New structural features in triphenylphosphinesilver(I) sulfanylcarboxylates

Article abstract of DOI:10.1039/b501309g

We investigated the reactions of 1.5 : 1 : 1 mole ratio mixtures of triphenylphosphine, silver nitrate and 3-(aryl)-2-sulfanylpropenoic acids H ₂xspa in chloroform/water, where in the acid nomenclature, spa = 2-sulfanylpropenoato and x = p, Clp

Full text of DOI:10.1039/b501309g

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F U L L P A P E R
New structural features in triphenylphosphinesilver(I)
sulfanylcarboxylates†
Elena Barreiro,a Jose´ S. Casas,a Mar´ıa D. Couce,b Agust´ın Sa´nchez,a Jose´ Sordo,*a
Jose´ M. Varelaa and Ezequiel M. Va´zquez-Lo´pezb
a Departamento de Qu´ımica Inorga´nica, Facultade de Farmacia, Universidade de Santiago de
Compostela, 15782, Santiago de Compostela, Galicia, Spain
b Departamento de Qu´ımica Inorga´nica, Facultade de Ciencias, Universidade de Vigo, 36200,
Vigo, Galicia, Spain. E-mail: qijsordo@usc.es
Received 26th January 2005, Accepted 22nd March 2005
First published as an Advance Article on the web 11th April 2005
We investigated the reactions of 1.5 : 1 : 1 mole ratio mixtures of triphenylphosphine, silver nitrate and
3-(aryl)-2-sulfanylpropenoic acids H2xspa in chloroform/water, where in the acid nomenclature, spa =
2-sulfanylpropenoato and x = p, Clp, mp, diBr-o-hp or f with p = 3-phenyl-, Clp = 3-(2-chlorophenyl)-, mp =
3-methoxyphenyl-, diBr-o-hp = 3-(3,5-dibromo-2-hydroxyphenyl)- and f = 3-(2-furyl)-. The compounds
[Ag(PPh3)(Hpspa)](1), [(AgPPh3)2(xspa)] [x = Clp (2), o-mp (3), p-mp (4), diBr-o-hp (5) and f (6)] and
[Ag(PPh3)3(Hfspa)] (7) were isolated and all except 7 were characterized by IR, Raman and FAB mass spectrometry
and by 1H, 13C and 31P NMR spectroscopy. Compound 6 was also characterized by 13C CP/MAS, and compounds 1
and 6 by 109Ag NMR spectroscopy. The crystal structures of 1, 2, 3, 4·(CH3)2CO, 5, 6·(CH3)2CO and 7 were
determined by X-ray diffraction. 1 has a supramolecular structure based on hydrogen bonding between
dinuclear units, and all the other complexes adopt discrete structures. 2, 3, 4·(CH3)2CO, 5, and 6·(CH3)2CO are
tetranuclear, and 7 mononuclear. The tetranuclear complexes contain the eight-membered coordination ring Ag4S2O2
(2, 3, 4·(CH3)2CO, 6·(CH3)2CO) or the twelve-membered ring Ag4(CO2)2S2 (5).
Introduction
The biological and/or medicinal activities of the thiolate
complexes of Ag(I) and Au(I) have increased interest in the
coordination chemistry and structures of these compounds.1–6
Au(I) thiolates can have antiarthritic,1,7 antitumor1,3,8,9 and
antimicrobial activities,4,5a–e while the antibacterial effects of
silver compounds have long been known, and silver nitrate and
certain silver complexes are still used against local infections,
Nomiya et al.5f have shown that the key factors determining
the antimicrobial effects of silver complexes include the kind of
atom co-ordinated to the silver(I) atom and the ease with which
the ligand is exchanged with biologically relevant ligands.
A number of Au(I) complexes of types [Au(PPh3)(Hxspa)],
[HQ][Au(PPh3)(xspa)] and [(AuPPh3)2(xspa)] [HQ = diiso-
propylammonium; spa = 2-sulfanylpropenoato; x = f, t, p,
where f = 3-(2-furyl)-, t = 3-(2-thienyl)-, and p = 3-phenyl-]
were recently studied in our laboratories,10 and the structures
of other triphenylphosphinegold(I) sulfanylcarboxylates have
also received attention (see ref. 10). However, the only similar
compounds of silver(I) to have had their structures elucidated
Scheme 1
are, as far as we know, [Ag(PPh3)3(Hmna)]11 (H2mna = 2-sul-
fanylnicotinic acid), [Ag(PPh3)3 (Hmba)]12 (H2mba = 2-sulfanyl-
benzoic acid) and [H4Ag8(2-mpa)6(PPh3)6].EtOH (2-H2mpa =
in intra- or intermolecular interactions, and partly because of
their likely influence on the hydrophilicity and lipophilicity
of the complexes prepared, which are of great importance for
racemic 2-sulfanylpropionic acid).13 [Ag(PPh3)3(Hmna)]11
and [Ag(PPh3)3(Hmba)]12 are mononuclear, and [H4Ag8(2-
mpa)6(PPh3)6].EtOH13 is octanuclear; all three have Ag–S and
their pharmaceutical activity.1,14,15 This paper describes the
Ag–P bonds but no Ag-carboxylate bonds.
structures of [(AgPPh3)(Hpspa)] (1), [(AgPPh3)2(Clpspa)] (2),
We have now prepared triphenylphosphinesilver(I) complexes
of the 3-(aryl)-2-sulfanylpropenoic acids depicted in Scheme 1.
The R groups of these acids were chosen partly to allow com-
parison of the structures of Ag(I) and Au(I) compounds with the
[(AgPPh3)2(o-mpspa)] (3), [(AgPPh3)2(p-mpspa)]·(CH3)2CO
(4·(CH3)2CO), [(AgPPh3)2(diBr-o-hpspa)] (5), [(AgPPh3)2-
(fspa)]·(CH3)2CO (6·(CH3)2CO) and [Ag(PPh3)3(Hfspa)] (7)
where Clp = 3-(2-chlorophenyl), mp = 3-methoxyphenyl, diBr-
same ligands, partly because of the possibility of their engaging
o-hp = 3-(3,5-dibromo-2-hydroxyphenyl) and f = 3-(2-furyl).
1 has a supramolecular structure, based on hydrogen bonding
between dinuclear units, and all the other complexes adopt
† Electronic supplementary information (ESI) available: Molecular
discrete structures; 2, 3, 4·(CH3)2CO, 5, and 6·(CH3)2CO are
structures of [(AgPPh3)2(o-mpspa)] (3), [(AgPPh3)2(p-mpspa)] (4),
[(AgPPh3)2(fspa)] (6). 109Ag NMR spectra of 6 and 1 (Figs. S1–S4).
tetranuclear and 7 mononuclear. The tetranuclear complexes
See http://www.rsc.org/suppdata/dt/b5/b501309g/
contain the unprecedented eight-membered coordination
T h i s j o u r n a l i s
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5
D a l t o n T r a n s . , 2 0 0 5 , 1 7 0 7 – 1 7 1 5
1 7 0 7
©

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ring Ag4S2O2 (2, 3, 4·(CH3)2CO, 6·(CH3)2CO) or the twelve-
membered ring Ag4(CO2)2S2 (5).
