Synthesis, structural characterization, and ligand replacement reactions of gem-dithiolato-bridged rhodium and iridium complexes

Article abstract of DOI:10.1021/ic800464p

The reaction of gem-dithiol compounds R₂C(SH)₂ (R = Bn (benzyl), ⁱPr; R₂ = -(CH₂J₄-) with dinuclear rhodium or iridium complexes containing basic ligands such as [M(μ-OH)(cod)]₂ and [M(μ-OMe)(cod)]₂, or the mononuclear [M(acac)(cod)] (M = Rh, Ir, cod = 1,5-cyclooctadiene) in the presence of a external base, afforded the dinuclear complexes [M ₂(μ-S₂CR₂)(cod)₂] (1-4). The monodeprotonation of 1,1-dimercaptocyclopentane gave the mononuclear complex [Rh(HS₂Cptn)(cod)] (5) that is a precursor for the dinuclear compound [Rh₂(μ-S₂Cptn)(cod)₂] (6). Carbonylation of the diolefin compounds gave the complexes [Rh₂(M-S ₂CR₂)(CO)₄] (7-9), which reacted with P-donor ligands to stereoselectively produce the trans isomer of the disubstituted complexes [Rh₂(μ-S₂CR₂)(CO) ₂(PR′₃)₂] (R′ = Ph, Cy (cyclohexyl)) (10-13) and [Rh₂(μ-S₂CBn ₂)(CO)₂{P(OR′)₃}₂] (R′ = Me, Ph) (14-15). The substitution process in [Rh₂(μ-S ₂CBn₂)(CO)₄] (7) by P(OMe)₃ has been studied by spectroscopic means and the full series of substituted complexes [Rh₂(μ-S₂CBn₂)(CO)_4-n{P(OR) ₃}_n] (n = 1, 4) has been identified in solution. The eis complex [Rh₂(μ-S₂CBn₂)(CO) ₂(μ-dppb)] (16) was obtained by reaction of 7 with the diphosphine dppb (1,4-bis(diphenylphosphino)butane). The molecular structures of the diolefinic dinuclear complexes [Rh₂(μ-S₂CR ₂)(cod)₂] (R = Bn (1), ⁱPr (2); R₂ = -(CH₂)₄ - (6)) and that of the cis complex 16 have been studied by X-ray diffraction.

Full text of DOI:10.1021/ic800464p

Inorg. Chem. 2008, 47, 6090-6104
Synthesis, Structural Characterization, and Ligand Replacement
Reactions of gem-Dithiolato-Bridged Rhodium and Iridium Complexes
Angel B. Rivas,† Jose´ M. Gasco´n,‡ Fernando J. Lahoz,‡ Ana I. Balana,‡ Alvaro J. Pardey,†
Luis A. Oro,*,‡ and Jesu´s J. Pe´rez-Torrente*,‡
Departamento de Qu´ımica Inorga´nica, Instituto UniVersitario de Cata´lisis Homoge´nea, Instituto
de Ciencia de Materiales de Arago´n, UniVersidad de Zaragoza-CSIC, 50009 Zaragoza, Spain, and
Centro de Equilibrios en Solucio´n, Escuela de Qu´ımica, Facultad de Ciencias, UniVersidad
Central de Venezuela, Caracas, Venezuela
Received March 13, 2008
The reaction of gem-dithiol compounds R2C(SH)2 (R ) Bn (benzyl), iPr; R2 ) -(CH2)4-) with dinuclear rhodium
or iridium complexes containing basic ligands such as [M(µ-OH)(cod)]2 and [M(µ-OMe)(cod)]2, or the mononuclear
[M(acac)(cod)] (M ) Rh, Ir, cod ) 1,5-cyclooctadiene) in the presence of a external base, afforded the dinuclear
complexes [M2(µ-S2CR2)(cod)2] (1-4). The monodeprotonation of 1,1-dimercaptocyclopentane gave the mononuclear
complex [Rh(HS2Cptn)(cod)] (5) that is a precursor for the dinuclear compound [Rh2(µ-S2Cptn)(cod)2] (6). Carbonylation
of the diolefin compounds gave the complexes [Rh2(µ-S2CR2)(CO)4] (7-9), which reacted with P-donor ligands to
stereoselectively produce the trans isomer of the disubstituted complexes [Rh2(µ-S2CR2)(CO)2(PR′3)2] (R′ ) Ph,
Cy (cyclohexyl)) (10-13) and [Rh2(µ-S2CBn2)(CO)2{P(OR′)3}2] (R′ ) Me, Ph) (14-15). The substitution process
in [Rh2(µ-S2CBn2)(CO)4] (7) by P(OMe)3 has been studied by spectroscopic means and the full series of substituted
complexes [Rh2(µ-S2CBn2)(CO)4-n{P(OR)3}n] (n ) 1, 4) has been identified in solution. The cis complex [Rh2(µ-
S2CBn2)(CO)2(µ-dppb)] (16) was obtained by reaction of 7 with the diphosphine dppb (1,4-bis(diphenylphosphi-
i
no)butane). The molecular structures of the diolefinic dinuclear complexes [Rh2(µ-S2CR2)(cod)2] (R ) Bn (1), Pr
(2); R2 ) -(CH2)4- (6)) and that of the cis complex 16 have been studied by X-ray diffraction.
Introduction
sites in metalloenzymes,3 catalytic intermediates in the
hydrodesulfurization process (HDS) in homogeneous phase,4
and in the study of sulfur poisoning of solid catalysts.5
Transition metal-sulfur complexes have attracted con-
siderable attention due to their significant relevance to
biological and industrial processes.1 In particular, thiolato
derivatives of transition metals are of great importance in
coordination chemistry and a large number of mono- and
polynuclear compounds containing both simple and func-
tionalized thiolato and dithiolato ligands have been synthe-
sized and structurally characterized.2 The long-standing
interest in transition metal-thiolate chemistry has been
promoted from their relevance as model compounds of metal
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* To whom correspondence should be addressed. E-mail: oro@unizar.es
(L.A.O.), perez@unizar.es (J.J.P.-T.). Fax: 34 976761143.
†
Universidad Central de Venezuela.
Universidad de Zaragoza-CSIC.
‡
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6090 Inorganic Chemistry, Vol. 47, No. 13, 2008
10.1021/ic800464p CCC: $40.75  2008 American Chemical Society
Published on Web 05/29/2008

gem-Dithiolato-Bridged Rhodium and Iridium Complexes
However, the use of thiolate derivatives as building blocks
for heteropolymetallic transition-metal complexes6 and su-
pramolecular entities,7 their potential application in transition-
metal catalysis for the synthesis of organosulfur compounds,8
and their possible use as precursors for metal sulfides with
important technological applications9 are additional aspects
that have stimulated further developments in this field.
In contrast with the plentiful transition-metal complexes
containing dithiolato ligands, the number of gem-dithiolato
complexes, unlike those 1,1-ethylenedithiolato complexes
and related unsaturated dithiolene ligands that exhibit planar
geometry,10 is very scarce. On the other hand, trialkylphos-
phonium-dithioformate complexes also have a four-
membered dithiametallacyclobutane structural unit that re-
sults from the coordination of the two thiolato groups on
the sp3 carbon atom; however, these ligands are electronically
very different because of the zwitterionic character of the
[S2C(H)PR3] ligand.11 Surprisingly, all of the known gem-
dithiolato complexes have been obtained by indirect meth-
ods12–19 which do not involve gem-dithiol compounds as
reactants despite being already described in the early 1960s.20
Rational synthetic routes to mono- and dinuclear complexes
containing the simple methanedithiolato ligand (S2CH2)2-
involve the alkylation of several bis-hydrosulfido, M2(µ-SH)2
(M ) Mo, Re, Fe),13 or bis-sulfido Pt2(µ-S)2 dinuclear
complexes14 by dihalomethanes, generally in the presence
of a base or the insertion of carbon disulfide into M-H bonds
(M ) Cr, Mo, Re, Ru, Rh).15 Other complexes with (S2CR2)2-
ligands have been obtained, for example, by alkylation of
dinuclear methanedithiolato complexes,16 by the base-
induced double Michael addition of activated alkynes to
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Inorganic Chemistry, Vol. 47, No. 13, 2008 6091

Rivas et al.
dinuclear bis-hydrosulfido iron complexes,17 or by the
addition of acetone to a mononuclear bis-hydrosulfido iridium
compound in the presence of catalytic acid.18 Interestingly,
a variety of dirhenium gem-dithiolato complexes have been
prepared by the reaction of cis-[Re2(µ-O2CR)2Cl2(µ-dppm)2]
with dihydrogen sulfide in the presence of aldehydes or
ketones in acid media.19
Dinuclear d8 transition-metal complexes with doubly
bridged thiolates, [M2(µ-SR)2L4], have recently attracted
widespread interest regarding their electronic, structural, and
conformational properties.21 However, dinuclear rhodium
thiolato bridged complexes were already discovered to be
effective catalysts in the hydroformylation of olefins under
mild conditions in the early 1980s.22 Subsequent advances
in rhodium thiolate chemistry were focused on the utilization
of modified thiolato and dithiolato ligands, looking for the
influence of a more rigid structure on the catalytic activity.23
Furthermore, as chiral information can be introduced on the
backbone of the dithiolato ligand, these dinuclear systems
have found application in asymmetric hydroformylation,
especially in combination with chiral diphosphines.24 Inter-
estingly, complexes with dithiolato ligands have also been
used as synthons for the preparation of heterobimetallic
complexes with catalytic activity.25
complex from a gem-dithiol compound.26 This compound,
as the bis-thiolato and dithiolato dinuclear counterparts, is
an active catalyst precursor for the hydroformylation of
olefins under mild conditions. We report herein the scope
and limitations of this new synthetic methodology for the
direct synthesis of diolefin dinuclear gem-dithiolato com-
plexes [M2(µ-S2CR2)(cod)2] (M ) Rh, Ir) from several gem-
i
dithiols (R2C(SH)2; R ) Bn, Pr; and R2 ) -(CH2)4-). In
addition, the reactivity of the rhodium complexes with carbon
monoxide, the replacement reactions with several P-donor
ligands, and the comparison with the related thiolato di-
nuclear systems are also described.
Experimental Section
General. All manipulations were performed under a dry argon
atmosphere using Schlenk-tube techniques. Solvents were dried by
standard methods and distilled under argon immediately prior to
use. Standard literature procedures were used to prepare the
complexes [Rh(µ-OH)(cod)]2, [M(µ-OMe)(cod)]2 (M ) Rh, Ir),27
[M(acac)(cod)] (M ) Rh, Ir),28 [Rh(acac)(CO)(PPh3)],28a and
[Rh(acac)(CO)(PCy3)].29
Physical Measurements. 1H, 31P{1H}, and 13C{1H} NMR
spectra were recorded on a Varian Gemini 300 spectrometer
operating at 300.08, 121.47, and 75.46 MHz respectively. Chemical
shifts are reported in parts per million and referenced to SiMe4
using the residual resonances of the deuterated solvents (1H and
13C) and 85% H3PO4 (31P) as an external reference, respectively.
Assignments in complex NMR spectra were done by simulation
with the program gNMR ver. 3.6 (Cherwell Scientific Publishing
Limited) for Macintosh. The initial choice of chemical shifts and
coupling constants were optimized by successive iterations follow-
ing a standard least-squares procedure, a numerical assignment of
the experimental frequencies was used. IR spectra were recorded
on a Nicolet-IR 550 spectrometer. Elemental carbon, hydrogen, and
nitrogen analyses were performed with a PerkinElmer 2400
microanalyzer. Molecular weights were determined with a Knauer
osmometer using chloroform solutions of the complexes. Mass
spectra were recorded in a VG Autospec double-focusing mass
spectrometer operating in the FAB+ mode. Ions were produced with
the standard Cs+ gun at ca. 30 Kv, and 3-nitrobenzylic alcohol
(NBA) was used as a matrix.
We have recently reported the straighforward synthesis
2-
of the complex [Rh2(µ-S2Chxn)(cod)2] (ChxnS2 ) 1,1-
cyclohexanedithiolato) which is, to our knowledge, the first
example of direct synthesis of a gem-dithiolato-bridged
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A. J. Chem. Soc., Chem. Commun. 1983, 510. (b) Kalck, P. In
Organometallics in Organic Syntheses; de Meijere, A., Tom Dick,
H., Eds.; Springer Verlag: Weinheim, Germany, 1987; p 297. (c)
Kalck, P. Polyhedron 1988, 7, 2441.
Synthesis and Characterization of gem-Dithiol Com-
pounds. 1,1-Dimercaptocyclopentane, Cptn(SH)2,20a,b 2,4-dimethyl-
3,3-dimercaptopentane, iPr2C(SH)2,20c and 1,3-diphenyl-2,2-dimer-
captopropane, Bn2C(SH)2,20d were prepared according to reported
(23) (a) Bayo´n, J. C.; Claver, C.; Masdeu-Bulto´, A. M. Coord. Chem. ReV.
1999, 193-195, 73. (b) Castellanos-Paez, A.; Thayaparan, J.; Castillo´n,
S.; Claver, C. J. Organomet. Chem. 1998, 551, 375. (c) Aaliti, A.;
Masdeu, A. M.; Ruiz, A.; Claver, C. J. Organomet. Chem. 1995, 489,
101. (d) Masdeu, A. M.; Ruiz, A.; Castillo´n, S.; Claver, C.; Hitchcock,
P. B.; Chaloner, P. A.; Bo, C.; Poblet, J. M.; Sarasa, P. J. Chem. Soc.,
Dalton Trans. 1993, 2689. (e) Bayo´n, J. C.; Real, J.; Claver, C.; Polo,
A.; Ruiz, A. J. Chem. Soc., Chem. Commun. 1989, 1056.
(25) (a) Takemoto, S.; Shimadzu, D.; Kamikawa, K.; Matsuzaka, H.;
Nombra, R. Organometallics 2006, 25, 982. (b) Fornie´s-Ca´mer, J.;
Masdeu-Bulto´, A. M.; Claver, C.; Tejel, C.; Ciriano, M. A.; Cardin,
C. J. Organometallics 2002, 21, 2609. (c) Fornie´s-Ca´mer, J.; Claver,
C.; Masdeu-Bulto´, A. M.; Cardin, C. J. J. Organomet. Chem. 2002,
662, 188. (d) Fornie´s-Ca´mer, J.; Masdeu-Bulto´, A. M.; Claver, C.
Inorg. Chem. Commun. 2002, 5, 351. (e) Fornie´s-Ca´mer, J.; Masdeu-
Bulto´, A. M.; Claver, C. Inorg. Chem. Commun. 1999, 2, 89. (f)
Fornie´s-Ca´mer, J.; Masdeu-Bulto´, A. M.; Claver, C.; Cardin, C. J.
Inorg. Chem. 1998, 37, 2626. (g) Singh, N.; Prasad, L. B. Indian
J. Chem. 1998, A37, 169. (h) Aggarwal, R. C.; Mitra, R. Indian
J. Chem. 1994, A33, 55.
(24) (a) Freixa, Z.; Martin, E.; Gladiali, S.; Bayon, J. C. Appl. Organomet.
Chem. 2000, 14, 57. (b) Pamies, O.; Net, G.; Ruiz, A.; Bo, C.; Poblet,
J. M.; Claver, C. J. Organomet. Chem. 1999, 586, 125. (c) Castellanos-
Pa´ez, A.; Castillo´n, S.; Claver, C. J. Organomet. Chem. 1997, 539, 1.
(d) Ruiz, N.; Aaliti, A.; Fornies-Camer, J.; Ruiz, A.; Claver, C.; Cardin,
C. J.; Fabbri, D.; Gladiali, S. J. Organomet. Chem. 1997, 545-546,
79. (e) Ruiz, N.; Castillo´n, S.; Ruiz, A.; Claver, C.; Aaliti, A.;
AlvarezLarena, A.; Piniella, J. F.; Germain, G. J. Chem. Soc., Dalton
Trans. 1996, 969. (f) Masdeu-Bulto´, A. M.; Orejo´n, A.; Castellanos,
A.; Castillo´n, S.; Claver, C. Tetrahedron: Asymmetry 1996, 7, 1829.
(g) Masdeu, A. M.; Orejo´n, A.; Ruiz, A.; Castillo´n, S.; Claver, C. J.
Mol. Catal. A: Chem. 1994, 94, 149. (h) Claver, C.; Castillo´n, S.;
Ruiz, A.; Delogu, G.; Fabri, D.; Gladiali, S. J. Chem. Soc., Chem.
Commun. 1993, 1833.
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Torrente, J. J. Eur. J. Inorg. Chem. 2007, 5677.
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S. R.; Shaw, B. L. J. Chem. Soc. 1965, 4997.
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6092 Inorganic Chemistry, Vol. 47, No. 13, 2008

