Novel types of tetra-, hexa-. octa-. and dodecanuclear silver clusters containing (2,7-Di-tert-butylfluoren-9-ylidene) methanedithiolate

Article abstract of DOI:10.1021/ic802045j

The reaction of AgCIO₄ with piperidinium 2,7-di-tert-butyl-9H- fluorene-9-carbodithioate (pipH)[S₂C(t-Bu-Hfy)] (1) (t-Bu-Hfy = 2,7-di-tert-butylfluoren-9-yl) afforded [Ag_n{S₂C(t-Bu-Hfy) }_n] (2), which

Full text of DOI:10.1021/ic802045j

Inorg. Chem. 2009, 48, 2060-2071
Novel Types of Tetra-, Hexa-, Octa-, and Dodecanuclear Silver Clusters
Containing (2,7-Di-tert-butylfluoren-9-ylidene)methanedithiolate†
Jose´ Vicente,‡ Pablo Gonza´lez-Herrero,*,‡ Yolanda Garc´ıa-Sa´nchez,‡ and Peter G. Jones§
Grupo de Qu´ımica Organometa´lica, Departamento de Qu´ımica Inorga´nica, Facultad de Qu´ımica,
UniVersidad de Murcia, Apdo. 4021, 30071 Murcia, Spain, and Institut fu¨r Anorganische and
Analytische Chemie, Technische UniVersita¨t Braunschweig, Postfach 3329,
38023 Braunschweig, Germany
Received October 24, 2008
The reaction of AgClO4 with piperidinium 2,7-di-tert-butyl-9H-fluorene-9-carbodithioate (pipH)[S2C(t-Bu-Hfy)] (1) (t-
Bu-Hfy ) 2,7-di-tert-butylfluoren-9-yl) afforded [Agn{S2C(t-Bu-Hfy)}n] (2), which reacted with phosphines to give
[Ag{S2C(t-Bu-Hfy)}L2] [L ) PPh3 (3a); L2 ) bis(diphenylphosphino)ethane (dppe, 3b), 1,1′-bis(diphenylphosphino)-
ferrocene (dppf, 3c). By reacting complex 2 with AgClO4 and piperidine in a 1:1:1 molar ratio, the dodecanuclear
cluster [Ag12{S2Cd(t-Bu-fy)}6] (4) (t-Bu-fy ) 2,7-di-tert-butylfluoren-9-ylidene) was obtained. Compound 4 can also
be directly prepared from the reaction of 1 with AgClO4 and piperidine in a 1:2:1 molar ratio. The reactions of 1
with AgClO4, phosphines, and piperidine afforded the compounds [Ag6{S2Cd(t-Bu-fy)}3L5] [1:2:2:1 molar ratio; L )
PPh3 (5a), P(p-To)3 (5b)], [Ag4{S2Cd(t-Bu-fy)}2(dppf)2] (6) (1:2:1:1 molar ratio), [Agn{S2Cd(t-Bu-fy)}n/2{P(i-Pr)3}n] (7)
(1:2:2:1 molar ratio), or [Ag8{S2Cd(t-Bu-fy)}4{P(i-Pr)3}4] (8) (1:2:1:1 molar ratio). Complexes 5a,b, 6, 7, and 8 can
be also obtained by reacting 4 with the corresponding phosphine in the appropriate molar ratio. The crystal structures
of 4, 5b, and 8 have been determined by X-ray diffraction studies. The nuclearity of complex 6 was established
from its 31P{1H} NMR data, which reveal a very fast dynamic process leading to an average coupling of each of
the P atoms of the dppf ligands with four Ag atoms.
Introduction
and coordination polymers.9 Our research group has been
involved in the synthesis of polynuclear complexes with this
type of ligand, including heterometallic derivatives.10,11
However, the previously reported silver complexes with 1,1-
Silver complexes and clusters with thiolato ligands have
been the subject of considerable interest because of their
extraordinary structural diversity.1,2 The study of their
structures, bonding modes, and spectroscopic features has
proved to be relevant to the structural elucidation of the
metal-binding sites of metallothioneins.3 In recent years, their
importance has become apparent for a number of applications
in the area of advanced materials, including the synthesis of
monolayer-protected clusters4 and the thermolytic preparation
of nanostructured materials.5
(2) (a) Chen, J.-X.; Xu, Q.-F.; Xu, Y.; Zhang, Y.; Chen, Z.-N.; Lang,
J.-P. Eur. J. Inorg. Chem. 2004, 4247. (b) Fijolek, H. G.; Gonzalez-
Duarte, P.; Park, S. H.; Suib, S. L.; Natan, M. J. Inorg. Chem. 1997,
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Y.; Yamada, Y.; Okamoto, K. i. J. Inorg. Biochem. 2000, 82, 229.
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A. J.; Gasyna, Z.; Stillman, M. J. J. Biol. Chem. 1989, 264, 17091.
(f) Krebs, B.; Henkel, G. Angew. Chem., Int. Ed. 1991, 30, 769.
(4) (a) Branham, M. R.; Douglas, A. D.; Mills, A. J.; Tracy, J. B.; White,
P. S.; Murray, R. W. Langmuir 2006, 22, 11376. (b) Pradeep, T.; Mitra,
S.; Nair, A. S.; Mukhopadhyay, R. J. Phys. Chem. B 2004, 108, 7012.
(c) Fenske, D.; Persau, C.; Dehnen, S.; Anson, C. E. Angew. Chem.,
Int. Ed. 2004, 43, 305.
1,1-Ethylenedithiolates (XYCdCS22-) and related dithio
ligands have received attention because of their ability to
form high-nuclearity clusters,6,7 heteronuclear complexes,8
* To whom correspondence should be addressed. E-mail: pgh@um.es.
† (Fluoren-9-ylidene)methanedithiolato Complexes, part 6. For previous
parts, see refs 11, 18-21.
‡
Universidad de Murcia.
Technische Universita¨t Braunschweig.
(5) (a) Chen, Y.-B.; Chen, L.; Wu, L.-M. Inorg. Chem. 2005, 44, 9817.
(b) Carotenuto, G.; Martorana, B.; Perlo, P.; Nicolais, L. Polym. News
2004, 29, 315. (c) Viau, G.; Piquemal, J.-Y.; Esparrica, M.; Ung, D.;
Chakroune, N.; Warmont, F.; Fievet, F. Chem. Commun. 2003, 2216.
§
(1) Jin, X.; Xie, X.; Qian, H.; Tang, K.; Liu, C.; Wang, X.; Gong, Q.
Chem. Commun. 2002, 600.
2060 Inorganic Chemistry, Vol. 48, No. 5, 2009
10.1021/ic802045j CCC: $40.75  2009 American Chemical Society
Published on Web 01/29/2009

NoWel Types of SilWer Clusters
Chart 1
ethylenedithiolates are very scarce and have been described
2-
only with the ligands (NC)2CdCS2 (i-mnt) and {(EtO)2-
2-
P(O)}(NC)CdCS2 (cpdt). Most of them are anionic
clusters, namely, [Ag8(i-mnt)6]4-,12 [Ag6(i-mnt)6]6-,13 [Ag4(i-
mnt)4]4-, [Ag8(i-mnt)6(PPh3)4]4-, and [Ag9(i-mnt)6-
(PPh3)6]3-.7,14 The only neutral complexes are the tetranu-
clear clusters [Ag4(i-mnt)2(dppm)4]15 and [Ag4(cpdt)2-
(dppm)4]16 and the coordination polymer [Ag4(i-
mnt)2(HPyS)4]n (HPyS ) pyridine-2-thione).17 The cationic
derivative [Ag5(cpdt)2(dppm)4](PF6) has also been reported.16
We have recently undertaken the study of the reactivity
and photophysical properties of transition metal complexes
with (fluoren-9-ylidene)methanedithiolate and several disub-
stituted derivatives.11,18-21 The di-tert-butyl-substituted ho-
mologue [(t-Bu-fy)dCS22-, Chart 1] is particularly suitable
for the synthesis of metal complexes, because it normally
gives more stable and soluble species. In general, the ligands
of this kind show remarkable differences from the previously
used 1,1-ethylenedithiolates; these are largely attributable to
the absence of strongly electron-withdrawing substituents and
affect the photophysical properties and redox behavior of
their metal complexes. Thus, the strongly electron-donating
character of these ligands is responsible for the facile
oxidation of certain Au(I) and Pt(II) complexes under
atmospheric conditions and the unusually low energies of
their charge-transfer absorptions and emissions.18,20 We have
also reported the aerial oxidation of Cu(I) and Cu(II) to
Cu(III) complexes with (t-Bu-fy)dCS22- 19 and the formation
of dinuclear derivatives with the condensed dithiolato ligands
19,21
2-
2-
S[(t-Bu-fy)dCS]2 and S[(t-Bu-fy)dCS]3
.
In view of the atypical characteristics of the (fluoren-9-
ylidene)methanedithiolato ligands, we thought it of interest
to carry out an exploration of the chemistry of silver
complexes with (t-Bu-fy)dCS22-. Here, we present a series
of neutral Ag(I) complexes with this ligand and also with
its protonated precursor, (t-Bu-Hfy)CS2- (Chart 1). The new
dithiolato complexes represent unprecedented types of silver
thiolate clusters.
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Chem. Commun 1997, 2047. (b) Vicente, J.; Chicote, M. T.; Gonza´lez-
Herrero, P.; Jones, P. G.; Humphrey, M. G.; Cifuentes, M. P.; Samoc,
M.; Luther-Davies, B. Inorg. Chem. 1999, 38, 5018. (c) Vicente, J.;
Chicote, M. T.; Huertas, S.; Bautista, D.; Jones, P. G.; Fischer, A. K.
Inorg. Chem. 2001, 40, 2051. (d) Vicente, J.; Chicote, M. T.; Huertas,
S.; Jones, P. G. Inorg. Chem. 2003, 42, 4268. (e) Vicente, J.; Chicote,
M. T.; Huertas, S.; Jones, P. G.; Fischer, A. K. Inorg. Chem. 2001,
40, 6193. (f) Vicente, J.; Chicote, M. T.; Mart´ınez-Viviente, E.;
Mart´ınez-Mart´ınez, A. J.; Jones, P. G. Inorg. Chem. 2006, 45, 10434.
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Bautista, D. Inorg. Chem. 2007, 46, 4718.
(12) Birker, P. J. M. W. L.; Verschoor, G. C. J. Chem. Soc., Chem.
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Experimental Section
General Considerations, Materials, and Instrumentation. All
preparations were carried out at room temperature under an
atmosphere of nitrogen using Schlenk techniques, except in the
cases indicated. Synthesis-grade solvents were obtained from
commercial sources. Piperidinium 2,7-di-tert-butyl-9H-fluorene-9-
carbodithioate (1) was prepared as previously decribed.22 All other
reagents were obtained from commercial sources and used without
further purification. NMR spectra were recorded on Bruker Avance
200, 300, or 400 spectrometers, usually at 298 K, unless otherwise
indicated. Chemical shifts are referred to internal TMS (1H and
13C{1H}) or external 85% H3PO4 (31P{1H}). The assignments of
1
the H and 13C{1H} NMR spectra were made with the help of
HMBC and HSQC experiments. Chart 1 shows the atom numbering
of the dithiolato ligand. NMR simulations were carried out with
the program gNMR 5.0. Melting points were determined on a
Reichert apparatus and are uncorrected. Elemental analyses were
carried out with a Carlo Erba 1106 microanalyzer. Infrared spectra
were recorded in the range 4000-200 cm-1 on a Perkin-Elmer
Spectrum 100 spectrophotometer using KBr pellets. Electronic
absorption spectra were recorded on a Unicam UV500 spectro-
photometer.
X-Ray Structure Determinations. Crystals of 4, 5b, and 8
suitable for X-ray diffraction studies were obtained from C6H6/
hexane (4) or CH2Cl2/MeCN (5b, 8). Numerical details are
presented in Table 1. The data for 4 were collected on an Oxford
Diffraction Nova O diffractometer using mirror-focused Cu KR
radiation in the ω-scan mode. The data for 5b and 8 were collected
on an Oxford Diffraction Xcalibur S diffractometer using mono-
chromated Mo KR radiation in the ω-scan mode. The structures
were solved by direct methods and refined anisotropically on F2
(21) Vicente, J.; Gonza´lez-Herrero, P.; Garc´ıa-Sa´nchez, Y.; Bautista, D.
Inorg. Chem. 2008, 47. 10662.
(22) Vicente, J.; Gonza´lez-Herrero, P.; Garc´ıa-Sa´nchez, Y.; Pe´rez-Cadenas,
M. Tetrahedron Lett. 2004, 45, 8859.
Inorganic Chemistry, Vol. 48, No. 5, 2009 2061

