Mononuclear arene ruthenium complexes containing 5,6-diphenyl-3-(pyridine-2-yl)-1,2,4-triazine as chelating ligand: Synthesis and molecular structure

Article abstract of DOI:10.1016/j.ica.2007.11.007

The mononuclear cations of the general formula [(η⁶-arene)RuCl(pdpt)]⁺ (pdpt = 5,6-diphenyl-3-(pyridine-2-yl)-1,2,4-triazine; arene = C₆H₆ (1); C₆H₅Me (2); p-PrⁱC₆H₄Me (3); C₆Me₆ (4)) have been synthesised from 5,6-diphenyl-3-(pyridine-2-yl)-1,2,4-triazine (pdpt) and the corresponding chloro complexes [(η⁶-C₆H₆)Ru(μ-Cl)Cl]₂, [(η⁶-C₆H₅Me)Ru(μ-Cl)Cl]₂, [(η⁶p-PrⁱC₆H₄Me)Ru(μ-Cl)Cl]₂ and [(η⁶-C₆Me₆)Ru(μ-Cl)Cl]₂, respectively. The X-ray crystal structure analyses of [1][PF₆] · (C₆H₆)_2.5 and [2][PF₆] · (CH₃CN)₂ reveal a typical piano-stool geometry around the metal centre and in the crystal packing a complexed networks of intermolecular interactions.

Full text of DOI:10.1016/j.ica.2007.11.007

Available online at www.sciencedirect.com
Inorganica Chimica Acta 361 (2008) 2601–2608
www.elsevier.com/locate/ica
Mononuclear arene ruthenium complexes containing
5,6-diphenyl-3-(pyridine-2-yl)-1,2,4-triazine as chelating ligand:
Synthesis and molecular structure
Bruno Therrien *, Cynthia Saıd-Mohamed, Georg Suss-Fink
¨
¨
ˆ ˆ
Institut de Chimie, Universite´ de Neuchatel, Case postale 158, CH-2009 Neuchatel, Switzerland
Received 16 May 2007; received in revised form 15 August 2007; accepted 2 November 2007
Available online 7 November 2007
Abstract
The mononuclear cations of the general formula [(g6-arene)RuCl(pdpt)]+ (pdpt = 5,6-diphenyl-3-(pyridine-2-yl)-1,2,4-triazine; are-
ne = C6H6 (1); C6H5Me (2); p-PriC6H4Me (3); C6Me6 (4)) have been synthesised from 5,6-diphenyl-3-(pyridine-2-yl)-1,2,4-triazine (pdpt)
and the corresponding chloro complexes [(g6-C6H6)Ru(l-Cl)Cl]2, [(g6-C6H5Me)Ru(l-Cl)Cl]2, [(g6p-PriC6H4Me)Ru(l-Cl)Cl]2 and [(g6-
C6Me6)Ru(l-Cl)Cl]2, respectively. The X-ray crystal structure analyses of [1][PF6] ꢀ (C6H6)2.5 and [2][PF6] ꢀ (CH3CN)2 reveal a typical
piano-stool geometry around the metal centre and in the crystal packing a complexed networks of intermolecular interactions.
Ó 2007 Elsevier B.V. All rights reserved.
Keywords: Arene ligands; N ligand; Polypyridyl ligand; Ruthenium
1. Introduction
Similarly, organometallic g6-arene ruthenium com-
plexes have been investigated as anticancer drug candi-
dates. They are known to interact with DNA to form
monofunctional DNA adducts [4c,6]. Therefore, we were
interested in combining an arene ruthenium moiety with
a polypyridyl ligand able to interact with DNA at its
periphery. Herein we report on the synthesis and character-
isation of mononuclear arene ruthenium complexes with
the polypyridyl chelate ligand, 5,6-diphenyl-3-(pyridine-2-
yl)-1,2,4-triazine (pdpt). After coordination to the ruthe-
nium atom, the pdpt ligand still possesses a free pyridyl
function for intermolecular interactions.
Ruthenium complexes attract more and more attention
in view of their applications as biological active species
[1]. Two ruthenium-based anticancer drugs, NAMI-A [2]
and KP1019 [3], have completed phase I clinical trials and
are scheduled to enter phase II in the near future (see
Fig. 1). Among classical ruthenium anticancer drugs, poly-
pyridyl–Ru systems have been used as molecular DNA
probes owing to their photoluminescence properties and
ability to intercalate DNA [4]. These potential DNA-target-
ing anticancer agents have been screened for anticancer
activity. Numerous examples of polypyridyl–Ru complexes
including [2,20-bipyridine, 1,10-phenanthroline, 2,20:60200-
terpyridine] have been studied [5]. In all cases, their bio-
logical activity was related to their ability to intercalate
DNA.
