Synthesis of (phosphine)silver(I) trifluoromethanesulfonate complexes and the molecular structure of di-μ-trifluoromethylsulfonate-(tetrakis-triphenylphosphine)disilver(I)

Article abstract of DOI:10.1016/S0020-1693(00)00196-1

Reactions of silver trifluoromethanesulfonate (triflate) and equimolar amounts of triphenylphosphine, 1,2-bis(diphenylphosphino)ethane, bis(diphenylphosphino)methane, or 1,1-bis(diphenylphosphino)ethane in either DME or CH₂Cl₂ solution produced the corresponding 1:1 complexes [(L)Ag(I)(SO₃CF₃)] (2-5) in > 80% yields. A related 2:1 complex [(Ph₃P)₂Ag(I)(SO₃CF₃)] (1) was also obtained using 2 equiv. of Ph₃Ph. Both ³¹P NMR variable temperature solution spectra as well as solid state spectra were recorded for the new complexes, and were generally helpful in structural assignments. An X-ray crystallographic study of 1 shows this to be a dimeric complex with bridging triflate ions; the silver atoms having distorted tetrahedral coordination. (C) 2000 Elsevier Science S.A.

Full text of DOI:10.1016/S0020-1693(00)00196-1

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Inorganica Chimica Acta 308 (2000) 37–44
Synthesis of (phosphine)silver(I) trifluoromethanesulfonate
complexes and the molecular structure of
di-m-trifluoromethylsulfonate-(tetrakis-triphenylphosphine)disilver(I)
Linda Lettko, John S. Wood *1, Marvin D. Rausch *2
Department of Chemistry, Uni6ersity of Massachusetts, Amherst MA 01003, USA
Received 5 August 1999; accepted 14 June 2000
Abstract
Reactions of silver trifluoromethanesulfonate (triflate) and equimolar amounts of triphenylphosphine, 1,2-bis(diphenylphos-
phino)ethane, bis(diphenylphosphino)methane, or 1,1-bis(diphenylphosphino)ethane in either DME or CH2Cl2 solution produced
the corresponding 1:1 complexes [(L)Ag(I)(SO3CF3)] (2–5) in \80% yields. A related 2:1 complex [(Ph3P)2Ag(I)(SO3CF3)] (1) was
also obtained using 2 equiv. of Ph3Ph. Both 31P NMR variable temperature solution spectra as well as solid state spectra were
recorded for the new complexes, and were generally helpful in structural assignments. An X-ray crystallographic study of 1 shows
this to be a dimeric complex with bridging triflate ions; the silver atoms having distorted tetrahedral coordination. © 2000 Elsevier
Science S.A. All rights reserved.
Keywords: Crystal structures; Silver complexes; Phosphine complexes; Triflate complexes
1. Introduction
2. Experimental
Recent studies in our laboratory have been con-
cerned with the formation and structure of thermally
stable organosilver compounds of the type (h-
C5H4R)Ag(L), where L=a triorganophosphine and
R=an electron-withdrawing substituent [1]. (Phos-
phine)–silver(I) trifluoromethanesulfonate complexes
were found to be highly useful intermediates in the
formation of these organosilver derivatives. In this pa-
per, we describe the synthesis of a series of new com-
plexes of the type [(L)Ag(I)(SO3CF3)], where
L=mono- or bidentate phosphine ligands, together
with an X-ray structural investigation of the related
complex [(Ph3P)2Ag(I)(SO3CF3)] (1).
2.1. Materials and general procedures
All operations were carried out under an argon at-
mosphere using standard Schlenk, vacuum or glovebox
techniques. The argon was dried with H2SO4, P2O5, and
molecular sieves, and trace oxygen was removed with
activated BTS catalyst. Dimethoxyethane (DME) was
predried over sodium wire, and both dimethoxyethane
and pentane were distilled under argon from
Na/K alloy. Dichloromethane (CH2Cl2) was dried
and distilled under argon from CaH2. Silver(I)
trifluoromethanesulfonate, triphenylphosphine, bis-
(diphenylphosphino)methane,
1,2-bis(diphenylphos-
phino)ethane and 1,1-bis(diphenylphosphino)ethane
were purchased from Aldrich Chemical Co.
