New dinuclear Ru2(CO)4 sawhorse-type complexes containing bridging carboxylato ligands

Article abstract of DOI:10.1002/zaac.200800385

The thermal reaction of Ru₃(CO)₁₂ with ethacrynic acid, 4-[bis(2-chlorethyl)amino]benzenebutanoic acid (chlorambucil), or 4-phenylbutyric acid in refluxing solvents, followed by addition of two-electron donor ligands (L), gives the d

Full text of DOI:10.1002/zaac.200800385

ARTICLE
DOI: 10.1002/zaac.200800385
New Dinuclear Ru2(CO)4 Sawhorse-Type Complexes Containing Bridging
Carboxylato Ligands
Mathieu Auzias,[a] Johan Mattsson,[a] Bruno Therrien,[a] and Georg Süss-Fink*[a]
Keywords: Carbonyl ligands; Carboxylato bridges; Dinuclear complexes; Ruthenium
Abstract. The thermal reaction of Ru3(CO)12 with ethacrynic acid,
4-[bis(2-chlorethyl)amino]benzenebutanoic acid (chlorambucil), or C5H5N; 6: R ϭ C3H6-C6H5, L ϭ PPh3). The single-crystal struc-
4-phenylbutyric acid in refluxing solvents, followed by addition of ture analyses of 2, 3, 5 and 6 reveal a dinuclear Ru2(CO)4 sawhorse
C3H6-C6H4-N(C2H4-Cl)2, L ϭ PPh3; 5: R ϭ C3H6-C6H5, L ϭ
two-electron donor ligands (L), gives the diruthenium complexes structure, the diruthenium backbone being bridged by the car-
Ru2(CO)4(O2CR)2L2 (1: R ϭ CH2O-C6H2Cl2-COC(CH2)C2H5, boxylato ligands, while the two L ligands occupy the axial positions
L ϭ C5H5N; 2: R ϭ CH2O-C6H2Cl2-COC(CH2)C2H5, L ϭ of the diruthenium unit.
PPh3; 3: R ϭ C3H6-C6H4-N(C2H4-Cl)2, L ϭ C5H5N; 4: R ϭ
trogen prior to use. All reagents were purchased either from Ald-
rich or Fluka and used as received. Dodecacarbonyltriruthenium
Introduction
was prepared according to published method [8]. The 1H, 13C{1H}
and 31P{1H} NMR spectra were recorded on a Bruker AMX 400
spectrometer using the residual protonated solvent as internal
standard. Infrared spectra were recorded on a Perkin-Elmer FT-IR
1720X spectrometer (4000-400 cmϪ1). Electro-spray mass spectra
were obtained in positive-ion mode with an LCQ Finnigan mass
spectrometer.
Sawhorse-type diruthenium complexes are well-known
since 1969, when J. Lewis and co-workers reported their
formation by refluxing Ru3(CO)12 in the corresponding car-
boxylic acid and the depolymerisation of the materials ob-
tained in coordinating solvents to give dinuclear complexes
of the type Ru2(CO)4(O2CR)2L2 (R ϭ H, CH3, C2H5,
C9H19; L ϭ C5H5N, AsPh3, PPh3), L being a two-electron
donor ligand [1]. Later, by a single-crystal X-ray structure
analysis of Ru2(CO)4(O2CR)2L2 (R ϭ C4H9; L ϭ PBut3),
these complexes have been shown to have a Ru2(CO)4 back-
bone in a sawhorse-type arrangement with two μ2-η2-
carboxylato bridges and two axial ligands [2]. Since their
discovery, a considerable number of such sawhorse-type di-
ruthenium complexes with carboxylato bridges have been
synthesized [3], and used in various fields as well as catalysis
[4, 5, 6] or to synthesize metallo-mesomorphic materials [7].
Herein, we report the synthesis and characterization of
six new Ru2(CO)4 sawhorse-type complexes containing car-
boxylato ligands, some of which with biologically active
substituents. The single-crystal structure analysis of four
representative complexes is presented as well.
