Structural and spectroscopic characterization of silver(I) tribenzylphosphane complexes including chloro and bromo derivatives with unusual stoichiometries and an iodo complex with a Ag13I13 cluster core

Article abstract of DOI:10.1016/j.poly.2010.11.031

The reaction of tribenzylphosphane (PBn₃) with silver(I) halides, AgX (X = Cl, Br and I), afforded the cluster compound, [Ag ₁₃I₁₃(PBn₃)₆ ] (1), a low-yielding ionic salt, [Ag(PBn₃)₂]₈[AgCl ₃]Cl₆·6H₂O (2), and a non-stoichiometric compound, Ag_～11.5Br_～11.5(PBn₃) ₁₆·～5.5H₂O (3). As well, reactions with the appropriate Ag salt and PBn₃ in a 1:2 M ratio yielded [Ag(PBn ₃)₂]PF₆ (4), [Ag(PBn₃) ₂]BF₄ (5) and [Ag(PBn₃)₂Cl] ·0.33CHCl₃ (6) while [Ag(PBn₃)₂I] (7) was obtained when the ratio was 4:1. The iodo-cluster 1 has an onion-like structure with an iodide ion at its center surrounded trigonal-prismatically by an inner core of six silver ions. These silver ions are tetrahedrally coordinated to the innermost iodide ion and by six iodides that bridge to an outer layer of six silver ions which themselves are tetrahedrally coordinated by six bridging iodides and capped by the six PBn₃ ligands. The top of the onion features a silver ion with three iodo ligands arranged in a near-planar trigonal arrangement around it. Single crystal X-ray crystallography shows the complexes 2 and 3 to contain columns of discrete [Ag(PBn ₃)₂]⁺ cations with a linear P-Ag-P coordination, as also observed in the simple salts, 4 and 5, where the anion is [PF₆]^- and [BF₄]^-. The phenyl groups of PBn₃ swing back over the silver to generate a sixfold phenyl embrace. However, in 3, although the PBn₃ sites are fully occupied, about a quarter of the sixfold phenyl embraces are devoid of the object of their attention, the encapsulated silver ion. For 2, the [AgCl₃] ^2- anions are trigonal-planar, three-coordinated. For 3, the AgBr32-appear as motifs in an approximately 25% silver-deficient Ag ₄Br62-cluster. The crystal structures of the three-coordinate halides, 6 and 7, show that the geometry around the silver is close to a T-shape, with the chloride and iodide ions bound. The far-IR and ³¹P CP MAS NMR spectra of a selection of the new complexes confirm aspects of their symmetry as deduced from the crystallographic studies.

Full text of DOI:10.1016/j.poly.2010.11.031

Polyhedron 30 (2011) 638–646
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Structural and spectroscopic characterization of silver(I) tribenzylphosphane
complexes including chloro and bromo derivatives with unusual stoichiometries
and an iodo complex with a Ag13I13 cluster core
a
c
Eric W. Ainscough a, Graham A. Bowmaker b, Andrew M. Brodie a, , Graham H. Freeman , John V. Hanna ,
⇑
Geoffrey B. Jameson a, Carl A. Otter a
a Chemistry – Institute of Fundamental Sciences, Massey University, Private Bag 11 222, Palmerston North 4442, New Zealand
b Chemistry Department, University of Auckland, Auckland 1142, New Zealand
c Department of Physics, University of Warwick, Coventry CV4 7AL, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
The reaction of tribenzylphosphane (PBn3) with silver(I) halides, AgX (X = Cl, Br and I), afforded the clus-
Received 9 November 2010
Accepted 25 November 2010
Available online 2 December 2010
ter compound, [Ag13 13
I
(PBn3)6 ] (1), a low-yielding ionic salt, [Ag(PBn3)2]8[AgCl3]Cl6ꢀ6H2O (2), and a non-
stoichiometric compound, Agꢁ11.5Brꢁ11.5(PBn3)16ꢀꢁ5.5H2O (3). As well, reactions with the appropriate Ag
salt and PBn3 in a 1:2 M ratio yielded [Ag(PBn3)2]PF6 (4), [Ag(PBn3)2]BF4 (5) and [Ag(PBn3)2Cl]ꢀ0.33CHCl3
(6) while [Ag(PBn3)2I] (7) was obtained when the ratio was 4:1. The iodo-cluster 1 has an onion-like
structure with an iodide ion at its center surrounded trigonal-prismatically by an inner core of six silver
ions. These silver ions are tetrahedrally coordinated to the innermost iodide ion and by six iodides that
bridge to an outer layer of six silver ions which themselves are tetrahedrally coordinated by six bridging
iodides and capped by the six PBn3 ligands. The top of the onion features a silver ion with three iodo
ligands arranged in a near-planar trigonal arrangement around it. Single crystal X-ray crystallography
shows the complexes 2 and 3 to contain columns of discrete [Ag(PBn3)2]+ cations with a linear P–Ag–P
coordination, as also observed in the simple salts, 4 and 5, where the anion is [PF6]ꢂ and [BF4]ꢂ. The phe-
nyl groups of PBn3 swing back over the silver to generate a sixfold phenyl embrace. However, in 3,
although the PBn3 sites are fully occupied, about a quarter of the sixfold phenyl embraces are devoid
of the object of their attention, the encapsulated silver ion. For 2, the [AgCl3]2ꢂ anions are trigonal-planar,
Keywords:
Silver(I) complexes
Tribenzylphosphane
X-ray diffraction
2ꢂ
2ꢂ
three-coordinated. For 3, the AgBr3 appear as motifs in an approximately 25% silver-deficient Ag4Br6
cluster. The crystal structures of the three-coordinate halides, 6 and 7, show that the geometry around
the silver is close to a T-shape, with the chloride and iodide ions bound. The far-IR and 31P CP MAS
NMR spectra of a selection of the new complexes confirm aspects of their symmetry as deduced from
the crystallographic studies.
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
neutral monomeric complexes [Au(PBn3)X] (X = Cl and Br) are ob-
tained, but parallel attempts to prepare the iodo analog resulted in
Tribenzylphosphane (PBn3) is an easily oxidized bulky ligand
with a Tolman cone angle of 165° compared to 145° for PPh3 and
it is also more basic with the pKa of its conjugate acid being 2.7
compared to ꢁ6.0 for PPh3 [1]. The conformationally flexible ben-
zyl groups are also be expected to influence the coordination
chemistry of PBn3. This has been observed for complexes of cop-
per(I), where, instead of neutral [Cu(PR3)X]n phosphane complexes
(n = 1, 2 or 4 depending on the steric bulk of the PR3 ligands) [2],
rearrangement occurs, so that ionic compounds of the form
[Cu(PBn3)2][CuX2] (X = Cl and Br) are obtained in the solid state
with linear [Cu(PBn3)2]+ cations [3]. For gold(I), the two-coordinate
the isolation of the oxide, Bn3PO [4]. However, the monomeric io-
nic complex [Au(PBn3)2]I could be isolated, as well as the related
[Au(PBn3)2]X (X = Cl and BF4) compounds, all of which contain lin-
ear [Au(PBn3)2]+ cations with non-coordinated anions. The driving
force for the formation of ionic adducts has been ascribed to inter-
ligand ‘embraces’ within the linear two-coordinate cation, which
prevents secondary coordination of the counterion to the metal
ion [3b,4].