Proton (1H) NMR spectra were obtained on Bruker
AC-80 or 200 MHz spectrometers, or on Varian XL-
200 or XL-300 spectrometers, and were referenced to
tetramethylsilane as an internal standard. Solution
phosphorus (31P) NMR spectra were obtained on either
Bruker AC-80, Varian XL-200 or MSL-300 spectrome-
1 *Corresponding author. Tel.: +1-413-545 2291; fax: +1-413-545
4490; e-mail: jonwood@chem.umass.edu.
2 *Corresponding author.
0020-1693/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(00)00196-1

38
L. Lettko et al. / Inorganica Chimica Acta 308 (2000) 37–44
ters and are referenced to 85% H3PO4 in D2O as an
external standard. Solid state 31P NMR spectra were
obtained on an IBM 200 MHz spectrometer and are
referenced to CaHPO4. Melting points were obtained
on a Mel-Temp apparatus from Laboratory Devices,
Inc., and are uncorrected. Microanalyses were per-
formed by the Microanalytical Laboratory, University
of Massachusetts, Amherst, MA.
and 0.49 g (1.9 mmol) of silver(I) trifluoromethanesul-
fonate. DME (ca. 50 ml) was added to the mixture, and
after 30 min of stirring, a white solid precipitated from
solution. After filtration, the solid was taken up in ca.
25 ml of CH2Cl2 and pentane was then added until the
solution turned slightly cloudy. The solution was cooled
to −20°C to give 1.1 g (88%) of [1,2-bis(diphenylphos-
phino)ethane]silver(I) trifluoromethanesulfonate as
small white air-stable crystals, m.p 259–261°C. 1H
NMR (CDCl3): l 2.64 (4 H, br s, CH2CH2), 7.21–7.94
(20 H, m, C6H5). 31P NMR (75% CH2Cl2, 25% CDCl3,
2.2. Preparation of mono(triphenylphosphine)sil6er(I)
trifluoromethanesulfonate (2)
1
1
25°C): l 6.28 (dd, J(109Ag–P)=569, J (107Ag–P)=
1
In a 100 ml round-bottom Schlenk flask were placed
silver(I) trifluoromethanesulfonate (1.0 g, 3.9 mmol)
and triphenylphosphine (1.0 g, 3.9 mmol). Ca. 40 ml of
CH2Cl2 was added to the combined solids and the
reaction was allowed to stir at 25°C for 12 h. The clear
solution was concentrated to half of its original volume
under reduced pressure and then ca. 15 ml of pentane
was added. The solution was cooled to −20°C to yield
1.8 g (89%) of mono(triphenylphosphine)silver(I) tri-
fluoromethanesulfonate as a white, crystalline air-stable
505 Hz). Solid state 31P NMR: l 9.15 (d, J(Ag–P)=
519 Hz). Anal. Calc. for 3, C27H24AgF3O3P2S: C, 49.48;
H, 3.69; Ag, 16.46. Found: C, 49.24; H, 3.69; Ag,
16.43%.
2.5. Preparation of [bis(diphenylphosphino)-
methane]sil6er(I) trifluoromethanesulfonate (4)
In a manner similar to the synthesis of 2, bis-
(diphenylphosphino)methane (1.0 g, 2.6 mmol), silver(I)
trifluoromethanesulfonate (0.67 g, 2.6 mmol) and ca. 40
ml of CH2Cl2 were combined in a 100 ml round-bottom
Schlenk flask, and the reaction allowed to stir at 25°C
for 12 h. Concentration of the clear solution under
reduced pressure, addition of ca. 15 ml of pentane and
cooling to −20°C produced 1.4 g (84%) of [bis-
(diphenylphosphino)methane]silver(I) trifluoromethane-
sulfonate as a white crystalline solid. The compound
was air-stable and had an m.p. of 265–267°C. 1H
1
solid, m.p. 148–149°C. H NMR (CDCl3): l 7.35–7.62
(m, C6H5). 31P NMR (75% CH2Cl2, 25% CDCl3,
1
−73°C): l 15.23 (d, J(Ag–P)=774 Hz). Solid state
1
31P NMR: l 12.14 (d, J(Ag–P)=793 Hz). Anal. Calc.
for 2 C19H15AgF3O3PS: C, 43.95; H, 2.91; Ag, 20.78.
