Unexpected diastereoisomeric-trimers in the crystalline structure of triflatetriphenylphosphinesilver(I)

Article abstract of DOI:10.1016/S0277-5387(98)00361-1

The synthesis and spectroscopic properties of [Ag₃(O₃SCF₃)₃(PR₃) ₃] (PR₃=PPh₃ and PPh₂Me) are described and the trimeric nature has been confirmed in the case of the PPh₃ derivative. The X-ray crystal structure of [Ag₃(O₃SCF₃)₃(PPh₃) ₃] shows that each triflate group is in a different coordination mode and that there are two diastereoisomers in the asymmetric unit.

Full text of DOI:10.1016/S0277-5387(98)00361-1

Polyhedron 18 (1999) 807–810
Unexpected diastereoisomeric-trimers in the crystalline structure of
triflatetriphenylphosphinesilver(I)
Raquel Terrobaa, Michael B. Hursthousea, Mariano Lagunab, , Aranzazu Mendia
c
*
aDepartment of Chemistry, University of Wales Cardiff, PO Box 912, Cardiff CF1 3TB, UK
b
´
´
´
Departamento de Quımica Inorganica, Instituto de Ciencia de Materiales de Aragon, Universidad de Zaragoza-CSIC, 50009 Zaragoza, Spain
c
´
Departamento de Quımica, Universidad de Burgos, 09001 Burgos, Spain
Received 24 August 1998; accepted 24 September 1998
Abstract
The synthesis and spectroscopic properties of [Ag3(O3SCF3)3(PR3)3] (PR35PPh3 and PPh2Me) are described and the trimeric nature
has been confirmed in the case of the PPh3 derivative. The X-ray crystal structure of [Ag3(O3SCF3)3(PPh3)3] shows that each triflate
group is in a different coordination mode and that there are two diastereoisomers in the asymmetric unit.
All rights reserved.
1999 Elsevier Science Ltd.
Keywords: Silver; Trinuclear complexes; Triflate; Triphenylphosphine; Diastereoisomers
1. Introduction
2. Experimental
Silver salts have widespread applications in synthetic
procedures as halogen abstractors [1,2], one electron
oxidants [2–5] or as building blocks [6–14] in the prepara-
tion of heteropolynuclear complexes. For all these pur-
poses Ag(OClO3) has been widely used and some deriva-
tives such as [Ag(OClO3)L] (L5PPh3, PPh2Me or tetrahy-
drothiophene) have proved to be appropriate synthons for
heteronuclear silver complexes. Due to the inherent
hazards of metal perchlorates as potential explosives we
need to look for similar complexes with other non strong
coordinating counterion. The compound Ag(O3SCF3) has
been used by many authors [15–18] as a safer source of
silver ions and we tested [Ag(O3SCF3)L]n as a silver
synthon for heteronuclear complexes [19,20]. Here we
describe an easier preparation than previously reported for
the silver triflate derivatives of triphenyl- and
methyldiphenyl-phosphine, and also their spectroscopic
properties. The X-ray crystal structure of the tri-
phenylphosphine derivative consists of a trinuclear silver
complex with the three triflates in three different coordina-
tion modes, and the presence of two diastereoisomers in
the same unit cells.
2.1. General procedures
The C, H, S analyses were carried out on a Perkin-Elmer
2400 Microanalyser. Conductivities were measured in
approximately 531024 mol dm23 acetone solutions, with
Jenway 4010 Conductimeter. The melting points were
measured using a Gallenkamp apparatus and are uncor-
rected. The Infrared spectra were recorded (4000–200
cm21) on a Perkin-Elmer 883 Spectrophotometer, using
Nujol mulls between polyethylene sheets. The NMR
spectra were recorded on a Bruker ARX 300 Spectrometer,
in CD2Cl2. Chemical Shifts are cited relative to SiMe4
(1H), 85% H3PO4 (external 31P) and CFCl3 (19F). Mass
spectra were recorded on VG Autospec LSIMS Technique
using 3-nitrobenzylalcohol as a matrix and a Cesium gun.
2.2. Preparation of [Ag3(O3SCF3 )3(PR3 )3 ] [L5PPh3 (1),
PPh2Me (2)]
To a diethyl ether (30 cm3) solution of [Ag(O3SCF3)]
(0.252g, 1 mmol), was added PPh3 (0.262 g, 1 mmol) or
PPh2Me (0.200 g, 1 mmol). After 1 h the solution was
concentrated in vacuum until 5 cm3 and after addition of
hexane (30 cm3) led the precipitation of the new complex-
1
es as white solids. Yield%: 85 1, 82 2. H NMR: 1:
d57.6–7.3 (m, 15H, Ph). 2: d57.55–7.35 (m, 10H, Ph);
*
Corresponding author.
0277-5387/99/$ – see front matter
PII: S0277-5387(98)00361-1
1999 Elsevier Science Ltd. All rights reserved.