Synthesis of 1؊6
A solution of Ru3(CO)12 (200 mg, 0.32 mmol) and the correspond-
ing acid (285 mg, 0.94 mmol for ethacrynic acid 1Ϫ2; 288 mg,
0.94 mmol for chlorambucil 3Ϫ4; 154 mg, 0.94 mmol for 4-phenyl-
1-butyric acid 5Ϫ6) in dry tetrahydrofuran (30 mL) was heated to
120 °C in a pressure Schlenk tube for 18 h. Then the solvent was
evaporated to give a brown residue which was dissolved in tetra-
hydrofuran and the appropriate ligand L (0.94 mmol) (1, 3, 5, L ϭ
C5H5N; 2, 4, 6, L ϭ PPh3) was added. The solution was stirred at
room temperature for two hours, then the solution was evaporated
and the product isolated from the residue by crystallization from
a tetrahydrofuran/hexane or dichloromethane/hexane mixture. The
products were purified by column chromatography on silica gel
using dichloromethane as eluent. Complexes 1Ϫ6 were obtained as
yellow crystalline powders which are stable up to 200 °C.
Experimental Section
Ru2(CO)4{O2CCH2O-C6H2Cl2-COC(CH2)C2H5}2(C5H5N)2
Yield: 68 %, 344 mg, 0.32 mmol.
(1).
General Remarks
All manipulations were carried out by routine under nitrogen at-
mosphere. Organic solvents were degassed and saturated with ni-
1H NMR (400 MHz, CDCl3): δ ϭ 8.34 (m, 4H, CHpyr), 7.81 (t, 2H, CHpyr
3J ϭ 7.6 Hz), 7.32 (m, 4H, CHpyr), 7.10 (d, 2H, CHaro 3J ϭ 8.6 Hz), 7.04
(d, 2H, CHaro
3J ϭ 8.6 Hz), 5.90 (s, 2H, CH2ϭC), 5.48 (s, 2H, CH2ϭC),
,
,
,
4.72 (s, 4H, CH2COO), 2.46 (q, 4H, CH2CH3, 3J ϭ 7.4 Hz), 1.15 (t, 6H,
CH3, 3J ϭ 7.4 Hz). 13C{1H} NMR (100 MHz, CDCl3): δ ϭ 206.44 (CO),
195.70 (2C, CϭO), 185.78 (COO), 157.17, 156.88 (C-Cl), 151.06 (C-O),
150.22 (C5H5N), 137.53 (C5H5N), 129.24 (CH2), 125.34 (C5H5N), 111.49
(CH3), 68.60 (CH2), 46.54 (CH), 26.61 (CH2). IR (CaF2, CH2Cl2): ν(CO)
2030 vs, 1978 m, 1947 vs, ν(OCO) 1613 m, 1585 m cmϪ1. ESI-MS: m/z ϭ
941.79 [M-C5H5N-2COϩH]ϩ.
* Prof. G. Süss-Fink
Fax: ϩ41-3271-82511
E-Mail: georg.suess-fink@unine.ch
´
ˆ
[a] Institut de Chimie, Universite de Neuchatel
ˆ
Avenue de Bellevaux 51, CP 158, 2009 Neuchatel, Switzerland
Z. Anorg. Allg. Chem. 2009, 635, 115Ϫ119
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
115

M. Auzias, J. Mattsson, B. Therrien, G. Süss-Fink
ARTICLE
Ru2(CO)4{O2CCH2O-C6H2Cl2-COC(CH2)C2H5}2(PPh3)2
Yield: 39 %, 260 mg, 0.180 mmol.
(2). tion, a CH2Cl2 solution (20 mL) of the appropriate ligand L
(0.515 mmol) C5H5N (5) or PPh3 (6) was added. Then the solution
1H NMR (400 MHz, (CD3)2CO): δ ϭ 7.61-7.30 (m, 30H, CHaro), 7.07 (d,
was stirred at room temperature for two hours. The volume of the
solvent was then reduced and the product was precipitated by ad-
dition of hexane. The product was obtained as a yellow powder.