Vicente et al.
Table 1. Crystallographic Data for 4·C6H14 ·4C6H6, 5b·CH2Cl2 ·3MeCN, and 8·CH2Cl2 ·3MeCN
4·C6H14 ·4C6H6
5b·CH2Cl2 ·3MeCN
8·CH2Cl2 ·3MeCN
formula
fw
T (K)
C162H182Ag12S12
3808.24
103(2)
1.54184
monoclinic
P21/n
14.5153(3)
31.7686(6)
34.3104(6)
90
90.769(3)
90
15820.2(5)
4
1.599
13.469
0.0594
C178H188Ag6Cl2N3P5S6
3434.82
100(2)
C131H191Ag8Cl2N3P4S8
3122.09
100(2) K
0.71073
monoclinic
C2/c
26.7245(5)
20.9427(5)
25.0333(6)
90
93.527(3)
90
13984.2(5)
4
1.483
1.345
λ (Å)
0.71073
cryst syst
space group
a (Å)
triclinic
j
P1
16.5832(5)
17.4121(5)
32.9195(10)
75.352(3)
75.838(3)
63.234(3)
8116.5(4)
2
1.414
0.937
0.0543
0.1282
b (Å)
c (Å)
R (deg)
ꢀ (deg)
γ (deg)
V (Å3)
Z
Fcalcd (Mg m-3
)
µ (mm-1
R1a
)
0.0270
0.0628
wR2b
0.1765
a R1 ) ∑|Fo| - |Fc|/∑|Fo| for reflections with I > 2σ(I). b wR2 ) [∑[w(Fo2 - Fc2)2]/∑[w(Fo )2]0.5 for all reflections; w-1 ) σ2(F2) + (aP)2 + bP, where
2
2
P ) (2Fc2 + Fo )/3 and a and b are constants set by the program.
using the program SHELXL-97 (G. M. Sheldrick, University of
Go¨ttingen).23 Restraints to local aromatic ring symmetry or light-
atom displacement factor components were applied in some cases.
Special features of refinement are as follows: The structure of 4
contains four benzene molecules and one hexane, as well as at least
one solvent site that could not be identified. Much of the solvent
does not refine well. Furthermore, some t-Bu groups are poorly
resolved. In view of these problems, C atoms were refined
isotropically. For compound 5b, extensive regions of residual
electron density presumably correspond to solvent molecules but
could not be refined satisfactorily. Accordingly, the program
SQUEEZE (A. L. Spek, University of Utrecht, Netherlands) was
used to remove mathematically the effects of the solvent. For
calculations of formula mass and so forth, an idealized solvent
content of one CH2Cl2 and three MeCN molecules was assumed.
t-Bu hydrogens were assigned assuming ideally staggered methyl
groups. p-Tolyl methyl groups were modeled using idealized
geometry but may suffer from rotational disorder. For compound
8, residual electron density was tentatively identified as one MeCN
site and one superimposed site with CH2Cl2 and MeCN. However,
this model could not be refined adequately. The program SQUEEZE
was therefore used to cancel the effect of the solvent. For the
calculation of mass-dependent parameters, an idealized composition
of one CH2Cl2 and three MeCN molecules was assumed. The t-Bu
group at C15 is disordered.
[Agn{S2C(t-Bu-Hfy)}n] (2). To a solution of piperidinium 2,7-
di-tert-butyl-9H-fluorene-9-carbodithioate (1) (583 mg, 1.22 mmol)
in acetone (15 mL) was added AgClO4 (246 mg, 1.19 mmol). An
orange precipitate immediately formed, which was filtered off,
recrystallized from CH2Cl2/MeOH, and vacuum-dried to give 2 as
a red solid. Yield: 508 mg, 93%. Anal. calcd for C22H25AgS2: C,
57.26; H, 5.46; S, 13.90. Found: C, 56.94; H, 5.56; S, 13.79. Mp:
198 °C (dec). IR (KBr, cm-1): ν(CS2), 1020. 1H NMR (400.9 MHz,
CDCl3): δ 7.38 (d, 3JHH ) 8.0 Hz, 2 H each, H4, H5), 7.22 (s, 2 H,
H1, H8), 7.17 (d, 3JHH ) 8.0 Hz, 2 H, H3, H6), 5.64 (s, 1 H, H9),
1.02 (s, 18 H, t-Bu). 13C{1H} NMR (100.8 MHz, CDCl3): δ 151.1
(C2, C7), 146.2 (C8a, C9a), 138.7 (C4a, C4b), 125.8 (C3, C6),
121.7 (C1, C8), 119.6 (C4, C5), 72.2 (C9), 35.5 (CMe3), 32.2
(CMe3).
0.21 mmol), and the resulting orange solution was stirred for 30
min. The solvent was removed under a vacuum, and the residue
was treated with hexane (20 mL) to give a pale brown precipitate,
which was filtered off, washed with hexane (2 × 2 mL), and
vacuum-dried to give 3a. Yield: 171 mg, 84%. Anal. calcd for
C58H55AgP2S2: C, 70.65; H, 5.59; S, 6.49. Found: C, 70.38; H, 5.62;
S, 6.50. Mp: 134 °C. IR (KBr, cm-1): ν(CS2), 1012. 1H NMR (400.9
3
MHz, CDCl3): δ 7.85 (s, 2 H, H1, H8), 7.62 (d, JHH ) 8.0 Hz, 2
H, H4, H5), 7.37 (dd, 3JHH ) 8.0 Hz, 4JHH ) 1.6 Hz, 2 H, H3, H6),
7.33-7.29 (m, 18 H, o-H + p-H, Ph), 7.19-7.16 (m, 12 H, m-H,
PPh3), 5.66 (s, 1 H, H9), 1.25 (s, 18 H, t-Bu). 13C{1H} NMR (50.1
MHz, CDCl3): δ 259.6 (CS2), 149.4 (C2, C7), 146.1 (C8a, C9a),
138.3 (C4a, C4b), 133.8 (d, 1JC-P ) 27.0 Hz, i-C, Ph), 133.3 (o-C,
3
Ph), 129.7 (p-C, Ph), 128.6 (d, JCP ) 14.7 Hz, m-C, Ph), 124.3
(C3, C6), 122.7 (C1, C8), 118.7 (C4, C5), 72.6 (C9), 34.9 (CMe3),
31.6 (CMe3). 31P{1H} NMR (162.3 MHz, CDCl3, 223 K): δ 6.96
1
1
107Ag
109Ag
(2 d, JP-
) 355 Hz, JP-
) 407 Hz).
[Ag{S2C(t-Bu-Hfy)}(dppe)] (3b). This pale orange compound
was prepared as described for 3a, from 2 (63 mg, 0.14 mmol) and
dppe (61 mg, 0.15 mmol). Yield: 100 mg, 86%. Anal. calcd for
C48H49AgP2S2: C, 67.05; H, 5.74; S, 7.46. Found: C, 67.04; H, 5.88;
S, 7.05. Mp: 181 °C (dec). IR (KBr, cm-1): ν(CS2), 1011. 1H NMR
(400.9 MHz, CDCl3): δ 7.93 (s, 2 H, H1, H8), 7.66 (d, 3JHH ) 8.0
Hz, 2 H, H4, H5), 7.41-7.39 (m, 10 H, H3, H6 + Ph), 7.30-7.26
(m, 4 H, Ph), 7.17-7.14 (m, 8 H, Ph), 5.71 (s, 1 H, H9), 2.36 (s,
4 H, CH2), 1.25 (s, 18 H, t-Bu). 13C{1H} NMR (100.8 MHz,
CDCl3): δ 149.5 (C2, C7), 146.1 (C8a, C9a), 138.4 (C4a, C4b),
133.1 (i-C, Ph), 132.7 (o-C, Ph), 130.0 (p-C, Ph), 128.8 (m-C, Ph),
124.3 (C3, C6), 122.7 (C1, C8), 118.8 (C4, C5), 72.7 (C9), 34.9
(CMe3), 31.6 (CMe3), 24.8 (CH2) (CS2 not observed). 31P{1H} NMR
1
107Ag
(162.3 MHz, CDCl3, 223 K): δ 3.16 (2 d, JP-
) 351 Hz,
1JP-
) 405 Hz).
109Ag
[Ag{S2C(t-Bu-Hfy)}(dppf)] (3c). This orange compound was
obtained as a monohydrate following the procedure described for
3a, from 2 (126 mg, 0.27 mmol) and dppf (163 mg, 0.29 mmol).
Yield: 235 mg, 85%. Anal. calcd for C48H55AgOP2S2: C, 65.06; H,
5.36; S, 6.20. Found: C, 65.13; H, 5.29; S, 6.12. Mp: 156 °C (dec).
1
IR (KBr, cm-1): ν(CS2), 1011. H NMR (400.9 MHz, CDCl3): δ
3
7.93 (br, 2 H, H1, H8), 7.63 (d, JHH ) 8.0 Hz, 2 H, H4, H5),
3
4
[Ag{S2C(t-Bu-Hfy)}(PPh3)2] (3a). To a solution of PPh3 (118
mg, 0.45 mmol) in CH2Cl2 (15 mL) was added complex 2 (96 mg,
7.54-7.50 (m, 10 H, Ph), 7.37 (dd, JHH ) 8.0 Hz, JH-H ) 1.5
Hz, 2 H, H3, H6), 7.34-7.23 (m, 10 H, Ph), 5.72 (s, 1 H, H9),
4.27 (t, 3JH-H ) 1.7 Hz, 4 H, H2, H5, Cp), 4.11 (br, 4 H, H3, H4,
Cp), 1.21 (s, 18 H, t-Bu). 13C{1H} NMR (75.4 MHz, CDCl3): δ
(23) Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, 64, 112.
2062 Inorganic Chemistry, Vol. 48, No. 5, 2009

