Novel thiophene-based cycloruthenated compounds: Synthesis, characterization, and reactivity

Article abstract of DOI:10.1021/ic101946n

The reactions between a series of thiophene-based imines with [(η⁶-C₆H₆)RuCl(μ-Cl)]₂, in a basic medium, and in MeCN give a family of ruthenacycles of stoichiometry [Ru(C^∧N)(NCMe)₄]PF₆ (C^∧N = orthometalated thiopheneimine). In these species, the C-H activation process is produced in most cases at the thiophene ring. When two C-H bonds are competing (thiophene vs aryl), the cyclometalation can be driven regioselectively to the thiophene unit or to the aryl ring as a function of the location of the iminic C = N bond. Cyclometalation can also be oriented to positions 2 or 3 of the thiophene depending on the situation of the imine in the heterocycle (3 or 2, respectively). In all studied cases, the η⁶-C₆H ₆ ligand was substituted by acetonitrile. The X-ray structures of two representative complexes have been determined. These thiophene-based metallacycles react with iodine under very mild conditions affording, after hydrolysis, substituted 3-iodo-2-formyl(benzo)thiophenes or substituted 2-iodo-3-formyl(benzo)thiophenes, as a function of the organometallic precursor.

Full text of DOI:10.1021/ic101946n

Inorg. Chem. 2011, 50, 37–45 37
DOI: 10.1021/ic101946n
Novel Thiophene-Based Cycloruthenated Compounds: Synthesis,
Characterization, and Reactivity
Luciano Cuesta,† Irene Maluenda,† Tatiana Soler,‡ Rafael Navarro,† and Esteban P. Urriolabeitia*,†
†
ꢀ
ꢀ
Departamento de Compuestos Organometalicos, Instituto de Ciencia de Materiales de Aragon, CSIC-
‡
ꢀ
ꢀ
Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza, Spain, and Servicios Tecnicos de Investigacion,
Facultad de Ciencias Fase II, Universidad de Alicante, 03690 San Vicente de Raspeig, Alicante, Spain
Received May 5, 2010
The reactions between a series of thiophene-based imines with [(η6-C6H6)RuCl(μ-Cl)]2, in a basic medium, and in
MeCN give a family of ruthenacycles of stoichiometry [Ru(C∧N)(NCMe)4]PF6 (C∧N = orthometalated thiophenei-
mine). In these species, the C-H activation process is produced in most cases at the thiophene ring. When two C-H
bonds are competing (thiophene vs aryl), the cyclometalation can be driven regioselectively to the thiophene unit or to
the aryl ring as a function of the location of the iminic CdN bond. Cyclometalation can also be oriented to positions 2 or
3 of the thiophene depending on the situation of the imine in the heterocycle (3 or 2, respectively). In all studied cases,
the η6-C6H6 ligand was substituted by acetonitrile. The X-ray structures of two representative complexes have been
determined. These thiophene-based metallacycles react with iodine under very mild conditions affording, after hydro-
lysis, substituted 3-iodo-2-formyl(benzo)thiophenes or substituted 2-iodo-3-formyl(benzo)thiophenes, as a function of
the organometallic precursor.
Introduction
cations.5 Although palladium is, without any doubt, the
transition metal that has been the most studied to promote
the formation of metallacycles,6 because cyclopalladated
compounds are known for numerous families of ligands to
date, it is well-known that other metals can be successfully
employed for the synthesis of cyclometalated species. In parti-
cular, cycloruthenated compounds have emerged in the past
Cyclometalation, discovered in the early 1960s, has become
one of the most popular and useful organometallic reactions,1
mainly because this strategy represents a mild route for acti-
vating C-H bonds selectively, displaying an enormous syn-
thetic potential. Metallacycles have been widely applied in
catalysis and metal-mediated organic syntheses,2 and in the
last years, a renewal of interest in these species has appeared,
motivated by the multiple applications exhibited by these
organometallic entities in several domains of the chemistry.
For example, they have been used as sensors,3 liquid-crystal
materials,4 anticancer agents, or other biorganometallic appli-
(5) (a) Severin, K.; Bergs, R.; Beck, W. Angew. Chem., Int. Ed. 1998, 37,
1634. (b) Dyson, P. J.; Sava, G. Dalton. Trans. 2006, 1929. (c) Kurzeev, S. A.;
Vilesov, A. S.; Fedorova, T. V.; Stepanova, E. V.; Koroleva, O. V.; Bukh, C.;
Bjerum, M. J.; Kurnikov, I. V.; Ryabov, A. D. Biochemistry 2009, 48, 4519.
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*To whom correspondence should be addressed. E-mail: esteban@unizar.
es. Fax: (þ0034)976761187.
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A. V. J. Organomet. Chem. 2004, 689, 4055. (e) Omae, I. J. Organomet. Chem.
2007, 692, 2608. (f) Selander, N.; Szabo, K. J. Dalton Trans. 2009, 627.
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r
2010 American Chemical Society
Published on Web 11/30/2010
pubs.acs.org/IC

38 Inorganic Chemistry, Vol. 50, No. 1, 2011
Cuesta et al.
Scheme 1. Synthesis of Ruthenacycles 2a-2h, Showing the Position of the C-H Bond Activated
few years as an extraordinarily versatile family of molecules,7
displaying interesting applications in several fields. For ex-
ample, their unique photophysical and electrochemical prop-
erties have been exploited in the design of sensitizers for solar
cells8 or electron shuttles in redox-catalyzed processes.9 In
addition, ruthenacycles have been found to display an ap-
pealing potential as antitumor agents10 and are among the
most active catalysts reported to date for transfer hydro-
genation reactions.11 It is also remarkable that ruthenium
derivatives have been successfully employed to promote
organic transformations, presenting in some cases behaviors
complementary to those of their much more studied palla-
dium counterparts.7
Various examples have appeared recently in the literature
dealing with the synthesis of ruthenacycles, implying the partici-
pation of a vast range of precursors and ligand settings.7
However, the number of cycloruthenated complexes from
heterocyclic rings is still scarce.12 Particularly interesting in
this aspect is the synthesis of thiophene-containing cyclome-
talated species, considering that thiophene-based materials
are a very important class of organic materials because of
their biological, electronic, magnetic, and optical properties.13
The combination of thiophene moieties with cycloruthenated
units could lead to a promising family of complexes with
potential in all of the aforementioned areas of chemistry and
materials science (solar cells, anticancer activity, electron shuttles,
etc.). Moreover, cycloruthenation could offer an attractive
alternative strategy for the selective syntheses of modified
thiophenes, which continue to attract the attention of synthetic
chemists because of their inherent interest (building blocks
for synthesis, biological activity, etc.).
For these reasons, we have studied cycloruthenation of
thiophene-based imines. We have found that these com-
pounds can be orthometalated selectively under mild condi-
tions. In addition, the cycloruthenated species are adequate
starting compounds for the synthesis of iodo-modified thio-
phenes, an unprecedented reaction in ruthenium complexes,
and which provide alternative pathways for the synthesis of
these interesting compounds.
Results and Discussion
(10) (a) Gaidon, C.; Jeannequin, P.; Bischoff, P.; Pfeffer, M.; Sirlin, C.;
Loeffler, J. P. J. Pharmacol. Exp. Ther. 2005, 315, 1403. (b) Leyva, L.; Sirlin,
C.; Rubio, L.; Franco, C.; Lagadec, R. L.; Spencer, J.; Bischoff, P.; Gaidon, J.;
Loeffler, C. P.; Pfeffer, M. Eur. J. Inorg. Chem. 2007, 3055. (c) Leyva, L.; Malek,
F.; Benzima, S.; Denis, J. M.; Gueulette, J.; Dufour, P.; Gaiddon, C.; Loeffler, J. P.;
Sirlin, C.; Pfeffer, M.; Bischoff, P. Lett. Drug Des. Discovery 2008, 5, 1.
(d) Meng, X.; Leyva, M. L.; Jenny, M.; Gross, I.; Benosman, S.; Fricker, B.;
Harlepp, S.; Hebraud, P.; Boss, A.; Wlosik, P.; Bischoff, P.; Sirlin, C.; Pfeffer, M.;
Loeffler, J. P.; Gaiddon, C. Cancer Res. 2009, 69, 5458. (e) Ruiz, J.; Vicente, C.;
de Haro, C.; Bautista, D. Dalton Trans. 2009, 5071.For excellent reviews
including noncyclometalated ruthenium complexes with anticancer properties,
see: (f) Dyson, P. J.; Sava, G. Dalton Trans. 2006, 1929. (g) Ronconi, L.; Sadler,
P. J. Coord. Chem. Rev. 2007, 251, 1633.
1. Synthesis of the Cycloruthenated Complexes. The
starting imines 1a-1o have been prepared using conven-
tional procedures (see the Experimental Section),14 which
consist of condensation of the appropriate formylthio-
phene with aniline, benzylamine, or 2-thienylmethylamine.
