our knowledge, this is the first
report on such hepta- and octa-nuclear complexes containing all
nitrogen coordination. The observed mono- and di-deprotonation
of the ligand protons in these complexes is driven by the relative
reactivities of the Ag(I) salts, as well as the acidic nature of the
amino protons in 1 indicated by its pKa value of 4.01 in
MeOH.14 Further, the pyridyl rings of the ligands in 2, 3 and 4
are arranged in a mutually cis-fashion and involved in encapsu-
lating the cluster moieties. The PvO groups in all of these cases
are pointing away from cluster centre and remain non-coordinat-
ing. Interestingly, related cyclic phosphazenes have shown a
high affinity for silver(I), resulting in the formation of coordi-
nation polymers, which can accommodate up to five Ag(I) ions
per ligand.20
Fig. 5 Packing diagram of 1·C7H8.
in which solvated toluene molecules are occupied in the void
space (Fig. 5).
UV-visible and fluorescence spectra
The UV-visible spectra of the compounds 1, 2, 3 and 4 in
DMSO show single absorptions arising from the pyridylamino
chromophores and range between 282 nm (for 4) and 285 nm
(for 1) (Fig. 6a). These values are found to be red shifted in the
solid-state by about 50 nm (Fig. 6b) and range from 332 nm (for
1) to 337 nm (for 4), indicating that these transitions are predo-
minantly n → π* in nature. The solution emission spectra of the
ligand 1 and the complex 2 in DMSO show almost equal intensi-
ties and maxima at 325 nm. Similarly the emission maxima of 3
and 4 are nearly same at 328 and 330 nm, respectively, but show
a quenching of fluorescence intensities by a factor of 50%. The
solid-state fluorescence spectra of these compounds are again red
shifted by about 50 nm confirming the n → π* transitions and
ranges from 389 nm (for 1) to 397 nm (for 4) (Fig. 6d). Interest-
ingly, as we move from the free ligand 1 to the Ag(I) complexes
coordinated to neutral (2), mono-anionic (3) and di-anionic (4)
ligands, the fluorescence intensities in the solid-state decrease
progressively. Although such an effect can be expected in the
solution emission spectra as well, the presumable dynamic
nature of the Ag–N bonds in dilute solutions precludes such an
observation. The calculated quantum yields of 0.065 (for 1),
0.045 (for 2), 0.020 (for 3) and 0.018 (for 4) in DMSO solutions
are very low compared to the reference 2-aminopurine.
In one of the crystallization reactions involving 1 and AgOAc,
we observed the formation of a toluene adduct of 1 (1·C7H8),
instead of the expected Ag(I) complex. This is attributed to
the solvent incompatibilities of 1 and AgOAc under the
given reaction conditions, resulting in the crystallization of
1·C3H8. The structure of 1·C7H8 was obtained in monoclinic
P2(1)/c space group. The asymmetric unit consists of four mole-
cules of PO(NHpy)3 and four toluene molecules. The metric
parameters associated with P–N and PvO bonds are comparable
with the reported structures of 1.14,21 In the crystal structure
of 1·C7H8, two of the three amino protons in each ligand are
inter-molecularly interacting with two pyridyl nitrogens
forming a H-bonded dimer. These dimers are further connected
through the phosphoryl oxygens and the remaining amino
protons, leading to a chain structure (Fig. S7, ESI†). Interest-
ingly, the packing diagram of it shows a 1D-channel structure
Conclusions
In summary, we have synthesized interesting examples of tri-,
hepta- and octa-nuclear Ag(I) complexes starting from the
2-pyridyl-functionalized tris(amido) phosphate ligand. Utilizing
the slight variations in the reactivities of the Ag(I) salts, sequen-
tial deprotonation of the ligand amino protons were achieved
forming imido P(V) species analogous to the dihydrogen phos-
phate and mono hydrogen phosphate ions. The solid-state fluor-
escence spectra of the ligand and complexes show a sequential
quenching of fluorescence intensities from the free ligand to the
Ag(I) complex containing the di-anionic di-imido phosphate
ligand. Such an observation has been made for the first time in
imido-P(V) chemistry. Currently, work is in progress towards the
mild synthesis of imido-phosphate tri-anions analogous to the
PO43− ion using various reactive metal salts.