We were interested in extending our work with PBn3 to study
the nature of the complexes formed with the third member of
the triad, namely silver(I). This report describes the synthesis and
structural characterization of a series of compounds showing the
structural flexibility of silver leading to a variety of new compound
types. For example, from the reaction of tribenzylphosphane with
⇑
Corresponding author. Tel.: +64 63569099; fax: +64 63505682.
E-mail addresses: e.ainscough@massey.ac.nz (E.W. Ainscough), a.brodie@mas-
sey.ac.nz (A.M. Brodie), g.b.jameson@massey.ac.nz (G.B. Jameson).
0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.11.031

E.W. Ainscough et al. / Polyhedron 30 (2011) 638–646
639
AgI in an approximately 1:2 M ratio an unusual onion-like cluster,
[Ag13I13(PBn3)6 ] (1), crystallizes from the reaction. It is well known
that in the presence of phosphanes, silver(I) salts, AgX (X = halide
or pseudohalide), readily form a range of clusters. Some of the
smaller ones contain, for example, Ag5 [5], Ag6 [6], Ag7 [7], Ag8
cooled solution was filtered to remove unreacted AgI. Slow diffu-
sion of pentane vapor into the filtrate afforded colorless crystals
suitable for X-ray analysis. Yield: 69 mg, 26%. Mp 200–203 °C
dec. Anal. Calc. for C126H126Ag13I13P6: C, 31.00; H, 2.60. Found: C,
31.73; H, 2.57%.
[6a,8], Ag9 and Ag10 [9] and Ag12 [10] and there other larger units,
4ꢂ
for example in the anion [Ag50S7(SC6H4But-4)40
]
[11], but a
2.2.2. Octa{bis(tribenzylphosphane)silver(I)} trichloroargentate(I)
chloride hexahydrate, [Ag(PBn3)2]8[AgCl3]Cl6ꢀ6H2O (2)
‘stand-alone’ Ag13 unit has not been reported previously, although,
in the presence of CO, an Ag13 unit is found in the bimetallic tetra-
Tribenzylphosphane (0.10 g, 0.33 mmol) and AgCl (0.475 g,
3.31 mmol) were refluxed in 5 cm3 chloroform for 1 h. The cooled
solution was filtered to remove unreacted AgCl and the filtrate was
transferred to a vial and sealed in a jar with pentane. The jar was
stored in the dark overnight and small cubic colorless crystals as
well as clumps and needles formed around the side of the vial.
The product was a mixture and the near cubic crystals were ana-
lyzed by X-ray crystallography.
anion, [Ag13Fe8(CO)32]
4ꢂ, which features a centered cuboctahedral
stereogeometry [12] that resembles a fragment of the cubic
face-centered structure of the bulk metal. In other studies, semi-
empirical and ab initio calculations on a Ag13 nanoparticle favor a
buckled biplanar structure [13], whereas in the polymeric
3ꢂ
structure of the {[Ag13
(l-SC5H9NHMe)16
]
}
n
cation, Ag10S16 units
are linked by three silver atoms [14]. Coordination-based self-
assembly is an effective way to prepare clusters with unusual
structures, and steric bulk can be exploited to produce stable cores,
protected by a shell of ligands from self aggregation. The geometry
2.2.3. Agꢁ11.5Brꢁ11.5(PBn3)16ꢀꢁ5.5H2O (3)
Tribenzylphosphane (0.40 g, 1.31 mmol) and AgBr (0.124 g,
0.66 mmol) were refluxed in 20 cm3 chloroform for 30 min. The
cooled solution was filtered to remove unreacted AgBr and the fil-
trate reduced in volume by half under reduced pressure, then hex-
ane was added until the solution just went cloudy. The flask was
allowed to stand overnight in the dark to yield 0.35 g of colorless
crystals. Slow diffusion of hexane vapor into a chloroform solution
afforded colorless chunky crystals suitable for X-ray analysis. The
precipitate also contained crystals of tribenzylphosphane oxide.
of the Ag13 core in [Ag13I13(PBn3)6 ] (1) is different from the previ-
ous cases, and consists of a non-centered distorted threefold axi-
ally symmetric capped prismane-like structure that illustrates
the plasticity of not only the silver but also the iodo coordination.
No complexes of the type [Ag(PR3)X]4 (X = Cl, Br or I) were isolated
[15], instead the preferences were for the following stoichiome-
tries: [Ag(PBn3)2]8[AgCl3]Cl6ꢀ6H2O (2), the non-stoichiometric
complex Agꢁ11.5Brꢁ11.5(PBn3)16ꢀꢁ5.5H2O (3) – for which only the
tribenzylphosphane sites are fully occupied – as well as the mono-
metallic species, [Ag(PBn3)2]X [X = BF4 (4) and PF6 (5)] and
[Ag(PBn3)2X] [X = Cl (6) and I (7)]. All have been crystallographi-
cally characterized, 1, 2 and 3 proving particularly complex. The
[Ag(PBn3)2X] complexes display distorted T-shaped coordination
spheres whereas the [Ag(PBn3)2)]X species, as well as [Ag(PBn3)2]8
[AgCl3]Cl6ꢀ6H2O and Agꢁ11.5Brꢁ11.5(PBn3)16ꢀꢁ5.5H2O, all feature
linearly or near-linearly coordinated [Ag(PBn3)2)]+ cations similar
to those found for copper and gold [3,4]. The structures of 2 and
3 contain [AgCl3]2ꢂ and [AgBr3]2ꢂ anions respectively, along with
water and the appropriate ionic halide (to balance charge) in the
lattice. The far-IR and 31P CP MAS NMR spectra are also reported
for several compounds and discussed in relation to their structure
and bonding.
2.2.4. Bis(tribenzylphosphane)silver(I) hexafluorophosphate,
[Ag(PBn3)2](PF6) (4)
Tribenzylphosphane (0.3 g, 0.99 mmol) and [Ag(CH3CN)4]PF6
(0.206 g, 0.49 mmol) were refluxed in 20 cm3 chloroform for
15 min and a white product was filtered from the cooled reaction
mixture and washed well with acetonitrile. The crude product
was recrystallized from nitromethane to give colorless crystals
suitable for X-ray analysis. Yield: 34 mg, 8%. The crystals start to
darken about 280 °C and decomposed at 330–340 °C. Anal. Calc.
for C42H42AgF6P3: C, 58.53; H, 4.92. Found: C, 58.21; H 4.97%.