The imines 1a-1h were reacted with [(η6-C6H6)RuCl(μ-Cl)]2
and KPF6 (2:1:4 molar ratio) under the same experimen-
tal conditions as those reported previously by Pfeffer and
co-workers for cycloruthenation of amines (NaOH, 45 °C,
(11) (a) Dani, P.; Karlen, T.; Gossage, R. A.; Gladiali, S.; Van Koten, G.
Angew. Chem., Int. Ed. 2000, 39, 743. (b) Baratta, W.; Da Ros, P.; del Zotto, A.;
Sechi, A.; Zangrando, E.; Rigo, P. Angew. Chem., Int. Ed. 2004, 43, 3584.
(12) (a) Deeming, A. J.; Jayasuriya, S. N.; Arce, A. J.; Sanctis, Y. D.
Organometallics 1996, 15, 786. (b) Moorlag, C.; Clot, O.; Wolf, M. O.; Patrick,
B. O. Chem. Commun. 2002, 3028. (c) Koizumi, T.; Tomon, T.; Kanata, K.
Organometallics 2003, 22, 970. (d) Koizumi, T.; Tomon, T.; Kanata, K.
J. Organomet. Chem. 2005, 690, 4272. (e) Moorlag, C.; Wolf, M. O.; Bohne,
C.; Patrick, B. O. J. Am. Chem. Soc. 2005, 127, 6382. (f) Patra, S. K.; Bera, J. K.
Organometallics 2006, 25, 6054. (g) Lobana, T. S.; Bawa, G.; Castineiras, A.;
Butcher, R. J.; Zeller, M. Organometallics 2008, 27, 175.
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J. Heterocycl. Chem. 2008, 51, 6531.1b: Powell, A. B.; Brown, R. J.; Vavosudevan,
K. V.; Cowley, A. H. Dalton Trans. 2009, 2521.1c: Hwang, W.-S.; Wang,
D.-L.; Chiang, M. Y. J. Organomet. Chem. 2000, 613, 231.1f: Joly, G. D.;
Jacobsen, E. N. J. Am. Chem. Soc. 2004, 126, 4102.1g: Cremonesi, G.; Croce,
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687, 16.1i: Morimoto, T.; Sekiya, M. Chem. Lett. 1985, 9, 1731.1j: Macias, A.;
García, C.; De Blas, A.; Rodriguez, T.; Bastida, R.; Souza, A. An. Quim. 1992, 88,
337.1k: Imhof, W. J. Organomet. Chem. 1997, 533, 31.1l: Anderson, C.; Crespo,
M.; Font-Bardía, M.; Klein, A.; Solans, X. J. Organomet. Chem. 2000, 601,
22.1o: Sone, T. Bull. Chem. Soc. Jpn. 1964, 37, 1197.1q: Audoye, P.; Coumes,
R.-C.; Gaset, A.; Gorrichon, J.-P. Can. J. Chem. 1982, 60, 1148.
(13) For an excellent overview of recent research on thiopene-based
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17, 1581.

Article
Inorganic Chemistry, Vol. 50, No. 1, 2011 39
NCMe).15 Under these conditions, the orthoruthenated
derivatives [(C∧N)Ru(NCMe)4]PF6 (2a-2h; C∧N = cyclo-
ruthenated imine; see Scheme 1) were obtained in good
yields after flash chromatography over aluminum oxide.
Reactions carried out using 2-thienylamine or 2-for-
mylthiophene failed to afford cyclometalated derivatives
under the same experimental conditions, indicating that
the presence of the imine moiety as a directing group is
critical. It was also noted that [(η6-C6H6)RuCl(μ-Cl)]2
was a better starting material for obtaining the desired
result and that the method is applicable to a wide variety
of substrates.
C-H bond activation at the thiophene unit in 2a-2e
occurs as expected because cyclometalation of the aryl
ring is, in principle, disfavored by the fact that it would
lead to the formation of highly strained four-membered
metallacycles. More interestingly, when these reaction
conditions were applied to the thiophene-based benzyla-
mines 1f and 1g, where both the heterocycle and the arene
units are capable of forming five-membered metalla-
cycles, only the thiophene moiety undergoes cyclometala-
tion through C-H activation, yielding complexes 2f and
2g. Therefore, the size of the resulting metallacycle is not a
discriminating factor for the orientation of cycloruthena-
tion, and other parameters have to be considered. The
preferred orthometalation of the electron-rich thiophene
ring, compared with the aryl ring, is in good agreement
with a SEAr mechanism operating for C-H bond activa-
tion, in line with previous observations and with the higher
reactivity toward electrophiles of the heterocycle versus
the arene.17 In addition, we have to consider that in
complexes 2a-g the iminic CdN bond belongs to the
ruthenacycle; that is, it is endocyclic. These types of endo
structures are typically more stable than the correspond-
ing ones with the CdN bond exocyclic (for instance, those
derived from ruthenation at the aryl ring) because of
the endo effect.18 This thermodynamic effect is related to
the additional stabilization gained by conjugation of the
π-electron density of the CdN double bond, that of the
heterocycle, and the appropriate orbitals of the metal. In
our experience in dealing with palladium complexes and
different types of ligands, the endo effect could be a very
strong directing factor and its importance should not be
neglected.18k-n,19 Aiming to determine the importance of
the endo effect in the outcome of these reactions, we have
carried out cycloruthenation of the bis(imine)thiophene
1h, which contains two nonequivalent thiophene rings,
and this allowed us to minimize the influence of the nature
of the aromatic ring. When imine 1h was reacted with [(η6-
C6H6)RuCl(μ-Cl)]2 under the same experimental conditions
cycloruthenatedderivativesthan[(η6-p-MeC6H4 Pr)RuCl-
i
(μ-Cl)]2, an observation commonly interpreted as an indi-
cation of the operation of an SEAr mechanism.7
Complexes 2a-2h were fully characterized by NMR
spectroscopy, elemental analyses, and mass spectrome-
try. In addition, complexes 2b and 2f were characterized
by X-ray diffraction methods (see the crystallographic
analyses section). In all studied cases, C-H bond activa-
tion takes place regioselectively at the heterocyclic ring,
despite the presence of diverse C-H bonds suitable for
activation or different directing groups (the imine N
atom and the sulfur S atom). Activation of the proton
at the 3 position on the thiophene ring is inferred from
the 1H NMR spectra of 2a-2h, which showed the disap-
pearance of the characteristic resonance of H3 of the thiophene
moiety. The presence of C3 σ-bound to the ruthenium
center was evidenced by an extremely low-field signal in
the 13C NMR spectra (about 200 ppm). Analysis of the
spectroscopic data also indicates that the η6-C6H6 ring
was replaced by acetonitrile ligands, leading to the forma-
tion of octahedral species where the ruthenium coordina-
tion sphere is formed by the cyclometalated ligand, bound
to the metallic center through the N atom of the imine and
one carbon of the thiophene moiety, and four acetonitrile
ligands. Displacement of the arene ligands by acetonitrile
is a rather common process in the chemistry of the cyclo-
ruthenated species16 and is attributed to the weakening of
the metal-arene bond by the strong coordinating char-
acter of the cyclometalated ligand.7,15
Remarkably, the reaction tolerates the presence of
alkyl and aryl groups in the thiophene moiety, as demon-
strated by the formation of complexes 2c and 2d, containing
a methyl group and a phenyl group, respectively (Scheme 1).
However, when we attempted orthometalation of imines
with electron-withdrawing substituents such as chlorine
[SC4H2-2-(CHdNPh)-5-Cl] (1p) or nitro [SC4H2-2-(CHd
NPh)-5-NO2] (1q), no transformation was observed, sug-
gesting once more that C-H bond activation occurs
through a SEAr mechanism, in line with previous obser-
vations. It is worth noting that this synthetic strategy
seems to be valid not only for substituted thiophenes but
also for benzothiophenes. For example, the benzothio-
pheneimine 1e (Scheme 1) can be successfully ortho-
metalated by reaction with [(η6-C6H6)RuCl(μ-Cl)]2 under
the conditions described above. The compound obtained,
2e, has incorporated the Ru atom at position 3 of the benzo-
thiophene ring, showing that the presence of the fused aryl
ring does not have a significant influence on the reaction
(17) For example, thiophene brominates 107 times faster than does
benzene. See: (a) Swanston, J. Thiophene. Ullmann’s Encyclopedia of
Industrial Chemistry; Wiley-VCH: Weinheim, Germany, 2006. For an overview
of electrophilic substitutions of five-menbered rings, see: (b) Merino, G. Adv.
Heterocycl. Chem. 1975, 13, 235.
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Organometallics 1992, 11, 1536. (b) De Munno, G.; Ghedini, M.; Neve, F.