NoWel Types of SilWer Clusters
259.5 (CS2), 149.4 (C2, C7), 146.1 (C8a, C9a), 138.3 (C4a, C4b),
134.5 (vt, N ) 24.2 Hz, i-C, Ph), 133.9 (vt, N ) 19.1 Hz, o-C,
Ph), 129.7 (p-C, Ph), 128.4 (vt, N ) 9.5 Hz, m-C, Ph), 124.2 (C3,
C6), 122.5 (C1, C8), 118.6 (C4, C5), 74.0 (vt, N ) 28.1 Hz, C2,
C5, Cp), 72.7 (br, C9), 71.8 (br, C3, C4, Cp), 34.8 (CMe3), 31.5
(CMe3) (C1 of Cp not observed). 31P{1H} NMR (162.3 MHz,
C, 63.37; H, 5.83; S, 5.78. Mp: 158 °C (dec). IR (KBr, cm-1):
1 4
ν(CdCS2), 1496. H NMR (400.9 MHz, CDCl3): δ 9.31 (d, JHH
3
) 1.6 Hz, 6 H, H1, H8), 7.59 (d, JHH ) 8.0 Hz, 6 H, H4, H5),
7.19 (dd, 4JHH ) 1.6 Hz, 3JHH ) 8.0 Hz, 6 H, H3, H6), 7.02 (m, 30
H, To), 6.60 (br, 30 H, To), 2.10 (s, 45 H, Me, To), 1.18 (s, 54 H,
t-Bu). 13C{1H} NMR (100.8 MHz, CDCl3): δ 151.9 (br, CS2), 148.2
(C2, C7), 140.9 (C8a, C9a), 139.1 (p-C, To), 136.2 (C4a, C4b),
1
1
107Ag
109Ag
CDCl3, 223 K): δ -5.9 (2 d, JP-
) 338 Hz, JP-
) 389
2
Hz).
133.5 (d, JCP ) 17 Hz, o-C, To), 132.1 (C9), 130.1 (br, i-C, To),
3
[Ag12{S2Cd(t-Bu-fy)}6] (4). Method A. To a solution of 1 (203
mg, 0.42 mmol) and AgClO4 (170 mg, 0.82 mmol) in THF (15
mL) was added piperidine (44 µL, 0.44 mmol), and the resulting
orange solution was stirred for 48 h. The solvent was removed under
a vacuum, and the residue was treated with MeOH (30 mL),
whereupon a brown precipitate formed, which was filtered off and
recrystallized from CHCl3/pentane to give 4 as a yellowish orange
solid. Yield: 130 mg, 56%.
Method B. To a solution of complex 2 (202 mg, 0.44 mmol)
and AgClO4 (90 mg, 0.44 mmol) in THF (15 mL) was added
piperidine (44 µL, 0.44 mmol), and the resulting orange solution
was stirred for 6 h. The solvent was removed under a vacuum, and
the residue was treated with MeOH (30 mL), whereupon an orange
precipitate formed, which was filtered off and recrystallized from
CHCl3/pentane to give 4. Yield: 85 mg, 35%.
129.2 (d, JCP ) 9 Hz, m-C, To), 124.8 (C1, C8), 121.8 (C3, C6),
116.9 (C4, C5), 34.9 (CMe3), 31.8 (CMe3), 21.3 (Me, To). 31P{1H}
NMR (162.3 MHz, CDCl3): δ 3.5 (br).
[Ag4{S2Cd(t-Bu-fy)}2(dppf)2] (6). Method A. A solid mixture
of 1 (104 mg, 0.22 mmol), AgClO4 (85 mg, 0.41 mmol), and dppf
(124 mg, 0.22 mmol) was suspended in MeCN (15 mL). Piperidine
(24 µL, 0.24 mmol) was then added, and the mixture was stirred
for 30 min. A yellow solid gradually precipitated, which was filtered
off, washed with MeCN (2 × 3 mL), and vacuum-dried. Yield:
221 mg, 96%.
Method B. To a solution of compound 4 (104 mg, 0.06 mmol)
in CH2Cl2 (10 mL) was added dppf (116 mg, 0.21 mmol), and the
mixture was stirred for 35 min. A small amount of a yellow solid
gradually precipitated. The solvent was partially evaporated under
a vacuum (5 mL), and Et2O was added to complete the precipitation.
The solid was then filtered off and vacuum-dried to give 6. Yield:
164 mg, 80%. Anal. calcd for C112H104Ag4Fe2P4S4: C, 59.91; H,
4.67; S, 5.71. Found: C, 59.98; H, 4.70; S, 5.82. Mp: 179 °C (dec).
IR (KBr, cm-1): ν(CdCS2), 1484. 1H NMR (400.9 MHz, CDCl3):
δ 9.55 (d, 4JHH ) 1.5 Hz, 4 H, H1, H8), 7.62 (d, 3JHH ) 7.9 Hz, 4
H, H4, H5), 7.48-7.43 (m, 16 H, o-H, Ph), 7.19-7.13 (m, 12 H,
Method C. A suspension of complex 5a (431 mg, 0.197 mmol)
in distilled THF (30 mL) was stirred for 48 h under atmospheric
conditions. An orange solution was obtained. The solvent was
removed under a vacuum, and the residue was treated with MeOH
(30 mL), whereupon an orange precipitate formed, which was
filtered off, washed with MeOH (2 mL), and vacuum-dried to give
4. Yield: 186 mg, 83%. Anal. calcd for C132H144Ag12S12: C, 46.50;
H, 4.26; S, 11.28. Found: C, 46.65; H, 4.13; S, 10.63. Mp: 192 °C
2
H3, H6 + p-H, Ph), 6.95 (t, JHH ) 7.2 Hz, 16 H, m-H, Ph), 4.83
(br, 8 H, Cp), 3.79 (s, 8 H, Cp), 1.13 (s, 36 H, t-Bu). 13C{1H}
NMR (100.8 MHz, CDCl3): δ 152.3 (CS2), 147.8 (C2, C7), 141.1
(C8a, C9a), 135.2 (C4a, C4b), 133.8 (i-C, Ph), 133.4 (m, o-C, Ph),
133.0 (C9), 129.7 (p-C, Ph), 128.4 (m, m-C, Ph), 123.9 (C1, C8),
121.0 (C3, C6), 117.3 (C4, C5), 75.8 (d, 2JCP ) 14.6 Hz, C1, Cp),
1
(dec). IR (KBr, cm-1): ν(CdCS2), 1503, 1473. H NMR (400.9
4
MHz, CDCl3): δ 9.11, 9.02, 9.01 (all d, JHH ) 1.5 Hz, 2 H each,
H1, H8), 7.57-7.52 (m, 6 H, H4, H5), 7.32, 7.29, 7.21 (all dd,
4JHH ) 1.5 Hz, 3JHH ) 8.0 Hz, 2 H each, H3, H6), 1.32, 1.26, 1.04
(all s, 18 H each, t-Bu). 13C{1H} NMR (100.8 MHz, CDCl3): δ
149.8, 149.5, 149.4 (C2, C7), 144.2 (br, CS2), 139.5, 139.4, 138.9
(C8a, C9a), 137.7, 137.6, 137.4 (C4a, C4b), 135.2, 134.9 (C9),
125.6, (C3, C6), 125.1, 125.0, 124.9, 124.7 (C1, C8, C3, C6), 118.3,
118.1, 118.0 (C4, C5), 35.1, 35.0 (CMe3), 32.0, 31.8, 31.7 (CMe3).
[Ag6{S2Cd(t-Bu-fy)}2(PPh3)5] (5a). To a solution of dithioate
1 (154 mg, 0.32 mmol) in MeCN (15 mL) were added AgClO4
(131 mg, 0.63 mmol), PPh3 (175 mg, 0.67 mmol), and piperidine
(32 µL, 0.32 mmol), and the mixture was stirred for 0.5 h. A bright
yellow precipitate gradually formed, which was filtered off, washed
with MeCN (3 × 3 mL), and vacuum-dried to give 5a. Yield: 286
mg, 83%. Anal. calcd for C156H147Ag6P5S6: C, 62.12; H, 4.91; S,
6.38. Found: C, 61.87; H, 5.07; S, 5.71. Mp: 139 °C (dec). IR (KBr,
3
74.1 (d, JCP ) 36.2 Hz, C2, C5, Cp), 72.5 (m, C3, C4, Cp), 34.9
(CMe3), 31.9 (CMe3). 31P{1H} NMR (162.3 MHz, CDCl3): δ -0.53
1
1
107Ag
109Ag
(quint m, JP-
) 457 Hz, JP-
) 524 Hz, calculated
constants, see text).
[Agn{S2Cd(t-Bu-fy)}n/2{P(i-Pr)3}n] (7). To a solution of 1 (102
mg, 0.21 mmol) in MeCN (15 mL) were added AgClO4 (83 mg,
0.40 mmol), P(i-Pr)3 (82 µL, 0.43 mmol), and piperidine (22 µL,
0.22 mmol), and the mixture was stirred for 1 h. A yellow solid
gradually precipitated, which was filtered off, washed with MeCN
(2 mL), and vacuum-dried to give 7. Yield: 124 mg, 69%. Anal.
calcd for C40H66Ag2P2S2: C, 54.06; H, 7.49; S, 7.22. Found: C,
53.82; H, 7.69; S, 7.16. Mp: 152 °C (dec). IR (KBr, cm-1):
1
ν(CdCS2), 1482. H NMR (300.1 MHz, CDCl3): δ 9.51 (br, 4 H,
1
3
4
cm-1): ν(CdCS2), 1489. H NMR (400.9 MHz, CDCl3): δ 9.28
H1, H8), 7.60 (d, JHH ) 8.0 Hz, 4 H, H4, H5), 7.19 (dd, JHH )
(d, 4JHH ) 1.5 Hz, 6 H, H1, H8), 7.59 (d, 4JHH ) 7.9 Hz, 6 H, H4,
H5), 7.24-7.18 (m, 36 H, H3, H6 + m-H, Ph), 7.12 (m, 30 H,
o-H, Ph), 6.95 (m, 15 H, p-H, Ph), 1.24 (s, 54 H, t-Bu). 13C{1H}
NMR (75.5 MHz, CDCl3): δ 148.2 (C2, C7), 140.5 (C8a, C9a),
136.3 (C4a, C4b), 133.5 (d, 3JCP ) 17.2 Hz, o-C, Ph), 133.2 (C9),
131.7 (d, 1JCP ) 53.4 Hz, i-C, Ph), 129.3 (p-C, Ph), 128.5 (d, 4JCP
) 8.5 Hz, m-C, Ph), 124.7 (C1, C8), 122.2 (C3, C6), 117.1 (C4,
C5), 34.9 (CMe3), 31.8 (CMe3) (CS2 not observed). 31P{1H} NMR
(81.0 MHz, CDCl3): δ 4.9 (br).
1.5 Hz, JHH ) 8.0 Hz, 4 H, H3, H6), 1.94 (m, 12 H, CHMe2),
3
3
3
1.37 (s, 36 H, t-Bu), 1.09 (dd, JHH ) 7.0 Hz, JHP ) 14.4 Hz, 72
H, CHMe2). 13C{1H} NMR (50.1 MHz, CDCl3): δ 147.4 (C2, C7),
141.3 (C8a, C9a), 134.8 (C4a, C4b), 131.8 (C9), 124.5 (C1, C8),
120.2 (C3, C6), 116.7 (C4, C5), 35.0 (CMe3), 32.0 (CMe3), 22.6
(d, 1JCP ) 8.7 Hz, CHMe2), 20.5 (d, JCP ) 5.8 Hz, CHMe2) (CS2
2
not observed). 31P{1H} NMR (162.3 MHz, CDCl3, 213 K): δ 39.8
1
1
107Ag
109Ag
(2 d, JP-
) 460 Hz, JP-
) 530 Hz).
[Ag8{S2Cd(t-Bu-fy)}4{P(i-Pr)3}4] (8). To a solution of AgClO4
(205 mg, 0.99 mmol) and 1 (234 mg, 0.49 mmol) in THF (10 mL)
were added piperidine (49 µL, 0.49 mmol) and P(i-Pr)3 (107 µL,
0.49 mmol). The resulting yellowish orange solution was stirred
for 15 min and concentrated under reduced pressure (4 mL). The
addition of MeCN (20 mL) led to the precipitation of a yellow
[Ag6{S2Cd(t-Bu-fy}3{P(p-To)3}5] (5b). This bright yellow com-
pound was prepared as described for 5a, from 1 (221 mg, 0.46
mmol), AgClO4 (192 mg, 0.92 mmol), P(p-To)3 (290 mg, 0.95
mmol), and piperidine (50 µL, 0.51 mmol). Yield: 454 mg, 91%.
Anal. calcd for C171H177Ag6P5S6: C, 63.65; H, 5.53; S, 5.96. Found:
Inorganic Chemistry, Vol. 48, No. 5, 2009 2063