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Fig. 6 UV-visible spectra of the compounds 1–4 (a) in DMSO solution and (b) in the solid-state. Fluorescence spectra of the compounds 1–4 (c) in
DMSO solution (λex = 327 nm) and (d) in the solid-state (λex = 390 nm). All of the solution spectra were recorded at 10 μM concentration.
comparison with the emission of a solution of 2-aminopurine
(ΦR = 0.68) in H2O, employed as a standard.22 The excitation
wavelength used was 327 nm. The quantum yields were then
Experimental
General remarks
2
calculated using the expression, ΦS = ΦR(AS/AR)(nS /nR2). The
All manipulations involving phosphorus halides were performed
under a dry nitrogen atmosphere in standard Schlenk glassware.
Solvents were dried over potassium (hexane) and sodium
(toluene). 2-aminopyridine and silver(I) salts were purchased
from Aldrich and used as received. The halide precursor POCl3
was purchased locally (SPECTROCHEM, India) and was
distilled prior to use. NMR spectra were recorded on a Jeol
400 MHz spectrometer (1H NMR: 400.13 MHz, 13C{1H}NMR:
100.62 MHz, 31P{1H} NMR: 161.97 MHz) at room temperature
using SiMe4 (1H, 13C) and 85% H3PO4 (31P) as external stan-
dards. The solid-state (CP-MAS) 31P{1H} NMR spectra were
obtained on a Bruker 500 MHz spectrometer at a MAS rate of
10.0 KHz. The ESI-mass spectra in the positive ion mode were
recorded in a Waters-SYNAPT-G2 high resolution spectrometer.
UV-visible spectra were recorded by a Perkin-Elmer Lambda-35
spectrophotometer. The solid-state UV-visible spectra were
obtained from Perkin-Elmer Lambda-950 UV-Visible NIR spec-
trophotometer with 150 mm integrating sphere. The emission
spectra were obtained from Florolog-3 Horiba Jobin Vyon fluore-
scence spectrophotometer with a 450 W Xe lamp as the exci-
tation source. Emission quantum yields were determined by
subscripts S and R denote sample and reference respectively. Φ
is the fluorescence quantum yield, A is the integrated area under
the corrected fluorescence spectra and n is the refractive index
of the solvent. The solid-state emission spectra were obtained
from the front face mode. Elemental analyses were performed on
a Vario-EL cube elemental analyzer. FT-IR spectra were taken on
a Perkin Elmer spectrophotometer with samples prepared as KBr
pellets. Melting points were obtained using an Electro thermal
melting point apparatus and were uncorrected.
Synthesis
2·3H2O. To a solution of 1 (100 mg, 0.306 mmol) in metha-
nol (3 mL), containing a few drops of chloroform in a screw-
capped vial, toluene (1 mL) was added followed by a careful
layering of a solution of AgNO3 (78 mg, 0.460 mmol) in water
(3 mL). The resulting slightly cloudy solution was kept in the
dark for crystallization. Colorless block-like crystals were
obtained after 10 days. Yield 62% (113 mg, based on P). M. P.
1
180–182 °C, H NMR(400 MHz, {(CD3)2SO}): δ 6.95 (s, CH),
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Table 1 Crystallographic dataa
Compound
1·C7H8
15H15N6OP
2·3H2O
3·5CH3OH·3H2O
4·H2O
Chemical formula
Formula weight
Temperature
Crystal system
Space group
a (Å); α (°)
C
C30H36Ag3N15O14P2
1216.29
296(2)K
monoclinic
P21
14.0273(12); 90
22.194(2); 98.846(5)
14.8103(13); 90
4556.0(7); 4
1.773
C65H80Ag8Cl4N24O28P4
2774.17
296(2)K
monoclinic
C2/c
49.075(3); 90
13.2864(7); 90.737(2)
27.6363(15); 90
18 018.2(17); 8
2.045
C45H41Ag7BF4N18O4P3
1832.77
296(2)K
hexagonal
R3
14.1261(3); 90
14.1261(3); 90
24.5724(14); 120
4246.4(3); 3
2.150
418.43
200(2)K
monoclinic
P21/c
21.975(3); 90
17.625(2); 130.373(6)
29.216(3); 90
8620.7(18); 16
1.290
b (Å); β (°)
c (Å); γ (°)
V (Å3); Z
ρ (calc) mg m−3
μ (Mo Kα) mm−1
2θmax (°)
0.154
50
1.422
45
1.981
50
2.528
56
R(int)
0.1152
99.5%
15 154/1039
1.007
0.1091
98.7%
11 649/1004
1.002
0.0608
99.4%
15 842/903
1.002
0.0527
99.6%
4402/254
1.038
Completeness to θ
Data/param.