gem-Dithiolato-Bridged Rhodium and Iridium Complexes
i
methods. Analytical and NMR data: Cptn(SH)2. Anal. Calcd for
C5H10S2: C, 44.73; H, 7.51; S, 47.76. Found: C, 44.70; H, 7.48; S,
47.70. 1H NMR (CDCl3, 293 K) δ: 2.69 (s, 2H, SH), 2.06 (m, 4H,
>CH2), 1,81 (m, 4H, >CH2). 13C{1H} NMR (CDCl3, 293 K) δ:
55.6 (C1), 48.1 (C2 and C5), 23.6 (C3 and C4). Bn2C(SH)2. Anal.
Calcd for C15H16S2: C, 69.18; H, 6.19; S, 24.62. Found: C, 69.14;
H, 6.10; S, 24.50. 1H NMR (CDCl3, 293 K) δ: 7.33-7.28 (m, 10H,
Ph), 3.22 (s, 4H, >CH2), 2.36 (s, 2H, SH). 13C{1H} NMR (CDCl3,
293 K) δ: 136.0, 131.5, 127.9, 127,4 (Ph), 56.8 (C(SH)2), 52.8
(>CH2). iPr2C(SH)2. Anal. Calcd for C7H16S2: C, 51.16; H, 9.81;
and 31.1 (>CH2) (cod), 20.1 (-CH3, Pr). MS (FAB+, CH2Cl2,
m/z): 584 (M+, 100%).
[Ir2(µ-S2CBn2)(cod)2] (3). [Ir(acac)(cod)] (0.104 g, 0.260 mmol)
and Bn2C(SH)2 (0.040 g, 0.153 mmol) were reacted in CH2Cl2 (5
mL) for 15 min to give a dark-red suspension. The suspension was
concentrated under vacuum to about one-half the volume, and then
MeOH (3 mL) was added to complete the precipitation. The
compound was isolated by filtration, washed with MeOH (2 × 2
mL), and dried under vacuum. Yield: 0.099 g (88%). Anal. Calcd
for C31H38S2Ir2: C, 43.34; H, 4.46; S, 7.46. Found: C, 43.29; H,
4.36; S, 6.61. 1H NMR (CDCl3, 293 K) δ: 7.23 (m, 10H, Ph), 4.04
(m, 2H, dCH), 3.81 (m, 2H, dCH) (cod), 3.51 (s, 4H, >CH2, Bn),
2.09 (m, 8H, >CH2), 1.66 (m, 4H, >CH2), 1.27 (m, 4H, >CH2)
(cod). 13C{1H} NMR (CDCl3, 293 K) δ: 137.7, 131.2, 127.8, 126.6
(Bn), 95.1 (CS2), 66.2 (dCH, cod), 63.0 (>CH2, Bn), 62.9 (dCH),
31.8 and 31.6 (>CH2, cod). MS (FAB+, CH2Cl2, m/z): 860 (M+,
40%), 661 (M+ - cod - Bn, 30%).
1
S, 39.02. Found: C, 51.10; H, 9,70; S, 38.91. H NMR (CDCl3,
293 K) δ: 2.08 (sept, 2H, JH-H ) 7 Hz, CH, iPr), 2.05 (s, 2H, SH),
i
1.07 (d, 12H, JH-H ) 7 Hz, -CH3, Pr). 13C{1H} NMR (CDCl3,
293 K) δ: 68.0 (C(SH)2), 37.7 (CH), 18.2 (CH3) (iPr).
Synthesis of the Complexes. [Rh2(µ-S2CBn2)(cod)2] (1).
Method A. To a solution of [Rh(µ-OH)(cod)]2 (0.500 g, 1.096 mmol)
in CH2Cl2 (5 mL) was added 1,3-diphenyl-2,2-dimercaptopropane,
Bn2C(SH)2, (0.312 g, 1.200 mmol) to give immediately an orange-
red solution that was stirred for 15 min. The addition of EtOH (5
mL) afforded an orange suspension that was concentrated under
vacuum to ca. 5 mL and then filtered to give an orange microc-
rystalline solid, which was washed with EtOH (2 × 3 mL) and
dried under vacuum. Yield: 0.627 g (84%). Method B. [Rh(µ-
OMe)(cod)]2 (0.100 g, 0.206 mmol) and Bn2C(SH)2 (0.054 g, 0.206
mmol) were reacted in CH2Cl2 (5 mL) to give immediately a red
solution that was stirred for 30 min. The compound was isolated
as an orange-brown microcrystalline solid following the procedure
described above. Yield: 0.122 g (87%). Method C. Triethylamine
(120 µL, 0.652 mmol, F ) 0.728 g mL-1) and Bn2C(SH)2 (0.091
g, 0.350 mmol) were successively added to a solution of [Rh(acac)-
(cod)] (0.202 g, 0.650 mmol) in CH2Cl2 (5 mL) to give a red
solution that was stirred for 15 min. Work-up as described above
gave the compound as a red microcrystalline solid. Yield: 0.188 g
(85%). Anal. Calcd for C31H38S2Rh2: C, 54.71; H, 5.63; S, 9.42.
[Ir2(µ-S2CiPr2)(cod)2] (4). [Ir(µ-OMe)(cod)]2 (0.126 g, 0.190
mmol) and Pr2C(SH)2 (29 µL, F = 1 g mL-1, 0.177 mmol) were
i
reacted in CH2Cl2 (10 mL) at -78 °C for 10 min. The compound
was isolated as a dark-red solid following the procedure described
for 2. The crude compound was dissolved in a n-hexane/CH2Cl2
(3:1) mixture and then eluted through an alumina column (14 ×
1.5 cm) to give a violet solution. Concentration of the solution
afforded a purple microcrystalline solid that was filtered, washed
with n-pentane (2 × 3 mL), and dried under vacuum. Yield: 0.110
g (76%). Anal. Calcd for C23H38S2Ir2: C, 36.20; H, 5.02; S, 8.40.
1
Found: C, 36.00; H, 4.73; S, 8.83. H NMR (CDCl3, 293 K) δ:
4.26 (m, 4H, dCH), 3.92 (m, 4H, dCH) (cod), 2.48 (sept, 2H,
CH, JH-H ) 6.9 Hz, iPr), 2.28 (m, 4H, >CH2), 2.16 (m, 4H, >CH2),
1.87 (m, 4H, >CH2), 1.41 (m, 4H, >CH2) (cod), 0.98 (d, 12H,
-CH3, JH-H ) 6.9 Hz, iPr). 13C{1H} NMR (CDCl3, 293 K) δ: 110.4
(CS2), 65.7 and 63.2 (dCH, cod), 50.6 (CH, Pr), 32.6 and 31.9
(>CH2, cod), 19.9 (-CH3, iPr). MS (FAB+, CH2Cl2, m/z): 762 (M+,
i
I
100%), 613 (M+ - cod - Pr, 24%).
1
Found: C, 54.71; H, 5.90; S, 9.57. H NMR (CDCl3, 293 K) δ:
[Rh(HS2Cptn)(cod)] (5). To a solution of [Rh(acac)(cod)] (0.171
g, 0.550 mmol) in CH2Cl2 (10 mL) was added 1,1-dimercaptocy-
clopentane, Cptn(SH)2, (77 µL, 0.550 mmol, F ) 0.95 g mL-1) to
give immediately a dark-red solution that was stirred for 15 min.
The solution was concentrated under vacuum to ca. 5 mL, and then
MeOH (5 mL) was added to give a dark-red suspension. The
suspension was further concentrated, and then diethyl ether (5 mL)
was added to complete the precipitation. The suspension was filtered
and then recrystallized from CH2Cl2/diethyl ether to give the
compound as a dark-red solid. Yield: 0.128 g (68%). Anal. Calcd
for C13H21S2Rh: C, 45.34; H, 6.15; S, 18.62. Found: C, 45.30; H,
7.21 (m, 10H, Ph), 4.3 (m, 4H, dCH), 4.16 (m, 4H, )CH) (cod),
3.56 (s, 4H, >CH2, Bn), 2.36 (m, 4H, >CH2), 2.27 (m, 4H, >CH2),
1.80 (m, 4H, >CH2), 1.74 (m, 4H, >CH2) (cod). 13C{1H} NMR
(CDCl3, 293 K) δ: 137.8, 131.2, 127.6, 126.4 (Bn), 86.1 (CS2),
79.9 (d, JRh-C ) 12 Hz, dCH), 78.5 (d, JRh-C ) 12 Hz, dCH)
(cod), 60.9 (>CH2, Bn), 30.6 (>CH2, cod). MS (FAB+, CH2Cl2,
m/z): 680 (M+, 25%), 572 (M+ - cod, 15%), 464 (M+ - 2cod,
22%).
[Rh2(µ-S2CiPr2)(cod)2] (2). [Rh(µ-OH)(cod)]2 (0.151 g, 0.331
mmol) and 2,4-dimethyl-3,3-dimercaptopentane, iPr2C(SH)2, (52 µL,
F = 1 g mL-1, 0.317 mmol) were reacted in CH2Cl2 (10 mL) at
-78 °C for 10 min. The solution was allowed to warm up to room
temperature and stirred for 20 min. The resulting red-orange solution
was concentrated under vacuum to about one-half the volume and
then EtOH (5 mL) was added to give a red-orange solid that was
filtered, washed with EtOH (2 × 2 mL), and dried under vacuum.
The solid was dissolved in an n-hexane/CH2Cl2 (2:1) mixture and
then eluted through an alumina column (14 × 1.5 cm) to give an
orange solution. Concentration of the solution afforded an orange
microcrystalline solid that was filtered, washed with n-pentane (2
× 3 mL), and dried under vacuum. Yield: 0.151 g (78%). Anal.
Calcd for C23H38S2Rh2: C, 47.26; H, 6.55; S, 10.97. Found: C,
47.21; H, 6.40; S, 10.77. 1H NMR (CDCl3, 293 K) δ: 4.50 (m, 4H,
dCH), 4.25 (m, 4H, dCH) (cod), 2.65 (sept, 2H, JH-H ) 6.9 Hz,
1
5.95; S, 18.13. H NMR (CDCl3, 293 K) δ: 4.18 (m, 4H, dCH)
(cod), 2.39 (m, 5H, >CH2, cod and SH), 1.93 (br, 4H, >CH2) (cod),
1.82 (m, 4H, >CH2), 1.64 (m, 4H, >CH2) (Cptn). 13C{1H} NMR
(CDCl3, 293 K) δ: 81.7 (d, JRh-C ) 11 Hz, dCH, cod), 66.8 (C1),
48.5 (C2 and C5) (Cptn), 31.6 (>CH2, cod), 23.8 (C3 and C4, Cptn).
MS (FAB+, CH2Cl2, m/z): 554 (M+ + Rh(cod) - H, 89%), 343
(M+ - H, 67%).
[Rh2(µ-S2Cptn)(cod)2] (6). [Rh(µ-OH)(cod)]2 (0.350 g, 0.767
mmol) and Cptn(SH)2, (108 µL, 0.767 mmol, F ) 0.95 g mL-1
)
were reacted in CH2Cl2 (10 mL) at room temperature for 10 min.
The compound was isolated as a dark-red solid following the
procedure described for 1. The crude compound was dissolved in
CH2Cl2 and then eluted through an alumina column (12 × 1.5 cm)
with n-hexane/dichloromehane (2:1) to give an orange solution.
Concentration of the solution afforded an orange microcrystalline
solid that was filtered, washed with n-pentane (2 × 3 mL), and
dried under vacuum. Yield: 0.263 g (62%). Anal. Calcd for
i
CH, Pr), 2.45 (m, 8H, >CH2), 2.0 (m, 4H, >CH2), 1.85 (m, 4H,
i
>CH2) (cod), 1.20 (d, 12H, JH-H ) 6.9 Hz, -CH3, Pr). 13C{1H}
NMR (CDCl3, 293 K) δ: 101.2 (CS2), 79.5 (d, JRh-C ) 11.5 Hz,
dCH), 78.6 (d, JRh-C ) 12.4 Hz, dCH) (cod), 46.5 (CH, iPr), 31.6
Inorganic Chemistry, Vol. 47, No. 13, 2008 6093