Vicente et al.
Scheme 1a
a
To ) tolyl; pip ) piperidine; dppe ) 1,2-bis(diphenylphosphino)ethane; dppf ) 1,1′-bis(diphenylphosphino)ferrocene.
solid, which was filtered off, recrystallized from CH2Cl2/MeCN,
and vacuum-dried to give 8. Yield: 300 mg, 84%. Anal. calcd for
precursors with the corresponding piperidinium 9H-fluorene-
9-carbodithioate in the presence of a base. In some cases,
dithioato complexes were obtained when the reactions were
carried out in the absence of a base.18,19
C
124H180Ag8P4S8: C, 51.11; H, 6.23; S, 8.80. Found: C, 51.03; H,
6.26; S, 8.71. Mp: 168 °C (dec). IR (KBr, cm-1): ν(CdCS2), 1496,
1
1464. H NMR (400.9 MHz, CD2Cl2, 203 K): δ 9.22 (s, 4 H, H1,
By reacting dithioate 1 with AgClO4 in a 1:1 molar ratio
in acetone, the red complex [Agn{S2C(t-Bu-Hfy)}n] (2)
precipitated in almost quantitative yield (Scheme 1). The
reactions of this compound with PPh3, 1,2-bis(diphenylphos-
phino)ethane (dppe), or 1,1′-bis(diphenylphosphino)ferrocene
(dppf) in the appropriate molar ratios allowed the preparation
of the tetracoordinated complexes [Ag{S2C(t-Bu-Hfy)}L2]
[L ) PPh3 (3a); L2 ) dppe (3b), dppf (3c)]. Although it
proved impossible to grow crystals of complexes 2 and 3a-c,
their elemental analyses are consistent with a 1:1 dithioato/
silver ratio.
Synthesis of Silver(I) Complexes with the (t-Bu-fy)dCS22-
Ligand. The attempts to obtain anionic complexes with the
dithiolato ligand (t-Bu-fy)dCS22- through the deprotonation
of the dithioato complexes 2 or 3a-c with piperidine or
(Pr4N)OH led in all cases to complicated mixtures. However,
the deprotonation of the dithioato ligand in 2 with piperidine
was successful in the presence of an additional equivalent
of AgClO4, leading to the formation of a neutral complex,
which, according to its elemental analysis, has a 2:1 silver
to dithiolate ratio. An X-ray diffraction study revealed that
the product of this reaction is the dodecanuclear cluster
[Ag12{S2Cd(t-Bu-fy)}6] (4; Scheme 1). This compound can
H8), 9.06, 8.63 (both s, 2 H each, H1, H8), 7.63, 7.59, 7.45, 7.39
(all d, 3JHH ) 8.0 Hz, 2 H each, H4, H5), 7.22, 7.16, 7.12, 6.94 (all
3
d, JHH ) 8.0 Hz, 2 H each, H3, H6), 1.87, 1.63 (both br m, 6 H
each, CHMe2), 1.28, 1.26, 1.24 (all s, 18 H each, t-Bu), 1.03-0.98
(br m, 18 H, CHMe2), 0.84-0.64 (br m, 54 H, CHMe2), 0.51 (s,
18 H, t-Bu). 31P{1H} NMR (162.3 MHz, CDCl3, 203 K): δ 48.6 (2
1
1
1
107Ag
d, JP-
1
109Ag
107Ag
) 521 Hz, JP-
) 594 Hz), 45.2 (2 d, JP-
)
109Ag
477 Hz, JP-
) 549 Hz). Data for isomer 8* (see the NMR
1
section) is as follows. H NMR (400.9 MHz, CD2Cl2, 203 K): δ
9.17 (d, 4JHH ) 1.4 Hz, 2 H, H1, H8), 7.58 (d, 3JHH ) 8.0 Hz, 2 H,
4
3
H4, H5), 7.26 (dd, JHH ) 1.4 Hz, JHH ) 8.0 Hz, 2 H, H3, H6),
1.55 (br m, 3 H, CHMe2), 1.30 (s, 18 H, t-Bu) (CHMe2 signals
overlapped by those from 8). 31P{1H} NMR (162.3 MHz, CDCl3,
1
1
107Ag
109Ag
203 K): δ 50.8 (2 d, JP-
) 543 Hz, JP-
) 626 Hz).
Results and Discussion
Synthesis of Silver(I) Complexes with the (t-Bu-Hfy)CS2-
Ligand. The synthesis of Ag(I) complexes with (t-Bu-
Hfy)CS2- (Chart 1) was undertaken in order to explore their
suitability as precursors for the preparation of complexes with
the dithiolato ligand (t-Bu-fy)dCS22-. As we have shown
in our previous reports, metal complexes with the (fluoren-
9-yliden)methanedithiolato ligand and its 2,7-disubstituted
derivatives can be obtained by reacting appropriate metal
2064 Inorganic Chemistry, Vol. 48, No. 5, 2009

