Synthesis, characterization, and in vitro evaluation of novel ruthenium(II) η6-arene imidazole complexes

Article abstract of DOI:10.1021/jm060495o

Ten complexes of general formula [Ru(η⁶-arene)Cl ₂(L)], [Ru(η⁶-arene)Cl(L)₂][X], and [Ru(η⁶-arene)(L)₃][X]₂ (η⁶- arene = benzene, p-cymene; L = imidazole, benzimidazole, N-methylimidazole, N-butylimidazole, N-vinylimidazole, N-benzoylimidazole; X = Cl, BF₄, BPh₄) have been prepared and characterized by spectroscopy. The structures of five representative compounds have been established in the solid state by single-crystal X-ray diffraction. All the new compounds were assessed by the same in vitro screening assays applied to [imidazole-H][trans-RuCl ₄(DMSO)(imidazole)] (NAMI-A) and [Ru(η⁶-arene)Cl ₂(1,3,5-triaza-7-phosphaadamantane)] (RAPTA) compounds. It was found that the new compounds show essentially the same order of cytotoxicity as the RAPTA compounds toward cancer cells. Several of the compounds were selective toward cancer cells in that they were less (or not) cytotoxic toward nontumorigenic cells that are used to model healthy human cells. Thus, two of the compounds, [Ru(η⁶-p-cymene)Cl(vinylimid)₂][Cl] (vinylimid = N-vinylimidazole) and [Ru(η⁶-benzene)(mimid) ₃][BF₄]₂ (mimid = N-methylimidazole), have been selected for a more detailed in vivo evaluation.

Full text of DOI:10.1021/jm060495o

5552
J. Med. Chem. 2006, 49, 5552-5561
Synthesis, Characterization, and in Vitro Evaluation of Novel Ruthenium(II) η6-Arene
Imidazole Complexes
Carsten A. Vock,† Claudine Scolaro,† Andrew D. Phillips,† Rosario Scopelliti,† Gianni Sava,‡,§ and Paul J. Dyson*,†
Institut des Sciences et Inge´nierie Chimiques, Ecole Polytechnique Fe´de´rale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland, Callerio
Foundation Onlus, Via A. Fleming 22-31, 34127, Trieste, Italy, and Dipartimento di Scienze Biomediche, UniVersita` di Trieste, Via L.
Giorgieri 7, 34127, Trieste, Italy
ReceiVed April 27, 2006
Ten complexes of general formula [Ru(η6-arene)Cl2(L)], [Ru(η6-arene)Cl(L)2][X], and [Ru(η6-arene)(L)3]-
[X]2 (η6-arene ) benzene, p-cymene; L ) imidazole, benzimidazole, N-methylimidazole, N-butylimidazole,
N-vinylimidazole, N-benzoylimidazole; X ) Cl, BF4, BPh4) have been prepared and characterized by
spectroscopy. The structures of five representative compounds have been established in the solid state by
single-crystal X-ray diffraction. All the new compounds were assessed by the same in vitro screening assays
applied to [imidazole-H][trans-RuCl4(DMSO)(imidazole)] (NAMI-A) and [Ru(η6-arene)Cl2(1,3,5-triaza-7-
phosphaadamantane)] (RAPTA) compounds. It was found that the new compounds show essentially the
same order of cytotoxicity as the RAPTA compounds toward cancer cells. Several of the compounds were
selective toward cancer cells in that they were less (or not) cytotoxic toward nontumorigenic cells that are
used to model healthy human cells. Thus, two of the compounds, [Ru(η6-p-cymene)Cl(vinylimid)2][Cl]
(vinylimid ) N-vinylimidazole) and [Ru(η6-benzene)(mimid)3][BF4]2 (mimid ) N-methylimidazole), have
been selected for a more detailed in vivo evaluation.
Introduction
and invasion of tumor cells10,11 because of f-actin condensation
and reduction of gelatinolytic capacity.12-14 The uniqueness of
the antimetastatic effects of 2 also emerges from a comparison
with other ruthenium complexes, in some cases structurally very
similar to 2, such as the imidazolium trans-bisimidazoletetra-
chlororuthenate (structurally related to 3), which was found to
be active against colorectal tumors.15 This compound, although
showing some pharmacological behaviors similar to those of
2, is free of antimetastatic activity, and also the effects on
invasion and adhesion are much less pronounced than those of
2.11 Compound 3 has also successfully completed phase I
clinical trials.16
More recently, increasing interest has focused on organome-
tallic compounds,17-19 specifically on ruthenium(II) arene
compounds which show remarkable cytotoxic properties in vitro
as well as in vivo. The first complex of this kind that was
evaluated for cytotoxic properties was [Ru(η6-benzene)Cl2-
(metronidazole)] 4 (metronidazole ) 1-â-hydroxyethyl-2-meth-
yl-5-nitroimidazole) (Figure 1). Although the complex showed
higher cytotoxic activity than the anticancer drug metronidazole
itself,20 further studies were not forthcoming. A series of
compounds with the general formula [Ru(η6-arene)Cl(en)][PF6]
(en ) ethylenediamine; arene ) benzene, p-cymene, tetrahy-
droanthracene, etc.) have been studied for their in vitro
anticancer activity; e.g., one of the most active complexes, [Ru-
(η6-p-cymene)Cl(en)][PF6] 5 (Figure 1), exhibits an IC50 value
of 8 µM against the A2780 human ovarian cancer cell line.21
In the same paper [Ru(η6-p-cymene)Cl2(isonicotinamide)] was
described but found to be much less active than the ethylene-
diamine complexes.
The discovery of the anticancer properties of cisplatin in
19651,2 heralded the development of metallopharmaceuticals and
founded a revolution in cancer therapy. Platinum drugs are
believed to induce cytotoxicity by cross-linking DNA, causing
changes to the DNA structure that inhibit replication and protein
synthesis. However, the application of platinum drugs suffers
from their high general toxicity, leading to severe side effects.
In comparison, ruthenium-based anticancer drugs exhibit a
low general toxicity and specifically accumulate in cancer cells.3
This is possibly due to the ability of ruthenium to mimic iron
in binding to certain biomolecules, including serum transferrin
and albumin, which are known to be responsible for solubili-
zation, transport, and detoxification of iron in mammals.3
Rapidly growing cancer cells have a greater requirement for
iron, which leads to an overexpression of transferrin receptors
on their surfaces such that ruthenium compounds accumulate
in cancer cells.3
The most prominent examples of ruthenium anticancer drugs
developed so far are the Ru(III) complexes Na[trans-RuCl4-
(DMSO)(imida)], NAMI 1, its more stable imidazolium ana-
logue [imidH][trans-RuCl4(DMSO)(imid)], NAMI-A 2, and the
indazole compound [indH][trans-RuCl4(ind)2], KP1019 3 (Fig-
ure 1). Compound 2 shows high selectivity for solid tumor
metastases4,5 and low toxicity at pharmacologically active
doses6-8 and has successfully completed phase I clinical trials.9
Metastasis control is associated with a series of biological
activities that influence cell functions such as adhesion, motility,
* To whom correspondence should be addressed. Phone: +41 (0)21 693
98 54. Fax: +41 (0)21 693 98 85. E-mail: paul.dyson@epfl.ch.
† Ecole Polytechnique Fe´de´rale de Lausanne (EPFL).
‡ Callerio Foundation Onlus.
Our research has focused on compounds of general formula
[Ru(η6-arene)Cl2(pta)] (pta ) 1,3,5-triaza-7-phosphaadaman-
tane) (RAPTA), the prototype being [Ru(η6-p-cymene)Cl2(pta)]
6 (RAPTA-C) (Figure 1).3,22 In vitro it exhibits pH-dependent
DNA-damaging properties such that at pH < 7, which can be
found in the tumor mass of poorly oxygenated cancer cells,
DNA is damaged, whereas normal cells with pH > 7 are not
§ Universita` di Trieste.
a Abbreviations: en, ethylenediamine; ind, indazole; pta, 1,3,5-triaza-
7-phosphaadamantane; imid, imidazole; mimid, N-methylimidazole; ben-
zimid, benzimidazole; bimid, N-butylimidazole; vinylimid, N-vinylimida-
zole; benzoylimid, N-benzoylimidazole; [9]aneS3, 1,4,7-trithiacyclononane;
EE, ethyl acetate.
10.1021/jm060495o CCC: $33.50 © 2006 American Chemical Society
Published on Web 08/09/2006

Ruthenium(II) η6-Areneimidazole Complexes
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 18 5553
Figure 1. Structures of NAMI 1, NAMI-A 2, KP1019 3, [Ru(η6-benzene)Cl2(metronidazole)] 4, [Ru(η6-p-cymene)Cl(en)][PF6] 5, RAPTA-C 6,
and [RuCl(pta)2([9]aneS3)][OTf] 7.
