Tetranuclear [Rh4(μ-PyS2) 2(diolefin)4] Complexes as Building Blocks for New Inorganic Architectures: Synthesis of Coordination Polymers and Heteropolynuclear Complexes with Electrophilic d8 and d10 Metal Fragments

Article abstract of DOI:10.1021/ic034893i

The reaction of [Rh₄(μ-PyS₂)₂(cod) ₄] (PYS₂ = 2,6-pyridinedithiolate, cod = 1,5-cyclooctadiene) with CF₃SO₃Me gave the cationic complex [Rh₄(μ-PyS₂Me)₂(cod) ₄][CF₃SO₃]₂ (1) with two 6-(thiomethyl)pyridine-2-thiolate bridging ligands from the attack of Me+ at the terminal sulfur atoms of the starting material. Under identical conditions [Rh₄(μ-PyS₂)₂(tfbb)₄] (tfbb = tetrafluorobenzobarrelene) reacted with CF₃SO₃Me to give the mixed-ligand complex [Rh₄(μ-PyS₂)(μ-PyS ₂Me)(tfbb)₄][CF₃SO₃] (2). The nucleophilicity of the bridging ligands in the complexes [Rh₄(μ -PyS₂)₂(diolefin)₄] was exploited to prepare heteropolynuclear species. Reactions with [Au(PPh₃)(Me ₂CO)][ClO₄] gave the hexanuclear complexes [(PPh ₃)₂Au₂Rh₄(μ-PyS₂) ₂(diolefin)₄][ClO₄]₂ (diolefin = cod (3), tfbb (4)). The structure of 4, solved by X-ray diffraction methods, showed the coordination of the [Au(PPh₃)]⁺ fragments to the peripheral sulfur atoms in [Rh₄(μ-PyS₂) ₂(diolefin)₄ along with their interaction with the neighbor rhodium atoms. Neutral coordination polymers of formula [CIMRh ₄(μ-PyS₂)₂(diolefin)₄] _n (M = Cu (5, 6), Au (7)) result from the self-assembly of alternating [Rh₄(μ-PyS₂)₂(diolefin) ₄] ([Rh₄]) blocks and MCI linkers. The formation of the infinite polymetallic chains was found to be chiroselective for M = Cu; one particular chain contains exclusively homochiral [Rh₄] complexes. Cationic heterometallic coordination polymers of formula [MRh ₄(μ-PyS₂)₂(diolefin)₄] _n (M = Ag (8, 9), Cu (10, 11)) and [Rh₅(μ-PyS ₂)₂(diolefin)₅]_n[BF ₄]_n (12, 13) result from the reactions of [Rh ₄] with [Cu(CH₃CN)₄]BF₄, AgBF ₄, and [Rh(diolefin)(Me₂CO)₂]BF₄, respectively. The heterometallic coordination polymers exhibit a weak electric conductivity in the solid state in the range (1.2-2.8) × 10^-7 S cm^-1.

Full text of DOI:10.1021/ic034893i

Inorg. Chem. 2004, 43, 1558−1567
Tetranuclear [Rh4(µ-PyS ) (diolefin)4] Complexes as Building Blocks for
2 2
New Inorganic Architectures: Synthesis of Coordination Polymers and
Heteropolynuclear Complexes with Electrophilic d8 and d10 Metal
Fragments
Miguel A. Casado, Jesu´s J. Pe´rez-Torrente, Miguel A. Ciriano,* Fernando J. Lahoz, and Luis A. Oro*
Departamento de Qu´ımica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n,
UniVersidad de Zaragoza-CSIC, 50009-Zaragoza, Spain
Received July 29, 2003
The reaction of [Rh4(µ-PyS ) (cod)4] (PyS ) 2,6-pyridinedithiolate, cod ) 1,5-cyclooctadiene) with CF SO Me
2 2
2
3
3
gave the cationic complex [Rh4(µ-PyS Me)2(cod)4][CF SO ] (1) with two 6-(thiomethyl)pyridine-2-thiolate bridging
2
3
3 2
ligands from the attack of Me+ at the terminal sulfur atoms of the starting material. Under identical condi-
tions [Rh4(µ-PyS ) (tfbb)4] (tfbb ) tetrafluorobenzobarrelene) reacted with CF SO Me to give the mixed-ligand
2 2
3
3
complex [Rh4(µ-PyS )(µ-PyS Me)(tfbb)4][CF SO ] (2). The nucleophilicity of the bridging ligands in the complexes
2
2
3
3
[Rh4(µ-PyS ) (diolefin)4] was exploited to prepare heteropolynuclear species. Reactions with [Au(PPh3)(Me2CO)]-
2 2
[ClO ] gave the hexanuclear complexes [(PPh3)2Au2Rh4(µ-PyS ) (diolefin)4][ClO ] (diolefin ) cod (3), tfbb (4)).
4
2 2
4 2
The structure of 4, solved by X-ray diffraction methods, showed the coordination of the [Au(PPh3)]+ fragments to
the peripheral sulfur atoms in [Rh4(µ-PyS ) (diolefin)4] along with their interaction with the neighbor rhodium atoms.
2 2
Neutral coordination polymers of formula [ClMRh4(µ-PyS ) (diolefin)4]n (M ) Cu (5, 6), Au (7)) result from the
2 2
self-assembly of alternating [Rh4(µ-PyS ) (diolefin)4] ([Rh4]) blocks and MCl linkers. The formation of the infinite
2 2
polymetallic chains was found to be chiroselective for M ) Cu; one particular chain contains exclusively homo-
chiral [Rh4] complexes. Cationic heterometallic coordination polymers of formula [MRh4(µ-PyS ) (diolefin)4]n[BF ]
2 2
4 n
(M ) Ag (8, 9), Cu (10, 11)) and [Rh5(µ-PyS ) (diolefin)5]n[BF ] (12, 13) result from the reactions of [Rh4] with
2 2
4 n
[Cu(CH CN)4]BF , AgBF , and [Rh(diolefin)(Me2CO)2]BF , respectively. The heterometallic coordination polymers
3
4
4
4
exhibit a weak electric conductivity in the solid state in the range (1.2−2.8) × 10-7 S cm-1.
Introduction
polydentate ligands with metal ions or unsaturated metal
complexes.2 The design of the ligand is crucial for this pur-
pose, since the dimensionality and topology of the final
assemblies are predominantly controlled by the coordination
preferences of the metal center and the location of the donor
sites in the organic ligand.3
The molecular self-assembly of coordination polymers and
supramolecular assemblies through metal-ligand coordina-
tion is a powerful method in the design of new materials
with promising physicochemical properties of potential
application in technology.1 The development of coordination
polymer chemistry has given rise to many remarkable inor-
ganic architectures through the self-assembly of suitable
An alternative approach to the synthesis of coordination
polymers and supramolecules is the use of transition metal
complexes as building blocks. Metal-containing ligands with
uncoordinated donor atoms can be induced to self-assemble
* To whom correspondence should be addressed. E-mail: mciriano@
posta.unizar.es (M.A.C.); oro@posta.unizar.es (L.A.O.). Department fax:
(+34) 976-761143.
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1558 Inorganic Chemistry, Vol. 43, No. 4, 2004
10.1021/ic034893i CCC: $27.50 © 2004 American Chemical Society
Published on Web 01/21/2004

Tetranuclear [Rh4(µ-PyS2)2(diolefin)4] Complexes
with other metal ions or unsaturated metal complexes through
the free coordination donors.4 In this context, mixed-metal
coordination polymers have been assembled using the rod-
shaped dicyanoargentate(I) complex and tetracyanoaurate-
(III) as building blocks.5 Mononuclear cyano isocyanoarene
and pyridyl phenyl isocyanide metal complexes, bearing
respectively cyano and pyridyl groups in peripheral sites,
are also effective building blocks for coordination polymers.6
Similarly, one-dimensional Cu(II)-Ag(I) mixed-metal chains
with 2-methylpyrazine-5-carboxylate spacers have been
obtained from a mononuclear Cu(II) complex having free
donor sites and silver(I) salts.7 Dinuclear species as connec-
tion devices for self-assembly have scarcely been exploited.
Very recently, reports from several groups describe the use
metalloligand, due to the presence of two available coordina-
tion donor sites at the peripheral sulfur atoms, has led to the
synthesis of the polymer [ClCuRh4(µ-PyS2)2(cod)4]n (cod )
1,5-cyclooctadiene) fully characterized by a crystal structure
determination.13 Thus, the tetranuclear complexes can be
envisaged as building blocks for new inorganic assemblies
by adding suitable metal centers and assuming that the
structure of the tetranuclear framework is maintained. Herein
we describe the construction of discrete heteropolynuclear
complexes and one-dimensional coordination polymers ob-
tained by reaction of the rhodium complexes [Rh4(µ-PyS2)2-
(diolefin)4] with electrophilic d8 and d10 metal complexes.