NoWel Types of SilWer Clusters
also be directly obtained from the reaction of dithioate 1
with AgClO4 and piperidine in a 1:2:1 molar ratio in THF.
We then attempted the direct synthesis of neutral Ag(I)
complexes with (t-Bu-fy)dCS22- and phosphine ligands by
reacting dithioate 1 with AgClO4, phosphines, and piperidine
in a molar ratio of 1:2:2:1 in MeCN. These reactions afforded
neutral clusters of various nuclearities, depending on the
nature of the phosphine. When PPh3 or P(p-To)3 (To ) tolyl)
was employed, the hexanuclear clusters [Ag6{S2Cd(t-Bu-
fy)}3L5], where L ) PPh3 (5a) or P(p-To)3 (5b), were isolated
in high yields as bright yellow precipitates. The elemental
analyses of 5a and 5b are consistent with a 6:3:5 silver/
dithiolate/phosphine ratio, which was confirmed for 5b by
means of an X-ray single-crystal structure analysis (see
below). Complexes 5a and 5b are only moderately stable in
solution, and they slowly lose phosphine. When the com-
plexes are stirred in distilled THF for 48 h, the dodecanuclear
cluster 4 eventually forms. The formation of 4 from 5a,b
requires the presence of atmospheric oxygen and also
requires that the solvent be free of peroxide inhibitors, which
suggests that the oxidation of the dissociated phosphine is
crucial for the transformation to occur. This process is
reversible, and the reaction of 4 with PPh3 or PTo3 in a 1:12
molar ratio gave complex 5a or 5b, respectively.
The reaction of 1 with AgClO4, dppf, and piperidine in a
1:2:1:1 molar ratio in MeCN afforded the tetranuclear
derivative [Ag4{S2Cd(t-Bu-fy)}2(dppf)2] (6) as a yellow
precipitate. Alternatively, compound 6 can be obtained by
reacting cluster 4 with dppf in a 1:6 molar ratio in CH2Cl2.
In contrast to 5a and 5b, complex 6 exhibits a remarkable
stability in solution, even under atmospheric conditions. Its
nuclearity was established from the 31P{1H} NMR data (see
the NMR section).
By reacting 1 with AgClO4, P(i-Pr)3, and piperidine in a
1:2:2:1 molar ratio in MeCN, a compound with the stoichi-
ometry [Agn{S2Cd(t-Bu-fy)}n/2{P(i-Pr)3}n] (7) was obtained
as a yellow precipitate. Complex 7 can also be prepared from
the reaction of 4 with P(i-Pr)3 in a 1:12 molar ratio. The
nuclearity of 7 could not be unequivocally established (see
the NMR section). Complex 7 is moderately labile in
solution, and it slowly decomposes, giving a complicated
mixture. One of the decomposition products is the octa-
nuclear cluster [Ag8{S2Cd(t-Bu-fy)}4{P(i-Pr)3}4] (8), which
results from the loss of n/2 equiv of P(i-Pr)3 from 7.
Compound 8 crystallized in an attempt to obtain crystals of
7 from CH2Cl2/MeCN and was structurally characterized by
means of an X-ray diffraction study; it can be independently
obtained in high yield by reacting a solution of 4 in THF
with P(i-Pr)3 in a 1:6 molar ratio.
161.00(7)°; S(4)-Ag(11)-S(12), 154.68(8)°]. The Ag-S
distances lie in the range 2.373-2.428 Å and are normal
for dicoordinated silver thiolato complexes.1,24 The molecule
can be viewed as two interlocked Ag6S6 macrocycles, held
together by the C atoms of the CS2 moieties. If we consider
linear S-Ag-S segments, the shape of each of the macro-
cycles resembles the twist-boat conformation of cyclohexane
(Figure 2). The cluster has approximate D2 symmetry, with
one pseudo-2-fold axis passing through the Ag(11), Ag(1),
Ag(2), and Ag(8) atoms; a second axis through the C(104)
and C(134) atoms; and a third axis through the midpoint of
the Ag(1)-Ag(2) segment. The shape of the Ag12 core is
rather flat, with eight of the Ag atoms [Ag(1), Ag(2), and
Ag(7-12)] being almost coplanar (mean deviation from
plane: 0.068 Å), while the other four make up a slightly
twisted rectangle (main deviation from plane: 0.267 Å),
perpendicular to the Ag8 mean plane (Figure 3). There are
21 Ag · · ·Ag metallophilic contacts in the range 2.875-3.367
Å, which, in view of the low coordination number of the
Ag atoms, must play a crucial role in the stabilization of the
cluster. Notably, the innermost metal centers, Ag(1) and
Ag(2), establish a total of eight contacts with neighboring
Ag atoms, while the rest of metals are involved in one to
four Ag· · · Ag contacts.
The crystal structure of 5b, which has no imposed
symmetry (Figure 4, Table 3), reveals that three of the Ag
atoms [Ag(2), Ag(3), Ag(4)] have trigonal AgS2P coordina-
tion, while the others are in trigonal AgS3 [Ag(1)], linear
AgS2 [Ag(5)], or tetrahedral AgS2P2 [Ag(6)] environments.
Five of the S atoms are doubly bridging, while S(2) is triply
bridging. The Ag-S bond distances range from 2.382 to
2.798 Å, the shortest corresponding to the linearly coordi-
nated Ag(5) atom. The Ag6S6 core as depicted in Figure 4
has very approximate mirror symmetry, although the distance
Ag(1)-S(1) is too long (4.228 Å). There are six short
Ag · · · Ag metallophilic contacts in the range 2.886-3.143
Å. As far as we are aware, the arrangement of the silver
atoms has no precedent in other silver thiolato complexes.
The complex [Ag6(SC6H4Cl-p)6(PPh3)5] has the same Ag/
S/P ratio, but the Ag6S6 core has a very different structure,
with one doubly bridging and five triply bridging S atoms.25
The molecular structure of compound 8, which displays
crystallographic 2-fold symmetry [the axis passes through
Ag(1) and Ag(2)], is represented in Figures 5 and 6. Selected
bond distances and angles are listed in Table 4. As observed
for 4, all of the dithiolates act as quadruply bridging ligands.
The Ag(1) atom is in a distorted tetrahedral AgS4 environ-
(24) (a) Block, E.; Gernon, M.; Kang, H. K.; Oforiokai, G.; Zubieta, J.
Inorg. Chem. 1989, 28, 1263. (b) Chen, J. X.; Xu, Q. F.; Zhang, Y.;
Chen, Z. N.; Lang, J. P. J. Organomet. Chem. 2004, 689, 1071. (c)
Dance, I. G.; Fitzpatrick, L. J.; Craig, D. C.; Scudder, M. L. Inorg.
Chem. 1989, 28, 1853. (d) Dance, I. G.; Fitzpatrick, L. J.; Rae, A. D.;
Scudder, M. L. Inorg. Chem. 1983, 22, 3785. (e) Fujisawa, K.; Imai,
S.; Moro-oka, Y. Chem. Lett. 1998, 167. (f) Li, J. R.; Li, Z. H.; Du,
S. W.; Wu, X. T. Polyhedron 2005, 24, 481. (g) Sampanthar, J. T.;
Vittal, J. J.; Dean, P. A. W. J. Chem. Soc., Dalton Trans. 1999, 3153.
(h) Tang, K.; Aslam, M.; Block, E.; Nicholson, T.; Zubieta, J. Inorg.
Chem. 1987, 26, 1488. (i) Tang, K.; Yang, J. P.; Yang, Q. C.; Tang,
Y. J. Chem. Soc., Dalton Trans. 1989, 2297.
Crystal Structures. The crystal structure of the dodeca-
nuclear cluster 4 is shown in Figure 1; it displays no imposed
crystallographic symmetry. Selected bond distances and
angles are listed in Table 2. Each of the six dithiolates acts
as a bridging ligand toward four Ag atoms. All 12 metal
centers are in approximately linear coordination environ-
ments, with S-Ag-S angles in the range 154.68-176.84°;
the most appreciable deviations from linearity are observed
for the Ag(11) and Ag(8) atoms [S(6)-Ag(8)-S(1),
(25) Dance, I. G.; Fitzpatrick, L. J.; Scudder, M. L. Inorg. Chem. 1984,
23, 2276.
Inorganic Chemistry, Vol. 48, No. 5, 2009 2065