Figure 2. General structure of compounds 8-10.
affected. Indeed, this selectivity was observed in comparative
cell tests of several structural diversified RAPTA derivatives
with TS/A adenocarcinoma cancer cells and nontumorigenic
(healthy) HBL-100 mammary cells.23 In vivo, 6 reduced
significantly the growth of lung metastases in CBA mice bearing
the MCa mammary carcinoma. Mass spectroscopic investiga-
tions revealed the lability of the arene moiety in RAPTA
complexes during binding experiments with an oligonucleotide
in cell-free medium.24,25 Recent results indicate that the η6-
coordinated arene moiety in RAPTA-type compounds can be
substituted by chelating ligands with three coordination sites
such as 1,4,7-trithiacyclononane ([9]aneS3), and in comparative
cell studies, the complex [RuCl(pta)2([9]aneS3)][OTf] 7 (Figure
1) showed similar cytotoxicity and selectivity as 6.26
In an attempt to synergistically combine the classes of
substances, i.e., the Ru(II) piano-stool complexes such as 6, with
the imidazole ligand characteristic of NAMI-type ruthenium(III)
complex, to obtain new potent anticancer drugs, in this study
we describe the synthesis, crystallographic analysis, and pre-
liminary in vitro biological evaluation of three new classes of
Ru(II)-η6-areneimidazole complexes 8-10 (Figure 2). Com-
plexes of type [Ru(η6-arene)Cl2(ligand)] 8, with one imidazole
ligand, have already been reported,27,28 including the monoim-
idazole derivative [Ru(η6-C6Me6)Cl2(imidazole)].27 However,
to the best of our knowledge, none of the existing examples
have been evaluated for their anticancer properties. As far as
we are aware, the bis-imidazole complexes of type [Ru(η6-
arene)Cl(ligand)2][X] 9 and the tris-imidazole complexes of type
[Ru(η6-arene)(ligand)3][X]2 10 are unprecidented, and a com-
parison of the in vitro activity of 8-10 should provide useful
information for further biological evaluation and future drug
design strategies.
Results and Discussion
The monoimidazole type complexes 8, the pyridine analogue
11, and the morpholine derivative 12 were prepared according
to a protocol described by Bennett and Smith.29 Treatment of
[Ru(η6-p-cymene)Cl2]2 with the corresponding stoichiometric
amount, or a slight excess, of the amine in toluene under reflux
for 2-3 h led to the complexes in reasonable to good yields
(Figure 3). The desired compounds precipitated directly from
the reaction mixture and were isolated by filtration. For the more
labile ligand N-benzoylimidazole (benzoylimid), which was
synthesized by a literature protocol,30 the conversion was carried
out in CH2Cl2 at room temperature.
In contrast to the other reactions, reaction with N-butylimi-
dazole (bimid) did not lead to the formation of a precipitate.
Therefore, an excess of petroleum ether was added, and the
mixture was stored at 4 °C. After 6 weeks, large red crystals
formed, which were identified by X-ray analysis as the ionic
species [Ru(η6-p-cymene)Cl(bimid)2][Ru(η6-p-cymene)Cl3] 13
(Figure 3; also see the crystallographic section). To our

5554 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 18
Vock et al.
Figure 3. Structures of 8a-c and 11-13.
Figure 4. Structures of 9a-e.
knowledge, the anion [Ru(η6-p-cymene)Cl3]- has only been
reported once before31 and a related trichlororuthenate(II) anion
has also been prepared with different η6-arene ligands,32,33 but
in each case synthesis was carried out in the presence of
hydrochloric acid. In contrast, the formation of the ionic
compound 13 proceeded under nonacidic conditions in a
nonpolar solvent.
The synthesis of the bis-imidazole compounds, 9, was
generally performed by heating a mixture of the ruthenium
precursor and 4 equiv of the appropiate ligand in a high-boiling
alcoholic solvent such as iPrOH or nBuOH for 4-8 h (Figure
4), with the exception of [Ru(η6-p-cymene)Cl(imid)2][BPh4] 9e
that was prepared in acetone in the presence of a slight excess
of NaBPh4. Use of an excess ligand led to slightly higher yields
without the formation of higher substituted compounds, i.e., of
type 10. With the exception of 9a the obtained yields were only
moderate. Attempts to crystallize 9c,d failed, and the solvent-
wet compounds liquidified quickly with an accompanying color
change to dark-brown when exposed to air, which might be
due to their high hygroscopicity. However, thoroughly dried,
the substances can be handled without problems. In general,
the high hygroscopicity of the chloride salts 9a-d is correlated
with very high water solubility, which makes them ideal for
physiological applications in terms of administration.
Compounds 10 (Figure 5) were prepared by treatment of the
corresponding ruthenium(II) precursor with a slight excess of
N-methylimidazole and AgBF4 in CH2Cl2 or CHCl3 under
ambient conditions, leading to compounds 10a and 10b in
modest yield. The substances exhibited good to very good water
solubility.
The ESI mass spectra of 8-10 in methanol or CH3CN provide
parent peaks corresponding to the cations for 9 and 10, and in
the case of 8 loss of one chloride ligand takes place to generate
a cation. For compounds 8 and 9, varying degrees of solvated
species are also observed; nonetheless, all spectra confirm the
presence of the expected products.
The assignment of the imidazole 1H and 13C NMR signals in
the series of homologous complexes [Ru(η6-p-cymene)Cl2-

Ruthenium(II) η6-Areneimidazole Complexes
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 18 5555
Figure 5. Structures of complexes 10a,b.
Table 1. Selected Bond Lengths (in Å) and Angles (deg) for Complexes 9a, 9b, 9e, 10b, and 13
9a
9b
13 (cation)
(Ar ) p-cymene;
R ) nBu)
9e
10b
(Ar ) p-cymene;
(Ar ) p-cymene;
(Ar ) benzene;
(Ar ) benzene;
parameter
Ru-N(imid(R))
R ) Me)
R ) nBu)
R ) H)
R ) Me)
2.121(3)
2.131(3)
2.122(2)
2.123(2)
2.110(5)
2.131(5)
2.114(3)
2.122(3)
2.107(2)
2.108(2)
2.110(2)
Ru-Cl
2.432(5)
1.684
83.02(6)
2.422(1)
1.668
84.56(12)
2.415(2)
1.669
85.87(18)
2.407(1)
1.671
85.00(13)
Ru-Arcentriod
1.678
N(imid(R))-Ru-N(imid(R))
82.07(6)
85.53(6)
90.37(6)
Cl-Ru-N(imid(R))
86.61(5)
87.44(5)
128.88
87.47(9)
88.19(10)
127.67
87.57(13)
87.77(13)
127.12
86.44(9)
85.61(9)
128.88
Arcentriod-Ru-N(imid(R))
125.41
127.71
131.15
129.98
128.41
128.43
129.23
Arcentriod-Ru-Cl
125.99
126.55
126.38
126.67
(mimid)] 8a, [Ru(η6-p-cymene)Cl(mimid)2][Cl] 9a, and [Ru-
(η6-p-cymene)(mimid)3][BF4]2 10a was based on 2D NMR
experiments in combination with spectroscopic data and calcula-
tions of Standfest-Hauser et al.34 and Caballero et al.,35 dealing
with related complexes. For the 13C NMR data, only minor
changes are observed between the complexes. However, it must
be mentioned that the NMR spectra of 10a were measured in
acetone-d6 instead of CDCl3, which only allows a tentative com-
parison between the spectral data sets. A continuous shift to
higher frequencies of ∆δ ) 3.1 ppm is observed for the
resonance of C-2′ as the number of imidazole ligands at the
ruthenium(II) center increases. For C-4′ and C-5′, no such trend
is observed. In comparison, very strong changes are observed
for the 1H NMR resonances of the imidazole protons. Between
complexes 8a and 9a, the signals of 2′-H and 5′-H are shifted
to higher frequencies with ∆δ ) 1.32 ppm and ∆δ ) 0.29 ppm,
respectively. The frequencies for 10a are similar to 8a and not,
as perhaps could be expected, to 9a. For 4′-H, a continuous but
only small shift to lower frequencies of ∆δ ) 0.17 ppm is
observed when changing from 8a to 10a. The proton in the 2′-
position becomes more acidic when two imidazole ligands are
attached to the ruthenium center, and to a lesser extent this trend
is also valid for 5′-H. The most extreme position of a signal
corresponding to 2′-H is detected at 9.73 ppm for the complex
[Ru(η6-p-cymene)Cl(vinylimid)2][Cl] 9c. The resonances of 2′-H
for the N-unsubstituted imidazoles 8b, 9d, and 9e are found at
8.03-8.28 ppm. The corresponding peak for 8c is detected at
8.51 ppm.
Figure 6. ORTEP figure of 9a drawn with 30% probability ellipsoids.
Anion and water solvate have been omitted for clarity.
another) per unit cell. The p-cymene group of the metal cation
is rotated to eclipse one of the imidazole ligands with the methyl
substituent. Conversely, the bulkier isopropyl substituent points
away from the imidazole and chloride ligands. The facial
orientation of the imidazole ligands in the solid state is
determined primarily by intermolecular interactions. This is
verified by an analysis of the packing structure, which shows
that the hydrogen atoms of one N-methylimidazole ligand exhibit
intermolecular interactions with the chloride anions and a single
oxygen of water and vice versa for the second imidazole group.
The p-cymene group also forms some weak interactions with
the anionic moieties.
When the imidazole groups are fitted with a longer alkyl chain
(i.e., n-butyl), a different spatial orientation of the ligands is
obtained (Figure 7). Two different complexes containing the
cation [Ru(η6-p-cymene)Cl(bimid)2]+ were crystallographically
studied, one with a simple Cl- counterion (9b, Figure 7) and
another one with the very rarely seen monomeric anion [Ru-
(η6-p-cymene)Cl3]- (13, Figure 8), reported only once previ-
Characterization of the Complexes 9a, 9b, 9e, 10b, and
13 by X-ray Diffraction. For a set of representative complexes,
single crystals suitable for crystallographic structure analysis
by X-ray diffraction were obtained.36 All structures display the
ubiquitous three-legged piano-stool geometry; important bond
lengths and angles are listed in Table 1. Complex 9a (Figure
6) was found to crystallize with two cations, two chloride anions,
and two water solvates (with the oxygen centers facing one

5556 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 18
Vock et al.
fitted into the pocket defined by two imidazole ligands. In
general, the doubly cationic nature of the complex results in
closer anion interactions compared to the other complexes.