Results and Discussion
4+
of the Rh2 core as a building block to form both cyclic
Reactions of [Rh4(µ-PyS2)2(diolefin)4] ([M4]) with
CF3SO3Me. Synthesis of 6-(Thiomethyl)pyridine-2-thio-
late Cationic Complexes. Looking for the nucleophilic
centers in the complexes [M4], we reacted them with the
electrophilic Me+ to assess about the donor atoms and
their possible stereochemistry for further reactions with
metal centers. From the reaction of [Rh4(µ-PyS2)2(cod)4]
with CF3SO3Me the cationic tetranuclear species [Rh4(µ-
PyS2Me)2(cod)4][CF3SO3]2 (1) was isolated in good yield
as a red microcrystalline solid. The attack of Me+ occurred
at the terminal sulfur atoms of the complex [Rh4(µ-
PyS2)2(cod)4] to produce two 6-(thiomethyl)pyridine-2-thio-
late bridging ligands. Thus, complex 1 behaves as a 2:1
electrolyte in acetone, and the thiomethyl groups were ob-
supramolecules and coordination polymers by condensation
with appropriate bidentate ligands.8
As a result of our interest in the design of effective poly-
dentate ligands for the construction of polynuclear com-
plexes,9 we have prepared the tetranuclear [M4(µ-PyS2)2-
(diolefin)4] (M ) Rh, Ir) complexes ([M4]) supported by two
tridentate 2,6-pyridinedithiolate (PyS22-) bridging ligands
acting as six electron donors.10 The rhodium and iridium
tetranuclear complexes [M4] are redox-active precursors of
mixed-valence paramagnetic [M4]+ complexes.11 They also
behave as encapsulating agents for the thallium(I) ion to give
the cationic pentametallic species [TlM4(µ-PyS2)2(diolefin)4]+
through a great change of the coordination mode of the
bridging 2,6-dimercaptopyridine ligands and the formation
of two Tl-M bonds.12 A preliminary test on the capability
of the tetranuclear [Rh4(µ-PyS2)2(cod)4] complex to act as a
1
served as singlets at δ 2.80 ppm in the H and at 17.9 ppm
in the 13C{1H} NMR spectra. Moreover, both bridging
6-(thiomethyl)pyridine-2-thiolate ligands were found to be
equivalent, while the olefin carbons of the four 1,5-cyclo-
octadiene ligands displayed eight doublets in the 13C{1H}
NMR spectrum, evidencing that the cation possesses C2
symmetry. Compound 1 is apparently static while the parent
complex [Rh4(µ-PyS2)2(cod)4] is fluxional; the motion,
affecting the external cod ligands, is associated with the lone
electron pairs on the outer sulfur atoms.10 Thus, the formation
of the thiomethyl groups fixes 1 electron pair/sulfur and, as
a consequence, complex 1 becomes rigid.
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Withersby, M. A.; Schro¨der, M. Coord. Chem. ReV. 1999, 183, 117.
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Kyritsakas, N.; Fischer, J. Chem. Commun. 1998, 2545. (e) Fortin,
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Kaes, C.; Hosseini, M. W.; Rickard, C. E. F.; Skelton, B. W.; White,
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L.-F. Inorg. Chem. 1998, 37, 5776. (c) Mao, L.-F.; Mayr, A. Inorg.
Chem. 1996, 35, 3183.
The methylation of the 2,6-pyridinedithiolate bridges in
[Rh4(µ-PyS2)2(cod)4] resulted to be a stereoselective process.
The tetranuclear compound [Rh4(µ-PyS2)2(cod)4] exits as a
couple of enantiomers, which can be designed as (RS,RS)-
[Rh4] and (SS,SS)-[Rh4], since the two bridging sulfur atoms
are stereogenic. Upon methylation, the two terminal sulfur
atoms also become chiral centers; up to six different
stereoisomers could be produced depending on the relative
disposition of the thiomethyl groups in both enantiomers.
However, since the symmetry found for 1 is C2, both sulfur
atoms of the thiomethyl groups should have identical
configuration, and therefore, complex 1 resulted to be a
couple of enantiomers. Assuming that the thiomethyl groups
(7) Dong, Y.-B.; Smith, M. D.; zur Loye, H.-C. Inorg. Chem. 2000, 39,
1943.
(8) (a) Bonar-Law, R. P.; McGrath, T. D.; Singh, N.; Bickley, J. F.; Steiner,
A. Chem. Commun. 1999, 1707. (b) Cotton, F. A.; Daniels, L. M.;
Lin, C.; Murillo, C. A. J. Am. Chem. Soc. 1999, 21, 4538. (c) Bickley,
J. F.; Bonar-Law, R. P.; Femoni, C.; MacLean, E. J.; Steiner, A.; Teat,
S. J. J. Chem. Soc., Dalton Trans. 2000, 4025. (d) Miyasaka, H.;
Campos-Ferna´ndez, C. S.; Gala´n-Mascaro´s, J. R.; Dunbar, K. R. Inorg.
Chem. 2000, 39, 5870. (e) Cotton, F. A.; Lin, C.; Murillo. C. A. Acc.
Chem. Res. 2001, 34, 759.
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Coord. Chem. ReV. 1999, 193-195, 941.
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Alonso, P. J.; Lahoz, F. J.; Oro, L. A. Inorg. Chem. 1999, 38, 2482.
(13) Casado, M. A.; Pe´rez-Torrente, J. J.; Edwards, A. J.; Oro, L. A.;
Ciriano, M. A.; Lahoz, F. J. CrystEngComm 2000, 23 (http://
www.rsc.org/ej/ce/2000/b004750n/index.htm).
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Oro, L. A. Inorg. Chem. 1996, 35, 1782.
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Inorganic Chemistry, Vol. 43, No. 4, 2004 1559

Casado et al.
Chart 1. Proposed Structures of Complexes 1 and 2
were directed away from the bulky 1,5-cyclooctadiene
ligands on the neighboring rhodium atoms, complex 1 would
exist as the enantiomers (RS,RS,SS,SS)-(1) and (SS,SS,RS,RS)-
(1),14 the former being depicted in Chart 1.
Figure 1. Molecular structure of [(PPh3)2Au2Rh4(µ-PyS2)2(tfbb)4]-
[ClO4]2 (4).
(cod)4] with 2 molar equiv of the solvated species [Au(PPh3)-
(Me2CO)][ClO4] gave the heteropolynuclear complex [(PPh3)2-
Au2Rh4(µ-PyS2)2(cod)4][ClO4]2 (3), which was isolated as a
red microcrystalline solid in good yield. Similarly, the
hexanuclear complex [(PPh3)2Au2Rh4(µ-PyS2)2(tfbb)4][ClO4]2
(4) was isolated from the reaction of [Rh4(µ-PyS2)2(tfbb)4]
with [Au(PPh3)(Me2CO)][ClO4] as violet microcrystals. Both
complexes behave as 2:1 electrolytes in acetone, although
the peaks of largest m/z observed in the FAB+ mass spectra
corresponded to the ions [Rh4]-Au(PPh3)+ (100%). The two
bridging pyridine-2,6-dithiolate ligands and the PPh3 groups
The mixed-ligand complex [Rh4(µ-PyS2)(µ-PyS2Me)-
(tfbb)4][CF3SO3] (2) was obtained as a dark red microcrys-
talline solid by reaction of [Rh4(µ-PyS2)2(tfbb)4] with
CF3SO3Me as for the cod complex. It is noticeable that in
this case only one of the bridging ligands was methylated
and, consequently, complex 2 possesses 6-(thiomethyl)-
pyridine-2-thiolate and 2,6-pyridinedithiolate bridges (Chart
1
1). As expected, the H NMR spectra of 2 showed six
resonances for the aromatic protons of the two different
bridging ligands. The combination of the H,H-COSY spec-
trum, which allowed the identification of the two sets of three
resonances for the pyridine rings, with the detection of a
NOE effect (5%) between the protons of the thiomethyl
group at δ 2.79 ppm and the signal at δ 6.86 ppm allowed
the full assignment of the aromatic resonances.
Attempts to prepare the complex [Rh4(µ-PyS2Me)2-
(tfbb)4]2+ by reacting [Rh4(µ-PyS2)2(tfbb)4] with CF3SO3Me
in excess were also unsuccessful. Compound 2 was isolated
again under these conditions but in lower yield. This result
suggests a weaker nucleophilicity of the terminal sulfur atoms
in [Rh4(µ-PyS2)2(tfbb)4] than in the analogous cod complex,
which could be attributed to the stronger π-acceptor character
of the tfbb ligands. The partial methylation in 2 versus the
full methylation in 1 is a clear evidence for the interplay
between metals and ligands leading to an electronic com-
munication between the sulfurs. On the other hand, both
experiments corroborate the ability of the tetranuclear com-
plexes to engage electron pairs on the outer sulfur atoms
with electrophiles in a stereoselective way.
1
were found to be equivalent in the H NMR and 31P{1H}
NMR spectra of the complexes 3 and 4, respectively, in
agreement with structures with a C2 symmetry.