Rivas et al.
C21H32S2Rh2: C, 45.49; H, 5.82; S, 11.56. Found: C, 45.61; H, 5.69;
S, 11.23. 1H NMR (C6D6, 293 K) δ: 4.85 (m, 4H, dCH), 4.44 (m,
4H, dCH) (cod), 2.54 (m, 4H, >CH2, Cptn), 2.46 (m, 8H, >CH2),
2.00 (m, 4H, >CH2), 1.85 (m, 4H, >CH2) (cod), 1.70 (m, 4H,
1.19 (d, JH-H ) 6.9 Hz, -CH3), 1.13 (d, JH-H ) 6.9 Hz, -CH3)
(iPr). 13C{1H} NMR (C6D6, 293 K) δ: 191.7 (dd, JRh-C ) 75 Hz,
2JP-C ) 17 Hz, CO), 135.2 (d, JP-C ) 44 Hz), 133.5 (d, JP-C ) 12
Hz), 129.6, 128.2 (d, JP-C ) 5 Hz) (PPh3), 102.3 (CS2), 47.6 (CH),
19.2 and 19.1(-CH3) (iPr). MS (FAB+, CH2Cl2, m/z): 948 (M+,
>CH2, Cptn). 13C{1H} NMR (CDCl3, 293 K) d: 79.9 (d, JRh-C
)
11 Hz, dCH), 78.9 (d, JRh-C ) 12 Hz, dCH) (cod), 81.9 (C1),
60.0 (C2 and C5) (Cptn), 31.5 and 31.1 (>CH2, cod), 25.0 (C3 and
C4, Cptn). MS (FAB+, CH2Cl2, m/z): 554 (M+, 100%), 446 (M+
- cod, 45%), 338 (M+ - 2cod, 32%).
100%); 920 (M+ - CO, 50%); 890(M+ - 2CO, 40%); 686 (M+
-
PPh3, 35%). IR (CH2Cl2, cm-1): ν (CO), 1956 (s).
[Rh2(µ-S2Cptn)(CO)2(PPh3)2] (12). [Rh(acac)(CO)(PPh3)] (0.065
g, 0.132 mmol) and Cptn(SH)2 (10.7 µL, 0.075 mmol, F ) 0.95 g
mL-1) were reacted in CH2Cl2 (10 mL) for 15 min to give an orange
solution. The compound was isolated as an orange solid following
the procedure described for 10 (method A). Yield: 0.049 g (81%).
Anal. Calcd for C43H38O2P2S2Rh2: C, 56.22; H, 4.17; S, 6.98.
[Rh2(µ-S2CBn2)(CO)4] (7). Carbon monoxide was bubbled
through an orange solution of [Rh2(µ-S2CBn2)(cod)2] (1) (0.100 g,
0.147 mmol) in CH2Cl2 (5 mL) for 10 min to give a pale-red
solution. n-Hexane (10 mL) was added, and the volume of the
solution reduced by continuous bubbling of carbon monoxide until
a red solid precipitated. Addition of n-hexane (3 mL) and
concentration by bubbling led to further precipitation. The com-
pound was isolated by filtration, washed with n-hexane (2 × 3 mL),
and dried under vacuum. Yield: 0.078 g (92%). Anal. Calcd for
C19H14O4S2Rh2: C, 39.60; H, 2.45; S, 11.13. Found. C, 39.90; H,
2.63; S, 11.09. 1H NMR (CDCl3, 293 K) δ: 7.45 (m, 8H), 7.28 (m,
2H), 3.31 (s, 4H, >CH2) (Bn). 13C{1H} NMR (CDCl3, 293 K) δ:
184.4 (d, JRh-C ) 72 Hz, CO), 136.9, 132.1, 128.3, 127.8, (Bn),
95.4 (CS2), 60.6 (>CH2, Bn). MS (FAB+, CH2Cl2, m/z): 576 (M+,
1
Found: C, 56.00; H, 4.16; S: 7.03. H NMR (CDCl3, 293 K) δ:
7.77-7.69 (m, 12H), 7.42-7.33 (m, 18H) (PPh3), 2.19 (m, 4H,
>CH2), 1.57 (m, 4H, >CH2) (Cptn). 13C{1H} NMR (CDCl3, 293
2
K) δ: 191.4 (dd, JRh-C ) 76 Hz, JP-C ) 17 Hz, CO), 134.8 (d,
JP-C ) 46 Hz), 133.9 (d, JP-C ) 12 Hz), 129.8 (s), 128.1 (d, JP-C
) 12 Hz) (PPh3), 84.3 (C1), 60.0 (C2 and C5), 24.5 (C3 and C5)
(Cptn). MS (FAB+, CH2Cl2, m/z): 918 (M+, 82%), 890 (M+
CO, 55%). IR (toluene, cm-1): ν(CO), 1972 (s).
-
[Rh2(µ-S2CBn2)(CO)2(PCy3)2] (13). [Rh(acac)(CO)(PCy3)] (0.103
g, 0.202 mmol) and Bn2C(SH)2 (0.026 g, 0.101 mmol) were reacted
in CH2Cl2 (10 mL) for 15 min to give a pale-orange solution that
was stirred for 15 min. The compound was isolated as a yellow
solid following the procedure described for 10 (method A). Yield:
0.089 g (82%). Anal. Calcd for C53H80O2P2S2Rh2: C, 58.88; H,
7.46; S, 5.93. Found: C, 58.35; H, 7.22; S, 6.02. 1H NMR (CDCl3,
293 K) δ: 7.20 (m, 10H, Bn), 3.96 (AB q, δA ) 4.02, δB ) 3.88,
JAB ) 14.85 Hz, 4H, >CH2, Bn), 2.04 (m, 18 H), 1.75 (m, 30 H),
1.23 (m, 18 H) (PCy3). 13C{1H} NMR (CDCl3, 293 K) δ: 192.1
(dd, JRh-C ) 76.9 Hz, 2JP-C ) 17.5 Hz, CO), 138.6, 130.8, 128.2,
126.7 (Bn), 86.2 (CS2), 62.0 (>CH2, Bn), 37.0 (d, JP-C ) 22 Hz,
-CHP), 30.7, 28.1 (d, JP-C ) 12.4 Hz), 26.9 (>CH2, PCy3). MS
(FAB+, CH2Cl2, m/z): 1080 (M+, 17%), 1052 (M+ - CO, 20%),
1024 (M+ - 2CO, 15%), 744 (M+ - 2CO - PCy3, 30%). IR
(CH2Cl2, cm-1): ν(CO), 1942 (s).
70%); 548 (M+ - CO, 95%), 520 (M+ - 2CO, 70%), 492 (M+
-
3CO, 85%), 464 (M+ - 4CO, 100%), 430 (M+ - 2CO - Bn,
80%). IR (CH2Cl2, cm-1): ν(CO), 2078 (m), 2054 (s), 2010 (s).
[Rh2(µ-S2CBn2)(CO)2(PPh3)2] (10). Method A. To a solution
of [Rh(acac)(CO)(PPh3)] (0.103 g, 0.209 mmol) in CH2Cl2 (10 mL)
was added Bn2C(SH)2 (0.027 g, 0.105 mmol) to give a red solution
that was stirred for 15 min. The solution was concentrated under
vacuum to about one-half the volume, and then MeOH (6 mL) was
added to afford an orange solid that was filtered, washed with
MeOH (2 × 3 mL), and dried under vacuum. Yield: 0.101 g (92%).
Method B. To a solution of compound [Rh2(µ-S2CBn2)(CO)4] (7),
prepared in situ by carbonylation of [Rh2(µ-S2CBn2)(cod)2] (1)
(0.100 g, 0.147 mmol) in CH2Cl2 (10 mL) for 15 min was added
solid PPh3 (0.077 g, 0.295 mmol) to give an orange solution with
evolution of carbon monoxide. The solution was stirred for 10 min,
and then MeOH (10 mL) was added to give a red suspension.
Concentration of the suspension to about one-half the volume led
to further precipitation. Filtration and washing with MeOH (3 × 3
mL) followed by drying under vacuum gave the product as an
[Rh2(µ-S2CBn2)(CO)2{P(OMe)3}2] (14). To a solution of [Rh2(µ-
S2CBn2)(CO)4] (7) (0.024 g, 0.042 mmol) in CH2Cl2 (5 mL) at
room temperature was added P(OMe)3 (10 µL, 0.084 mmol, F )
1.05 g mL-1, 98%) to give a yellow solution with evolution of
carbon monoxide. The solution was stirred for 10 min and then
n-hexane (5 mL) was added. The solvent was slowly eliminated
under vacuum, and the resulting thick solid was washed with
n-hexane (3 × 3 mL) to give a light orange solid that was filtered
and dried under vacuum. Yield: 0.029 g (91%). Anal. Calcd for
C23H32O8P2S2Rh2: C, 35.95; H, 4.20; S, 8.34. Found. C, 36.15; H,
orange-red solid. Yield: 0.138
g (90%). Anal. Calcd for
C53H44O2P2S2Rh2: C, 60.93; H, 4.24; S, 6.14. Found: C, 60.43; H,
1
4.44; S: 6.04. H NMR (C6D6, 293 K) δ: 7.6 (m, 12H), 7.3 (m,
18H) (PPh3), 7.0 (m, 10H, Ph), 3.50 (AB q: δA ) 3.98, δB ) 3.3,
JAB ) 14.1 Hz, 4H, >CH2, Bn). 13C{1H} NMR (C6D6; 293 K) δ:
192.5 (dd, JRh-C ) 76 Hz, 2JP-C ) 18 Hz, CO), 138.7 (Ph), 135.8
(d, JP-C ) 72 Hz), 134.8 (d, JP-C ) 12 Hz) (PPh3), 131.8 (Ph),
130.5 (PPh3), 128.9 (d, JP-C ) 12 Hz) (PPh3), 127.1 (Ph), 89.1
(CS2), 61.9 (>CH2, Bn). MS (FAB+, CH2Cl2, m/z): 1044 (M+,
100%), 1016 (M+ - CO, 35%), 988 (M+ - 2CO, 11%), 754 (M+
- CO - PPh3, 36%). IR (toluene, cm-1): ν(CO), 1967 (s).
[Rh2(µ-S2CiPr2)(CO)2(PPh3)2] (11). Carbon monoxide was
bubbled through a solution of [Rh2(µ-S2CiPr2)(cod)2] (2) (0.086 g,
0.147 mmol) in CH2Cl2 (10 mL) to give a yellow-brown solution
of the compound [Rh2(µ-S2CiPr2)(CO)4] (8) in 15 min. Further
reaction with PPh3 (0.077 g, 0.294 mmol) gave a deep-red solution
with evolution of carbon monoxide. Work-up as described above
for 10 (method B) gave the compound as a red solid. Yield: 0.120
g (93%). Anal. Calcd for C45H44O2P2S2Rh2: C, 56.97; H, 4.67; S,
1
4.18; S, 8.12. H NMR (C6D6, 293 K) δ: 7.54 (d, 4H), 7.27 (m,
4H), 7.19 (d, 2H) (Bn), 3.79 (AB q: δA ) 4.08, δB ) 3.50, JAB
)
2
13.35 Hz, 4H, >CH2, Bn), 3.58 (d, JC-P ) 12 Hz, -OMe).
13C{1H} NMR (C6D6, 293 K) δ: 190.24 (dd, JRh-C ) 74 Hz, 2JP-C
) 24 Hz, CO), 137.98, 131.59, 128.59, 127.20 (Bn), 90.42 (CS2),
62.56 (>CH2, Bn), 51.70 (OMe). MS (FAB+, CH2Cl2, m/z): 768
(M+, 32%), 712 (M+ - 2CO, 100%), 616 (M+ - CO - P(OMe)3,
33%), 588 (M+ - 2CO - P(OMe)3, 45%), 464 (M+ - 2CO -
2P(OMe)3, 25%). IR (toluene, cm-1): ν(CO), 1986 (s).
[Rh2(µ-S2CBn2)(CO)2{P(OPh)3}2] (15). [Rh2(µ-S2CBn2)(CO)4]
(7) (0.020 g, 0.035 mmol) and P(OPh)3 (19 µL, 0.070 mmol, F )
1.184 g mL-1, 97%) were reacted in CH2Cl2 (5 mL) at room
temperature to give a yellow solution with the evolution of carbon
monoxide. Work-up as described above gave the compound as a
1
6.76. Found: C, 56.56; H, 4.73; S, 6.75. H NMR (C6D6, 293 K)
yellow solid. Yield: 0.035
g (88%). Anal. Calcd for
δ: 8.11 (m, 12H), 7.32-7.18 (m, 18H) (PPh3), 3.07 (m, 2H, CH),
C53H44O8P2S2Rh2: C, 55.80; H, 3.89; S, 5.62. Found: C, 55.68; H,
6094 Inorganic Chemistry, Vol. 47, No. 13, 2008