H2Clpspa. Rod-Clpspa (2.55 g, 10 mmol), 2 M NaOH
(50 cm3), 2 M HCl (50 cm3), beige solid. Yield: 81%. Mp: 110◦
C. Anal. found, C 50.4. H 3.2, S 14.7%; calc. for C9H7O2SCl, C
−1
=
50.4, H 3.3, S 14.9%. IR and Raman (R) (cm ): 1638vs, m(C O);
Experimental
1437m, d(OH); 1259s, m(C–O); 2561m 2564m (R), m(S–H). NMR
(dmso-d6): H, d 13.30 (w, 1H, C(1)OH), 7.933 (s, 1H, C(3)H)
1
Material and methods
and 7.37 (m, 4H, C(6)H, C(7)H, C(8)H, C(9)H). NMR (CDCl3):
1H, d 9.49 (w, 1H, C(1)OH), 4.46 (s, 1H, C(2)SH), 8.14 (s, 1H,
C(3)H), 7.46 (d, 1H, C(6)H), 7.34 (m, 2H, C(7)H, C(8)H) and
7.82 (d, 1H, C(9)H);13C, d 170.6 C(1), 125.5 C(2), 135.1 C(3),
134.6 C(4), 1343.5 C(5), 130.3 C(6), 130.8 C(7), 127.7 C(8) and
130.1 C(9).
2-Chlorobenzaldehyde, 2-methoxybenzaldehyde, 4-methoxy-
benzaldehyde,
3,5-dibromo-2-hydroxybenzaldehyde
and
furfural-2-carboxaldehyde (all from Aldrich), benzaldehyde
(Probus), triphenylphosphine (Riedel-de-Hae¨n) and silver
nitrate (Prolabo) were all used as supplied.
Elemental analyses were performed with a Fisons 1108
microanalyser. Melting points were determined with a Bu¨chi
apparatus and are uncorrected. Mass spectra were recorded on
a Kratos MS50TC spectrometer connected to a DS90 system
and operating in FAB mode (m-nitrobenzyl alcohol, Xe, 8 eV;
ca. 1.28 × 10−15 J); ions were identified by DS90 software and
the data characterizing the metallated peaks were calculated
assuming the Ag isotope to be 107Ag. IR spectra (KBr pellets or
Nujol mulls) and Raman spectra (polycrystalline samples) were
recorded on a Bruker IFS66V FT-IR spectrometer equipped
with an FRA-106 Raman accessory, and are reported in the
synthesis section using the following abbreviations: vs = very
strong, s = strong, m = medium, w = weak, sh = shoulder,
br = broad. 1H and 13C NMR spectra in solution were recorded
in dmso-d6 or CDCl3 at room temperature on a Bruker AMX
300 operating at 300.14 (1H) and 75.40 MHz (13C), using 5 mm
o.d. tubes; chemical shifts are reported relative to TMS using
H2-o-mpspa. Rod-o-mpspa (2.51 g, 10 mmol), 1 M NaOH
(50 cm3), 1 M HCl (50 cm3), yellow solid. Yield: 49%. Mp: 130◦
C. Anal. found, C 56.5, H 4.6, S 15.7%; calc. for C10H10O3S, C
−1
=
57.1, H 4.8, S 15.2%. IR and Raman (R) (cm ): 1664vs, m(C O);
1481s, d(OH); 1282vs, m(C–O); 2560m 2561w (R), m(S–H). NMR
(dmso-d6): H, d 13.00 (w, 1H, C(1)OH), 7.92 (s, 1H, C(3)H),
1
7.70 (d, 1H, C(6)H), 7.02 (t, 1H, C(7)H) 7.40 (t, 1H, C(8)H) 7.08
(d, 1H, C(9)H) and 3.82 (s, 3H, OCH3); 13C, d 166.2 C(1), 128.9
C(2), 139.5 C(3), 119.9 C(4), 157.6 C(5), 111.1 C(6), 131.6 C(7),
122.4 C(8), 130.4 C(9) and 55.6 C(OCH3).
H2-p-mpspa. Rod-p-mpspa (2.51 g, 10 mmol), 1 M NaOH
(50 cm3), 1 M HCl (50 cm3), orange solid. Yield: 67%. Mp: 160◦
C. Anal. found, C 56.9, H 5.1, S 15.0%; calc. for C10H10O3S:
C 57.1, H 4.8, S 15.2%. IR and Raman (R) (cm−1): 1662vs,
=
m(C O); 1427m, d(OH); 1259vs, m(C–O); 2570m 2570w (R), m(S–
H). NMR (dmso-d6): 1H, d 12.90 (w, 1H, C(1)OH), 7.90 (s, 1H,
C(3)H), 7.82 (d, 2H, C(5)H, C(9)H), 6.94 (d, 2H, C(6)H, C(8)H)
and 3.79 (s, 3H, OCH3); 13C, d 166.7 C(1), 125.3 C(2), 145.0 C(3),
126.4 C(4), 133.2 C(5), C(9), 113.9 C(6), C(8), 160.8 C(7) and
55.4 C(OCH3).
1
the solvent signal (d H = 2.50 ppm; d 13C = 39.50 ppm or d
1H = 7.26 ppm; d 13C = 77.00 ppm) as reference. 1H–1H COSY
NMR spectra were recorded, and 1H–13C HMBC (heteronuclear
multiple bond correlation) and HMQC (heteronuclear multiple
quantum coherence) experiments were performed, using a
Varian Inova 400 spectrometer. 31P NMR spectra were recorded
at 202.46 MHz on a Bruker AMX 500 spectrometer using 5 mm
od tubes, and are reported relative to external H3PO4 (85%).
H2-diBr-o-hpspa. Rod-diBr-o-hpspa (3.79 g, 10 mmol), 1 M
NaOH (50 cm3), 1M HCl (50 cm3), beige solid. Yield: 95%.
Mp: 120◦ C. Anal. found, C 30.7, H 1.5, S 8.8%; calc. for
C9H6O3SBr2: C 31.9, H 1.8, S 9.4%. IR and Raman (R) (cm−1):
1
Since the ligands rapidly decompose in dmso-d6, H and 13C
=
1682vs, m(C O); 1449s, d(OH); 1278vs, m(C–O); 2565m 2565w
(R), m(S–H). NMR (dmso-d6): H, d 11.39 (w, 1H, C(1)OH),
NMR data were obtained from freshly prepared concentrated
solutions.
1
10.06 (s, 1H, C(3)H) 9.86 (w, 1H, C(5)OH), 8.07 (d, 1H, C(7)H)
and 7.88 (d, 1H, C(9)H);13C, d 169.3 C(1), − C(2), − C(3), 124.2
C(4), 155.9 C(5), 111.2 C(6), 140.4 C(7), 113.3 C(8) and 132.9
Solid-state 13C (75.40 MHz) spectra were recorded at room
temperature using a Bruker AMX 300 spectrometer equipped
with a CP/MAS (cross-polarization magic angle spinning)
accessory. Samples were packed in 7 mm Zirconia rotors and
spun at 3.0 and 4.0 kHz at the “magic” angle. 109Ag NMR spectra
were acquired at 23.27 MHz from solutions in a 4 : 1 mixture
of dmso and dmso-d6 in 10 mm od tubes in a Bruker AMX500
apparatus, and were referenced by the substitution method using
a 4M solution of AgNO3 in D2O (d = 0) as standard.
1
C(9). NMR (CDCl3): H, d 9.81 (s, 1H, C(3)H), 11.51 (s, 1H,
C(5)OH), 7.91 (d, 1H, C(7)H) and 7.67 (d, 1H, C(9)H);13C, d −
C(1), 118.3 C(2), − C(3), 121.9 C(4), 157.3 C(5), 112.5 C(6),
142.0 C(7), 111.4 C(8) and 134.9 C(9).
H2fspa. Rod-fspa (2.11 g, 10 mmol), 1 M NaOH (50 cm3),
1 M HCl (50 cm3), light brown solid. Yield: 64%. Mp: 109◦
C. Anal. found, C 49.1, H 3.7, S 18.9%; calc. for C7H6O3S: C
−1
=
49.4, H 3.5, S 18.8%. IR (R) (cm ): 1673vs, m(C O); 1417s,
Synthesis
d(OH); 1266s, m(C–O); 2568m, m(S–H). NMR (dmso-d6): 1H, d
12.82 (w, 1H, C(1)OH), 7.60 (s, 1H, C(3)H), 7.22 (d, 1H, C(5)H),
6.67 (t, 1H, C(6)H) and 7.87 (d, 1H, C(7)H); 13C, d 166.4 C(1),
124.5 C(2), 132.0 C(3), 149.9 C(4), 118.8 C(5), 113.4 C(6) and
146.8 C(7). NMR (CDCl3):1H, d 4.71 (s, 1H, C(2)SH), 7.75 (s,
1H, C(3)H), 6.90 (d, 1H, C(5)H), 6.58 (t, 1H, C(6)H) and 7.67
(d, 1H, C(7)H); 13C, d 170.5 C(1), 118.8 C(2), 124.3 C(3), 150.7
C(4), 116.4 C(5), 112.7 C(6) and 144.7 C(7).