The molecular structure of compound [(PPh3)2Au2Rh4-
(µ-PyS2)2(tfbb)4][ClO4]2 (4) determined by X-ray methods
is shown in Figure 1. Selected bond distances and angles
are listed in Table 1. Compound 4 is hexanuclear re-
sulting from the coordination of two Au(PPh3)+ fragments
to the peripheral sulfur atoms of the tetranuclear complex
[Rh4(µ-PyS2)2(tfbb)4]. Both 2,6-pyridinedithiolate ligands are
bonded to the four rhodium centers and to one gold(I) atom,
acting as eight-electron donors. The C-S bond distances
(range 1.752-1.790(11) Å), corresponding to a bond order
near 1, suggest the major presence of the thiolate resonant
2-
hybrid of the PyS2 ligands rather than the thione upon
coordination to the Au atoms. The rhodium atoms exhibit a
slightly distorted square-planar geometry while the coordina-
tion environment of the gold(I) centers is roughly linear. It
is noticeable that the Au(PPh3) fragments are directed away
from the Rh(cod) fragments, as proposed for complex 1. In
consequence, compound 4 exists in the solid state as the two
enantiomers (RS,RS,SS,SS)-(4) and (SS,SS,RS,RS)-(4).14
Reaction of [Rh4(µ-PyS2)2(diolefin)4] with M(PPh3)+ (M
) Ag, Au). Syntheses of Discrete Heteropolynuclear
Complexes. Two further examples confirm the potential of
the tetranuclear complexes to act as bidentate ligands for
appropriate metal centers. Thus, the reaction of [Rh4(µ-PyS2)2-
An interesting structural feature of 4 concerns the inter-
metallic separations. Although the rhodium-rhodium dis-
tances (range 3.0720-3.3509(18) Å) are shorter than those
found in the complex [Rh4(µ-PyS2)2(cod)4] (3.9210(6) and
3.1435(5) Å), the shortening of the internal intermetallic
distance is notable. However, the shortest intermetallic
(14) Priority numbers have been assigned according to the standard
sequence rule developed for carbon compounds (CIP rules): von
Zelewsky, A. Stereochemistry of Coordination Compounds; Wiley:
New York, 1996. The two last descriptors design the configuration of
the former bridging sulfur atoms in the rhodium precursors.
1560 Inorganic Chemistry, Vol. 43, No. 4, 2004

Tetranuclear [Rh4(µ-PyS2)2(diolefin)4] Complexes
Table 1. Selected Bond Distances (Å) and Angles (deg) for
[(PPh3)2Au2Rh4(µ-PyS2)2(tfbb)4][ClO4]2 (4)a
Rh(1)-S(1)
Rh(1)-S(3)
Rh(1)-C(11)
Rh(1)-C(12)
Rh(1)-C(14)
Rh(1)-C(15)
Rh(2)-S(1)
Rh(2)-N(1)
Rh(2)-C(17)
Rh(2)-C(18)
Rh(2)-C(20)
Rh(2)-C(21)
Au(1)-S(3)
Au(1)-P(1)
S(1)-C(10)
S(3)-C(1)
2.366(3)
2.370(3)
Rh(4)-S(4)
Rh(4)-S(2)
Rh(4)-C(29)
Rh(4)-C(30)
Rh(4)-C(32)
Rh(4)-C(33)
Rh(3)-S(4)
Rh(3)-N(2)
Rh(3)-C(26)
Rh(3)-C(27)
Rh(3)-C(23)
Rh(3)-C(24)
Au(2)-S(2)
Au(2)-P(2)
S(4)-C(5)
2.380(3)
2.374(3)
2.120(11)
2.126(11)
2.176(10)
2.145(10)
2.358(3)
2.133(12)
2.110(10)
2.129(10)
2.199(10)
2.363(3)
2.115(8)
2.157(10)
2.107(9)
2.113(8)
2.156(10)
2.158(10)
2.133(10)
2.137(10)
2.328(3)
2.123(10)
2.145(10)
2.330(3)
2.254(3)
2.247(3)
Figure 2. Crystal packing of the compound [ClCuRh4(µ-PyS2)2(cod)4]n
(5) showing a short segment of two homochiral infinite chains. (The labeling
indicates the chirality of the sulfur atoms.)
1.757(10)
1.752(11)
1.365(11)
1.344(12)
1.334(13)
1.377(13)
1.375(12)
1.374(13)
1.345(13)
1.345(13)
1.402(13)
1.397(13)
1.790(10)
1.774(11)
1.362(12)
1.364(12)
1.359(13)
1.422(13)
1.404(13)
1.382(13)
1.413(14)
1.366(15)
1.376(13)
1.360(13)
S(2)-C(6)
N(1)-C(1)
N(2)-C(6)
N(1)-C(5)
N(2)-C(10)
C(6)-C(7)
C(1)-C(2)
ing as the coordination polymer (see below) [AgRh4-
(µ-PyS2)2(cod)4]n[ClO4]n in good yield and triphenylphos-
phine, the reaction with [Rh4(µ-PyS2)2(tfbb)4] gave the mono-
nuclear complex [Rh(tfbb)(PPh3)2]+ as the single isolated
species. Monitoring the latter reaction by 31P{1H} NMR
spectroscopy at low temperature confirmed the complete
transfer of the PPh3 ligands from the silver complex to Rh-
(tfbb)+ fragments arising from the tetranuclear complexes,
since the only phosphorus-containing species observed was
[Rh(tfbb)(PPh3)2]+ (δ 28.0 ppm; d, JRh-P ) 150 Hz).
Reactions of [Rh4(µ-PyS2)2(diolefin)4] with MCl (M )
Cu, Au), M+ (M ) Ag, Cu), and [Rh(diolefin)]+. Synthesis
of Coordination Polymers. We have shown13 that [ClCuRh4-
(µ-PyS2)2(cod)4]n (5), obtained by reaction of [Rh4(µ-PyS2)2-
(cod)4] with CuCl, is a mixed-metal coordination polymer
in the solid state resulting from the self-assembly of
alternating [Rh4(µ-PyS2)2(cod)4] blocks and CuCl linking
units, as shown in Figure 2. The related compound [ClCuRh4-
(µ-PyS2)2(tfbb)4]n (6) was isolated as a purple solid by mixing
equimolar amounts of [Rh4(µ-PyS2)2(tfbb)4] and CuCl in
dichloromethane. Looking for metal fragments other than
CuCl to act as linkers in polymeric structures based on the
tetranuclear [Rh4] ligands, we thought that nude cations of
the group 11 metals or complexes with two available
coordination positions could also produce polymeric struc-
tures by a self-assembly process.
The compound [AuCl(tht)] behaves as a source of “AuCl”
fragments due to the presence of the labile tetrahydrothio-
phene (tht) ligand. Thus, the reaction of [Rh4(µ-PyS2)2(tfbb)4]
with [AuCl(tht)] in dichloromethane (1:1 molar ratio) gave
the mixed-metal coordination polymer [ClAuRh4(µ-PyS2)2-
(tfbb)4]n (7), which was isolated as a purple microcrystalline
solid in good yield. However, the related cyclooctadiene
compound [ClAuRh4(µ-PyS2)2(cod)4]n could not be obtained
by this route, but a brown insoluble material with poorly
reproducible analytical results was isolated from the reaction
of [Rh4(µ-PyS2)2(cod)4] with 4 molar equiv of [AuCl(tht)].
The cationic mixed-metal coordination polymers contain-
ing silver(I), [AgRh4(µ-PyS2)2(cod)4]n[BF4]n (8) and [AgRh4-
C(2)-C(3)
C(7)-C(8)
C(3)-C(4)
C(8)-C(9)
C(4)-C(5)
C(9)-C(10)
C(29)-C(30)
C(32)-C(33)
C(26)-C(27)
C(23)-C(24)
C(11)-C(12)
C(14)-C(15)
C(17)-C(18)
C(20)-C(21)
S(1)-Rh(1)-S(3)
S(1)-Rh(1)-M(1)
S(1)-Rh(1)-M(2)
S(3)-Rh(1)-M(1)
S(3)-Rh(1)-M(2)
M(1)-Rh(1)-M(2)
S(1)-Rh(2)-N(1)
S(1)-Rh(2)-M(3)
S(1)-Rh(2)-M(4)
N(1)-Rh(2)-M(3)
N(1)-Rh(2)-M(4)
M(3)-Rh(2)-M(4)
S(3)-Au(1)-P(1)
Rh(1)-S(1)-Rh(2)
Rh(1)-S(1)-C(10)
Rh(2)-S(1)-C(10)
Rh(1)-S(3)-Au(1)
Rh(1)-S(3)-C(1)
Au(1)-S(3)-C(1)
Rh(2)-N(1)-C(1)
Rh(2)-N(1)-C(5)
C(1)-N(1)-C(5)
102.36(11) S(4)-Rh(4)-S(2)
101.17(10)
94.3(3)
159.9(3)
164.2(3)
96.0(3)
69.5(4)
89.8(3)
102.0(2)
169.5(2)
165.4(3)
97.6(3)
91.4(2)
158.1(3)
165.7(3)
97.1(3)
70.1(4)
90.2(2)
101.5(2)
167.3(2)
168.3(3)
97.8(3)
70.5(3)
S(4)-Rh(4)-M(7)
S(4)-Rh(4)-M(8)
S(2)-Rh(4)-M(7)
S(2)-Rh(4)-M(8)
M(7)-Rh(4)-M(8)
S(4)-Rh(3)-N(2)
S(4)-Rh(3)-M(6)
S(4)-Rh(3)-M(5)
N(2)-Rh(3)-M(6)
N(2)-Rh(3)-M(5)
M(5)-Rh(3)-M(6)
69.6(3)
177.04(12) S(2)-Au(2)-P(2)
175.86(11)
83.42(9)
111.9(4)
106.3(4)
81.25(10)
115.3(4)
98.7(4)
81.12(9)
111.2(3)
107.8(4)
Rh(4)-S(4)-Rh(3)
Rh(4)-S(4)-C(5)
Rh(3)-S(4)-C(5)
82.59(10) Rh(4)-S(2)-Au(2)
114.5(4)
98.4(4)
118.8(7)
122.5(7)
118.7(9)
Rh(4)-S(2)-C(6)
Au(2)-S(2)-C(6)
Rh(3)-N(2)-C(6)
Rh(3)-N(2)-C(10) 120.7(7)
C(6)-N(2)-C(10) 119.2(9)
120.1(7)
a M(1)-M(8) represent the midpoints of the olefinic bonds coordinated
to Rh atoms.