N
N
N
N
*
Corresponding author. Tel.: +41 032 7182499; fax: +41 032 7182511.
pdpt
E-mail address: bruno.therrien@unine.ch (B. Therrien).
0020-1693/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2007.11.007

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B. Therrien et al. / Inorganica Chimica Acta 361 (2008) 2601–2608
are dissolved in methanol (30 mL). The mixture is heated
to 50 °C and stirred for 4 h. After cooling to room temper-
ature, the volume is reduced and the product is precipitated
by the addition of diethylether. The orange–brown solid is
filtered, washed with n-pentane and dried under vacuum to
give [(g6-C6H5Me)RuCl(pdpt)][PF6] (170 mg, 0.25 mmol,
NH
NH
Cl
N
Ru
S
NH
N
Cl
Cl
O
Cl
Cl
Cl
Ru
N
H
NH
Cl
Cl
yield 66%). 1H NMR (400 MHz, CD3CN):
d
N
H
N
HN
3
(ppm) = 2.34 (s, 3H, C6H5CH3), 5.79 (d, 1H, J = 6.0 Hz,
C6H5CH3), 5.83 (d, 1H, C6H5CH3), 5.85 (dd, 1H,
3J = 5.9 Hz, C6H5CH3), 6.13 (dd, 1H, C6H5CH3), 6.18
(dd, 1H, C6H5CH3), 7.46 (m, 6H, C6H5), 7.72 (m, 4H,
NAMI-A
KP1019
Fig. 1. Clinically evaluated ruthenium-based anticancer drugs.
3
C6H5), 7.88 (dd, 1H, J = 5.6 Hz, C5H4N), 8.30 (dd, 1H,
3
3J = 7.8 Hz, C5H4N), 8.68 (d, 1H, J = 9.4 Hz, C5H4N),
3
9.45 (d, 1H, J = 7.6 Hz, C5H4N); IR (KBr, cmꢁ1): m(P-
2. Experimental
F) 838s; 558m; UV–Vis (5.9 ꢂ 10ꢁ6 M, CH3CN): kmax
298 nm (e = 9.76 ꢂ 104 Mꢁ1 cmꢁ1); ESI-MS (m/z): 539
[M+]; Anal. Calc. for C27H22N4ClF6PRu: C, 47.41; H,
3.24; N, 8.19. Found: C, 47.19; H, 3.37; N, 8.37%.
2.1. General remarks
5,6-Diphenyl-3-(pyridine-2-yl)-1,2,4-triazine (pdpt) and
KPF6 were purchased from Aldrich and used as received.
[(g6-arene)Ru(l-Cl)Cl]2 (arene = C6H6, C6H5Me, p-
PriC6H4Me, C6Me6) were prepared according to the pub-
lished methods [7]. The NMR spectra were recorded on a
Bruker AMX 400 MHz spectrometer using the residual
protonated solvent as internal standard. Infrared spectra
were recorded as KBr pellets on a Perkin–Elmer FTIR
1720-X spectrometer. UV–Vis absorption spectra were
recorded on an Uvikon 930 spectrophotometer. Microanal-
yses were performed by the Laboratory of Pharmaceutical
Chemistry, University of Geneva (Switzerland). Electro-
spray mass spectra were obtained in positive-ion mode with
an LCQ Finnigan mass spectrometer.