The 3-(Aryl)-2-sulfanylpropenoic acids H2pspa, H2Clpspa,
H2-o-mpspa, H2-p-mpspa, H2-diBr-o-hpspa and H2fspa were
prepared16 by condensation of the appropriate aldehyde with
rhodanine, subsequent alkaline hydrolysis of the 5-substituted
rhodanines so obtained (Rod-pspa, Rod-Clpspa, Rod-o-mpspa,
Rod-p-mpspa, Rod-diBr-o-hpspa and Rod-fspa), and acidifica-
tion with aqueous HCl.
Complexes 1–6 were prepared as follows. A solution of the
appropriate sulfanylcarboxylic acid and a 56% excess of
triphenylphosphine in chloroform was added to a solution
of silver nitrate and NaOAc in water, and the mixture was shaken
for 20 min. The organic phase was separated using a separation
funnel, dried with MgSO4, and the CHCl3 was evaporated
under vacuum. The crude oily product was treated with 1 : 1
hexane/ethanol, and the resulting solid was dried in vacuo and
crystallized from acetone. Crystals of 7 were obtained from the
mother liquor (hexane/ethanol) of 6. Only in the case of the
p-mpspa derivative did a molecule of (CH3)2CO co-crystallize
H2pspa. Rod-pspa (2.21 g, 10 mmol), 1M NaOH (50 cm3),
1 M HCl (50 cm3), yellow solid. Yield: 70%. Mp: 123◦ C. Anal.
found, C 59.4, H 4.4, S 17.5%; calc. for C9H8O2S, C 60.0,
−1
=
H 4.4, S 17.8%. IR and Raman (R) (cm ): 1670vs, m(C O);
1416s, d(OH); 1266vs, m(C–O); 2567m 2570w (R), m(S–H). NMR
(dmso-d6): 1H, d 12.6 (w, 1H, C(1)OH), 5.22 (vw, 1H, C(2)SH),
7.73 (s, 1H, C(3)H), 7.68 (d, 2H, C(5)H, C(9)H), 7.47 (t, 2H,
C(6)H, C(8)H) and 7.39 (m, 1H, C(7)H); 13C, d 167.1 C(1), 129.5
C(2), 145.6 C(3), 134.4 C(4), 131.3 C(5), C(9), 129.4 C(6), C(8)
and 130.8 C(7).
1 7 0 8
D a l t o n T r a n s . , 2 0 0 5 , 1 7 0 7 – 1 7 1 5

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upon initial crystallization although this co-crystallization pro-
cess also occurred with 6 upon recrystallization from the same
solvent.
[(AgPPh3)2(diBr-o-hpspa)] (5). H2-diBr-o-hpspa (0.50 g,
1.5 mmol), PPh3 (1.25 g,4.8 mmol), AgNO3 (0.25 g, 1.5 mmol),
NaOAc (0.0.40 g, 4.9 mmol), CHCl3 (33 cm3), H2O (66 cm3),
white crystals. Yield: 50%. Mp: 190 ◦C. Anal. found, C 50.7,
H 3.6, S 2.4%; calc. for C45H34O3SP2Ag2Br2, C 50.1, H 3.2,
S 3.0%. MS (FAB): the main metallated signals are at m/z
1462 (3%), [(AgPPh3)3-diBr-o-hpspa]+; 1092 (12), [M]+; 631
(84), [(PPh3)2Ag]+; 369 (100), [(PPh3)Ag]+. IR (cm−1): 1556s,
mas(COO); 1349s, msym(COO); Dm 207; 1480m, 1434vs, m(Ph3P).
NMR (dmso-d6): 1H, d 9.98 (s, 1H, C(3)H), 8.73 (w, 1H,
C(5)OH), 7.79 (s, 1H, C(7)H), 7.14–7.61 (m, 31H, C(9)H,
H(PPh3));13C, d − C(1), − C(2), − C(3), 122.0 C(4), 159.6 C(5),
112.6 C(6), 138.4 C(7), 109.8 C(8), 135.5 C(9), 133.3 (d, Co(Ph3),
[(AgPPh3)(Hpspa)] (1). H2pspa (0.74 g, 4.2 mmol), PPh3
(1.71 g, 6.5 mmol), AgNO3 (0.71 g, 4.2 mmol), NaOAc (0.57 g,
6.9 mmol), CHCl3 (33 cm3), H2O (66 cm3), yellow crystals.
◦
Yield: 45%. Mp: 155 C. Anal. Found, C 58.8, H 4.1, S 5.6%;
calc. for C27H22O2SPAg, C 59.0, H 4.0, S 5.8%. MS (FAB): the
main metallated signals are at m/z 918(14%), [(AgPPh3)2pspa]+;
631(46), [(PPh3)2Ag]+; 369(100), [(PPh3)Ag]+. IR (cm−1): 1637vs,
=
m(C O); 1435s, d(OH); 1252s, m(C–O); 1479m, 1435s, m(PPh3).
NMR (dmso-d6): H, d 12.56 (w, 1H, C(1)OH), 7.54 (s, 1H,
1
1
C(3)H), 8.20 (d, 2H, C(5)H, C(9)H), 7.25 (t, 2H, C(6)H, C(8)H),
7.19–7.41 (m, 16H, C(7)H, H(PPh3)); 13C, d 171.0 C(1), − C(2),
136.5 C(3), 136.2 C(4), 130.2 C(5), 127.5 C(6), 127.3 C(7), 132.0
(d, Ci(Ph3), J = 26.4), 133.2 (d, Co(Ph3), J = 17.3), 128.7 (d,
J = 16.8), 128.8 (d, Cm(Ph3), J = 9.2), 130.1 Cp(Ph3); 31P { H}:
1
d 7.0 (s), 29.6 (s). NMR (CDCl3): H, d 9.87 (s, 1H, C(3)H),
6.78 (w, 1H, C(5)OH), 7.84 (d, 1H, C(7)H), 7.10 (d, 1H, C(9)H),
1
7.19–7.79 (m, 30H, H(PPh3));31P { H}: d 2.4 (s), 28.4 (s).
1
Cm(Ph3), J = 9.5), 130.1 Cp(Ph3); 31P { H}: d 11.3 (s). 109Ag
[(AgPPh3)2(fspa)] (6). H2fspa (0.76 g, 4.5 mmol), PPh3
(1.85 g, 7.0 mmol), AgNO3 (0.76 g, 4.5 mmol), NaOAc (0.60 g,
7.3 mmol), CHCl3 (33 cm3), H2O (66 cm3), orange crystals. Yield:
43%. Mp: 170◦ C. Anal. found, C 55.4, H 3.8, S 3.8%; calc. for
C43H34O3SP2Ag2, C 56.8, H 3.7, S 3.5%. MS (FAB): the main
metallated signals are at m/z 1278 (2%), [(AgPPh3)3fspa]+; 909
(18), [M]+; 631 (100), [(PPh3)2Ag]+; 369 (65), [(PPh3)Ag]+. IR
(cm−1): 1562m, mas(COO); 1479s, 1435s, m(Ph3P). NMR (dmso-
d6): 1H, d 7.44 (s, 1H, C(3)H), 7.59 (d, 1H, C(5)H), 6.42 (m, 1H,
C(6)H), 7.61 (d, 1H, C(7)H), 7.20–7.43 (m, 30H, H(PPh3));13C,
d 170.2 C(1), 122.2 C(2), 128.6 C(3), 153.4 C(4), 112.9 C(5),
111.9 C(6), 142.0 C(7), 132.5 (d, Ci(Ph3), J = 20.7), 133.2 (d,
Co(Ph3), J = 17.2), 128.7 (d, Cm(Ph3), J = 9.2), 129.9 Cp(Ph3);
NMR (dmso/dmso-d6): d 936.3 (s).