Cell Growth Inhibition Effects on TS/A Adenocarcinoma
Cells and HBL-100 Mammary Cells. The biological MTT (3-
(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) test,
which measures mitochondrial dehydrogenase activity as an
indication of cell viability, was carried out with all these water-
soluble compounds except for complex 9e because of its very
low solubility in water. The experiments were performed on
two different cell lines, tumor mouse TS/A cells and normal
human HBL-100 cells, a comparison of cytotoxicity between
the cell lines (the latter as a model for healthy cells) being used
to identify RAPTA compounds as selective antitumor agents.23,25
The effects of these ruthenium compounds on the cell growth
were evaluated by measuring the variations after treatment for
24, 48, and 72 h. The IC50 values for all the compounds studied
are listed in Table 2 for both cell lines (see Supporting
Information, Figure S1, for graphs of the cytotoxic effects).
Figure 7. ORTEP figure of 9b drawn with 30% probability ellipsoids.
The anion has been omitted for clarity.
ously.31 In both cases, the alkyl substituents of the p-cymene
moiety eclipse both bimid ligands. The Ru-Cl and Ru-N bond
distances for 9b (2.422(1), 2.123(3), 2.121(3) Å) and 13 (2.415-
(2), 2.110(5), 2.131(5) Å) remain identical within experimental
error to those in 9a (2.432(1), 2.121(2), 2.131(2) Å). However,
the N-Ru-N angle increases slightly from 83.02(6)° in 9a to
84.56(12)° in 9b and 85.53(6)° in 13. The longer aliphatic chain
has the effect of reducing the number of intermolecular
associations. The majority of present interactions are centered
around the bound chloride groups of the anion and the p-cymene
ligand. However, for 13, one imidazole group is tilted slightly
more to form a weak interaction with the anion. In 9b, the
hydrogens (H2A and H4A) form a symmetric bifurcating
interaction with the chloride (H2A‚‚‚Cl1 2.520 Å, H4A‚‚‚Cl1
2.586 Å).
Compared to cisplatin, for example, from Table 2 it is clear
that all the ruthenium areneimidazole complexes are far less
cytotoxic, yet their cytotoxicities are not too dissimilar to other
ruthenium complexes such as 6 and its toluene derivative [Ru-
(η6-toluene)Cl2(pta)] (RAPTA-T) (see Table 2).23,25 Type 8
compounds exert very little differences in cytotoxicity between
the two cell lines, taken as an indication of potentially poor
selectivity in vivo.
Compounds 9a and 9d do not show any toxicity toward either
cell line even at 1000 µM concentrations. The two compounds,
which contain pyridine and morpholine (as opposed to imid-
azoles), are the only compounds that are actually more cytotoxic
toward the model healthy cells (HBL-100) compared to the
cancer cell model. Combined, it is interesting to note that the
ruthenium complexes that have reached clinical trials to date
are endowed with imidazole or indazole ligands and not other
amines, although their precise roles remain unknown.9,38
The remaining two compounds that were investigated feature
a η6-coordinated benzene instead of p-cymene. For 9e (Figure
9), the first attempt to solve the structure yielded a mixture of
the cations [Ru(η6-benzene)Cl(imid)2]+ and [Ru(η6-benzene)-
(OH) (imid)2]+ in a 9:1 ratio. Regrowing the crystals under more
anhydrous conditions yielded a structure containing only the
chloride containing species. Interestingly, the N-H protons for
both imidazole ligands are engaged in a π-type interaction with
a phenyl group of the borate anion. An extended structure is
thus formed between alternating imidazole groups of the cation
and phenyls of the anion. This type of interaction is uncommon,
but it has been observed in the free N-protonated and N-
The remaining complexes, 9b, 9c, 10a, and 10b, are all more
cytotoxic in the TS/A cancer cell line than the healthy cell
model, the most cytotoxic being 10a but the one showing the
greatest difference in cytotoxicity being [Ru(η6-p-cymene)Cl-
(vinylimid)2][Cl] 9c, which is 2.7-fold more cytotoxic toward
the cancer cells, and [Ru(η6-benzene)(mimid)3][BF4]2 10b,
which is 3-fold more cytotoxic. Such selective cytotoxicity is
characteristic not only of the RAPTA compounds but also of
the [9]aneS3 analogues (e.g., 7 in Figure 1) with pta and
ethylenediamine as coligands.26 Although the cationic ruthe-
nium(II) arene ethylenediamine complexes introduced by Sadler
et al.21,39,40 (e.g., 5 Figure 1) display significantly higher
cytotoxicities in A2780 human ovarian cancer cells, at best IC50
) 2 µM for [RuCl(η6-dihydroanthracene)(en)][PF6], which is
similar to the value of cisplatin with IC50 ) 0.5 µM,40 a direct
comparison is difficult, since these compounds have not been
evaluated against the same cancer cell/healthy cell model for
the determination of selectivity. As far as we are aware, the
ruthenium(II) arene imidazole derivatives 9c and 10b represent
the first compounds of this general type without the pta ligand
to exert such a selectivity in the in vitro assay. While both these
compounds have been selected for further studies, these data
indicate that it is still too early to discern a parallel between
compound structure and biological response, especially since
the most selective compounds were those with substituted
imidazoles rather than imidazole itself that is present in NAMI-
A.
methylated imidazolium salts containing BPh4 .
- 37 The Ru-Cl
distance is slightly shorter (2.407(1) Å) than for the correspond-
ing p-cymene analogues, with the Ru-N bonds (2.122(3) and
2.114(3) Å) being equivalent as well as the N-Ru-N bond
angle (85.00(13)°). Another difference between the η6-p-cymene
and η6-benzene coordinated structures is the orientation of the
imidazole ligand, where in the former, the (Ru)N-C(H)-N(R)
component is always pointing toward the arene and the (Ru)N-
C(H)-C(H)-N(R) part is directed toward the Cl ligand.
However, in the benzene structure 9e (Ar ) C6H6, R ) H), the
ligands are rotated 180° with respect to one another to allow
for the π-type interaction with the phenyl groups of the borate
anion.
Representative for η6-arene ruthenium(II) trisimidazole com-
plexes of type 10, a crystal structure was collected for 10b
(Figure 10). The Ru-N bond distances (2.107(2), 2.108(2),
2.111(2) Å) are equivalent to those for complexes of type 8
and 9. In 10b, the imidazole ligands are arranged into a quasi-
C3 symmetric propeller conformation around the Ru-benzene
axis. The two BF4- anions lie almost parallel to the arene ring,

Ruthenium(II) η6-Areneimidazole Complexes
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 18 5557
Figure 8. ORTEP plot of 13 drawn with 30% probability ellipsoids.
Table 2. IC50 Values of the Complexes on TS/A and HBL-100 Cell
Lines after 72 h of Incubation
IC50 (µM)
compd
TS/A
HBL-100
[Ru(η6-p-cymene)Cl2(pyridine)] (11)
[Ru(η6-p-cymene)Cl2(morpholine)] (12)
[Ru(η6-p-cymene)Cl2(mimid)] (8a)
[Ru(η6-p-cymene)Cl2(benzimid)] (8b)
[Ru(η6-p-cymene)Cl2(benzoylimid)] (8c)
[Ru(η6-p-cymene)Cl(mimid)2][Cl]‚H2O (9a)
[Ru(η6-p-cymene)Cl(bimid)2][Cl] (9b)
[Ru(η6-p-cymene)Cl(vinylimid)2][Cl] (9c)
[Ru(η6-p-cymene)Cl(imid)2][Cl] (9d)
[Ru(η6-p-cymene)(mimid)3][BF4]2 (10a)
[Ru(η6-benzene)(mimid)3][BF4]2 (10b)
[Ru(η6-p-cymene)Cl2(pta)] (6)23
757
640
659
573
723
522
523
790
601
895
>1000
>1000
172
238
361
990
>1000
>1000
136
172
249
740
>300
>300
Figure 9. ORTEP figure of 9e drawn with 30% probability ellipsoids.
The anion has been omitted for clarity.
>300
[Ru(η6-toluene)Cl2(pta)]23
74
pyridine (30 µL, 0.37 mmol, 2.3 equiv) was added at room
temperature. The resulting mixture was heated to reflux for 3 h.
After the mixture was cooled, the precipitate was filtered, washed
with petroleum ether (3 × 10 mL), and dried in vacuo, affording
1
an orange microcristalline solid (78.7 mg, 0.204 mmol, 63%). H
NMR (400 MHz, CDCl3): δ ) 1.31 (d, J ) 6.9 Hz, 6 H, 1-CH-
(CH3)2), 2.10 (s, 3 H, 4-CH3), 3.00 (sept, J ) 6.9 Hz, 1 H,
1-CH(CH3)2), 5.22 (d, J ) 6.0 Hz, 2 H, 2-H, 6-H), 5.44 (d, J )
6.0 Hz, 2 H, 3-H, 5-H), 7.31 (ddd (strongly irregular), J ) 7.6,
5.2, 1.4 Hz, 2 H, 3′-H, 5′-H), 7.74 (tt, J ) 7.6, 1.4 Hz, 1 H, 4′-H),
9.05 (dt (strongly irregular), J ) 5.2, 1.4 Hz, 2 H, 2′-H, 6′-H). 13
C
NMR (100 MHz, CDCl3): δ ) 18.18 (4-CH3), 22.27 (1-CH(CH3)2),
30.63 (1-CH(CH3)2), 82.23 (C-2, C-6), 82.77 (C-3, C-5), 97.02 (C-
4), 103.5 (C-1), 124.5 (C-3′, C-5′), 137.5 (C-4′), 154.9 (C-2′, C-6′).