gem-Dithiolato-Bridged Rhodium and Iridium Complexes
Table 6. Selected Bond Distances (Angstroms) and Angles (Degrees)
for 16
least-squares refinement of 3D centroids (3185 reflns, 4.5 e 2θ e
29.3° for 1; 6234, 9863, or 19 904 reflns, 4.5 e 2θ e 56.6° for 2,
6, or 16, respectively). Data were measured through the use of CCD
recording of narrow ω rotation frames (0.3° each). All data were
integrated with the Bruker SAINT program,30 which includes
Lorentz and polarization corrections. Absorption correction was
applied by using the SADABS routine.31
The structures were solved by Patterson methods, completed by
subsequent difference Fourier techniques, and refined by full-matrix
least-squares on F2 (SHELXL-97)32 with initial isotropic but
subsequent anisotropic thermal parameters for all non-hydrogen
atoms. Hydrogen atoms in 1 were included in the model from
calculated or observed (olefinic hydrogens) positions but were
refined with riding positional and displacement parameters. In the
case of 2, 6, and 16, hydrogen atoms were obtained from difference
Fourier maps and refined as free isotropic atoms. Atomic scattering
factors were used as implemented in the program.32
Rh(1)-S(1)
Rh(1)-S(2)
Rh(1)-P(1)
Rh(1)-C(1)
S(1)-C(3)
P(1)-C(21)
P(1)-C(22)
P(1)-C(28)
C(1)-O(1)
C(3)-C(4)
C(18)-C(19)
C(20)-C(21)
2.3995(5) Rh(2)-S(1)
2.3926(5) Rh(2)-S(2)
2.2655(5) Rh(2)-P(2)
2.4001(5)
2.3801(5)
2.2618(5)
1.837(2)
1.867(2)
1.834(2)
1.819(2)
1.826(2)
1.144(3)
1.551(3)
1.531(3)
1.840(2)
1.869(2)
1.851(2)
1.830(2)
1.823(2)
1.142(2)
1.540(3)
1.536(3)
1.528(3)
Rh(2)-C(2)
S(2)-C(3)
P(2)-C(18)
P(2)-C(34)
P(2)-C(40)
C(2)-O(2)
C(3)-C(11)
C(19)-C(20)
S(1)-Rh(1)-S(2)
S(1)-Rh(1)-P(1)
S(1)-Rh(1)-C(1)
S(2)-Rh(1)-P(1)
S(2)-Rh(1)-C(1)
P(1)-Rh(1)-C(1)
Rh(1)-S(1)-Rh(2)
Rh(1)-S(1)-C(3)
Rh(2)-S(1)-C(3)
S(1)-C(3)-S(2)
S(1)-C(3)-C(4)
S(1)-C(3)-C(11)
Rh(1)-C(1)-O(1)
71.047(16) S(1)-Rh(2)-S(2)
96.810(17) S(1)-Rh(2)-P(2)
71.248(16)
95.385(18)
168.50(6)
166.080(18)
98.92(6)
94.77(6)
76.399(14)
85.46(6)
172.34(6)
S(1)-Rh(2)-C(2)
166.816(18) S(2)-Rh(2)-P(2)
101.30(6)
90.82(6)
75.894(15) Rh(1)-S(2)-Rh(2)
S(2)-Rh(2)-C(2)
P(2)-Rh(2)-C(2)
Results
85.21(6)
85.19(6)
96.36(9)
110.01(13)
112.95(14)
179.6(2)
Rh(1)-S(2)-C(3)
Rh(2)-S(2)-C(3)
C(4)-C(3)-C(11)
S(2)-C(3)-C(4)
S(2)-C(3)-C(11)
Rh(2)-C(2)-O(2)
85.82(6)
112.35(16)
113.87(13)
110.36(13)
176.16(19)
Synthesis and Characterization of Diolefin gem-Di-
thiolato-Bridged Rhodium and Iridium Dinuclear
Compounds. The synthesis of gem-dithiolato-bridged di-
nuclear complexes can be accomplished directly from gem-
dithiol compounds using standard mono- or dinuclear
compounds containing basic ligands. Thus, reaction of [Rh(µ-
OH)(cod)]2 with 1,3-diphenyl-2,2-dimercaptopropane,
Bn2C(SH)2, in dichloromethane at room temperature gave a
red-orange solution of the compound [Rh2(µ-S2CBn2)(cod)2]
(1), which was isolated as an orange-red microcrystalline
solid in good yield. The synthesis of 1 can be also carried
out in similar yields starting from [Rh(µ-OMe)(cod)]2 or
[Rh(acac)(cod)] (1:2 molar ratio), although addition of an
external base (NEt3) is convenient for the later compound
to drive the reaction to completion. The related iridium
dinuclear compound [Ir2(µ-S2CBn2)(cod)2] (3) was obtained
as a purple microcrystalline solid in good yield from
Bn2C(SH)2 and [Ir(acac)(cod)] (1:2 molar ratio), although
without the need of an external base, probably because of
the low solubility of the complex in the reaction media
(Scheme 1).
The synthetic flexibility observed in the case of Bn2C(SH)2
is not completely applicable to the preparation of dinuclear
complexes with 2,4-dimethyl-3,3-dimercaptopentane, iPr2C-
(SH)2, as the synthesis is generally problematic due to side
reactions. Thus, following a similar synthetic protocol,
reaction of iPr2C(SH)2 with [Rh(acac)(cod)] (1:2 molar ratio)
in dichloromethane gave a deep-red solution from which the
trinuclear hydride cluster [Rh3(µ3-S)2(µ-H)(cod)3]33a was
isolated in 55% yield (Scheme 2). It is known that some
gem-dithiol compounds are transformed into the correspond-
ing thione by SH2(g) elimination.34 Thus, the formation of
the cluster is probably driven by the SH2(g) formed by the
1
4.02; S, 5.55. H NMR (C6D6, 293 K) δ: 7.71 (d, 12H, OPh),
7.51-7.33 (m, 10H, Bn), 7.27 (m, 12H), 7.06 (m, 6H) (OPh), 3.68
(AB q: δA ) 3.68, δB ) 3.48, JAB ) 14.4 Hz, 4H, >CH2, Bn).
13C{1H} NMR (C6D6, 293 K) δ: 189.2 (d, JRh-C ) 74 Hz, 2JP-C
)
24 Hz, CO), 152.4 (d, J ) 6 Hz, OPh), 137.6, 131.7 (Bn), 130.2
(OPh), 128.5, 127.3 (Bn), 125.5, 121.9 (OPh), 89.1 (CS2), 61.8
(>CH2, Bn). MS (FAB+, CH2Cl2, m/z): 1140 (M+, 20%), 1112
(M+ - CO, 30%), 1084 (M+ - 2CO, 45%), 802 (M+ - P(OPh)3
- CO, 35%), 774 (M+ - P(OPh)3 - 2CO, 85%). IR (toluene,
cm-1): ν(CO), 1994 (s).
[Rh2(µ-S2CBn2)(CO)2(µ-dppb)] (16). To a solution of 7 pre-
pared in situ by carbonylation of [Rh2(µ-S2CBn2)(cod)2] (1) (0.059
g, 0.087 mmol) in CH2Cl2 (10 mL) was added solid dppb (0.036
g, 0.087 mmol) to give a yellow solution with evolution of carbon
monoxide. The solution was stirred for 10 min and then concen-
trated under vacuum to about one-half the volume. The addition
of MeOH (5 mL) gave the compound as a yellow solid that was
filtered, washed with cold MeOH (3 × 3 mL), and dried under
vacuum. Yield: 0.072 g (87%). Anal. Calcd for C45H42O2P2S2Rh2:
1
C, 57.09; H, 4.47; S, 6.77. Found: C, 56.94; H, 4,35; S, 6.65. H
NMR (CDCl3, 293 K) δ: 7.80 (m, 4H), 7.67 (m, 4H), 7.64-7.00
(m, 14H), 7.04 (m, 8H) (Bn and dppb), 3.56 (AB q, δA ) 3.59, δB
) 3.54, JAB ) 14.10 Hz, 4H, >CH2, Bn), 2.46 (m, 4H), 2.20 (m,
2H), 1.40 (m, 2H) (>CH2, dppb). 31P{1H} NMR (CDCl3, 293 K)
δ: 32.25 (d, JRh-P ) 157 Hz). MS (FAB+, CH2Cl2, m/z): 946 (M+,
95%), 918 (M+ - CO, 26%), 890 (M+ - 2CO, 72%). IR (toluene,
cm-1): ν(CO), 1980 (s).
Crystal Structure Determination of [Rh2(µ-S2CBn2)(cod)2]
(1), [Rh2(µ-S2CiPr2)(cod)2] (2), [Rh2(µ-S2Cptn)(cod)2] (6), and
[Rh2(µ-S2CBn2)(CO)2(µ-dppb)] (16). Suitable crystals for X-ray
diffraction of 1, 2, 6, and 16 were obtained by slow diffusion of
n-hexane into CH2Cl2 solutions of the complexes at 258 K. A
summary of crystal data and refinement parameters for the structural
analyses is given in Table 6. The crystals used in the analyses were
glued to a glass fiber and mounted on a Bruker SMART APEX
diffractometer. The instrument was equipped with a CCD area
detector, and data were collected using graphite-monochromated
Mo KR radiation (λ ) 0.71073 Å) at low temperature (173 K (1)
or 100(1) K (2, 6, and 16)). Cell constants were obtained from the
(30) SAINTPLUS, Ver. 6.28; Bruker AXS: Madison, WI; 2001.
(31) Blessing, R. H. Acta Crystallogr. 1995, A51, 33; implemented in
SADABS: Area-Detector Absorption Correction, Ver. 2.03, 2002.
(32) SHELXTL Package, Ver. 6.10; Bruker-AXS: Madison, WI, 2000;
Sheldrick G.M. SHELXS-86 and SHELXL-97 , 1997.
(33) (a) Arif, A.; M, Hefner.; J. G., Jones.; R. A., Koschmieder.; S. U,
Polyhedron 1998, 7, 561. (b) Bright, T. A.; Jones, R. A.; Koschmieder,
S. U.; Nunn, C. M. Inorg. Chem. 1988, 27, 3819.
Inorganic Chemistry, Vol. 47, No. 13, 2008 6095

