Silver(I) methanesulfonate complexes containing diphosphine ligands: Spectroscopic and structural characterization

Article abstract of DOI:10.1016/j.ica.2009.02.036

1:1 and 2:1 adducts of diphosphine ligands R₂P(R′)_nPR₂ (dppm: R = Ph, R′ = CH₂, n = 1; dppe: R = Ph, R′ = CH₂, n = 2; dppp: R = Ph, R′ = CH₂, n = 3; dppb: R = Ph, R′ = CH₂, n = 4; dppf: R = Ph, R′ = ferrocenyl, n = 1) with silver(I) methanesulfonate have been synthesized and characterized both in solution (¹H, ³¹P NMR) and in the solid state (IR, single crystal X-ray structure analysis). The two different stoichiometries have been found to depend on the molar ratio of ligand to metal employed and the nature of the diphosphine ligand. In AgO₃SMe:dppp,dppb (1:1)₂, in the [Ag(P^P)₂Ag] arrays, the silver atoms are also bridged by anion oxygen atoms, in disparate fashion commensurate with the different Ag?Ag distances.

Full text of DOI:10.1016/j.ica.2009.02.036

Inorganica Chimica Acta 362 (2009) 3225–3230
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Silver(I) methanesulfonate complexes containing diphosphine ligands:
Spectroscopic and structural characterization
a
a
b
b
Claudio Pettinari a, , Jean Ngoune , Alessandro Marinelli , Brian W. Skelton , Allan H. White
*
a Dipartimento di Scienze Chimiche, Università di Camerino, via S. Agostino 1, 62032 Camerino (MC), Italy
b Chemistry M313, SBBCS, University of Western Australia, Crawley, WA 6009, United States
a r t i c l e i n f o
a b s t r a c t
1:1 and 2:1 adducts of diphosphine ligands R2P(R0)nPR2 (dppm: R = Ph, R0 = CH2, n = 1; dppe: R = Ph,
R0 = CH2, n = 2; dppp: R = Ph, R0 = CH2, n = 3; dppb: R = Ph, R0 = CH2, n = 4; dppf: R = Ph, R0 = ferrocenyl,
n = 1) with silver(I) methanesulfonate have been synthesized and characterized both in solution (1H,
31P NMR) and in the solid state (IR, single crystal X-ray structure analysis). The two different stoichiom-
etries have been found to depend on the molar ratio of ligand to metal employed and the nature of the
diphosphine ligand. In AgO3SMe:dppp,dppb (1:1)2, in the [Ag(P^P)2Ag] arrays, the silver atoms are also
bridged by anion oxygen atoms, in disparate fashion commensurate with the different Agꢀ ꢀ ꢀAg distances.
Ó 2009 Elsevier B.V. All rights reserved.
Article history:
Received 10 December 2008
Received in revised form 22 February 2009
Accepted 23 February 2009
Available online 9 March 2009
Keywords:
Ag(I) complexes
Diphosphine ligands
Crystal structure
Spectroscopy
1. Introduction
2. Experimental
Silver methanesulfonate is photostable and commercially avail-
able, showing no air sensitivity, and employed as a standard for sil-
ver CP/MAS experiments [1]. Some reports have appeared recently
on silver sulfonate derivatives exhibiting a rich structural diversity,
as exemplified in one-, two- or three-dimensional polymeric struc-
tures [2–6]. However, the number of silver species thus far isolated
stabilized by Lewis bases or other ancillary ligands is very limited,
notwithstanding their potential use in catalysis [7] and in materi-
als science [8], and the well-known versatility of methanesulfonate
precꢁursors, through, for example, the relative lability of bound
RSO;3 maintained throughout the d-block metal ions [9]. Organo-
phosphine and phosphite stabilized silver(I) methanesulfonate
complexes have been described recently [10], also discussing their
thermal stability; syntheses, structures and luminescence of
mononuclear, dinuclear and tetranuclear silver(I) sulfonate com-
plexes with PPh3 have also been reported [11]. Further it has re-
cently been shown that the dinuclear, cyclic structural motif
[Ag2(diphosphine)2]2+ can be employed as a synthon for building
up coordination cages containing large cavities [12], depending
on the chain between the two phosphorus donor sites. Here we re-
port on the interaction between silver(I) methanesulfonate with
diphosphine ligands, which, to date, have been neglected with re-
spect to monodentate phosphines.