Vicente et al.
Figure 1. Thermal ellipsoid representation (30% probability; isotropic light atoms as spheres) of the structure of complex 4. H atoms and t-Bu groups have
been omitted for clarity.
carbon atoms of the dithioato ligand slightly modified with
respect to those of the free dithioate 1,22 with the H9
resonance in the range of 5.64-5.78 ppm and the CS2
resonance around 259 ppm. The NMR data of 2 suggest a
highly symmetrical, oligomeric structure for this complex.
The polymeric [Agn(S2C-o-To)n]26 is comprised of repeating
tetranuclear subunits (Chart 2, a), and some pyridine adducts
of Ag(I) dithiobenzoates, such as [Ag4(S2CMes)4(py)3] and
[Ag4(S2C-o-To)4(py)4]27 (Mes ) mesityl; To ) tolyl; b and
c, respectively), as well as the related [Ag4{S2CC-
(PPh3)2}4]4+ (d),28 are tetranuclear species. The 1H NMR data
of complexes 3a-c are compatible with mononuclear
Figure 2. Perspective view of one of the Ag6S6 macrocycles in the structure
of 4 (thermal ellipsoids with 50% probability).
structures with tetrahedral coordination around silver. Their
31P{1H} NMR spectra display the resonance arising from
ment, with S-Ag-S angles in the range 90.07-141.10°.
the phosphines as somewhat broad singlets at room temper-
ature, which is attributable to phosphine dissociation and
exchange processes in solution.29 For this reason, we
measured the 31P{1H} NMR spectra at low temperatures,
The Ag(2), Ag(4), and Ag(5) atoms are in approximately
linear environments, the first two with AgS2 coordination
and the third with AgSP coordination. The Ag(3) atom is in
a distorted trigonal AgS2P coordination. The Ag-S bond
distances lie in the range 2.381-2.688 Å, the shortest being
associated with the linearly coordinated Ag(2), Ag(4), and
Ag(5) atoms. The molecule displays a total of 11 Ag · · · Ag
short contacts in the range 2.835-3.258 Å.
(26) Lanfredi, A. M. M.; Ugozzoli, F.; Camus, A.; Marsich, N. J. Chem.
Cryst. 1995, 25, 37.
(27) Schuerman, J. A.; Fronczek, F. R.; Selbin, J. Inorg. Chim. Acta 1989,
160, 43.
(28) Petz, W.; Neumuller, B.; Krossing, I. Z. Anorg. Allg. Chem. 2006,
632, 859.
(29) (a) Lanfredi, A. M. M.; Ugozzoli, F.; Asaro, F.; Pellizer, G.; Marsich,
N.; Camus, A. Inorg. Chim. Acta 1991, 190, 71. (b) Muetterties, E. L.;
Alegranti, C. W. J. Am. Chem. Soc. 1972, 94, 6386.
NMR Spectra, Solution Structure, and Dynamic
Behavior. The 1H and 13C{1H} NMR spectra of complexes
2 and 3a-c show one set of signals for the protons and
2066 Inorganic Chemistry, Vol. 48, No. 5, 2009

NoWel Types of SilWer Clusters
Table 2. Selected Bond Distances (Å) and Angles (deg) for 4
Ag(1)-S(3)
2.4185(19) Ag(6)-S(8)
2.428(2) Ag(6)-S(5)
2.382(2)
2.4156(19)
2.9098(8)
2.373(2)
2.375(2)
2.394(2)
2.396(2)
2.409(2)
2.410(2)
2.380(2)
2.388(2)
3.2871(10)
2.419(2)
2.427(2)
2.403(2)
2.405(2)
1.788(8)
1.785(8)
1.784(8)
1.776(8)
1.771(7)
1.783(7)
1.793(8)
1.785(8)
1.792(8)
1.776(8)
1.777(8)
1.784(8)
Ag(1)-S(11)
Ag(1)-Ag(11)
Ag(1)-Ag(12)
Ag(1)-Ag(5)
Ag(1)-Ag(10)
Ag(1)-Ag(4)
Ag(1)-Ag(3)
Ag(1)-Ag(2)
Ag(1)-Ag(6)
Ag(2)-S(2)
2.9338(10) Ag(6)-Ag(9)
3.0113(10) Ag(7)-S(10)
3.0303(8) Ag(7)-S(1)
3.0494(9) Ag(8)-S(6)
3.1071(8) Ag(8)-S(1)
3.2660(8) Ag(9)-S(6)
3.2999(8) Ag(9)-S(7)
3.3669(9) Ag(10)-S(4)
2.4077(18) Ag(10)-S(8)
2.4099(18) Ag(10)-Ag(11)
2.8747(8) Ag(11)-S(4)
3.0144(8) Ag(11)-S(12)
3.0318(8) Ag(12)-S(9)
3.0404(8) Ag(12)-S(12)
3.0649(8) S(1)-C(14)
3.2912(8) S(2)-C(14)
3.3658(8) S(3)-C(44)
Ag(2)-S(5)
Ag(2)-Ag(8)
Ag(2)-Ag(6)
Ag(2)-Ag(3)
Ag(2)-Ag(9)
Ag(2)-Ag(7)
Ag(2)-Ag(4)
Ag(2)-Ag(5)
Ag(3)-S(9)
2.387(2)
S(4)-C(44)
Ag(3)-S(2)
2.4165(19) S(5)-C(74)
2.8865(8) S(6)-C(74)
3.2800(9) S(7)-C(104)
Ag(3)-Ag(7)
Ag(3)-Ag(12)
Ag(4)-S(10)
Ag(4)-S(11)
Ag(4)-Ag(12)
Ag(5)-S(7)
2.389(2)
2.410(2)
2.8991(9) S(10)-C(134)
S(8)-C(104)
S(9)-C(134)
Figure 3. The Ag12 cluster in the structure of 4. The Ag · · ·Ag contacts in
the range 2.875-3.367 Å are represented as banded cylinders. Longer
Ag-Ag distances are represented by dashed lines. Thermal ellipsoids at
50% probability.
2.405(2)
2.427(2)
2.8984(8)
S(11)-C(164)
S(12)-C(164)
Ag(5)-S(3)
atoms give rise to a broad signal centered at 144.2 ppm,
probably as a consequence of unresolved Ag-C couplings.
The present NMR data indicate that the structure of 4 is
essentially nonfluxional in solution.
Ag(5)-Ag(10)
S(3)-Ag(1)-S(11)
S(2)-Ag(2)-S(5)
S(9)-Ag(3)-S(2)
175.12(8) C(74)-S(5)-Ag(2)
176.08(7) C(74)-S(5)-Ag(6)
168.69(7) Ag(2)-S(5)-Ag(6)
106.6(2)
103.9(3)
77.32(6)
103.2(3)
106.9(3)
92.47(7)
105.1(3)
108.8(3)
91.91(7)
108.2(3)
S(10)-Ag(4)-S(11) 172.32(7) C(74)-S(6)-Ag(8)
1
S(7)-Ag(5)-S(3)
S(8)-Ag(6)-S(5)
S(10)-Ag(7)-S(1)
S(6)-Ag(8)-S(1)
S(6)-Ag(9)-S(7)
S(4)-Ag(10)-S(8)
172.74(7) C(74)-S(6)-Ag(9)
170.78(7) Ag(8)-S(6)-Ag(9)
176.82(7) C(104)-S(7)-Ag(5)
161.00(7) C(104)-S(7)-Ag(9)
173.04(7) Ag(5)-S(7)-Ag(9)
170.40(8) C(104)-S(8)-Ag(6)
The room-temperature H NMR spectra of the dithiolato
complexes 5a and 5b show only one resonance for the t-Bu
substituents and each of the pairs of aromatic protons H1/
H8, H3/H6, and H4/H5 of the fluoren-9-ylidene groups.
These data are thus indicative of structures with equivalent
and symmetrical dithiolato ligands in solution. However, in
view of the crystal structure of 5b, it is clear that complex
dynamic processes take place, which result in the interchange
of coordination environments between all of the silver atoms
and eventually make the dithiolato ligands equivalent on the
NMR time scale. The room-temperature 31P{1H} NMR
spectra of 5a and 5b show a very broad resonance, which is
also indicative of exchange processes. Unfortunately, the 1H
and 31P{1H} NMR spectra of 5a,b could not be measured at
low temperatures because of their very low solubilities.
The 1H NMR data of the dppf complex 6 are also
indicative of a structure with symmetrical and equivalent
dithiolato ligands. It is therefore striking that its 31P{1H}
NMR spectrum at room temperature displays the resonance
corresponding to the P atoms of the PPh2 groups as a
quintuplet of apparent quintuplets, with almost constant
spacings of 122.4 and 8.7 Hz (Figure 7). If the structure of
6 in solution was regular, all of the P atoms would be
equivalent, and therefore only one resonance should be
observed, which would appear as two doublets because of
the coupling with the 107Ag and 109Ag isotopes. The observed
multiplicity suggests that 6 undergoes a very fast dynamic
process in solution by means of which the P atoms exchange
their positions. To confirm this possibility, we measured the
31P{1H} NMR spectra of 6 at different temperatures, which
show that the quintuplet broadens as the temperature
decreases. However, the complex is scarcely soluble below
S(4)-Ag(11)-S(12) 154.68(8) C(104)-S(8)-Ag(10) 101.3(3)
S(9)-Ag(12)-S(12) 176.75(8) Ag(6)-S(8)-Ag(10)
90.58(8)
110.2(3)
C(14)-S(1)-Ag(7)
C(14)-S(1)-Ag(8)
Ag(7)-S(1)-Ag(8)
C(14)-S(2)-Ag(2)
C(14)-S(2)-Ag(3)
Ag(2)-S(2)-Ag(3)
C(44)-S(3)-Ag(1)
C(44)-S(3)-Ag(5)
Ag(1)-S(3)-Ag(5)
106.1(2)
99.7(3)
C(134)-S(9)-Ag(3)
C(134)-S(9)-Ag(12) 99.6(3)
96.03(7)
105.7(2)
103.9(3)
77.87(5)
104.7(2)
104.9(3)
77.41(6)
Ag(3)-S(9)-Ag(12) 86.43(7)
C(134)-S(10)-Ag(7) 105.7(3)
C(134)-S(10)-Ag(4) 106.1(3)
Ag(7)-S(10)-Ag(4)
91.08(7)
C(164)-S(11)-Ag(4) 105.6(3)
C(164)-S(11)-Ag(1) 103.3(3)
Ag(4)-S(11)-Ag(1)
79.91(6)
C(44)-S(4)-Ag(10) 111.2(3)
C(44)-S(4)-Ag(11) 101.9(3)
Ag(10)-S(4)-Ag(11) 86.47(7)
C(164)-S(12)-Ag(12) 106.7(3)
C(164)-S(12)-Ag(11) 96.1(3)
Ag(12)-S(12)-Ag(11) 106.28(8)
which allowed observation of the Ag-P couplings (see the
Experimental Section).
1
The H and 13C NMR data of cluster 4 are in agreement
with its solid-state structure. Thus, its D2 symmetry in
solution leads to two types of dithiolato ligands, labeled as
A and B in Scheme 1. The two type-A ligands lie along one
of the 2-fold axes and thus give rise to one signal for the
t-Bu groups in the 1H NMR spectrum, while the four type-B
ligands do not contain equivalent atoms and give rise to two
different signals for the t-Bu groups. The three signals of
equal intensity observed for each of the pairs of aromatic
protons H1/H8, H3/H6, and H4/H5 (see Chart 1 for the atom
numbering) are explained in the same manner. The 13C NMR
spectrum of 4 shows the expected two signals for the C9
atoms of the t-Bu-fy groups at 135.2 and 134.9 ppm, with
relative intensities of approximately 2:1, while the CS2 carbon
Inorganic Chemistry, Vol. 48, No. 5, 2009 2067