Rivas et al.
Scheme 1. Synthesis of Rhodium and Iridium gem-Dithiolato-Bridged
Dinuclear Diolefin Complexes
Figure 1. Molecular structure of [Rh2(µ-S2CBn2)(cod)2] (1).
Scheme 2. Formation of a Trirhodium Hydride Cluster by
i
Deprotonation of Pr2C(SH)2
i
decomposition of Pr2C(SH)2 mediated by [Rh(acac)(cod)].
This interpretation is sustained together by the detection in
the reaction media of the thione iPr2CdS (GC/MS evidence)
and by the clean formation of [Rh3(µ3-S)2(µ-H)(cod)3] by
reaction of [Rh(acac)(cod)] with SH2(g).
Figure 2. Molecular structure of [Rh2(µ-S2CiPr2)(cod)2] (2).
Nevertheless, the formation of the hydride clusters [M3(µ3-
S)2(µ-H)(cod)3] (M ) Rh, Ir)33 is minimized by using
rhodium and iridium dinuclear compounds as starting materi-
the expected two sharp resonances for the dCH protons and
four sharp multiplets for the >CH2 protons as a consequence
of the differentiation between the two groups of exo and
endo protons of the equivalent cod ligands. In accordance
with the chemical equivalence of both benzyl and isopropyl
fragments of the gem-dithiolato ligands in the structures, the
benzylic and isopropylic protons were observed as a sharp
singlet in 1 and 3 and as the expected septuplet and doublet
i
als. Thus, reaction of Pr2C(SH)2 with [Rh(µ-OH)(cod)]2 or
[Ir(µ-OMe)(cod)]2 afforded the compounds [Rh2(µ-
S2CiPr2)(cod)2] (2) and [Ir2(µ-S2CiPr2)(cod)2] (4), which were
isolated as orange and purple microcrystalline solids in 76%
yield after chromatography purification to remove the hydride
clusters (Scheme 1).
3
(1:6 ratio, JH-H ≈ 6.9 Hz) in 2 and 4, respectively. The
1-4 have been fully characterized by elemental analysis,
FAB mass spectra, and multinuclear NMR spectroscopy. In
addition, the structures of 1 and 2 have been determined by
X-ray diffraction methods (Figures 1 and 2), showing the
bridging and chelating coordination mode (1:2κ2S, 1:2κ2S′)
formation of the dimetallic core in 1-4 strongly influences
the chemical shift of the resonance of the geminal carbon
atoms of the bridging gem-dithiolato ligands in the 13C{1H}
NMR spectra. This resonance is shifted to higher frequencies,
compared to the free gem-dithiols, by about 30 ppm in the
rhodium (1 and 2) and 40 ppm in the iridium ones (3 and 4)
and reflects the effect of the ligand coordination to the metal
centers.
1
of the gem-dithiolato ligands. The H NMR of the com-
pounds showed no resonances attributable to SH protons,
indicating the complete deprotonation of the gem-dithiol
1
compounds upon the formation of the complexes. The H
Stepwise Formation of Dinuclear gem-Dithiolato-
Bridged Compounds. The monitoring of the reaction of
and 13C{1H} NMR showed rigid structures that are in
agreement with the dinuclear structures of C2V symmetry
found in the solid. In particular, the 1H NMR spectra showed
1
[Rh(acac)(cod)] with Bn2C(SH)2 in CDCl3 by H NMR
spectroscopy showed the exclusive formation of the dinuclear
compound [Rh2(µ-S2CBn2)(cod)2] (1) independently of the
utilized molar ratio (1:1 or 2:1) as a consequence of the
simultaneous deprotonation of both -SH groups of
(34) (a) Campaigne, E.; Edwards, B. E. J. Org. Chem. 1962, 27, 3760. (b)
Mayer, R.; Hiller, G.; Nitzschke, M.; Jentzsch, J. Angew. Chem., Int.
Ed. 1963, 75, 1011.
6096 Inorganic Chemistry, Vol. 47, No. 13, 2008

gem-Dithiolato-Bridged Rhodium and Iridium Complexes
Scheme 3. Stepwise Formation of the gem-Dithiolato-Bridged
Dinuclear 6
Figure 3. Molecular structure of [Rh2(µ-S2Cptn)(cod)2] (6).
the cod protons. Thus, the dCH and >CH2 protons were
observed as broad and featureless resonances at 4.18 ppm
and at 2.39 and 1.93 ppm, respectively. The resonance of
the SH proton probably is also broad and is hidden under
the resonances of the cod ligand. The 13C{1H} NMR
spectrum showed the full equivalence of the dCH and
>CH2 carbons, which were observed at 81.7 ppm (d, JRh-C
) 11 Hz) and at 31.6 ppm. The resonance of the geminal
carbon atom in 5 was observed at 66.8 ppm and, as
expected, is shifted to higher frequency compared to the
resonance of Cptn(SH)2 (23.6 ppm). As could be antici-
pated, this effect is more pronounced in 6 where this
resonance was observed at 81.9 ppm and is the result of
the (1:2κ2S, 1:2κ2S′) coordination mode of the doubly
deprotonated Cptn(SH)2 ligand.
Bn2C(SH)2. In sharp contrast, we have observed that in some
cases the deprotonation of the gem-dithiol compounds by
rhodium complexes can be carried out sequentially.
The reaction of 1,1-dimercaptopentane, Cptn(SH)2, with
[Rh(acac)(cod)] (1:2 molar ratio) and NEt3 in dichlorometane
gave a brown solution from which a brown solid was
1
isolated. The H NMR analysis of this solid in CDCl3
evidenced the formation of the dinuclear compound [Rh2(µ-
S2Cptn)(cod)2] (6) together with the mononuclear
[Rh(HS2Cptn)(cod)] (5), which was present in, roughly, 20%.
However, when the reaction was conducted in a 1:1 molar
ratio without NEt3 under the same conditions, the composi-
tion of the mixture was reversed, and the resulting dark-red
solution showed almost 85% of the mononuclear species
(Scheme 3). In fact, the mononuclear compound
[Rh(HS2Cptn)(cod)] (5) was isolated as a dark-red solid in
68% yield after recrystallization of the crude obtained
following this procedure. The dinuclear compound [Rh2(µ-
S2Cptn)(cod)2] (6) has been obtained as an orange solid in
62% yield from [Rh(µ-OH)(cod)]2 and Cptn(SH)2 after
purification by chromatography to remove 5 that is formed
in trace amounts. Interestingly, the deprotonation of
[Rh(HS2Cptn)(cod)] (5) can be accomplished by [Rh(µ-
OH)(cod)]2 in dichloromethane to give the dinuclear com-
pound [Rh2(µ-S2Cptn)(cod)2] (6) in good yield (Scheme 3).
The dinuclear formulation of 6 has been corroborated by
an X-ray diffraction study (Figure 3). In addition, the NMR
spectroscopic data of 6 closely resemble those of the
previously described dinuclear compounds and do not
deserve further comments. 5 has been characterized by
elemental analysis, mass spectrum, and NMR spectroscopy
as a mononuclear species containing a monodeprotonated
Cptn(SH)2 ligand with an unusual κ2S,S′ coordination mode.
The FAB mass spectrum showed the molecular ion at m/z
343 together with the ion at m/z 554 corresponding to the
dinuclear species. This ion most likely results from the
recombination of the produced ions because no mononuclear
fragments were observed in the FAB mass spectrum of 6.
In contrast with 6, which is rigid at room temperature, 5 is
The spectroscopic information obtained for [Rh(HS2-
Cptn)(cod)] (5) strongly suggests the existence of a dynamic
behavior responsible for the chemical equivalence of the
dCH protons and carbons of the cod ligand. Assuming a
planar or a dynamic puckering four-membered metalla-
cycle,35 the intramolecular shift of the SH proton between
both S-donor atoms together with the inversion of the sulfur
atom bearing the mercapto group would account for the
spectroscopic observations. A comparable dynamic process
involving the Au(PPh3)+ fragment, that is isolobal with H+,
has been observed in the early late heterotrimetallic com-
pound [Cptt Zr(µ-S)2{Ir(CO)2}{Au(PPh3)}] that contains a
2
[Zr(µ-S)2Ir] core.36
Molecular Structures of [Rh2(µ-S2CBn2)(cod)2] (1),
[Rh2(µ-S2CiPr2)(cod)2] (2), and [Rh2(µ-S2Cptn)(cod)2]
(6). The molecular structures of 1, 2, and 6 are shown in
Figures 1, 2, and 3, respectively, and their selected bond
lengths and angles are all deliberately arranged in Table 1.
In all of the three complexes, two Rh(cod) moieties are
connected through a gem-dithiolato µ-S2CR2 double bridge,
(35) (a) Tanabe, T.; Takeda, N.; Tokitoh, N. Eur. J. Inorg. Chem. 2007,
1225. (b) Komuro, T.; Matsuo, T.; Kawaguchi, H.; Tatsumi, K. Inorg.
Chem. 2003, 42, 5340. (c) Komuro, T.; Marsuo, T.; Kawaguchi, H.;
Tatsumi, K. Chem. Commun. 2002, 988. (d) Giolando, D. M.;
Rauchfuss, T. B.; Clark, G. M. Inorg. Chem. 1987, 26, 3080.
(36) Hernandez-Gruel, M. A. F.; Lahoz, F. J.; Oro, L. A.; Pe´rez-Torrente,
J. J. Organometallics 2007, 26, 6437.
1
fluxional and the H NMR showed average resonances for
Inorganic Chemistry, Vol. 47, No. 13, 2008 6097