2.1. Materials and methods
AgO3SMe and R2P(R0)nPR2 (dppm: R = Ph, R0 = CH2, n = 1; dppe:
R = Ph, R0 = CH2, n = 2; dppp: R = Ph, R0 = CH2, n = 3; dppb: R = Ph,
R0 = CH2, n = 4; dppf: R = Ph, R0 = ferrocenyl, n = 1) were purchased
from Aldrich and used without further purification. All reactions
were carried out under an atmosphere of dry oxygen-free dinitro-
gen, using standard Schlenk techniques and protected from light.
All solvents were dried, degassed and distilled prior to use. Ele-
mental analyses (C,H,S) were performed with a Fisons Instruments
1108 CHNS-O Elemental Analyser. IR spectra were recorded from
4000 to 100 cmꢁ1 with a Perkin–Elmer System 2000 FT-IR instru-
ment. 1H and 31P NMR spectra were recorded on a VXR-300 Varian
spectrometer operating at room temperature (300 MHz for 1H) and
on a Mercury-Plus Varian 400 NMR spectrometer (400 for 1H and
162.4 MHz for 31P, respectively). Referencing is relative to TMS
(1H) and H3PO4 31P). The electrical resistance of CH2Cl2 and ace-
(
tone solutions was measured with a Crison CDTM 522 conductim-
eter at room temperature. Melting points were obtained using a
Stuart SMP3 melting point apparatus and were not corrected. Posi-
tive and negative electrospray mass spectra were obtained with a
Series 1100 MSI detector HP spectrometer, using an acetonitrile
mobile phase. Solutions (3 mg/mL) for electrospray ionization
mass spectrometry (ESI MS) were prepared using reagent grade
acetone or acetonitrile. For the ESI MS data, masses and intensities
were compared to those calculated by using the IsoPro Isotopic
Abundance Simulator Version 2.1 [13]; peaks containing silver(I)
and copper ions are identified as the centres of isotopic clusters.
* Corresponding author. Tel.: +39 0737 402234; fax: +39 0737 637345.
E-mail address: Claudio.pettinari@unicam.it (C. Pettinari).
0020-1693/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2009.02.036

3226
C. Pettinari et al. / Inorganica Chimica Acta 362 (2009) 3225–3230
2.2. Syntheses
764m, 742s, 694s, 664m, 617w, 551m, 522m, 508m, 485m,
477m, 450w, 412w, 377w, 342w, 278w, 255w, 227w, 206w. Anal.
Calc. for C29H31AgO3P2S: C, 55.34; H, 4.96; S, 5.09. Found: C,
55.02; H, 5.19; N, 4.75%. ESI MS (+): 457 [100] [(dppbO2)+H]+;
916 [40] [(dppbO2)2+H]+; 961 [10] [Ag(dppp)2]+, 1104 [25]
[Ag2Cl(dppb)2]+.
2.2.1. Synthesis of AgO3SMe:dppm (1:1) (1)
AgO3SMe (0.203 g, 1.0 mmol) was added to an ethanol solution
(30 ml) of dppm (0.384 g, 1.0 mmol), at room temperature. After
the addition, the solution was stirred for 24 h at room temperature
in the dark. A colorless precipitate formed in 70% yield which was
filtered off and washed with ethanol (10 ml). M.p. 298–302 °C. 1H
NMR (CDCl3, 293 K): d 2.60s (SO3CH3), 3.29s (2H, P(CH2)P), 7.1–
7.5m (40H, PC6H5). 31P NMR (CDCl3, 293 K): 8.4 br. 31P NMR (CDCl3,
223 K): 9.56m (1J(107Ag–31P): 489 Hz, 2J(P–P): 160 Hz;
3J(107Ag–31P: ꢁ4.5 Hz; 1J(107Ag–31P): 561 Hz, 3J(107Ag–31P:
2.2.5. Synthesis of AgO3SMe:dppf (1:1) (5)
Derivative 5 has been prepared in 65% yield, following the pro-
cedure reported for 2, by using AgO3SMe (0.203 g, 1.0 mmol) and
dppf (0.554 g, 1.0 mmol), at 40 °C. M.p. 186 °C dec. 1H NMR (CDCl3,
293 K): d 2.85s (3H, SO3CH3), 4.2–4.4m (8H, PFc2P), 7.2–7.6m (20H,
PC6H5). 31P NMR (CDCl3, 293 K): 2.1 dd (1J(109Ag–31P): 498 Hz;
1J(107Ag–31P): 438 Hz). Km (Acetone, conc. = 0.9 ꢂ 10ꢁ3 M):
ꢁ5.2 Hz). Km (CH2Cl2, conc. = 0.88 ꢂ 10ꢁ3 M): 16.5
X .