Inorg. Chim. Acta 1995, 239, 155. (c) Albert, J.; Granell, J.; Sales, J.; Font-Bardía,
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M.; Solans, X. Organometallics 1995, 14, 1393. (d) Gomez, M.; Granell, J.;
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Martínez, M. Organometallics 1997, 16, 2539. (e) Gomez, M.; Granell, J.;
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Martínez, M. J. Chem. Soc., Dalton Trans. 1998, 37. (f) Gomez, M.; Granell, J.;
Martínez, M. Eur. J. Inorg. Chem. 2000, 217. (g) Gorunova, O. N.; Keuseman,
K. J.; Goebel, B. M.; Kataeva, N. A.; Churakov, A. V.; Kuz'mina, L. G.; Dunina,
V. V.; Smoliakova, I. P. J. Organomet. Chem. 2004, 689, 2382. (h) Keuseman,
K. J.; Smoliakova, I. P.; Dunina, V. V. Organometallics 2005, 24, 4159. (i) Bielsa,
R.; Larrea, A.; Navarro, R.; Soler, T.; Urriolabeitia, E. P. Eur. J. Inorg. Chem.
2005, 1724. (j) Mawo, R. Y.; Mustakim, S.; Young, V. G., Jr.; Hoffmann, M. R.;
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Smoliakova, I. P. Organometallics 2007, 26, 1801. (k) Aguilar, D.; Arag€ues,
M. A.; Bielsa, R.; Serrano, E.; Navarro, R.; Urriolabeitia, E. P. Organometallics
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2007, 26, 3541. (l) Aguilar, D.; Arag€ues, M. A.; Bielsa, R.; Serrano, E.; Soler, T.;
Navarro, R.; Urriolabeitia, E. P. J. Organomet. Chem. 2008, 693, 417. (m) Bielsa,
R.; Navarro, R.; Soler, T.; Urriolabeitia, E. P. Dalton Trans. 2008, 1203.
(n) Bielsa, R.; Navarro, R.; Soler, T.; Urriolabeitia, E. P. Dalton Trans. 2008,
1787.
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(15) Fernandez, S.; Pfeffer, M.; Ritleng, V.; Sirlin, C. Organometallics
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(19) (a) Bielsa, R.; Navarro, R.; Urriolabeitia, E. P.; Lledos, A. Inorg.
1999, 18, 2390.
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(16) Recent example not included in ref 7: Djukic, J.-P.; Fetzer, L.; Czysz,
A.; Iali, W.; Sirlin, C.; Pfeffer, M. Organometallics 2010, 29, 1675.
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40 Inorganic Chemistry, Vol. 50, No. 1, 2011
Cuesta et al.
Scheme 2. Synthesis of Thiophene-Based Ruthenacycles 2i and 2j
as those described for 1a-1g, complex 2h was isolated as
the only organometallic product, and it was characterized
as the endo isomer (Scheme 1). The endo arrangement
was determined by selective NOESY-1D experiments,
where it was found that irradiation of the signal at 5.12
ppm, attributed to the CH2 moiety, causes enhancement
of the signals at 8.42 and 7.08 ppm, assigned respectively
to the imine proton and the thienyl H atom located in the
β position of the nonmetalated heterocyclic ring. This fact
implies that the thiophene connected to the CH2 unit
keeps the three protons and, therefore, indicates that
metalation has taken place in the other thiophene moiety.
Irradiation of the imine proton only gave enhancement of
the CH2 unit, as expected for an endo complex. These
observations permit one to conclude that when similar
electronic conditions are present, the C-H activation
process seems to favor formation of the isomer with an
endo configuration because it is thermodynamically more
stable.19 It should be noted here that analysis of the
reaction crudes has not allowed detection of the presence
of exo isomers, although their existence could not be fully
discarded.
Once the importance of CdN bond location in systems
with similar electron densities was probed (two thiophene
rings in 2h), the next step was investigation of the selec-
tivity of the process when the imine does not belong to the
thiophene moiety. The reaction of the Schiff bases 1i and
1j with [(η6-C6H6)RuCl(μ-Cl)]2 under the same condi-
tions as those described above yielded complexes 2i and 2j
(see Scheme 2), where the benzyl rings were cyclome-
talated selectively.
The regiochemistry of 2i and 2j was initially inferred
from the spectroscopic NMR data, where the lack of one
of the aryl protons is observed and the thiophene integrity
is retained, and, once more, the spectroscopic data in-
dicated that the benzene unit is replaced by acetonitrile
ligands. These structural characteristics were confirmed,
in the case of 2j, by an X-ray diffraction study. The poor
quality of the data provides a structure not amenable for a
discussion of the distances and angles. However, it clearly
confirms the connectivity deduced from the NMR data.
A drawing of the cation present in 2j is showed in Figure 1.
Formation of the endo complexes 2i and 2j is com-
pletely regioselective despite the fact that the thiophene
ring seems to be more prone to undergo cyclometalation,
assuming a SEAr mechanism for C-H bond activation.
Therefore, formation of 2i and 2j indicates that the
thermodynamic endo effect is a critical factor in control-
ling the regiochemistry of these reactions. As a far as we
know, the importance of this effect in the formation of
ruthenacycles has never been noted previously.
Figure 1. Side view of complex 2j showing the labeling scheme.
as shown in the Scheme 3. The use of the imines 1k-1n
(see Scheme 3) presents the same problem of competitive
orthometalation between the thiophene and aryl rings.
The presence of the iminic CdN double bond at the 3
position of the thiophene moiety ensures, in principle,
formation of the endocyclic isomer by C-H bond activa-
tion at the heterocyclic ring. However, even for the endo-
cyclic compound, two different positions, 2 and 4, could
be activated, affording two different isomers. The reaction
of the imines 1k-1n with [(η6-C6H6)RuCl(μ-Cl)]2, always
using the same experimental conditions, affords the cor-
responding orthoruthenated derivatives 2k-2n, as shown
in Scheme 3. Replacement of the benzene ring by acet-
onitriles also takes place in these reactions. All complexes
were fully characterized by analytical and spectroscopic
methods, following the same key features as those de-
scribed for 2a-2j.
In all cases studied, metalation gives the expected endo
derivatives and, moreover, it has occurred selectively at
the 2 position of the thiophene, as expected for the higher
reactivity of this position in electrophilic substitution
processes.20 Traces of other isomers were not observed
in the reaction crudes. The reaction is, therefore, totally
regioselective with respect to the ring to be metalated and
to the position of metalation on the thiophene. As pre-
viously explained, the endo effect is responsible of the
selective metalation of 1k-1m (the endo character of
complex 2m was determined by selective NOESY-1D
experiments) because the same pattern of reactivity as
that observed in 2a-2h is found here. However, even if
metalation at the 2 position is the most favored process,20
selectivity of the reaction is noteworthy in the case of 1n
because metalation at the 5 position of benzothiophene,
with concomitant formation of a six-membered ruthena-
cycle, could be competitive with the formation of 2n.
To test the possibility of achieving a double cycloruthe-
nation over the same thiophene ring, the 2,5-bis(imine)-
thiophene 1o was treated with the ruthenium source [(η6-
C6H6)RuCl(μ-Cl)]2 and KPF6 (1:1:4 molar ratio), in a basic
medium and with acetonitrile as the solvent, affording
The synthetic strategy described above can be easily
expanded for the synthesis of complexes in which C-H
activation has occurred at the 2 position of the thiophene,
(20) Katritzky, A. R.; Taylor, R. Electrophilic Substitution of Hetero-
cycles, Quantitative Aspects, Advances in Heterocyclic Chemistry Series;
Academic Press: San Diego, CA, 1990; Vol. 47.

Article
Inorganic Chemistry, Vol. 50, No. 1, 2011 41
Scheme 3. Synthesis of Ruthenacycles 2k-2n, Showing the Position of the C-H Bond Activated
Scheme 4. Orthometalation of the Bis(imine) 1o
monocycloruthenated complex 2o as the only organometal-
lic compound, as shown in Scheme 4. We have attempted
different metal/ligand molar ratios and different reaction
conditions, but in all cases, 2o was the only detected
species. Probably the presence of the strongly electron-
attracting ruthenium metal on the heterocycle deactivates
it toward a second orthoruthenation. The presence of
three singlets in the 1H NMR spectrum of 2o (two imine
protons and one thiophene proton) accounts for activa-
tion of only one of the two heterocyclic protons. Incor-
poration of only one Ru(NCMe)4 unit to the thiophene
moiety is evident from the 1H and 13C NMR spectra but
also from the obtained values of elemental analysis and
mass spectrometry.
In summary, we have obtained cycloruthenated com-
plexes through C-H bond activation of different thio-
pheneimine-based ligands. The presence of the imine
moiety as a directing group is critical to achieving ortho-
metalation. The reaction is totally regioselective and, in
all cases, seems to be driven by the endo effect. The
presence of the ruthenium center in different selected
points of the thiophene skeleton opens the possibility of
further modification of these substrates in a regioselective
manner.
most commonly used approaches (e.g., SEAr or directed
lithiation) and (b) eliminates the need to use electron-rich
substrates or strong acids/bases. However, as far as we
know, no other metal has never been successfully em-
ployed to promote the selective orthohalogenation of
organic substrates via cyclometalation. We present here
the first examples in which a non-palladium-based me-
tallacycle has been demonstrated to react with halogens,
providing reliable access to key compounds.
The reaction of 2a with I2 in wet acetonitrile affords,
after hydrolysis “in situ”, the corresponding 2-formyl-3-
iodothiophene 3a (Scheme 5),23 which can be extracted
from the crude mixture with Et2O.
