Synthesis, characterization, and DNA binding of new water-soluble cyclopentadienyl ruthenium(II) complexes incorporating phosphines

Article abstract of DOI:10.1021/ic051053q

The new water-soluble ruthenium(II) chiral complexes [RuCpX(L)(L′)] ⁿ⁺ (X = Cl, I. L = PPh₃; L′ = PTA, mPTA; L = L′ = PTA, mPTA) (PTA = 1,3,5-triaza-7-phosphaadamantane; mPTA = N-methyl-1,3,5-triaza-7-phosphaadamantane) have been syn

Full text of DOI:10.1021/ic051053q

Inorg. Chem. 2006, 45, 1289−1298
Synthesis, Characterization, and DNA Binding of New Water-Soluble
Cyclopentadienyl Ruthenium(II) Complexes Incorporating Phosphines
Antonio Romerosa,*,† Tatiana Campos-Malpartida,† Chaker Lidrissi,† Mustapha Saoud,†
Manuel Serrano-Ruiz,† Maurizio Peruzzini,‡ Jose Antonio Garrido-Ca´rdenas,§ and
Federico Garc´ıa-Maroto§
AÄ rea de Qu´ımica Inorga´nica, Facultad de Ciencias, UniVersidad de Almer´ıa, Almer´ıa, Spain,
Istituto di Chimica dei Composti Organometallici, CNR, Via Madonna del Piano, 10, 50019 Sesto
Fiorentino (FI), Italy, and AÄ rea de Bioqu´ımica, Facultad de Ciencias, UniVersidad de Almer´ıa,
Almer´ıa, Spain
Received June 27, 2005
+
The new water-soluble ruthenium(II) chiral complexes [RuCpX(L)(L
′
)]n (X
)
Cl, I. L
)
)
PPh3; L′ ) PTA, mPTA;
N-methyl-1,3,5-triaza-7-
L
)
L
′ ) PTA, mPTA) (PTA
)
1,3,5-triaza-7-phosphaadamantane; mPTA
phosphaadamantane) have been synthesized and characterized by NMR and IR spectroscopy and elemental analysis.
The salt mPTA(OSO2CF3) was also prepared and fully characterized by spectroscopic techniques. X-ray crystal
structures of [RuClCp(PPh3)(PTA)] (2), [RuCpI(PPh3)(PTA)] (3), and [RuCpI(mPTA)(PPh3)](OSO2CF3) (9) have been
determined. The binding properties toward DNA of the new hydrosoluble complexes have been studied using the
mobility shift assay. The ruthenium chloride complexes interact with DNA depending on the hydrosoluble phosphine
bonded to the metal, while the corresponding compounds with iodide, [RuCpI(PTA)2] (1), [RuCpI(PPh3)(PTA)] (3),
[RuCpI(mPTA)2](OSO2CF3)2 (6), and [RuCpI(mPTA)(PPh3)](OSO2CF3) (9), do not bind to DNA.
Introduction
transition metal complexes.2 These nucleobases behave as
effective ligands for a wide range of metal ions,1,2 adopting
different coordination modes as a function of the electronic
and steric properties of the additional donor groups coordi-
nated to the metal center. Our studies have been carried out
on both Pd and Pt complexes that are among the most
biologically active metals.1,2 Jointly with these studies, we
are involved in the synthesis of new water-soluble ruthenium
complexes that are useful for bringing about catalytic
reactions in water and biphasic conditions.3 These complexes
provide interesting solutions to most of the important
disadvantages of homogeneous catalysis in organic solvents.4
During the past decades great attention has been paid to
studying the interaction of several nucleobases with transition
metal fragments.1 In this wide area of chemistry, we have
contributed by studying the interaction of purines, which are
among the most important components of DNA, with
* To whom correspondence should be addressed. E-mail: romerosa@ual.es.
† AÄ rea de Qu´ımica Inorga´nica, Facultad de Ciencias, Universidad de
Almer´ıa.
‡ CNR.
§ AÄ rea de Bioqu´ımica, Facultad de Ciencias, Universidad de Almer´ıa.
(1) (a) Metal Ions in Biological Systems; Sigel A., Sigel H., Eds.; Marcel
Dekker: New York, 1996; Vol. 32. (b) Cohen, S. M.; Lippard, S. J.
Prog. Nucl. Acid. Res. Mol. Biol. 2001, 67, 93. (c) Schneider, A. G.;
Schmalle, H. W.; Arod, F.; Dubler, E. J. Inorg. Biochem. 2002, 89,
227. (d) Colonna, G.; Di Masi, N. G.; Marzilli, L. G.; Natile, G. Inorg.
Chem. 2003, 42, 997. (e) Sullivan, S. T.; Ciccarese, A.; Fanizzi, F.
P.; Marzilli, L. G. Inorg. Chem. 2000, 39, 836. (f) Dubler, E.; Schmalle,
H. W.; Arod, F.; Schneider, A. Acta Crystallogr., Sect. C 2002, 58,
m111. (g) Monjardet-Bas, V.; Elizondo-Riojas, M. A.; Chottard, J.
C.; Kozelka, J. Angew. Chem., Int. Ed. 2002, 41, 2998. (h) Sigel, R.
K. O.; Freisinger, E.; Abbate, M.; Lippert, B. Inorg. Chim. Acta 2002,
339, 355. (i) Roitzsch, M.; Rother, I. B.; Willermann, M.; Erxleben,
A.; Costisella, B.; Lippert, B. Inorg. Chem. 2002, 41, 5946. (j) Lueth,
M. S.; Freisinger, E.; Glahe, F.; Mueller, J.; Lippert, B. Inorg. Chem.
1998, 37, 3195. (k) Jansen, B. A. J.; Perez, J. M.; Pizarro, A.; Alonso,
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229.
(2) (a) Romerosa, A.; Bergamini, P.; Bertolasi, V.; Canella, A.; Cattabriga,
M.; Gavioli, G.; Man˜as, S.; Mantovani, N.; Pellacani, L. Inorg. Chem.
2004, 43, 905-913. (b) Romerosa, A.; Lo´pez-Magan˜a, C.; Saoud, M.;
Man˜as-Carpio, S. Eur. J. Inorg. Chem. 2003, 348. (c) Romerosa, A.;
Lo´pez-Magan˜a, C.; Saoud, M.; Man˜as, S.; Colacio, E.; Suarez-Varela,
J. Inorg. Chim. Acta 2000, 307, 125. (d) Romerosa, A.; Suarez-Varela,
J.; Hidalgo, M. A.; Avila-Roso´n, J. C.; Colacio, E. Inorg. Chem. 1997,
36, 3784. (e) Fillaut, J.-L.; de los Rios, I.; Masi, D.; Romerosa, A.;
Zanobini, F.; Peruzzini, M. Eur. J. Inorg. Chem. 2002, 935.
(3) (a) Saoud, M.; Romerosa, A.; Peruzzini, M. Organometallics 2000,
19, 4005. (b) Saoud, M.; Romerosa, A.; Man˜as-Carpio, S.; Gonsalvi,
L.; Peruzzini, M. Eur. J. Inorg. Chem. 2003, 1614. (c) Lidrissi, C.;
Romerosa, A.; Saoud, M.; Serano-Ruiz, M.; Gonsalvi, L.; Peruzzini,
M. Angew. Chem., Int. Ed. 2005, 44, 2568.
10.1021/ic051053q CCC: $33.50
Published on Web 01/05/2006
© 2006 American Chemical Society
Inorganic Chemistry, Vol. 45, No. 3, 2006 1289

Romerosa et al.
Noticeably, ruthenium complexes have shown important
biological activity and are becoming more and more impor-
tant in bioinorganic chemistry.5 Indeed, three main properties
make ruthenium compounds amenable to be investigated for
medicinal applications: (i) the excellent rate of ligand
exchange; (ii) the wide range of accessible oxidation states;
and (iii) the ability of ruthenium to mimic iron binding to a
variety of biological molecules. However, many of the
ruthenium complexes are barely soluble in aqueous solution,
a condition that has to be fulfilled to allow for both efficient
administration and transport through living organisms.
Solubility of ruthenium compounds has been increased by
using dialkyl sulfoxide derivatives, such as in [trans-RuCl4-
(DMSO)Im][ImH] (NAMI-A), which is now recognized as
the most successful ruthenium-based anticancer compound
and has recently entered clinical trials,6 and by using water-
soluble phosphines, which has provided access to interesting
hydrosoluble complexes.7 In particular, the extensive and
pioneering work by Sadler and co-workers on the antitumor
properties of organometallic piano-stool compounds8 has
shown that this class of complexes are effective antitumoral
agents and has shed some light on the mechanism ruling the
interaction between the biomolecule and ruthenium. Interest-
ingly, Ru(II) complexes are far more reactive toward DNA
than Ru(III) and Ru(IV)5 and it is therefore probable that
the anticancer activity shown by several Ru(III) complexes
would involve initial reduction to Ru(II). Moreover, strong
evidence has been accumulated, showing that metal-to-
protein interactions are also extremely important in promot-
ing the anticancer activity of ruthenium compounds and it
has been demonstrated that such interactions could occur with
ruthenium ions in either oxidation states.1,8
a pair of water-soluble piano-stool ruthenium complexes,9
which showed modest biological activity. Remarkably, this
activity is lower than that found for other piano-stool
ruthenium complexes containing PTA10 and therefore it
should be attributed to the other ligands bonded to the metal.