ꢁ1 cm2 molꢁ1
IR (cmꢁ1): 3040sh [
m(C–H)], 1445w, 1309m, 1226m, 1150m, 1137s,
616w, 547m, 513s, 481m, 470m, 439w, 421w, 339m. Anal. Calc. for
C26H25AgO3P2S: C, 53.17; H, 4.29; S, 5.46. Found: C, 53.32; H, 4.33;
S, 5.55%. ESI MS (+): 1019 [100] [Ag2Cl(dppm)2]+.
19.0
X
ꢁ1 cm2 molꢁ1. IR (cmꢁ1): 1584w, 1570w, 1558w [
m
(Cꢀ ꢀ ꢀC)],
1235m, 1166m, 1151m, 1097m, 893w, 835w, 765m, 744m,
723w, 706w, 698s, 661w, 650w, 634w, 600w, 583w, 576w,
568w, 550m, 538m, 514m, 496m, 483m, 466m, 427m, 399w,
375w, 363w, 352w, 327w, 314w, 304w, 284w, 279m, 254w,
247m, 228m, 224m, 213m. Anal. Calc. for C35H31AgFeO3P2S: C,
55.51; H, 4.13; S, 4.23. C, 55.86; H, 4.35; N, 4.03%. ESI MS (+):
189 [100] [Ag(MeCN)2]+; 662 [20] [Ag(dppf)]+; 865 [40]
[Ag2(O3SMe)(dppf)]+.
2.2.2. Synthesis of AgO3SMe:dppe (1:1) (2)
AgO3SMe (0.203 g, 1.0 mmol) was added to an ethanol solution
(30 ml) of dppp (0.396 g, 1.0 mmol), at room temperature. After
the addition, the solution was stirred for 24 h at room temperature
in the dark. A colorless precipitate formed which was filtered off
and washed with ethanol (10 ml). Crystallization from ethanol
gave complex 2 as a microcrystalline solid in 60% yield. M.p.
249–252 °C dec. 1H NMR (CDCl3, 293 K): d 2.4br 2.65s (4H,
P(CH2)2P + 3H, SO3CH3), 7.2–7.5m (20H, PC6H5). 31P NMR (CDCl3,
223 K): 9.7 d br (1J(Ag–31P): 440 Hz); 13.5 dd (1J(109Ag–31P):
2.2.6. Synthesis of AgO3SMe:dppe 1:2 (6)
AgO3SMe (0.203 g, 1.0 mmol) was added to a methanol solution
(30 ml) of dppe (0.795 g, 2.0 mmol), at 40 °C. After the addition, the
solution was stirred for 24 h at room temperature in the dark. A
colorless precipitate formed which was filtered off and washed
with methanol (6 ml). Crystallization from methanol gave complex
6 as a microcrystalline solid in 70% yield. M.p. 138 °C dec. 1H NMR
(CDCl3, 293 K): d 2.15, 2.45 (11H, P(CH2)2P + SO3CH3), 7.1–7.5m
(40H, PC6H5). 31P NMR (CDCl3, 293 K): +6.1 (1J(109Ag–31P):
266 Hz; 1J(107Ag–31P): 230 Hz). Km (acetone, conc. = 0.9 ꢂ 10ꢁ3 M):
695 Hz; 1J(107Ag–31P): 604 Hz. IR (cmꢁ1): 3117w, 3050w [
H)], 1558w, 1523w, 1512w, 1478m, 1433m [
118m, 1170m, 1155m, 1106m, 1095m, 101m, 552s, 509s, 485m,
473m, 447m. Anal. Calc. for C27H27AgO3P2S: C, 53.92; H, 4.53; S,
5.33. Found: C, 54.00; H, 4.56; N, 5.28%. ESI MS (+): 429 [100]
[(dppeO2)+H]+; 860 [80] [(dppeO2)2+H]+; 905 [40] [Ag(dppe)2]+,
1048 [5] [Ag2Cl(dppe)2]+.
m
(C–
m
(Cꢀ ꢀ ꢀC)], 1231m,
97.5
X
ꢁ1 cm2 molꢁ1. IR (cmꢁ1): 3056m [
m
m
(C–H)], 1653w, 1636w,
(Cꢀ ꢀ ꢀC)], 1482m, 1434s,
1584w, 1570w, 1559w, 1540w, 1506w [
2.2.3. Synthesis of AgO3SMe:dppp (1:1) (3)
1308m, 1214s, 1198s, 1181s, 1154s, 1096s, 1039s, 998m, 863w,
744s, 700s, 663s, 654s, 617m, 550s, 520s, 506s, 480s, 457m,
448m, 348m. Anal. Calc. for C53H51AgO3P4S: C, 63.67; H, 5.14; S,
3.21. Found: C, 64.12; H, 5.15; N, 3.07%. ESI MS (+): 905 [100]
[Ag(dppe)2]+.