ESI-MS (CH3CN): m/z (%) ) 390.4 (21) [Ru(cymene)Cl(CH3-
CN)(pyridine)]+, 349.9 (49) [Ru(cymene)Cl(pyridine)]+, 311.9
(100) [Ru(cymene)Cl(CH3CN)]+.
Figure 10. ORTEP figure of 10b drawn with 30% probability
ellipsoids. The anion has been omitted for clarity.
Experimental Details
Synthesis and Chemical Characterization. [RuCl2(η6-p-
cymene)]2 and [RuCl2(η6-benzene)]2 were synthesized following a
literature protocol.41 All other reagents and solvents were obtained
from commercial sources and used without further purification. 1H
and 13C NMR spectra were recorded on a Bruker 400 MHz
spectrometer at room temperature in CDCl3, acetone-d6, DMSO-
d6 or MeOH-d4. The NMR spectra were referenced to internal
[Ru(η6-p-cymene)Cl2(morpholine)] (12). To a suspension of
[Ru(η6-p-cymene)Cl2]2 (100 mg, 0.163 mmol) in toluene (15 mL),
morpholine (30 µL, 0.34 mmol, 2.1 equiv) was added at room
temperature. The resulting mixture was heated to reflux for 3 h.
After the mixture was cooled, the precipitate was filtered, washed
with petroleum ether (4 × 10 mL), and dried in vacuo, affording
1
1
solvents as follows: δ (CHCl3, H) ) 7.26 and δ (CDCl3, 13C) )
an orange microcristalline solid (96.0 mg, 0.244 mmol, 75%). H
77.00; δ (acetone-d5, 1H) ) 2.05 and δ (acetone-d6, 13C) ) 29.84;
δ (DMSO-d5, 1H) ) 2.50 and δ (DMSO-d6, 13C) ) 39.52; δ
(MeOH-d3, 1H) ) 3.31 and δ (MeOH-d4, 13C) ) 49.00.42 Structures
showing the numbering scheme for the NMR assignments are
provided in Supporting Information. Electrospray ionization mass
spectra (ESI-MS) were recorded on a Thermofinigan LCQ Deca
XP Plus quadrupole ion trap instrument in positive mode in MeOH
or CH3CN following a literature procedure.43 Elemental analyses
were provided by the analytical services of EPFL.
NMR (400 MHz, CDCl3): δ ) 1.30 (d, J ) 6.9 Hz, 6 H, 1-CH-
(CH3)2), 2.23 (s, 3 H, 4-CH3), 2.42 (br mc, 1 H, NH), 3.02 (sept, J
) 6.9 Hz, 1 H, 1-CH(CH3)2), 3.23 (qd, J ) 12.4 Hz, JAB ) 3.1
Hz, 2 H, 2′-HA, 6′-HA), 3.45 (td, J ) 12.4 Hz, JAB ) 1.6 Hz, 2 H,
3′-HA, 5′-HA), 3.65 (br d, J ) 12.4 Hz, 2 H, 3′-HB, 5′-HB), 3.86
(dd, J ) 12.4 Hz, JAB ) 3.1 Hz, 2 H, 2′-HB, 6′-HB), 5.30 (d, J )
6.1 Hz, 2 H, 2-H, 6-H), 5.34 (d, J ) 6.1 Hz, 2 H, 3-H, 5-H). 13C
NMR (100 MHz, CDCl3): δ ) 18.39 (4-CH3), 21.98 (1-CH(CH3)2),
30.92 (1-CH(CH3)2), 54.10 (C-2′, C-6′), 69.09 (C-3′, C-5′), 78.00
(C-2, C-6), 82.93 (C-3, C-5), 93.36 (C-4), 104.9 (C-1). ESI-MS
(CH3CN): m/z (%) ) 494.6 (29) [Ru(cymene)(morpholine)3 - H]+,
[Ru(η6-p-cymene)Cl2(pyridine)] (11). To a suspension of [Ru-
(η6-p-cymene)Cl2]2 (100 mg, 0.163 mmol) in toluene (15 mL),

5558 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 18
Vock et al.
398.6 (100) [Ru(cymene)Cl(CH3CN)(morpholine)]+, 352.6 (12)
[Ru(cymene)Cl(CH3CN)2]+.
(C-2, C-6), 82.57 (C-3, C-5), 97.58 (C-4), 103.1 (C-1), 118.2 (C-
5′), 129.3 (C-3′′, C-5′′), 130.1 (C-2′′, C-6′′), 133.0 (C-4′), 134.5
(C-4′′), 141.7 (C-2′), 164.7 (NCO). ESI-MS (CH3CN): m/z (%) )
483.4 (100) [Ru(cymene)Cl(CH3CN)(benzoylimid)]+, 443.0 (65)
[Ru(cymene)Cl(benzoylimid)]+, 352.5 (65) [Ru(cymene)Cl(CH3-
CN)2]+, 311.9 (67) [Ru(cymene)Cl(CH3CN)]+.
[Ru(η6-p-cymene)Cl2(mimid)] (8a). To a suspension of [Ru-
(η6-p-cymene)Cl2]2 (100 mg, 0.163 mmol) in toluene (15 mL),
N-methylimidazole (26 µL, 0.33 mmol, 2.0 equiv) was added at
room temperature. The resulting mixture was heated to reflux for
3 h. After the mixture was cooled, the precipitate was filtered,
washed with petroleum ether (4 × 10 mL), and dried in vacuo,
affording a brown, slightly sticky, and hygroscopic solid (58.7 mg,
[Ru(η6-p-cymene)Cl(mimid)2][Cl]‚H2O (9a). To a suspension
of [Ru(η6-p-cymene)Cl2]2 (100 mg, 0.163 mmol) in iPrOH (15 mL),
N-methylimidazole (100 µL, 1.26 mmol, 7.73 equiv) was added at
room temperature. The resulting mixture was heated to reflux for
8 h. The solvent was removed in vacuo. The residue was taken up
in CH2Cl2, and an excess of EE was added. CH2Cl2 was removed
in vacuo. The obtained turbid solution was decanted from a
precipitated slimy solid and kept standing in air at room temperature
for several hours. Orange crystals precipitated, which were also
suitable for X-ray analysis. The precipitate was filtered and dried
in vacuo, affording an orange crystalline solid (117 mg, 0.240 mmol,
1
0.151 mmol, 46%). H NMR (400 MHz, CDCl3): δ ) 1.28 (d, J
) 6.9 Hz, 6 H, 1-CH(CH3)2), 2.19 (s, 3 H, 4-CH3), 2.99 (sept, J )
6.9 Hz, 1 H, 1-CH(CH3)2), 3.65 (s, 3 H, 1′′-H3), 5.25 (d, J ) 5.7
Hz, 2 H, 2-H, 6-H), 5.44 (d, J ) 5.7 Hz, 2 H, 3-H, 5-H), 6.85 (br
s, 1 H, 4′-H), 7.30 (br s, 1 H, 5′-H), 7.87 (br s, 1 H, 2′-H). 13C
NMR (100 MHz, CDCl3): δ ) 18.54 (4-CH3), 22.22 (1-CH(CH3)2),
30.65 (1-CH(CH3)2), 34.52 (C-1′′), 81.41 (C-2, C-6), 82.45 (C-3,
C-5), 97.24 (C-4), 102.6 (C-1), 120.7 (C-4′), 132.2 (C-5′), 140.4
(C-2′). ESI-MS (CH3CN): m/z (%) ) 393.4 (10) [Ru(cymene)Cl-
(CH3CN)(mimid)]+, 353.0 (100) [Ru(cymene)Cl(mimid)]+, 311.9
(28) [Ru(cymene)Cl(CH3CN)]+.
73%).
1H NMR (400 MHz, CDCl3): δ ) 1.13 (d, J ) 6.9 Hz, 6
H, 1-CH(CH3)2), 1.78 (s, 3 H, 4-CH3), 2.37 (sept, J ) 6.9 Hz, 1 H,
1-CH(CH3)2), 3.77 (s, 6 H, 2 × 1′′-H3), 5.83 (d, J ) 6.3 Hz, 2 H,
2-H, 6-H), 5.86 (d, J ) 6.3 Hz, 2 H, 3-H, 5-H), 6.77 (t, J ) 1.5
Hz, 2 H, 2 × 4′-H), 7.59 (t, J ) 1.5 Hz, 2 H, 2 × 5′-H), 9.19 (br
s, 2 H, 2 × 2′-H). 13C NMR (100 MHz, CDCl3): δ ) 17.85 (4-
CH3), 22.21 (1-CH(CH3)2), 30.73 (1-CH(CH3)2), 34.69 (2 × C-1′′),
82.19 (C-2, C-6), 85.92 (C-3, C-5), 100.4 (C-4), 103.3 (C-1), 120.6
(2 × C-4′), 130.6 (2 × C-5′), 142.1 (2 × C-2′). ESI-MS (MeOH):
m/z (%) ) 565.1 (5) [Ru2(cymene)2(MeOH)3]+, 434.9 (100) [Ru-
(cymene)(mimid)2Cl]+, 353.1 (4) [Ru(cymene)(mimid)Cl]+.