2.2.5. Bis(tribenzylphosphane)silver(I) tetrafluoroborate,
[Ag(PBn3)2](BF4) (5)
2. Experimental
Tribenzylphosphane (0.4 g, 1.31 mmol) and AgBF4 (0.128 g,
0.66 mmol) were refluxed in 20 cm3 chloroform for 1 h and the
white product filtered from the cooled reaction mixture. The crude
product was recrystallized from nitromethane to give colorless
crystals suitable for X-ray analysis. Yield: 87 mg, 16%. The crystals
start to darken about 280 °C and decomposed at 330–340 °C. Anal.
Calc. for C42H42AgBF4P2: C, 62.75; H, 5.27. Found: C, 62.04; H,
5.38%.
2.1. General
Analytical grade solvents were used without purification. Tri-
benzylphosphane (Bn3P) and the silver halide salts were obtained
from the Sigma–Aldrich Co. and [Ag(MeCN)4]PF6 was prepared
using the method [16] described for the analogous copper(I) com-
plex. Although all reactions were carried out under an atmosphere
of dinitrogen, the presence of adventitious water or oxygen during
the crystallization of 2 and 3 resulted in the inclusion of H2O
molecules in the lattice and in the case of 3, some oxidation of
the tribenzylphosphane. All the new compounds were soluble in
chloroform. Microanalyses were performed by the Campbell
Microanalytical Laboratory, University of Otago. Compounds 2
and 3 were characterized crystallographically since they could only
be obtained in low yield along with other reaction products.
2.2.6. Chlorobis(tribenzylphosphane)silver(I) 0.33chloroform,
[Ag(PBn3)2Cl]ꢀ0.33CHCl3 (6)
Tribenzylphosphane (0.40 g, 1.31 mmol) and AgCl (0.094 g,
0.66 mmol) were refluxed in 20 cm3 of chloroform under nitrogen
for one hour. The cooled solution was filtered to remove unreacted
AgCl and the filtrate reduced in volume by half under reduced
pressure then hexane added until the solution just went cloudy.
After standing overnight, the product was obtained as fine white
needles. Yield: 0.342 g, 66%. Mp 173–180 °C. Anal. Calc. for
2.2. Compound preparation
C
42H42AgClP2ꢀ0.33CHCl3: C, 64.22; H, 5.40. Found: C, 64.23; H,
2.2.1. Triskaidekaiodohexa(tribenzylphosphane)triskaidekasilver(I),
[Ag13I13(PBn3)6] (1)
5.80%. Slow diffusion of hexane vapor into a chloroform solution
afforded white needles suitable for X-ray analysis. The discrepancy
between the analytical data and the X-ray structure indicates the
lattice CHCl3 is readily lost.
Tribenzylphosphane (0.1 g, 0.33 mmol) and AgI (0.17 g,
0.71 mmol) were refluxed in 10 cm3 chloroform for 1.5 h. The

640
E.W. Ainscough et al. / Polyhedron 30 (2011) 638–646
2.2.7. Iodobis(tribenzylphosphane)silver(I), [Ag(PBn3)2I] (7)
PBn3 (0.1 g, 0.33 mmol) and AgI (0.34 g, 1.45 mmol) were re-
fluxed in 3 cm3 chloroform under nitrogen for 6 h. The cooled solu-
tion was filtered to remove unreacted AgI. Slow diffusion of
pentane vapor into the filtrate afforded colorless elongated crystals
suitable for X-ray analysis. Yield: 18 mg, 13%. Mp 155–160° dec.
Anal. Calc. for C42H42AgIP2: C, 59.78; H, 5.02. Found: C, 59.19; H,
5.04%.
disordered about the –3 (S6) center. Assuming 3 (C3) symmetry
and inversion disorder on the AgI cluster led to the novel but
chemically sensible cluster (PBn3)6(AgI)13. Refinement converged
very cleanly to a value for R1 (observed data) of 0.0318. Although
residual electron density is concentrated within the cluster near
the I and Ag sites, indicating that, perhaps, overall symmetry is
ꢀ
lower than 3 (C3), refinements in space group R1 (both with and
without twinning) did not improve the model.
2.3. X-ray data collection and refinement
2.3.2. [Ag(PBn3)2]8[AgCl3]Cl6ꢀ6H2O (2)
The diffraction data could be merged with acceptable statistics
into crystals systems cubic and lower, although there was a small
but significant difference in one axis compared to the other two.
Ignoring the numerous systematic absence violations, refinements
in space group Pnnn died at R1 ꢁ 0.21 (even allowing for trilling).
(Note: Pnnn was the initially chosen space group of the bromide
(3) for which the unit cell is almost identical to that for this chlo-
ride derivative.) Structure elucidation was then pursued in space
group P21212, again ignoring systematic absence violations, but
similarly to attempts in space group Pnnn, the benzyl moieties
were not discernable in electron density maps. To facilitate com-
parison with the bromide analog, successful structure solution
and refinement were conducted in a non-standard setting of
P222. Stable refinement was achieved in space group P222 with
pseudo-merohedral trilling [twin law 0 1 0/0 0 1/1 0 0, and final
refinement of twin components giving 0.147(58), 0.260(60),
0.184(64), 0.229(58), 0.103 (60) and 0.076, the high errors the re-
sult of allowing for inversion twinning]. As for the bromide, a dis-
The X-ray data were collected on a Siemens P4 four-circle dif-
fractometer, using a Siemens SMART 1K CCD area detector. The
crystals were mounted in an inert oil and irradiated with graphite
monochromated Mo K
a (k = 0.71073 Å) X-rays. The data were
collected by the SMART program and processed with SAINT to apply
Lorentz and polarization corrections to the diffraction spots
(integrated 3 dimensionally). Crystal data are given Table 1. The
structures of 4–7 were solved by direct methods and refined using
the SHELXTL program [17].
2.3.1. [Ag13I13(PBn3)6] (1)
The Ag–PBn3 moiety was readily decipherable from the top di-
rect methods’ solution; however, the cluster of 6 large peaks at and
around the ꢂ3 (S6) site was not so readily interpretable. Constrain-
ing all peaks to have a common isotropic displacement parameter
and assigning to each peak a free variable describing the fractional
occupancy, xj, by atom Ij, with fractional occupancy of atom Agj
constrained to 1 ꢂ xj, yielded an unambiguous assignment of each
peak as either silver or iodine atoms, as well as the total occupancy
of the site. Identity of atom and fractional occupancy of these sites
were also substantiated in refinements in which the atomic
displacement parameter at each site was subject only to the
constraint that it was equal for each Ag/I pair. With two Ag atoms
being unacceptably close and occupying general positions with
only half occupancy, it was concluded that the structure was
2ꢂ
ordered AgCl3 cluster disports itself about a 222 site, but yields
an apparent X4Y6 cluster, where the Y species, sitting on crystallo-
graphic twofold axes, are present, each in half occupancy, and the
Ag+ ion, sitting in a general position is present in quarter occu-
pancy. At other 2 and 222 sites chloride ions are found. These to-
gether with a chloride ion in a general position, give an overall
Ag:Cl:P ratio of 9:9:16. Because of high correlation among param-
eters resulting from the intrinsic tetragonal pseudo-symmetry and
Table 1
Crystal and refinement data for the complexes.