This halogenation process seems to be general and
tolerates different functional groups. The reaction of 2c
and 2d with elemental iodine, under the same experimen-
tal conditions, affords the corresponding 5-methyl-3-
iodo-2-formylthiophene (3c) and 5-phenyl-3-iodo-2-for-
mylthiophene (3d) in very good yields. Characterization
of 3c and 3d as iodine derivatives is clear from the
observation of signals at 96.8 and 105.0 ppm, respectively,
in the 13C NMR spectra, typical of the C-I groups.24
Moreover, treatment of the benzothiophene complex 2e
affords in a clean way 3-iodo-2-formylbenzothiophene
(3e), showing the versatility of the method. Reactions
carried out under analogous conditions with metal-free
imines failed to afford the respective halogenated compounds,
2. Iodination Reactions. Halogenation of aromatic
compounds is one of the fundamental reactions in organic
chemistry.21 The use of palladacycles as intermediates for
the introduction of the halogen functional group has
emerged as an attractive strategy22 because it (a) displays
a complete regioselectivity for orthohalogenated com-
pounds, thus providing a complementary method to the
(23) Synthesis of 3-iodo-2-formylthiophene (3a): (a) Antonioletti, R.;
D’Auria, M.; D’Onofrio, F.; Piancatelli, G.; Scettri, A. J. Chem. Soc., Perkin
Trans. 1 1986, 1755. (b) Guillard, R.; Fournari, P.; Person, M. Bull. Soc. Chim.
Fr. 1967, 4121. (c) Sonoda, M.; Kinoshita, S.; Lu, T.; Fukuda, H.; Miki, K.;
Umeda, R.; Tobe, Y. Synth. Commun. 2009, 39, 3315. Synthesis of 2-iodo-3-
formylthiophene (3n): Wunderlich, S. H.; Knochel, P. Angew. Chem., Int. Ed.
2007, 46, 7685. Synthesis of 2-iodo-3-formylthiophene (3k): Gronomitz, S.;
Dahlgren, T. Chem. Scr. 1977, 12, 57.
(21) (a) Taylor, R. Electrophilic Aromatic Substitution; Wiley: New York,
1990. (b) De La Mare, P. B. Electrophilic Halogenation; Cambridge University
Press: Cambridge, U.K., 1976; Chapter 5.
(22) (a) Kalyani, D.; Dick, R. A.; Anani, Q. W.; Sanford, M. S. Tetra-
hedron 2006, 62, 11483. (b) See ref 2g. (c) Giri, R.; Chen, X.; Yu, J.-Q. Angew.
Chem., Int. Ed. 2005, 44, 2112.
€
´
(24) Prestch, E.; Buhlman, P.; Affolter, C.; Herrera, A.; Martınez, R.
ꢀ
Structural Determination of Organic Compounds; Springer-Verlag Iberica:
Barcelona, Spain, 2001.

42 Inorganic Chemistry, Vol. 50, No. 1, 2011
Cuesta et al.
Scheme 5. Syntheses of the Iodinated Thiophenes 3a, 3c-3e, 3k, and 3n
demonstrating the fundamental role played by the ruthe-
nium complex. The water in NCMe promotes the final
hydrolysis of the putative haloimine intermediate to give
the haloaldehyde.
This method can also be applied to the synthesis of
other haloformylthiophenes. Therefore, the reaction 2k
or 2n with I2 in wet acetonitrile affords the corresponding
2-iodo-3-formylthiophene (3k) or 2-iodo-3-formylbenzo-
thiophene (3n). These compounds can be isolated in pure
form following the same workup as that described pre-
viously for 3a and 3c-3e.
These results offer a promising new synthetic strategy for
the formation of 3-iodo-2-formylthiophenes and 2-iodo-3-
formylthiophenes, key precursors in the production of
multiple thiophene-based materials. This strategy, more-
over, is of considerable interest because, contrary to all of
the procedures described previously,23 it offers a synthetic
pathway for the selective introduction of a halogen ortho to
a preexisting aldehyde inposition 2, a regiochemistrythatis
especially difficult to achieve in this kind of heterocycle
because positions 4 and 5 are typically more reactive.
The advantage of this method in terms of accessibility
and selectivity is counterbalanced by the drawback of the
use of stoichiometric quantities of ruthenium. This makes
this method noncompetitive with the traditional organic
procedures when simple compounds such as 3a are
considered.23 However, in the case of the more substi-
tuted derivatives, this method can be considered as at
least an alternative to the usual preparative procedures,
avoiding the use of unstable lithium intermediates, which
are difficult to handle and require very low temperatures
and where, in some cases, it is difficult to control the
position of lithium incorporation. In addition, as far as
we know, catalytic halogenation of the heterocycles has
not been carried out using palladacycles, in spite of
impressive recent developments on arylic substrates.2g
3. Crystallographic Analysis of 2b and 2f. The crystal
structures of complexes 2b and 2f have been determined
by X-ray diffraction methods. Representations of the
cations present in 2b and 2f are shown in Figures 2 and
3, respectively. The two molecules are isostructural and
show the Ru atom in an octahedral environment, sur-
rounded by the C and N atoms of the orthometalated
thiopheneimine ligand and by the four N atoms of the
four acetonitrile ligands.
Figure 2. Side view of the cation of 2b. The PF6 counteranion has been
removed for clarity. Selected distances (A) and angles (deg): Ru(1)-C(5)
1.950(9), Ru(1)-N(1) 2.081(8), Ru(1)-N(2) 1.975(9), Ru(1)-N(3)
1.992(9), Ru(1)-N(4) 2.076(8), Ru(1)-N(5) 1.995(9); C(5)-Ru(1)-N(1)
79.6(3), N(2)-Ru(1)-N(1) 89.4(3), N(3)-Ru(1)-N(5) 89.9(4), N(5)-
Ru(1)-N(1) 92.0(3).
Figure 3. Side view of the cation of complex 2f. The PF6 counteranion
has been removed for clarity. Selected distances (A) and angles (deg):
Ru(1)-C(5) 2.018(3), Ru(1)-N(1) 2.069(2), Ru(1)-N(2) 2.010(2), Ru-
(1)-N(3) 2.139(3), Ru(1)-N(4) 2.006(3), Ru(1)-N(5) 2.024(3); C(5)-
Ru(1)-N(1) 79.81(11), N(2)-Ru(1)-N(1) 86.71(9), N(5)-Ru(1)-N(1)
170.49(10), N(4)-Ru(1)-N(5) 90.72(10).
ties.12a,e-g This shorter distance could be related to the
large downfield shift observed in the 13C NMR spectrum
for this carbon, suggesting a partial double-bond char-
acter. This fact has been observed in other ruthenium
complexes.12b,e The Ru-N bond lengths imply that the
The distance Ru(1)-C(5) [1.950(9) A] in 2b is shorter
than those observed for other ruthenacycles [range: 2.076(3)-
2.114(4) A] containing cyclometalated thiophene moie-

Article
Inorganic Chemistry, Vol. 50, No. 1, 2011 43
chelating imine falls in the usual range of distances found
in related structural arrangements.12 As expected, the Ru-
N bond distance for the nitrile located in a trans posi-
tion with respect to the metalated carbon, Ru(1)-N(3), is
slightly longer than the others because of the large trans
influence of the σ-bound carbon.
The geometric features of 2f are similar to the ones
observed for 2b, with a C(5)-Ru(1) bond distance of
2.018(3) A and a little longer Ru-N distance [Ru(1)-
N(3) 2.139(3) A] for the MeCN situated trans to the meta-
lated carbon. Other structural parameters are as expected
and do not merit further comments.
(s, C), 141.8 (s, C), 133.8 (s, C), 133.3 (s, CH), 129.3 (s, CH),
129.2 (s, CH), 129.0 (s, CH), 126.1 (s, CH), 126.0 (s, CH), 123.6
(s, CH), 121.1 (s, CH).
Imine 1e [SC8H5-2-(CHdNPh)]. Yield: white solid (0.578 g,
97%). Anal. Calcd for C15H11NS: C, 75.92; H, 4.67; N, 5.90; S,
13.51. Found: C, 75.63; H, 4.51; N, 5.75; S, 13.27. MS (ESIþ):
m/z 238.0 ([M þ H]þ). 1H NMR (CDCl3): δ 8.71 (s, 1H,
NdCH), 7.92-7.84 (m, 2H, C6H4), 7.73 (s, 1H, thiophene),
7.46-7.40 (m, 4H, 2 C6H4 þ 2 Ph), 7.31-7.28 (s, 3H, Ph).
13C{1H} NMR (CDCl3): δ 158.6 (s, CH), 151.1 (s, C), 143.0 (s,
C), 141.1 (s, C), 139.3 (s, C), 129.6 (s, CH), 129.2 (s, CH), 126.5
(s, CH), 126.4 (s, CH), 124.8 (s, CH), 124.7 (s, CH), 122.9 (s,
CH), 121.13 (s, CH).