[Ru(η6-p-cymene)Cl(bimid)2][Cl] (9b). To a suspension of [Ru-
(η6-p-cymene)Cl2]2 (100 mg, 0.163 mmol) in iPrOH (15 mL),
N-butylimidazole (150 µL, 1.14 mmol, 7.00 equiv) was added at
room temperature. The resulting mixture was heated to reflux for
8 h. The solvent was evaporated in vacuo. The residue was taken
up in EE, and the solution was filtered over a short pad of silica
gel. Excess of imidazole ligand was washed down with EE, and
the ruthenium complex was subsequently eluted with CHCl3/EtOH
(3:1). Evaporation of the solvent and crystallization of the residue
from EE/Et2O yielded a yellow crystalline compound (91.1 mg,
0.164 mmol, 50%). Crystals suitable for X-ray analysis were
obtained by slow crystallization from EE/Et2O. 1H NMR (400 MHz,
CDCl3): δ ) 0.90 (t, J ) 7.4 Hz, 6 H, 2 × 4′′-H3), 1.12 (d, J )
6.9 Hz, 6 H, 1-CH(CH3)2), 1.16-1.32 (m, 4 H, 2 × 3′′-H2), 1.71-
1.79 (m, 4 H, 2 × 2′′-H2), 1.77 (s, 3 H, 4-CH3), 2.37 (sept, J ) 6.9
Hz, 1 H, 1-CH(CH3)2), 4.01 (t, J ) 7.2 Hz, 4 H, 2 × 1′′-H2), 5.85
(d, J ) 6.1 Hz, 2 H, 2-H, 6-H), 5.89 (d, J ) 6.1 Hz, 2 H, 3-H,
5-H), 6.79 (t, J ) 1.4 Hz, 2 H, 2 × 4′-H), 7.62 (t, J ) 1.4 Hz, 2
H, 2 × 5′-H), 9.22 (t, J ) 1.4 Hz, 2 H, 2 × 2′-H). 13C NMR (100
MHz, CDCl3): δ ) 13.46 (2 × C-4′′), 17.80 (4-CH3), 19.47 (2 ×
C-3′′), 22.22 (1-CH(CH3)2), 30.81 (1-CH(CH3)2), 32.58 (2 × C-2′′),
47.92 (2 × C-1′′), 82.32 (C-2, C-6), 85.94 (C-3, C-5), 100.4 (C-
4), 103.3 (C-1), 119.1 (2 × C-4′), 130.5 (2 × C-5′), 141.5 (2 ×
C-2′). ESI-MS (MeOH): m/z (%) ) 519.0 (100) [Ru(cymene)-
(bimid)2Cl]+, 395.3 (6) [Ru(cymene)(bimid)Cl]+.
[Ru(η6-p-cymene)Cl2(benzimid)] (8b). To a suspension of [Ru-
(η6-p-cymene)Cl2]2 (100 mg, 0.163 mmol) in toluene (15 mL),
benzimidazole (40.0 mg, 0.339 mmol, 2.08 equiv) was added at
room temperature. The resulting mixture was heated to reflux for
2.5 h. After the mixture was cooled, the precipitate was filtered,
washed with petroleum ether (4 × 10 mL), and dried in vacuo,
affording an orange-brown solid (88.0 mg, 0.207 mmol, 64%). 1H
NMR (400 MHz, CDCl3): δ ) 1.26 (d, J ) 6.9 Hz, 6 H, 1-CH-
(CH3)2), 2.04 (s, 3 H, 4-CH3), 2.87 (sept, J ) 6.9 Hz, 1 H,
1-CH(CH3)2), 5.39 (d, J ) 5.7 Hz, 2 H, 2-H, 6-H), 5.57 (d, J )
5.7 Hz, 2 H, 3-H, 5-H), 6.60-6.66 (br m, 2 H, 6′-H, 7′-H), 6.92-
7.00 (br m, 1 H, 5′-H), 7.60 (d, J ) 8.2 Hz, 1 H, 4′-H), 8.12 (br s,
1 H, 2′-H), 10.44 (br s, 1 H, NH). 13C NMR (100 MHz, CDCl3):
δ ) 18.44 (4-CH3), 22.24 (1-CH(CH3)2), 30.64 (1-CH(CH3)2), 80.78
(C-2, C-6), 82.73 (C-3, C-5), 97.32 (C-4), 102.6 (C-1), 112.5 (C-
7′), 118.5 (C-4′), 121.9 (C-5′), 123.2 (C-6′), 132.1 (C-7′a), 140.0
(C-3′a), 144.7 (C-2′). ESI-MS (CH3CN): m/z (%) ) 429.5 (100)
[Ru(cymene)Cl(CH3CN)(benzimid)]+, 389.0 (26) [Ru(cymene)Cl-
(benzimid)]+, 352.5 (23) [Ru(cymene)Cl(CH3CN)2]+, 311.9 (52)
[Ru(cymene)Cl(CH3CN)]+.
Synthesis of N-Benzoylimidazole (Benzoylimid). To a solution
of imidazole (1.36 g, 20 0 mmol, 2.00 equiv) in CH2Cl2 (15 mL),
benzoyl chloride (1.16 mL, 9.99 mmol) was added at room
temperature over 3 min. The resulting mixture was stirred at room
temperature for 75 min. The precipitate was filtered and washed
with CH2Cl2 (3 × 5 mL). The combined filtrates were evaporated
in vacuo, affording a slightly yellow oily liquid that was used
1
without further purification. H NMR (400 MHz, CDCl3): δ )
7.16-7.18 (br m, 1 H, 4-H), 7.52-7.59 (m, 3 H, 5-H, 3′-H, 5′-H),
7.69 (tt, J ) 6.9, 1.5 Hz, 1 H, 4′-H), 7.80 (dt, J ) 6.6, 1.5 Hz,
2′-H, 6′-H), 8.08 (br s, 1 H, 2-H).
[Ru(η6-p-cymene)Cl2(benzoylimid)] (8c). To a solution of [Ru-
(η6-p-cymene)Cl2]2 (250 mg, 0.408 mmol) in CH2Cl2 (10 mL), a
solution of N-benzoylimidazole (142 mg, 0.825 mmol, 2.02 equiv)
in CH2Cl2 (3 mL) was added at room temperature. The resulting
mixture was stirred at room temperature for 2 h. Addition of
petroleum ether (60 mL) led to the separation of an oil, which was
redissolved by addition of CH2Cl2 (50 mL). The solution was
reduced in vacuo to a volume of approximately 20 mL. Strong
crystallization set in, which was accomplished by keeping the
solution at room temperature for an additional 30 min. The
precipitate was filtered with suction, washed with petroleum ether
(2 × 10 mL), and dried in vacuo, affording an orange-brown
crystalline solid (320 mg, 0.669 mmol, 82%). 1H NMR (400 MHz,
CDCl3): δ ) 1.30 (d, J ) 6.9 Hz, 6 H, 1-CH(CH3)2), 2.21 (s, 3 H,
4-CH3), 2.99 (sept, J ) 6.9 Hz, 1 H, 1-CH(CH3)2), 5.30 (d, J )
5.8 Hz, 2 H, 2-H, 6-H), 5.48 (d, J ) 5.8 Hz, 2 H, 3-H, 5-H), 7.49
(s, 1 H, 5′-H), 7.55 (s, 1 H, 4′-H), 7.56 (t, J ) 7.6 Hz, 2 H, 3′′-H,
5′′-H), 7.70 (t, J ) 7.6 Hz, 1 H, 4′′-H), 7.77 (d, J ) 7.6 Hz, 2 H,
2′′-H, 6′′-H), 8.51 (s, 1 H, 2′-H). 13C NMR (100 MHz, CDCl3): δ
) 18.61 (4-CH3), 22.22 (1-CH(CH3)2), 30.72 (1-CH(CH3)2), 81.49
[Ru(η6-p-cymene)Cl(vinylimid)2][Cl] (9c). To a suspension of
[Ru(η6-p-cymene)Cl2]2 (100 mg, 0.163 mmol) in nBuOH (15 mL),
N-vinylimidazole (60 µL, 0.66 mmol, 4.0 equiv) was added at room
temperature. The resulting mixture was heated to reflux for 4 h.
The solvent was removed in vacuo as azeotrope with toluene. The
residue was taken up in CH2Cl2, and an excess of EE was added.
CH2Cl2 was removed in vacuo. Addition of a large excess of Et2O
led to the formation of a yellow precipitate. The supernatant was
pipetted off. The precipitate was washed with Et2O (2 × 5 mL)
and dried in vacuo, affording a yellow, very moisture-sensitive solid
1
(49.6 mg, 0.100 mmol, 31%). H NMR (400 MHz, CDCl3): δ )
1.15 (d, J ) 6.9 Hz, 6 H, 1-CH(CH3)2), 1.82 (s, 3 H, 4-CH3), 2.39
(sept, J ) 6.9 Hz, 1 H, 1-CH(CH3)2), 5.03 (dd, J ) 8.9, 2.3 Hz, 2
H, 2 × 2′′-Hcis), 5.58 (dd, J ) 15.8, 2.3 Hz, 2 H, 2 × 2′′-Htrans),
5.88 (d, J ) 6.1 Hz, 2 H, 2-H, 6-H), 5.92 (d, J ) 6.1 Hz, 2 H, 3-H,
5-H), 7.05 (dd, J ) 15.8, 8.9 Hz, 2 H, 2 × 1′′-H), 7.07 (t, J ) 1.7
Hz, 2 H, 2 × 4′-H), 7.68 (br s, 2 H, 2 × 5′-H), 9.73 (br s, 2 H, 2
× 2′-H). 13C NMR (100 MHz, CDCl3): δ ) 17.93 (4-CH3), 22.22

Ruthenium(II) η6-Areneimidazole Complexes
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 18 5559
(1-CH(CH3)2), 30.82 (1-CH(CH3)2), 82.55 (C-2, C-6), 86.04 (C-3,
C-5), 100.6 (C-4), 103.6 (C-1), 104.3 (2 × C-2′′), 116.0 (2 × C-4′),
129.0 (2 × C-1′′), 130.7 (2 × C-5′), 141.0 (2 × C-2′). ESI-MS
(MeOH): m/z (%) ) 565.1 (5) [Ru2(cymene)2(MeOH)3]+, 458.9
(100) [Ru(cymene)(vinylimid)2Cl]+, 367.1 (2) [Ru(cymene) (vi-
nylimid)Cl]+.