separation in 4, 3.0627(10) Å, corresponds to the Au‚‚‚Rh
separation. This distance, although clearly longer than those
found in complexes with rhodium(I)-gold(I) bonds, is short
enough to be indicative of an intermetallic interaction and
is probably a consequence of the metalophilic attraction
between both closed-shell d8-d10 metals.15
The attachment of Au(PPh3) groups to both terminal sulfur
atoms in [Rh4(µ-PyS2)2(tfbb)4] to give 4 contrasts with the
single methylation of one pyridine-2,6-dithiolate ligand with
CF3SO3Me to give [Rh4(µ-PyS2)(µ-PyS2Me)(tfbb)4]+ (2). The
difference reflects a lesser need of electronic density on the
sulfur atoms for coordination to a metal than for alkylation,
in addition to the affinity of gold for the soft sulfur donor
atoms.
The reactions of the tetranuclear complexes with [Ag-
(PPh3)]ClO4 gave distinct results. Thus, while the reaction
with [Rh4(µ-PyS2)2(cod)4] rendered an insoluble solid analyz-
(15) (a) Pyykko¨, P. Chem. ReV. 1988, 88, 563. (b) Pyykko¨, P. Chem. ReV.
1997, 97, 597. (c) Pyykko¨, P.; Li, J.; Runeberg, N. Chem. Phys. Lett.
1994, 218, 133.
Inorganic Chemistry, Vol. 43, No. 4, 2004 1561

Casado et al.
(µ-PyS2)2(tfbb)4]n[BF4]n (9), were obtained by reaction of the
complexes [Rh4(µ-PyS2)2(diolefin)4] with AgBF4. In a similar
fashion, the reaction of the complexes [Rh4(µ-PyS2)2-
(diolefin)4] with [Cu(CH3CN)4]BF4 resulted in the formation
of the coordination assemblies [CuRh4(µ-PyS2)2(cod)4]n[BF4]n
(10) and [CuRh4(µ-PyS2)2(tfbb)4]n[BF4]n (11) in good isolated
yields. The formation of the silver(I) complexes 8 and 9
competes with the oxidation of the corresponding rhodium
tetranuclear complexes. In fact, complex 8 decomposes
slowly in dichloromethane to give the paramagnetic com-
pound [Rh4(µ-PyS2)2(cod)4]BF4 and metallic silver.10
Neither [Rh4(µ-PyS2)2(cod)4] nor [Rh4(µ-PyS2)2(tfbb)4] was
found able to add [RhCl(diolefin)] fragments from the
complexes [Rh(µ-Cl)(diolefin)]2 (diolefin ) cod and tfbb),
although homometallic coordination polymers were acces-
sible by the reactions with cationic rhodium species with
two easily replaceable ligands. Thus, addition of [Rh(diole-
fin)(Me2CO)2]+ to the corresponding tetranuclear complex
in dichloromethane resulted in the formation of the cat-
ionic coordination polymers [Rh5(µ-PyS2)2(cod)5]n[BF4]n (12)
and [Rh5(µ-PyS2)2(tfbb)5]n[BF4]n (13), which were isolated
as purple and violet microcrystalline solids in excellent
yields. Attempts to apply this synthetic approach to coordi-
nation polymers made with [Rh4] as ligands and d8 centers
as linkers were unsuccessful, since the syntheses resulted to
be not selective. For example, the reaction of [Rh4(µ-PyS2)2-
(cod)4] with [Ir(cod)(Me2CO)x]+ gave mixtures of com-
pounds containing heterotetranuclear complexes [Rh3Ir] and
[Rh2Ir2] (FAB+ MS evidence) as the result of the exchange
between the added Ir(cod)+ fragment with Rh(cod)+ in the
[Rh4] complex.
Chiroselective Formation of [ClCuRh4(µ-PyS2)2(cod)4]n.
As already mentioned, the crystal structure of [ClCuRh4-
(µ-PyS2)2(cod)4]n (5) consists of one-dimensional chains
that propagate along a screw 2-fold axis; one particular
chain contains exclusively homochiral [Rh4] building
blocks.13 Figure 2 shows short segments of two complemen-
tary homochiral infinite chains; the upper chain contains
(RS,RS,RS,RS)-[Rh4] complexes and the lower (SS,SS,SS,SS)-
[Rh4] complexes.
Since the parent compound [Rh4(µ-PyS2)2(cod)4] exits as
the pair of enantiomers (RS,RS)-[Rh4] and (SS,SS)-[Rh4] and
the two peripheral sulfur atoms become chiral centers on
coordination to the CuCl linkers, a chiral recognition occurs
in the formation of each chain to be made exclusively from
either (RS,RS,RS,RS)-[Rh4] or (SS,SS,SS,SS)-[Rh4] complexes,
respectively. In this case not only the two new chiral sulfur
centers possess identical chirality but all the sulfur atoms
have identical chirality in a particular chain.14
Figure 3. Diastereoisomers of the molecular species ClCu-[Rh4]2: (a)
ClCu-(RS,RS,RS)-[Rh4]2/ClCu-(SS,SS,SS)-[Rh4]2;(b)ClCu-(RS,RS,RS)-[Rh4]-
(SS,SS,SS)-[Rh4].
presence of two well-defined molecular species in solution,
1
since the aromatic region of the H NMR spectrum in ben-
zene-d6 was outstandingly simple while the parent com-
plex [Rh4(µ-PyS2)2(cod)4] was not detected. Assuming that
the molecular species in solution were Cl2Cu2-[Rh4] and
ClCu-[Rh4]2, their combination would produce the poly-
meric chain. Supporting this idea, the ions ClCu2-[Rh4]+
and ClCu-[Rh4]+ were detected in the FAB+ spectrum. In
addition, the calculated molecular weight for an equimolar
mixture of Cl2Cu2-[Rh4] and ClCu-[Rh4]2 (1837) agrees
well with the experimental observed value (1730). Moreover,
the aromatic region of the 1H NMR spectrum of 3 is
compatible with the presence of both species in a 1:1 molar
ratio. Thus, the resonances at δ 8.40, 6.90, and 6.40 ppm
2-
would correspond to the homotopic PyS2 ligands of
Cl2Cu2-[Rh4], whereas the two sets of resonances at δ 7.90,
6.80, 6.30 and 6.90, 6.55, 6.05 ppm can be assigned to two
pairs of equivalent bridging ligands in ClCu-[Rh4]2, which
is in accordance with the couplings observed by analysis of
the H,H-COSY spectrum. From the above data, the species
Cl2Cu2-[Rh4], with a C2 axis, exists as a couple of enantio-
mers giving identical NMR spectra. The apparently single
species detected for ClCu-[Rh4]2 could be either the couple
of enantiomers ClCu-(RS,RS,RS)-[Rh4]2/ClCu-(SS,SS,SS)-
[Rh4]2 or the species ClCu-(RS,RS,RS)-[Rh4](SS,SS,SS)-[Rh4],
with C2 and Cs symmetries, respectively (Figure 3), or both
assuming that the resonances were averaged by a dissociative
equilibrium. Inspection of molecular models of ClCu-[Rh4]2
suggests that the steric interaction between the bulky 1,5-
cyclooctadiene ligands and the bridging ligands is notably
reduced if the ClCu-[Rh4]2 moiety is made of two homo-
chiral tetranuclear complexes, i.e., the second species de-
tected is the couple of enantiomers. As a consequence, the
formation of the polymer would encompass the molecular
recognition between the following chiral molecular compo-
nents ClCu-(RS,RS,RS)-[Rh4]2/Cl2Cu2-(RS,RS,RS,RS)-[Rh4]
and ClCu-(SS,SS,SS)-[Rh4]2/Cl2Cu2-(SS,SS,SS,SS)-[Rh4].