Imine 1m [SC4H3-3-(CHdNC4H3S)]. Yield: orange oil (0.491
g, 95%). Anal. Calcd for C10H9NS2: C, 57.94; H, 4.38; N, 6.76;
S, 30.93. Found: C, 57.41; H, 4.23; N, 6.25; S, 30.39. MS (ESIþ):
m/z 207.9 ([M þ H]þ). 1H NMR (CDCl3): δ 8.36 (s, 1H,
NdCH), 7.64 (m, 2H), 7.33 (m, 1H), 7.27 (s, 1H), 7.04 (m,
2H), 4.96 (s, 2H, CH2). 13C{1H} NMR (CDCl3): δ 156.6 (s, CH),
142.1 (s, C), 140.3 (s, C), 129.2 (s, CH), 127.0 (s, CH), 126.6 (s,
CH), 125.9 (s, CH), 125.1 (s, CH), 124.9 (s, CH), 59.3 (s, CH2).
Imine 1n [SC8H5-3-(CHdNPh)]. Yield: pale-yellow solid
(0.571 g, 96%). Anal. Calcd for C15H11NS: C, 75.92; H, 4.67;
N, 5.90; S, 13.51. Found: C, 75.67; H, 4.70; N, 5.70; S, 13.15. MS
Conclusion
In this Article, we present a versatile strategy for the synthe-
sis of thiophene-based cycloruthenated compounds employ-
ing imine units as directing groups. The regiochemistry of
these processes is governed by the endo effect, which permits
one to direct C-H activation to the heterocycle or to the
arene unit. Reactions between these novel organometallic
entities and iodine allow for the practical and reproducible
syntheses of iodinated formylthiophenes, a strategy based on
an unprecedented selective halogenation of ruthenacycles.
1
(ESIþ): m/z 237.9 ([M þ H]þ). H NMR (CDCl3): δ 9.00 (dd,
1H, C6H4, 3JHH = 8.40, 4JHH = 1.20), 8.75 (s, 1H, NdCH), 7.99
(s, 1H, thiophene), 7.91 (dd, 1H C6H4, JHH = 7.80, JHH =
3
4
0.60), 7.56-7.44 (m, 4H, 2 C6H4 þ 2 Ph), 7.30-7.28 (s, 3H, Ph).
13C{1H} NMR (CDCl3): δ 154.9 (s, CH), 152.6 (s, C), 140.9 (s,
C), 136.6 (s, C), 134.8 (s, CH), 134.3 (s, C), 129.3 (s, CH), 125.9
(s, CH), 125.6 (s, CH), 125.5 (s, CH), 125.4 (s, CH), 122.6 (s,
CH), 121.0 (s, CH).
Experimental Section
General Methods. Solvents were dried and distilled using
standard procedures before use. All reactions were carried out
under an argon atmosphere using standard Schlenk techniques.
Elemental analyses were carried out with a Perkin-Elmer 2400-B
microanalyzer. 1H, 13C, 31P, and 19F NMR spectra were recorded
in CD3CN or CDCl3 solutions at 25 °C on Bruker AV300,
AV400, or Varian Gemini 300 spectrometers (δ in ppm and J in
Hz) at a 1H NMR operating frequency of 300.13 or 400.13 MHz.
1H and 13C NMR spectra were referenced using the solvent
signal as an internal standard, while 19F NMR spectra were
referenced to CFCl3 and 31P NMR spectra were externally
referenced to H3PO4 (85%). The SELNO-1D 1H NMR experi-
ments were performed with optimized mixing times (D8),
depending of the irradiated signal. Positive-mode electrospray
ionization mass spectrometry (ESIþ MS) spectra were recorded
using an Esquire 3000 ion-trap mass spectrometer (Bruker Daltonic
GmbH) equipped with a standard ESI/APCI source. Samples
were introduced by direct infusion with a syringe pump. Nitrogen
served as both the nebulizer gas and the dry gas.
Imine 1p [SC4H3-2-(CHdNPh)-5-Cl]. Yield: orange solid
(0.511 g, 92%). Anal. Calcd for C11H8NSCl: C, 59.59; H, 3.64;
N, 6.32; S, 14.46. Found: C, 59.34; H, 3.39; N, 6.28; S, 13.99. MS
(ESIþ): m/z 221.9 ([M þ H]þ). 1H NMR (CDCl3): δ 8.34 (s, 1H,
NdCH), 7.31-7.28 (s, 2H), 7.18-7.11 (m, 4H), 6.88 (d, 1H,
3
thiophene, JHH = 5.20). 13C{1H} NMR (CDCl3): δ 151.5 (s,
CH), 150.3 (s, C), 141.0 (s, C), 135.2 (s, C), 130.8 (s, CH), 128.6
(s, CH), 126.4 (s, CH), 125.7 (s, CH), 120.4 (s, CH).
Ruthenacycles: General Procedure. To a suspension of [(η6-
benzene)RuCl(μ-Cl)]2 (0.100 g, 0.2 mmol), NaOH (0.016 g, 0.4
mmol), and KPF6 (0.146 g, 0.8 mmol) in MeCN (25 mL) was
added the corresponding imine (0.4 mmol), and the mixture was
stirred at 45 °C under argon for 48 h. The resulting solution was
evaporated in vacuo to dryness. The residue was purified by
flash chromatography over Al2O3 using MeOH/DCM (1-3%)
as the eluent, the orange fraction was collected and concentrated
in vacuo to a minimum volume, and a solid precipitated upon
the addition of Et2O (15 mL). The precipitate was washed
several times with Et2O, affording the desired product. The
complexes appeared to be very sensitive to oxidation, turning
quickly green when exposed to air. Signals due to the NCMe
ligands could not be properly assigned on the 1H NMR spectra
because of overlap and fast exchange with the deuterated solvent.
Compound 2a. Yield: orange solid (0.125 g, 52%). Anal. Calcd
Imines 1a-1o: General Procedure. The corresponding alde-
hyde (2.5 mmol) was dissolved in CH2Cl2 (15 mL). MgSO4 (0.5
g) was added together with the respective amine (2.5 mmol), and
the suspension was stirred overnight at room temperature under
an argon atmosphere. Then the mixture was filtered to remove
MgSO4 and the solvent removed under reduced pressure. The
imines were recovered, and when needed, they were purified
according to the reported procedures. The spectral data of the
previously reported imines 1a-1c, 1f-1l, 1o, and 1q were
compared with the literature data to confirm their structures.14
The new imines 1d, 1e, 1n, and 1p were recystallizated from
dichloromethane (DCM)/pentane prior to use, and the imine 1m
was recovered and used without further purification. All of the
new imines employed were fully characterized by NMR spec-
troscopy, mass spectrometry, and elemental analysis.
for C19H20N5SPF6Ru MeCN: C, 39.56; H, 3.64; N, 13.18; S,
3
5.03. Found: C, 39.58; H, 3.31; N, 13.52; S, 5.43. MS (ESIþ): m/z
411.0 ([M - MeCN]þ). 31P{1H} NMR (CD3CN): δ -144.6 (hpt,
1JPF = 706.5). 19F NMR (CD3CN): δ -72.9 (d). 1H NMR
5
(CD3CN): δ 8.41 (d, 1H, NdCH, JHH = 0.40), 7.82 (d, 1H,
thiophene, 3JHH = 4.80), 7.62 (dd, 1H, thiophene, 3JHH = 4.80,
5JHH = 0.40), 7.45-7.41 (m, 2H, Ph), 7.31-7.27 (m, 3H, Ph).
13C{1H} NMR (CD3CN): δ 201.2 (s, C, C-Ru), 166.9 (s, CH,
NdC), 152.0 (s, C), 137.5 (s, C), 135.9 (s, CH, thiophene), 132.8
(s, CH, thiophene), 128.7 (s, CH, Ph), 126.0 (s, CH, Ph), 124.1 (s,
C, MeCN), 123.8 (s, C, MeCN), 122.9 (s, CH, Ph), 122.3 (s, C,
MeCN), 3.3 (s, CH3, MeCN), 3.2 (s, CH3, MeCN), 2.9 (s, CH3,
MeCN).
Imine 1d [SC4H2-2-(CHdNPh)-5-Ph]. Yield: yellow solid
(0.569 g, 86%). Anal. Calcd for C17H13NS: C, 77.53; H, 4.98;
N, 5.32; S, 12.17. Found: C, 77.73; H, 4.74; N, 5.19; S, 11.97. MS
(ESIþ): m/z 264.0 ([M þ H]þ). 1H NMR (CDCl3): δ 8.56 (s, 1H,
NdCH), 7.71 (m, 2H), 7.47-7.36 (m, 7H), 7.29-7.26 (m, 3H).
13C{1H} NMR (CDCl3): δ 152.9 (s, CH), 151.4 (s, C), 149.0

44 Inorganic Chemistry, Vol. 50, No. 1, 2011
Cuesta et al.
Compound 2b. Yield: orange solid (0.127 g, 51%). Anal. Calcd
for C20H22N5OSPF6Ru: C, 38.34; H, 3.54; N, 11.18; S, 5.12.