2-H, 6-H), 6.21 (d, J ) 6.2 Hz, 2 H, 3-H, 5-H), 6.68 (t, J ) 1.3
Hz, 3 H, 3 × 4′-H), 7.34 (t, J ) 1.3 Hz, 3 H, 3 × 5′-H), 8.19 (br
s, 3 H, 3 × 2′-H). 13C NMR (100 MHz, acetone-d6): δ ) 17.89
(4-CH3), 22.43 (1-CH(CH3)2), 31.18 (1-CH(CH3)2), 35.08 (3 ×
C-1′′), 84.12 (C-2, C-6), 87.82 (C-3, C-5), 104.5 (C-4), 106.2 (C-
1), 123.7 (3 × C-4′), 131.7 (3 × C-5′), 143.5 (3 × C-2′). ESI-MS
(CH3CN): m/z (%) ) 568.9 (50) [Ru(cymene)(mimid)3(BF4)]+,
[Ru(η6-p-cymene)Cl(imid)2][Cl] (9d). To a suspension of [Ru-
(η6-p-cymene)Cl2]2 (100 mg, 0.163 mmol) in iPrOH (15 mL),
imidazole (50.0 mg, 0.734 mmol, 4.50 equiv) was added at room
temperature. The resulting mixture was heated to reflux for 8 h.
After the mixture was cooled, the solution was decanted from some
precipitate, and the solvent was removed in vacuo. The residue
was taken up in CH2Cl2, and an excess of EE was added. CH2Cl2
was removed in vacuo. The obtained turbid solution was kept
standing under N2 at room temperature for 1.5 days. The supernatant
was decanted, and the formed precipitate was dried in vacuo,
affording a very hygroscopic yellow solid (63.7 mg, 0.144 mmol,
240.9 (100) [Ru(cymene)(mimid)3]2+
.
[Ru(η6-benzene)(mimid)3][BF4]2 (10b). To a suspension of [Ru-
(η6-benzene)Cl2]2 (100 mg, 0.200 mmol) in CHCl3 (10 mL),
N-methylimidazole (110 µL, 1.39 mmol, 6.93 equiv) and AgBF4
(164 mg, 0.842 mmol, 4.21 equiv) were added at room temperature.
The resulting mixture was stirred at room temperature in the dark
for 2 h and then filtered over a short pad of Celite. The filter cake
was washed with CHCl3 (2 × 10 mL) and MeOH (4 × 10 mL).
The collected filtrates were evaporated in vacuo. The residue was
taken up in EE (30 mL) and CH2Cl2 (15 mL). The mixture was
stirred at 40 °C for 10 min, and CH2Cl2 was removed in vacuo.
The yellow EE solution was decanted from some insoluble slimy
precipitate. The residue was extracted again with EE (20 mL) at
room temperature. The combined extracts were concentrated in
vacuo until strong crystallization set in. The precipitate was filtered,
washed with EE (2 × 5 mL), and dried in vacuo, affording a gray-
yellow crystalline solid (52.2 mg, 87.1 µmol, 22%). Crystals suitable
for X-ray analysis were obtained by slow crystallization from
MeOH/EE. 1H NMR (400 MHz, acetone-d6): δ ) 3.82 (s, 9 H, 3
× 1′′-H3), 6.22 (s, 6 H, 1-H - 6-H), 6.71 (t, J ) 1.4 Hz, 3 H, 3 ×
4′-H), 7.36 (t, J ) 1.4 Hz, 3 H, 3 × 5′-H), 8.01 (br s, 3 H, 3 ×
2′-H). 13C NMR (100 MHz, acetone-d6): δ ) 35.13 (3 × C-1′′),
87.99 (C-1 - C-6), 123.8 (3 × C-4′), 131.6 (3 × C-5′), 143.2 (3
× C-2′). ESI-MS (CH3CN): m/z (%) ) 512.9 (18) [Ru(benzene)-
(mimid)3(BF4)]+, 212.9 (100) [Ru(benzene)(mimid)3]2+, 192.4 (39)
1
44%). H NMR (400 MHz, CDCl3): δ ) 1.21 (d, J ) 6.5 Hz, 6
H, 1-CH(CH3)2), 1.72 (s, 3 H, 4-CH3), 2.42 (sept, J ) 6.5 Hz, 1 H,
1-CH(CH3)2), 5.61 (d, J ) 6.0 Hz, 2 H, 2-H, 6-H), 5.71 (d, J )
6.0 Hz, 2 H, 3-H, 5-H), 6.92 (br s, 2 H, 2 × 4′-H), 7.32 (br s, 2 H,
2 × 5′-H), 8.28 (br s, 2 H, 2 × 2′-H); NH not detected. 13C NMR
(100 MHz, CDCl3): δ ) 17.77 (4-CH3), 22.22 (1-CH(CH3)2), 30.69
(1-CH(CH3)2), 81.61 (C-2, C-6), 85.05 (C-3, C-5), 100.4 (C-4),
103.2 (C-1), 117.1 (2 × C-4′), 129.5 (2 × C-5′), 138.8 (2 × C-2′).
ESI-MS (MeOH): m/z (%) ) 406.8 (100) [Ru(cymene)(imid)2Cl]+.
[Ru(η6-benzene)Cl(imid)2][BPh4] (9e). To a suspension of [Ru-
(η6-benzene)Cl2]2 (100 mg, 0.200 mmol) and imidazole (85.0 mg,
1.25 mmol, 6.24 equiv) in acetone (15 mL), NaBPh4 (300 mg, 0.877
mmol, 4.38 equiv) was added at room temperature. The resulting
brown suspension was heated to reflux for 4 h. Still slightly warm,
the resulting gray-green suspension containing some light-brown
solid was filtered over a short pad of Celite. The filter cake was
washed with acetone (4 × 20 mL), iPrOH (2 × 20 mL), and acetone
(20 mL). The combined filtrates were reduced in vacuo to a volume
of approximately 6-7 mL. A dark-yellow to brown precipitate
began to form. The solution was stored at -25 °C for 20 min to
accomplish crystallization. The formed precipitate was filtered with
suction, washed with iPrOH (2 × 5 mL), and dried in vacuo,
affording a dark-yellow crystalline solid (132 mg, 0.197 mmol,
49%). Crystals suitable for X-ray analysis were obtained from
acetone/iPrOH by slow evaporation. Higher quality crystals were
obtained by carefully layering an acetone solution of the compound
[Ru(benzene)(mimid)2(CH3CN)]2+
.
Single-Crystal X-ray Analysis. Crystals suitable for analysis
by X-ray diffraction were coated with hydrocarbon oil and mounted
on the end of a thin glass fiber, and the crystal was immersed in a
rapid stream of low-temperature N2. The primary and cell reflection
data were collected using either a Bruker Kappa/Apex II or Oxford
Diffraction KM4/sapphire diffractometer, both equipped with
graphite monochromated Mo KR radiation and a CCD detector.
Standard reflections were continuously monitored for crystal
deterioration; none of the samples demonstrated any form of decay.
Cell parameters and space group determination were performed
using the program Dirax44 or CrysAlis CCD45 by Oxford Diffrac-
tion. Reflection data was processed using EvalCCD46 or CrysAlis
RED45 software, and absorption correction based on the multiscan
method was obtained through the SADABS47 program. Structure
solutions were obtained using SIR9248 or SHELXS;49 in both cases
a direct method algorithm was employed. Structure refinement using
SHELXL49 involved continuous cycles of full matrix least-squares
refinement on F2. All non-hydrogen atoms were refined anisotro-
pically; hydrogens atoms with strong data were located, but most
were placed in geometry calculated positions and refined with a
riding model. Graphical representation of the structure was made
with ORTEP-3.50 Hydrogens bonded to water were fixed according
to standard bond lengths. The important crystallographic parameters
for each structure are given in Table S1 in Supporting Information.
In Vitro Tests. TS/A murine adenocarcinoma cell lines, initially
obtained from Dr. G. Forni (CNR, Centro di Immunogenetica ed
Oncologia Sperimentale, Torino, Italy), belong to the tumor cell
panel of the Callerio Foundation and are stored in liquid nitrogen.
Cells were cultured according to a standard procedure51 and
maintained in RPMI-1640 medium (EuroClone, Wetherby, U.K.)
supplemented with 10% fetal bovine serum (FBS, Invitrogen,
Milano, Italy), 2 mM L-glutamine (EuroClone, Wetherby, U.K.),
and 50 µg/mL gentamycin sulfate solution (EuroClone, Wetherby,
U.K.). The cell line was kept in a CO2 incubator with 5% CO2 and
100% relative humidity at 37 °C. Cells from a confluent monolayer
were removed from flasks by a trypsin-EDTA solution (EuroClone,
Wetherby, U.K.).
1
with Et2O. H NMR (400 MHz, acetone-d6): δ ) 5.91 (s, 6 H,
1-H - 6-H), 6.78 (br t, J ) 7.3 Hz, 4 H, 4 × para-H {BPh4}),
6.92 (t, J ) 7.4 Hz, 8 H, 8 × meta-H {BPh4}), 7.26 (t, J ) 1.4 Hz,
2 H, 2 × 4′-H), 7.29-7.36 (br m, 10 H, 2 × 5′-H, 8 × ortho-H
{BPh4}), 8.03 (br s, 2 H, 2 × 2′-H); NH not detected. 13C NMR
(100 MHz, acetone-d6): δ ) 86.13 (C-1 to C-6), 118.5 (2 × C-4′),
122.3 (4 × para-C {BPh4}), 125.3 (q, JCB ) 2.8 Hz, 8 × meta-C
{BPh4}), 131.5 (2 × C-5′), 137.0 (q, JCB ) 1.4 Hz, 8 × ortho-C
{BPh4}), 139.8 (2 × C-2′), 164.9 (q, JCB ) 49.4 Hz, 4 × ipso-C
{BPh4}). ESI-MS (MeOH): m/z (%) ) 406.8 (100) [Ru(cymene)-
(imid)2Cl]+.