[(AgPPh3)2(Clpspa)] (2). H2Clpspa (0.71 g, 3.3 mmol), PPh3
(1.36 g, 5.13 mmol), AgNO3 (0.56 g, 3.3 mmol), NaOAc
(0.90 g, 10.9 mmol), CHCl3 (◦33 cm3), H2O (66 cm3), golden
crystals. Yield: 45%. Mp: 200 C. Anal. found, C 56.4, H 3.7,
S 3.0%; calc. for C45H35O2SP2Ag2Cl, C 56.6, H 3.7, S 3.4%.
MS (FAB): the main metallated signals are at m/z 1322 (3%),
[(AgPPh3)3Clpspa]+; 953 (11), [M]+; 631 (100), [(PPh3)2Ag]+;
369 (91), [(PPh3)Ag]+. IR (cm−1):1533vs, mas(COO); 1354vs,
msym(COO); Dm 179; 1475vs, 1433vs, m(Ph3P). NMR (dmso-d6):
1H, d 7.85 (s, 1H, C(3)H), 7.54 (d, 1H, C(6)H), 7.15 (t, 1H,
C(7)H), 7.61 (m, 1H, C(8)H), 9.42 (d, 1H, C(9)H), 7.19–7.42
(m, 30H, H(PPh3));13C, d 171.4 C(1), 125.4 C(2), 135.5 C(3),
142.7 C(4), 132.7 C(5), 128.6 C(6), 131.4 C(7), 125.8 C(8), 127.7
C(9) 133.2 (d, Co(Ph3), J = 17.5), 128.8 (d, Cm(Ph3), J = 8.2),
1
1
31P { H}: d 10.2 (s), 29.8 (s). NMR (CDCl3): H, d 7.62 (s,
1H, C(3)H), 7.44 (d, 1H, C(5)H), 6.14 (t, 1H, C(6)H), 7.58
(d, 1H, C(7)H), 7), 7.16–7.54 (m, 30H, H(PPh3));13C, d 169.2
C(1), 123.7 C(2), 128.4 C(3), 154.8 C(4), 112.6 C(5), 111.5 C(6),
141.7 C(7), 132.9 (d, Ci(Ph3), J = 18.2), 133.5 (d, Co(Ph3), J =
1
129.8 Cp(Ph3); 31P { H}: d 6.9(s), 29.5 (s). NMR (CDCl3): 1H, d
8.10 (s, 1H, C(3)H), 7.67 (m, 1H, C(6)H), 6.95 (m, 1H, C(7)H),
6.66 (m, 1H, C(8)H), 9.10 (d, 1H, C(9)H), 7.17–7.34 (m, 30H,
H(PPh3));13C, d 168.6 C(1), 125.4 C(2), 133.2 C(3), 138.5 C(4),
135.7 C(5), 129.1 C(6), 130.1 C(7), 127.7 C(8), 128.3 C(9), 133.2
(d, Ci(Ph3), J = 15.5), 133.6 (d, Co(Ph3), J = 17.0), 128.7 (d,
1
18.4), 128.8 (d, Cm(Ph3), J = 9.2), 129.7 Cp(Ph3); 31P { H}: d 5.2
(s), 28.5 (s). Solid NMR 13C, d 167.9 C(1), 123.3 C(2), − C(3),
155.2 C(4), 112.8 C(5), 112.0 C(6), 139.8 C(7), 136.4, 133.6,
132.6, 129.7 C(Ph3). 109Ag NMR (dmso/dmso-d6): d 1033.4
(s). After separating the initial batch of 6 a small number of
single crystals of [Ag(PPh3)3(Hfspa)] (7) were obtained at room
temperature from the mother liquor (ethanol/hexane). Crystals
of 6·(CH3)2CO suitable for X-ray diffractometry were obtained
upon recrystallization of 6 from acetone.
1
Cm(Ph3), J = 8.8), 129.7 Cp(Ph3); 31P { H}: d 3.7 (s), 28.4 (s).
[(AgPPh3)2(o-mpspa)] (3). H2-o-mpspa (0.50 g, 2.4 mmol),
PPh3 (0.98 g, 3.7 mmol), AgNO3 (0.41 g, 2.4 mmol), NaOAc
(0.48 g, 3.9 mmol), CHCl3 (33 cm3), H2O (66 cm3), orange
crystals. Yield: 37%. Mp: 185 ◦C. Anal. found, C 59.6, H
4.0, S 3.8%; calc. for C46H38O3SP2Ag2, C 58.2, H 4.0, S 3.4%.
MS (FAB): the main metallated signals are at m/z 1317 (1%),
[(AgPPh3)3-o-mpspa]+; 948 (26), [M]+; 631 (54), [(PPh3)2Ag]+;
369 (100), [(PPh3)Ag]+. IR (cm−1): 1534vs, mas(COO); 1350vs,
msym(COO); Dm 184; 1475m, 1433s, m(Ph3P). NMR (dmso-d6): 1H,
d 7.93 (s, 1H, C(3)H), 8.99 (d, 1H, C(6)H), 6.67 (t, 1H, C(7)H),
6.88 (d, 1H, C(9)H), 3.69 (s, 3H, OCH3), 7.20–7.60 (m, 31H,
C(8)H, H(PPh3));13C, d 171.8 C(1), 128.2 C(2), 133.2 C(3), 125.8
C(4), 156.7 C(5), 110.2 C(6), 129.4 C(7), 119.1 C(8), 128.5 C(9),
55.3 C(OCH3), 133.1 (d, Ci(Ph3), J = 21.3), 133.1 (d, Co(Ph3),
Crystallography
X-Ray data collection and reduction. Single crystals of
[(AgPPh3)(Hpspa)] (1), [(AgPPh3)2(Clpspa)] (2), [(AgPPh3)2(o-
mpspa)] (3), [(AgPPh3)2(p-mpspa)]·(CH3)2CO (4·(CH3)2CO),
[(AgPPh3)2(diBr-o-hpspa)] (5), [(AgPPh3)2(fspa)]·(CH3)2CO
(6·(CH3)2CO) and [Ag(PPh3)3(Hfspa)] (7) were mounted on
glass fibres in a Bruker Smart CCD automatic diffractometer.
Data were collected at 293 K using Mo Ka radiation (k =
17a
˚
0.71073 A). Corrections for Lorentz effects, polarization and
absorption17b were made. Table 1 summarizes the crystal data,
experimental details and refinement results.
1
J = 17.2), 128.7 (d, Cm(Ph3), J = 9.2), 130.1 Cp(Ph3); 31P { H}:
d 11.0 (s), 29.6 (s).
Structure analyses were carried out by direct methods.17c
Least-squares full-matrix refinements on F2 were performed
using the program SHELXL97. Atomic scattering factors and
anomalous dispersion corrections for all atoms were taken
from ref. 17d. Reflection data for 4·(CH3)2CO and 6·(CH3)2CO
were corrected for the diffuse scattering due to disordered
solvent molecules by means of the program SQUEEZE.17e All
non-hydrogen atoms were refined anisotropically, although in
4·(CH3)2CO the same anisotropic factor was used for all the
carbon atoms of one of the triphenylphosphine phenyl rings
(C121–C126). Hydrogen atoms were refined as riders. Graphics
were obtained with PLATON.18
[(AgPPh3)2(p-mpspa)]·(CH3)2CO (4·(CH3)2CO). H2-p-mpspa
(0.75 g, 3.6 mmol), PPh3 (1.47 g, 5.6 mmol), AgNO3 (0.61 g,
3.6 mmol), NaOAc (0.48 g, 5.9 mmol), CHCl3 (33 cm3), H2O
(66 cm3), yellow crystals. Yield: 38%. Mp: 195 ◦C. Anal. found,
C 57.9, H 4.2, S 3.3%; calc. for C49H44O4SP2Ag2, C 58.0, H
4.5, S 3.2%. MS (FAB): the main metallated signals are at m/z
948 (26%), [M]+; 631 (54), [(PPh3)2Ag]+; 369 (100), [(PPh3)Ag]+.