Compound
[Ag13I13(PBn3)6]
(1)
[Ag(PBn3)2]8[AgCl3]Cl6ꢀ6H2O Agꢁ11.5Brꢁ11.5(PBn3)16ꢀꢁ5.5H2O [Ag(PBn3)2]PF6
[Ag(PBn3)2]BF4
(5)
[Ag(PBn3)2Cl]ꢀCHCl3
(6)
(2)
(3)
(4)
Molecular
formula
C
126H126Ag13I13P6 C336H348Ag9Cl9O6P16
C336H347Ag11.5Br11.5O5.5P16
C42H42AgF6P3
C42H42AgBF4P2
C43H43AgCl4P2
Molecular weight
T (K)
Crystal system
Space group
a (Å)
4878.12
200(2)
6267.52
200(2)
orthorhombic
P222
19.722(4)
19.722(4)
19.738(4)
90
7117.04
200(2)
tetragonal
P4/nnc
19.647(3)
19.647(3)
19.745(4)
90
861.54
203(2)
803.38
203(2)
871.38
203(2)
monoclinic
P21/c
9.8401(2)
20.7137(5)
20.3865(3)
90
rhombohedral
monoclinic
C2/c
14.68490(10)
13.6436(2)
19.6266(2)
90
monoclinic
C2/c
14.1182(4)
13.6580(3)
19.5086(5)
90
ꢀ
R3
17.4433(4)
17.4433(4)
39.8703(13)
90
b (Å)
c (Å)
a
(°)
b (°)
90
120
10506.0(5)
3
90
90
7677(3)
1
90
90
7622(2)
1
90.5370(10)
90
3932.11(8)
4
92.4340(10)
90
3758.38(17)
4
91.6780(10)
90
4153.49(14)
4
c
(°)
V (Å3)
Z
l
(Mo K
a
)
)
4.750
0.779
2.369
0.693
0.671
0.849
(mmꢂ1
qcalc (g cmꢂ3
2h max (°)
)
2.313
50
5235
1.356
50.16
13,490
1.551
49.42
3395
1.455
55
4332
1.420
54.84
4120
1.393
54.84
9131
No. of unique
reflections
Data/restraints/
parameters
Final R indices
5235/0/249
13,490/1461/882
R1 = 0.0697, wR2 = 0.1590
R1 = 0.1273, wR2 = 0.1901
1.123
3395/0/229
4332/0/237
4120/47/244
9131/36/479
R1 = 0.0313,
wR2 = 0.0783
R1 = 0.0616, wR2 = 0.1640
R1 = 0.0982, wR2 = 0.1952
1.014
R1 = 0.0246,
wR2 = 0.0661
R1 = 0.0279,
wR2 = 0.0677
1.052
R1 = 0.0289,
wR2 = 0.0709
R1 = 0.0353,
wR2 = 0.0743
1.028
R1 = 0.0289,
wR2 = 0.0709
R1 = 0.0624,
wR2 = 0.0983
1.128
[I > 2r(I)]
R indices (all data) R1 = 0.0435,
wR2 = 0.0837
Goodness of fit on 1.041
F2

E.W. Ainscough et al. / Polyhedron 30 (2011) 638–646
641
exacerbated by the trilling into cubic pseudo-symmetry, mild
damping and moderate restraints on atomic displacement param-
eters had to be employed to achieve stable non-oscillatory conver-
gence. In addition, benzyl moieties were restrained to standard
geometry. The final R1(observed data) of 0.0697 is commensurate
with the intrinsic quality of the diffraction data.
0 ¼ ðþ1Þð2Þð0:5Þð0:765ð3ÞÞ ½Agþ in AgðPBn3Þ ꢃþ
2
ðþ1Þð2Þð0:25Þð1:354ð10ÞÞ ½Agþ in X8Y6 moietyꢃþ
ðꢂ1Þð3Þð0:5Þð0:932ð4ÞÞ ½Brꢂ in X8Y6 moietyꢃþ
ðꢂ1Þð1Þð0:25Þð0:178ð11ÞÞ ½Brꢂ at 222 siteꢃ:
There are eight [Ag0.765(PBzn)2]+0.765 moieties per cell and approxi-
mately two pairs of pairs of AgBr3 moieties with disordered Ag+
2ꢂ
2.3.3. Agꢁ11.5Brꢁ11.5(PBn3)16ꢀꢁ5.5H2O (3)
ions per cell. Full occupancy of this site would lead to 12 Brꢂ and
4 Ag+ per cell; 11.16 Brꢂ are observed and 5.42 Ag+. Immediately
adjacent cation sites (X) of the apparent X8Y6 moiety are separated
by only 2.0 Å and cannot, therefore, be simultaneously occupied.
The excess Ag+ ions, however, requires that in addition to the pairs
of body-diagonally related Ag+ ions there is also a significant frac-
tion of face-diagonally related Ag+ ions in the cluster. The final ratio
of Ag:Br:P is 11.55:11.55:16. Forcing whole-number stoichiometric
ratios (e.g. 12:12:16) led to higher values for R1, as well as patterns
of positive and negative peaks consistent with deficits and sur-
pluses of electron density. The final difference Fourier map was flat
and featureless. Because of the high degree of pseudo-merohedral
twinning (twin law 0 1 0/0 0 1/1 0 0 with refined twin components
of 0.219(4) and 0.316(2) and 0.465), false/ghost atoms appeared at
special positions in early electron density maps and changes in
atomic displacement parameters were often highly correlated,
especially for atoms on special positions. Stability of refinement
was improved when the geometry of the benzyl groups was re-
strained by use of free variables. Once the disorder model for the
In addition to systematic absences consistent with space group
Pnnn, there is considerable pseudo-symmetry apparent in the cell
metric with a and b axes indistinguishably different, and the c axis
being only 0.1 Å (ꢁ0.5%) longer than the a and b axes. Moreover,
the diffraction data show considerable pseudo-symmetry, with
barely unacceptable statistics for merging of data into tetragonal
ꢀ
P4/mmm or cubic Pm3m Laue groups (Rint = 0.086 and 0.092,
respectively, compared to 0.072 for merging into Pmmm). Finally,
reflections h + k + l = 2n + 1 are systematically much weaker than
average and reflections hhl, hkh and hll are only weakly observed.