[Ru(η6-p-cymene)(mimid)3][BF4]2 (10a). To a suspension of
[Ru(η6-p-cymene)Cl2]2 (100 mg, 0.163 mmol) in MeOH (10 mL),
N-methylimidazole (80 µL, 1.0 mmol, 6.2 equiv) and AgBF4 (128
mg, 0.658 mmol, 4.03 equiv) were added at room temperature. The
resulting mixture was stirred at room temperature in the dark for 2
h and then filtered over a short pad of Celite. The filter cake was
washed with MeOH (5 × 15 mL). The collected filtrates were
evaporated in vacuo to a volume of approximately 10 mL. EE (30
mL) was added, and the solvent was then removed in vacuo until
the beginning of crystallization. After standing at room temperature
for 1 h, the formed crystals were filtered with suction, washed with
EE (2 × 5 mL), and dried in vacuo, affording an intensive yellow
crystalline solid (124 mg, 0.189 mmol, 58%). Crystals suitable for
X-ray analysis were obtained by slow crystallization from MeOH/
EE. 1H NMR (400 MHz, acetone-d6): δ ) 1.12 (d, J ) 6.9 Hz, 6
H, 1-CH(CH3)2), 1.83 (s, 3 H, 4-CH3), 2.45 (sept, J ) 6.9 Hz, 1 H,
1-CH(CH3)2), 3.85 (s, 9 H, 3 × 1′′-H3), 5.95 (d, J ) 6.2 Hz, 2 H,

5560 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 18
Vock et al.
(12) Gava, B.; Zorzet, S.; Spessotto, P.; Cocchietto, M.; Sava, G. Inhibition
of B16 melanoma metastases with the ruthenium complex imidazo-
lium trans-imidazoledimethylsulfoxide-tetrachlororuthenate and down-
regulation of tumor cell invasion. J. Pharmacol. Exp. Ther. 2006,
317, 284-291.
(13) Sava, G.; Zorzet, S.; Turrin, C.; Vita, F.; Soranzo, M.; Zabucchi,
G.; Cocchietto, M.; Bergamo, A.; DiGiovine, S.; Pezzoni, G.; Sartor,
L.; Garbisa, S. Dual action of NAMI-A in inhibition of solid tumor
metastasis: Selective targeting of metastatic cells and binding to
collagen. Clin. Cancer Res. 2003, 9, 1898-1905.
(14) Vacca, A.; Bruno, M.; Boccarelli, A.; Coluccia, M.; Ribatti, D.;
Bergamo, A.; Garbisa, S.; Sartor, L.; Sava, G. Inhibition of endothelial
cell functions and of angiogenesis by the metastasis inhibitor NAMI-
A. Br. J. Cancer 2002, 86, 993-998.
(15) Seelig, M. H.; Berger, M. R.; Keppler, B. K. Antineoplastic activity
of three ruthenium derivatives against chemically induced colorectal
carcinoma in rats. J. Cancer. Res. Clin. Oncol. 1992, 118, 195-
200.
(16) Jakupec, M. A.; Arion, V. B.; Kapitza, S.; Reisner, E.; Eichinger,
A.; Pongratz, M.; Marian, B.; Graf von Keyserlingk, N.; Keppler,
B. K. KP1019 (FFC14A) from bench to bedside: preclinical and
early clinical development. An overview. Int. J. Clin. Pharmacol.
Ther. 2005, 43, 595-596.
(17) Allardyce, C. S.; Dorcier, A.; Scolaro, C.; Dyson, P. J. Development
of organometallic (organo-transition metal) pharmaceuticals. Appl.
Organomet. Chem. 2005, 19, 1-10.
(18) Vessieres, A.; Top, S.; Beck, W.; Hillard, E.; Jaouen, G. Metal
complex SERMs (selective oestrogen receptor modulators). The
influence of different metal units on breast cancer cell antiproliferative
effects. Dalton Trans. 2006, 529-541.
(19) Bioorganometallics; Jaouen, G., Ed.; Wiley-VCH: Weinheim,
Germany, 2005.
(20) Dale, L. D.; Tocher, J. H.; Dyson, T. M.; Edwards, D. I.; Tocher, D.
A. Studies on DNA damage and induction of SOS repair by novel
multifunctional bioreducible compounds. II. A metronidazole adduct
of a ruthenium-arene compound. Anti-Cancer Drug Des. 1992, 7,
3-14.
(21) Morris, R. E.; Aird, R. E.; del Socorro Murdoch, P.; Chen, H.;
Cummings, J.; Hughes, N. D.; Parsons, S.; Parkin, A.; Boyd, G.;
Jodrell, D. I.; Sadler, P. J. Inhibition of cancer cell growth by
ruthenium(II) arene complexes. J. Med. Chem. 2001, 44, 3616-3621.
(22) Allardyce, C. S.; Dyson, P. J.; Ellis, D. J.; Heath, S. L. [Ru(η6-p-
cymene)Cl2(pta)] (pta ) 1,3,5-triaza-7-phosphatricyclo[3.3.1.1]-
decane: a water soluble compound that exhibits pH dependent DNA
binding providing selectivity for diseased cells. Chem. Commun.
2001, 1396-1397.
(23) Scolaro, C.; Bergamo, A.; Brescacin, L.; Delfino, R.; Cocchietto,
M.; Laurenczy, G.; Geldbach, T. J.; Sava, G.; Dyson, P. J. In vitro
and in vivo evaluation of ruthenium(II)-arene PTA complexes. J.
Med. Chem. 2005, 48, 4161-4171.
(24) Dorcier, A.; Dyson, P. J.; Gossens, C.; Rothlisberger, U.; Scopelliti,
R.; Tavernelli, I. Binding of organometallic ruthenium(II) and
osmium(II) complexes to an oligo-nucleotide: a combined mass
spectrometric and theoretical study. Organometallics 2005, 24, 2114-
2123.
(25) Scolaro, C.; Geldbach, T. J.; Rochat, S.; Dorcier, A.; Gossens, C.;
Bergamo, A.; Cocchietto, M.; Tavernelli, I.; Sava, G.; Rothlisberger,
U.; Dyson, P. J. Influence of hydrogen-bonding substituents on the
cytotoxicity of RAPTA compounds. Organometallics 2006, 25, 756-
765.
(26) Serli, B.; Zangrando, E.; Gianferrara, T.; Scolaro, C.; Dyson, P. J.;
Bergamo, A.; Alessio, E. Is the aromatic fragment of piano-stool
ruthenium compounds an essential feature for anticancer activity?
The development of new RuII-[9]aneS3 analogues. Eur. J. Inorg.
Chem. 2005, 3423-3434.
HBL-100 nontumorigenic human breast cells obtained from
ATCC (American Type Culture Collection) were maintained in
McCoy’s 5A medium (Sigma, St. Louis, MO) supplemented with
10% FBS, 2 mM L-glutamine, 100 UI/mL penicillin, and 100 µg/
mL streptomycin (EuroClone, Whetherby, U.K.) in a humidified
atmosphere with 5% CO2 at 37 °C.
Cell viability was determined by the trypan blue dye exclusion
test. For experimental purposes, the cells were sown in multiwell
cell culture plastic plates (Corning Costar Italia, Milano, Italy). Cell
growth was determined by the MTT viability test.52 Cells were sown
on 96-well plates and 24 h after were incubated with the appropriate
compound at 1-300 µM, prepared by dissolving in a medium
containing 5% of serum for 24, 48, and 72 h. Analysis was
performed at the end of the incubation time. Briefly, MTT [3-(4,5-
dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] dissolved
in PBS (5 mg/mL) was added (10 µL per 100 µL of medium) to
all wells, and the plates were then incubated at 37 °C with 5%
CO2 and 100% relative humidity for 4 h. After this time, the
medium was discarded and 100 µL of DMSO (Sigma, St. Louis,
MO) was added to each well according to the method of Alley et
al.53 Optical density was measured at 570 nm on a SpectraCount
Packard (Meriden, CT) instrument. Graphs indicating the cytotoxic
effects of 8a-c, 9b,c, and 10a,10b on TS/A and HBL-100 cells
are provided in Figure S1 of Supporting Information.
Acknowledgment. We thank the Swiss National Science
Foundation, the EPFL, COST (Switzerland), LINFA Labora-
tories, and CRTrieste Foundation for financial support. A
postdoc stipend provided from the German Academic Exchange
Service (DAAD) for C.A.V. is gratefully acknowledged.
Supporting Information Available: Crystallographic data in
CIF format, structures for all synthesized compounds with number-
ing schemes for NMR assignments, elemental analysis results,
crystallographic parameters, and cell viability studies. This material
is available free of charge via the Internet at http://pubs.acs.org.
References
(1) Rosenberg, B.; Vancamp, L.; Krigas, T. Inhibition of cell division
in Escherichia coli by electrolysis products from a platinum electrode.
Nature 1965, 205, 698-699.
(2) Rosenberg, B.; Vancamp, L.; Trosko, J. E.; Mansour, V. H. Platinum
compounds: a new class of potent antitumour agents. Nature 1969,
222, 385.