Found: C, 37.98; H, 3.19; N, 11.52; S, 4.73. MS (ESIþ): m/z
441.0 ([M - MeCN]þ). 31P{1H} NMR (CD3CN): δ -144.6 (spt,
1JPF = 706.5). 19F NMR (CD3CN): δ -72.9 (d). 1H NMR
(CD3CN): δ 8.37 (s, 1H, NdCH), 7.80 (d, 1H thiophene,
(s, CH3, MeCN), 3.7 (s, CH3, MeCN). Single crystals suitable
for X-ray diffraction analysis were obtained by diffusion of
Et2O into a solution of 2f in MeCN.
Compound 2g. Yield: yellow solid (0.137 g, 53%). Anal. Calcd
for C21H24N5OSPF6Ru 1.5CH2Cl2: C, 35.19; H, 3.54; N, 9.12;
3
S, 4.17. Found: C, 35.55; H, 3.44; N, 9.13; S, 3.62. MS (ESIþ): m/
z 413.9 ([M - 2MeCN]þ). 31P{1H} NMR (CD3CN): δ -144.6
(spt, 1JPF = 706.5). 19F NMR (CD3CN): δ -72.9 (d). 1H NMR
(CD3CN): δ 8.39 (s, 1H, NdCH), 7.68 (d, 1H, thiophene,
3
3JHH = 4.80), 7.61 (d, 1H, thiophene, JHH = 4.80),
7.25-7.23 (m, 2H, C6H4OMe), 6.98-6.95 (m, 2H, C6H4OMe),
3.84 (s, 3H, OMe). 13C{1H} NMR (CD3CN): δ 200.1 (s, C,
C-Ru), 166.1 (s, CH, NdC), 158.0 (s, C), 145.8 (s, C), 137.4 (s,
C), 135.9 (s, CH, thiophene), 132.3 (s, CH, thiophene), 129.8 (s,
C, MeCN), 128.0 (s, C, MeCN), 123.8 (s, CH, C6H4OMe), 122.3
(s, C, MeCN), 113.7 (s, CH, C6H4OMe), 55.2 (s, CH3, OMe), 3.3
(s, CH3, MeCN), 3.2 (s, CH3, MeCN), 2.9 (s, CH3, MeCN).
Single crystals suitable for X-ray diffraction analysis were
obtained by the slow diffusion of Et2O into a solution of 2b in
MeCN.
3
3JHH = 4.50), 7.50 (d, 1H, thiophene, JHH = 4.50),
7.26-7.23 (m, 2H, C6H4OMe), 6.94-6.91 (m, 2H, C6H4OMe),
4.92 (s, 2H, CH2-Ph), 3.77 (s, 3H, OMe). 13C{1H} NMR
(CD3CN): δ 197.0 (s, C, C-Ru), 166.7 (s, CH, NdC), 158.9
(s, C), 135.7 (s, CH, thiophene), 135.2 (s, C), 130.7 (s, CH,
thiophene), 130.4 (s, C), 129.8 (s, CH, C6H4OMe), 123.7 (s, C,
MeCN), 123.2 (s, C, MeCN), 121.5 (s, C, MeCN), 113.5 (s, CH,
C6H4OMe), 63.9 (s, CH2, CH2-Ph), 54.9 (s, CH3, OMe), 3.3 (s,
CH3, MeCN), 3.2 (s, CH3, MeCN), 2.9 (s, CH3, MeCN).
Compound 2h. Yield: yellow solid (0.103 g, 42%). Anal. Calcd
Compound 2c. Yield: red solid (0.139 g, 57%). Anal. Calcd for
C20H22N5SPF6Ru: C, 39.35; H, 3.63; N, 11.47; S, 5.25. Found:
C, 39.42; H, 3.67; N, 11.87; S, 5.19. MS (ESIþ): m/z 425.0 ([M -
for C18H20N5S2PF6Ru 0.5MeCN: C, 35.82; H, 3.40; N, 12.09;
3
1
MeCN]þ. 31P{1H} NMR (CD3CN): δ -144.6 (spt, JPF
=
S, 10.06. Found: C, 35.57; H, 3.36; N, 11.76; S, 10.79. MS
(ESIþ): m/z 430.9 ([M - MeCN]þ). 31P{1H} NMR (CD3CN):
δ -144.6 (spt, 1JPF = 706.5). 19F NMR (CD3CN): δ -72.9 (d).
1H NMR (CD3CN): δ 8.42 (s, 1H, NdCH), 7.70 (d, 1H,
thiophene-cyclometalated, 3JHH = 4.70), 7.49 (d, 1H, thiophene-
706.5). 19F NMR (CD3CN): δ -72.9 (d). 1H NMR (CD3CN):
δ 8.24 (s, 1H, NdCH), 7.43-7.38 (m, 2H, Ph), 7.32 (s, 1H,
thiophene), 7.30-7.25 (m, 3H, Ph). 13C{1H} NMR (CD3CN): δ
204.9 (s, C, C-Ru), 165.9 (s, CH, NdC), 152.5 (s, C), 149.3 (s,
C), 136.4 (s, C), 135.6 (s, CH, thiophene), 128.7 (s, CH, Ph),
125.8 (s, CH, Ph), 123.9 (s, C, MeCN), 123.0 (s, C, MeCN), 122.4
(s, CH, Ph), 120.1 (s, C, MeCN), 15.0 (s, CH3, Me-thiophene),
3.3 (s, CH3, MeCN), 3.2 (s, CH3, MeCN), 2.9 (s, CH3, MeCN).
Compound 2d. Yield: dark-red solid (0.141 g, 52%). Anal.
3
cyclometalated, JHH = 4.70), 7.31 (dd, 1H, H5 thiophene,
3
4JHH = 1.20, JHH = 5.10), 7.08 (m, 1H, H3 thiophene), 7.00
(dd, 1H, H4 thiophene, 3JHH = 5.10 and 3.60), 5.12 (s, 2H, CH2).
13C{1H} NMR (CD3CN): δ 197.9 (s, C, C-Ru), 167.0 (s, CH,
NdC), 141.5 (s, C), 135.8 (s, CH), 135.5 (s, C), 131.3 (s, CH),
127.2 (s, CH), 127.0 (s, CH), 125.4 (s, CH), 124.7 (s, C, MeCN),
123.7 (s, C, MeCN), 121.9 (s, C, MeCN), 58.2 (s, CH2, CH2
thiophene), 3.5 (s, CH3, MeCN), 3.4 (s, CH3, MeCN), 2.9 (s,
CH3, MeCN).
Calcd for C25H24N5SPF6Ru 0.5MeCN: C, 45.06; H, 3.71; N,
3
11.11; S, 4.63. Found: C, 45.68; H, 3.25; N, 10.82; S, 5.02. MS
(ESIþ): m/z 487.0 ([M - MeCN]þ). 31P{1H} NMR (CD3CN): δ
-144.6 (spt, 1JPF = 706.5). 19F NMR (CD3CN): δ -72.9 (d). 1H
NMR (CD3CN): δ 8.40 (s, 1H, NdCH), 7.98 (s, 1H, thiophene),
7.87-7.84 (m, 2H, Ph), 7.50-7.48 (m, 4H, Ph), 7.46-7.31 (m,
4H, Ph). 13C{1H} NMR (CD3CN): δ 203.8 (s, C, C-Ru), 166.4
(s, CH, NdC), 152.4 (s, C), 151.7 (s, C), 138.2 (s, C), 134.6 (s, C),
132.9 (s, CH, thiophene), 129.1 (s, CH, Ph), 128.7 (s, CH, Ph),
128.2 (s, CH, Ph), 126.2 (s, CH, Ph), 126.0 (s, CH, Ph), 124.3 (s,
C, MeCN), 123.8 (s, C, MeCN), 122.9 (s, CH, Ph), 122.5 (s, C,
MeCN), 3.5 (s, CH3, MeCN), 3.2 (s, CH3, MeCN), 2.9 (s, CH3,
MeCN).
Compound 2i. Yield: orange solid (0.112 g, 45%). Anal. Calcd
for C20H22N5SPF6Ru: C, 39.35; H, 3.63; N, 11.47; S, 5.25.
Found: C, 39.21; H, 3.15; N, 11.78; S, 5.71. MS (ESIþ): m/z
426.0 ([M - MeCN]þ). 31P{1H} NMR (CD3CN): δ -144.6 (spt,
1JPF = 706.5). 19F NMR (CD3CN): δ -72.9 (d). 1H NMR
(CD3CN): δ 8.41 (s, 1H, NdCH), 7.84-7.81 (m, 1H,
4
3
thiophene), 7.46 (dd, 1H, C6H4, JHH = 1.20, JHH = 7.50),
7.29 (dd, 1H, C6H4, 4JHH = 1.20, 3JHH = 5.10), 7.05 (m, 1H,
thiophene), 6.81 (m, 2H, 1H C6H4 þ 1H thiophene), 6.75 (m,
1H, C6H4), 5.10 (s, 2H, CH2). 13C{1H} NMR (CD3CN): δ 189.7
(s, C, C-Ru), 175.4 (s, CH, NdC), 148.2 (s, C), 139.8 (s, C),
137.3 (s, CH), 127.9 (s, CH), 127.4 (s, CH), 126.8 (s, CH),
126.4 (s, CH), 125.0 (s, CH), 123.3 (s, C, MeCN), 123.2 (s, C,
MeCN), 120.2 (s, C, MeCN), 119.8 (s, CH), 58.2 (s, CH2, CH2
thiophene), 2.8 (s, CH3, MeCN), 2.7 (s, CH3, MeCN), 2.2 (s,
CH3, MeCN).