AgO3SMe (0.203 g, 1.0 mmol) was added to a methanol solution
(30 ml) of dppp (0.410 g, 1.0 mmol), at 40 °C. After the addition, the
solution was stirred for 24 h at room temperature in the dark. A
colorless precipitate formed which was filtered off and washed
with methanol (6 ml). Crystallization from methanol gave complex
3 as a microcrystalline solid in 40% yield. M.p. 300 °C dec. 1H NMR
(CDCl3, 293 K): d 2.0–2.4br (6H, P(CH2)3P), 2.91s (3H, SO3CH3), 7.2–
7.5m (20H, PC6H5). 31P NMR (CDCl3, 293 K): 9.9 dd (1J(109Ag–31P):
2.2.7. Synthesis of AgO3SMe:dppp (1:2) (7)
AgO3SMe (0.203 g, 1.0 mmol) was added to a methanol solution
(30 ml) of dppp (0.818 g, 2.0 mmol), at 40 °C. After the addition, the
solution was stirred for 24 h at room temperature in the dark. A
colorless precipitate formed which was filtered off and washed
with methanol (6 ml). Crystallization from methanol gave complex
7 as a microcrystalline solid in 60% yield. M.p. 174 °C dec. 1H NMR
(CDCl3, 293 K): d 1.83s br, 2.4t (12H, P(CH2)3P), 2.80s (3H, SO3CH3),
7.2–7.5m (40H, PC6H5). 31P NMR (CDCl3, 293 K): ꢁ4.7 dd
(1J(109Ag–31P): 254 Hz; 1J(107Ag–31P): 220 Hz. Km (acetone, con-
577 Hz; 1J(107Ag–31P): 501 Hz. IR (cmꢁ1): 3067w, 3041w [
H)], 1585w, 1571w [
m
(C–
m(Cꢀ ꢀ ꢀC)], 1308m, 1215m, 1197m, 1181m,
1153m, 1097m, 1037m, 1027m, 696s, 617m, 549s, 522s, 508s,
476s, 446s, 433m, 387m, 353m, 339m, 325m, 314m, 302m,
288w, 276w, 260w, 247w, 230w, 225w, 213w. Anal. Calc. for
C28H29AgO3P2S: C, 54.65; H, 4.75; S, 5.21. Found: C, 54.45; H,
4.96; N, 5.30%. ESI MS (+): 443 [100] [(dpppO2)+H]+; 888 [60]
[(dpppO2)2+H]+; 933 [20] [Ag(dppp)2]+, 1076 [15] [Ag2Cl(dppp)2]+.
c. = 0.96 ꢂ 10ꢁ3 M): 90.1
X
ꢁ1 cm2 molꢁ1. IR (cmꢁ1): 3058m [
(Cꢀ ꢀ ꢀC)], 1482m, 1434s,
m(C–
H)], 1654w, 1585w, 1570w, 1508w [
m
2.2.4. Synthesis of AgO3SMe:dppb (1:1) (4)
1214s, 1199m, 1181m, 1154m, 1096m, 1040s, 1026w, 998w,
693s, 650s, 616m, 551m, 510s, 483, 439m, 407m, 349w, 304w,
290w, 279w, 254w, 226w. Anal. Calc. for C55H55AgO3P4S: C,
64.27; H, 5.39; S, 3.12. Found: C, 64.32; H, 5.35; N, 3.03%.