808
R. Terroba et al. / Polyhedron 18 (1999) 807–810
1.95 (s,br, 3H, Me). 31P-h1Hj NMR 1: d514.5 (s) at r.t. and
14.7 (dd, 2J107AgP5740.6 Hz, 2J109AgP5855.0 Hz) at 2808C.
3. Results and discussion
2
2: d521.7 (s) at r.t. and 21.8 (dd, J107AgP5768.0 Hz,
The addition of the corresponding phosphine to a
diethylether solution of [Ag(O3SCF3)] in a 1:1 ratio is an
easier way to synthesize [Ag3(O3SCF3)3(PR3)3] (PR35
PPh3, 1; PPh2Me, 2) than previously reported [20]. The
spectroscopic data for complexes 1 and 2 are in agreement
with the proposed estoichiometry. IR spectra show absorp-
tions at 1285 (vs, br), 1250 (vs, br), 1224 (vs), 1209 (vs)
and 1170 (vs, br) for 1 and 1316 (vs), 1288 (vs, br), 1231
(vs), 1223 (vs) and 1184 (vs, br) for 2 which can be
assigned to a covalent coordination of the triflate group
[25,26]. In accordance with that their dichloromethane
solutions behave as non conductors, although the acetone
solutions show conductivities characteristic of 1:1 elec-
trolytes, probably because of the replacement of triflate by
solvent molecules [19,20,27]. The 31Ph1Hj NMR spectra at
room temperature consist of broad singlets which split into
two doublets at 2808C because of the presence of two
2J109AgP5875.9 Hz) at 2808C. 19F NMR 1: d5278.0 (s). 2:
d5277.7 (s). Mass spectra, m/z(%): 1: 1409(2)
([Ag3(O3SCF3)2(PPh3)3]1),
889(15)
([Ag2(O3SCF3)(PPh3)2]1), 369(100) ([Ag(PPh3)]1). 2:
1223(1)
([Ag2(O3SCF3)(PPh2Me)2]1),
([Ag3(O3SCF3)2(PPh2Me)3]1),
765(9)
307(100)
([Ag(PPh2Me)]1) M.p. 1328C 1, 788C (decomp.) 2.
Elemental analysis 1 C57H45Ag3F9O9P3S3 (1557.63):
calcd. C 43.9, H 2.9, S 6.2; found: C, 44.1; H, 3.0; S, 6.5;
2 C42H39Ag3F9O9P3S3 (1371.47): calcd. C 36.8, H 2.5, S
7.0; found C 36.5, H 2.8, S 7.3. LM in acetone 1: 122, 2:
124 ohm21 cm2 mol21. In dichloromethane 1: 3.8, 2: 2.4
ohm21 cm2 mol21
.
2.3. X-ray determination of compound 1
2
2
isotopomers with J107AgP5740.6 Hz, and J109AgP5855.0
Single crystals were grown by diffusing hexane into a
dichloromethane solution of complex (1) at room tempera-
ture and mounted in inert oil.
2
Hz in 1 and J107AgP5768.0 Hz, 2J109AgP5875.9 Hz in 2.
The magnitude of the Ag-P coupling constants have been
related with the coordination core for series of nitrate
triphenylphosphine silver(I) complexes. So complexes
[Ag(NO3)(PPh3)n] show different coupling constants
[28,29] that depend on the values of n: n54 (P4 coordina-
tion core) J107AgP5109 Hz, n53 (P3O coordination core)
2.4. Crystal data and data collection parameters
C114H90Ag6F18O18P6S6, M53115.26, monoclinic, a5
˚
25.896(4),
b513.1150(10),
c535.578(4)A,
b5
J
J
107AgP5310 Hz and n52 (P2O2 coordination core)
107AgP5470 Hz. Although the latter values belong to
3
˚
106.89(2)8, U511562(2)A , T5150K, space group P21 /n,
˚
graphite monochromated Mo-Ka radiation l50.71069 A,
c.p.m.a.s values, the data found in CD2Cl2 solutions for
complexes 1 and 2 point to a coordination core with a high
contribution of oxygen atoms which probably requieres a
non mononuclear structure. On the other hand, the 19F
NMR spectra show singlets at room temperature which
persist even at 2808C. The liquid secondary ion mass
spectra (LSIMS1) show the trinuclear ion less a triflate
anion [Ag3(O3SCF3)2(PR3)3]1, as well as the corre-
sponding di-[Ag2(O3SCF3)(PR3)2]1 and mono-nuclear
species [Ag(PR3)]1, the latter being the base peak in both
complexes. The presence of trinuclear species and the
absence of higher nuclearities can be considered as evi-
dence of the trinuclear structure of these complexes.
Z54, Dc51.790 Mg m23, F(000)56192, colorless prism
with dimensions 0.1830.1630.14 mm, m51.283 mm21
;
Delft Instruments FAST TV area detector diffractometer
positioned at the window of a rotating-anode generator,
following procedures described elsewhere [21], u range for
data collection 1.76 to 25.738, -28>h>0, 0>h>18, -14>
k>0, 0>k>11, -43>l>0, 0>l>42; 32686 reflections
collected, 16224 independent (Rint50.1444).
2.5. Structure solution and refinement
The structure was solved by direct methods using
SHELXS 86 [22], and refined by full-matrix least squares
on F2o, using the program SHELXL 93 [23]. All data used
were corrected for Lorentz-polarization factors, and sub-
sequently for absorption using the program DIFABS [24].
The non-hydrogen and non-carbon atoms were refined with
anisotropic thermal parameters. All hydrogen atoms were
included in idealized positions. The refinement was per-
formed with rigid bond restrictions in some oxygen atoms.
Refinement proceeded to R50.0370, wR50.0579 for 2339
data with Io.2s (Io) and goodness of fit on F2 0.356 for
943 parameters and 30 restraints, and R50.2565, wR5
0.1095 for all data. In the final Fourier synthesis the
The
molecular
structure
of
the
complex
[Ag3(O3SCF3)3(PPh3)3], has been established by X-ray
diffraction and is shown in Fig. 1. Selected bond lengths
and angles are given in Table 1. Although the crystal and
thus the data were not of good quality, the resolution and
refinement of the structure confirms the trimeric nature of
1 and it consists of two trimeric molecules that are
conformational isomers of each other. In the first of them,
the three silver centers are each bonded to one tri-
phenylphosphine and the triflate units bridge the metal
centers. One silver atom, Ag(2), is in a trigonal-planar
arrangement, bonded to its one phosphine with an Ag-P
˚
electron density fluctuates in the range 0.387 to 20.481 e
distance of 2.363(5)A and two oxygen atoms from differ-
23. CCDC number 102746.
ent triflates with Ag-O distances of 2.492(13) and
˚
A