In keeping with this hypothesis, the recently reported piano-
stool complexes [RuCl2(PTA)([9]aneS3)] and [RuCl(PTA)2-
([9]aneS3)](OSO2CF3) ([9]aneS3 ) 1,4,7-trithiacyclononane)11
show comparable cytotoxic activity with [RuClCp*(PTA)2]9
and [RuCl2(p-cymene)(PTA)],10 suggesting a negligible role
of the cyclopentadienyl and p-cymene ligands in the biologi-
cal activity. The question of addressing the biological role
for the different donor ligands coordinated to ruthenium can
likely be accurately answered by planning a systematic study
on a wide family of RuCp compounds containing different
water-soluble phosphines. From such a study we could obtain
important information for the rational design of new DNA-
binding agents capable of recognizing specific sequences or
structures and henceforth modifying specific DNA functions.
Here, we address this study reporting on the synthesis and
the characterization of a series of water-soluble piano-stool
ruthenium complexes of general formula [RuCpX(L)(L′)]n+
(X ) Cl, I. L ) PPh3, L′ ) PTA, mPTA; L ) L′ ) PTA,
mPTA. PTA ) 1,3,5-triaza-7-phosphaadamantane; mPTA
) N-methyl-1,3,5-triaza-7-phosphaadamantane), sharing an
identical structural motif with different combinations of
water-soluble phosphines such as PTA (I) and N-alkylated-
PTA (II).12 In addition, we show that these complexes, stable
to both hydrolysis and oxygen, exhibit remarkable activity
toward DNA in the darkness that is clearly depending on
the nature and number of the donor ligands (water-soluble
phosphines and halogen).
Recently, we described the first water-soluble ruthenium
cyclopentadienyl complexes containing hydrosoluble phos-
phines coordinated to the metal, namely, [RuClCp′(PTA)2]
(Cp′ ) Cp, Cp*; PTA ) 1,3,5-triaza-7-phosphaadamantane),
Experimental Section
(4) Grubbs, R. H. In Aqueous Organometallic Chemistry and Catalysis;
Horva´th, I. T., Joo´, F., Eds.; NATO ASI Ser. 35; Kluwer Academic
Publishers: Dordrecht, The Netherlands, 1995; p 15.
General Procedures. All chemicals were reagent grade and,
unless otherwise stated, were used as received by commercial
suppliers. The solvents were all degassed and distilled according
to standard procedures.13 All reactions and manipulations were
routinely performed under a dry nitrogen atmosphere by using
standard Schlenk-tube techniques. The hydrosoluble phosphines
PTA14 and mPTA(I)15,16 and the complexes [RuClCp(PTA)2]9 and
(5) (a) Hotze, A. C. G.; van der Geer, E. P. L.; Caspers, S. E.; Kooijman,
H.; Spek, A. L.; Haasnoot, J. G.; Reedijk, J. Inorg. Chem. 2004, 43,
4935. (b) Reedijk, J. Proc. Natl. Acad. Sci. U.S.A. 2003, 100, 3611.
(c) Clarke, M. J. Coord. Chem. Rev. 2002, 232, 69. (d) Velders, A.
H.; Kooijman, H.; Spek, A. L.; Haasnoot, J. G.; de Vos, D.; Reedijk,
J. Inorg. Chem. 2000, 39, 2966. (e) Hotze, A. C. G.; Caspers, S. E.;
de Vos, D.; Kooijman, H.; Spek, A. L.; Flamigni, A.; Bacac, M.; Sava,
G.; Haasnoot, J. G.; Reedijk, J. J. Biol. Inorg. Chem. 2004, 9, 354.
(6) (a) Frausin, F.; Scarcia, V.; Cocchietto M.; Sava, G. J. Pharmacol.
Exp. Ther. 2005, 313, 227. (b) Serli, B.; Zangrando, E.; Gianferrara,
T.; Yellowlees L.; Alessio, E. Coord. Chem. ReV. 2003, 245, 73. (c)
Sava, G.; Gagliardi, R.; Bergamo, A.; Alessio, E.; Mestroni, G.
Anticancer Res. 1999, 19, 969.
(9) Akbayeva, D. N.; Gonsalvi, L.; Oberhauser, W.; Peruzzini, M.; Vizza,
F.; Bru¨ggeller, P.; Romerosa, A.; Sava, G.; Bergamo, A. Chem.
Commun. 2003, 264.
(10) Allardyce, C. S.; Dyson, P. J.; Ellis, D. J.; Heath, S. L. Chem. Commun.
2001, 1396.
(7) Dorcier, A.; Dyson, P. J.; Gossens, C.; Rothlisberger, U.; Scopelliti,
R.; Tavernelli, I. Organometallics 2005, 24, 2114 and references
therein.
(8) (a) Yan, Y. K.; Melchart, M.; Habtemariam, A.; Sadler, P. J. Chem.
Commun. 2005, 4764. (b) Chen, H.; Parkinson, J. A.; Parsons, S.;
Coxall, R. A.; Gould, R. O.; Sadler, P. J. J. Am. Chem. Soc. 2002,
124, 3064. (c) Wang, F.; Chen, H.; Parkinson, J. A.; del Socorro
Murdoch, P.; Sadler, P. Inorg. Chem. 2002, 41, 4509. (d) Wang, F.;
Bella, J.; Parkinson, J. A.; Sadler, P. J. J. Biol. Inorg. Chem. 2005,
10, 147.
(11) Serli, B.; Zangrando, E.; Gianferrara, T.; Scolaro, C.; Dyson, P. J.;
Bergamo, A.; Alessio, E. Eur. J. Inorg. Chem. 2005, 3423.
(12) For a review on PTA chemistry, see: Phillips, A. D.; Gonsalvi, L.;
Romerosa, A.; Vizza, F.; Peruzzini, M. Coord. Chem. ReV. 2004, 248,
955.
(13) Purification of Laboratory Chemicals, 3rd ed.; Perrin, D. D., Armarego,
W. L. F., Eds; Butterworth and Heinemann: Oxford, 1988.
(14) Daigle, D. J. Inorg. Synth. 1998, 32, 40.
(15) Aqueous-Phase Organometallic Catalysis; Cornils, B., Herrmann, W.
A., Eds.; Wiley-VCH: Weinheim, Germany, 1998.
1290 Inorganic Chemistry, Vol. 45, No. 3, 2006

Water-Soluble Cyclopentadienyl Ruthenium(II) Complexes
[RuClCp(PPh3)2]17 were prepared as described in the literature. CD3-
OD for NMR measurements (Cortec-Euriso-top) was dried over
vacuum-dried. Crystals good enough for X-ray diffraction were
obtained by slow evaporation from a CHCl3 solution. Yield: 0.04
g, 70%. S25°C < 0.1 mg/mL. Elemental analysis for C29H32N3IP2-
Ru (712.52): found, C 48.56, H 4.71, N 5.44%; calcd, C 48.89, H
4.53, N 5.90%. 1H NMR (CDCl3): δ (ppm) 3.54-4.08 (m,
CH2P(PTA), 6 H), 4.24-4.46 (m, CH2N(PTA), 6 H), 4.46 (s, Cp, 5
H), 7.34-7.59 (m, aromatic protons, 15 H). 13C{1H} NMR: δ
1
molecular sieves (0.4 nm). H and 13C{1H} NMR spectra were
recorded on a Bruker DRX300 spectrometer operating at 300.13
MHz (1H) and 75.47 MHz (13C), respectively. Peak positions are
relative to tetramethylsilane and were calibrated against the residual
solvent resonance (1H) or the deuterated solvent multiplet (13C).
31P{1H} and 19F{1H} NMR spectra were recorded on the same
instrument operating at 121.49 and 282.40 MHz, respectively.
Chemical shifts for 31P{1H} NMR were measured relative to
external 85% H3PO4 and for 19F{1H} NMR to CFCl3 with downfield
values taken as positive in both cases. Infrared spectra were recorded
as KBr disks using an FT-IR ATI Mattson Infinity Series. Elemental
analyses (C, H, N, S) were performed on a Fisons Instruments EA
1108 elemental analyzer.
1
(ppm) 57.16 (d, JCP ) 14.2, CH2P(PTA)), 73.04 (s, CH2N(PTA), 6
H), 79.13 (s, Cp), 127.77-139.09 (aromatic carbons). 31P{1H}
NMR: δ (ppm) -39.50 (d, 1JPP ) 43.28 Hz, PTA), 47.88 (d, PPh3).