Found: C, 43.73; H, 2.86; Ag, 20.92%.
2.3. Preparation of bis(triphenylphosphine)sil6er(I)
trifluoromethanesulfonate (1)
2
NMR (CDCl3): l 3.95 (4 H, m, CH2, J(1H–31P)=5
Silver(I) trifluoromethanesulfonate (0.51 g, 2.0 mmol)
and triphenylphosphine (1.05 g, 4.0 mmol) were added
to a 100 ml round bottom Schlenk flask. The flask was
cooled to −10°C and ca. 50 ml of DME was added. A
white solid immediately precipitated from solution, but
the reaction was allowed to stir for 2 h with gradual
warming to 25°C. The reaction mixture was filtered and
the white solid was extracted with ca. 20 ml of CH2Cl2.
A small amount of pentane was added to the clear
solution and it was cooled to −20°C, producing 1.2 g
(77%) of bis(triphenylphosphine)silver(I) trifluoro-
methanesulfonate as small white air-stable crystals,
Hz), 7.22–7.62 (40 H, m, C6H5). 31P NMR (75%
CH2Cl2, 25% CDCl3, 25°C): l 6.86 (m). Solid state 31P
NMR: l 1.21 (m). Anal. Calc. for 4, C26H22AgF3O3P2S:
C, 48.69; H, 3.46; Ag, 16.82. Found: C, 48.59; H, 3.52;
Ag, 16.61%.
2.6. Preparation of [1,1-bis(diphenylphosphino)-
ethane]sil6er(I) trifluoromethanesulfonate (5)
In a manner similar to the synthesis of 2, 1,1-bis-
(diphenylphosphino)ethane (0.38 g, 0.95 mmol), sil-
ver(I) trifluoromethanesulfonate (0.25 g, 0.95 mmol)
and ca. 30 ml of CH2Cl2 were combined in a 100 ml
round-bottom Schlenk flask, and the reaction was al-
lowed to stir at 25°C for 3 h. After filtration through
Celite, pentane was added until the clear solution
turned slightly cloudy. The solution was cooled to
−20°C to yield 0.56 g (88%) of [1,1-bis(diphenylphos-
phino)ethane]silver(I) trifluoromethanesulfonate as a
1
m.p. 212–214°C. H NMR (CDCl3): l 7.20–7.63 (m,
C6H5). 31P NMR (75% CH2Cl2, 25% CDCl3, −73°C):
l 11.64 (dd, 1J(107Ag–P)=487, 1J(109Ag–P)=562 Hz).
1
Solid state 31P NMR: l 10.05 (d, J(Ag–P)=484 Hz).
Anal. Calc. for 1 C37H30AgF3O3P2S: C, 56.86; H, 3.87;
Ag, 13.80. Found: C, 56.68; H, 4.00; Ag, 13.76%.
1
2.4. Preparation of [1,2-bis(diphenylphosphino)-
ethane]sil6er(I) trifluoromethanesulfonate (3)
white crystalline air-stable solid, m.p. 287–293°C. H
NMR (CDCl3): l 1.55 (3 H, m, CH3), 4.84 (1 H, m,
CH), 7.22–7.82 (20 H, m, C6H5). 31P NMR
(75% CH2Cl2, 25% CDCl3, 25°C): l 25.77 (m). Solid-
state 31P NMR: l 20.81 (m). Anal. Calc. for 5,
In a 100 ml round-bottom Schlenk flask were placed
0.75 g (1.9 mmol) of 1,2-bis(diphenylphosphino)ethane

L. Lettko et al. / Inorganica Chimica Acta 308 (2000) 37–44
39
C27H24AgF3O3P2S: C, 49.48; H, 3.69; Ag, 16.46. Found:
C, 49.36; H, 3.76; Ag, 16.30%.