IR (cm−1): 1534vs, mas(COO); 1354, msym(COO); Dm 182; 1479s,
1
1435vs, m(Ph3P). NMR (dmso-d6): H, d 7.57 (s, 1H, C(3)H),
8.00 (d, 2H, C(5)H), 6.80 (d, 2H, C(6)H), 3.70 (s, 3H, OCH3),
7.03–7.63 (m, 31H, C(3)H, H(PPh3)).
CCDC reference numbers 261747–261753.
D a l t o n T r a n s . , 2 0 0 5 , 1 7 0 7 – 1 7 1 5
1 7 0 9

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1 7 1 0
D a l t o n T r a n s . , 2 0 0 5 , 1 7 0 7 – 1 7 1 5

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See http://www.rsc.org/suppdata/dt/b5/b501309g/ for cry-
stallographic data in CIF or other electronic format.
The S atoms both bridge asymmetrically between the two
˚
˚
silver(I) ions [Ag–S = 2.429(2) A, Ag–S#1 = 2.849(3) A],
forming a planar Ag2S2 core. Each silver(I) is four-coordinated in
a distorted tetrahedral AgS2OP environment, being bound to the
two S atoms, the triphenylphosphine P atom [Ag–P = 2.369(3)
Results and discussion
˚
˚
A] and one of the carboxylate O atoms [Ag–O(1) = 2.599(6) A].
The Ag–O(1) distance is at the upper end of the range of Ag–O
distances in tetrahedral environments,20 and is thus indicative of
a weak interaction. The coordination of this O atom leads to
the formation of an essentially planar AgC2SO five-membered
We initially attempted to prepare the complexes by reacting
AgPh3NO3 and alkaline H2xspa in 1 : 1 or 2 : 1 mole ratio, i.e.
by the same procedure as previously described10 for analogous
Au(I) complexes. Hovewer, even after tedious purification steps,
this method only afforded pure compounds in the case of the 2
: 1 complexes, and even these were non-crystalline. We therefore
tried reacting silver nitrate, phosphine and sulfanylcarboxylate
under heterogeneous conditions, as described by Becker et al.19
This afforded the 1 : 1 : 1 silver–phosphine–sulfanylcarboxylate
complex 1 and the 2 : 2 : 1 complexes 2–6, and the mother liquor
of 6 also afforded the 1 : 3 : 1 complex 7. This stoichiometric
variety suggests that several species are present in the reaction
media, the species isolated being determined by their relative
solubilities. The coexistence of several species with a different
PPh3 contents has previously been observed by Nomiya et al.11
in solutions of the Ag(I) compounds of 2-sulfanylnicotinic acid.
The presence in the FAB+ mass spectra of signals for both the
[M]+ peak and fragments with different PPh3 contents suggests
easy cleavage of Ag–P bonds, and cleavage of Ag–S bonds is also
evident.
˚
chelate ring. The Ag1 · · · Ag#1 distance, 3.1283(19) A, although
˚
longer than in metallic silver [2.889(6) A] is shorter than twice
21
˚
the van der Waals radius of this metal (3.44 A), and shorter
22
˚
than the 3.1300(3) A found in {[Ag(PPh3)(SPh)]4}, in which it
has been argued that there is a significant bonding interaction
between the Ag(I) centres.
The dinuclear units are associated in chains by hydrogen
bonds between their carboxy groups (Fig. 2), and the weakness
of the Ag–O bond is corroborated by the geometric parameter◦s
˚
of both these bonds [0.872(5), 1.789(6), 2.661(8) A, 177.6(5)
=
for O(2)–H(2). . .O(1)#2] and the CO2H group (C O = 1.21–
ranges.23
˚
˚
1.25 A, C–OH = 1.31–1.35 A) being within their normal
Solid state studies
[Ag(PPh3)(Hpspa)] (1). Single crystals obtained by slow
concentration of an acetone solution of [Ag(PPh3)(Hpspa)] were
composed of [Ag(PPh3)(Hpspa)]2 units which can be seen as
formed by Ag(PPh3)(Hpspa) monomers connected by Ag–S
bonds, the metal atom in each monomer being O,S-chelated.
Fig. 1 shows this structure, and the most significant structural
parameters are listed in Table 2.
Fig. 2 Hydrogen bonding in [Ag(PPh3)(Hpspa)] (1).
24
Both the structure of 1 and that of [Ag(pyOS)(PPh3)]2
(H2pyOS = 1-hydroxypyridine-2-thione) are based on an Ag2S2
core in which each Ag atom acquires a distorted tetrahedral
geometry by co-ordinating to one oxygen, two sulfurs and one
phosphorus. The Ag2S2 core of 1 is slightly broader and slightly
less skewed than that of [Ag(pyOS)(PPh3)]2, in which the Ag–
◦
˚
Fig. 1 Molecular structure of [Ag(PPh3)(Hpspa)] (1) (for clarity,
triphenylphosphine phenyl rings are represented by their P-bound ipso
carbons).
S distances are 2.057(1) and 2.822(1) A, Ag–S–Ag 74.8(1)
and S–Ag–S 105.2(1)◦. Like 1, however, [Ag(pyOS)(PPh3)]2
has a weak interaction between the two silver ions [Ag · · · Ag
˚
3.248(1) A]. Perhaps the most significant difference between the
Table 2 Selected interatomic distances (A) and angles (◦) in
˚
two compounds is that whereas the dinuclear units of the 1-
hydroxypyridine-2-thione derivative are isolated, those of 1 are
linked in chains by hydrogen bonds.
[Ag(PPh3)(Hpspa)] (1)
(a) Ag environment
The structural differences between 1 and the stoichiomet-
rically similar triphenylphosphinegold(I) sulfanylpropenoato
[Au(PPh3)(Hfspa)]10 are more marked. Although both have
similar M–S and M–P bond lengths, the monomers of the
gold compound are not linked in dimers by M–S coordinate
bonds but by p-stacking between triphenylphosphine phenyl
rings and by hydrogen bonds between the CO2H groups, which
are, accordingly, not available for polymerizing interactions.
Additionally, the M–O bond is shorter in Ag(I), which narrows
the S–M–P angle.