2.4. [(g6-p-PriC6H4Me)RuCl(pdpt)][PF6] ([3][PF6])
[(g6-p-PriC6H4Me)Ru(l-Cl)Cl]2 (100 mg, 0.16 mmol),
C20H14N4 (101.34 mg, 0.32 mmol) and KPF6 (60.15 mg,
0.32 mmol) are dissolved in methanol (30 mL). The mix-
ture is heated to 50 °C and stirred for 4 h. After cooling
to room temperature, the volume is reduced and the prod-
uct is precipitated by the addition of diethylether. The
brown solid is filtered, washed with n-pentane and dried
under vacuum to give [(g6-p-PriC6H4Me)RuCl(pdpt)][PF6]
(120 mg, 0.16 mmol, yield 51%). 1H NMR (400 MHz,
3
CD3CN): d (ppm) = 1.20 (d, 3H, J = 3.4 Hz, CH(CH3)2),
3
1.22 (d, 3H, J = 3.5 Hz, CH(CH3)2), 2.17 (s, 3H, CH3),
2.89 (sept, 1H, 3J = 6.9 Hz, CH(CH3)2), 5.80 (d, 1H,
2.2. [(g6-C6H6)RuCl(pdpt)][PF6] ([1][PF6])
3J = 6.2 Hz, C6H4), 5.85 (d, 1H, J = 6.3 Hz, C6H4), 6.01
3
(d, 1H, C6H4), 6.03 (d, 1H, C6H4), 7.52 (dd, 2H, C6H5),
7.55 (dd, 2H, C6H5), 7.65 (m, 2H, C6H5), 7.75 (m, 4H,
[(g6-C6H6)Ru(l-Cl)Cl]2 (100 mg, 0.20 mmol), pdpt
(124 mg, 0.40 mmol) and KPF6 (73.6 mg, 0.40 mmol) are
dissolved in methanol (30 mL). The mixture is heated to
50 °C and stirred for 4 h. After cooling to room temperature,
the volume is reduced and the product is precipitated by the
addition of diethylether. The orange solid is filtered, washed
with n-pentane and dried under vacuum to give [(g6-
3
C6H5), 7.91 (dd, 1H, J = 5.6 Hz, C5H4N), 8.31 (dd, 1H,
3J = 7.9 Hz, C5H4N), 8.69 (d, 1H, 3J = 10 Hz, C5H4N),
3
9.44 (d, 1H, J = 7.5 Hz, C5H4N); IR (KBr, cmꢁ1): m(P-
F) 839s; 558m; UV–Vis (1.0 ꢂ 10ꢁ5 M, CH3CN): kmax
300 nm (e = 3.29 ꢂ 104 Mꢁ1 cmꢁ1); ESI-MS (m/z): 581
[M+]; Anal. Calc. for C30H28N4ClF6PRu: C, 49.63; H,
3.89; N, 7.72. Found: C, 49.19; H, 3.91; N, 7.69%.
1
C6H6)RuCl(pdpt)][PF6] (60 mg, 0.09 mmol, yield 22%). H
NMR (400 MHz, CD3CN): d (ppm) = 6.14 (s, 6H, C6H6),
7.53 (m, 4H, C6H5), 7.63 (m, 2H, C6H5), 7.75 (m, 4H,
2.5. [(g6-C6Me6)RuCl(pdpt)][PF6] ([4][PF6])
3
C6H5), 7.89 (dd, 1H, J = 5.6 Hz, C5H4N), 8.31 (dd, 1H,
3J = 7.8 Hz, C5H4N), 8.68 (d, 1H, 3J = 10 Hz, C5H4N),
[(g6-C6Me6)Ru(l-Cl)Cl]2
(100 mg,
0.15 mmol),
3
9.52 (d, 1H, J = 7.6 Hz, C5H4N); IR (KBr, cmꢁ1): m(P-F)
C20H14N4 (92.8 mg, 0.30 mmol) and KPF6 (55.10 mg,
0.30 mmol) are dissolved in methanol (30 mL). The mix-
ture is heated to 50 °C and stirred for 4 h. After cooling
to room temperature, the volume is reduced and the prod-
uct is precipitated by the addition of diethylether. The dark
red solid is filtered, washed with n-pentane and dried under
vacuum to give [(g6-C6Me6)RuCl(pdpt)][PF6] (120 mg,
840s; 558m. UV–Vis (6.6 ꢂ 10ꢁ5 M, CH3CN): kmax
298 nm (e = 0.97 ꢂ 104 Mꢁ1 cmꢁ1); ESI-MS (m/z): 525
[M+]; Anal. Calc. for C26H20N4ClF6PRu: C, 46.61; H,
3.01; N, 8.36. Found: C, 46.60; H, 3.61; N, 8.05%.
2.3. [(g6-C6H5Me)RuCl(pdpt)][PF6] ([2][PF6])
1
0.16 mmol, yield 53%). H NMR (400 MHz, CD3CN): d
[(g6-C6H5Me)Ru(l-Cl)Cl]2 (100 mg, 0.19 mmol), pdpt
(117.5 mg, 0.38 mmol) and KPF6 (69.7 mg, 0.38 mmol)
(ppm) = 2.19 (s, 18H, C6(CH3)6), 7.44 (dd, 2H,
3J = 7.9 Hz, C6H5), 7.54 (m, 6H, C6H5), 7.73 (d, 2H,

B. Therrien et al. / Inorganica Chimica Acta 361 (2008) 2601–2608
2603
Table 1
2.6. X-ray crystallographic study
Crystallographic and selected experimental data for [1][PF6] ꢀ (C6H6)2.5
and [2][PF6] ꢀ (CH3CN)2
Crystals of [1][PF6] ꢀ (C6H6)2.5 are obtained by the slow
evaporation of a chloroform/benzene solution of [1][PF6],
while the crystals of [2][PF6] ꢀ (CH3CN)2 are obtained by
the slow evaporation of an acetonitrile solution of
[2][PF6]. The data were measured using a Bruker SMART
CCD diffractometer, using Mo Ka graphite monochromat-
[1][PF6] ꢀ (C6H6)2.5 [2][PF6] ꢀ (CH3CN)2
C41H35ClF6N4PRu C31H28ClF6N6PRu
Chemical formula
Formula weight
Crystal system
Space group
Crystal colour and shape
Crystal size
865.22
766.08
monoclinic
P21/n (No. 14)
red block
monoclinic
P21/n (No. 14)
red needle
˚
ed radiation (k = 0.71073 A). The structures were solved by
0.18 ꢂ 0.14 ꢂ 0.13 0.32 ꢂ 0.08 ꢂ 0.07
˚
a (A)
15.716(1)
10.8734(6)
22.995(2)
98.695(6)
3884.3(5)
4
8.5006(5)
20.086(2)
18.890(1)
124.652(6)
3199.1(4)
4
direct methods using the program SHELXS-97 [8]. The refine-
ment and all further calculations were carried out using
SHELXL-97 [8]. The H-atoms were included in calculated
positions and treated as riding atoms using the SHELXL
default parameters. The non-H atoms were refined aniso-
tropically, using weighted full-matrix least-square on F2.