Rivas et al.
Table 1. Crystal Data, Data Collection, and Refinement Parameters for 1, 2, 6, and 16
1
2
6
16
empirical formula
cryst size, mm
fw
space group
a, Å
C31H38Rh2S2
C23H38Rh2S2
C21H32Rh2S2
C45H42O2P2Rh2S2 ·CH2Cl2
0.37 × 0.23 × 0.22
1031.59
P21/n (No. 14)
17.6034(12)
10.6870(7)
24.2161(17)
90.0
107.7410(10)
90.0
4339.1(5)/4
1.579
0.17 × 0.09 × 0.06
0.38 × 0.11 × 0.02
0.34 × 0.34 × 0.34
680.55
584.47
554.41
j
j
P21/n (No. 14)
6.3798(5)
20.1991(16)
21.1670(17)
90.0
97.660(2)
90.0
2703.4(4)/4
1.672
P1 (No. 2)
P1 (No. 2)
6.4559(4)
10.8020(6)
16.8466(10)
99.427(1)
91.151(1)
104.990(1)
1117.11(11)/2
1.738
7.5580(5)
9.9802(6)
b, Å
c, Å
15.1423(9)
108.7250(10)
92.1170(10)
108.5870(10)
1012.90(11)/2
1.818
R, deg
ꢀ, deg
γ, deg
V, Å3/Z
Dcalcd, g·cm-3
µ, mm-1
1.394
0.787, 0.919
1.671
0.566, 0.964
1.837
0.537, 0.542
1.092
0.685, 0.792
min., max. transm. factors
no. of measd reflns
no. of unique reflns
no. of data/restraints/params
GOF (all data)a
17 795 (1.40 e θ e 28.61) 13 859 (1.98 e θ e 28.34) 12 332 (2.24 e θ e 28.29) 51 934 (1.71 e θ e 28.31)
6347 (Rint ) 0.1029)
6347/0/324
5274 (Rint ) 0.0252)
5274/0/396
1.026
0.0231 (4699 refl.)
0.0511
4718 (Rint ) 0.0132)
4718/0/354
1.103
0.0160 (4539 refl.)
0.0398
10 466 (Rint ) 0.0286)
10 466/0/681
1.056
0.0257 (9397 refl.)
0.0603
0.927
R1(F) (only for F2 > 2σ(F2))b 0.0487 (4572 refl.)
wR2(F2) (all data)c
0.1005
a
GOF ) (∑[w(Fo2 - Fc )2]/(n - p))1/2, where n and p are the number of data and parameters. b R1(F) ) ∑|Fo| - |Fc|/∑|Fo| only for observed reflections
2
c
2
2
2
2
2
2
(in parentheses). wR2(F2) ) (∑[w(Fo - Fc )2]/∑[w(Fo )2])1/2 where w ) 1/[σ2(Fo ) + (aP)2] and P ) [max(0, Fo ) + 2Fc ]/3.
with the sulfur atoms showing a (1:2κ2S, 1:2κ2S′) coordina-
tion mode. The major differences among the three molecular
structures merely concern the distinct R substituents of the
dithiolato ligands: two benzyl groups in 1, two iso-propyl
substituents in 2, and a cyclic four-membered saturated ring
of carbon atoms in 6.
(R ) C6F5),38 76.32 and 87.37° (R ) C6F4CF3),39 or 74.99
and 79.01° (R2 ) -CH2CH2-),23d respectively. These
structural modifications—fundamentally those affecting the
S-Rh-S bond angles—are also coupled with changes in
the dihedral angles between the metal coordination planes
(as evidenced by the RhS2Rh torsion angles: 105.49° (R )
Me),37 118.37° (R ) C6F5),38 117.39 (R ) C6F4CF3),39 or
104.16° (R2 ) -CH2CH2-)23d) and by the existence of
shorter intermetallic distances.
The coordination geometry around the rhodium centers is
in all cases distorted square-planar; the distortions funda-
mentally arise from the chelating behavior of the two ligands,
cod, and µ-S2CR2, with the S(1)-Rh-S(2) bond angles in
the range of 70.40(4)-72.017(13)° and the interolefinic
angles (between midpoints of coordinated double bonds) in
the range 87.44(16)-88.31(5)° (Table 1). The dihedral angle
between the two metal coordination planes are rather similar
(91.32(6) (1), 92.75(3) (2) and 93.59(2)° (6)) and the
metal-metal separations are almost unaffected by the change
in the thiolate substituent (2.8544(5) in 1, 2.8674(3) in 2,
and 2.8608(2) Å in 6). As previously observed for other
thiolate bridged Rh(I) complexes, both rhodium atoms are
slightly displaced out of the coordination mean-plane toward
theexternalpartofthemolecule(range0.0197(4)-0.1263(4)Å),
proving the existence of a weak repulsion between the metal
atoms, most likely due to the ligand-forced short metal-metal
nonbonding distance;23d,25f,26 this fact could be also sub-
stantiated by the values of the torsion angle Rh(1)-S(1) · · ·
S(2)-Rh(2) (94.51(4) in 1, 96.50(2) in 2, and 96.22(1)° in
6)) that, in all cases, are slightly larger (around 3°) than the
dihedral angle between coordination planes (see above).
If compared with other related (µ-SR)2 or (µ-SRS)
dithiolato complexes, the presence of these gem-dithiolato
ligands originates a feeble augment of the Rh-S-Rh bond
angle (mean 74.12(1)°), but a significant decrease in the
S-Rh-S bond angles (71.30(1)°); thus, values reported for
closely related dinuclear dithiolato complexes [Rh2(µ-
SR)2(cod)2] are (Rh-S-Rh and S-Rh-S mean values,
respectively): 77.75 and 75.90° (R ) Me),37 75.68 and 88.83°
All the cycloocta-1,5-diene molecules in 1, 2, and 6 exhibit
the classical tub conformation, showing analogous Rh-C
and olefinic C-C bond distances to those observed in the
above referred dithiolato complexes, reflecting the electronic
similarities between gem and general dithiolato ligands. Also,
the Rh-S bond distances observed (Table 1) are in the
central region of the separations detected in related dinuclear
dithiolato complexes [Rh2(µ-SR)2(cod)2] (range 2.289-2.487,
mean 2.38(3) Å).40
Synthesis and Characterization of Carbonyl gem-Di-
thiolato-Bridged Rhodium Dinuclear Compounds. The di-
nuclear framework of the gem-dithiolato-bridged rhodium
compounds is sustained in carbonylation reactions. The
carbonylation of diolefin rhodium 1, 2, and 6 at room
temperature in dichloromethane afforded colored solutions
of the corresponding tetracarbonyl complexes [Rh2(µ-
S2CBn2)(CO)4] (7), [Rh2(µ-S2CiPr2)(CO)4] (8), and [Rh2(µ-
S2Cptn)(CO)4] (9). However, the presence of cod in the
reaction media, the partial reversibility of the carbonylation
processes, and the relative instability of these complexes
make their isolation difficult.
Attempts to prepare the carbonyl complexes directly from
gem-dithiol compounds using carbonyl starting materials, for
example [Rh(acac)(CO)2], were unsuccessful. Fortunately,
(38) Cruz-Garritz, D.; Rodr´ıguez, B.; Torrens, H.; Leal, J. Transition Met.
Chem. 1984, 9, 284.
(39) Jones, W. D.; Garcia, J.; Torrens, H. Acta Crystallogr. 2005, E61,
m2204.
(37) Wark, T. A.; Stephan, D. W. Can. J. Chem. 1990, 68, 565.
6098 Inorganic Chemistry, Vol. 47, No. 13, 2008
(40) Allen, F. H. Acta Crystallogr. 2002, B58, 380.

gem-Dithiolato-Bridged Rhodium and Iridium Complexes
Table 2. Selected Bond Distances (Å) and Angles (deg) for 1, 2, and 6a
1
2
6
1
2
6
Rh(1)· · ·Rh(2)
Rh(1)-S(1)
Rh(1)-S(2)
Rh(1)-C(1)
Rh(1)-C(2)
Rh(1)-C(5)
Rh(1)-C(6)
S(1)-C(17)
C(1)-C(2)
2.8544(5)
2.3979(12)
2.4078(11)
2.137(5)
2.142(4)
2.125(4)
2.135(5)
1.847(4)
1.378(7)
1.373(7)
1.541(6)
2.8674(3)
2.3514(5)
2.3819(6)
2.142(2)
2.143(2)
2.119(2)
2.141(2)
1.870(2)
1.392(3)
1.390(3)
1.550(3)
2.8608(2)
2.3690(4)
2.3896(4)
2.1406(15)
2.1449(16)
2.1358(16)
2.1444(16)
1.8613(16)
1.397(2)
Rh(2)-S(1)
Rh(2)-S(2)
Rh(2)-C(9)
Rh(2)-C(10)
Rh(2)-C(13)
Rh(2)-C(14)
S(2)-C(17)
C(9)-C(10)
C(13)-C(14)
C(17)-C(19)b
2.3748(12)
2.3650(12)
2.129(4)
2.155(4)
2.129(4)
2.122(5)
1.867(4)
1.387(6)
1.386(7)
1.544(6)
2.3633(6)
2.3581(5)
2.126(2)
2.157(2)
2.138(2)
2.135(2)
1.875(2)
1.389(3)
1.394(3)
1.559(3)
2.3627(4)
2.3618(4)
2.1367(16)
2.1419(16)
2.1411(15)
2.1334(16)
1.8640(16)
1.398(2)
1.398(2)
1.549(2)
C(5)-C(6)
1.400(2)
1.543(2)
C(17)-C(18)
S(1)-Rh(1)-S(2)
S(1)-Rh(1)-M(1)
S(1)-Rh(1)-M(2)
S(2)-Rh(1)-M(1)
S(2)-Rh(1)-M(2)
M(1)-Rh(1)-M(2)
Rh(1)-S(1)-Rh(2)
Rh(1)-S(1)-C(17)
Rh(2)-S(1)-C(17)
S(1)-C(17)-S(2)
S(1)-C(17)-C(18)
S(1)-C(17)-C(19)b
70.40(4)
172.17(12)
100.14(12)
101.83(11)
170.49(11)
87.61(15)
73.46(3)
84.55(13)
88.23(13)
96.47(19)
113.4(3)
71.122(19)
172.95(5)
98.73(5)
102.07(5)
169.21(5)
87.94(7)
74.916(17)
86.65(7)
86.80(7)
71.420(13)
172.39(4)
99.10(4)
101.11(4)
170.33(4)
88.31(5)
74.399(12)
84.66(5)
86.86(5)
S(1)-Rh(2)-S(2)
S(1)-Rh(2)-M(3)
S(1)-Rh(2)-M(4)
S(2)-Rh(2)-M(3)
S(2)-Rh(2)-M(4)
M(3)-Rh(2)-M(4)
Rh(1)-S(2)-Rh(2)
Rh(1)-S(2)-C(17)
Rh(2)-S(2)-C(17)
C(18)-C(17)-C(19)b
S(2)-C(17)-C(18)
S(2)-C(17)-C(19)b
71.53(4)
170.81(12)
99.51(12)
100.75(11)
168.36(11)
87.44(16)
73.45(3)
83.85(13)
88.06(14)
108.5(3)
71.331(19)
170.87(5)
99.91(5)
100.67(5)
170.89(5)
87.85(7)
74.445(16)
85.66(7)
86.84(7)
72.017(13)
172.33(4)
99.70(4)
100.46(3)
169.28(3)
87.95(5)
74.038(12)
84.02(5)
86.83(5)
94.65(10)
110.12(14)
114.61(14)
96.42(7)
112.84(11)
115.42(11)
111.23(17)
110.03(14)
115.12(15)
105.48(13)
113.49(11)
113.41(11)
109.4(3)
113.2(3)
115.4(3)
a M(1), M(2), M(3), and M(4) represent the midpoints of the olefinic C(1)-C(2), C(5)-C(6), C(9)-C(10), and C(13)-C(14) bonds. b In 6, the atom label
of carbon atom bonded to C(17), analogous to C(19) in 1 and 2, corresponds to C(21).
Scheme 4. Replacement Reactions on gem-Dithiolato-Bridged
Dinuclear Complexes
the low solubility of [Rh2(µ-S2CBn2)(CO)4] (7) in n-hexane
allowed their isolation under a carbon monoxide atmosphere
as a red microcrystalline solid in excellent yield. The
dinuclear formulation of 7 relies on the FAB+ spectra that
showed the molecular ion at m/z 576 and the ions resulting
1
from the sequential losses of four carbonyl ligands. The H
and 13C{1H} NMR spectra in CDCl3 were in agreement with
a C2V symmetry structure resulting from the replacement of
a cod ligand by two carbonyls on each rhodium center. Thus,
the equivalent carbonyl ligands were observed as a doublet
at 184.4 ppm (JRh-C ) 72 Hz) in the 13C{1H} NMR spectrum
and the benzylic protons of the gem-dithiolato ligand as a
1
sharp singlet at 3.31 ppm in the H NMR spectrum.
The IR spectrum of 7 in solution (CH2Cl2) showed three
ν(CO) bands for the terminal carbonyl groups at 2078 (m),
2054 (s), and 2010 (s) cm-1. The same pattern has also been
observed in the IR of the in situ generated solutions of the
complexes [Rh2(µ-S2CiPr2)(CO)4] (8) and [Rh2(µ-
S2Cptn)(CO)4] (9) and [Rh2(µ-S2Chxn)(CO)4]26 (Table 2),
indicating that the formation of dinuclear tetracarbonyl
complexes from the parent olefin complexes is clean and
quantitative. The observed pattern of intensities (m, s, s) is
stituted complexes [Rh2(µ-S2CR2)(CO)2(PR′3)2] in the case
of phosphine ligands (PR′3 ) PPh3 or PCy3). Thus, the
addition of 2 mol equiv of PPh3 to solutions of tetracarbonyl
7 and 8, generated in situ by carbonylation of the corre-
sponding diolefin complexes, afforded orange solutions of
the complexes [Rh2(µ-S2CBn2)(CO)2(PPh3)2] (10) and [Rh2(µ-
S2CiPr2)(CO)2(PPh3)2] (11), which were isolated as orange-
red solids in excellent yields. 10 can be alternatively prepared
in similar yield by reaction of Bn2C(SH)2 with [Rh(acac)-
(CO)(PPh3)] (1:2 molar ratio) (Scheme 4). This synthetic
approach is also the more convenient for the synthesis of
the complexes [Rh2(µ-S2Cptn)(CO)2(PPh3)2] (12) and [Rh2(µ-
S2CBn2)(CO)2(PCy3)2] (13), which were obtained as orange
typical for tetracarbonyl dinuclear complexes having both
thiolato and dithiolato bridging ligands.21a,24d,41
Replacement Reactions on [Rh2(µ-S2CR2)(CO)4] by
P-Donor Ligands. The carbonyl replacement reactions by
P-donor ligands on the complexes [Rh2(µ-S2CR2)(CO)4] takes
place quickly at room temperature and stops at the disub-
(41) (a) Kiriakidou-Kazemifar, N. K.; Auca, M.; Pakkanen, T. A.; Tunik,
S. P.; Nordlander, E. J. Organomet. Chem. 2001, 623, 65. (b) Polo,
A.; Claver, C.; Castillo´n, S.; Ruiz, A.; Bayo´n, J. C.; Real, J.; Meali,
C.; Masi, D. Organometallics 1992, 11, 3525. (c) Bayo´n, J. C.;
Esteban, P.; Real, J.; Claver, C.; Polo, A.; Ruiz, A.; Castillo´n, S. J.
Organomet. Chem. 1991, 403, 393. (d) Bonet, J. J.; Thorez, A.;
Maisonnat, A.; Galy, J.; Poilblanc, R. J. Am. Chem. Soc. 1979, 101,
5940.
Inorganic Chemistry, Vol. 47, No. 13, 2008 6099