The chiroselectivity observed in the formation of the
polymeric chains in 3 is an unusual example of chiral
In contrast with most of the coordination polymers
described herein the compound [ClCuRh4(µ-PyS2)2(cod)4]n
(5) is soluble in chlorinated solvents and in benzene. The
fragmentation of the polymeric structure in solution becomes
evident after the determination of a remarkably low molec-
ular weight (1730) in chloroform while compound 5 is a
nonelectrolyte in this solvent. The crystallization of 5 leads
to the formation of the infinite homochiral chains in a
reversible way. Spectroscopic data in solution suggest the
1562 Inorganic Chemistry, Vol. 43, No. 4, 2004

Tetranuclear [Rh4(µ-PyS2)2(diolefin)4] Complexes
Chart 2. Possible Solid-State Structures for the Cationic Coordination Polymers Containing M+ (M ) Ag and Cu) and Rh(diolefin)+ Linkers
selection during the self-assembly process. Chiroselective
self-assembly of [2 × 2] grid-type inorganic arrays with
different octahedral metal centers have been reported.16
Diastereoselectivity has been also observed in the self-
assembly of molecular squares based on palladium and
platinum square-planar complexes17 and in homochiral
macrocyclic dinuclear anions containing octahedral molyb-
denum complexes.18 A related 2-D phenomenon in a su-
pramolecular three-dimensional hydrogen-bonded network
derived from diacetylene dicarboxylic acid dihydrate has
been noticed.19 Multiple hydrogen bonding also produces
homochiral columnar structures made with alternate stacked
(tfbb)4]n (7) are probably related to that of compound 5 since
both have MCl linkers. Possible solid-state structures for the
cationic coordination polymers containing M+ (M ) Ag and
Cu) and Rh(diolefin)+ linkers are shown in Chart 2 in which
the BF4- anions and the auxiliary diolefin ligands have been
omitted for clarity. They are based on molecular models
assuming linear (d10) and square planar (d8) coordination
environments imposed for the metal linkers. It is noticeable
that the suggested zigzag arrangement of the polymeric
chains results from the relative disposition of the tetranuclear
building blocks in the chains to reduce the repulsion between
the bulky diolefin ligands.
3-
cations [Co(en)3]3+ and P3O9 anions with the Λ or ∆
Most of the compounds described herein are insoluble in
common organic solvents once they have been isolated as
solids, which precludes characterization in solution. The
insolubility seems to be a dominant feature of the coordina-
tion polymers, and insoluble materials have been proposed
to be coordination polymers on the basis of this property.21
enantiomer.20 In our case, the origin of the stereoselectivity
in the methylation leading to 1 and in the formation of the
homochiral chains in 3 is probably associated with steric
reasons; i.e., the entering group (methyl or metal) occupies
the less hindered site on the peripheral sulfur atoms.
Characterization and Properties of the Coordination
Polymers. The coordination polymers have been char-
acterized by elemental microanalyses and FAB+ MS. Diag-
nostics for the coordination polymers are the respective
FAB+ MS, since characteristic fragments arising from the
polymeric structures are regularly observed in the mass
spectra. In particular, a peak corresponding to the fragment
[Rh4]-M-[Rh4]+ is observed in the FAB+ mass spectra of
the compounds 7 (M ) Au), 8 and 9 (M ) Ag), and 12 (M
) Rh). It is noticeable that all the coordination polymers
also exhibit the peaks corresponding to the ions [Rh4]-M+
and [Rh4]+ which confirm both the integrity of the tetra-
nuclear building blocks and the coordination of the added
electrophilic metal fragments.
1
Compounds 10 and 12 are soluble in CDCl3. While the H
NMR spectrum of 12 was not resolved even at low
temperature, that of [CuRh4(µ-PyS2)2(cod)4]n[BF4]n (10) was
very simple, showing three sharp resonances at δ 8.18 (d),
7.82(d), and 7.02 (dd) in CDCl3 at 218 K. A possible
interpretation for the simplicity of this spectrum would be
the existence of symmetric cyclic oligomers in solution. As
shown in Figure 4, a cyclic structure of D2 symmetry,
[CuRh4(µ-PyS2)2(cod)4]44+, can be made of four homochiral
rhodium tetranuclear complexes, which would account for
the observed spectrum, since all the pyridine-2,6-dithio-
late bridging ligands become equivalent. Interestingly, the
existence of cyclic oligomers and polymeric species made
of a given monomeric unit seems to be controlled by subtle
steric and electronic factors.22 For example, the hydration
of the cyclic hexamer [{Ag(pymo)}6] gives the polymer
The solid-state structures of the coordination polymers
[ClCuRh4(µ-PyS2)2(tfbb)4]n (6) and [ClAuRh4(µ-PyS2)2-
(16) Bassani, D. M.; Lehn, J.-M.; Fromm, K.; Fenske, D. Angew. Chem.,
Int. Ed. 1998, 37, 2364.
(17) Stang, P. J.; Olenyuk, B. Angew. Chem., Int. Ed. Engl. 1996, 35, 732.
(18) Duhme, A.-K.; Davis, S. C.; Hughes, D. L. Inorg. Chem. 1998, 37,
5380.
(19) Dunitz, J. D. Chem.sEur. J. 1998, 4, 745.
(20) Nakashima, T.; Mishiro, J.; Ito, M.; Kura, G.; Ikuta, Y.; Matsumoto,
N.; Nakajima, K.; Kojima, M. Inorg. Chem. 2003, 42, 2323.
(21) (a) Emara, A. A. A.; Khalil, S. M. E.; Salib, K. A. R. J. Coord. Chem.
1995, 289, 36. (b) Irwin, M. J.; Jia, G. C.; Vittal, J. J.; Puddephatt, R.
J. Organometallics 1996, 15, 5321.
(22) (a) Colacio, E.; Ghazi, M.; Kiveka¨s, R.; Moreno, J. M. Inorg. Chem.
2000, 39, 2882. (b) Navarro, J. A. R.; Freisinger, E.; Lippert, B. Inorg.
Chem. 2000, 39, 1059. (c) Masciocchi, N.; Ardizzoia, G. A.;
LaMonica, G.; Maspero, A.; Sironi, A. Angew. Chem., Int. Ed. 1998,
37, 3366.
Inorganic Chemistry, Vol. 43, No. 4, 2004 1563

Casado et al.
distilled under nitrogen immediately prior to use. The tetranuclear
complexes [Rh4(µ-PyS2)2(cod)4] and [Rh4(µ-PyS2)2(tfbb)4] were
prepared as described previously.10 Standard literature pro-
cedures were used to prepare CuCl and AgClO4. [Rh(µ-Cl)-
(cod)]2,26 [Rh(µ-Cl)(tfbb)]2,27 [AuCl(tht)],28 [AuCl(PPh3)],29 and
[Cu(CH3CN)]4[BF4]30 were prepared according to previously
reported methods. AgBF4 and CF3SO3Me were purchased from
Fluka Chem. and used as received.
Warning! Perchlorate salts are potentially explosiVe and should
only be handle with geat care and in small quantities.
1
Physical Measurements. H and 31P{1H} NMR spectra were
recorded on Varian UNITY and Bruker ARX 300 spectrometers
operating at 299.95 and 300.13 and 121.42 and 121.49 MHz,
respectively. 13C{1H} NMR spectra were recorded on Varian
Gemini 300 operating at 75.46 MHz. Chemical shifts are reported
in parts per million and referenced to Me4Si using the signal of the
deuterated solvent (1H and 13C) and 85% H3PO4 (31P) as external
reference, respectively. IR spectra were recorded on a Perkin-Elmer
783 spectrometer using Nujol mulls between polyethylene sheets
or in solution in a cell with NaCl windows. Elemental analyses
were performed with a Perkin-Elmer 240-C microanalyzer. Con-
ductivities were measured in ca. 5 × 10-4 M dichloromethane
solutions using a Philips PW 9501/01 conductimeter. Molecular
weights were determined with a Knauer osmometer using chloro-
form 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; 3-nitrobenzyl alcohol (NBA) was used as matrix. Electrical
conductivities were measured at room temperature on pellets made
of polycrystalline samples by the conventional two-probe method.31
n+
Figure 4. Possible cyclic structure for [CuRh4(µ-PyS2)2(cod)4]n (10)
containing four rhodium tetranuclear complexes (n ) 4). The cod ligands
have been omitted for clarity.
[{Ag(pymo)}n]‚2H2O,23 while the assembly of dinuclear
[{(CH2)n(PPh2)2}Au2]2+ complexes with the rigid-rod ligand
trans-1,2-bis(4-pyridyl)ethylene produces gold(I) coordina-
tion polymers for n ) 3 and 4 and rings containing four
gold(I) atoms for n ) 2.24
Compounds 5-12 exhibit a weak electric conductivity
in the solid state. Room-temperature conductivities of
pellets made of polycrystalline samples were in the range
(1.2-2.8) × 10-7 S cm-1, while the conductivities found
for related rhodium complexes behaving as insulators are
less than 10-8 S cm-1.25 Interestingly, neither 2,6-dimercap-
topyridine nor the tetranuclear complexes [Rh4(µ-PyS2)2(diole-
fin)4] are conductors under identical experimental conditions.
Preparation of the Complexes. [Rh4(µ-PyS2Me)2(cod)4]-
[CF3SO3]2 (1). CF3SO3Me (21 µL, 0.170 mmol) was added to a
solution of [Rh4(µ-PyS2)2(cod)4] (0.100 g, 0.088 mmol) in dichlo-
romethane (10 mL) to give a dark red solution. Concentration of
this solution to ca. 5 mL and further addition of methanol (5 mL)
gave a dark solid, which was removed by filtration through Celite.