AgO3SMe (0.203 g, 1.0 mmol) was added to a methanol solution
(30 ml) of dppb (0.423 g, 1.0 mmol), at 40 °C. After the addition, the
solution was stirred for 24 h at room temperature in the dark. The
solution was then stored at 5 °C. Colorless crystals (65%) slowly
formed which were filtered off and washed with methanol
(10 ml). M.p. 261 °C dec. 1H NMR (CDCl3, 293 K): d 1.95s br, 2.56s
(6H, P(CH2)4P), 2.26s (3H, SO3CH3), 7.2–7.6m (20H, PC6H5). 31P
NMR (CDCl3, 293 K): 1.7 dd (1J(109Ag–31P): 539 Hz; 1J(107Ag–31P):
2.2.8. Synthesis of AgO3SMe:dppb (1:2) (8)
AgO3SMe (0.203 g, 1.0 mmol) was added to a methanol solution
(30 ml) of dppb (0.818 g, 2.0 mmol), at 40 °C. After the addition, the
solution was stirred for 24 h at room temperature in the dark. A
colorless precipitate formed which was filtered off and washed
with methanol (6 ml). Crystallization from methanol gave complex
8 as a microcrystalline solid in 45% yield. M.p. 222 °C dec. 1H NMR
466 Hz). Km (CH2Cl2, conc. = 0.5 ꢂ 10ꢁ3 M): 12.0
X
ꢁ1 cm2 molꢁ1
.
IR (cmꢁ1): 3057m [
m(C–H)], 1584w, 1573w [m
(Cꢀ ꢀ ꢀC)], 1310m,
1278m, 1211m, 1186m, 1165s, 1146s, 1100m, 1070m, 792w,

C. Pettinari et al. / Inorganica Chimica Acta 362 (2009) 3225–3230
3227
Fig. 1. (a,b) Projections of the dimers of 3, 4, (i,ii) through, and normal to, their Ag2P4 planes.
(CDCl3, 293 K): d 2.05–2.23br (16H, P(CH2)4P), 2.73s (3H, SO3CH3),
2.3. Structure determinations
7.1–7.45 m (40H, PC6H5). 31P NMR (CDCl3, 293 K): ꢁ0.1 dd
(1J(109Ag–31P): 257 Hz; 1J(107Ag–31P): 219 Hz. Km (CH2Cl2, con-
Full spheres of CCD area-detector diffractometer data were
measured at ca. 153 K (monochromatic Mo radiation,
k = 0.71073 Å; -scans, 2hmax = 58°) yielding Nt(otal) reflections,
c. = 0.5 ꢂ 10ꢁ3 M): 23.0
X
ꢁ1 cm2 molꢁ1. IR (cmꢁ1): 3050m [
m
(C–
Ka
H)], 1585w, 1558w [
m
(Cꢀ ꢀ ꢀC)], 1216s, 1175s, 740s, 721m, 694sd,
x
618w, 550w, 518m, 479m, 444w, 396w, 344w, 301w. Anal. Calc.
for C57H59AgO3P4S: C, 64.84; H, 5.63; S, 3.04. Found: C, 64.45; H,
5.65; S, 2.59%.
these merging to N independent (Rint cited), after ‘empirical’/mul-
tiscan absorption correction (proprietary software), these being
used in the full matrix least squares refinements on F2, refining
anisotropic displacement parameters for the non-hydrogen atoms,
hydrogen atom treatment following a riding model; No reflections
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
R
Ag
R
R
R
with F > 4r(F) were considered ‘observed’. Neutral atom complex
P
P
P
P
P
P
scattering factors were employed; computation used the SHELXL
97 program [14]. Reflection weights were ðr2ðF2Þ þ ðaPÞ þ bPÞꢁ1
2
O3SMe
Ag
P
Ag
P
ðP ¼ ðF2o þ 2F2c Þ=3Þ. Pertinent results are given below and in the ta-
bles and Fig. 1, the latter showing 50% probability amplitude dis-
placement envelopes for the non-hydrogen atoms, hydrogen
atoms having arbitrary radii of 0.1 Å. Full .cif depositions reside
MeSO3
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
with
the
Cambridge
Crystallographic
Data
Centre,
#708681,708682.
R = (CH2)n, n = 1, 2,3 or 4
R = 4,4-ferrocenyl
R = (CH2)n, n = 2,3 or 4
2.3.1. Crystal/refinement data
2.3.1.1. AgO3SMe:dppp (1:1)2 (3). C56H58Ag2O6P4S2, M = 1230.8. Tri-
1:2 adducts
1:1 adducts
1
ꢀ
clinic, space group P1ðCi ; No: 2Þ, a = 10.492(1), b = 11.948(1)
Chart 1.
c = 13.073(1) Å, a = 69.006(1), b = 66.349(1), c = 66.857(1)°, V =

3228
C. Pettinari et al. / Inorganica Chimica Acta 362 (2009) 3225–3230
Fig. 2. ESI MS spectra (MeCN, positive mode) of compounds 1 (a), 5 (b) and 2 (c).