ꢀ
In either orthorhombic, tetragonal (P4/nnc) or cubic (Pn3m) space
groups, the [Ag(PBn3)2]+ moiety was readily discerned. A Y8X6 clus-
ter, where the eight Y sites form the vertices of a cuboid and the six
X sites cap each face, was also apparent and defied facile interpre-
tation. Electron density maps and subsequent refinement allowed
X to be identified as Br. Requirements of electroneutrality dictated
that site Y contained silver, possibly an [Ag4Br6]2ꢂ cluster, with Ag+
occupying alternate corners of the cube, and with Ag+ then disor-
dered about a 222 site, leading to [Ag(PBn3)2]2[Ag4Br6]. However,
this species was (i) inconsistent with crystal packing, which had
eight [Ag(PBn3)2] units per cell, requiring tetra-anionic species at
the two anion sites per cell, (ii) had unnaturally acute bridging
Ag–Br–Ag angles of ꢁ60o, and (iii) on refinement led to values
for R1 (observed data) of more than 0.13 for models assuming no
twinning, twinning into pseudo-tetragonality (hkl and khl super-
imposed) or twinning into pseudo-cubicity (hkl, lhk and klh super-
imposed) with substantial residual electron density, both positive
and negative in the vicinity of Ag and Br sites, and at the other
three sites of 222 point symmetry. Refinement of occupancies of
all Ag and Br sites, with tight restraints on electroneutrality, led
to considerable improvement in the value for R1 to 0.093 for the
cubic ‘‘trilling’’, with the Y8X6 cluster being made up of a pair of
disordered AgBr3 cluster, for the partly occupied lone Brꢂ site
2ꢂ
and for the incomplete occupancy of the Ag+ site of the [Ag(PBn3)2]
moiety was deciphered, final refinements converged smoothly. The
final value for R1 (observed data) is 0.0707. The crystal packing of
this material is distinctly different to the chloride analog, which is
in the subgroup P222 of Pnnn. Although the arrangement of the
[Ag(PBn3)2] moieties is essentially identical, the bromide features
two disordered AgBr3 ions per cell and a partially occupied Brꢂ
2ꢂ
site, giving a (AgBr)11.55 stoichiometry. In contrast, the chloride ana-
log (2) has exact stoichiometry Ag:Cl:P of 9:9:16. However, close
metrical relationships among atoms led to final refinements being
performed in the higher symmetry tetragonal space group P4/nnc
with the empirical formula simplified (within estimated standard
deviations) to Agꢁ11.5Brꢁ11.5(PBn23 16
)
ꢀꢁ5.5H2O and chemical enti-
2ꢂ
disordered triangular AgBr3 moieties (lying on the body diagonal
ties distributed as 0.375/0.50 Ag+ in the Ag(PBnz3)2 site of –1 sym-
of the Ag cuboid, and then disordered by crystallographic 222 sym-
metry). At this stage it was becoming increasingly apparent that
one of the other sites of 222 symmetry was only partially occupied
by Brꢂ and another was occupied by water, with the remaining 222
site occupied by the apparent cluster. In addition, considerable
negative electron density was concentrated at the Ag+ sites of the
[Ag(PBn3)2]+ moieties, located on inversion centers, indicating that
these Ag+ sites might not be fully occupied. Final refinement as-
signed free variables to the (i) occupancy of Ag+ in the two sites
with –1 point symmetry, (ii) occupancy of the two independent
Ag+ sites in the apparent X8Y6 cluster of point symmetry 222
(the two crystallographically independent Ag+ ions on general
positions assigned occupancy of 0.25 based on electron density),
(iii) occupancy of the three independent Brꢂ sites (located on the
twofold axes) in the apparent X8Y6 cluster, and (iv) occupancy of
Brꢂ on a site of 222 symmetry, with the overall restraint of a net
charge balance of zero for the Ag+ and Brꢂ ions. The prior refine-
ment established that there was equal occupancy of Ag+ in each
pair of Ag+ sites and of Brꢂ in the trio of Brꢂ sites. Thus, overall
the compound is non-stoichiometric. This is summarized in the fol-
lowing expression in which the first term is the charge on the ion,
the second term is the number of independent sites, the third term
is the maximum occupancy of that site and the fourth term is the
refined value of fractional occupancy, with its estimated standard
deviation in parentheses:
metry, 0.34375/1.00 Ag+ in a general position in the AgBr3 cluster
2ꢂ
for which the Brꢂ occupancies are 0.21875/0.25 for the site of four-
fold symmetry and 0.46875/0.50 for the site with twofold [0 1 0]
symmetry (numbers after the slash are fractional site multiplici-
ties); stoichiometric balance is achieved by 0.03125/0.125 occu-
pancy by Brꢂ of the isolated H2O site of 422 symmetry. A site of
222 symmetry is fully occupied by another H2O. The final value
for R1 (observed data) is 0.0616, significantly lower than that for
the orthorhombic refinement, and the permutative cubic twin law
(0 1 0/0 0 1/1 0 0) had final refined components of 0.270(5) and
0.260(5) and 0.530.
2.4. Infrared spectroscopy
Far-infrared spectra were recorded at 4 cmꢂ1 resolution on
samples suspended in polythene disks using a Nicolet 8700 FT-IR
spectrometer or a Perkin Elmer Spectrum 400 FT-IR spectrometer.
2.5. NMR spectroscopy
The 31P cross-polarization, magic-angle-spinning (CPMAS) NMR
spectra of compounds 4, 5 and 7 were recorded at 7.0 T on a Varian
Infinity Plus-300 spectrometer operating at
of 121.47 MHz. All spectra were obtained with conventional
a
31P frequency

642
E.W. Ainscough et al. / Polyhedron 30 (2011) 638–646
cross-polarization (CP) methods and a MAS frequency of ꢁ10 kHz
Interestingly, when AgF was refluxed with PBn3 in a 1:1 M ratio
in CHCl3 the complex [Ag(PBn3)2Cl]ꢀ0.33CHCl3 was formed pre-
sumably accordingly to the equation:
using a Bruker 4 mm double-air-bearing probe. The typical pulse
parameters employed were: a 1H
p/2 pulse time of 3.5 ls, a
Hartmann-Hahn contact period of 10 ms, a recycle delay of 20 s,
and a 1H decoupling field strength during acquisition of ꢁ80 kHz.