(3) Allardyce, C. S.; Dyson, P. J. Ruthenium in medicine: current clinical
uses and future prospects. Platinum Met. ReV. 2001, 45, 62-69.
(4) Cocchietto, M.; Sava, G. Blood concentration and toxicity of the
antimetastasis agent NAMI-A following repeated intravenous treat-
ment in mice. Pharmacol. Toxicol. 2000, 87, 193-197.
(5) Zorzet, S.; Sorc, A.; Casarsa, C.; Cocchietto, M.; Sava, G. Pharmo-
cological effects of the ruthenium complex NAMI-A given orally to
CBA mice with MCa mammary carcinoma. Met.-Based Drugs 2001,
8, 1-7.
(6) Sava, G.; Bergamo, A. Ruthenium-based compounds and tumour
growth control (review). Int. J. Oncol. 2000, 17, 353-365.
(7) Gagliardi, R.; Sava, G.; Pacor, S.; Mestroni, G.; Alessio, E.
Antimetastatic action and toxicity on healthy tissues of Na-[trans-
RuCl4(DMSO)Im] in the mouse. Clin. Exp. Metastasis 1994, 12, 93-
100.
(27) Pandey, D. S.; Sahay, A. N.; Agarwala, U. C. Synthesis and
characterisation of [Ru(η6-C6Me6)Cl2(CNPy)] and [Cl2(η6-C6Me6)-
Ru(µ-CNPy)Ru(η6-C6Me6)Cl2] and reactivity of [Ru(η6-C6Me6)Cl2-
(CNPy)] with various bases. Indian J. Chem. 1996, A35, 434-437.
(28) Singh, S. K.; Trivedi, M.; Chandra, M.; Sahay, A. N.; Pandey, D. S.
Luminiscent piano-stool complexes incorporating 1-(4-cyanophenyl)-
imidazole: synthesis, spectral and structural studies. Inorg. Chem.
2004, 43, 8600-8608.
(29) Bennett, M. A.; Smith, A. K. Arene ruthenium(II) complexes formed
by dehydrogenation of cyclohexadienes with ruthenium(III) trichlo-
ride. J. Chem. Soc., Dalton Trans. 1974, 233-241.
(30) Zaramella, S.; Stro¨mberg, R.; Yeheskiely, E. Stability studies of
N-acylimidazoles. Eur. J. Org. Chem. 2002, 2633-2639.
(31) Cabeza, J. A.; da Silva, I.; del Rio, I.; Garcia-Granda, S. [N,N′-Bis-
(6-methylpyrid-2-ylium)-(1R,2R)-1,2-diaminocyclohexane] bis-[(p-
cymene)-trichlororuthenate(II)]. Appl. Organomet. Chem. 2005, 19,
209-210.
(8) Magnarin, M.; Bergamo, A.; Carotenuto, M. E.; Zorzet, S.; Sava, G.
Increase of tumour-infiltrating lymphocytes in mice treated with
antimetastatic doses of NAMI-A. Anticancer Res. 2000, 20, 2939-
2944.
(9) Rademaker-Lakhai, J. M.; Van den Bongard, D.; Pluim, D.; Beijnen,
J. H.; Schellens, J. H. A phase I and pharmacological study with
imidazolium-trans-DMSO-imidazole-tetrachlororuthenate, a novel
ruthenium anticancer agent. Clin. Cancer Res. 2004, 10, 3717-3727.
(10) Sava, G.; Frausin, F.; Cocchietto, M.; Vita, F.; Podda, E.; Spessotto,
P.; Furlani, A.; Scarcia, V.; Zabucchi, G. Actin-dependent tumour
cell adhesion after short-term exposure to the anti-metastasis
ruthenium complex NAMI-A. Eur. J. Cancer 2004, 40, 1383-1396.
(11) Zorzet, S.; Bergamo, A.; Cocchietto, M.; Sorc, A.; Gava, B.; Alessio,
E.; Iengo, E.; Sava, G. Lack of in vitro cytotoxicity, associated to
increased G(2)-M cell fraction and inhibition of Matrigel invasion,
may predict in vivo-selective antimetastasis activity of ruthenium
complexes. J. Pharmacol. Exp. Ther. 2000, 295, 927-933.

Ruthenium(II) η6-Areneimidazole Complexes
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 18 5561
(32) Robertson, D. R.; Stephenson, T. A. Cationic and anionic complexes
of ruthenium(II) containing η6-arene ligands. J. Organomet. Chem.
1976, 116, C29-C30.
(33) Robertson, D. R.; Stephenson, T. A.; Arthur, T. Cationic, neutral
and anionic complexes of ruthenium(II) containing η6-arene ligands.
J. Organomet. Chem. 1978, 162, 121-136.
(42) Gottlieb, H. E.; Kotlyar, V.; Nudelman, A. NMR chemical shifts of
common laboratory solvents as trace impurities. J. Org. Chem. 1997,
62, 7512-7515.
(43) Dyson, P. J.; McIndoe, J. S. Analysis of organometallic compounds
using ion trap mass spectrometry. Inorg. Chim. Acta 2003, 354, 68-
74.
(34) Standfest-Hauser, C. M.; Schmid, R.; Kirchner, K.; Mereiter, K.
Formation of a hydroxo-bridged dinuclear Ru(III)/Ru(III) complex
from N-methylimidazole and [RuCp(CH3CN)3]+. Monatsh. Chem.
2004, 135, 911-917.
(35) Caballero, A.; Jalon, F. A.; Manzano, B. R.; Espino, G.; Perez-
Manrique, M.; Mucientes, A.; Poblete, F. J.; Maestro, M. Ruthenium
arene derivatives with PN hemilabile ligands. P-C cleavage and
phosphine to phosphinate transformation. Organometallics 2004, 23,
5694-5706.
(36) Crystallographic data for the structures in this paper have been
deposited with the Cambridge Crystallographic Data Centre as
supplementary publications CCDC 604182-604186. Copies of the
data can be obtained, free of charge, on application to CCDC, 12
Union Road, Cambridge CB2 1EZ, U.K. (fax, +44 1223 336033;
e-mail, deposit@ccdc.cam.ac.uk).
(44) Duisenberg, A. J. M. Indexing in single-crystal diffractometry with
an obstinate list of reflections. J. Appl. Crystallogr. 1992, 25, 92-
96.
(45) CrysAlis CCD, version 1.170, and CrysAlis RED, version 1.170.;
Oxford Diffraction Ltd., Abingdon, Oxfordshire, U.K., 2003.
(46) Duisenberg, A. J. M.; Kroon-Batenburg, L. M. J.; Schreurs, A. M.
M. An intensity evaluation method: EVAL-14. J. Appl. Crystallogr.
2003, 36, 220-229.
(47) Sheldrick, G. M. SADABS. Program for Empirical Absorption
Correction of Area Detector Data; University of Go¨ttingen: Go¨t-
tingen, Germany, 1996.
(48) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.; Burla,
M. C.; Polidori, G.; Camalli, M. SIR92, a program for automatic
solution of crystal structures by direct methods. J. Appl. Crystallogr.
1994, 27, 435.
(37) Kiviniemi, S.; Nissinen, M.; Alaviuhkola, T.; Rissanen, K.; Pursi-
ainen, J. The complexation of tetraphenylborate with organic N-
heteroaromatic cations. J. Chem. Soc., Perkin Trans. 2 2001, 2364.
(38) Keppler, B. K.; Henn, M.; Juhl, U. M.; Berger, M. R.; Niebl, R.;
Wagner, F. E. New ruthenium complexes for the treatment of cancer.
Prog. Clin. Biochem. Med. 1989, 10, 41-69.
(49) Sheldrick, G. M. SHELXS97 and SHELXL97; University of Go¨ttin-
gen: Go¨ttingen, Germany, 1997.
(50) Farrugia, L. J. ORTEP-3 for Windows, a version of ORTEP-III with
a graphical user interface (GUI). J. Appl. Crystallogr. 1997, 30, 565.
(51) Nanni, P.; De Giovanni, C.; Lollini, P. L.; Nicoletti, G.; Prodi, G.
TS/A: a new metastasising cell line from BALB/c spontaneous
mammary adenocarcinoma. Clin. Exp. Metastasis 1983, 1, 373-385.
(52) Mosmann, T. Rapid colorimetric assay for cellular growth and
survival: application to proliferation and cytotoxicity assays. J.
Immunol. Methods 1983, 65, 55-63.
(53) Alley, M. C.; Scudiero, D. A.; Monks, A.; Hursey, M. L.; Czerwinski,
M. J.; Fine, D. L.; Abbott, B. J.; Mayo, J. G.; Shoemaker, R. H.;
Boyd, M. R. Feasibility of drug screening with panels of human tumor
cell lines using a microculture tetrazolium assay. Cancer Res. 1988,
48, 589-601.
(39) Yan, Y. K.; Melchart, M.; Habtemariam, A.; Sadler, P. J. Organo-
metallic chemistry, biology and medicine: ruthenium arene anticancer
complexes. Chem. Commun. 2005, 4764-4776.
(40) Aird, R. E.; Cummings, J.; Ritchie, A. A.; Muir, M.; Morris, R. E.;
Chen, H.; Sadler, P. J.; Jodrell, D. I. In vitro and in vivo activity and
cross resistance profiles of novel ruthenium(II) organometallic arene
complexes in human ovarian cancer. Br. J. Cancer 2002, 86, 1652-
1657.
(41) Bennett, M. A.; Huang, T.-N.; Matheson, T. W.; Smith, A. K. (η6-
Hexamethylbenzene)-ruthenium complexes. Inorg. Synth. 1982, 21,
74-78.
JM060495O