Yields: 67 % (5) and 69 % (6).
2H, CHaro, ,
3J ϭ 8.6 Hz), 7.10 (d, 2H, CHaro 3J ϭ 8.6 Hz), 5.95 (s, 2H,
CH2ϭC), 5.38 (s, 2H, CH2ϭC), 4.45 (s, 2H, CH2COO), 2.43 (q, 4H,
CH2CH3, 3J ϭ 7.4 Hz), 1.10 (t, 6H, CH3, 3J ϭ 7.4 Hz). 13C{1H} NMR
(100 MHz, (CD3)2CO): δ ϭ 205.13 (CO), 195.70 (CϭO), 183.90 (COO),
157.19, 156.79 (C-Cl), 151.06 (C-O), 144.80, 139.20, 134.71, 134.50, 134.45,
134.39, 133.81, 133.65, 133.60, 131.06, 129.43, 129.38, 129.34 (CHaro), 129.24
(CH2), 123.29, 122.78 (CHaro), 111.49 (CH3), 68.60 (CH2), 47.06 (CH), 26.61
(CH2). 31P{1H} NMR (161 MHz, (CD3)2CO): δ ϭ 12.68. IR (CaF2, CH2Cl2):
ν(CO) 2028 vs, 1984 m, 1956 vs, ν(OCO) 1606 m, 1586 cmϪ1. ESI-MS: m/z ϭ
1443.02 [MϩH]ϩ, 1466.99 [M-2COϩNaϩ(CH3)2CO]ϩ.
X-ray Crystallographic Study
Yellow crystals of 2, 3, 5 and 6 were mounted at 203 K on a Stoe
Image Plate Diffraction system equipped with a φ circle goni-
ometer, using Mo-Kα graphite monochromated radiation (λ ϭ
˚
Ru2(CO)4{O2CC3H6-C6H4-N(C2H4-Cl)2}2(C5H5N)2 (3). Yield:
81 %, 412 mg, 0.381 mmol.
0.71073 A) with φ range 0-200°. The structures were solved by di-
rect methods using the program SHELXS-97 [9]. Refinement and
all further calculations were carried out using SHELXL-97 [10].
The H-atoms were included in calculated positions and treated as
riding atoms using the SHELXL default parameters. The non-H
atoms were refined anisotropically, using weighted full-matrix least-
square on F2.
1H NMR (400 MHz, CDCl3): δ ϭ 8.81-8.83 (m, 4H, C5H5N), 7.87-7.92 (m,
2H, C5H5N), 7.44-7.48 (m, 4H, C5H5N), 6.98 (d, 4H, C6H4, 3J ϭ 8.7 Hz),
6.58 (d, 4H, C6H4, 3J ϭ 8.7 Hz), 3.63-3.75 (m, 16H, N(CH2)2Cl), 2.49 (t,
4H, (CH2)2CH2, 3J ϭ 7.2 Hz), 2.36 (t, 4H, (CH2)2CH2, 3J ϭ 7.2 Hz), 1.81-
1.92 (m, 4H, CH2CH2CH2). 13C{1H} NMR (100 MHz, CDCl3): δ ϭ 206.64
(CO), 187.08 (COO), 152.31 (C5H5N), 144.57 (CHaro), 137.83 (C5H5N),
131.67 (CHaro), 130.08 (CH), 125.34 (C5H5N), 112.44 (CH), 54.01, 40.99,
36.72, 34.39, 28.53 (CH2). IR (CaF2, CH2Cl2): ν(CO) 2023 vs, 1971 m,
1939 vs, ν(OCO) 1582 m, 1568 m cmϪ1. ESI-MS: m/z ϭ 1082.02 [MϩH]ϩ,
1002.89 [M-C5H5NϩH]ϩ.