All data were referenced to 85% H3PO4 via an external reference
of (NH4)(H2PO4) (d 1.0 ppm), which was also used to set the
Hartmann–Hahn match condition. The CPMAS NMR spectrum of 1
was recorded at 9.4 T on a Varian INOVA spectrometer operating
at a 31P frequency of 161.92 MHz. Spectra were obtained with con-
ventional CP methods and a MAS frequency of ꢁ5 kHz using a Varian
7 mm CPMAS probe. Two thousand transients were collected using a
AgF þ 2PBn3 þ 2CHCl3 ! ½AgðPBn3Þ2Clꢃ ꢀ CHCl3 þ CHCl2F
The probable halide exchange reaction of CHCl3 with AgF under
mild conditions may have been promoted by the complexation of
AgF with the basic PBn3 which then produces a stronger fluoro
nucleophile. Similarly, it has been reported [18] that a halide ex-
change reaction occurs when 7,7-dichloro-2,5-diphenylbenzocy-
clopropene reacts with excess AgF in MeCN for 24 h at room
temperature. The presence of a coordinating solvent may speed
up what is otherwise a slow reaction.
1H
p/2 pulse time of 8 ls, a Hartmann–Hahn contact period of 4 ms,
an acquisition time of 50 ms and a recycle delay of 15 s. The 1H
decoupling field strength during acquisition was ꢁ60 kHz. Spectra
were zero filled to 4096 data points and a 20 Hz line broadening ap-
plied prior to FT. The 31P chemical shift was referenced to 85% H3PO4
via an external reference of triphenylphosphane (d ꢂ9.9 ppm).
3.2. Crystal structures
Table 2 summarizes the bond lengths and angles for the new
compounds. The cluster [Ag13I13(PBn3)6 ] (1) has an onion-like
structure with overall C3 symmetry (Fig. 1). At the center is an io-
dide ion on a special position with C3 symmetry surrounded trigo-
nal-prismatically by an inner core of six silver ions. These silver
ions are arranged with C3 symmetry and are tetrahedrally coordi-
nated by the innermost iodide ion and by six iodides that bridge
to an outer layer of six silver ions. In this outer layer the silver ions
are also tetrahedrally coordinated by six bridging iodides and
capped by the six PBn3 ligands, together arranged with S6 symme-
try. The top of the onion features a silver ion lying on the unique
threefold axis and capping the cluster with three iodo ligands ar-
ranged in a near-planar trigonal arrangement around this silver
ion. The inner core of silver ions and iodo ligands, which have C3
symmetry, are disordered by the crystallographic center of inver-
3. Results and discussion
3.1. Synthesis
Efforts to prepare complexes of 1:1 stoichiometry from the
reaction of one molar equivalent of AgX (X = Cl, Br or I) with
PBn3 were unsuccessful. Instead, the cluster [Ag13I13(PBn3)6 ] (1)
was isolated when the AgI:PBn3 ratio was ꢁ2:1, but when the ini-
tial molar ratio was 4:1 the complex [Ag(PBn3)2I] (7) crystallized.
The main difference in these two reactions, since unreacted AgI
is removed from both, lies in the concentration of PBn3 which is
higher for the latter reaction. For the chloride, when the ratio of
AgCl:PBn3 was 10:1, a compound of stoichiometry [Ag(PBn3)2]8-
[AgCl3]Cl6 6H2O (2) was isolated but when the ratio was 1:2
[Ag(PBn3)2Cl] (6) resulted. In the above reaction from which 2
was isolated, it appeared that 6 was also crystallizing from the
solution, which meant the yield of a pure product was very low.
For the bromide, tribenzylphosphane oxide, from adventitious oxy-
gen, formed when the AgBr:PBn3 ratio was 1:1, but when the ratio
ꢀ
sion of space group R3.
The crystal structures of 2–5 confirm that the complexes all
contain the linear [Ag(PBn3)2]+ cation (Fig. 2), as has been observed
previously for other d10 species, namely Cu(I) [3], Au(I) [4] and
Hg(II) [19]. Like these complexes, the Ag(I) also resides within a
‘sextuple phenyl embrace’ [20] – an array of intramolecular
p
ꢀ ꢀ ꢀH–C interactions between the benzyl groups on different li-
was 1:2 both the non-stoichiometric species, Agꢁ11.5Brꢁ11.5
-
gands as they encapsulate the metal center.
(PBn3)16ꢀꢁ5.5H2O (3) and phosphane oxide were isolated. Overall,
the variety and complexity of the formulations for these silver(I)
compounds indicates that crystal growth occurs from a solution
containing a mixture of halide and silver ions and the phosphane
For [Ag(PBn3)2]8[AgCl3]Cl6ꢀ6H2O (2) and Agꢁ11.5Brꢁ11.5(PBn3)16ꢀ
ꢁ5.5H2O (3), the trihalo-anion [AgX3]2ꢂ is disordered, unlike the
case for copper(I) where [CuX2]ꢂ (X = Cl or Br) is found in
[Cu(PBn3)2][CuX2] [3]. Both 2 and 3 contain the [Ag(PBn3)2]+ cation
along with halide ions and water in the lattice, but the bromo com-
plex contains also uncoordinated pairs of PBn3 molecules (still
embracing each other in a sixfold phenyl embrace in the absence
ꢂ
ligand. With weakly coordinating anions BF4 and PF6ꢂ, the reac-
tions afforded the compounds [Ag(PBn3)2]X [X = PF6 (4) and BF4
(5)].
2ꢂ
In contrast to these silver complexes, with gold well defined 1:1
and 1:2 compounds of the type [Au(PBn3)X] (X = Cl and Br) and
[Au(PBn3)2]XꢀnH2O (X = Cl, n = 1 or 2; X = I, n = 0), respectively,
were isolated. Unusually with the latter 1:2 complexes, the halide
groups are ionic in contrast to the silver analogs [4].
of an encapsulated silver ion), non-stoichiometric AgBr3 moie-
ties, as well as partially occupied free bromide sites. Although
the PBn3 sites are fully occupied, about a quarter of the encapsu-
2ꢂ
lated silver sites are vacant. The AgBr3 species appear as motifs
2ꢂ
in approximately 25% silver-deficient apparent Ag4Br6 clusters.
Table 2
Selected bond lengths (Å) and angles (°) for the silver-tribenzylphosphane compounds 1–7.a
Compound
Ag–P
Ag–X
P–Ag–P
P–Ag–X
1
2
3
4
5
6
7
2.458(1)
2.377(3)–2.389(3)
2.402(3)
2.3742(4)
2.3762(5)
2.6974(4)–3.0777(5)b
2.620(12)–2.714(13)c
2.599(5)–2.702(7)d
121.89(5)–100.20(3)b
179.3(2), 178.7(2)
180
180
180
142.89(3)
140.00(2)
2.4064(7), 2.4820(8)
2.4228(7), 2.4335(7)
2.5508(8)c
2.8063(3)b
125.81(3), 90.58(3)c
120.26(2), 99.33(2)b
a
b
c
Tables of bond lengths and angles are given in more detail in Supporting Information.
X = I.
X = Cl.