‘triflate’ ions were found to be coordinated to the silver
ions and to act as bridging ligands to centrosymmetri-
cally related silver atoms. In addition, the ions are
statistically disordered in two orientations, such that
one half ‘triflate’ is related to its partner by a non-crys-
tallographic mirror plane passing through the two coor-
dinated oxygen atoms and their two trans-related
fluorine atoms of the –CF3 groups. In contrast to some
other situations, where the CF3SO3− ion is often crys-
tallographically disordered [2], the disorder in this in-
stance was relatively well-defined and fairly readily
modeled. Thus, the sulfur and carbon atoms together
with the uncoordinated oxygen and its trans-related
fluorine atom of each of the two mirror related ions
were given population parameters of 0.5 on the basis of
the near equality of their thermal parameters. These
populations were not varied in the subsequent
refinement.
2.7. Crystallographic data collection and refinement of
the structure
Tan-colored crystals of [(Ph3P)2Ag(I)(SO3CF3)] (1)
suitable for X-ray analysis were obtained by recrystal-
lization from solutions of the complex in a CH2Cl2–
pentane mixture. Diffraction data were obtained on an
Enraf-Nonius CAD-4 diffractometer at room tempera-
ture using graphite monochromated Mo Ka radiation.
Unit cell dimensions were obtained from 25 accurately
centered reflections in the range 24B2qB30°. The
reflection intensities were monitored with four standard
reflections and there was no significant variation in
their intensity over the data collection period. An em-
pirical absorption correction based on c scans was
applied to the data. Details of cell parameters and
refinement results are given in Table 1.
The structure was refined by full-matrix least squares
on F2 using all 4183 independent reflections, with an-
isotropic thermal parameters assigned to silver, the
atoms of the two phosphine ligands and the two coordi-
nated oxygen atoms. The phenyl group hydrogen atoms
were included based on a riding model with CꢀH=0.95
The positions of the silver atom and the two
triphenylphosphine groups were determined by direct
methods and the positions of the atoms of the trifl-
uoromethylsulfonate ion were then located from subse-
quent successive difference Fourier syntheses. The
,
A. Atomic scattering factors for all non-hydrogen
atoms were taken from International Tables [3], while
that given by Stewart et al. was used for hydrogen [4].
Corrections for anomalous dispersion were included in
the calculations [5]. All crystallographic calculations
were carried out using the SHELXS-86 and SHELXL-93
program packages [6,7].
Table 1
Crystal data and structure refinement results for {Ag[P(C6H5)3]2-
(CF3SO3)}2
Empirical formula
Formula weight
Temperature (K)
Ag2P4S2C74H60O6F6
1563.0
293(2)
,
Wavelength (A)
0.71073 (Mo Ka)
triclinic
Crystal system
Space group
3. Results and discussion
(
P1 (no. 2)
Unit cell dimensions
3.1. Synthesis and characterization of
(phosphine)sil6er(I) trifluoromethane sulfonate
complexes
,
a (A)
12.368(5)
12.707(7)
13.309(3)
71.93(3)
62.57(3)
70.59(4)
1719.9(12)
1.509
,
b (A)
,
c (A)
h (°)
i (°)
The synthesis of the (phosphine)silver(I) trifluoro-
methanesulfonate (triflate) complexes could be accom-
plished using either of two different reaction conditions.
By reaction of equimolar (1:1) mixtures of silver triflate
and a triorganophosphine at room temperature in
DME as the solvent, the desired 1:1 complexes could
readily be obtained. Both reagents were soluble in
DME, but upon mixing, a white precipitate appeared
within minutes. After the reaction mixture was stirred
30 min to 2 h to insure completion, the solution was
filtered in an inert atmosphere. The white solid was
taken up in a minimum amount of CH2Cl2, pentane
was added, and the solution was cooled to −20°C
to produce the desired complexes (2–5) in \80%
yields:
k (°)
3
,
V (A )
Dcalc (g cm−3
)
Z
1
7.92
Absorption coefficient (cm−1
Absorption correction
Crystal size (mm)
Relative transmission factors
Data collection
)
Based on c scans
0.3×0.45×0.50 mm
0.74–1.00
ꢀ/2q
3.0–45.0
4183
2q Range (°)
Independent reflections
Parameters
410
R1 a, wR2 [I]2|(I)]
0.050, 0.130
0.066, 0.145
1.108
b
R1 a, wR2 (all data)
b
Goodness-of-fit
a R1=SꢀꢀFoꢀ−ꢀFcꢀꢀ/SꢀFoꢀ.
b wR2={S[w(Fo2−Fc2)2]/S[w(F2o)2]}1/2
.