¯
Crystal data for 2; C66H52Cl4O12P2Ru2, triclinic space group P1
(No. 2), cell parameters a ϭ 10.1138(9), b ϭ 15.4929(13), c ϭ
˚
21.1252(17) A, Ͱ ϭ 91.972(10), β ϭ 96.308(10), γ ϭ 108.582(9)°,
3
V ϭ 3110.1(5) A , Z ϭ 2, Dc ϭ 1.541 g cmϪ3, F(000) 1460, 11372
˚
Ru2(CO)4{O2CC3H6-C6H4-N(C2H4-Cl)2}2(PPh3)2 (4). Yield: 53 %,
357 mg, 0.247 mmol.
1H NMR (400 MHz, CDCl3): δ ϭ 7.61-7.57 (m, 12H, CHaro), 7.45-7.36 (m,
18H, CHaro), 6.85 (d, 4H, C6H4, 3J ϭ 8.7 Hz), 6.55 (d, 4H, C6H4, 3J ϭ
8.7 Hz), 3.75-3.62 (m, 16H, N(CH2)2Cl), 2.22 (t, 4H, (CH2)2CH2, 3J ϭ
reflections measured, 8944 unique (Rint ϭ 0.0308) which were used
in all calculations. R1 ϭ 0.0524 (I > 2σ(I)) and wR2 ϭ 0.1594,
Ϫ3
˚
GOF ϭ 1.081; max./min. residual density 2.787/Ϫ1.592 eA
.
¯
Crystal data for 3; C42H46Cl4N4O8Ru2, triclinic space group P1
(No. 2), cell parameters a ϭ 10.2849(12), b ϭ 11.1549(13), c ϭ
7.2 Hz), 2.02 (t, 4H, (CH2)2CH2, 3J
ϭ 7.2 Hz), 1.34-1.50 (m, 4H,
CH2CH2CH2). 13C{1H} NMR (100 MHz, CDCl3): δ ϭ 205.85 (CO), 188.67
(COO), 144.45 (CHaro), 134.35, 134.29, 134.23, 133.82, 131.72, 130.07,
128.62, 128.59, 128.54 (CHaro), 133.98, 133.67 (CHaro), 112.46 (CHaro),
54.05, 40.98, 36.86, 34.19, 27.99 (CH2). 31P{1H} NMR (161 MHz, CDCl3):
δ ϭ 14.79. IR (CaF2, CH2Cl2): ν(CO) 2022 vs, 1974 m, 1943 vs, ν(OCO) 1614 m,
1585 m cmϪ1. ESI-MS: m/z ϭ 1469.17 [MϩNa]ϩ.
˚
20.220(3) A, Ͱ ϭ 95.111(10), β ϭ 94.363(10), γ ϭ 104.394(9)°, V ϭ
3
2226.4(5) A , Z ϭ 2, Dc ϭ 1.609 g cmϪ3, F(000) 1092, 7868 reflec-
˚
tions measured, 5227 unique (Rint ϭ 0.0906) which were used in all
calculations. R1 ϭ 0.0496 (I > 2σ(I)) and wR2 ϭ 0.1227, GOF ϭ
Ϫ3
˚
0.918; max./min. residual density 0.554/Ϫ0.942 eA
.
Ru2(CO)4(O2CC3H6-C6H5)2(C5H5N)2 (5). Yield: 67 %, 252 mg,
0.316 mmol.
¯
Crystal data for 5; C34H32N2O8Ru2, triclinic space group P1 (No.