Vicente et al.
Figure 4. Thermal ellipsoid representation (50% probability) of complex 5b. H atoms and t-Bu and p-To groups have been omitted for clarity.
Table 3. Selected Bond Distances (Å) and Angles (deg) for 5b
phosphorus atoms exchange their positions through the
migration around a square Ag4 core (Figure 7) confirmed
that the room-temperature 31P{1H} NMR spectrum of 6 is
the result of a dynamic process. The spacing between the
Ag(1)-S(3)
2.4242(12)
2.5066(13)
2.6495(13)
2.8857(6)
2.9790(5)
3.1429(5)
2.4304(15)
2.5289(13)
2.5690(13)
2.3896(15)
2.4858(13)
2.6709(13)
3.1359(6)
2.4226(13)
2.4822(13)
2.5518(13)
2.9803(5)
148.34(4)
122.22(4)
82.60(4)
82.97(3)
93.04(3)
134.05(3)
71.47(3)
139.38(3)
72.41(3)
120.00(5)
128.12(5)
111.25(4)
148.04(6)
126.83(5)
82.55(4)
139.41(4)
105.69(4)
114.88(4)
165.87(4)
122.27(5)
101.82(4)
110.91(4)
114.58(4)
Ag(5)-S(1)
Ag(5)-S(4)
Ag(5)-Ag(6)
Ag(6)-P(5)
Ag(6)-P(4)
Ag(6)-S(3)
Ag(6)-S(1)
S(1)-C(10)
S(2)-C(10)
S(3)-C(30)
S(4)-C(30)
S(5)-C(50)
S(6)-C(50)
C(9)-C(10)
C(29)-C(30)
C(49)-C(50)
2.3823(13)
2.4058(13)
2.9410(5)
2.4646(14)
2.4879(14)
2.6581(13)
2.7975(13)
1.765(5)
1.780(5)
1.768(5)
1.780(5)
1.779(5)
Ag(1)-S(5)
Ag(1)-S(2)
Ag(1)-Ag(2)
Ag(1)-Ag(5)
peaks of the main quintuplet approximately corresponds to
Ag(1)-Ag(4)
1
107Ag
one-quarter of the mean of the coupling constants JP-
Ag(2)-P(1)
1
Ag(2)-S(6)
109
and JP-
and therefore can be interpreted as an average
Ag
Ag(2)-S(4)
coupling of each of the P atoms with four Ag atoms. The
further splitting into apparent quintuplets is attributable to
the superposition of the spectra of the different isotopomers.
A related process has been reported for the hexanuclear
derivatives [Ag6(EAr)4(dppm)](PF6)2 [EAr ) SPh, S(p-To),
SePh, or SeC6H4Me-p; dppm ) bis(diphenylphosphi-
no)methane], which led to the observation of a septuplet in
the 31P{1H} NMR spectra at high temperatures, although in
these cases, the splittings associated with the different
isotopomers did not resolve.30 The present 31P{1H} NMR
data prove that the dynamic process is intramolecular and
are also an unequivocal demonstration that 6 is tetranuclear.
In addition, since the Ag-P couplings are observed at room
temperature, they reveal that the dppf ligands do not
dissociate easily, which is consistent with the high stability
observed for this complex in solution. We note that tetra-
nuclear structures have been found for other silver(I)
dithiolato complexes such as [Ag4(i-mnt)2(dppm)4]15 and
[Ag4(cpdt)2(dppm)4]16 (cpdt ) {(EtO)2P(O)}(CN)CdCS22-),
which have their metal atoms in a nearly planar arrangement
and the dithiolato ligands acting as quadruply bridging
ligands above and below the Ag4 core. Complex 6 probably
has an analogous structure, but with only two diphosphine
ligands instead of four (Scheme 1).
Ag(3)-P(2)
Ag(3)-S(5)
Ag(3)-S(2)
Ag(3)-Ag(4)
1.770(5)
1.350(7)
1.375(7)
1.367(7)
Ag(4)-P(3)
Ag(4)-S(2)
Ag(4)-S(6)
Ag(4)-Ag(5)
S(3)-Ag(1)-S(5)
S(3)-Ag(1)-S(2)
S(5)-Ag(1)-S(2)
S(3)-Ag(1)-Ag(2)
S(5)-Ag(1)-Ag(2)
S(2)-Ag(1)-Ag(2)
S(3)-Ag(1)-Ag(5)
S(5)-Ag(1)-Ag(5)
S(2)-Ag(1)-Ag(5)
P(1)-Ag(2)-S(6)
P(1)-Ag(2)-S(4)
S(6)-Ag(2)-S(4)
P(2)-Ag(3)-S(5)
P(2)-Ag(3)-S(2)
S(5)-Ag(3)-S(2)
P(3)-Ag(4)-S(2)
P(3)-Ag(4)-S(6)
S(2)-Ag(4)-S(6)
S(1)-Ag(5)-S(4)
P(5)-Ag(6)-P(4)
P(5)-Ag(6)-S(3)
P(4)-Ag(6)-S(3)
P(5)-Ag(6)-S(1)
P(4)-Ag(6)-S(1)
S(3)-Ag(6)-S(1)
C(10)-S(1)-Ag(5)
C(10)-S(1)-Ag(6)
Ag(5)-S(1)-Ag(6)
C(10)-S(2)-Ag(4)
C(10)-S(2)-Ag(1)
Ag(4)-S(2)-Ag(1)
C(10)-S(2)-Ag(3)
Ag(4)-S(2)-Ag(3)
Ag(1)-S(2)-Ag(3)
C(30)-S(3)-Ag(1)
C(30)-S(3)-Ag(6)
Ag(1)-S(3)-Ag(6)
C(30)-S(4)-Ag(5)
C(30)-S(4)-Ag(2)
Ag(5)-S(4)-Ag(2)
C(50)-S(5)-Ag(3)
C(50)-S(5)-Ag(1)
Ag(3)-S(5)-Ag(1)
C(50)-S(6)-Ag(2)
C(50)-S(6)-Ag(4)
Ag(2)-S(6)-Ag(4)
92.87(4)
115.15(4)
108.41(17)
99.02(16)
68.65(3)
105.64(16)
126.64(17)
75.45(4)
140.55(16)
74.87(4)
92.21(4)
109.75(16)
110.16(16)
90.81(4)
96.68(15)
89.16(16)
102.28(5)
94.82(16)
100.91(17)
100.34(5)
100.85(16)
109.30(18)
105.60(5)
233 K in CD2Cl2, and we could not obtain well-resolved
spectra (see the Supporting Information for details). A
computer simulation of a (P-Ag)4 system in which the
(30) Yam, V. W. W.; Cheng, E. C. C.; Zhu, N. Y. New J. Chem. 2002, 26,
279.
2068 Inorganic Chemistry, Vol. 48, No. 5, 2009

NoWel Types of SilWer Clusters
Figure 5. Thermal ellipsoid representation (50% probability) of complex 8. H atoms and t-Bu and i-Pr groups have been omitted for clarity.
Chart 2
Figure 6. Perspective view of the Ag8S8P4 core of complex 8. Thermal
ellipsoids at 50% probability.
Complex 7 gives rise to a very simple 1H NMR spectrum
at room temperature, which is indicative of symmetrical and
equivalent dithiolato ligands, while the 31P{1H} NMR
spectrum shows a broad resonance at 41.7 ppm (CDCl3).
1
On cooling down to 213 K, the H NMR spectrum showed
no significant changes, while the 31P{1H} NMR spectrum
showed two doublets arising from equivalent [Ag{P(i-Pr)3}]+
units, thus revealing that this complex has a regular structure.
A tetranuclear structure similar to that proposed for 6 would
be consistent with the NMR data, but it could not be
unequivocally established.
The room-temperature H NMR spectrum of compound
8 shows broad signals for the protons of both the dithiolate
and the phosphine that are not consistent with the structure
found in the solid state. The aromatic region of the 1H NMR
spectra in CD2Cl2 at temperatures between 203 and 296 K
is shown in Figure 8. At 273 K, the resonances sharpen and
reveal the presence of two different species, each one giving
1
Inorganic Chemistry, Vol. 48, No. 5, 2009 2069