R. Terroba et al. / Polyhedron 18 (1999) 807–810
809
˚
2.236(12)A. The four atoms Ag(2), P(2), O(11) and O(31)
˚
belong to the same plane, Ag(2) being 0.021A out of this
plane. The other silver atoms, Ag(1) and Ag(3), are in
distorted tetrahedral configurations and are bonded to one
˚
phosphine with Ag-P distances of 2.327(5) and 2.341(5)A
both slightly shorter than that mentioned above. All are in
the range found for other Ag(PPh3) fragments [12–14,28–
30]. The tetrahedral arrangement is completed by three
oxygen atoms, one from each triflate unit with variable
˚
Ag-O distances, from 2.29(2)A (Ag(3)-O(21)) to
˚
2.546(12)A (Ag(1)-O(12)).
Although some examples of monobi- and tri-dentate
coordination of the triflate anion have been reported
[19,25,26,31–39] this is one of the rare examples with the
three triflate ligands in three different coordination modes.
One is monodentate, the one with S(2), so it possesses two
free oxygen atoms O(22) and O(23), while the other one,
O(21), acts as a bridge between Ag(1) and Ag(3) (m2 1:3
k2O). The S(1) triflate unit is bidentate, with the O(13)
atom free. O(11) is bonded only to Ag(2) and O(12) is
bridging to Ag(1) and Ag(3), so this triflate acts as bridge
for the three metal centers (m3 2kO, 1:3 k2O9). The S(3)
triflate unit is tridentate, acting like a bridge for all the
silver atoms, but each oxygen from this ligand is bonded
only to one silver (m3 1kO, 2kO9, 3kO0). The Ag-O bond
length between Ag(2) and the latter triflate unit mentioned,
Fig. 1. Molecule of the complex [Ag3(O3SCF3)3(PPh3)3] in the crystal.
Table 1
Selected bond lengths (A) and angles (8) for [Ag3(O3SCF3)3(PPh3)3] (1)
˚
˚
2.236(12)A, is the shortest found with this type of ligands.
Ag(1)-P(1)
Ag(1)-O(21)
Ag(2)-O(31)
Ag(2)-O(11)
Ag(3)-P(3)
Ag(3)-O(12)
S(1)-O(13)
S(1)-C(1)
S(2)-O(21)
S(2)-C(2)
S(3)-O(31)
S(3)-C(3)
2.327(5)
2.388(11)
2.236(12)
2.492(13)
2.341(5)
2.467(10)
1.454(10)
1.78(2)
1.430(13)
1.77(2)
1.472(12)
1.81(2)
Ag(1)-O(32)
Ag(1)-O(12)
Ag(2)-P(2)
Ag(3)-O(21)
Ag(3)-O(33)
S(1)-O(12)
S(1)-O(11)
S(2)-O(23)
S(2)-O(22)
S(3)-O(32)
S(3)-O(33)
2.338(14)
2.546(12)
2.363(5)
2.29(2)
2.432(11)
1.449(11)
1.482(14)
1.407(11)
1.440(12)
1.47(2)
The above mentioned [hHgAg2(mes)2(O3SCF3)2j2] [19]
˚
has one of its Ag-O distances 2.300(8)A, being previously
the smallest.
These trimers have four optically active atoms, the