GOF
R1 [F > 4σ(F)]
wR2 (all data)
Flack parameter
0.0537
0.1414
—
0.698/−0.437
0.0929
0.2545
0.58(6)
1.911/−0.962
0.0438
0.1121
—
0.554/−0.686
0.0395
0.1226
—
1.181/−0.791
Max. peak/hole (e Å−3
)
a Refer to the ESI† for the tables of bond-lengths and angles and H-bonding.
7.18 (br, CH), 7.72 (br, CH), 8.16 (br, CH), 8.96 (s, NH):
13C {1H}} (100 MHz, {(CD3)2SO}): δ 113.23, 117.12, 139.15,
148.56, 154.24: 31P NMR (161 MHz, {(CD3)2SO}): δ −5.2;
FT-IR data in KBr pellet (cm−1): 3443, 3138 [ν (N–H)]; 510,
601, 629, 771, 824, 952, 994, 1053, 1098, 1154, 1207, 1242,
1295, 1384, 1445, 1487,1574, 1601 [ν (P–N)]; 1207, 1242
[ν (PvO)]; 647, 735 [ν (Ag–N)]. Anal. calcd for
C30H30N15O11P2Ag3: C, 31.00; H, 2.60; N, 18.08. Found: C,
31.74; H, 2.58; N, 17.85.
{(CD3)2SO}): δ 113.57, 115.26, 139.00, 148.69, 154.61:
31P NMR (161 MHz, {(CD3)2SO}): δ +9.3; FT-IR data in
KBr pellet (cm−1): 3189 [ν (N–H)]; 690, 748, 956, 1031, 1081,
1280, 1410, 1498 [ν (P–N)]; 1221 [ν (PvO)]; 647, 736, 750
[ν (Ag–N)]: Anal. calcd for C45H39BN18O3F4P3Ag7: C, 29.78;
H, 2.17; N, 13.89. Found: C, 30.11; H, 2.58; N, 13.85.
1. C7H8. To a solution of 1 (100 mg, 0.306 mmol) in metha-
nol (3 mL), containing a few drops of chloroform in a screw-
capped vial, toluene (1 mL) was added followed by a careful
layering of a solution of AgOAc (153 mg, 0.916 mmol) in water
(3 mL). The resulting slightly cloudy solution was kept in the
dark for crystallization, from which colorless block-like crystals
of 1 formed. C7H8 was obtained after 10 days. The analytical
and spectroscopic data of the sample dried at 60 °C under
vacuum matches with the reported values of 1.
3·5CH3OH·3H2O. To a solution of 1 (100 mg, 0.306 mmol)
in methanol (2 mL) and chloroform (1 mL) in a screw-capped
vial, toluene (1 mL) was added followed by a careful layering of
a solution of AgClO4 (127 mg, 0.612 mmol) in methanol
(3 mL). The resulting slightly cloudy solution was kept in the
dark for crystallization. Colorless block-like crystals were
obtained after 3 days. Yield 72%, (149 mg, based on P).