X = Br.
d

E.W. Ainscough et al. / Polyhedron 30 (2011) 638–646
643
Fig. 1. (a) The structure of [Ag13I13(PBn3)6] (1) viewed along the unique threefold,
Ag6A-I4 axis. Ag6A is bound to I2A, I2C and I2E. The inner iodide ion, I4, is bound to
Ag3, Ag3B, Ag3E, Ag5A, Ag5 and Ag5E. Ag, AgA, AgB, AgC, AgD and AgE form the
outer layer of silver ions. (b) A space-filling representation of 1 viewed along the
Ag6A-I4 threefold axis.
The final refinement (see Experimental Section) indicates the
empirical formula can be simplified to Agꢁ11.5Brꢁ11.5(PBn3)16
ꢀ
ꢁ5.5H2O. The complex [Ag(PBn3)2]8[AgCl3]Cl6ꢀ6H2O (2) appears
to be stoichiometric, with two silver ions present in full occupancy
in general positions within two pairs of sixfold phenyl embraces of
the tribenzylphosphane ligands. Within each [Ag(PBn3)2]+ complex
the two P–Ag–P bond angles are slightly but significantly distorted
Fig. 2. The packing arrangement of eight [Ag(PBn3)2]+ cations. (a) In 3 showing the
formation of the anion-containing holes. (b) A similar view of 4. The packing
arrangements for 2 and 5 are also similar.
2ꢂ
from linearity [178.7(2)° and 179.3(2)°]. The AgCl3 moiety is dis-
ordered about a site of 222 symmetry, creating the illusion of an
120.0(2)° and 121.4(3)°; for 3 the six unique Ag–Br bonds in the
highly disordered [Ag4ꢂzBr6] cluster range from 2.599(5) to
2.702(7) Å and the Br–Ag–Br bond angles range from 117.4(2)° to
Ag4Cl2ꢂ cluster; however, the silver ions occupy general sites with
6
partial 25% occupancy. Isolated non-disordered chloride ions and
water molecules complete the crystal structure.
2ꢂ
123.8(2)°. There are only a few structurally characterized AgX3
For 2 the four unique Ag–P distances range from 2.377(3) to
2.389(3) Å; for 3 the Ag–P distance is marginally longer at
2.402(3) Å, possibly indicative of a slightly less close approach of
(X = Cl, Br or I) anions in the literature. For example, discrete
slightly distorted AgI3 ions are found in [PPh3Me](AgI3) [21a],
2ꢂ
but in [Hg7As4](AgI3)2 the anions have an off-plane geometry giv-
2ꢂ
2ꢂ
PBn3 moieties in a silver-free phenyl embrace. For 2, the three AgCl
ing them C3v symmetry [21b]. In contrast AgCl3 and AgBr3 ,
2ꢂ
bonds in the AgCl3
species are 2.620(13), 2.667(13) and
which have been isolated as guests in their (dibenzo-18-crown-
6)potassium and -rubidium salts, have regular D3h symmetry
2.714(13) Å and the Cl–Ag–Cl bond angles are 118.5(2)°,

644
E.W. Ainscough et al. / Polyhedron 30 (2011) 638–646
[21c]. The compound formulated as [Hg6As4](AgCl3)2 contains one-
dimensional anionic chains, not discrete AgCl3 anions [21d].
of the intramolecular ‘sextuple phenyl embrace’, the M–P distances
are slightly shorter for the PBn3 complexes than those observed for
another series of linear, two-coordinate coinage metal compounds,
[M(PMes3)2]BF4 (PMes3 = trimesitylphosphane) with Cu–P, Ag–P
and Au–P Å being 2.242(2), 2.4409(9) and 2.3525(10) Å, respec-
tively [22e].
2ꢂ
In the two-coordinate compounds, 4 and 5, which contain the
ꢂ
ꢂ
non-coordinating anions, PF6 and BF4 (Fig. 3(a)), the Ag(I) atom
lies on a center of symmetry with the P–Ag–P angles necessarily
constrained to 180°. Ag–P lengths observed here are 2.3742(4)
and 2.3762(5) Å compared with 2.205(3) and 2.2977(8) Å in the
analogous CuPF6 and AuBF4 adducts, which like the silver com-
plexes also crystallize in the monoclinic C2/c space group [3,4].
These observations reinforce the view that relativistic effects are
particularly pronounced for gold, making its covalent radius smal-
ler than that of silver regardless of its coordination environment
[22]. It should be noted, presumably because of the attractive effect
Despite the slightly chaotic nature of the speciation in the com-
pounds 2 and 3, the packing motifs present in the four crystal
structures 2–5 are very similar. The six phenyl rings of the ‘em-
brace’ in the Ag(PBn3)2 or ‘(PBn3)2’ pairs are spatially disposed to
approximate as six corners of a cube, with the phosphorus atoms
diagonally opposing and sitting on the two remaining corners
(Fig. 2). In 2 and 3, the cubes pack together face-to-face in a regular
manner such that a hole is left in the array, approximately where
the phosphorus atoms from adjacent molecules are the closest
(Fig. 2(a)). Close contacts between phenyl and benzyl hydrogen
atoms and the aromatic rings of adjacent molecules cement to-
gether these cubic blocks. The spaces that are generated in the lat-
tice near the phosphorus atoms contain the remaining components
of the crystal, where further stabilizing hydrogen bonding interac-
tions can occur between the halogen or oxygen atoms and benzyl
or aromatic hydrogen atoms. Unlike 2 and 3, in 4 and 5 all the
cubes are lined up in the same direction which means that the
(a)
(b)
600
500
400
300
200
100
Wavenumber/cm -1
Fig. 3. (a) The linear [Ag(PBn3)2]+ cation in the crystal structure of 4. The structure
of the cation in 5 is almost identical. (b) The structure of [Ag(PBn3)2Cl] in 6. (c) The
structure of [Ag(PBn3)2I] (7).
Fig. 4. Far-IR spectra of (a) [Ag(PBn3)2I] (7); (b) [Ag13I13(PBn3)6] (1). Bands assigned
as (AgI) are labeled with their wave numbers.
m

E.W. Ainscough et al. / Polyhedron 30 (2011) 638–646
645
holes that are generated have only half of the cubes with P–Ag–P
axes orientated towards the hole (Fig. 2(b)). The PF6 counter-ions
consistent with the monomer structure, the
m
(Ag–I) frequency
being slightly less than the value 121 cmꢂ1 found for [Ag(PCy3)2I]
(PCy3 = tricyclohexylphosphane) [23]. This is in keeping with the
Ag–I bond being longer (2.806 vs. 2.778 Å) and the P–Ag bonds
being shorter (2.423 and 2.433 vs. 2.478 Å) in the PBn3 complex.