˚
2), cell parameters a ϭ 9.614(4), b ϭ 10.713(4), c ϭ 17.766(9) A,
1H NMR (400 MHz CDCl3): δ ϭ 8.76 (m, 4H, C5H5N), 7.82 (m, 2H,
C5H5N), 7.38 (m, 4H, C5H5N), 7.13-7.23 (m, 6H, C6H5), 7.03 (dd, 4H, C6H5,
5J ϭ 1.53 Hz 3J ϭ 6.63 Hz), 2.53 (t, 4H, OOCCH2CH2, 3J ϭ 7.8 Hz), 2.32
(t, 4H, CH2CH2C6H5, 3J ϭ 7.1 Hz), 1.84 (m, 4H, CH2CH2CH2). 13C{1H}
NMR (100 MHz CDCl3): δ ϭ 204.15 (CO), 186.50 (COO), 151.87 (C5H5N),
142.07 (C6H4), 137.32 (C5H5N), 128.41 (C6H4), 128.23 (C6H4), 125.72
(C6H4), 124.85 (C5H5N), 36.29 (CH2), 35.15 (CH2), 27.83 (CH2). IR (CaF2,
CH2Cl2): ν(CO) 2023 vs, 1971 m, 1938 vs, ν(OCO) 1600 w, 1569 m cmϪ1. ESI-
MS: m/z ϭ 821.5 [MϩNa]ϩ, 742.7 [M-2COϩH]ϩ.
3
˚
Ͱ ϭ 73.17(5), β ϭ 88.74(5), γ ϭ 72.71(5)°, V ϭ 1668.3(12) A , Z ϭ
2, Dc ϭ 1.590 g cmϪ3, F(000) 804, 6070 reflections measured, 4331
unique (Rint ϭ 0.0642) which were used in all calculations. R1
0.0403 (I > 2σ(I)) and wR2 ϭ 0.1011, GOF ϭ 0.915; max./min.
ϭ
Ϫ3
˚
residual density 0.838/Ϫ1.007 eA
.
Crystal data for 6; C60H52O8P2Ru2, monoclinic space group
P21/n (No. 14), cell parameters a ϭ 15.2072(9), b ϭ 39.987(2), c ϭ
3
˚
˚
Ru2(CO)4(O2CC3H6-C6H5)2(PPh3)2 (6). Yield: 69 %, 206 mg,
0.177 mmol.
17.5163(11) A, β ϭ 90.797(5)°, V ϭ 10650.4(11) A , Z ϭ 8, Dc ϭ
1.453 g cmϪ3, F(000) 4752, 18938 reflections measured, 8571
1H NMR (400 MHz, CDCl3): δ ϭ 7.53 (m, 12H, PPh3), 7.33 (m, 18H, PPh3),
unique (Rint ϭ 0.1735) which were used in all calculations. R1
ϭ
7.17 (m, 6H, C6H5), 6.89 (m, 4H, C6H5), 2.25 (t, 4H, OOCCH2CH2, 3J ϭ
0.0650 (I > 2σ(I)) and wR2 ϭ 0.1572, GOF ϭ 0.834; max./min.
7.7 Hz), 1.96 (t, 4H, CH2CH2C6H5, 3J
ϭ
7.4 Hz), 1.42 (m, 4H,
˚
residual density 0.661/Ϫ1.436 eAϪ3. Figures 1 to 4 were drawn with
CH2CH2CH2C6H5). 13C{1H} NMR (100 MHz, CDCl3): δ ϭ 205.66 (CO),
188.30 (COO), 142.24 (Caro), 134.12 (Caro), 134.06 (Caro), 134.00 (Caro),
133.69 (Caro), 133.53 (Caro), 133.37 (Caro), 129.86 (Caro), 128.66 (Caro), 128.41
(Caro), 128.37 (Caro), 128.32 (Caro), 125.82 (Caro), 36.76 (CH2), 35.25 (CH2),
27.57 (CH2). 31P{1H} NMR (161 MHz, CDCl3): δ ϭ 12.72 ppm. IR (CaF2,
CH2Cl2): ν(CO) 2022 vs, 1977 m, 1949 s, ν(OCO) 1566 s cmϪ1. ESI-MS: m/z ϭ
1187.6 [MϩNa]ϩ, 845.1 [M-PPh3-3COϩNaϩCH3OH]ϩ.
ORTEP [11].