Ag–P
Ag–S
Ag–O(1)
Ag–S#1
Ag–Ag#1
2.369(3)
2.429(2)
2.599(6)
2.849(3)
3.1283(19)
P–Ag–S
149.83(9)
112.97(16)
74.12(15)
97.73(9)
107.80(7)
108.69(16)
72.19(7)
P–Ag–O(1)
S–Ag–O(1)
P–Ag–S#1
S–Ag–S#1
O(1)–Ag–S#1
Ag–S–Ag#1
(b) Hpspa
O(1)–C(1)
O(2)–C(1)
C(1)–C(2)
C(2)–C(3)
C(3)–C(4)
1.241(9)
1.302(9)
1.496(11)
1.349(10)
1.442(10)
O(1)–C(1)–O(2)
O(1)–C(1)–C(2)
O(2)–C(1)–C(2)
C(3)–C(2)–C(1)
C(3)–C(2)–S
121.0(10)
121.9(9)
117.1(9)
115.6(9)
125.5(7)
118.7(7)
In keeping with deprotonation of S and with the CO2H
group hydrogen bonding shown by the X-ray study, the IR and
Raman spectra of [Ag(PPh3)(Hpspa)] do not show the m(SH)
C(1)–C(2)–S
D a l t o n T r a n s . , 2 0 0 5 , 1 7 0 7 – 1 7 1 5
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Table 3 Selected interatomic distances (A) and angles (◦) in
˚
[Ag(PPh3)3(Hfspa)] (7)
(a) Ag environment
Ag–P(2)
Ag–P(1)
Ag–P(3)
Ag–S
Ag–O(1)
Ag–O(2)
2.5505(9)
2.5597(8)
2.6120(9)
2.6179(9)
3.997(3)
5.140(3)
P(2)–Ag–P(1)
P(2)–Ag–P(3)
P(1)–Ag–P(3)
P(2)–Ag–S
P(1)–Ag–S
P(3)–Ag–S
110.52(3)
114.96(3)
104.76(3)
116.23(3)
103.68(3)
105.50(3)
(b) Hfspa
O(1)–C(1)
O(2)–C(1)
C(1)–C(2)
C(2)–C(3)
C(3)–C(4)
1.318(5)
1.203(5)
1.506(6)
1.339(5)
1.435(6)
O(1)–C(1)–O(2)
O(1)–C(1)–C(2)
O(2)–C(1)–C(2)
C(3)–C(2)–C(1)
C(3)–C(2)–S
120.6(5)
115.9(4)
123.5(5)
117.2(4)
126.9(3)
115.9(3)
C(1)–C(2)–S
band located at 2567 cm−1 in the spectrum of H2pspa, and the
vibrations of the CO2H group are slightly shifted from their
Fig. 4 Molecular structure of [(AgPPh3)2(Clpspa)] (2) (for clarity,
hydrogen atoms have been omitted and triphenylphosphine phenyl rings
are represented by their P-bound carbons).
=
positions in the latter spectrum [1670, m(C O); 1416, d(OH);
1266, m(C–O)].
[Ag(PPh3)3(Hfspa)] (7). Single crystals of [Ag(PPh3)3-
(Hfspa)] (7) obtained from the mother liquor of 6 are formed
of isolated Ag(PPh3)3(Hfspa) units. Fig. 3 shows the molecular
structure, and the most significant structural parameters are
listed in Table 3. The Ag atom is coordinated to three PPh3
ligands and to the deprotonated S atom of the Hfspa fragment.
The angles around the silver atom are those of a very slightly
distorted tetrahedron. The Ag–P distances [2.5597(8), 2.5505(9)
and 2.6120(9) A] and the Ag–S distance [2.6179(9) A] are
significantly longer than those found previously in the similar
near-tetrahedral complexes [Ag(PPh3)3(Hmna)]11 (H2mna = 2-
sulfanylnicotinic acid) and [Ag(PPh3)3(Hmba)]12 (H2mba = 2-
sulfanylbenzoic acid) both of which, like 7, have an AgSP3 core.
coordinate bonds (shown schematically in Scheme 2) create
the eight-membered ring Ag4O2S2. In addition to the bonds
forming this ring, there is an Ag–P bond on each Ag atom, and
the O(2) atoms form highly asymmetric Ag–O · · · Ag bridges
supplementing the Ag–S–Ag bridges.
˚
˚
Scheme 2
Each tetranuclear unit has two types of silver atom with
different environments. Ag(1) is essentially three-coordinated,
to P(1), S and one of the carboxylate O atoms of the same
˚
xspa as the S belongs to [Ag(1)–O(1) = 2.347(4)–2.414(3) A],
although it is also bound weakly20 by the other carboxylate O
atom of the other xspa (xspa#1) [Ag(1)–O(2)#1 = 2.736(4)–
˚
2.808(3) A], the weakness of this bond being confirmed by
P(1), Ag(1), S and O(1) being almost coplanar. Ag(2) is four-
coordinated to P(2), to the S coordinated to Ag(1), and to both
the carboxylate O atoms of xspa#1 [Ag(2)–O(1)#1 = 2.365(4)–
˚
˚
2.624(4) A; Ag(2)–O(2)#1 = 2.470(4)–2.590(5) A]. In all four
˚
compounds the Ag(1)–Ag(2) distance [3.1429(7)–3.3839(8) A]
is shorter than twice the van der Waals radius of this metal
(3.44 A).
21
˚
Fig. 3 Molecular structure of [Ag(PPh3)3(Hfspa)] (7) (for clarity,
triphenylphosphine phenyl rings are represented by their P-bound
carbons).
Other characteristics common to these four compounds
include: (i) the asymmetry of the Ag–S–Ag and Ag–O–Ag
bridges; (ii) the almost rectangular Ag–S–Ag angles [79–86◦]
and much wider main Ag–O–Ag angles [138–147◦]; and (iii) the
shortness of the Ag–P bond on essentially three-coordinated
Ag(1) in comparison with the bond on the four-coordinated
Ag(2). It is also worth noting that whereas the Ag(1)–O(1)
distance is practically constant (though just a little longer in
Interestingly, the free CO2H group does not form intermolecu-
lar hydrogen bonds as in 1 and [Au(PPh3)(Hfspa)],10 but a single
intramolecular hydrogen bond with the◦S atom [O(1)–H(1). . .S
˚
0.946(3) 2.1590(11) 2.876(3) A, 131.7(2) ]. As a result, the C(1)–
O(2) bond is shorter than in 1 and [Au(PPh3)(Hfspa)], showing
greater p-bond character.
˚
6), O(1)–Ag(2)#1 bond varies in length from 2.365(4) A in
[(AgPPh3)2(xspa)] (2, 3, 4·(CH3)2CO and 6·(CH3)2CO).
Fig. 4 shows the structure and numbering scheme of the complex
[(AgPPh3)2(Clpspa)] (2) and Table 4 lists the most significant
structural parameters for this complex and for [(AgPPh3)2(o-
mpspa)] (3), [(AgPPh3)2(p-mpspa)] (4) and [(AgPPh3)2(fspa)]
(6) (Figs. S1–S3, ESI†). All four complexes are formed by
tetranuclear [(AgPPh3)2(xspa)]2 units in which most of the
4 (in which the Ag–O–Ag bridge is practically symmetrical)
to 2.624(4) A in 3 (which has the most asymmetrical bridge).
This latter value is at the upper end of the range for Ag–O
bonds in tetrahedral Ag environments20; a longer O(1)–Ag(2)#1
distance would make the xspa carboxylate group bridge between
Ag(1) and Ag(2) in bis-monodentate fashion, as in 5 (see below),
instead of being monodentate for Ag(1) and chelating Ag(2).