Vicente et al.
Figure 8. 1H NMR spectra of complex 8 in CD2Cl2 at different temperatures
(aromatic region). The resonances corresponding to the isomeric species
8* have been labeled with an asterisk.
set undergoes a minor shift to lower frequencies and a drastic
decrease in relative intensity. The resonances of the major
species at 203 K are consistent with the structure found for
8 in the solid state, which contains two types of dithiolato
ligands, neither of which have equivalent protons, thus giving
rise to four signals for each of the H1/H8, H3/H6, and H4/
H5 pairs. The other set of resonances must correspond to an
isomeric species (8*), which, as deduced from the integration
of its signals, has the same Ag/dithiolate/phosphine ratio as
8. We have labeled these signals with an asterisk in Figure
8. In the 0-2 ppm region, four resonances are observed for
Figure 7. (a) Experimental 31P{1H} NMR spectrum of 6 in CD2Cl2 at 298
K. (b) Simulated 31P NMR spectrum for a (P-Ag)4 system in which the P
atoms migrate around a square Ag4 core (1JP- Ag ) 457 Hz, k ) 107 s-1).
107
Table 4. Selected Bond Distances (Å) and Angles (deg) for 8
Ag(1)-S(1)
Ag(1)-S(3)
Ag(1)-Ag(2)
Ag(1)-Ag(4)
Ag(2)-S(4)
Ag(2)-Ag(4)
Ag(2)-Ag(3)
Ag(4)-Ag(5)
Ag(3)-P(1)
Ag(3)-S(3)
Ag(3)-S(2)#1
2.5715(6)
2.6880(6)
2.8345(4)
2.9507(2)
2.4423(6)
3.0979(2)
3.2584(2)
2.9085(3)
2.3946(7)
2.4576(6)
2.6564(6)
Ag(3)-Ag(4)#1
Ag(4)-S(4)
Ag(4)-S(2)
Ag(5)-P(2)
Ag(5)-S(1)
S(1)-C(10)
2.8464(2)
2.3946(6)
2.4038(6)
2.3697(7)
2.3807(6)
1.774(2)
1.770(2)
1.773(2)
1.779(2)
1.364(3)
1.362(3)
113.32(7)
91.000(19)
104.78(8)
1
the t-Bu groups of 8, while 8* gives only one. The H and
31P{1H} NMR spectra also show the resonances of the two
different P(i-Pr)3 ligands expected for 8, while the isomer
8* contains only one type of P(i-Pr)3 ligand (see the
Supporting Information). In conclusion, the present NMR
data show that (a) complex 8 is in equilibrium with an
isomeric species (8*) in solution, (b) the relative concentra-
tion of isomer 8* decreases with the temperature, (c) complex
8 undergoes a dynamic process leading to equivalent and
symmetrical dithiolates and equivalent phosphines above 273
K on the NMR time scale, and (d) isomer 8* has a regular
structure with equivalent dithiolates and phosphines. How-
ever, the nuclearity of 8* cannot be inferred from its NMR
data.
S(2)-C(10)
S(3)-C(30)
S(4)-C(30)
C(9)-C(10)
C(29)-C(30)
C(10)-S(1)-Ag(1)
S(1)#1-Ag(1)-S(1) 90.07(3)
S(1)-Ag(1)-S(3)#1 92.914(18) Ag(5)-S(1)-Ag(1)
S(1)-Ag(1)-S(3)
114.824(18) C(10)-S(2)-Ag(4)
S(3)#1-Ag(1)-S(3) 141.10(3)
C(10)-S(2)-Ag(3)#1 106.88(8)
S(1)-Ag(1)-Ag(2) 134.965(14) Ag(4)-S(2)-Ag(3)#1 68.250(16)
S(3)-Ag(1)-Ag(2) 70.549(13) C(30)-S(3)-Ag(3)
99.69(8)
S(4)#1-Ag(2)-S(4) 167.78(3)
P(1)-Ag(3)-S(3) 142.42(2)
P(1)-Ag(3)-S(2)#1 116.07(2)
C(30)-S(3)-Ag(1)
Ag(3)-S(3)-Ag(1)
C(30)-S(4)-Ag(4)
118.95(8)
95.603(19)
101.08(7)
98.03(8)
S(3)-Ag(3)-S(2)#1 101.492(19) C(30)-S(4)-Ag(2)
S(4)-Ag(4)-S(2)
P(2)-Ag(5)-S(1)
156.36(2)
175.43(3)
C(10)-S(1)-Ag(5) 104.15(8)
Ag(4)-S(4)-Ag(2)
S(2)-C(10)-S(1)
S(3)-C(30)-S(4)
79.646(18)
117.55(13)
115.49(12)
IR Spectra. The solid-state infrared spectrum of the
dithioato complex 2 shows a band at 1020 cm-1 assignable
to one of the ν(CS2) modes. For the phosphino complexes
3a-c, this band is observed at around 1010 cm-1. These
values are slightly lower than those observed for other silver
dithioato complexes.32
rise to a single set of resonances for the pairs of equivalent
aromatic protons, H1/H8, H3/H6, and H4/H5 (see Chart 1
for the atom numbering). As the temperature decreases, one
of the sets broadens again and at 203 K resolves into four
resonances for each of the pairs of protons,31 while the other
The dithiolato complexes 5a,b, 6, and 7 give rise to an
intense band between 1485 and 1489 cm-1, assignable to
(31) For the H1/H8 protons, three signals are observed, one of them of
double intensity.
(32) Marsich, N.; Pellizer, G.; Camus, A.; Lanfredi, A. M. M.; Ugozzoli,
F. Inorg. Chim. Acta 1990, 169, 171.
2070 Inorganic Chemistry, Vol. 48, No. 5, 2009

NoWel Types of SilWer Clusters
Table 5. Electronic Absorption Data for Compounds 2-8 in CH2Cl2
Solution (ca. 5 × 10-5 M) at 298 K (λ > 330 nm)
Conclusions
compd
λ
max/nm (ε/M-1 cm-1
)
A series of neutral silver complexes with 2,7-di-tert-butyl-
9H-fluorene-9-carbodithioate and (2,7-di-tert-butylfluoren-
9-ylidene)methanedithiolate have been prepared, including
tetra-, hexa-, octa-, and dodecanuclear clusters. The com-
pound [Ag12{S2Cd(t-Bu-fy)}6] (4) is the first neutral homo-
leptic 1,1-ethylenedithiolato silver complex, and its structure
has no precedent in the chemistry of silver 1,1-dithiolates.
Complex 4 is a useful starting material for the preparation
of dithiolato complexes of silver with phosphine ligands. The
compounds [Ag6{S2Cd(t-Bu-fy)}3L5] [L ) PPh3 (5a), P(p-
To)3 (5b)], [Ag4{S2Cd(t-Bu-fy)}2(dppf)2] (6), [Agn{S2Cd(t-
Bu-fy)}n/2{P(i-Pr)3}n] (7), and [Ag8{S2Cd(t-Bu-fy)}4{P(i-
Pr)3}4] (8) also represent new types of silver clusters
containing dithiolato and phosphine ligands. Compounds
5a,b and 7 undergo phosphine dissociation and exchange
processes in solution. Complex 6 undergoes a very fast
dynamic process leading to an average coupling of each of
the P atoms of the dppf ligands with four Ag atoms. The
octanuclear derivative 8 is in equilibrium with a structural
isomer in solution, but the nuclearity and structure of the
latter could not be established. Complex 8 also undergoes a
dynamic process leading to equivalent and symmetrical
dithiolates and equivalent phosphines in solution. In contrast
to the phosphine derivatives, the dodecanuclear cluster 4 does
not exhibit fluxional behavior in solution.
2
347 (6000)
359 (6800)
356 (6900)
353 (4400)
363 (136600)
375 (59000)
395 (60500)
418 (34600)
386 (40900)
386 (100100)
3a
3b
3c
4
5a
5b
6
7
8
the ν(CdCS2) mode, while for 4 and 8, two bands are
observed at 1503 and 1473 cm-1 and 1496 and 1464 cm-1,
respectively. These values are comparable to those found
2-
for neutral Au(I) complexes with the (t-Bu-fy)dCS2
ligand.18
Electronic Absorption Spectra. The UV-visible absorp-
tion spectra of compounds 2-8 were measured in the range
200-700 nm in CH2Cl2 at 298 K. All of them show intense
bands at around 230, 250-270, and 300 nm arising from
the aromatic part of the dithioato or dithiolato ligands.18,19
The absorptions with λ > 330 nm are listed in Table 5. The
dithioato complexes 2 and 3a-c give rise to a relatively weak
band in the range 347-359 nm. This absorption is only
slightly modified with respect to that observed for the free
dithioate 1 (346 nm), which can be ascribed to n-π*
transitions within the CS2 group.18 The spectra of the
dithiolato complexes 4-8 show a broad and intense band in
the range 363-418 nm. The energies and relatively large
molar extinction coefficients observed for this band are
typical of the π-π* transitions associated with the CdCS2
moiety of the (2,7-di-tert-butylfluoren-9-ylidene)methanedithi-
olato ligand.11 As expected, the molar extinction coefficients
are larger for the clusters with a higher number of dithiolates
per molecule (4 and 8). The molar extinction coefficient for
complex 7 was calculated assuming a tetranuclear formula-
tion and fits well within the observed values, although it
cannot be considered as a confirmation of the proposed
nuclearity.
Acknowledgment. We thank Ministerio de Educacio´n y
Ciencia (Spain), FEDER (CTQ2004-05396 and CTQ2007-
60808/BQU), for financial support. Y.G.-S. thanks Ministerio
de Educacio´n y Ciencia (Spain) for a grant.
Supporting Information Available: Crystallographic data in
1
CIF format for 4, 5b, and 8; H NMR spectrum of 4; variable-
temperature 31P{1H} NMR spectra of 6; simulations of the 31P NMR
spectra of a (P-Ag)4 system at different rate constants; variable-
1
temperature H and 31P{1H} NMR spectra of 8. This material is
available free of charge via the Internet at http://pubs.acs.org.
IC802045J
Inorganic Chemistry, Vol. 48, No. 5, 2009 2071