Synthesis of mPTA(OSO2CF3) (4). MeOSO2CF3 (0.14 mL, 1.27
mmol) was added via a syringe to a stirred PTA (0.1 g, 0.64 mmol)
CHCl3 solution (10 mL). The white suspension which formed was
refluxed for 30 min and cooled at room temperature. The white
precipitate which separated was filtered, washed with CHCl3 (2 ×
1 mL), and air-dried. Yield: 0.0485 g, 23.7%. S25°C ) 240 mg/
mL. Elemental analysis for C8H15N3F3O3PS (321.25): found, C
29.70, H 4.72, N 12.86; S 9.56%; calcd, C 29.90, H 4.71, N 13.08,
S 9.96%. IR (KBr, cm-1): ν(OSO) 1264. 1H NMR (D2O): δ (ppm)
Synthesis of [RuCpI(PTA)2] (1). This compound was synthe-
sized by a slightly modified procedure to that described in the
literature.18 A solution of [RuClCp(PTA)2] (0.10 g, 0.14 mmol) in
15 mL of MeOH was reacted by KI (0.022 g, 0.13 mmol) at
refluxing temperature. After 1 h, the orange precipitated formed
was filtered while hot, washed with MeOH (2 × 5 mL), and
vacuum-dried. Yield: 0.08 g, 68%. S25°C ) 10 mg/mL. Elemental
analysis for C17H29N6P2RuI (607.38): found, C 33.31, H 5.03, N
13.53%; calcd, C 33.62, H 4.81, N 13.84%. 1H NMR (300.13 MHz,
20 °C, CDCl3): δ (ppm) 3.99-4.20 (m, CH2P(PTA), 12 H), 4.48-
2.67 (s, CH3N(mPTA), 3 H), 3.83 (ABPYY′X system, 2JH ) 15.0
AHB
2
4
4
Hz, J
) 14.1 Hz, J
) 0.4 Hz, J
HA,BP
HBHY(CH3NCH2P)
HBHY′(CH3NCH2P)
) 0.3 Hz, 4JH (NCH N) ) 1.5 Hz, NCH2P(mPTA), 4 H), 4.28 (AMPX
AHX
2
system, 2JH P ) 6.7 Hz, 4JH (NCH P) ) 0.4 Hz, 4JH
)
)
AHM
AHX(CH3NCH2N)
2
A
2
0.3 Hz, CH3NCH2P(mPTA), 2 H), 4.45 (ABMX system, JH
13.8 Hz, 4JH
NCH2N(mPTA), 2 H), 4.81 (ABMQX system, JH
AHB
4
) 1.5 Hz, JH H
) 0.5 Hz,
) 12.0 Hz,
AHM(NCH2P)
X(CH3NCH2N)
2
B
1
4.46 (m, CH2N(PTA), 12 H), 4.65 (s, Cp, 5 H). H NMR (D2O): δ
AHB
4
4JH
) 0.3 Hz, JH
) 0.3 Hz, JH H
)
4
(ppm) 3.91-4.10 (m, CH2P(PTA), 12 H), 4.48 (bs, CH2N(PTA), 12
AHM(CH3NCH2P)
AHQ(NCH2P)
X(NCH2N)
B
H), 4.75 (bs, Cp, 5 H). 13C{1H} NMR (75.47 MHz, 20 °C,
0.5 Hz, CH3NCH2N(mPTA), 4 H). 13C{1H} NMR: δ (ppm) 45.27
1
1
CDCl3): δ (ppm) 59.63 (t, JCP ) 8.6 Hz, CH2P(PTA)), 73.30 (s,
(d, JCP ) 21.4 Hz, NCH2P(mPTA)), 49.92 (s, CH3N(mPTA)), 56.45
CH2N(PTA)), 76.83 (s, Cp). 13C{1H} NMR (D2O): δ (ppm) 56.37
(t, 1JCP ) 8.6 Hz, CH2P(PTA)), 70.60 (s, CH2N(PTA)), 77.65 (s, Cp).
31P{1H} NMR (121.49, 20 °C, CDCl3): δ (ppm) -30.11 (s, PTA).
31P{1H} NMR (D2O): δ (ppm) -28.51 (s, PTA).
1
(d, JCP ) 33.6 Hz, CH3NCH2P(mPTA)), 69.10 (s, NCH2N(mPTA)),
1
80.01 (s, CH3NCH2N(mPTA)), 119.24 (q, JCF ) 316.8 Hz, OSO2-
CF3). 31P{1H} NMR: δ (ppm) -85.10 (s, mPTA). 19F{1H} NMR
(282.40, 20 °C, D2O): δ (ppm) -78.98 (s, OSO2CF3).
Synthesis of [RuClCp(PPh3)(PTA)] (2). Solid PTA (0.65 g,
4.24 mmol) was slowly added to a vigorously stirred solution of
[RuClCp(PPh3)2] (3.00 g, 4.13 mmol) in 65 mL of toluene. The
mixture was gradually heated to a boiling temperature and gently
refluxed for 2 h. After the solution was cooled to room temperature,
the yellow powder of [RuClCp(PPh3)(PTA)] (2) was collected by
filtration and washed with Et2O (2 × 3 mL). Crystals adequate for
X-ray determination were obtained by slow evaporation from a CH3-
Cl:n-hexane (1:1) solution. Yield: 2.30 g, 89%. S25°C ) 1.5 mg/
mL. Elemental analysis for C29H32N3ClP2Ru (621.06): found, C
55.93, H 5.31, N 6.57%; calcd, C 56.08, H 5.19, N 6.77%.
Elemental analysis for crystals C29H32ClN3P2Ru‚1CHCl3‚0.25H2O
(744.94): found, C 48.15, H 4.62, N 5.42%; calcd, C 48.37, H
4.53, N 5.64%. 1H NMR (CDCl3): δ (ppm) 3.73-4.01 (m,
PCH2(PTA), 6 H), 4.23-4.46 (m, NCH2(PTA), 6 H), 4.41 (s, Cp, 5
H), 7.32-7.64 (m, aromatic protons, 15 H). 13C{1H} NMR: δ (ppm)
55.37 (AXX′ system, 1JCPX ) 13.3 Hz, 1JCPx′ ) 2.0 Hz, NCH2P(PTA)),
Synthesis of [RuClCp(mPTA)2](OSO2CF3)2 (5). RuCl3‚xH2O
(0.03 g, 0.145 mmol) in 5 mL of EtOH and freshly cracked
cyclopentadiene (1 mL, 0.02 mmol) were added to a stirred solution
of mPTA(OSO2CF3) (0.1 g, 0.312 mmol) in 10 mL of EtOH. The
mixture was refluxed for 6 h, filtered through sintered glass while
hot, and then evaporated to dryness under vacuum. The crude
yellow solid was taken with 1 mL of EtOH and precipitated with
5 mL of Et2O. The yellow solid obtained was filtered, washed with
Et2O (2 × 1 mL), and vacuum-dried. Yield: 0.016 g, 12.9%. S25°C
) 80 mg/ mL. Elemental analysis for C21H35N6ClF6O6P2RuS2
(844.13): found, C 29.75, H 4.52, N 9.54, S 7.22%; calcd, C 29.88,
H 4.18, N 9.96, S 7.60%. IR (KBr, cm-1): ν(OSO) 1269. 1H NMR
(D2O): δ (ppm) 2.82 (s, CH3N(mPTA), 6 H), 3.92-4.16 (m,
CH2P(mPTA), 12 H), 4.19-4.98 (m, CH2N(mPTA), 12 H), 4.85 (s, Cp,
5 H). 13C{1H} NMR (D2O): δ (ppm) 49.30 (s, CH3N(mPTA)), 50.76
1
1
(bd, JCP ) 57.5 Hz, NCH2P(mPTA)), 57.99 (bd, JCP ) 58.0 Hz,
CH3NCH2P(mPTA)), 67.80 (bd, 2JCP ) 8.6 Hz, NCH2N(mPTA)), 80.29
1
1
1
73.19 (d, JCP ) 5.8 Hz, NCH2N(PTA)), 78.70 (t, JCP ) 2.1 Hz,
(s, CH3NCH2N(mPTA)), 80.36 (s, Cp), 119.54 (q, JCF ) 317.0 Hz,
Cp), 128.05-138.72 (m, aromatic carbons). 31P{1H} NMR: δ
OSO2CF3). 31P{1H} NMR (D2O): δ (ppm) -10.74 (s, mPTA). 19F-
1
{1H} NMR (D2O): δ (ppm) -78.84 (s, OSO2CF3).
(ppm) -34.96 (d, JPP ) 34.7, PTA), 48.16 (d, PPh3).
Synthesis of [RuCpI(PPh3)(PTA)] (3). An excess of solid KI
(0.12 g, 0.07 mmol) was added to a solution of 2 (0.03 g, 0.05
mmol) in 15 mL of MeOH and then kept at refluxing temperature
for 30 min. The orange precipitate obtained was filtered while hot,
washed with MeOH (2 × 5 mL) and EtOH (2 × 2 mL), and
Synthesis of [RuCpI(mPTA)2](OSO2CF3)2 (6). Solid NaI
(0.053 g, 0.35 mmol) was added to a solution of 5 (0.05 g, 0.059
mmol) in 10 mL of MeOH/H2O (1:1) and stirred at room
temperature for 15 min. The mixture was gradually heated to the
boiling temperature and then gently refluxed for 1 h. The resulting
red solution was filtered through Celite and the solvent evaporated
to leave a red yellowish solid which was taken with CHCl3 (3 mL).
The resulting solution was filtered and the solvent removed under
vacuum to give 6 as a yellowish red powder. Yield: 0.050 g, 90.2%.
S25°C ) 32 mg/mL. Elemental analysis for C21H35N6IF6O6P2RuS2
(16) Joo´, F.; Kovacs, J.; Katho, A.; Benyei, A. C.; Decuir, T.; Darensboug,
D. J. Inorg. Synth. 1998, 32, 2.
(17) Bruce, M. L.; Windsor, N. J. Aust. J. Chem. 1977, 30, 1601.
(18) Bolan˜o, S.; Gonsalvi, L.; Zanobini, F.; Vizza, F.; Bertolasi, V.;
Romerosa, A.; Peruzzini, M. J. Mol. Catal. A: Chem. 2004, 224, 61.
Inorganic Chemistry, Vol. 45, No. 3, 2006 1291

Romerosa et al.