˚
1 7 1 2
D a l t o n T r a n s . , 2 0 0 5 , 1 7 0 7 – 1 7 1 5

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◦
˚
Table 4 Selected interatomic distances (A) and angles ( ) in the 2 : 1 triphenylphosphinesilver(I) sulfanylcarboxylate complexes 2, 3, 4·(CH3)2CO,
and 6·(CH3)2CO
(a) Ag environment
2
3
4·(CH3)2CO
2.3503(19)
2.4489(18)
2.347(4)
6·(CH3)2CO
2.3629(14)
2.4539(13)
2.414(3)
Ag(1)–P(1)
Ag(1)–S
Ag(1)–O(1)
2.3504(16)
2.4300(15)
2.359(3)
2.3547(17)
2.4577(16)
2.356(4)
Ag(1)–O(2)#1
Ag(1)–Ag(2)
Ag(2)–P(2)
2.808(3)
2.736(4)
2.748(4)
2.791(3)
3.1429(7)
2.3905(15)
2.5072(14)
2.519(3)
3.2519(6)
2.3812(15)
2.4593(16)
2.624(4)
3.3839(8)
2.3784(17)
2.5267(18)
2.365(4)
3.3111(6)
2.3856(15)
2.5173(14)
2.457(3)
Ag(2)–S
Ag(2)–O(1)#1
Ag(2)–O(2)#1
P(1)–Ag(1)–S
P(1)–Ag(1)–O(1)
P(1)–Ag(1)–O(2)#1
O(1)–Ag(1)–S
Ag(1)–O(1)–Ag(2)#1
Ag(1)–S–Ag(2)
P(2)–Ag(2)–S
P(2)–Ag(2)–O(1)#1
P(2)–Ag(2)–O(2)#1
O(2)#1–Ag(2)–S
O(1)#1–Ag(2)–S
O(1)#1–Ag(2)–O(2)#1
2.470(4)
2.502(4)
2.590(5)
2.509(3)
158.11(5)
120.91(10)
90.37(8)
80.11(10)
143.75(17)
79.06(4)
127.75(5)
119.67(9)
122.01(19)
105.52(9)
105.46(9)
52.49(11)
151.12(6)
124.37(10)
104.98(9)
78.77(10)
146.51(17)
82.81(5)
149.72(6)
110.62(9)
106.53(10)
100.68(9)
96.65(9)
155.62(6)
118.29(11)
101.16(11)
78.88(11)
137.49(19)
85.69(6)
130.63(6)
126.91(11)
117.23(11)
98.26(10)
101.61(11)
52.19(14)
157.56(5)
118.38(8)
100.18(7)
79.01(8)
143.84(14)
83.52(4)
128.36(5)
128.47(9)
120.76(8)
100.63(8)
100.26(8)
53.00(10)
51.21(12)
(b) Ligand
S–C(2)
O(1)–C(1)
O(2)–C(1)
C(1)–C(2)
C(2)–C(3)
C(3)–C(4)
O(2)–C(1)–O(1)
O(2)–C(1)–C(2)
O(1)–C(1)–C(2)
C(3)–C(2)–C(1)
C(3)–C(2)–S
C(1)–C(2)–S
C(2)–C(3)–C(4)
1.764(5)
1.271(6)
1.245(6)
1.516(7)
1.335(7)
1.451(7)
122.5(5)
118.9(5)
118.6(5)
116.5(5)
124.9(4)
118.5(4)
133.7(5)
1.770(6)
1.259(6)
1.260(7)
1.538(8)
1.329(7)
1.469(8)
123.4(6)
117.4(6)
119.2(6)
116.7(6)
123.7(5)
119.4(4)
129.5(6)
1.772(6)
1.243(7)
1.257(7)
1.536(8)
1.324(8)
1.476(9)
122.2(6)
117.6(6)
120.2(6)
117.2(6)
125.2(5)
117.6(5)
132.5(6)
1.764(5)
1.270(5)
1.255(5)
1.510(6)
1.337(6)
1.451(7)
122.8(5)
117.6(5)
119.6(5)
117.7(5)
121.8(4)
120.4(4)
129.4(5)
Although, as far as we know, the Ag4O2S2 ring of these
complexes has not previously been reported, it can be compared
with the similarly eight-membered ring Ag4S4 that is found,
for example, in the triphenylphosphine silver(I) thiocarboxylate
[(AgPPh3)4(l-SC{O}Me–S)4]·C6H5CH3,25 in which two of the
Ag–S–Ag angles are 76.42(3)◦ (similar to the values of 79.06(4)-
85.69(6)◦ in 2, 3, 4·(CH3)2CO and 6·(CH3)2CO) and two are
123.46(5)◦ (137.49(19)–146.51(17)◦ for Ag(1)–O(1)–Ag(2)#1 in
the new compounds).
In the dinuclear monomeric molecules of gold complexes of
type [(AuPPh3)2(xspa)],10 each gold atom is strongly bound to a
P atom and to the thiolate S atom and a bond with a carboxylate
O atom gives Au(I) an environment similar to that of Ag(I) in 2, 3,
4·(CH3)2CO and 6·(CH3)2CO. The silver compounds can be seen
as formed by two mutually inverted (AgPPh3)2(xspa) monomers
similar to the Au(I) compounds, each of which chelates the less
coordinated M atom of the other through its carboxylate group.
In both silver and gold complexes, the M(1)–M(2) distance is
shorter than twice the corresponding van der Waals radius.
In keeping with their crystallographically demonstrated dide-
protonation and coordination the 2 : 1 silver complexes have
IR and Raman spectra in which there are no SH bands and the
IR bands due to the carboxylate group being strongly modified
with respect to those of the free ligands at least in the cases of
2, 3 and 4 in which the asymmetric carboxylate band appears
around 1534 cm−1 and the symmetric band around 1354 cm−1,
making mas(CO2−)–msym(CO2−) around 180 cm−1.
Fig. 5 Molecular structure of [(AgPPh3)2(diBr-o-hpspa)] (5) (triph-
enylphosphine phenyl rings have been omitted for clarity).
tural parameters of which are listed in Table 5. Each tetranu-
clear unit features a twelve-membered Ag4(CO2)2S2 ring in which
each Ag is linked indirectly to two others: to one via the S atom of
the monomer to which these two silver atoms may be considered
to belong, and to the other via a bis-monodentate carboxylate
group that for Ag(1) belongs to its own monomer (by which
it is thus O,S-chelated) and for Ag(2) to the other. The only
other atoms to which the Ag atoms are coordinated are the
P atoms of their PPh3 ligands, so both types of Ag atom are
three-coordinated. The Ag–S, Ag–P and Ag–O distances are,
˚
respectively, 2.4033(10), 2.3442(11) and 2.402(3) A for Ag(1)
˚
and 2.4331(10), 2.3719(11) and 2.445(3) A for Ag(2), i.e. all the
˚
bonds of Ag(2) are 0.03–0.05 A longer than those of Ag(1). The
[(AgPPh3)2(diBr-o-hpspa)] (5). Single crystals obtained by
slow concentration of an acetone solution of [(AgPPh3)2(diBr-
o-hpspa)] are composed of tetranuclear dimers of formula
[(AgPPh3)2(diBr-o-hpspa)]2 (Fig. 5), the most significant struc-
angles around Ag(1) and Ag(2) are also different, Ag(2) having
the more perfect trigonal environment. The Ag(1) · · · Ag(2)
˚
distance, 3.2208(4) A, is again shorter than twice the van der
21
˚
Waals radius of this metal (3.44 A).
D a l t o n T r a n s . , 2 0 0 5 , 1 7 0 7 – 1 7 1 5
1 7 1 3

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◦
˚
Table 5 Selected interatomic distances (A) and angles ( ) in the 2 : 1
triphenylphosphinesilver(I) sulfanylcarboxylate complex 5
signal has shifted to higher field (from 145.6 ppm in H2pspa)
and the C(1) signal to lower field (from 167.1 in H2pspa).
However, the fact that the C(1) signal is practically in the same
position as in the spectrum of [Au(PPh3)(Hpspa)]10 suggests
that the weak Ag–O bond is lost in solution. The ipso carbons
of the PPh3 phenyl rings are more shielded in the complexes
than in free PPh3 (for which their signal lies at 136.428) and
(a) Ag environment
Ag(1)–P(1)
Ag(1)–S
Ag(1)–O(1)
Ag(1)–Ag(2)
Ag(2)–P(2)
Ag(2)–S
2.3442(11) P(1)–Ag(1)–S
2.4033(10) P(1)–Ag(1)–O(1)
S–Ag(1)–O(1)
Ag(1)–S–Ag(2)
2.3719(11) P(2)–Ag(2)–S
162.55(4)
118.19(7)
79.12(7)
83.51(3)
157.64(4)
105.60(7)
96.75(7)
98.75(12)
94.00(12)
2.402(3)
3.2208(4)
1
the value J(13C–31P) increases from 11.5 Hz to 26.4 Hz. Also,
1
the complex has a 31P{ H} NMR signal at 11.36 ppm, close
2.4331(10) P(2)–Ag(2)–O(2)#1
Ag(2)–O(2)#1
2.445(3)
S–Ag(2)–O(2)#1
C(2)–S–Ag(1)
C(2)–S–Ag(2)
to those of other 1 : 1 silver–triphenylphosphine complexes
with S–Ag–P fragments,29 which together with the foregoing
suggests that the PPh3 ligand is still coordinated in solution.