Concentration of the resulting red solution to ca. 1 mL and addition
of methanol rendered the complex as a red microcrystalline solid,
which was filtered out, washed with methanol, and dried under
vacuum. Yield: 0.107 g (84%). Anal. Calcd for C46H60F6N2O6-
Rh4S6: C, 37.97; H, 4.16; N, 1.93. Found: C, 37.60; H, 3.74; N,
1.92. MS (FAB+, CH2Cl2, m/z): 1141 ([Rh4(PyS2Me)(PyS2)-
(cod)4]+, 4%), 945 ([Rh3(PyS2Me)2(cod)3]+, 58%), 578 ([Rh2(PyS2-
Me)(cod)2]+, 100%). ΛM (S cm2 mol-1): 157 (acetone, 4.94 × 10-4
Concluding Remarks
The two peripheral sulfur atoms in the tetranuclear
[Rh4(µ-PyS2)2(diolefin)4] (diolefin ) cod, tfbb) complexes
have nucleophilic character, as evidenced the reactions with
methyl triflate. Interestingly, the integrity of the tetranuclear
framework is sustained upon methylation of the bridging
ligands. Both complexes possess two juxtaposed donor sites
oriented in a divergent fashion available for coordination of
suitable metal ions and behave as chiral building blocks for
the construction of unusual coordination polymers and
heteropolynuclear complexes. Finally, it is worthwhile men-
tioning that the related iridium tetranuclear complexes
[Ir4(µ-PyS2)2(diolefin)4] (diolefin ) cod, tfbb) also have a
potential application as ligands. However, although both
rhodium and iridium complexes are redox-active species, the
iridium complexes are easily oxidized and their behavior as
ligands is frequently conditioned by redox processes.
1
M). H NMR (CD2Cl2, 298 K): δ 8.39 (d, 2H, JH-H ) 7.8 Hz),
7.53 (dd, 2H), 7.11 (d, 2H, JH-H ) 8.2 Hz) (PyS2Me ligands), 5.26
(m, 2H, dCH), 5.03 (m, 2H, dCH), 4.90 (m, 4H, dCH), 4.52 (m,
2H, dCH), 4.40 (m, 2H, dCH), 4.00 (m, 2H, dCH), 3.41 (m, 2H,
dCH) (cod ligands), 2.80 (s, 6H, PyS2Me), 3.0-1.5 (several m,
32H, >CH2) (cod ligands). 13C NMR (CD2Cl2, 298 K): δ 167.0,
156.0, 140.2, 130.4, 121.0 (PyS2Me ligands), 92.2 (d, JRh-C ) 11
Hz), 90.4 (d, JRh-C ) 13 Hz), 88.1 (d, JRh-C ) 11 Hz), 87.9 (d,
JRh-C ) 11 Hz), 87.0 (d, JRh-C ) 11 Hz), 86.9 (d, JRh-C ) 12 Hz),
86.5 (d, JRh-C ) 12 Hz), 79.7 (d, JRh-C ) 11.5 Hz) (dCH, cod
ligands), 34.9, 34.0, 33.0, 32.5, 29.2, 29.1, 28.4, 27.5 (>CH, cod
ligands), 17.9 (s, PyS2Me).
Experimental Section
General Methods and Starting Materials. All manipulations
were performed under a dry nitrogen atmosphere using Schlenk-
tube techniques. Solvents were dried by standard methods and
(23) Masciocchi, N.; Corradi, M.; Moret, M.; Ardizzoia, G. A.; Maspero,
A.; LaMonica, G.; Sironi, A. Inorg. Chem. 1997, 36, 5648.
(24) Irwin, M. J.; Vittal, J. J.; Yap, G. P. A.; Puddephatt, R. J. J. Am.
Chem. Soc. 1996, 118, 13101.
(25) (a) Anderson, J. E.; Gregory, T. P.; Net, G.; Bayo´n, J. C. J. Chem.
Soc., Dalton Trans. 1992, 487. (b) Bayo´n, J. C.; Net, G.; Esteban, P.;
Rasmussen, P. G.; Bergstrom, D. F. Inorg. Chem. 1991, 30, 4771.
(26) Giordano, G.; Crabtree, R. H. Inorg. Synth. 1979, 19, 218.
(27) Roe, D. E.; Masey, A. G. J. Organomet. Chem. 1971, 28, 273.
(28) Uson, R.; Laguna, A.; Laguna, M. Inorg. Synth. 1989, 26, 85.
(29) Braunstein, P.; Lehner, H.; Matt, D. Inorg. Synth. 1990, 27, 218.
(30) Kubas, G. J. Inorg. Synth. 1979, 19, 90.
(31) Ueyama, K.; Matsubayashi, G.; Tanaka, T. Inorg. Chim. Acta 1984,
87, 143.
1564 Inorganic Chemistry, Vol. 43, No. 4, 2004

Tetranuclear [Rh4(µ-PyS2)2(diolefin)4] Complexes
[Rh4(µ-PyS2)( µ-PyS2Me)(tfbb)4][CF3SO3] (2). CF3SO3Me
(5.70 µL, 0.047 mmol) was added to a solution of [Rh4(PyS2)2-
(tfbb)4] (0.075 g, 0.047 mmol) in dichloromethane (10 mL) to give
a violet solution, which was stirred for 2 h. Concentration of the
solution to ca. 1 mL and addition of hexane gave the complex as
a dark red microcrystalline solid, which was filtered off, washed
with hexane, and dried under vacuum. Yield: 0.075 g (90%). Anal.
Calcd for C60H33F19N2O3Rh4S5: C, 40.88; H, 1.88; N, 1.59.
Found: C, 40.82; H, 1.80; N, 1.62. MS (FAB+, CH2Cl2, m/z): 1613
([Rh4(PyS2Me)(PyS2)(tfbb)4]+, 100%), 1284 ([Rh3(PyS2Me)(PyS2)-
(tfbb)3]+, 25%), 814 ([Rh2(PyS2Me)(tfbb)2]+, 100%). ΛM (S cm2
[ClCuRh4(µ-PyS2)2(cod)4]n (5). Solid CuCl (0.066 g, 0.132
mmol) was added to a solution of [Rh4(µ-PyS2)2(cod)4] (0.075 g,
0.066 mmol) in dichloromethane (15 mL), and the solution was
stirred for 3 h. The resulting dark red solution was filtered through
Celite and then concentrated under vacuum to ca. 1 mL. Slow
addition of diethyl ether (10 mL) gave an orange solid, which was
filtered off, washed with diethyl ether, and dried under vacuum.
Yield: 0.059 g (80%). Anal. Calcd for C42H54ClCuN2Rh4S4: C,
41.15; H, 4.44; N, 2.28. Found: C, 41.02; H, 4.73; N, 2.26. MS
(FAB+, CH2Cl2, m/z): 1289 (ClCu2-[Rh4]+, 5%), 1227 (ClCu-
1
[Rh4]+, 12%), 1189 (Cu-[Rh4]+, 25%), 1126 ([Rh4]+, 81%). H
1
mol-1): 144 (acetone, 5.55 × 10-4 M). H NMR (CD2Cl2, 298
NMR (C6D6, 293 K, aromatic region): δ 8.40 (d, 2H), 7.90 (d,
2H), 6.90 (m, 4H), 6.80 (d, 2H), 6.55 (d, 2H), 6.40 (m, 2H), 6.30
(t, 2H), 6.05 (t) (PyS2). Mr found: 1730.
K): δ 8.27 (d, 1H, JH-H ) 7.3 Hz), 7.06 (dd, 1H), 7.00 (br, 1H)
(PyS2 ligand), 8.01 (d, 1H, JH-H ) 7.3 Hz), 7.26 (dd, 1H),, 6.86
(d, 1H, JH-H ) 8.0 Hz) (PyS2Me ligand), 6.17 (m, 1H, CH), 6.10
(m, 1H, CH), 5.96 (m, 1H, CH), 5.83 (m, 3H, CH), 5.69 (m, 2H,
CH), 5.42 (m, 1H, dCH), 4.86 (m, 2H, dCH), 4.72 (m, 1H,
dCH), 4.58 (m, 1H, dCH), 4.51 (m, 3H, dCH), 4.37 (m, 5H,
dCH), 4.23 (m, 1H, dCH), 4.17 (m, 1H, dCH), 3.99 (m, 1H,
dCH) (tfbb ligands), 2.79 (s, 3H, PyS2Me ligand). 13C NMR
(CD2Cl2, 298 K): δ 170.2, 167.4, 162.8, 152.3, 138.6, 137.6, 128.2,
125.7, 122.9, 118.3 (PyS2Me and PyS2 ligands), 140.0 (dm, JF-C
) 260 Hz), 138.0 (dm, JF-C ) 265 Hz), 127.5-125.8 (m) (C-F,
tfbb ligands), 68.5 (m), 64.8 (m), 62.6 (m), 61.8 (m), 59.9 (m),
58.3 (m), 55.0 (m), 54.5 (m), 49.9 (m), 41.2 (m), 39.9 (m), (dCH,
tfbb ligands), 39.8-39.3 (m) (CH, tfbb ligands), 17.6 (s, PyS2Me).