(935.58): found, C 26.75, H 3.98, N 8.64, S 6.52%; calcd, C 26.96,
H 3.77, N 8.98, S 6.85%. IR (KBr, cm-1): ν(OSO) 1271. 1H NMR
(D2O): δ (ppm) 2.80 (s, CH3N(mPTA), 6 H), 3.80-4.20 (m,
CH2P(mPTA), 12 H), 4.34-5.12 (m, CH2N(mPTA), 12 H), 4.90 (s, Cp,
5 H). 13C{1H} NMR (D2O): δ (ppm) 49.32 (CH3N(mPTA)), 51.18
resulting red-orange mixture was filtered through Celite and the
solvent was completely evaporated. The red-orange solid was
washed with Et2O (2 × 5 mL) and vacuum-dried.
(C) The red solution obtained by refluxing for 1 h a solution of
7 (0.10 g, 0.26 mmol) and NaI (0.02 g, 0.27 mmol) in 5 mL of
MeOH was cooled and evaporated to 1 mL. Addition of 3 mL of
Et2O gave a reddish orange precipitate which was filtered, washed
with Et2O (2 × 1 mL), and vacuum-dried.
1
1
(bd, JCP ) 57.0 Hz, NCH2P(mPTA)), 58.1 (bd, JCP ) 51.9 Hz,
CH3NCH2P(mPTA)), 67.70 (bd, 2JCP ) 8.6 Hz, NCH2N(mPTA)), 80.11
1
(s, CH3NCH2N(mPTA)), 80.17 (s, Cp), 120.27 (q, JCF ) 318.1 Hz,
OSO2CF3). 31P{1H} NMR: δ (ppm) -15.02 (s, mPTA). 19F{1H}
NMR: δ (ppm) -79.02 (s, OSO2CF3).
Yield: 0.08 g, 34% (method A); 0.20 g, 89%. Elemental analysis
(taken on a crystalline sample obtained from method A) C31H35N3F3-
IO3P2RuS1‚2H2O (912.64): found, C 40.44, H 4.44, N 4.42, S
3.22%; calcd, C 40.80, H 4.31, N 4.60, S 3.51%. Elemental analysis
(taken on a powdered sample obtained from method B) C31H35-
N3O3F3IRuP2S1 (876.61): found, C 42.24, H 4.27, N 4.52, S 3.42%;
calcd, C 42.47, H 4.02, N 4.79, S 3.66%. IR (KBr, cm-1): ν(OSO)
1258. 1H NMR (CDCl3): δ (ppm) 2.78 (s, CH3N(mPTA), 3 H), 3.74-
4.12 (m, CH2P(mPTA), 6 H), 4.31-5.17 (m, CH2N(mPTA), 6 H), 4.68
(s, Cp, 5 H), 7.41-7.56 (aromatic protons, 15 H). 13C{1H} NMR:
Synthesis of [RuClCp(mPTA)(PPh3)](OSO2CF3) (7). Solid 4
(0.08 g, 0.28 mmol) was added to a stirred solution of [RuClCp-
(PPh3)2] (0.1 g, 0.14 mmol) in 5 mL of acetone and slowly warmed
to reflux which was maintained for 4 h. During this time 7 separated
out as a yellow-orange powder, which was collected by filtration
while hot, washed with acetone (2 × 2 mL), and vacuum-dried.
Yield: 0.077 g, 71%. S25°C ) 1.1 mg/mL. Elemental analysis for
C31H35N3ClF3O3P2RuS (785.16): found, C 47.24, H 4.52, N 5.12,
S 3.82%; calcd, C 47.42, H 4.49, N 5.35, S 4.08%. IR (KBr, cm-1):
1
δ (ppm) 48.91 (s, CH3N(mPTA)), 51.34 (d, JCP ) 15.8 Hz,
ν(OSO) 1251. 1H NMR (CD3OD): δ (ppm) 2.58 (bs, CH3N(mPTA)
3 H), 3.44-3.96 (m, CH2P(mPTA), 6 H), 4.07-4.36 (m, CH2N(mPTA)
,
,
NCH2P(mPTA)), 51.34 (d, 1JCP ) 15.8 Hz, CH3NCH2P(mPTA)), 59.27
(s, NCH2N(mPTA)), 69.59 (s, CH3NCH2N(mPTA)), 81.90 (s, Cp),
120.46 (q, 1JCF ) 319.76 Hz, OSO2CF3), 129.03-135.15 (aromatic
6 H), 4.59 (s, Cp, 5 H), 7.45-7.53 (m, aromatic protons, 15 H).
1H NMR (DMSO-d6): δ (ppm) 2.50 (bs, CH3N(mPTA), 3 H), 3.12-
3.77 (m, CH2P(mPTA), 6 H), 4.09-4.95 (m, CH2N(mPTA), 6 H), 4.54
(s, Cp, 5 H), 7.45-7.47 (m, aromatic protons, 15 H). 13C{1H} NMR
(DMSO-d6): δ (ppm) 48.87 (s, CH3N(mPTA)), 49.17 (d, 1JCP ) 12.7
1
carbons). 31P{1H} NMR: δ (ppm) -18.63 (d, JPP ) 41.5 Hz,
mPTA), 46.30 (d, PPh3). 19F{1H} NMR: δ (ppm) -78.35 (s, OSO2-
CF3).
Stability Tests for the Ruthenium Complexes [RuCpX(L)-
(L′)]n+ (X ) Cl, I. L) PPh3, L′ ) PTA, mPTA; L ) L′ ) PTA,
mPTA) toward H2O and O2. In a standard procedure, 0.01 g of
ruthenium complexes, but 7 and 9, were introduced into a 5 mm
NMR tube and dissolved in degassed CDCl3 (1.0 mL). The solution
was then cooled to ca. 0 °C and dry O2 was slowly bubbled
throughout the solution for 2 min via a long syringe needle. 31P-
{1H} NMR monitoring showed no change within 1 week. No
decomposition was also observed after 1 week, maintaining the
temperature at 40 °C. Due to poor solubility in CDCl3, the
complexes 7 and 9 were dissolved in CD3OD where they showed
a similar lack of reactivity toward O2.
A similar stability experiment performed in D2O showed that 1,
2, 5, 6, 7, and 9 did not decompose within 1 week at room
temperature. At 40 °C however decomposition was observed within
2 days. Compounds 3 and 8 were not soluble enough in water to
accomplish the above experiment. However, dissolving 0.02 g of
complexes 3 and 8 in 10 mL of aerated water causes decomposition
at 40 °C within 2 days (IR and NMR analysis) with the formation
of green-colored solutions likely containing paramagnetic ruthenium
species which prevented the recording of NMR spectra.
DNA Mobility Shift Assays. Reactions between DNA and the
ruthenium complexes were performed in a 20 µL final volume
containing 10 mM sodium phosphate buffer at physiological pH
7.0, 1 µg of the pBluescript-KSII plasmid (3 Kbp, from Stratagene),
and appropriate amounts of a freshly prepared solution of the Ru
complex in water, to achieve the desired metal-to-base pair
stoichiometry. Reaction mixtures were incubated for 14 h at 37 °C
in the dark. 10 µL samples were withdrawn and analyzed by
electrophoresis in 1% agarose gels freshly prepared in TAE buffer
(40 mM tris(hydroxymethyl)aminomethane, 20 mM sodium acetate,
1 mM EDTA, pH 8.0). Running was conducted in TAE buffer at
a constant voltage of 3 V/cm. DNA bands were visualized by
incubation of the gel with 1 µg/mL ethidium bromide in TAE buffer
for 30 min and photographed under UV light. For each active
compound we registered the Ri (ruthenium-to-base molar ratio)
value at which complete transformation of the supercoiled-to-
relaxed form of the plasmid was attained.
1
Hz, NCH2P(mPTA)), 51.97 (d, JCP ) 15.3 Hz, CH3NCH2P(mPTA)),
59.44 (s, NCH2N(mPTA)), 58.76 (s, CH3NCH2N(mPTA)), 79.3 (s, Cp),
121.08 (q, 1JCF ) 321.4 Hz, OSO2CF3), 128.54-134.03 (aromatic
carbons). 31P{1H} NMR (CD3OD): δ (ppm) -15.38 (d, 1JPP ) 43.9,
mPTA), 46.31 (d, PPh3). 31P{1H} NMR (DMSO-d6): δ (ppm)
1
-15.57 (d, JPP ) 43.3, mPTA), 47.27 (d, PPh3). 19F{1H} NMR
(CD3OD): δ (ppm) -80.11 (s, OSO2CF3). 19F{1H} NMR (DMSO-
d6): δ (ppm) -77.72.
Synthesis of [RuCpI(mPTA)(PPh3)]Cl (8). Solid [RuClCp-
(PPh3)2] (0.10 g, 0.14 mmol) was added to a solution of mPTA (I)
(0.16 g, 0.54 mmol) in 30 mL of 2-propanol. The resulting mixture
was stirred at refluxing temperature for 6 h. The orange precipitate
obtained was filtered while hot and dissolved in 2 mL of CHCl3.
Addition of 4 mL of Et2O gave an orange precipitate which was
filtered off, washed with Et2O (2 × 2 mL), and vacuum-dried.