The 109Ag NMR spectrum, in dmso/dmso-d6 solution at room
temperature shows just a single signal, which indicates that
there is only one Ag species present in solution. Its position,
936.3 ppm, is compatible with the incorporation of a P atom in
an Ag–S2 environment,5a,30,31 but also with other environments,
such as AgPS2O (the result of coordination of a dmso molecule)
or, more probably, AgPSO (the result of coordination of a dmso
molecule and cleavage of the weaker Ag–S bond).
C(1)–O(2)–Ag(2)#1 130.6(3)
C(1)–O(1)–Ag(1)
116.2(3)
(b) Ligand
S–C(2)
O(1)–C(1)
O(2)–C(1)
C(1)–C(2)
C(2)–C(3)
C(3)–C(4)
1.779(4)
1.260(4)
1.251(5)
1.532(5)
1.324(4)
1.473(5)
O(2)–C(1)–O(1)
O(2)–C(1)–C(2)
O(1)–C(1)–C(2)
C(3)–C(2)–C(1)
C(3)–C(2)–S
C(1)–C(2)–S
C(2)–C(3)–C(4)
125.7(4)
115.9(4)
118.4(4)
119.3(4)
120.2(3)
120.4(3)
126.6(4)
[(AgPPh3)2(xspa)] (2, 3, 4·(CH3)2CO and 6. In the 1H NMR
spectra of these complexes the dideprotonation of the ligand
is reflected by there being no signals for either the thiol or the
CO2H group. Also, the C(3)H signals are shifted to higher field
than in the spectra of the free ligands, which as in the case of
1 suggests that the S-coordination detected in the solid state is
also present in solution. The 13C NMR spectra show C(3) to be
more shielded in the complexes than in the free ligands, which
corroborates the persistence of S–Ag bonds in solution. The fact
that the C(1) signal of 6 in solution is close to its position in the
13C CP/MAS spectrum may perhaps be an indication that the
Ag–O bonds detected in the solid state also persist in solution,
and hence that the dimers of the solid remain intact, but the
apparently contradictory though inconclusive 109Ag results (vide
infra) make it impossible to draw a definite conclusion in this
regard.
The two monomers are linked not only by the Ag(1)–OCO–
Ag(2)#1 bridge, but also by hydrogen bonds between the
diBr-o-hpspa OH groups and the carboxylate oxygen involved
in chelation of Ag(1) [O(3)–H(3). . .O(1)#1: 0.74(4), 1.91(4),
2.639(4) A, 170(5) ]. This hydrogen bond may be responsible
for the inability of O(1) to coordinate to Ag(2)#1 as it does
in 2, 3, 4·(CH3)2CO and 6·(CH3)2CO (vide supra), and suggests
that a molecule with an XH group able to form hydrogen bonds
might be able to cleave the O(1)–Ag(2)#1 bond of these latter
complexes.
The IR and Raman spectra of 5 show no SH bands and the
bands due to the bis-monodentate bridging COO− group are
strongly modified with respect to the free ligand, the asymmetric
band lying at 1556 cm−1 and the symmetric band at 1349 cm−1,
so that mas(CO2−)–msym(CO2−) = 207 cm−1.
◦
˚
As in 1, the ipso carbons of the triphenylphosphine phenyl
rings, are more shielded than in free PPh3, in the spectrum of
which they appear at 136.4 ppm in dmso and 137.4 ppm in
Solution studies
Attempts were made to record 1H and 13C NMR spectra of the
ligands and complexes in both dmso-d6 and CDCl3, but poor
solubility prevented the recording of some of these spectra.
Signals were identified on the basis of our previous data for
similar compounds10,26 and, when necessary, by means of two-
1
CDCl3,29 and the value of J(13C–31P) increases from 11.5 Hz
(dmso) or 12,5 Hz (CDCl3)29 to around 20 Hz for the complexes.
The 31P NMR spectra of the complexes, all show a single peak
attributable to coordinated PPh3 at 6.9–11.0 ppm in dmso and
3.7–5.2 ppm in CDCl3 (cf. −3.64 and −5.33 ppm, respectively,
for free PPh3). These chemical shifts are similar to those found
in other triphenylphosphinesilver(I) derivatives.5b,11,12
1
dimensional H–13C NMR (HMQC and HMBC) and DEPT
methods. The aromatic region of these spectra is complicated
by the large number of hydrogen and carbon atoms of the
triphenylphosphine ligand. Although several compounds were
subjected to solid state 13C CP/MAS spectrometry only for
[(AgPPh3)2fspa] was it possible to identify any of the signals.
All the 1H NMR spectra of the ligands exhibited a very broad
peak at low field that was attributed to the COOH proton. The
thiol proton signal was only identified in the spectra of H2pspa
and H2Clspa, in which it is located near 5.00 ppm. The 13C
spectra of all the ligands show the CO2H signal near 167 ppm,
the C(3) signal of H2-diBr-o-hpspa was not located and those
of H2pspa, H2Clspa, H2-o-mpspa, H2-p-mpspa and H2fspa were
located between 132.0 and 145.6 ppm.
The109Ag NMR spectrum of 6 in dmso/dmso-d6 at room tem-
perature showed just a single signal (at 1033.4 ppm), suggesting
that all the Ag(I) atoms are equivalent in solution (and hence
that the dimers of the solid do not remain intact, in apparent
contradiction with the 13C NMR results). Furthermore, the
halfwidth of the peak, 217 Hz, (Fig. S4, ESI†), is half that of
compound 1, 535 Hz, which appears to rule out the possibility of
equilibrium between the two types of Ag(I) coordination found
in the solid state (or if there is an equilibrium it is very fast on
the NMR experiment timescale). However as in the case of 1,
diagnosis of the Ag environment from the position of the signal
is impossible because of the lack of systematic data for similar
systems.
[Ag(PPh3)(Hpspa)] (1). In keeping with the non-
deprotonation of the CO2H group in crystals of 1 the
1
1
broad signal at 12.60 ppm in the H NMR spectrum of the
[(AgPPh3)2(diBr-o-hpspa)] (5). As expected, the H NMR
ligand persists in that of the complex, in which the absence
of any SH signal and the shift of the C(3)H signal to higher
field (from 7.73 ppm for H2pspa) are in keeping with the
S-coordination found in the solid state.10,26,27 Although it is
not clear whether both the Ag–S bonds persist (i.e. whether
the dimers of 1 remain intact), S-coordination is further
corroborated by the 13C NMR spectrum, in which the C(3)
spectrum of this complex showed no signals for either the
thiol proton or the CO2H group. Unfortunately, rigorous
interpretation of the 13C NMR spectrum was prevented by
the poor solubility of the complex and the complexity of the
spectrum; in particular, it was not possible to identify the C(1)
and the C(3) signals, which prevented the coordination mode of
the sulfanyl and carboxylate groups from being inferred.
1 7 1 4
D a l t o n T r a n s . , 2 0 0 5 , 1 7 0 7 – 1 7 1 5

View Article Online
The 31P NMR spectra in dmso-d6 and CDCl3, both show a
single peak attributable to coordinated PPh3 (at 7.0 ppm in dmso
and 2.4 ppm in CDCl3).
13 K. Nomiya, H. Yokoyama, R. Noguchi and K. Machida, Chem.
Lett., 2002, 922.
14 M. J. McKeage, L. Maharaj and S. J. Berners-Price, Coord. Chem.
Rev., 2002, 232, 127.
15 K. Nomiya, S. Yamamato, R. Noguchi, H. Yokoyama, N. Ch.
Kasuga, K. Okyamarand and Ch. Kato, J. Inorg. Biochem., 2003,
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Acknowledgements
We thank the EU Directorate General for Regional Poli-
cies and the Directorate General for Research of the Span-
ish Ministry of Science and Technology for financial sup-
port under ERDF programs (projects BQU2002-04524-CO2-
01 and BQU2002-04524-CO2-02), and the Xunta the Galicia,
Spain, for support under projects PGIDIT03PXIC20306PN and
PGIDIT03PXIC30103PN.
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1 7 1 5