ꢂ
have a well-defined orientation in the holes that involve C–Hꢀ ꢀ ꢀF
hydrogen bonding with three of the six fluorine atoms per anion,
ꢂ
although some disorder exists in the BF4 species. However, in 2
and 3 the holes are much larger, in order to accommodate the dis-
ordered orientations of the AgX3 anions or the remaining halide
ions and water molecules.
The [Ag(PBn3)2X] (X = Cl and I) complexes, 6 and 7 (Fig. 3(b) and
(c)) contain three-coordinate Ag(I) centers with ‘P2X’ donor sets,
which are best described as distorted T-shaped. The Ag–P bonds
The m(Ag–I) range for 1 is similar to that found for [{Ag(PCy3)I}4]
2ꢂ
[24] but the band structure is more complex due to the lower sym-
metry and more complex structure of the former compound.
The 31P CP MAS NMR spectra for 4 and 5 are shown in Fig. 5. The
naturally occurring isotopes of silver
(
107Ag, 51.82% natural
abundance; 109Ag, 48.18%) both have nuclear spin I = ½, and their
magnetogyric ratios are similar in magnitude. The 31P NMR spectra
of complexes of silver(I) with phosphorus-donor ligands normally
show splitting due to 1J(P–Ag) coupling but in the solid state sep-
arate splitting due to the 107Ag and 109Ag nuclei, which is usually
observed in solution, is not normally resolved due to the greater
are 2.4064(7) and 2.4820(8) Å for
6 and 2.4228(7) and
2.4335(7) Å for 7, whereas the bond Ag–Cl is 2.5508(8) Å and
Ag–I 2.8063(3) Å. The angles around the coordination plane in both
complexes are quite varied, ranging between 90.58(3)° and
142.89(3)° in the chloro complex and 99.33(2)° and 140.00(2)° in
the iodo complex.
line widths (
D
m
ꢁ 40 Hz) that occur under these conditions. The
In both complexes a similar conformational change in one of the
PBn3 ligands (in comparison with [Ag(PBn3)2]+) allows coordina-
tion of the halide ligand. One ligand of the pair retains approximate
C3 symmetry whereas in the other ligand, rotation about the P–CH2
bond pins back one of the phenyl rings to make room for the three-
coordinate geometry. A partial ‘embrace’ of intramolecular close
contacts is maintained by the other phenyl rings. In 6, a weak
hydrogen bond is formed between the hydrogen atom of the
disordered chloroform solvate and the chloride ligand. Similar
conformations and coordination geometries have been observed
in the [Cu(PBn3)2X] (X = Cl, Br and I) complexes [3b].
spectrum of the coordinated phosphane thus consists of a doublet
with a weighted average 31P–107,109Ag splitting 1J(31P–Ag) [23,24].
The solid-state 31P CP MAS NMR spectrum for the iodo-cluster 1
shows a doublet at ꢂ4.9 ppm with 1J(31P–Ag) = 525 Hz, these
parameters being similar to those observed for [{Ag(PCy3)I}4]
[24] which also contains a ‘AgPI3’ coordination sphere. The obser-
vation of a single doublet is consistent with the crystallographic
equivalence of the six phosphane ligands in the complex (see
above). The spectra of [Ag(PBn3)2]PF6 (4) and [Ag(PBn3)2]BF4 (5)
show doublets for the PBn3 phosphorus atoms at 42.0 and
44.9 ppm with 1J(31P–Ag) = 535 and 522 Hz, respectively (Fig. 5).
ꢂ
The spectrum of 4 also shows a signal due to the PF6 counterion
at ꢂ142.5 ppm with 1J(31P–Ag) = 717 Hz. The 1J(31P–Ag) for the
coordinated PBn3 are similar to those in the related complexes
[Ag(tmpp)2]ClO4 (tmpp = tris(2,4,6-trimethoxyphenylphosphane;
622 Hz) [25], and [Ag(PCy3)2)]ClO4 (ca. 500 Hz) [23]. The observa-
tion of single doublets for the phosphane P atoms in 4 and 5 is con-
sistent with their centrosymmetric structures.
3.3. Spectroscopic measurements
The far-IR spectrum of [Ag(PBn3)2I] (7) shows a single
m(Ag–I)
(PBn3)6 ] (1) dis-
band at 111 cmꢂ1, whereas the cluster [Ag13 13
I
plays a complex set of partially resolved bands from about 120
to 70 cmꢂ1 (Fig. 4). The single band for the former complex is
(a)
*
*
(b)
*
*
200
100
0
-100
-200
δ/ppm
Fig. 5. 31P CP MAS NMR spectra at B = 7.0 T of (a) [Ag(PBn3)2]PF6 (4); (b) [Ag(PBn3)2]BF4 (5). Peaks marked ⁄ are spinning sidebands.

646
E.W. Ainscough et al. / Polyhedron 30 (2011) 638–646
[3] (a) P.D. Akrivos, P.P. Karagiannidis, C.P. Raptopoulou, A. Terzis, S. Stoyanov,
4. Conclusions
Inorg. Chem. 35 (1996) 4082;
(b) E.W. Ainscough, A.M. Brodie, A.K. Burrell, G.H. Freeman, G.B. Jameson, G.A.
Bowmaker, A.M. Brodie, J.V. Hanna, P.C. Healy, J. Chem. Soc., Dalton Trans.
(2001) 144.
The chemistry of the silver(I)–tribenzylphosphane system is
considerably more varied than that observed for the copper(I) or
gold(I) analogs, resulting in the formation of the unique iodo clus-
ter, [Ag13I13(PBn3)6] (1), and the identification of the unusual
chloro and bromo derivatives, [Ag(PBn3)2]8[AgCl3]Cl6ꢀ6H2O (2),
and Agꢁ11.5Brꢁ11.5(PBn3)16ꢀꢁ5.5H2O (3) in the presence of coordi-
nating anions. The formation of [Ag(PBn3)2]+ in 2 and 3, and also
[4] E.W. Ainscough, G.A. Bowmaker, A.M. Brodie, G.H. Freeman, J.V. Hanna, P.C.
Healy, W.T. Robinson, B.W. Skelton, M.E. Smith, A.N. Sobolev, A.H. White, Eur. J.
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(b) J.F. Corrigan, D. Fenske, Chem. Commun. (1996) 943;
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60.
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ꢂ
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We thank the Massey University Research Fund for support, Dr.
A.K. Burrell for preliminary crystallographic assistance, and Dr. S.E.
Boyd (Griffith University) for running the 31P CPMAS NMR spec-
trum on compound 1. J.V.H. thanks the following for funding of
the solid state NMR infrastructure at Warwick: EPSRC, the Univer-
sity of Warwick, Birmingham Science City Advanced Materials Pro-
ject 2 supported by Advantage West Midlands and the European
Regional Development Fund.
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CCDC 787379, 787380, 787381, 787382, 787383, 787384 and
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paper. These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ,
UK; fax: (+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
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