1341 Å3. Dc (Z = 1) = 1.524 g cmꢁ3
0.65 ꢂ 0.40 ꢂ 0.10 mm; ‘T’min/max = 0.68. Nt = 15442, N = 6495
(Rint = 0.028), No = 5667; R1 = 0.040, wR2 = 0.108 (a = 0.056,
b = 2.2); S = 1.05.
Variata. Phenyl ring 22n was modelled as disordered over two
sites, occupancies refining to 0.644(7) and complement.
.
l
Mo = 0.98 mmꢁ1; specimen:
1.509 g cmꢁ3
.
l
Mo = 0.94 mmꢁ1
;
specimen:
0.45 ꢂ 0.40 ꢂ
0.16 mm; ‘T’min/max = 0.64. Nt = 15819, N = 6701 (Rint = 0.026),
No = 6358; R1 = 0.027, wR2 = 0.076 (a = 0.045, b = 1.3); S = 1.05.
Variata. A difference map residue was modelled in terms of a
water molecule oxygen fragment, O(01), occupancy refining to
0.228(8); associated hydrogen atoms were not located.
O(01)ꢀ ꢀ ꢀ(sulfate) O(2) is 2.683(10) Å.
2.3.1.2.
AgO3SMe:dppb
(1:1)2,
4
(ꢀ0.48H2O). C58H62A-
ꢀ
g2O6P4S2 ꢀ 0.48H2O, M = 1267.5. Triclinic, space group P1,
3. Results and discussion
a = 10.375(1), b = 12.010(1) c = 12.683(1) Å,
a = 109.106(2),
b = 91.682(2),
c
= 109.104(2)°,
V = 1395 Å3.
Dc
(Z = 1) =
The diphosphine silver(I) methanesulfonate 1:1 adducts 1–5
were prepared by using equimolar quantities of the P^P-donor, in
alcoholic solvents under nitrogen in moderate yield. By using a
large excess of the diphosphine the 2:1 adducts 6–8 formed (Chart
1). The complexes were isolated as white solids. They are not sen-
sitive to moisture and temperature, and insoluble in non-polar sol-
vent like petroleum, whereas they are soluble in chlorinated
solvents and acetone.
Table 1
Selected geometries, 3.
Atoms
Parameter
Atoms
Parameter
Distances (Å)
Ag–P(1)
Ag–P(20)
Ag–O(1)
Ag–O(10)
Ag–O(2)
2.4170(8)
2.3885(7)
2.574(2)
2.866(2)
2.890(4)
S–O(1)
S–O(2)
S–O(3)
S–C(4)
Agꢀ ꢀ ꢀAg0
1.461(2)
1.451(3)
1.434(3)
1.772(5)
4.4514(4)
The IR spectra of all derivatives show a number of absorptions
in the 1300–1000 cmꢁ1 region, due to asymmetric and symmetric
vibrations of SO2 according to the literature and also a medium
absorption at ca. 1030 cmꢁ1 that can be assigned to the S–O vibra-
tion [15–17]. It is worth noting that the 1:1 adducts show a pattern
of absorptions different to that found in the 2:1 species in which
the O3SMe is likely ionic. For example, in 3, in which the sulfonate
is covalently bonded, the symmetric absorption is found at ca.
1180 cmꢁ1, whereas in 6 in which an ionic O3SMe is hypothesised,
we have detected two strong absorptions between 1210 and
Angles (°)
P(1)–Ag–P(20)
P(1)–Ag–O(1)
P(1)–Ag–O(10)
P(1)–Ag–O(2)
P(20)–Ag–O(1)
P(20)–Ag–O(10)
P(20)–Ag–O(2)
150.98(2)
99.22(5)
97.22(5)
85.47(6)
109.66(5)
90.02(5)
114.50(6)
Ag–O(1)–S
Ag–O(10)–S0
Ag–O(2)–S
O(1)–Ag–O(10)
O(1)–Ag–O(2)
O(10)–Ag–O(2)
Ag–O(1)–Ag
104.1(1)
146.2(1)
90.9(2)
70.27(8)
51.75(7)
121.43(7)
109.7(1)
1190 cmꢁ1
.
P^P ligand torsions (°)
Ag–P(1)–C(1)–C(0)
P(1)–C(1)–C(0)–C(2)
ꢁ57.5(2)
Ag–P(2)–C(2)–C(0)
P(2)–C(2)–C(0)–C(1)
51.3(2)
ꢁ163.1(2)
The conductivity values found for derivatives 1–5 in dichloro-
methane are higher than those found, for example, in analogous
halide and pseudohalide derivatives [18] and are suggestive of a
150.9(2)
Primed atoms are related by the intramolecular inversion centre.