[ClCuRh4(µ-PyS2)2(tfbb)4]n (6). Solid CuCl (0.062 g, 0.062
mmol) was reacted with [Rh4(µ-PyS2)2(tfbb)4] (0.100 g, 0.062
mmol) in dichloromethane (15 mL) to give a purple suspension in
3 h. Concentration under vacuum and addition of methanol gave
the complex as a purple solid, which was filtered off, washed with
methanol, and dried under vacuum. Yield: 0.082 g (77%). Anal.
Calcd for C58H30ClCuF16N2Rh4S4: C, 41.03; H, 1.78; N, 1.65.
Found: C, 40.92; H, 1.75; N, 1.62. MS (FAB+, CH2Cl2, m/z): 1662
(Cu-[Rh4]+, 5%), 1597 ([Rh4]+, 100%).
[ClAuRh4(µ-PyS2)2(tfbb)4]n (7). Solid [AuCl(tht)] (0.020 g,
0.062 mmol) was added to a solution of [Rh4(µ-PyS2)2(tfbb)4]
(0.100 g, 0.062 mmol) in dichloromethane (10 mL) to give a dark
purple solution in 2 h. Concentration of the solution to ca. 1 mL
and slow addition of diethyl ether (10 mL) gave the complex as a
purple microcrystalline solid which was filtered off, washed with
diethyl ether and acetone, and dried under vacuum. Yield: 0.090
g (79%). Anal. Calcd for C58H30ClAuF16N2Rh4S4: C, 38.04; H,
1.65; N, 1.53. Found: C, 38.03; H, 1.59; N, 1.52. MS (FAB+,
CH2Cl2, m/z): 3392 (Au-[Rh4]2+, 60%), 1795 (Au-[Rh4]+, 10%),
1598 ([Rh4]+, 100%).
[(PPh3)2Au2Rh4(µ-PyS2)2(cod)4][ClO4]2 (3). Solid AgClO4 (0.027
g, 0.133 mmol) was added to a solution of [AuCl(PPh3)] (0.066 g,
0.133 mmol) in acetone (5 mL) to give a white suspension which
was stirred for 30 min in the dark. Silver chloride was removed by
filtration through Celite, and the resulting solution was reacted with
a solution of [Rh4(µ-PyS2)2(cod)4] (0.075 g, 0.066 mmol) in
dichloromethane (10 mL) for 1 h. Concentration of the dark red
solution to ca. 1 mL, and addition of methanol (10 mL) and diethyl
ether (5 mL) gave the complex as a red microcrystalline solid, which
was filtered off, washed with cold methanol, and vacuum-dried.
Yield: 0.111 g (75%). Anal. Calcd for C78H84Au2Cl2N2O8P2-
Rh4S4: C, 41.75; H, 3.77; N, 1.25. Found: C, 41.60; H, 3.90; N,
1.21. MS (FAB+, CH2Cl2, m/z): 1585 ([Rh4]-Au(PPh3)+, 100%),
1126 ([Rh4]+, 28%). ΛM (S cm2 mol-1): 200 (acetone, 3.72 × 10-4
[AgRh4(µ-PyS2)2(cod)4]n[BF4]n (8). A solution of AgBF4 (0.018
g, 0.095 mmol) in acetone (5 mL) was added to a solution of
[Rh4(µ-PyS2)2(cod)4] (0.107 g, 0.095 mmol) in dichloromethane
(15 mL). The dark red mixture was stirred for 1 h and then
concentrated under vacuum to ca. 1 mL. Addition of diethyl ether
(10 mL) gave the complex as a dark red solid, which was filtered
off, washed with diethyl ether and acetone, and dried under vacuum.
Yield: 0.106 g (84%). Anal. Calcd for C42H54AgBF4N2Rh4S4: C,
38.17; H, 4.12; N, 2.12. Found: C, 38.05; H, 3.92; N, 2.10. MS
(FAB+, CH2Cl2, m/z): 2361 (Ag-[Rh4]2+, 10%), 1235 (Ag-[Rh4]+,
1
M). H NMR (CDCl3, 293 K): δ 8.20 (d, 2H, JH-H ) 7.8 Hz,
PyS2), 7.60 (m, 18H, PPh3), 7.46 (m, 14H, PPh3 and PyS2), 7.32
(t, 2H, JH-H ) 7.8 Hz, PyS2), 5.15 (m, 2H, dCH), 4.90 (m, 4H,
dCH), 4.70 (m, 4H, dCH), 4.15 (m, 2H, dCH), 4.05 (m, 4H,
dCH), 3.30 (m, 2H, >CH2), 3.00-2.60 (m, 6H, >CH2), 2.65-
2.00 (m, 16H, >CH2), 1.90-1.50 (m, 8H, >CH2) (cod ligands).
31P NMR (CDCl3, 293 K): δ 36.0 (s).
1
80%), 1126 ([Rh4]+, 100%). H NMR (CDCl3, 218 K, aromatic
region): δ 8.70 (m), 8.08 (m), 7.96 (m), 7.88 (m), 7.70 (m), 7.64
(m), 7.54 (m), 7.10 (m), 6.80 (m), 6.62 (m), 6.46 (m) (PyS2 ligands).
[AgRh4(µ-PyS2)2(tfbb)4]n[BF4]n (9). The compound was pre-
pared from [Rh4(µ-PyS2)2(tfbb)4] (0.102 g, 0.064 mmol) and AgBF4
(0.012 g, 0.064 mmol) following the procedure described above.
The complex crystallized out in dichloromethane and was isolated
as a purple solid after concentration and addition of methanol (10
mL). Yield: 0.105 g (91%). Anal. Calcd for C58H30AgBF20N2-
Rh4S4: C, 38.84; H, 1.69; N, 1.56. Found: C, 38.68; H, 1.68; N,
1.57. MS (FAB+, CH2Cl2, m/z): 3304 (Ag-[Rh4]2+, 10%), 1706
(Ag-[Rh4]+, 35%), 1598 ([Rh4]+, 100%).
[CuRh4(µ-PyS2)2(cod)4]n[BF4]n (10). [Cu(CH3CN)]4[BF4] (0.022
g, 0.070 mmol) was added to a solution of [Rh4(µ-PyS2)2(cod)4]
(0.075 g, 0.066 mmol) in dichloromethane (10 mL). The dark red
mixture was stirred for 2 h and then filtered through Celite.
Concentration under vacuum to ca. 1 mL and addition of diethyl
ether (5 mL) and methanol (5 mL) gave the complex as a dark red
solid, which was filtered off, washed with methanol and acetone,
[(PPh3)2Au2Rh4(µ-PyS2)2(tfbb)4][ClO4]2 (4). An acetone solu-
tion of [Au(PPh3)(Me2CO)][ClO4] (0.094 mmol), prepared “in situ”
as described above, was reacted with [Rh4(µ-PyS2)2(tfbb)4] (0.075
g, 0.047 mmol) in dichloromethane (10 mL) to give a dark solution.
The complex was isolated as dark violet microcrystals by concen-
tration of the solution and addition of methanol (10 mL). Yield:
0.092 g (72%). Anal. Calcd for C94H60Au2Cl2F16N2O8P2Rh4S4: C,
43.15; H, 2.31; N, 1.07. Found: C, 43.00; H, 2.40; N, 1.07. MS
(FAB+, CH2Cl2, m/z): 2058 ([Rh4]-Au(PPh3)+, 100%), 1598
([Rh4]+, 23%). ΛM (S cm2 mol-1): 178 (acetone, 3.98 × 10-4 M).
1H NMR (CDCl3, 218 K): δ 8.29 (d, 2H, JH-H ) 7.5 Hz, PyS2),
7.8-7.4 (m, 30H, PPh3), 7.14 (d, 2H, JH-H ) 7.7 Hz, PyS2), 6.89
(dd, 2H, PyS2), 5.86 (m, 2H, CH), 5.70 (m, 4H, CH), 5.35 (m, 4H,
dCH), 5.30 (m, 2H, CH), 4.66 (m, 4H, dCH), 4.56 (m, 2H,
dCH), 4.36 (m, 2H, dCH), 4.13 (m, 2H, dCH), 3.96 (m, 2H,
dCH), (tfbb ligands). 31P NMR (CDCl3, 218 K): δ 36.6 (s).
Inorganic Chemistry, Vol. 43, No. 4, 2004 1565

Casado et al.
Table 2. Crystal Data and Refinement Parameters for Complex 4
and dried under vacuum. Yield: 0.071 g (84%). Anal. Calcd for
C42H54BCuF4N2Rh4S4: C, 39.50; H, 4.26; N, 2.19. Found: C,
39.30; H, 4.10; N, 2.14. MS (FAB*, CH2Cl2, m/z): 1189
(Cu-[Rh4]+, 10%), 1126 ([Rh4]+, 65%). 1H NMR (CDCl3,
218 K, aromatic region): δ 8.18 (d, JH-H ) 7.8 Hz), 7.82 (d, JH-H
) 7.8 Hz), 7.02 (dd) (PyS2).
[CuRh4(µ-PyS2)2(tfbb)4]n[BF4]n (11). The compound was pre-
pared from [Rh4(µ-PyS2)2(tfbb)4] (0.075 g, 0.047 mmol) and
[Cu(CH3CN)]4[BF4] (0.010 g, 0.047 mmol) by following the pro-
cedure described above. The complex crystallized out in dichlo-
romethane and was isolated as a purple garnet solid after concentra-
tion of the solution followed by addition of methanol (10 mL).