40
L. Lettko et al. / Inorganica Chimica Acta 308 (2000) 37–44
AgSO3CF3+LꢀDꢀMꢀꢀEꢀꢀorꢁ (L)AgSO3CF3
magnitude of 793 Hz centered at 12.14 ppm. The
coupling and chemical shift values were close but not
the same as the solution values, since solid state spectra
have increased line widths due to dipolar coupling
which are not averaged by molecular tumbling [11].
Coupling in these complexes is due to spin–spin cou-
pling between 31P and the 109Ag and 107Ag isotopes.
Individual resolution of phosphine–silver isotope cou-
pling is not apparent in the 31P NMR spectra of 2, and
an averaged doublet is therefore observed.
CH Cl
2
2
(2) L=Ph3P
(3) L=Ph2PCH2CH2PPh2
(4) L=Ph2PCH2PPh2
(5) L=(Ph2P)2CHCH3
An alternate synthetic procedure utilized CH2Cl2 as
the solvent. By an analogous method, the reaction was
allowed to stir for 3–12 h to form a clear solution.
Concentration of the solution, addition of a small
amount of pentane or hexane, and subsequent crystal-
lization at −20°C afforded 2–5 in comparable yields.
In addition to the 1:1 ratio of phosphine to silver
complexes, a 2:1 derivative was also prepared in the
case of Ph3P. In a manner similar to the above proce-
dures, the 2:1 complex (1) was prepared in 77% yield:
In the case of the 2:1 complex 1, two doublets were
observed in the 31P NMR solution spectrum at −73°C.
The two doublets were due to the 31P resonance being
split by each Ag isotope. The magnitude of the cou-
pling was 1J(109Ag–P)=562 and 1J(107Ag–P)=487
Hz, and the pattern was centered at 11.64 ppm. The
ratio of these two couplings should be equal to their
magnetogyric ratios [11]. For J(109Ag–31P)/J(107Ag–
31P), this ratio is 1.15. Experimental results match with
theory in this case, since the ratio of 562/487=1.15. In
the 31P solid-state spectrum of 1, one doublet was
DME or
AgSO3CF3+2Ph3Pꢀꢀꢀꢀꢀꢀꢀꢁ (Ph3P)2AgSO3CF3
CH Cl
2
1
2
All of the complexes 1–5 were air-stable in solution
as well as in the solid state. Exposure of 1–5 to light
over several days caused the white complexes to turn
yellow, indicating a sensitivity to light. The complexes
were very soluble in halogenated solvents such as
CH2Cl2 and CHCl3, and were moderately soluble in
more polar solvents such as tetrahydrofuran and
toluene.
1
observed at 10.05 ppm with J(Ag–P)=484 Hz. In the
solid state, it is often not possible to observe individual
resolved 109Ag–31P and 107Ag–31P scalar couplings,
since the line widths are so broad.
For complex 3, the spin–spin splitting due to cou-
pling of phosphorus to the individual silver isotopes
was observable even at room temperature in the solu-
tion spectrum. This result might be anticipated for a
chelating ligand such as 1,2-(diphenylphosphino)ethane
and in turn suggests that this ligand chelates to a single
metal center [12]. The pattern in the 31P NMR solution
spectrum of 3 was centered at 6.28 ppm, with 1J(109Ag–
3.2. 31P NMR spectral analysis
The (phosphine)silver(I) triflate complexes synthe-
sized in this study have also been characterized by 31P
NMR techniques, including variable temperature solu-
tion NMR and solid-state NMR. 31P NMR is a valu-
able tool in this regard, since silver has two
NMR-active isotopes. 107Ag and 109Ag are both spin
1/2 nuclei with high natural abundances of 52% and
48%, respectively. Ag–P coupling often is very broad in
phosphine–silver complexes at ambient temperatures in
solution due to rapid ligand exchange on the NMR
time scale. However, Ag–P coupling can be observed in
the solid state and at low temperatures in solution
[8–10]. For chelated phosphine ligands, resolution of
this coupling can often be observed at temperatures
approaching room temperature. There have been a
number of reports concerning Ag–P coupling in solu-
tion, but little information is currently available on
solid state studies of this unique interaction.