C. Pettinari et al. / Inorganica Chimica Acta 362 (2009) 3225–3230
3229
partial dissociation in solution. We cannot exclude the occurrence
of equilibria such as Eq. (1), also taking into account that species
analogous to [Ag2(diphosphine)2(O3SMe)]+ [19] may be formed,
but on the basis of NMR spectra (see below) we suggest in solution
also the existence of the dissociation Eq. (2), so that both processes
indicated here may be present.
1J(107Ag)/1J(109Ag) ratio is in good agreement with that calculated
from the gyromagnetic ratio of the Ag nuclei [22]. The signal due
to each free phosphine is always up-field with respect to that of
the corresponding silver(I) complex. It has been suggested
[23,24] that the spin–spin constant (J) between phosphorus and
silver changes, depending on the number of coordinated phospho-
rus atoms in the silver complex, and that it is possible to determine
the number of the latter from measurement of the J values in the
31P NMR spectra. On this basis we hypothesised a AgP2O2 environ-
½Ag2ðdiphosphineÞ2ðO3SMeÞ2ꢃ¡
½Ag ðdiphosphineÞ ðO3SMeÞꢃþ þ ½O3SMeꢃꢁ
ð1Þ
ð2Þ
2
2
ment for 2–5 and AgP4 for 6–8 in solution. The low temperature 31
P
½Ag2ðdiphosphineÞ2ðO3SMeÞ2ꢃ¡
½AgðdiphosphineÞ2ꢃðO3SMeÞ þ AgO3SMe
spectra of the 1:1 species consist often of a sharper double doublet,
flanked by a less intense double doublet, characterized by similar
coupling constants, that can be ascribed to the existence of two
forms of the same species in solution and a second double doublet
that increases with the time analogous to that found in the spectra
of the 1:2 adducts 6–8 and that confirms the relevance of Eq. (2). A
double triplet and a broad signal have been found at room temper-
ature in the spectrum of 1 whereas the low temperature 31P spec-
trum consists of an AA0XX0AA0 pattern [25] due to the non-
equivalence of the phosphorus atoms (as emerges also from the
X-ray data) and resulting from the large 2J(P–P), for the three pos-
sible combinations of the two silver isotopes. The same pattern,
has been found by us also for other known [Ag2(dppm)2(X)2] spe-
cies, supporting a binuclear structure for 1 [26]. We have calcu-
lated the values of the coupling constants from the NMR spectral
data recorded at 223 K by applying the equations reported by
van der Ploeg and van Koten [27].
Eq. (2) is consistent with the fact that dissolution of derivatives 2–4
in dichloromethane always yields small quantities of corresponding
derivatives 6–8.
The occurrence of the Eqs. (1) and (2) is also supported by the
ESI MS spectra carried out in MeCN. In the positive mode, the spec-
tra of 1–4 exhibit peaks due the cationic species [Ag2Cl(diphos-
phine)2]+ and [Ag(diphosphine)2]+ consequent upon loss of
methanesulfonate counter-ions (with exception of 1 in which the
unique signal detectable is that due to [Ag2Cl(dppm)2]+ (Fig. 2a).
However, no fragments containing two positive charges have been
detected. In the ESI MS spectrum of 5 (positive mode) we have
found signals due to both mononuclear [Ag(dppf)+] and dinuclear
[Ag2(O3SMe)(dppf)]+ (Fig. 2b and no signal due to 2:1:2 complex
is present. In the spectra of the 1:2 adducts 6–8, the unique signal
detectable is that assignable to a [Ag(diphosphine)2]+ species, con-
firming a greater stability of these species in solution. It is worth
noting that addition of the corresponding diphosphine to solution
of 2–4, leads to an increase of the signals due to cationic
[Ag(diphosphine)2]+ species.
In the spectra of 2–4 also signals due to protonated oxidized
diphosphines can be identified (see for example (Fig. 2c), whereas
these signals are not present in the spectra of 6–8. These results
confirm at least the partial existence of the silver complexes 1–8
in solution, the 1:2 adducts 6–8 being, however, the most stable
species with respect to the dinuclear adducts 1–4. The negative
electrospray spectra are always dominated by the presence of
peaks due to [O3SMe]ꢁ, [Ag(O3SMe)2]ꢁ and also due to [AgCl2]ꢁ,
(the Clꢁ ion rising from the solvent).