Rivas et al.
rhodium-rhodium bond distances in the dinuclear com-
plexes. Salient features in the 1H NMR of 10 and 13 are the
AB quartet (JAB ≈ 14 Hz), corresponding to the diaste-
reotopic >CH2 protons of the benzylic fragment in agreement
with the C2 symmetry of the compounds. Similarly, two
doublet resonances were observed for the diastereotopic
methyl groups of the isopropyl fragments in 11. The
equivalent carbonyl ligands in 10-13 were observed as a
doublet of doublets (dd) resonance in the 13C{1H} NMR
2
spectra, with JRh-C and JP-C couplings of ≈75 and 18 Hz,
respectively. Further evidence for the trans disposition of
the CO ligands in the structures comes from the observation
of a strong ν(CO) absorption in the IR of the complexes in
solution.41b,43
In contrast with 10-13, which do not react further with
PR′3 (PPh3 or PCy3), the reaction of complexes [Rh2(µ-
S2CR2)(CO)4] with phosphite ligands, P(OMe)3 and P(OPh)3,
goes further. The reaction of [Rh2(µ-S2CBn2)(CO)4] (7) with
P(OMe)3 has been studied in detail by 31P{1H} NMR (C6D6)
and four species [Rh2(µ-S2CR2)(CO)4-n{P(OR)3}n] (Pn, n )
1, 4) resulting from the partial or total replacement of the
CO ligands have been identified depending on the P(OR)3/
[Rh2] molar ratio (Table 4). The reaction of 7 with 1 mol
equiv of P(OMe)3 gave both the mono- and the disubstituted
complexes, P1 and P2. Interestingly, the reaction with 2 mol
equiv of P(OMe)3 gave predominantly the disubstituted P2
(mainly the trans isomer), although a small amount of the
monosubstituted P1 was still observed (Figure 5). Increasing
the P(OR)3/7 molar ratio to 3.5 resulted in the formation
almost exclusively of P3 and P4 (Figure 6). The molecular
ions of both species have been detected in the FAB+
spectrum of the resulting solution at m/z 836 (P3) and 960
(P4), respectively. Interestingly, the integrity of the dinuclear
unit is preserved when the P(OR)3/7 molar ratio was further
increased because the formation of the cationic mononuclear
species [Rh{P(OMe)3}4]+ was not detected.44
The attempt of isolation of P4 in the solid state was
unsuccessful because the compound was obtained as a
yellow-orange oil. However, the lack of formation of P3
when the P(OR)3/7 molar ratio was adjusted to 2 suggests
that the isolation of the P2 complexes could be possible. In
fact, the complexes [Rh2(µ-S2CBn2)(CO)2{P(OMe)3}2] (14)
and [Rh2(µ-S2CBn2)(CO)2{P(OPh)3}2] (15) have been ob-
tained as light orange and yellow solids, respectively, in
excellent yield. Both complexes have been fully characterized
by elemental analysis, FAB+ mass spectra, and NMR. The
31P{1H} NMR spectra showed that the compounds exist
mainly as the trans isomer, although the cis isomer is also
present in less than 5%. The resonance of the trans isomer
of both complexes closely resembles those of the related
phosphine 10-13 and has been simulated with the same
AA′XX′ spin system using the parameters of Table 3.
Noteworthy, similar 2JRh-P and JRh-Rh but larger 3JP-P (≈15
Hz) coupling constants have been observed.
Figure 4. (a) 31P{1H} NMR (CDCl3, 293 K) spectrum of [Rh2(µ-
S2Cptn)(CO)2(PPh3)2] (12). (b) Calculated 31P{1H} NMR spectrum for the
AA′XX′ spin system observed for the trans isomer.
Table 3. ν(CO) Stretching Frequencies (cm-1) Observed in the IR
Spectra in Solution (CH2Cl2) of Carbonyl 7-9
complex
ν(CO)
color
[Rh2(µ-S2Chxn)(CO)4]a
2082 (m), 2058 (s),
2013 (s) cm-1
red-brown
[Rh2(µ-S2CBn2)(CO)4] (7)
[Rh2(µ-S2CiPr2)(CO)4] (8)
[Rh2(µ-S2Cptn)(CO)4] (9)
2078 (m), 2054 (s),
red
2010 (s) cm-1
2080 (m), 2055 (s),
2011 (s) cm-1
yellow-brown
yellow-brown
2082 (m), 2059 (s),
2014 (s) cm-1
a Ref 26.
and yellow microcrystalline solids in good yield straight-
forwardly from the corresponding gem-dithiol and the
appropriate [Rh(acac)(CO)(PR′3)] complexes. The dinuclear
formulation of 10-13 relies on the FAB + spectra, which
showed the molecular ions and the sequential losses of two
carbonyl ligands. The complexes exist as the trans isomer
(C2 symmetry), although small amounts of the cis isomer
(Cs symmetry) (<3%) were observed in the 31P{1H} NMR
spectra of those complexes containing the less-steric de-
manding PPh3 ligands (10-12). The trans isomer showed a
distinctive complex resonance in the 31P{1H} NMR spectra
corresponding to an AA′XX′ spin system (Figure 4).42 The
observed signals correlate well with the calculated spectra
using the parameters reported in Table 3. Interestingly, each
phosphorus atom is coupled to both rhodium atoms with a
standard JRh-P and a negative small 2JRh-P coupling constants.
3
In addition, the observed JP-P (≈6 Hz) and JRh-Rh (3-4
Hz) coupling constants are in good agreement with a trans
disposition of the PR′3 ligands and the expected short
(43) (a) Balue´, J.; Bayo´n, J. C. J. Mol. Catal. A: Chem. 1999, 137, 193.
(b) Kalck, P.; Poilblanc, R. Inorg. Chem. 1975, 14, 2779.
(44) Wu, M. L.; Desmond, M. J.; Drago, R. S. Inorg. Chem. 1989, 18,
679.
(42) Hernandez-Gruel, M. A. F.; Pe´rez-Torrente, J. J.; Ciriano, M. A.; Rivas,
A. B.; Lahoz, F. J.; Dobrinovitch, I. T.; Oro, L. A. Organometallics
2003, 22, 1237.
6100 Inorganic Chemistry, Vol. 47, No. 13, 2008

gem-Dithiolato-Bridged Rhodium and Iridium Complexes
Table 4. 31P{1H} NMR (121.47 MHz, 293 K) Data for the Compounds [Rh2(µ-S2CR2)(CO)2(PR′3)2]a
compound
isomer
δ
JRh-P
2JRh-P
3JP-P
JRh-Rh
[Rh2(µ-S2CBn2)(CO)2(PPh3)2] (10)b
trans
cis
trans
cis
trans
cis
trans
trans
cis
41.59
39.60
41.76
40.20
41.37
39.00
51.56
139.96
141.00
122.08
123.30
163.70
163
163.10
163
163.50
162
156.88
258.07
252
-1.46
6.22
3.12
[Rh2(µ-S2CiPr2)(CO)2(PPh3)2] (11)b
[Rh2(µ-S2Cptn)(CO)2(PPh3)2] (12)c
-1.80
-1.23
6.45
6.19
3.42
3.58
[Rh2(µ-S2CBn2)(CO)2(PCy3)2] (13)c
-0.76
-1.95
4.29
14.00
3.33
2.89
[Rh2(µ-S2CBn2)(CO)2{P(OMe)3}2] (14)b
[Rh2(µ-S2CBn2)(CO)2{P(OPh)3}2] (15)c
trans
cis
276.82
273
-2.00
15.94
2.63
a The data of the trans isomers correspond to the calculated spectrum: AA′XX′ spin system, A ) 31P and X ) 103Rh (δ in ppm and J in Hz). b In C6D6.
c In CDCl3.
Figure 5. 31P{1H} NMR (C6D6) of the reaction of [Rh2(µ-S2CBn2)(CO)4]
(7) with 2 mol equiv of P(OMe)3 showing exclusively the presence of
[Rh2(µ-S2CBn2)(CO)2{P(OMe)3}2] (P2, cis and trans isomers, 14) and
[Rh2(µ-S2CBn2)(CO)3{P(OMe)3}] (P1).
Figure 7. Molecular structure of [Rh2(µ-S2CBn2)(CO)2(µ-dppb)] (16).
no)butane), resulted in the formation of cis disubstituted
complexes. The reaction of 7 with 1 mol equiv of dppb gave
a yellow solution of the compound [Rh2(µ-S2CBn2)(CO)2(µ-
dppb)] (16), which was isolated as a yellow solid in good
yield. The structure of 16 has been determined by X-ray
diffraction methods and is shown in Figure 7. The spectro-
scopic data obtained from the IR and NMR are in agreement
with an approximate Cs molecular symmetry as a result of
the coordination of the diphosphine in a cis fashion. The
diastereotopic >CH2 protons of the benzyl groups of the
bridging gem-dithiolato ligand are isochronus in C6D6 and
gave a single resonance at 3.94 ppm in the 1H NMR
spectrum. However, the spectrum in CDCl3 showed the
expected AB quarted centered at 3.56 ppm (JAB ≈ 14 Hz).
The 31P{1H} NMR spectrum features a slightly broad doublet
with no fine structure centered at 32.25 ppm (JRh-P ) 157
Hz). Finally, the equivalent carbonyl ligands were observed
as a broad absorption at 1980 cm-1 in the IR spectrum in
dichloromethane.
The related compound [Rh2(µ-Bn2CS2)(CO)2(µ-dppp)] has
also been identified in the reaction of 7 with dppp (27.87
ppm, d, JRh-P ) 170 Hz) together with other minor
unidentified species that could not be easily separated by
recrystallization. However, the observed JRh-P coupling
constants for these species (170-150 Hz) ruled out the
formation of cationic compounds such as [Rh(dppp)2]+ or
[Rh(CO)(dppp)2]+, potential products of the degradation of
the dinuclear structure.45
Figure 6. 31P{1H} NMR (C6D6) of the reaction of [Rh2(µ-S2CBn2)(CO)4]
(7) with 3.5 mol equiv of P(OMe)3 showing the presence of [Rh2(µ-
S2CBn2){P(OMe)3}4] (P4), [Rh2(µ-S2CBn2)(CO){P(OMe)3}3] (P3), and
traces of P2.
In contrast with monodentate P-donor ligands, that mainly
give rise to trans disubstituted complexes, the replacement
reactions on [Rh2(µ-S2CBn2)(CO)4] (7) using diphosphines
with a large bite angle, for example dppp (1,3-bis(diphe-
nylphosphino)propane) or dppb (1,4-bis(diphenylphosphi-
Inorganic Chemistry, Vol. 47, No. 13, 2008 6101