1
P)=569 and J(107Ag–P)=505 Hz. This ratio of 1.13
is approximately equal to the theoretical value. In the
solid-state 31P NMR spectrum of 3, one doublet was
1
observed at 9.15 ppm with J(Ag–P)=519 Hz.
The 31P NMR solution spectral patterns for 4 and 5
at 25°C were considerably more complicated than pat-
terns for 1–3 discussed above. This is no doubt due to
additional phosphorus–silver couplings, and suggest
that 4 and 5 are dimeric or tetrameric in solution. The
solid-state 31P NMR spectra for both 4 and 5 likewise
appeared as broad multiplets.
3.3. Crystallographic study of [(Ph3P)2Ag(I)(SO3CF3)]
(1)
Fig. 1 gives an ORTEP plot of the structure of the
complex [(Ph3P)2Ag2 (SO3CF3)2], together with the
atom labeling for the asymmetric unit, while Table 2
lists the bond distance and angle data for the coordina-
tion geometry about the silver atom. Fig. 2 gives two
views of the central portion of the molecule and as may
be seen, two triflate anions act as bridging ligands,
linking two bis-triphenylphosphine silver units to form
For complexes 1 and 2, both variable temperature
solution and solid state 31P studies were conducted. In
the case of 2, the 31P NMR solution spectrum at 25°C
consisted of a broad singlet, but at −73°C appeared as
1
a doublet with a J(Ag–P) coupling of 774 Hz centered
at 15.23 ppm. The solid-state 31P NMR spectrum also
1
occurred as a doublet due to J(Ag–P) coupling with a

L. Lettko et al. / Inorganica Chimica Acta 308 (2000) 37–44
41
Fig. 1. Perspective drawing of the structure of {[(C6H5)3P]2Ag(CF3SO3)}2 (1), giving the atomic labeling scheme. Atoms are represented by thermal
ellipsoids at the 50% probability level.
a centrosymmetric dimer of which this central portion
forms a quasi-planar eight-membered ring. Fig. 2(B)
illustrates the relative conformations of the two ‘half’
disordered triflate anions. Although these anions might
be termed bidentate, the bridging is quite asymmetric,
symmetrically bonded bridging ligand between neigh-
boring silver ions, so that the structure is based on
polymeric AgꢀNO3ꢀAg chains. In this complex the
trigonal plane is formed by the silver and phosphorus
atoms and the two shorter silverꢀoxygen bridge bonds,
the sum of the in-plane angles being 359.8°. The sil-
,
the two silverꢀoxygen distances differing by 0.2 A with
,
the angles around the oxygens also differing signifi-
cantly. Likewise, although the geometry around the
silver atom may be thought of as being approximately
tetrahedral, the angular deviations from a tetrahedral
geometry, together with the differing silverꢀoxygen dis-
tances are rather large. The silver atom is, in fact, fairly
close to being coplanar with the two phosphorus atoms
and oxygen atom O(1); the sum of the three angles,
being 353.4°, so that the geometry is better described as
being trigonal pyramidal.
verꢀphosphorus distances, averaging 2.430(2) A are
marginally longer than the distances of 2.340(4) to
,
2.370(5) A found in the 1:1 phosphine adducts that
have been characterized [13–15]. However, together
with the angle P(1)ꢀAgꢀP(2), they are very comparable
to the AgꢀP distances found in the stoichiometrically
equivalent trimethylphosphite complex, {[P(OMe)3]4-
Ag2(NO3)2}, [16], in which the nitrate ions form sym-
metrical bridges to the silver atoms, each through a
single oxygen atom.