Yield: 0.065 g (79%). Anal. Calcd for C58H30BCuF20N2Rh4S4: C,
39.83; H, 1.73; N, 1.60. Found: C, 39.63; H, 1.59; N, 1.59. MS
(FAB+, CH2Cl2, m/z): 1660 (Cu-[Rh4]+, 20%), 1598 ([Rh4]+,
100%).
[Rh5(µ-PyS2)2(cod)5]n[BF4]n (12). Solid AgBF4 (0.035 g, 0.1775
mmol) was added to a solution of [Rh(µ-Cl)(cod)]2 (0.044 g, 0.088
mmol) in acetone (5 mL). The silver chloride was removed by
filtration through Celite, and the solution containing the solvated
species [Rh(cod)(Me2CO)2][BF4] was transferred to a solution of
[Rh4(µ-PyS2)2(cod)4] (0.100 g, 0.088 mmol) in dichloromethane
(15 mL). The resulting violet solution was stirred for 1 h and then
concentrated under vacuum to ca. 1 mL. Slow addition of diethyl
ether gave the complex as a violet microcrystalline solid, which
was filtered off, washed with diethyl ether, and dried under vacuum.
Yield: 0.114 g (90%). Anal. Calcd for C50H66BF4N2Rh5S4: C,
42.17; H, 4.67; N, 1.97. Found: C, 42.04; H, 4.44; N, 1.91. MS
(FAB+, CH2Cl2, m/z): 2464 ([Rh4]2-Rh(cod)+, 7%), 1337 ([Rh4]-
Rh(cod)+, 47%), 1229 ([Rh4]-Rh+, 16%), 1126 ([Rh4]+, 100%).
ΛM (S cm2 mol-1): 84 (acetone, 5.57 × 10-4 M).
empirical formula
C94H60Au2Cl2F16N2O8P2Rh4S4‚
2CH2Cl2‚C3H6O‚4C6H14
3288.71
fw
space group
a, Å
b, Å
P21/n (No. 14)
22.7939(12)
21.9335(11)
24.5094(12)
115.2690(10)
11 081.0(10)
4
1.971
3.560
19 583/159/1271
0.832
0.0548
c, Å
â, deg
V, Å3
Z
D
calcd, g cm-3
µ, mm-1
no. of data/restraints/param
GOF (all data)a
R1(F) (F2 g 2σ(F2))b
wR2(F2) (all data)c
0.1111
2
2
a GOF ) (Σ[w(Fo - Fc )2]/(n - p))1/2, where n and p are the number
of data and parameters. b R1(F) ) Σ||Fo| - |Fc||/Σ|Fo| for 10 069 observed
2
2
2
reflections. c wR2(F2) ) (Σ[w(Fo - Fc )2]/Σ[w(Fo )2])1/2, where w )
2
2
2
1/[σ2(Fo ) + (aP)2] and P ) [max(0, Fo ) + 2Fc ]/3.
The structure was easily solved by Patterson methods, com-
pleted by subsequent difference Fourier techniques, and refined by
full-matrix least squares on F2 (SHELXL-97)34 with initial iso-
tropic thermal parameters. After anisotropic refinement of all the
atoms of the polynuclear cationic metal complex, several electron
residuals were detected spread in the cell localized in quite a few
spatial regions. At this stage, the perchlorate anions were straight-
forwardly found, but one of them exhibits static disorder for three
oxygen atoms (O(6), O(7), and O(8)). Two solvation disordered
CH2Cl2 molecules were also identified in the subsequent difference
Fourier maps; both of them need a disorder modelation from two
overlapping dichloromethane molecules. A third acetone solvation
molecule was also recognized among the numerous electron
residuals. All the atoms involved in disorder (one perchlorate, two
CH2Cl2, and the acetone molecule) were refined as isotropic atoms
and maintained under geometric restrictions during refinement.
Hydrogen atoms were included in calculated positions for the
hexanuclear cation; their positional and displacement parameters
were incorporated in the least-squares refinement riding on carbon
atoms.
At this step, several residuals of significant electron density (3-4
e/Å3) were still present in the difference Fourier map; they did not
display significant short contacts to any of the already identified
and refined atoms. Several attempts to model this electron density
were carried out by considering the different solvent molecules used
in the crystallization process. Unfortunately no clear disorder model
could be established. As an alternative, an evaluation of potential
solvent regions showed the presence of four voids in the cell,
completing an approximate volume of 1878 Å3; an electron count
over this volume provided an estimate of 216 e/region (a total of
866 e in the cell).35 Bearing in mind the solvents used in the
crystallization, we interpreted these figures by assuming the
presence of four highly disordered hexane molecules (4 × 50
e/hexane molecule) in each of these four “solvent regions”.
Nevertheless, the contribution of the observed contents (electron
density) of these solvent regions to the total structure factors was
calculated via discrete Fourier transformation and incorporated in
[Rh5(µ-PyS2)2(tfbb)5]n[BF4]n (13). An acetone solution (5 mL)
of [Rh(tfbb)(Me2CO)2][BF4] (0.054 mmol), prepared as describe
above from [Rh(µ-Cl)(tfbb)]2 and AgBF4, was added to a solution
of [Rh4(µ-PyS2)2(tfbb)4] (0.087 g, 0.054 mmol) in dichloromethane
(15 mL) to give a deep violet solution in 1 h. Concentration of the
solution under vacuum to ca. 2 mL and addition of methanol gave
the complex as a violet solid which was filtered off, washed with
methanol, and dried under vacuum. Yield: 0.115 g (94%). Anal.
Calcd for C70H36BF4N2Rh5S4: C, 41.73; H, 1.80; N, 1.39. Found:
C, 41.53; H, 1.78; N, 1.39. MS (FAB+, CH2Cl2, m/z): 1927 ([Rh4]-
Rh(tfbb)+, 65%), 1701 ([Rh4]-Rh+, 7%), 1598 ([Rh4]+, 100%).
Structural Determination of Complex 4. A summary of crystal
data and refinement parameters for the structural analysis is given
in Table 2. Suitable crystals for the X-ray diffraction study were
obtained by slow diffusion of hexane into a concentrated solution
of 4 in a dichloromethane/acetone mixture. A dark violet irregular
shaped crystal (0.28 × 0.14 × 0.12 mm) of 4 was glued to a
glass fiber and mounted on Bruker SMART APEX diffractom-
eter. The instrument was equipped with a CCD area detector, and
data were collected using graphite-monochromated Mo KR radia-
tion (λ ) 0.710 73 Å) at low temperature (100 K). Cell constants
were obtained from the least-squares refinement of three-
dimensional centroids of 5264 reflections (4.9 e 2θ e 42.3°). Data
were measured (59 718 reflections (1.9e θ e 25.1°); 19 583 unique,
Rint ) 0.0932) through the use of CCD recording of narrow ω
rotation frames (0.3° each) and were integrated with the Bruker
SAINT program which includes Lorentz and polarization correc-
tions.32 Absorption correction was applied by using the SADABS
routine (minimum and maximum transmission factors 0.533 and
0.645).33
(33) Blessing, R. H. Acta Crystallogr., Sect. A 1995, 51, 33. SADABS:
Area-detector absorption correction, v. 2.03; Bruker-AXS: Madison,
WI, 2002.
(34) SHELXTL Package, v. 6.10; Bruker-AXS: Madison, WI, 2000.
Sheldrick, G. M. SHELXS-86 and SHELXL-97; University of Go¨ttin-
gen: Go¨ttingen, Germany, 1997.
(32) SAINT+, version 6.22; Bruker AXS Inc.: Madison, WI, 2001. SAINT,
(35) Farrugia, L. J. WINGX Package. J. Appl. Crystallogr. 1999, 32, 837.
Spek, A. L. Acta Crystallogr. 1990, A46, C34.
version 6.28; Bruker AXS Inc.: Madison, WI, 2001.
1566 Inorganic Chemistry, Vol. 43, No. 4, 2004

Tetranuclear [Rh4(µ-PyS2)2(diolefin)4] Complexes
the final least-squares refinement of the ordered part of the
structure.36 Data presented in Table 2 assume the presence of the
four hexane molecules in the independent part of the cell in addition
to the previously identified moieties (the polynuclear cation, two
anions, dichloromethane, and acetone). Atomic scattering factors
were used as implemented in the program.34
edged. We thank Dr. Elena Cerrada (Inorganic Chemistry
Department, University of Zaragoza) for the measurement
of the electrical conductivities.
Supporting Information Available: An X-ray crystallographic
file, in CIF format, containing full details of the structural analysis
of 4 and the observed and calculated fine structure of the molecular
Acknowledgment. Financial support from Ministerio de
Ciencia y Tecnolog´ıa (MCyT(DGI)/FEDER, Projects BQU-
2002-00074 and BQU2000-1170) is gratefully acknowl-
+
fragments Ag-[Rh4]2 and Ag-[Rh4]+ detected in the mass
spectrum of 8. This material is available free of charge via the
Internet at http://pubs.acs.org.
(36) Sluis, P. V. D.; Spek, A. L. Acta Crystallogr. 1990, A46, 194.
IC034893I
Inorganic Chemistry, Vol. 43, No. 4, 2004 1567