CCDC 698270 (2), 698271 (3), 698272 (5) and 698273 (6) contain
the supplementary crystallographic data for this paper. These data
can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Alternative Synthesis of 5 and 6
Results and Discussion
A suspension of Ru3(CO)12 (111 mg, 0.174 mmol) and 4-phenyl-1-
butyric acid (85 mg, 0.515 mmol) in dry methanol (50 ml) was re-
fluxed (bath temperature 70 °C) under inert atmosphere in a classi-
Synthesis
In a high pressure Schlenk tube, dodecacarbonyltriru-
cal Schlenk tube overnight. After filtration of the methanol solu- thenium reacts first with the appropriate carboxylic acid in
116 www.zaac.wiley-vch.de
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2009, 115Ϫ119

New Dinuclear Ru2(CO)4 Sawhorse-Type Complexes
Scheme 1.
tetrahydrofuran at 120 °C to yield the corresponding than those of the triphenylphosphine analogues 2 and 6
˚
thf-intermediates [Ru2(CO)4(O2CR)2(thf)2], which react (2.7107(9) to 2.7197(6) A). This difference in the
with two-electron donor ligands L such as pyridine metalϪmetal separation can be associated to an increase in
or triphenylphosphine to give the complexes Ru2(CO)4- electron density between the metal atoms as a result of the
(O2CR)2L2 1Ϫ6 in good yields according to Equation (1).
lack of back-bonding to the NC5H5 ligands.
2/3 Ru3(CO)12 ϩ 2 RCOOH ϩ 2 L Ǟ
Ru2(CO)4(O2CR)2L2 ϩ 4 CO ϩ H2 (1)
Compounds 1Ϫ6 are air-stable yellow crystalline pow-
ders which have been characterized by IR, NMR and mass
spectroscopy. All compounds exhibit in the ν(CO) region of
the infrared spectrum the characteristic pattern of the
Ru2(CO)4 sawhorse unit: three bands around 2000 cmϪ1 for
the CO terminal ligands and two bands for symmetric and
asymmetric vibrations of the carboxylato bridges, around
1500Ϫ1600 cmϪ1 [1].
A convenient method for the synthesis of diruthenium
sawhorse-type complexes avoiding pressure Schlenk tube
heating was reported by A. H. White and co-workers [12].
We therefore tried to find out if refluxing conditions are
sufficient for the synthesis of our complexes. Indeed, re-
fluxing Ru3(CO)12 and the corresponding carboxylic acid
in methanol turned out to be adequate. The yields, however,
are not higher: In the case of 5 and 6, the yields are identical
to those obtained in the classical high-temperature syn-
thesis.
Figure 1. ORTEP drawing of 2, at 50 % probability level for
thermal displacement ellipsoids, with hydrogen atoms being
omitted for clarity.
Crystal Structures
Crystals suitable for X-ray structural analysis were ob-
tained by slow diffusion of hexane in concentrated solutions
of 2, 3, 5 and 6 in chloroform. The single-crystal structure
analyses of 2, 3, 5 and 6 exhibit the Ru2(CO)4 sawhorse
backbone with the two two-electron donor ligands in the
axial positions and the carboxylato bridges in the equa-
torial positions. The molecular structures of 2, 3, 5 and 6
are shown in Figures 1, 2, 3 and 4, respectively, and a series
of selected geometrical parameters are presented in Table 1.
All RuϪRu distances are in the range of a ruthenium-
Figure 2. ORTEP drawing of 3, at 50 % probability level for
thermal displacement ellipsoids, with hydrogen atoms being
ruthenium single bond but they are considerably shorter in
˚
the pyridine derivatives 3 and 5 (2.6816(7) and 2.669(1) A) omitted for clarity.