Single crystal X-ray structure determinations of 3 and 4 show
similar binuclear forms (Fig. 1, Tables 1 and 2), exhibiting the
familiar [Ag(P^P)2Ag] binuclear unit, with the silver atoms further
bridged in these examples by a pair of sulfonate ligands. The
Agꢀ ꢀ ꢀAg distances differ (4.0614(3); 4.4512(4) Å, in keeping with
the increased n in the (CH2)n bridges of the P^P ligands, despite
the constraint of the bridging sulfonate groups. The latter are
essentially symmetrically
l
-OSO2CH3 bridging (Ag–O(1,10)
2.496(2), 2.509(2); Agꢀ ꢀ ꢀO(20) 3.109(3) Å) in 4 (Table 2), less sym-
metrical 2.574(2), 2.866(2) Å with invasive Agꢀ ꢀ ꢀO(2) interaction
(2.890(4) Å), impacting on the remainder of the coordination envi-
ronment of the silver atom in 3 (Table 1). Interestingly, despite the
lack of close Agꢀ ꢀ ꢀO(2) interaction in 4, the symmetrical bridging
interactions of O(1) may be considered sufficiently invasive to
diminish the P–Ag–P angle from 150.98(2) in 3 to 139.63(2)°, both
in turn considerably diminished relative to the value found in Ag-
ClO4:dppp (1:1)2 where, despite the feebly coordinating nature of
the anion, there still is a pronounced anionic bridging interaction
1H NMR spectra were recorded for all complexes and were con-
sistent with the stoichiometries of the complexes. The CH3 proton
of O3SMe falls in all complexes in the range 2.4–2.8 in accordance
with the value previously reported [20]. The bridging methylene
proton resonances in 1–7 appear as a broad singlet or multiplet be-
tween 1.8 and 2.60 ppm, shifted with respect to those found in the
free donors and confirming the existence, at least partial, of the
complexes in solution. The chemical shift of the methylene protons
in 1 can be used for the evaluation of the charge changes on the
coordinating P atoms. We have calculated the appropriate value
on the basis of the empirical relation of Grim and Walton [21]
X
Table 2
Selected geometries, 4.
Atoms
Parameter
Atoms
Parameter
Distances (Å)
Ag–P(1)
2.4316(5)
2.4175(5)
2.496(2)
2.509(2)
3.109(3)
S–O(1)
S–O(2)
S–O(3)
S–C(4)
Agꢀ ꢀ ꢀAg0
1.464(2)
1.451(2)
1.446(2)
1.772(2)
4.0617(4)
dCH ðppmÞ ¼ 1:57
qi þ 2:65 ðqi
2
Ag–P(20)
Ag–O(1)
¼ charge on the ith phosphorus nucleusÞ:
Ag–O(10)
Ag–O(20)
The obtained change of charge, 0.20, correlates well with the upper
frequency coordination shift in the 31P NMR spectrum of 1.
Angles (°)
P(1)–Ag–P(20)
P(1)–Ag–O(1)
P(1)–Ag–O(10)
P(20)–Ag–O(1)
P(20)–Ag–O(10)
139.63(2)
105.77(4)
93.04(5)
97.25(4)
125.97(4)
Ag–O(1)–S
139.34(9)
111.28(8)
71.48(5)
31P chemical shifts (CDCl3 solution) and 31P–Ag coupling con-
stants for derivatives 1–8, are reported in Section 2. The room tem-
perature 31P NMR spectra of the complexes consists generally of
unresolved broad doublets or multiplets. At low temperature
(218–223 K), two resolved pairs of doublets, arising from coupling
between the phosphorus and silver atoms, are observed in the
accessible temperature range. In particular, in the spectra of deriv-
atives 2–7 typical pairs of doublets, due to 131J(31P–107Ag) and
1J(31P–109Ag) coupling, are resolved at 218 K and the observed
Ag–O(10)–S0
O(1)–Ag–O(10)
Ag–O(1)–Ag0
108.52(5)
P^P ligand torsions (°)
Ag–P(1)–C(11)–C(12)
P(1)–C(11)–C(12)–C(22)
C(11)–C(12)–C(22)–C(21)
ꢁ57.2(1)
176.4(1)
ꢁ74.0(2)
Ag–P(2)–C(21)–C(22)
P(2)–C(21)–C(22)–C(12)
66.5(2)
ꢁ75.4(2)
Primed atoms are related by the intramolecular inversion centre.

3230
C. Pettinari et al. / Inorganica Chimica Acta 362 (2009) 3225–3230
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with (in two phases) P–Ag–P 157.40(2)–160.53(2)° with Ag–P
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