1H NMR(400 MHz, {(CD3)2SO}): δ 3.14 (s, CH3), 6.97 (br,
CH), 7.20 (br, CH), 7.74 (br, CH), 7.97 (br, CH), 8.24 (br, CH),
8.89 (s, NH): 13C {1H}} (100 MHz, {(CD3)2SO}): δ 113.51,
117.27, 139.36, 148.78, 154.23: 31P NMR (161 MHz,
{(CD3)2SO}): δ +1.5; FT-IR data in KBr pellet (cm−1): 3416,
3126 [ν (N–H)]; 636, 724, 775, 958, 1061, 1293, 1418, 1449,
1488, 1598 [ν (P–N)]; 1228 [ν (PvO)]; 1025 [ν (Ag–N)]. Anal.
calcd for C60H56N24O20P4Cl4Ag8: C, 28.13; H, 2.20; N, 13.12.
Found: C, 29.00; H, 2.74; N, 13.02.
Crystallography
Reflections were collected on a Bruker Smart Apex II diffracto-
meter at 296 K using MoKα radiation (λ = 0.71073 Å) for
2·3H2O, 3·5CH3OH·3H2O and 4·H2O. The data for 1·C7H8 were
collected on Bruker Smart Apex Duo diffractometer at 200 K
using MoKα radiation (λ = 0.71073 Å). Structures were refined
by full-matrix least-squares against F2 using all data (SHELX).23
Crystallographic data for 1·C7H8, 2·3H2O, 3.5CH3OH·3H2O and
4·H2O are listed in Table 1. All non-hydrogen atoms were
refined anisotropically, if not stated otherwise. Hydrogen atoms
were constrained in geometric positions to their parent atoms.
One of the toluene molecules in 1·C7H8 was disordered and was
refined isotropically over two sites. Crystals of 2·3H2O were
slightly opaque and diffracted only weakly lacking observed
reflections at higher angles and hence a 2θ cut-off at 45° was
applied. Although the overall connectivity is not in doubt, care
should be taken when evaluating bond lengths and angles. Due
to the poor quality of data, atom positions of the nitrate and
4·H2O. To a solution of 1 (100 mg, 0.306 mmol) in methanol
and chloroform (3 mL) in a screw-capped vial, toluene (1 mL)
was added followed by a careful layering of a solution of AgBF4
(149 mg, 0.765 mmol) in methanol (3 mL). The resulting
slightly cloudy solution was kept in the dark for crystallization.
Light yellow colored single crystals were obtained in two weeks.
1
Yield 60% (112 mg, based on P), M. P. 190–192 °C, H NMR
(400 MHz, {(CD3)2SO}): δ 6.88 (br, CH), 7.58 (br, CH), 8.1 6
(br, CH), 8.72 (br, CH), 8.87 (br, NH): 13C {1H}} (100 MHz,
9758 | Dalton Trans., 2012, 41, 9753–9759
This journal is © The Royal Society of Chemistry 2012

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water moieties were refined isotropically. The nitrate ions were
refined with similar-distance restraints and global similar-U
restraints were applied to all C, N and O atoms. The structure of
2·3H2O was refined as a racemic twin. In 3·5CH3OH·3H2O the
perchlorate anions and solvent molecules are severely disordered
along channels that run between the cationic complexes. NMR
data suggest that there are about 5 methanol and 3 water mole-
cules per formula unit. The perchlorate ions and solvent mole-
cules were treated as a diffuse contribution to the overall
scattering without specific atom positions by SQUEEZE/
PLATON. In addition, we also provide a model that attempts to
describe the disorder. Isotropic refinement with tight restraints
gave tetrahedral ClO4– ions, albeit with large thermal parameters;
electron difference peaks due to solvents where refined as
partially occupied oxygen atoms. In 4·H2O one pyridyl group is
disordered. It was split over two positions and refined iso-
tropically with occupancy factors and similar distance and similar
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–
U restraints. Both the BF4 anion and the lattice water molecule
–
are disordered over the 3-fold axis. The BF4 anion was refined
isotropically with similar distance and similar U-restraints.
Acknowledgements
This work was supported by the Department of Science and
Technology, India through Grant No. SR/FT/CS-014/2008
(R. B.) and IISER, Pune. We thank Dr T. S. Mahesh for provid-
ing help in obtaining solid-state NMR spectra.
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