Yield: 0.07 g, 70%. S25°C ) 0.4 mg/mL. Elemental analysis for
C30H35N3ClIP2Ru (763.00): found, C 46.82, H 4.94, N 5.21%;
calcd, C 47.23, H 4.62, N 5.51%. 1H NMR (CDCl3): δ (ppm) 3.00
(s, CH3N(mPTA), 3 H), 3.92-4.02 (m, CH2P(mPTA), 6 H), 4.71-5.56
(m, CH2N(mPTA), 6 H), 4.77 (s, Cp, 5 H), 7.28-7.56 (aromatic
protons, 15 H). 13C{1H} NMR (CDCl3): δ (ppm) 48.68 (s,
1
CH3N(mPTA)), 51.92 (d, JCP ) 15.8 Hz, NCH2P(mPTA)), 54.35 (d,
1JCP ) 15.3 Hz, CH3NCH2P(mPTA)), 63.16 (s, NCH2N(mPTA)), 69.65
(s, CH3NCH2N(mPTA)), 80.62 (s, Cp), 128.16-138.34 (aromatic
1
carbons). 31P{1H} NMR: δ (ppm) -18.32 (d, JPP ) 40.7 Hz,
mPTA), 46.37 (d, PPh3).
Synthesis of [RuCpI(mPTA)(PPh3)](OSO2CF3)‚2H2O (9‚
2H2O). This complex was prepared by three different procedures.
(A) Compound 8 (0.20 g, 0.26 mmol) and NH4OSO2CF3 (0.04
g, 0.26 mmol) were dissolved in 5 mL of CHCl3. The yellow
solution obtained was left at room temperature for 1 h. By slow
evaporation of the solvent, yellow crystals formed, which were
filtered and dried in the air. The crystals were of good quality
suitable for analysis by X-ray diffraction methods.
(B) To a solution of 8 (0.20 g, 0.26 mmol) in 20 mL of CHCl3
was added AgOSO2CF3 (0.07 g, 0.27 mmol), causing the formation
of a white precipitate. After 1 h at refluxing temperature the
1292 Inorganic Chemistry, Vol. 45, No. 3, 2006

Water-Soluble Cyclopentadienyl Ruthenium(II) Complexes
Table 1. Crystallographic Data
2‚CHCl3‚0.25H2O
3
9‚2H2O
formula
Mr
C30H32.5N3Cl4O0.25P2Ru
743.90
C29H32N3IP2Ru
712.49
C31H35N3F3IO5P2RuS
908.59
space group
cryst syst
a/Å
b/Å
c/Å
Pca21
orthorhombic
17.7148(7)
17.1794(7)
21.1886(9)
90
90
90
6448.3(5)
8
1.533
3020
9.43
28649
8343
0.0473
P21/n
P21/c
monoclinic
20.5735(7)
20.7874(7)
9.3689(3)
90
101.9200(10)
90
3920.4(2)
4
1.539
1808
13.75
17744
5583
0.0402
monoclinic
9.8910(4)
18.8230(7)
14.4419(6)
90
98.4990(10)
90
2659.24(18)
4
1.780
1416
18.96
12571
R/deg
â/deg
γ/deg
V/Å3
Z
Dc/g cm-3
F(000)
M(Mo KR)/cm-1
measd reflns
unique reflns
Rint
3817
0.0431
obsd reflns [I g 2σ(I)]
θmin-θmax/deg
hkl ranges
R(F2) (obsd reflns)
wR(F2) (all reflns)
no. of variables
GOF
7889
1.6-23
-19, 19; -19, 18; -23, 19
0.0630
0.1601
731
1.083
-0.834, 2.771
3115
4278
1.4-23
-22, 20; -23, 21; -10, 10
0.0613
0.1792
372
1.097
-0.755, 1.711
1.8-23
-10, 9; -20, 20; -11, 16
0.0287
0.0502
325
0.929
-0.402, 0.526
F
min, Fmax/e Å-3
Scheme 1
X-ray Structure Determinations. Data of compounds 2‚CHCl3‚
0.25H2O, 3, and 9‚2H2O were collected on a Bruker APEX CCD
diffractometer (XDIFRACT service of the University of Almer´ıa)
using graphite monochromated Mo KR radiation (λ ) 0.7107 Å)
at room temperature (295 K). The crystal parameters and other
experimental details of the data collections are summarized in Table
1. The structures were solved by direct methods SIR9219 and refined
by full-matrix least-squares methods with SHELXTL.20 The solvent
molecules CHCl3 and H2O for 2‚CHCl3‚0.25H2O, and the OSO2-
CF3 anion and H2O for 9‚2H2O, were found to be disordered and
refined isotropically. All the non-hydrogen non-disordered atoms
for the compounds were refined with anisotropic atomic displace-
ment parameters. All hydrogen atoms, except for disordered water
solvate molecules, for all crystal structures were included in
calculated positions and refined using a riding model. The 2‚CHCl3‚
0.25H2O crystal was found to be a twin and was refined generating
the indices of the twin components from the input reflection indices.
All calculations were performed using SHELXTL. Crystallographic
data (excluding structure factors) for the structures in this paper
and have been deposited with the Cambridge Crystallographic Data
Centre as supplementary publications nos. CCDC 272750-272752.
Copies of the data can be obtained, free of charge, on application
to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax, +44
1223 336033; e-mail, deposit@ccdc.cam.ac.uk).
NMR moves ca. 5 ppm highfield (1 δPTA ) -30.11 ppm;
[RuClCp(PTA)2] δPTA ) -25.65 ppm). This resonance is a
lot affected by the solvent and shifts downfield in polar
solvents [i.e., δPTA ) -28.51 (D2O); -30.11 (CDCl3)]. The
1H and 13C{1H} NMR of 1 (see Experimental Section) do
not significantly differ from those reported for [RuClCp-
(PTA)2].9
Complex 2 was obtained by replacing one PPh3 molecule
in [RuClCp(PPh3)2] with the water-soluble phosphine PTA
(Scheme 1) in refluxing toluene. Metathesis of chloride from
2 with excess KI in refluxing MeOH afforded 3 in high yield
after workup.
The selective substitution of a single molecule of PPh3
by one of PTA in the starting complex [RuClCp(PPh3)2]
giving 2 was clearly confirmed by the appearance in the 31P-
{1H} NMR of two doublets at 48.16 (PPh3, 1JPP ) 34.7 Hz)
and -34.96 (PTA, 1JPP ) 34.7). No trace of the disubstituted
PTA derivative [CpRuCl(PTA)2] was detected by NMR
analysis. Remarkably, the ruthenium atom in 2 is chiral,
being coordinated by four different ligands (Cp, Cl, PPh3,
and PTA) and is a racemate of two chiral complexes. This
situation was clearly confirmed by the analysis of the crystal
structure by X-ray diffractometry (see Figure 1).
On going from 2 to 3, the substitution of the chloride with
the iodide ligand shifts both doublets in the 31P{1H} NMR
to high field, the PTA resonance being more susceptible to
the Cl/I substitution (∆δPTA ) |δPTA(3) - δPTA(2)| ppm )
|-39.50 - (-34.96)| ppm ) 4.54 ppm; ∆δPPh3 ) |δPPh3(3)
- δPPh3(2)| ) |47.88 - 48.16| ppm ) 0.28 ppm) and parallels
(ca. 5 ppm) that observed for 1 in comparison to [RuClCp-
Results and Discussions
Synthesis and Characterization of New Hydrosoluble
Ruthenium PTA Complexes (1, 2, and 3). Complex
[RuCpI(PTA)2] (1) was straightforwardly obtained by meta-
thetical reaction of [RuClCp(PTA)2]9 with KI in refluxing
MeOH by a slight modification of the method previously
published by us.20 As a consequence of the chloride substitu-
tion by iodide, the singlet of the PTA ligand in the 31P{1H}
(19) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.; Burla,
M. C.; Polidori, G.; Camalli, M. J. Appl. Crystallogr. 1994, 27, 435.
(20) Sheldrick, G. M. SHELXTL version 6.14; Bruker-AXS: Madison, WI,
2003.
Inorganic Chemistry, Vol. 45, No. 3, 2006 1293

Romerosa et al.
Scheme 2
ruthenium complexes to obtain comparable information on
their reactivity toward DNA. To synthesize these compounds,
we required an mPTA salt, a soft and poorly coordinating
anion like triflate. N-Methylation of PTA by MeOSO2CF3
was straightforwardly accomplished in CHCl3, giving the
ammonium triflate salt mPTA(OSO2CF3) (4). The chemical
1
shift for the signals observed in the H and 13C{1H} NMR
spectrum in CDCl3 does not differ from those of mPTA (I),
-
apart from the OSO2CF3 quadruplet in the 13C{1H} NMR
spectrum. However, 4 is more water-soluble than mPTA (I)
(S25°C ) 240 mg/mL).
(PTA)2] (see above). Both 1H and 13C{1H} NMR completely
support the proposed formula of 3 which was also confirmed
by X-ray diffraction analysis (Figure 3).
A synthetic procedure similar to that used for [RuClCp-
(PPh3)2]17 was used to prepare [RuClCp(mPTA)2] (5). Thus,
freshly cracked dicyclopentadiene was directly reacted with
RuCl3‚xH2O and mPTA(OSO2CF3) in EtOH to yield 5,
although in very poor yield (Scheme 3). Chloride substitution
in 5 by iodide via reaction with NaI in refluxing MeOH/
H2O leads to complex 6 in very good yield.