sulfur from the triflate units, except the monodentate one,
and the two tetrahedral silver atoms. In both molecules
these centers are in the same configuration, except S(1)
(labelled S(4) in the other molecule), that is in a different
configuration, see Fig. 2; the molecules are diasteroisom-
ers.
1.480(11)
P(1)-Ag(1)-O(32)
O(32)-Ag(1)-O(21)
O(32)-Ag(1)-O(12)
O(31)-Ag(2)-P(2)
P(2)-Ag(2)-O(11)
O(21)-Ag(3)-O(33)
O(21)-Ag(3)-O(12)
O(33)-Ag(3)-O(12)
O(12)-S(1)-O(11)
O(12)-S(1)-C(1)
O(11)-S(1)-C(1)
S(1)-O(12)-Ag(3)
Ag(3)-O(12)-Ag(1)
O(23)-S(2)-O(22)
O(23)-S(2)-C(2)
O(22)-S(2)-C(2)
S(2)-O(21)-Ag(1)
O(32)-S(3)-O(31)
O(31)-S(3)-O(33)
O(31)-S(3)-C(3)
S(3)-O(31)-Ag(2)
S(3)-O(33)-Ag(3)
117.1(3)
94.8(4)
89.2(4)
157.4(3)
104.9(3)
94.9(5)
P(1)-Ag(1)-O(21)
P(1)-Ag(1)-O(12)
O(21)-Ag(1)-O(12)
O(231)-Ag(2)-O(11)
O(21)-Ag(3)-P(3)
P(3)Ag(3)-O(33)
P(3)-Ag(3)-O(12)
O(12)-S(1)-O(13)
O(13)-S(1)-O(11)
O(13)-S(1)-C(1)
S(1)-O(11)-Ag(2)
S(1)-O(12)-Ag(1)
O(23)-S(2)-O(21)
O(21)-S(2)-O(22)
O(21)-S(2)-C(2)
S(2)-O(21)-Ag(3)
Ag(3)-O(21)-Ag(1)
O(32)-S(3)-O(33)
O(32)-S(3)-C(3)
O(33)-S(3)-C(3)
S(3)-O(32)-Ag(1)
134.8(4)
134.7(3)
71.7(4)
The mass spectra seem to indicate that the trinuclear
structure remains in solution as by the high Ag-P coupling
constants characteristic of a PO3 coordination core in the
NMR spectra. On the other hand, the presence of only one
type of phosphorus, even at 2808C, as well as only one
type of trifluoromethyl group indicates that the trinuclear
structure either is not the same in solution as in the solid
state or the triflate anions are moving in the NMR time
scale making both triflate and phosphine units, respective-
ly, equivalent.
97.6(4)
144.7(3)
104.5(3)
136.5(3)
115.0(8)
114.0(8)
104.4(8)
106.4(6)
111.7(5)
114.5(10)
114.5(7)
99.8(9)
125.9(7)
105.7(5)
114.4(8)
101.3(10)
104.0(8)
133.3(7)
74.8(4)
81.5(4)
115.4(7)
106.0(9)
99.8(10)
128.9(7)
96.1(4)
118.0(8)
104.0(9)
102.6(10)
127.3(8)
115.8(7)
116.4(8)
101.8(9)
129.2(7)
138.6(8)
Acknowledgements
´
The Spanish authors thank the Direccion General de
´
´
´
Investigacion Cientıfica y Tecnica (Grant PB95-0140) for
´
financial support and Ministerio de Educacion y Cultura
for a grant (to R.T.), and M.B.H. thanks the Engineering

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R. Terroba et al. / Polyhedron 18 (1999) 807–810
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