A rather similar ‘3+1’ distorted trigonal pyramidal
geometry is found for the silver atom in the 1:1 com-
plex of silver nitrate with triphenylphosphine [13],
where the nitrate ion acts both as an asymmetrically
bonded bidentate ligand to one silver and as an almost
The geometries of the two ‘half’ triflate ligands are as
expected, apart from the angles involving the coordi-
nated
oxygen
atoms,
O(1)ꢀS(1)ꢀO(2)
and
O(1)ꢀS(1)%ꢀO(2), which at 120.1(5) and 123.1(5)°, re-
spectively, are much larger than expected and signifi-

42
L. Lettko et al. / Inorganica Chimica Acta 308 (2000) 37–44
Table 2
supports this conclusion. Because of large least squares
correlation effects it was not possible to refine the
positions of two separate sites for each oxygen atom.
Although this disorder possibility introduces addi-
tional uncertainty into the observed AgꢀO distances,
Selected bond distances and angles for [Ag(CF3SO3)(P(C6H5)3)2]2
AgꢀP(1)
AgꢀP(2)
2.429(2)
2.431(2)
2.387(6)
2.584(5)
1.383(7)
1.389(7)
1.369(7)
1.363(7)
AgꢀO(1)
AgꢀO(2)
S(1)ꢀO(1)
S(1)ꢀO(2)
S(1)%ꢀO(1)
S(1)%ꢀO(2)
,
the short bond at 2.387(6) A falls in the range of values
,
of 2.35–2.46 A, [13,14,16], which are normally ob-
,
served, while the longer bond at 2.584(5) A is nearly
identical with that observed for a unidentate triflate ion
ligand in the polymeric complex [Ag2(triflate)2-
(NCC6H4CN)2(H2O)]n, [17].
P(1)ꢀAgꢀP(2)
O(1)ꢀAgꢀO(2)
P(1)ꢀAgꢀO(1)
P(1)ꢀAgꢀO(2)
P(2)ꢀAgꢀO(1)
P(2)ꢀAgꢀO(2)
AgꢀO(1)ꢀS(1)
AgꢀO(2)ꢀS(1)
AgꢀO(1)ꢀS(1)%
AgꢀO(2)ꢀS(1)%
O(1)ꢀS(1)ꢀO(2)
O(1)ꢀS(1)%ꢀO(2)
130.4(1)
92.8(2)
115.9(2)
104.6(2)
106.1(2)
98.2(2)
136.1(4)
151.9(5)
138.1(4)
179.3(5)
120.1(5)
123.1(5)
For the 1:1 complex with triphenylphosphine, i.e. 2,
we also propose
a dimeric structure, [Ph3PꢀAgꢀ
(CF3SO3)ꢀAgꢀPPh3] with double triflate bridges, and in
which the silver atoms are three coordinate, or distorted
four coordinate, if the triflate ion ligand adopt both a
bidentate chelating and a bridging role similar to that
found for the nitrate analogue noted above [13].
A few other silver, [18,19] and mixed silver–platinum
complexes [20,21], containing triflate ion ligands have
been structurally characterized and apart from the one
noted above, the ion generally acts as a m-2 or m-3
bridging ligand. For example, in the complex, [Ag(1,4-
thioxane)2(CF3SO3)], [18], the triflate ion bridges neigh-
cantly larger than the remaining four OꢀSꢀO angles.
However as noted earlier, the refinement model treated
the two half anions as sharing atoms O(1) and O(2), so
that it is quite possible that the refined positions for
these two atoms are the average for two unresolved
sites having a rather small positional separation. The
rather large U-tensor values obtained for these atoms
,
boring silver atoms, (AgꢀO; 2.59(1) and 2.47(1) A),
while in the complex ion [Ag6(triphos)4(CF3SO3)4]2+
,
where ‘triphos’ is a tridentate tripodal phosphine lig-
and, the triflate ions adopts a m-3 bridging mode, sitting
above alternate faces of the Ag6 octahedron [19].