The formula of complex 5 with two mPTA ligands is
clearly supported by 31P{1H} NMR in which a singlet at
-10.74 ppm (D2O) is observed. This chemical shift is ca. 5
ppm downfield shifted with respect to 7 (δmPTA (CD3OD) )
-15.38 ppm). The 1H NMR (D2O) agrees with the proposed
formula, showing the CH3N(mPTA) signal (δ ) 2.82 ppm)
slightly downfield shifted compared to that of 7 (δ(CD3OD)
) 2.58 ppm). A similar downfield shift is exhibited by the
Cp signal (δ(D2O) ) 4.85 ppm) in comparison to that of 7
(4.59 ppm). Metathesis of the chloride ligand with iodide
gives 6, which was characterized by NMR and IR spectros-
copy and elemental analysis.
Finally, the 1:1 reaction of 4 with [RuClCp(PPh3)2] in
acetone (Scheme 2) leads to the monosubstituted complex
[RuClCp(PPh3)(mPTA)](OSO2CF3) (7), which is practically
insoluble in organic solvents, such as CHCl3, scarcely soluble
in water (S25°C ) 1.1 mg/cm3), but soluble enough in acetone,
EtOH, and MeOH to allow for its NMR characterization.
As good quality crystals could not be obtained, complex 7
was characterized only by spectroscopic techniques and
elemental analysis. The 31P{1H} NMR recorded in CD3OD
shows a doublet at 46.31 ppm practically unchanged with
respect to 8 (46.37 ppm) and a second doublet at -15.38
ppm assigned to mPTA. The latter is ca. 3 ppm low field
shifted respective to the mPTA signal in 8 (-18.32 ppm).
This NMR behavior is in agreement with the general
tendency observed for these complexes: the substitution of
the chloride bonded to the metal by iodide causes PPh3 and
mPTA resonances to move to higher field. The coupling
constant between the phosphorus atoms for both compounds
8 (40.7 Hz) and 7 (43.3 Hz) are comparable, which further
supports the proposed structure for 7. The 1H NMR displays
the signals expected for mPTA, Cp, and PPh3 ligands in a
1:1:1 ratio. These resonances are similar to those found for
8 with only minimal differences observed in the N-methyl
(7 δ: 2.58 ppm; 8 δ: 3.00 ppm) and Cp singlets (7 δ: 4.59
ppm; 8 δ: 4.77 ppm) groups.
Synthesis and Characterization of New Hydrosoluble
Ruthenium mPTA+ Complexes (5, 6, 7, 8, and 9).
Interestingly, only single PPh3 replacement in [RuClCp-
(PPh3)2] was achieved by reaction with mPTA (I) in refluxing
2-propanol. Forcing the reaction conditions and increasing
the ratio of mPTA (I) with respect to the parent chloride
derivative did not afford the disubstituted mPTA complex
but yielded the iodine-coordinated salt [RuCpI(mPTA)-
(PPh3)]Cl (8) via metathetical reaction of the coordinated
chloride with the iodide counteranion of the N-methylated
phosphadamantane ligand. Scheme 2 illustrates this behavior.
The 31P{1H} NMR of 8 agrees with the substitution of one
PPh3 by one mPTA, showing a behavior similar to that
observed for the Cl/I pair 2/3. In the case at hand the signal
1
assigned to PPh3 exhibits a chemical shift (46.37 ppm, JPP
) 40.7 Hz) similar to that found for 2 and 3 whereas the
doublet due to the mPTA falls at a lower field (-18.32 ppm,
1JPP ) 40.7 Hz) in comparison with the chemical shift of
the PTA ligand in 2 and 3. Significant differences affect the
1H NMR spectrum of 8 in comparison with that of 2 and 3.
In particular, in 2 and 3 the NCH2N(PTA) protons show almost
identical δ values (2: 4.23-4.46 ppm; 3: 4.24-4.46 ppm),
whereas they move downfield (4.71-5.56 ppm) for 8. In
contrast, the Cp signal for 8 is shifted to lower field (4.77
ppm) than 2 and 3 (4.41 and 4.46 ppm).
Crystallization of 8 in CHCl3 in the presence of NH4OSO2-
CF3 gave crystals of [RuCpI(mPTA)(PPh3)](OSO2CF3) (9)
suitable for an X-ray diffraction study (see below). Complex
9 was also obtained by reaction of 7 with NaI in MeOH at
refluxing temperature but the best synthetic method was the
plane reaction of 8 with AgOSO2CF3 in CHCl3. The NMR
and IR spectra for 8 and 9 are essentially the same, the only
-
differences being due to the OSO2CF3 absorptions in the
IR spectrum and the presence of the CF3 quartet in the 13C-
{1H} NMR spectrum.
The crystal structure of the triflate salt 9 is in perfect
agreement with the formula proposed for 8 (Figure 4).
Inspection of the metrical data points out that the distances
and angles are similar to that observed for the series of Ru-
PPh3-PTA complexes described above, which in turn
suggests that both PTA and alkylated-PTA have similar cone
angles and induce comparable electronic effects to the metal.
The synthesis of the complexes [RuClCp(mPTA)(PPh3)]+,
[RuClCp(mPTA)2]2+, and [RuCpI(mPTA)2]2+ were success-
fully attempted in order to have in stock related hydrosoluble
Solubility in Water and Stability toward Oxygen of the
[RuCpX(L)(L′)]Y Complexes. The chemico-physical prop-
erties exhibited by the new ruthenium complexes described
1294 Inorganic Chemistry, Vol. 45, No. 3, 2006

Water-Soluble Cyclopentadienyl Ruthenium(II) Complexes
Scheme 3
in this article, particularly their marked solubility in water
and the 31P{1H} NMR data, agree with the proposed formulas
and confirm that the solid state structures are maintained in
water without any ligand replacement. As a common 31P-
{1H} NMR feature, the complexes show negative chemical
shifts for the PTA ligands which anyway fall always at higher
field than the mPTA. Coordinated PPh3 ligands resonate over
40 ppm in the expected region. The water solubility of the
complexes is predictable from the known hydrosolubility of
the PTA and mPTA phosphines,12 the number of water-
soluble phosphines (1 or 2) bonded to the metal, the type of
halogen (Cl or I) linked to the ruthenium, and last but not
least, the nature of the counteranion in charged complexes.
Generally, the water solubility of the complexes containing
two PTA ligands is higher than that including one PTA and
one PPh3 which, in turn, is higher than that of the complexes
with one mPTA and one PPh3. When iodide replaces
chloride, the solubility in water drops down. Finally, the
solubility of the cationic mPTA complexes increases by
replacing the chloride anion with triflate.
All the complexes are air-stable in water under aerobic
conditions within 1 day at both room temperature and 40
°C. The air stability of these complexes is in agreement with
previous observations by Sadler et al., suggesting that the
presence of arene molecules bonded to ruthenium favors the
stabilization of the Ru(II) species with respect to oxidized
Ru(III) derivatives.21 Therefore, for the complexes described
in this paper, the Cp ligand not only provides a lipophilic
side to the metal complex but also contributes to stabilization
of the ruthenium center in the +2 oxidation state. In addition,
no evidence for halide (Cl and I) replacement by water
(aquation) is observed. As mentioned above, the decomposi-
tion of these compounds likely affords unidentified green-
colored paramagnetic Ru(III) species which are silent by
NMR spectroscopy.
Figure 1. ORTEP view and atom numbering of compound 2. Only the
ipso carbons of the phenyl rings of PPh3 are shown. Hydrogen atoms have
been omitted for the sake of clarity.
ing three contiguous coordination positions, one Cl, one PPh3,
and one PTA. The coordination polyhedron about the metal
atom adopts a highly distorted pseudo-octahedral geometry
(P1-Ru-P1P ) 99.05(8)°; P2-Ru-P2P ) 98.92(9)°) likely
due to steric repulsion between the two phosphines. The two
independent molecules found in the asymmetric unit do not
show significant differences in their metrical parameters. The
overall geometry of the complex is very similar to that
observed for three-legged piano-stool complexes of the type
[MCpXL2] such as [RuClCp(PPh3)2].23 The Cp rings for the
two enantiomeric molecules are essentially planar, the biggest
separation being 0.0120 Å (C1) from the overall plan for
the Cp bonded to Ru1 and 0.0262 (C10) for the Cp bonded
to Ru2. The Ru-Cp(centroid) distances are for the two
molecules quite similar (Ru1-Cp(centroid) ) 1.845 Å; Ru2-
Cp(centroid) ) 1.837 Å) and comparable with that for [CpRuCl-
(PTA)2]24 (Ru-Cp(centroid) ) 1.844 Å) but somewhat shorter
than that in [RuClCp*(PTA)2] (1.861 Å).9 The Ru-P(PTA)
separations (Ru1-P1P ) 2.277(2) Å; Ru2-P2P ) 2.280(2)
Å) are somewhat larger than those of [RuClCp(PTA)2]
(average Ru-P ) 2.252 Å) and match the values found for
the few other X-ray authenticated Ru-PTA derivatives.12,25
The Ru-Cl distances (Ru1-Cl1 ) 2.448(2) Å, Ru2-Cl2
) 2.443(3) Å) for the two enantiomeric molecules are in
line with that of [RuClCp(PTA)2] (Ru-Cl ) 2.445 Å).
Despite the cone angle of PPh3 (ca. 147°) being greater than
Crystal Structure of [RuClCp(PPh3)(PTA)]‚CHCl3‚
0.25H2O (2‚CHCl3‚0.25H2O). An ORTEP22 view of 2‚
CHCl3‚0.25H2O is displayed in Figure 1 and the crystallo-
graphic data are given in Table 1. Crystals were obtained
by slow evaporation from a solution of 2 in CHCl3/n-hexane
(1:1).