Compound 2e. Yield: yellow solid (0.127 g, 49%). Anal. Calcd
for C23H22N5SPF6Ru CH2Cl2: C, 39.41; H, 3.31; N, 9.57; S,
3
4.38. Found: C, 39.75; H, 3.59; N, 9.81; S, 4.24. MS (ESIþ): m/z
460.8 ([M - MeCN]þ). 31P{1H} NMR (CD3CN): δ -144.6 (spt,
1JPF = 706.5). 19F NMR (CD3CN): δ -72.9 (d). 1H NMR
(CD3CN): δ 8.58 (s, 1H, NdCH), 8.53-8.50 (m, 1H, C6H4),
8.03-8.00 (m, 1H, C6H4), 7.53-7.48 (m, 4H, 3 Ph þ 1 C6H4),
7.42-7.36 (m, 3H, 2 Ph þ 1 C6H4). 13C{1H} NMR (CD3CN): δ
199.6 (s, C, C-Ru), 168.3 (s, CH, NdC), 152.3 (s, C), 149.7 (s,
C), 145.4 (s, C), 135.5 (s, C), 128.8 (s, CH), 128.7(s, CH), 126.4 (s,
CH), 126.3 (s, CH), 124.0 (s, CH), 123.9 (s, C, MeCN), 123.8 (s,
C, MeCN), 123.0 (s, CH), 123.1 (s, CH), 122.6 (s, C, MeCN), 3.3
(s, CH3, MeCN), 3.2 (s, CH3, MeCN), 2.9 (s, CH3, MeCN).
Compound 2f. Yield: yellow solid (0.141 g, 58%). Anal. Calcd
for C20H22N5SPF6Ru: C, 39.35; H, 3.63; N, 11.47; S, 5.25.
Found: C, 38.73; H, 3.91; N, 12.09; S, 5.57. MS (ESIþ): m/z
425.0 ([M - MeCN]þ). 31P{1H} NMR (CD3CN): δ -144.6 (spt,
1JPF = 706.5). 19F NMR (CD3CN): δ -72.9 (d). 1H NMR
(CD3CN): δ 8.43 (s, 1H, NdCH), 7.69 (d, 1H, thiophene,
Compound 2j. Yield: orange solid (0.119 g, 46%). Anal. Calcd
for C21H24N5OSPF6Ru: C, 39.38; H, 3.78; N, 10.93; S, 5.01.
Found: C, 39.99; H, 3.82; N, 11.28; S, 5.43. MS (ESIþ): m/z
455.0 ([M - MeCN]þ. 31P{1H} NMR (CD3CN): δ -144.6 (spt,
1JPF = 706.5). 19F NMR (CD3CN): δ -72.9 (d). 1H NMR
3
(CD3CN): δ 8.30 (s, 1H, NdCH), 7.40 (d, 1H, C6H3, JHH
=
8.10), 7.33 (d, 1H, C6H3, 4JHH = 2.40), 7.27 (m, 1H, thiophene),
7.03 (m, 1H, thiophene), 6.96 (m, 1H, thiophene), 6.41 (dd, 1H,
C6H3, 4JHH = 2.40, 3JHH = 8.10), 5.04 (s, 2H, CH2), 3.78 (s, 3H,
OMe). 13C{1H} NMR (CD3CN): δ 193.1 (s, C, C-Ru), 174.5 (s,
CH, NdC), 159.3 (s, C), 141.8 (s, C), 140.9 (s, C), 129.8 (s, CH),
127.1 (s, CH), 126.9 (s, CH), 125.4 (s, CH), 123.9 (s, C, MeCN),
123.0 (s, C, MeCN), 122.4 (s, CH), 121.2 (s, C, MeCN), 106.4 (s,
CH), 58.4 (s, CH2, CH2 thiophene), 54.5 (s, CH3, OMe), 3.4 (s,
CH3, MeCN), 3.3 (s, CH3, MeCN), 2.9 (s, CH3, MeCN). Single
crystals suitable for X-ray diffraction analysis were obtained by
the slow diffusion of Et2O into a solution of 2j in MeCN.
Compound 2k. Yield: orange solid (0.132 g, 55%). Anal.
3
3JHH = 4.80), 7.51 (d, 1H, thiophene, JHH = 4.80),
7.38-7.31 (m, 5H, Ph), 4.99 (s, 2H, CH2-Ph). 13C{1H} NMR
(CD3CN): δ 198.3 (s, C, C-Ru), 168.1 (s, CH, NdC), 139.5 (s,
C), 136.6 (s, CH, thiophene), 136.4 (s, C), 131.81 (s, CH,
thiophene), 129.3 (s, CH, Ph), 129.0 (s, CH, Ph), 128.1 (s, CH,
Ph), 124.7 (s, C, MeCN), 124.2 (s, C, MeCN), 122.5 (s, C,
MeCN), 65.5 (s, CH2, CH2-Ph), 4.2 (s, CH3, MeCN), 4.1
Calcd for C19H20N5SPF6Ru CH2Cl2: C, 35.25; H, 3.25; N,
3

Article
Inorganic Chemistry, Vol. 50, No. 1, 2011 45
10.28; S, 4.70. Found: C, 34.68; H, 3.17; N, 10.40; S, 4.43. MS
(ESIþ): m/z 452.0 ([M]þ). 31P{1H} NMR (CD3CN): δ -144.6
(spt, 1JPF = 706.5). 19F NMR (CD3CN): δ -72.9 (d). 1H NMR
(CD3CN): δ 8.19 (s, 1H, NdCH), 7.46-7.23 (m, 7H). 13C{1H}
NMR (CD3CN): δ 207.7 (s, C, C-Ru), 169.1 (s, CH, NdC),
153.2 (s, C), 148.3 (s, C), 129.7 (s, CH), 129.2 (s, CH), 126.8 (s,
CH), 125.1 (s, C, MeCN), 124.8 (s, C, MeCN), 124.7 (s, CH),
123.7 (s, CH), 123.6 (s, C, MeCN), 3.3 (s, CH3, MeCN), 3.1
(s, CH3, MeCN), 3.0 (s, CH3, MeCN).
Iodinations: General Procedure. Iodine (152 mg, 0.6 mmol)
was added to a solution of the respective complex (0.2 mmol) in
undried MeCN (15 mL). The mixture was stirred at room
temperature under argon for 48 h, and the solvent was removed.
The dark residue was extracted with Et2O (3 ꢀ 15 mL), and the
solution was washed with saturated aqueous Na2S2O3 (2 ꢀ 10
mL). The organic phases were collected and dried over MgSO4.
After filtration, the solvent was evaporated in vacuo and the
iodinated thiophene was recovered. The derivatives 3a, 3k, and
1
3n were identified by comparison with the reported H NMR
Compound 2l. Yield: orange solid (0.147 g, 60%). Anal. Calcd
for C20H22N5SPF6Ru: C, 39.35; H, 3.63; N, 11.47; S, 5.25.
Found: C, 39.03; H, 3.62; N, 11.79; S, 5.06. MS (ESIþ): m/z
425.0 ([M - MeCN]þ). 31P{1H} NMR (CD3CN): δ -144.6 (spt,
1JPF = 706.5). 19F NMR (CD3CN): δ -72.9 (d). 1H NMR
(CD3CN): δ 8.32 (s, 1H, NdCH), 7.40-7.38 (m, 3H, 1H
thiophene þ 2H Ph), 7.35-7.28 (m, 3H, Ph), 7.11 (d, 1H,
spectra.23
Aldehyde 3c [SC4H-2-(CHO)-3-I-5-Me]. Yield: yellow solid
(0.035 g, 69%). Anal. Calcd for C6H5IOS: C, 28.59; H, 2.00; S,
12.72. Found: C, 28.13; H, 1.66; S, 12.39. MS (ESIþ): m/z 252.
1H NMR (CDCl3): δ 9.69 (s, 1H, CHO), 6.97 (q, 1H, thiophene,
4
4JHH = 0.90), 2.56 (d, 3H, Me, JHH = 0.90). 13C{1H} NMR
3
thiophene, JHH = 5.10), 4.96 (s, 2H, CH2). 13C{1H} NMR
(CDCl3): δ 185.1 (s, CH, CHO), 152.1 (s, C), 137.1 (s, C), 135.8
(s, CH, thiophene), 96.8 (s, C, C-I), 15.63 (s, C, Me).