Fig. 2. (A) Perspective view showing the coordination polyhedron of the silver atoms and the conformation of the eight-membered ring in 1. (B)
View of the central portion of the structure of 1, showing the two alternative orientations adopted by the disordered triflate ions.

L. Lettko et al. / Inorganica Chimica Acta 308 (2000) 37–44
43
In contrast to the situation for unidentate phosphi-
nes, a rather larger number of structures of silver
complexes containing bidentate phosphines have been
determined, and in the case where the phosphine ligand
chelates the silver atom, dimeric complexes of the type
[diphosꢀAgꢀX2ꢀAgꢀdiphos] in which the two anions, X
act as bridging ligands, between the silver phosphine
units, are invariably formed [22–25]. Such species have
been crystallographically characterized for symmetric
phosphines, giving 6-membered, [22], 7-membered, [23],
eight-membered, [24] and 9-membered [25] chelate
rings, with the anion X, being variously NO3−, Cl− and
ClO4−. On the basis of these structural data, and our
31P NMR results, we therefore believe that complex 3,
formed with the symmetric ligand 1,2-bis(diphenylphos-
phino)ethane, (DPPE), has a similar dimeric structure,
[DPPEꢀAgꢀ(CF3SO3)ꢀAgꢀDPPE], with two triflate
bridges, and containing four coordinate silver.
With regard to the remaining two complexes, 4 and
5, containing, respectively, the bidentate phosphine lig-
ands, bis(diphenylphosphino)methane, DPPM, and 1,1-
bis(diphenylphosphino)ethane, DPMMe, the more
complicated 31P NMR spectra on the other hand, sug-
gest oligomeric structures in which the phosphines act
as bridging ligands to pairs of silver atoms, so giving
more than one type of Ag–P coupling. Both these
ligands would give rise to strained 4-membered rings if
chelated to one metal center, in contrast to the situation
for DPPE, which forms 5-membered chelate rings with
one metal center.
Such a ligand bridged structure has been character-
ized for the dimeric silver nitrate complex, [ONO2ꢀ
Ag(DPPM)2AgꢀO2NO], [26], the phosphines forming a
double bridge to the two silver atoms which have a
distorted tetrahedral geometry with bidentate nitrate
ions, and for the complex of silver bromide with a
relatedphosphine,bis(dimethylphosphino)methane DM-
PM, namely [BrꢀAg(DMPM)2AgꢀBr] [27]. In addition,
DPPM forms a similar ligand bridged structure in the
dimeric complex bis(carbomethoxycyclopentadienyl)-
bis[bis(diphenylphosphino)methane]disilver, (C5H4CO-
OCH3)2(DPPM)2Ag2, [28], while in the complex with
silver acetate, both DPPM molecules and acetate ions
act as bridging ligands to give, in the solid, a tetrameric
structure of stoichiometry [Ag2(CH3COO)2DPPM]2·
2H2O [29]. Again each silver atom exhibits an irregular
four coordinate geometry.
On the basis of these structural results, we therefore
believe it most likely that 4 and 5, [Ag(DPPM)-
(CF3SO3)] and [Ag(DPMMe)(CF3SO3)], also contain
similar dimeric phosphine bridged units, Ag2-
(DPPM)22+ and Ag2(DPMMe)22+, and that the triflate
ions either function as unidentate, or as bidentate lig-
ands to one silver atom, in each instance giving an
overall dimer, [Ag2(diphos)2(triflate)2], or that they act
as bridging ligands to link [Ag2(diphos)2]2+ dimer units
into overall tetrameric molecules or perhaps polymeric
species with alternating triflate and phosphine double
bridges.
4. Supplementary material
A listing of observed and calculated structure factors
(19 pages) and complete tables of crystal data, posi-
tional and anisotropic thermal parameters, coordinates
for hydrogen atoms, as well as complete tables of bond
distances and bond angles are available from one of the
authors (J.S.W) on request.
Acknowledgements
The authors thank Dr A. Chandrasekaran for his
help with carrying out the crystal structure refinements
and Dr Charles Dickinson for his invaluable assistance
in obtaining the solid state 31P NMR spectra.
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