The asymmetric unit in the cell contains one disordered
CHCl3, 0.25 water molecules, and two [RuClCp(PPh3)(PTA)]
neutral molecules which form enantiomeric pairs (Figure 1).
In both complex molecules the metal is coordinated with a
pseudo-octahedral geometry to one η5-Cp, formally occupy-
(23) Bruce, M. I.; Wong, F. S.; Skelton, B. W.; White, A. H. Dalton Trans.
1981, 1398.
(24) Frost, B. J.; Mebi, C. A. Organometallics 2004, 23, 5317.
(25) (a) Darensbourg, D. J.; Joo´, F.; Kannisto, M.; Katho, A.; Reibenspies,
J. H. Organometallics 1992, 11, 1990. (b) Darensbourg, D. J.; Joo´,
F.; Kannisto, M.; Katho, A.; Reibenspies, J. H.; Daigle, D. J. Inorg.
Chem. 1994, 33, 200. (c) Allardyce, C. S.; Dyson, P. J.; Ellis, D. J.;
Heath, S. L. Chem. Commun. 2001, 1396. (d) Darensbourg, D. J.;
Beckford, F. A.; Reibenspies, J. H. J. Cluster Sci. 2000, 11, 95.
(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. J. Med. Chem. 2001, 44, 3616.
(22) Johnson, C. K. ORTEP II. Report ORNL-5138; Oak Ridge National
Laboratory: Oak Ridge, TN, 1976.
Inorganic Chemistry, Vol. 45, No. 3, 2006 1295

Romerosa et al.
The asymmetric unit is constituted by one OSO2CF3 anion,
disordered by rotation around the C-S bond, two disordered
water molecules, and one enantiomeric [RuCpI(mPTA)-
(PPh3)]+ cation. The complex cation exhibits a pseudo-
octahedral geometry with Cp, iodide, PPh3, and mPTA
ligands coordinated to ruthenium. By actuation of the spatial
group symmetry (P21/c), the other enantiomeric cation is
generated (Figure 3) and, therefore, 4 is a racemate of the
two possible enantiomers obtained by distribution of the four
different ligands around the Ru atom. The octahedral
distortion around the metal (P1-Ru-P2 angle ) 100.12(8)°)
is more pronounced than that in 2, likely due to the larger
size of iodide which increases the repulsion between the
halide ligand and the other ruthenium coordinated ligands,
This result is intriguing as the cone angle for PTA and mPTA
is practically the same,12 which should have anticipated
similar intramolecular repulsions in related piano-stool
complexes.
The overall geometry of 4 is similar to that found for
[RuClCp*(PTA)2],9 [RuClCp(PTA)2],27 and complex 2. The
most important metrical characteristics are as follows: The
Cp ring is practically planar with the larger separation from
the overall Cp plane of only 0.0115 Å. The Ru-Cp(centroid)
distance (1.8563(7) Å) is similar to 3 (Ru-Cp(centroid) distance
) 1.852 Å), shorter than in [RuClCp*(PTA)2] (1.861 Å),9
and somewhat longer than in [RuClCp(PTA)2] (1.846 Å)27
and in 2 (Ru1-Cp(centroid) ) 1.845 Å; Ru2-Cp(centroid) ) 1.837
Å). The Ru-P(PTA) separation (Ru1-P1 ) 2.263(2) Å) is
shorter than that for 3 (Ru1-P1 ) 2.298(2) Å) but in line
with other Ru-PTA complexes.12,28 The Ru-I distance
(2.724 Å), slightly shorter than in 3 (Ru1-I1 distance )
2.751 (1) Å), is similar to the average value (2.711 Å) found
for the known [RuCpIL2] complex structures.27
Interaction of the Ru Complexes with DNA. Modifica-
tion of the electrophoretic mobility of plasmid DNA on
agarose gels is commonly taken as evidence for direct DNA-
metal interaction as has been shown in previous studies on
Pt and Ru compounds.28 Alteration of DNA structure, leading
to unwinding of the plasmid molecule, causes retardation in
the migration of supercoiled DNA (SC) and a slight increase
in the mobility of open circular DNA (OC) to a point
(coalescence point, CP) where both forms comigrate. We
have investigated the interaction of the new water-soluble
ruthenium complexes discussed above with SC DNA using
the shift mobility assay. The reactions between the ruthenium
complexes and SC plasmid DNA were performed in water-
containing phosphate buffer at pH 7.0 for 14 h at 37 °C in
darkness and then samples were analyzed by electrophoresis
in agarose-TAE gels. The reaction was performed in the
dark as a precaution against possible photochemical activa-
tion of the interaction process such as was observed for other
ruthenium complexes.29
Figure 2. ORTEP view and atom numbering of compound 3. Hydrogen
atoms have been omitted for the sake of clarity.
that of the PTA (ca. 102 °),26 the P-Ru-P(PTA) angle
(99.05(8)°) is quite similar to that for [RuClCp(PTA)2]
(P(PTA)-Ru-P(PTA) ) 96.85°).
A disordered water molecule has been found interspersed
in the lattice (Figure 1), clearly located between the N2P
and Cl2 atoms. Both N2P-O1W (2.748(2) Å) and Cl2-
O1W (3.144(2) Å) distances are shorter than those consider
to be hydrogen-bond interactions among these kinds of
atoms.26
The rest of the bond distances and angles are similar to
those found in the known Ru-PTA complexes and do not
deserve particular comments.12,27,28
Crystal Structure of [RuCpI(PPh3)(PTA)] (3). Solution
of 3 separated good quality crystals by slow crystallization
from CHCl3 solution. An ORTEP25 view of complex 3 is
displayed in Figure 2; the crystallographic data are provided
in Table 1.
The crystal structure is again constituted by a chiral
molecule with the metal coordinated to Cp, PPh3, PTA, and
one iodide ligand. The geometry of the complex is quite
similar to that of 2, discussed above. The Ru-Cp(centroid)
distance, 1.852 Å, is somewhat longer than those in both 2
(average Ru-Cp(centroid) ) 1.841 Å) and [RuClCp(PTA)2]
(Ru-Cp(centroid) ) 1.844 Å).27 The Ru-P(PTA) distance
(2.2979(11) Å) is much larger than those in 2 (Ru-Pave
)
2.278 Å). The Ru1-I1 separation (2.7514(4) Å) is larger
than the average value (2.711 Å) determined for the known
[RuCpIL2] complex structures.27 The coordination P1-Ru1-
P2 angle for 3 (97.31(4)°) is slightly shorter than that in 2
(average value P-Ru-P(PTA) ) 99.48°), which suggests
similar steric interactions in both complexes.
Crystal Structure of [RuCpI(mPTA)(PPh3)](OSO2CF3)‚
2H2O(9‚2H2O). Crystals of 4 satisfactory for X-ray diffrac-
tion analysis were obtained by slow evaporation from CHCl3
in the presence of NH4OSO2CF3. An ORTEP25 view is shown
in Figure 3; the crystallographic data are given in Table 1.
(26) (a) Tolman, C. A. J. Am. Chem. Soc. 1979, 92, 2956. (b) Delerno, J.
R.; Trefonas, L. M.; Darensbourg, M. Y.; Majeste, R. J. Inorg. Chem.
1976, 15, 816.
(27) (a) Yang, Y.; Abboud, K. A.; McElwee-White, L. Dalton Trans. 2003,
4288. (b) Pathak, D. D.; Hutton, A. T.; Hyde, J.; Walkden, A.; White,
C. J. Organomet. Chem. 2000, 606, 188. (c) Katayama, T.; Mat-
sushima, Y.; Onitsuka, K.; Takahashi, S. Chem. Commun. 2000, 2337.
(d) Duraczynska, D.; Nelson, J. H. Dalton Trans. 2003, 449.
(28) Singh, T. N.; Turro, C. Inorg. Chem. 2004, 43, 7260.
Retardation of SC DNA was observed for the chloro
complexes [RuClCp(PTA)2] (CP at Ri ) 13.3; Figure 4 panel
(29) (a) Schilden, K. v. d.; Garcia, F.; Kooijman, H.; Spek, A. L.; Haasnoot,
J. G.; Reedijk, J. Angew. Chem., Int. Ed. 2004, 43, 5668. (b) Fu, P.
K.-L.; Bradley, P. M.; Loyen, D. v.; Du¨rr, H.; Bossmann, S. H.; Turro,
C. Inorg. Chem. 2002, 41, 3808.
1296 Inorganic Chemistry, Vol. 45, No. 3, 2006

Water-Soluble Cyclopentadienyl Ruthenium(II) Complexes
Figure 3. ORTEP view and atom numbering of compound 9. Hydrogen atoms have been omitted for the sake of clarity.
As replacement of the halide ligand with water was not
observed for any of the ruthenium complexes during 24 h at
40 °C and the reactions with SC DNA were performed in
darkness, we are confident that the unchanged ruthenium
complexes are the DNA active species. Remarkably, no DNA
activity was observed with the iodide complexes 1, 3, and
9, a fact indicating that the Ru-I bond is likely more robust
than Ru-Cl and cannot be replaced by N-nucleophiles from
DNA.