(CD3CN): δ 201.1 (s, C, C-Ru), 168.9 (s, CH, NdC), 146.2 (s,
C), 138.6 (s, C), 128.3 (s, CH, Ph), 128.1 (s, CH, Ph), 127.2 (s,
CH, Ph), 125.0 (s, CH, thiophene), 124.8 (s, CH, thiophene),
123.8 (s, C, MeCN), 123.2 (s, C, MeCN), 121.9 (s, C, MeCN),
64.5 (s, CH2, CH2-Ph), 3.3 (s, CH3, MeCN), 3.0 (s, CH3,
MeCN), 2.8 (s, CH3, MeCN).
Aldehyde 3d [SC4H-2-(CHO)-3-I-5-Ph]. Yield: yellow solid
(0.039 g, 62%). Anal. Calcd for C11H7IOS: C, 42.06; H, 2.25; S,
10.21. Found: C, 41.73; H, 2.01; S, 9.79. MS (ESIþ): m/z 314. 1H
NMR (CDCl3): δ 9.76 (s, 1H, CHO), 7.68-7.64 (m, 2H, Ph),
7.49 (s, 1H, thiophene), 7.47-7.45 (m, 3H, Ph). 13C{1H} NMR
(CDCl3): δ 185.4 (s, CH, CHO), 154.5 (s, C), 144.9 (s, C), 137.8
(s, C), 137.8 (s, CH, thiophene), 132.8 (s, CH, Ph), 129.4 (s, CH,
Ph), 126.4 (s, CH, Ph), 105.0 (s, C, C-I).
Compound 2m. Yield: yellow solid (0.118 g, 48%). Anal.
Calcd for C18H20N5S2PF6Ru 0.5MeCN: C, 35.82; H, 3.40; N,
3
12.09; S, 10.06. Found: C, 36.13; H, 3.78; N, 11.82; S, 9.75. MS
(ESIþ): m/z 430.9 ([M - MeCN]þ). 31P{1H} NMR (CD3CN): δ
-144.6 (spt, 1JPF = 706.5). 19F NMR (CD3CN): δ -72.9 (d). 1H
NMR (CD3CN): δ 8.34 (s, 1H, NdCH), 7.40 (d, 1H, H4 thio-
Aldehyde 3e [SC8H4-2-(CHO)-3-I]. Yield: yellow solid (0.037
g, 64%). Anal. Calcd for C9H5IOS: C, 37.52; H, 1.75; S, 11.13.
1
Found: C, 37.09; H, 1.41; S, 10.76. MS (ESIþ): m/z 288. H
3
phene-cyclometalated, JHH = 3.80), 7.35 (dd, 1H, H5 thio-
NMR (CDCl3): δ 10.15 (s, 1H, CHO), 8.14-7.99 (m, 1H, C6H4),
7.87-7.76 (m, 1H, C6H4), 7.55-7.51 (m, 2H, C6H4). 13C{1H}
NMR (CDCl3): δ 187.3 (s, CH, CHO), 145.4. (s, C), 140.9 (s, C),
139.7 (s, C), 129.2 (s, CH, C6H4), 127.3 (s, CH, C6H4), 126.1
(s, CH, C6H4), 123.3 (s, CH, C6H4), 102.1 (s, C, C-I).
phene, 3JHH = 3.90, 4JHH = 0.90), 7.12 (d, 1H, H5 thiophene-
cyclometalated, 3JHH =3.80), 7.10(dd, 1H, H3 thiophene, 3JHH
=
2.70, 4JHH = 0.90), 7.05 (dd, 1H, H4 thiophene, 3JHH = 3.90,
3JHH = 2.70), 5.12 (s, 2H, CH2). 13C{1H} NMR (CD3CN): δ
201.7 (s, C, C-Ru), 168.0 (s, CH, NdC), 146.2 (s, C), 141.6 (s,
C), 126.9 (s, CH), 126.8 (s, CH), 125.3 (s, CH), 125.1 (s, CH),
124.9 (s, CH), 124.4 (s, C, MeCN), 123.8 (s, C, MeCN), 123.4 (s,
C, MeCN), 58.2 (s, CH2, CH2 thiophene), 3.3 (s, CH3, MeCN),
3.2 (s, CH3, MeCN), 2.8 (s, CH3, MeCN).
X-ray Crystallography. X-ray data collections were performed
on an Oxford Diffraction Xcalibur2 diffractometer using gra-
phite-monochromated Mo KR radiation (λ = 0.710 73 A). A
single crystal was mounted at the end of a quartz fiber in a
random orientation, covered with perfluorinated oil, and placed
under a cold stream of dinitrogen gas. In all cases, a hemisphere
of data was collected based on ω- or φ-scan runs. The diffraction
frames were integrated using the program or CrysAlis RED,25
and the integrated intensities were corrected for absorption with
SADABS.26 The structures were solved and developed by
Patterson and Fourier methods.27 All non-H atoms were refined
with anisotropic displacement parameters. The H atoms were
placed at idealized positions and treated as riding atoms. Each H
atom was assigned an isotropic displacement parameter equal to
1.2 times the equivalent isotropic displacement parameter of its
parent atom. The structures were refined to Fo2, and all reflec-
tions were used in the least-squares calculations.28
Compound 2n. Yield: yellow solid (0.128 g, 50%). Anal. Calcd
for C23H22N5SPF6Ru: C, 42.73; H, 3.43; N, 10.83; S, 4.96.
Found: C, 42.95; H, 3.88; N, 10.41; S, 4.74. MS (ESIþ): m/z
461.0 ([M - MeCN]þ). 31P{1H} NMR (CD3CN): δ -144.6 (spt,
1JPF = 706.5). 19F NMR (CD3CN): δ -72.9 (d). 1H NMR
(CD3CN): δ 8.61 (s, 1H, NdCH), 7.88-7.81 (m, 2H, C6H4),
7.48-7.43 (m, 2H, Ph), 7.35-7.26 (m, 4H, 3H Ph þ 1H C6H4),
7.13 (m, 1H, C6H4). 13C{1H} NMR (CD3CN): δ 218.7 (s, C,
C-Ru), 167.3 (s, CH, NdC), 153.3 (s, C), 144.8 (s, C), 143.0 (s,
C), 139.6 (s, C), 129.7 (s, CH, Ph), 126.9 (s, CH, Ph), 125.2 (s, C,
MeCN), 125.1 (s, CH, C6H4), 124.7 (s, C, MeCN), 124.1 (s, CH,
Ph), 123.9 (s, C, MeCN), 122.3 (s, CH, C6H4), 121.8 (s, CH,
C6H4), 118.7 (s, CH, C6H4), 3.4 (s, CH3, MeCN), 3.2 (s, CH3,
MeCN), 2.9 (s, CH3, MeCN).
Acknowledgment. Funding by the Ministerio de Ciencia e
ꢀ
Innovacion (Spain; Project CTQ2008-01784) and Gobierno de
Compound 2o. Yield: dark-red solid (0.137 g, 49%). Anal.
Calcd for C26H25N6SPF6Ru MeCN: C, 45.41; H, 3.81; N,
ꢀ
Aragon (Spain; Project PI071/09) is gratefully acknowledged.
L.C. thanks Consejo Superior de Investigaciones Cientıficas
(Spain) for a Juan de la Cierva contract.
3
´
13.24; S, 4.33. Found: C, 45.13; H, 3.46; N, 13.69; S, 4.69. MS
(ESIþ): m/z 514.0 ([M - MeCN]þ). 31P{1H} NMR (CD3CN): δ
-144.6 (spt, 1JPF = 706.5). 19F NMR (CD3CN): δ -72.9 (d). 1H
NMR (CD3CN): δ 8.89 (s, 1H, NdCH), 8.50 (s, 1H, RuNd
CH), 8.12 (s, 1H, thiophene), 7.51-7.44 (m, 4H, Ph), 7.39-7.29
(m, 6H, Ph). 13C{1H} NMR (CD3CN): δ 200.1 (s, C, C-Ru),
167.4 (s, CH, RuNdC), 154.2 (s, CH, NdC), 152.2 (s, C), 151.5
(s, C), 149.2 (s, C), 142.9 (s, C), 142.5 (s, CH, thiophene), 129.3
(s, CH, Ph), 128.8 (s, CH, Ph), 126.5 (s, CH, Ph), 126.2 (s, CH,
Ph), 124.8 (s, C, MeCN), 124.5 (s, C, MeCN), 122.8 (s, CH, Ph),
122.6 (s, C, MeCN), 121.1 (s, CH, Ph), 3.6 (s, CH3, MeCN), 3.2
(s, CH3, MeCN), 2.9 (s, CH3, MeCN).
Supporting Information Available: CIF of complexes 2b and
2f. This material is available free of charge via the Internet at
http://pubs.acs.org.
(25) CrysAlis RED, version 1.171.27p8; Oxford Diffraction Ltd.: Oxford,
U.K., 2005.
(26) Sheldrick, G. M. SADABS: Empirical absorption correction program;
€
€
Gottingen University: Gottingen, Germany, 1996.
(27) SHELXS-86: Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467.
(28) SHELXL-97: Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112.