Z. Anorg. Allg. Chem. 2009, 115Ϫ119
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
117

M. Auzias, J. Mattsson, B. Therrien, G. Süss-Fink
ARTICLE
˚
Table 1. Selected bond lengths /A and angles /° for 2, 3, 5 and 6
2
3
5
6A
PPh3
6B
PPh3
L ϭ
PPh3
NC5H5
NC5H5
Distances
RuϪRu
RuϪL(1)
RuϪL(2)
RuϪOcarboxylato 2.128(3)
RuϪOcarboxylato 2.143(3)
RuϪOcarboxylato 2.122(3)
RuϪOcarboxylato 2.147(3)
2.7197(6) 2.6816(7) 2.6689(13) 2.7107(9) 2.7156(9)
2.424(1)
2.454(1)
2.223(5)
2.239(5)
2.113(4)
2.124(3)
2.119(4)
2.136(4)
2.221(4)
2.228(4)
2.113(3)
2.129(3)
2.113(3)
2.126(3)
2.429(2)
2.435(2)
2.129(5)
2.164(5)
2.120(6)
2.127(6)
2.427(2)
2.446(2)
2.120(6)
2.121(6)
2.143(5)
2.144(5)
Angles
Ocarboxylato
O-Ru-O
O-Ru-O
Ccarbonyl
C-Ru-C
C-Ru-C
86.2(1)
85.4(1)
85.1(1)
86.2(1)
84.9(1)
83.8(1)
85.4(2)
82.2(2)
84.1(2)
81.7(2)
89.7(2)
88.3(2)
89.2(2)
89.2(2)
87.7(2)
90.2(2)
88.0(4)
90.1(4)
89.2(4)
89.7(4)
Figure 4. ORTEP drawing of 6A, at 50 % probability level for
thermal displacement ellipsoids, with hydrogen atoms omitted for
clarity.
Torsion angles
LϪRuϪRuϪL Ϫ18.5(2) Ϫ8.2(5)
Ϫ3.0(4)
32.5(5) Ϫ40.1(5)
cally active acids, ethacrynic acid is a Glutathione S-Trans-
ferase inhibitor (an enzyme involved in the process of de-
toxification of the cell) [14], while chlorambucil is an
alkylating agent inducing death cell by apoptosis [15]. Ac-
cording to the X-ray analysis structures of complexes 2 and
3, the coordination of ethacrynic acid and chlorambucil do
not induce any changes in their structure. They are coordi-
nated to the ruthenium atoms by the carboxylato bridge
keeping their active parts free, the methylene group and the
two chloro-ethyl arms, respectively. However, complexes
1Ϫ4 showed no cytotoxicity on human ovarian cancer cells,
due probably to their very low solubility in water.
In conclusion we have synthesized and structurally
characterized six new sawhorse-type complexes containing
various carboxylato bridging ligands. Additionally, we de-
scribed a method of synthesis using milder conditions as
compared to the classical method.
Acknowledgement
Figure 3. ORTEP drawing of 5, at 50 % probability level for
thermal displacement ellipsoids, with hydrogen atoms omitted for
clarity.
We are grateful to the Fonds National Suisse de la Recherche Scien-
tifique. A generous loan of ruthenium chloride from the Johnson
Matthey Technology Centre is also gratefully acknowledged.
The OCO bond angles of the carboxylato bridges [2:
126.6(4) and 127.9(4)°, 3: 125.9(5) and 127.0(5)°, 5: 124.9(4)
and 125.0(4)°, 6A: 124.2(8) and 125.4(8)°, 6B: 123.5(8) and
125.1(7)°] differ only slightly from those observed in other
Ru2(CO)4(O2CR)2L2 complexes [2, 3b, 3d].
The unit cell of complex 6 contains two symmetry-inde-
pendent molecules, identified 6A and 6B, respectively. How-
ever, the two molecules are almost identical, the main differ-
ence being in the relative position of the phenyl rings of the
two coordinated phenylbutyl carboxylato bridging ligands.
Diruthenium sawhorse-type complexes containing por-
phyrin-derived ligands show interesting anti-cancer proper-
ties [13]. Ethacrynic acid and chlorambucil are two biologi-
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Received: August 29, 2008
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