Although the N7 binding site of guanine, the most
electron-rich site on DNA, is known to be the privileged
target for both Ru(II) and Ru(III) metal complexes, many
reported ruthenium derivatives do not selectively interact with
nucleobases and act as intra- or interstrand cross-linking
agents binding more than one reactive coordination site.30
In the case at hand, it is reasonable that the interaction of
the water-soluble ruthenium complexes here described takes
place via removal of the coordinated chloride and coordina-
tion of the G nucleobase via N7. A similar situation was
indeed observed by Sadler et al. during a study of the reaction
of [{(η6-p-cymene)RuCl(µ-Cl)}2] with lysozime after chlo-
ride removal with silver triflate.31 X-ray diffraction analysis
showed that the three-legged piano-stool arene [(η6-p-
cymene)RuCl2]+ unit binds the Nꢀ of the imidazole ring of
the unique histidine residue (His15) in the lysozyme protein.
In the same paper, it was also reported that the interaction
of[(η6-p-cymene)RuCl(en)](PF6)withDNA14-merd(A1T2A3-
C4A5T6G7G8T9A10C11A12T13A14) in aqueous solution occurs
via chloride substitution and N7 coordination of guanine to
ruthenium.
Figure 4. DNA mobility shift assay for the water-soluble ruthenium
complexes. Plasmid DNA was incubated with [RuClCp(PTA)2] (panel A),
[RuCpI(PTA)2] (1) (panel B), [RuClCp(PPh3)(PTA)] (2) (panel C), [RuCpI-
(PPh3)(PTA)] (3) (panel D), [RuClCp(mPTA)2](OSO2CF3)2 (5) (panel E),
[RuCpI(mPTA)2](OSO2CF3)2 (6) (panel F), [RuClCp(mPTA)(PPh3)](OSO2-
CF3) (7) (panel G), and [RuCpI(mPTA)(PPh3)](OSO2CF3)2 (9) (panel H).
Ri values (Ru/base molar ratio) in the different assays were as follows: 0,
5.3, 8.0, 10.7, 13.3, 16.0, 21.3, 26.7 (lanes 1-8 of panel A); 0, 5.3, 8.0,
10.7, 13.3, 16.0, 21.3, 26.7, 32.0 (1-9 panel B); 0, 2, 4, 5, 6, 7, 8, 10, 11
(1-9 panel C); 0, 2, 4, 6, 8, 10, 12, 15 (1-9 panels D and F); 0, 0.4, 0.8,
1.2, 1.6, 2, 2.4, 3 (1-8 panel E); 0, 0.33, 0.66, 1.0, 1.3, 1.7, 2.0, 2.5 (1-8
panels G and H).
Complexes with anticancer activity of the type [(η6-arene)-
RuCl(en)]+ are highly selective in their recognition of binding
sites on nucleosides and nucleotides.32 This arises not only
from the differences in basicity between the possible binding
A), [RuClCp(PPh3)(PTA)] (2) (CP at Ri ) 5.0; Figure 4
panel C), [RuClCp(mPTA)2](OSO2CF3)2 (CP at Ri ) 1.2;
Figure 4, panel E), and [RuClCp(mPTA)(PPh3)](OSO2CF3)
(CP at Ri ) 1.3; Figure 4, panel G). No interaction between
the iodide complexes (1, 3, 6, and 9) and SC DNA was
observed (Figures 4, panels B, D, F, and H).
(30) Clarke, M. J.; Zhu, F.; Frasca, D. R. Chem. ReV. 1999, 99, 2511.
(31) McNae, I. W.; Fishburne, K.; Mabtemariam, A.; Hunter, T. M.;
Melchart, M.; Wang, F.; Walkinshaw, M. D.; Sadler, P. J. Chem.
Commun. 2004, 1786.
(32) Chen, H.; Parkinson, J. A.; Morris, R. E.; Sadler, P. J. J. Am. Chem.
Soc. 2003, 125, 173.
Inorganic Chemistry, Vol. 45, No. 3, 2006 1297

Romerosa et al.
sites but also from the demanding constraints imposed on
the reactive monofunctional site in these pseudo-octahedral
“piano-stool” Ru(II) arene complexes. By an appropriate
choice of the arene coligand it has been possible to achieve
a high degree of selectivity via kinetic effects due to π-π
arene-base stacking interactions (intercalation).
(1); X ) Cl, L ) PPh3, L′ ) PTA, Q ) 0, (2); X ) I, L )
PPh3, L′ ) PTA, Q ) 0 (3); X ) Cl, L, L′ ) mPTA, Q )
(OSO2CF3)2, (5); X ) I, L, L′ ) mPTA, Q ) (OSO2CF3)2,
(6); X ) Cl, L ) PPh3, L′ ) mPTA, Q ) OSO2CF3, (7); X
) Cl, L ) PPh3, L′ ) mPTA, Q ) Cl-, (8); X ) I, L )
PPh3, L′ ) mPTA, Q ) OSO2CF3, (9)) (PTA ) 1,3,5-triaza-
7-phosphaadamantane; mPTA ) methyl-1,3,5-triaza-7-phos-
phaadamantane) was synthesized and characterized. The
X-ray crystal structures for 2, 3, and 9 have been determined,
showing the expected piano-stool structures of a racemic
mixture of the two possible enantiomers. The complexes are
air-stable in both solid state and solution and maintain their
solid state structure in water solution where no significant
halide substitution is observed. The chloride derivatives
actively destabilize the duplex SC DNA structure in the dark
while the comparable iodides compounds are inactive. This
result suggests that the interaction between the [RuClCp-
(L)(L′)]Q complexes and SC DNA occurs via chloride
substitution by a DNA constituent, resulting in the formation
of a chemical bond between ruthenium and a DNA base.
The DNA activity further depends on the water-soluble
phosphine coordinated to the metal, suggesting that modi-
fication of DNA by the water-soluble {RuClCp} species
might be achieved by an adequate choice of the hydrosoluble
phosphines bonded to the metal. Therefore, the study of the
DNA activity of other components of this family of
complexes could provide information good enough for the
rational design of new hydrosoluble DNA-binding agents
based on the {RuClCp} structural motif and capable of
recognizing specific sequences or structures of DNA and/or
modifying specific DNA functions. The final scope of this
work is to better understand the interaction of water-soluble
ruthenium species with DNA in view also of potential
application of this chemistry in drug design.
The interaction of the novel chloride ruthenium complexes
2, 5, 7, and [CpRuCl(PTA)2] with SC DNA is strictly
dependent on the water-soluble phosphines bonded to the
metal. The Ri values obtained at the coalescence point
indicate that either methylation of the PTA or the substitution
of PTA by PPh3 increase the biological activity toward SC
DNA. As the electronic and steric properties of PTA and
mPTA are quite comparable,12 it is hard to put down the
observed differences in biological activity to only electronic
and steric effects. A similar behavior was observed for Pt
thiosalicylate complexes, [Pt(SC6H4COO)(L)] (L ) PTA or
PPh3), where the PPh3 derivative exhibits higher antitumor
activity toward leukemia P388 cells.33 Similarly, complexes
containing PPh3 such as [Pt(PPh3)2(µ-N,S-8-TT)]2, cis-[PtCl-
(PPh3)2(8-MTT)], cis-[Pt(PPh3)2(8-MTT)2], and cis-[Pt(PPh3)2-
(8-MTT)(8-TTH)] are stronger inhibitors of cisplatin-resistant
SKOV3 cell line than analogous complexes containing PTA
such as [Pt(PTA)2(µ-S,N-8-TT)]2, cis-[PtCl(PTA)2(8-MTT)],
and cis-[Pt(PTA)2(8-MTT)2] (8-TTH2 ) 8-thiotheophylline;
8-MTTH ) 8-methylthiotheophylline).2 Complex 9, contain-
ing both PPh3 and mPTA ligands, shows activity toward SC
DNA similar to 7, which contains two mPTA ligands, but
higher than [RuClCp(PTA)2] where only PTA are present.
Therefore, we may conclude that coordination of either
mPTA or PPh3 to ruthenium increases the activity of the
{RuClCp} unit toward SC DNA. All these results, taken
altogether, suggest that the relatively modest DNA activity
of the PTA complexes7,9,10 could be interpreted with the
basicity of the phosphadamantane cage which at the physi-
ological pH value may be easily protonated at the nitrogen
atom. The presence in transition metal PTA complexes of
protonated PTA ligands may well account for the docu-
mented biological effects likely due to the formation of
hydrogen-bonding interactions with different nucleophiles in
biological systems.
Acknowledgment. Authors thank PAI (Junta de Andalu-
c´ıa, FQM-317) and the MCYT (Spain) for the project
PPQ2003-0133. This work was supported by EC through
the MCRTN program AQUACHEM (MRTN-CT-2003-
503864) and the COST Actions D17 and D29. Miss Tatiana
Campos-Malpartida thanks MAE-AECI for a predoctoral
fellowship supporting her stay in Almeria.
Conclusions
Supporting Information Available: X-ray crystallographic files
in CIF format for the structure determination of compounds
2‚CHCl3‚0.25H2O, 3, and 9‚2H2O. This material is available free
of charge via the Internet at http://pubs.acs.org.
A family of new water-soluble ruthenium(II) chiral
complexes [RuCpX(L)(L′)]Q (X ) I, L, L′ ) PTA, Q ) 0,
(33) McCaffrey, L. J.; Henderson, W.; Nicholson, B. K.; Mackay, J. E.;
Dinger, M. B. Dalton Trans. 1997, 2577.
IC051053Q
1298 Inorganic Chemistry, Vol. 45, No. 3, 2006