Rivas et al.
[Rh2(µ-StBu)2(CO)2(PPh3)2],48 [Rh2{µ-SC6H2(iPr)3}2(CO)2-
(PPh3)2],49 [Rh2(µ-SPh)2(CO)2(PMe3)2],50 or [Rh2(µ-
StBu)2(CO)2(PPh2CH2CH2NMe3)2].51
Table 5. 31P{1H} NMR Data (C6D6) for the Pn Compounds
[Rh2(µ-S2CBn2)(CO)4-n{P(OMe)3}n] (n Denotes the Number of
P(OMe)3 Ligands in the Dinuclear Framework)a
compound
δ
J (Hz)
As for the Rh-S bond distances, those trans to the CO
ligands (2.3995 and 2.4001(5) Å) are slightly longer than
those trans to the phosphines (2.3926 and 2.3801(5) Å), a
phenomenon previously descibed in other dithiolato
complexes.21a,50 The rest of the metrical parameters, both
in the metal environments and within the ligands, are very
similar to those of literature complexes that have been
structurally characterized.21a,48–51
P1
138.7
JRh-P ) 256
P2c
139.96 (trans isomer)b JRh-P ) 258.07, JRh-P ) -1.95,
2
3JP-P ) 14.0, JRh-Rh ) 2.89
JRh-P ) 252
141.0 (cis isomer)
146.1 (Pa), 145.3 (Pb), JRh1-Pa ) 275, JRh2-Pb ) 275,
142.2 (Pc)
P3b
JRh2-Pc ) 258, JPb-Pc ) 10.4,
JPa-Pc ) 3
JRh-P ) 272
P4
146.6
a For the labeling scheme used in P3, see Figure 6. b Calculated spectrum.
c P2 is actually 14.
Molecular Structure of [Rh2(µ-S2CBn2)(CO)2(µ-dppb)]
(16). A molecular diagram of this dinuclear complex is shown
in Figure 7, and key bond lengths and angles are collected
in Table 5. Like its diolefin analogues, 1, 2, and 6, complex
16 shows a folded Rh2S2 core, with both rhodium atoms in
a distorted square-planar coordination. The greatest distor-
tions from this square-planar geometry consist of the small
S-Rh-S bond angles (71.047(16) and 71.248(16)°), al-
though the sums of the four bond angles between pairs of
cis ligands around each metal easily add up to 360.0°. The
dihedral angle between the metal coordination planes is
significantly larger (99.66(2)°) than those observed in the
diolefinic analogues 1, 2, and 6 (range 91.32(6)-93.59(2)°);
in accordance with this fact, the intermetallic separation
elongates to 2.9514(3) Å. In this case, there are not structural
features that could be indicative of an intermetallic repulsion,
as the RhSSRh torsion angle detected is very similar
(98.60(2)°) to the interplanar angle between metal coordina-
tion planes.
The diphosphine ligand also bridges the two metals in 16
occupying relative cisoidal positions. Interestingly, within
both metal coordination planes the larger cis angles are those
between the dithiolato (S(2)) and the carbonyl groups
(101.30(6) and 98.92(6)°), most probably as a subtle
consequence of the bridging behavior of the diphosphine
ligand in the other side of the metal coordination. The whole
structure resembles quite well that of the dithiolato complex
[Rh2(µ-StBu)2(CO)2(µ-dppb)], in which two monodentate
tert-butyl thiolate groups bridge the two metals of an identical
Rh2(CO)2(µ-dppb) moiety.46
Discussion
The synthesis of dinuclear [M2(µ-S2CR2)(cod)2] (M ) Rh,
Ir) complexes can be accomplished by direct deprotonation
of gem-dithiol compounds with rhodium or iridium com-
plexes that contain basic ligands. The diolefin complexes
[M2(µ-S2CR2)(cod)2] (M ) Rh, Ir) are accessible from the
dinuclear complexes [M(µ-OH)(cod)]2 and [M(µ-OMe)-
(cod)]2, or the mononuclear [M(acac)(cod)], sometimes in
the presence of an external base. The dinuclear complexes
are generally obtained in high yield although, in the case of
iPr2C(SH)2, the syntheses are complicated by the formation
of the trinuclear hydride clusters [M3(µ3-S)2(µ-H)(cod)3]33
which can be easily separated by chromatography. The
formation of the sulfido clusters resulted from the SH2(g)
i
produced in the decomposition of Pr2C(SH)2 as has been
evidenced by the detection of Pr2CdS by GC/MS. The
i
stepwise deprotonation of the gem-dithiol compounds has
only been observed in the case of Cptn(SH)2, and both the
mononuclear [Rh(HS2Cptn)(cod)] (5) and the dinuclear
[Rh2(µ-S2Cptn)(cod)2] (6) compounds have been isolated and
fully characterized.
This synthetic methodology is also applicable to the
preparation of the complexes [Rh2(µ-S2CR2)(CO)2(PR′3)2],
which can be also prepared from [Rh(acac)(CO)(PR′3)] (R′
) Ph, Cy) but not to the carbonyl complexes [Rh2(µ-
S2CR2)(CO)4]. However, these complexes have been obtained
by carbonylation of the corresponding diolefin compounds
and are precursors for the disubstituted complexes [Rh2(µ-
S2CR2)(CO)2(PR′3)2] after carbonyl replacement by P-donor
ligands (R′ ) Ph, Cy, OMe, OPh).
The above-described results on the synthesis of gem-
dithiolato-bridged complexes [Rh2(µ-S2CR2)(L2)2] are, in
some aspects, comparable to those previously described in
bis-thiolato, [Rh(µ-SR)(L2)]2, or dithiolato, [Rh2(µ-
S(CH2)nS)(L2)2] (n ) 2-4), complexes as they all have an
open-book structure. However, significant differences are
observed in nuclearity, stereochemistry and reactivity that
are probably a consequence of the special geometrical
constrains imparted by the gem-dithiolato ligand in the M2S2
core. The bridging and chelating coordination mode (1:2κ2S,
It could be consider that the cis disposition of carbonyl
groups is a consequence of the bidentate nature of the dppb
ligand. However, a detailed search on related structurally
characterized dithiolato analogues, of general stoichiometry
[Rh2(µ-SR)2(CO)2(PR′3)2], reveals that these dithiolato-
bridged rhodium(I) systems exhibit a preference toward a
cis disposition of the carbonyl groups, not only when the
phosphine ligands could restrict the molecular geometry
(bidentate phosphines)46,47 but also when the PR3 is mono-
dentate and no geometric restrictions could be envisaged,
these are the cases of [Rh2(µ-SPytBu)2(CO)2(PPh3)2],21a
(45) (a) Sanger, A. R. J. Chem. Soc., Dalton Trans. 1977, 120. (b) James,
B. R.; Mahajan, D. Can. J. Chem. 1980, 58, 996.
(48) Jones, R. A.; Schwab, S. T. J. Crystallogr. Spectrosc. 1986, 16, 577.
(49) Dilworth, J. R.; Morales, D.; Zheng, Y. J. Chem. Soc., Dalton Trans.
2000, 3017/ 3007.
(50) Bonet, J. J.; Kalck, P.; Poilblanc, R. Inorg. Chem. 1977, 16, 1514.
(51) Schumann, H.; Hemling, N.; Goren, N.; Blue, J. J. Organomet. Chem.
1995, 485, 209.
(46) Kalck, P.; Randrianalimanana, C.; Ridmy, M.; Thorez, A.; tom Dieck,
H.; Ehlers, J. New J. Chem. 1988, 12, 679.
(47) (a) Fihri, A.; Hierso, J.-C.; Ivanov, V. V.; Rebiere, B.; Amardeil, R.;
Broussier, R.; Meunier, P. Inorg. Chim. Acta 2004, 357, 3089.
6102 Inorganic Chemistry, Vol. 47, No. 13, 2008

gem-Dithiolato-Bridged Rhodium and Iridium Complexes
1:2κ2S′) of the gem-dithiolato ligands results in the formation
of two four-membered metallocycles. In addition, the pres-
ence of a single bridgehead carbon atom between both sulfur
atoms produces a compact and rigid M2S2 core with a small
angle between the coordination planes of the rhodium centers
and short metal-metal distances.
the carbonyl replacement reactions in some dinuclear tetra-
carbonyl complexes encompass a change of nuclearity and
the formation of tetranuclear complexes is quite common,
depending on the structure of the dithiolato ligand.23c,24d,e
Nevertheless, some dinuclear complexes exist exclusively
as the trans isomer,23d,56 although cis/trans mixtures have
been observed in other cases.23c,57 Another striking difference
between the three types of complexes concerns the formation
of pentacoordinated species in the substitution process that
evolve to the disubstituted complex by decarbonylation.
Thus, the species [Rh(µ-SR)(CO)2(PR3)]2 have been char-
acterized in the bis-thiolate chemistry43b but have not been
observed in the gem-dithiolato complexes. Interestingly,
related species have detected in dithiolate chemistry under
CO pressure.58
An additional remarkable difference between bis-thiolate
and gem-dithiolate chemistry concerns the pattern of sub-
stitution by monodentate phosphite ligands. As described
above, it is possible to replace the four carbonyl ligands in
complex [Rh2(µ-S2CBn2)(CO)4] (7) as was evidenced by the
characterization of the complex [Rh2(µ-S2CBn2){P(OMe)3}4].
However, the disubstituted complex [Rh(µ-StBu)-
(CO){P(OMe)3}]2 does not react further with P(OMe)3
despite that compound [Rh(µ-StBu){P(OMe)3}2]2 can be
prepared from [Rh(µ-Cl){P(OMe)3}2]2 and LiStBu.59
As far as the carbonyl replacement by diphosphine ligands
is concerned, it is important to notice that a large number of
bis-thiolato complexes [Rh2(µ-SR)2(CO)2(µ-diphos)] contain-
ing bridging diphosphine ligands have been characterized
as the cis-anti isomer.46,60 In the same way, replacement
reactions on the carbonyl gem-dithiolato complexes gives
the expected cis isomer as has been exemplified by the
synthesis of [Rh2(µ-S2CBn2)(CO)2(µ-dppb)] (16). However,
in the dithiolato series the dinuclear framework is not
generally preserved as was evidenced by the formation of
ion-pair compounds [Rh(dppp)2][Rh(dithiolato)(CO)2] as the
result of the sequestering of a rhodium atom by dppp.23b
Concluding Remarks. We have described the high yield
synthesis of dinuclear [M2(µ-S2CR2)(cod)2] (M ) Rh, Ir) and
[Rh2(µ-S2CR2)(CO)2(PR3)2] complexes by double deproto-
nation of diverse gem-dithiol compounds using mono- or
dinuclear complexes containing basic ligands. The diolefin
complexes are precursors for the carbonyl complexes [Rh2(µ-
S2CR2)(CO)4], which undergo stereoselective replacement
reactions by P-donor ligands to give the trans disubstituted
complexes with monodentate ligands and the cis complexes
with bridging diphosphines. The synthetic versatility of this
kind of complexes, the singular structural features of the
The bis-thiolato complexes can exist as different conform-
ers (syn-exo, syn-endo, and anti) that arise from the spatial
arrangement of the bridging thiolato ligands with a 1:2κ2S
coordination mode.52 However, a large number of diolefin
complexes [M(µ-SR)(cod)]2 (M ) Rh, Ir) display a syn-endo
conformation in the solid state and have a dynamic behavior
by inversion of the nonplanar Rh2S2 ring.21a,41b,53,54 In
contrast, the dinuclear complexes [Rh2(µ-S2CR2)(cod)2] are
static as should be expected by the structure of the bridging
ligand that blocks the ring-flipping process. On the other
hand, dithiolato ligands afforded di- or tetranuclear com-
plexes depending on the structure of the dithiolato ligand.
For example, the nuclearity of the rhodium complexes
[Rh2(µ-S(CH2)nS)(cod)2]x is influenced by the number of
methylenic units between the two sulfur atoms. Thus,
dinuclear complexes (x ) 1) were prepared for n ) 2, 3,
but a tetranuclear complex was obtained in the case of 1,4-
butanedithiolato ligand (n ) 4).23d More sophisticated
ligands, for example, 1,1′-binaphthalene-2,2′-dithiolato, gave
a mixture of both di- and tetranuclear complexes.24e Interest-
ingly, the tetranuclear complexes were easily converted to
dinuclear complexes by carbonylation at atmospheric pres-
sure, that is [Rh2(µ-S(CH2)4S)(CO)4], indicating the strong
influence of the auxiliary ligands on the nuclearity.23d
Similarly, dinuclear complexes [Rh(µ-SR)2(CO)2]2 and [Rh2(µ-
S2CR2)(CO)4] were obtained along the carbonyl series with
bis-thiolato and gem-dithiolato ligands, respectively.
The replacement reactions by monodentate P-donor ligands
on the tetracarbonyl complexes usually stop at the disubsti-
tuted complexes. The solid-state structure of the complexes
[Rh(µ-SR)(CO)(PR′3)]2 show a cis arrangement of the bulky
phosphine or phosphite ligands and an anti conformation of
the bridging thiolato ligands with the endo substituent at the
side of the molecule with the small carbonyls
ligands.21a,48–51,55 However, in some complexes a dynamic
equilibrium between the cis and trans isomers has been
observed in solution.41b,43b,50 In contrast, the complexes
[Rh2(µ-S2CR2)(CO)2(PR3)2] that do not have any conforma-
tional restriction associated to the bridging ligand exist
predominantly as the trans isomer. In the dithiolato series,
(52) Aullo´n, G.; Ujaque, G.; Lledo´s, A.; Alvarez, S. Chem.sEur. J. 1999,
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J. Chem. Soc., Dalton Trans. 1992, 1831. (e) Wark, T. A.; Stephan,
D. W. Can. J. Chem. 1990, 68, 565. (f) Cotton, F. A.; Lahuerta, P.;
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(56) Bayo´n, J. C.; Esteban, P.; Real, J.; Claver, C.; Ruiz, A. J. Chem. Soc.,
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(57) Castellanos-Pa´ez, A.; Castillo´n, S.; and Claver, C. J. Organomet. Chem.
1997, 539, 1.
(58) Die´guez, M.; Claver, C.; Masdeu-Bulto´, A. M.; Ruiz, A.; van Leeuwen,
P. W. N. M.; Schoemaker, G. Organometallics 1999, 18, 2107.
(59) Kalck, P.; Pfister, P.-M.; Southern, T. G.; Thorez, A. Inorg. Synth.
1985, 23, 122.
(60) (a) Choukroun, R.; Dahan, F.; Gervais, D.; Rifai, C. Organometallics
1990, 9, 1982. (b) Senocq, F.; Randrianalimanana, C.; Thorez, A.;
Kalck, P.; Choukroun, R.; Gervais, D. J. Chem. Soc., Chem. Commun.
1984, 1376. (c) Choukroun, R.; Gervais, D.; Jaud, J.; Kalck, Ph.;
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(54) Abel, E. W.; Orrell, K. G. Prog. Inorg. Chem. 1984, 32, 1.
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Inorganic Chemistry, Vol. 47, No. 13, 2008 6103

Rivas et al.
compact Rh2S2 core enforced by the gem-dithiolato bridging
ligand, and the catalytic activity for the hydroformylation
of alkenes open the possibility of study of the influence of
the gem-dithiolato ligand on the catalytic activity. Further
studies concerning the reactivity and catalytic activity of these
complexes are currently in progress.
Desarrollo (CYTED) for a fellowship. Also, A.B.R. and
A.J.P. thank Fonacit-Venezuela (S1-2002000260) for finan-
cial support.
Supporting Information Available: X-ray crystallographic file
in CIF format for the structure determination of 1, 2, 6, and 16.
This material is available free of charge via the Internet at
http://pubs.acs.org.
Acknowledgment. The financial support from Ministerio
de Educacio´n y Ciencia (MEC/FEDER) Project CTQ2006-
03973/BQU is gratefully acknowledged. A.B.R. thanks the
Programa Iberoamericano de Ciencia y Tecnolog´ıa para el
IC800464P
6104 Inorganic Chemistry, Vol. 47, No. 13, 2008