Crystallographic details are summarised in Table 1. Figs.
3 and 4 are drawn with ORTEP [9] and Figs. 5–7 with MER-
CURY [10].
˚
b (A)
˚
c (A)
b (°)
3
˚
V (A )
Z
T (K)
173(2)
173(2)
Dcalc (g cmꢁ3
)
1.480
1.591
l (mmꢁ1
)
0.578
0.691
Scan range (°)
1.70 < h < 25.66
7311
1.49 < h < 25.66
5585
Unique reflections
Observed reflections
[I > 2r(I)]
4805
3836
3. Results and discussion
Rint
0.0730
0.2008
Final R indices [I > 2r(I)]a
R indices (all data)
Goodness-of-fit
0.0433, wR2 0.0944 0.1196, wR2 0.3046
0.0774, wR2 0.1022 0.1547, wR2 0.3202
The arene ruthenium complexes [(g6-arene)Ru(l-Cl)Cl]2
(arene = C6H6, C6H5Me, p-PriC6H4Me, C6Me6) react with
two equivalents of 5,6-diphenyl-3-(pyridine-2-yl)-1,2,4-tri-
azine (pdpt) in methanol at 50 °C in the presence of
KPF6 to form the cationic arene ruthenium complexes
[(g6-C6H6)RuCl(pdpt)]+ (1), [(g6-C6H5Me)RuCl(pdpt)]+ (2),
[(g6-p-PriC6H4Me)RuCl(pdpt)]+ (3) and [(g6-C6Me6)RuCl-
(pdpt)]+ (4), which are isolated as their hexafluorophos-
phate salts (Scheme 1). The hexafluorophosphate salts of
complexes 1–4 are orange–brown, non-hygroscopic, air-
stable solids. They are sparingly soluble in methanol, chlo-
roform and water, but well soluble in dichloromethane,
acetone and acetonitrile. All compounds have been charac-
0.903
1.144
Maxiꢁm3um, minimum Dq/e
0.877, ꢁ0.601
2.296, ꢁ2.387
˚
(A
)
P
P
2
2 1=2
a
Structure was refined on F 2o: wR2 ¼ ½ ½wðF o2 ꢁ F c2Þ ꢃ= wðF 2oÞ ꢃ
,
P
2
where wꢁ1 ¼ ½ ðF o2Þ þ ðaPÞ þ bPꢃ and P ¼ ½maxðF 02; 0Þ þ 2F 2c ꢃ=3.
3
C6H5), 7.93 (dd, 1H, J = 5.6 Hz, C5H4N), 8.26 (dd, 1H,
3J = 7.8 Hz, C5H4N), 8.68 (d, 1H, 3J = 10 Hz, C5H4N),
9.03 (d, 1H, J = 7.6 Hz, C5H4N); IR (KBr, cmꢁ1): m(P-
3
F) 840s; 558m; UV–Vis (1.1 ꢂ 10ꢁ5 M, CH3CN): kmax
439 nm (e = 0.45 ꢂ 104 Mꢁ1 cmꢁ1), 295 nm (e = 1.63 ꢂ
104 Mꢁ1 cmꢁ1); ESI-MS (m/z): 609 [M+]; Anal. Calc. for
C32H32N4ClF6PRu: C, 50.97; H, 4.28; N, 7.43. Found: C,
50.71; H, 4.40; N, 7.47%.
1
terised on the basis of elemental analysis, H NMR, IR,
UV–Vis and mass spectroscopy.
Scheme 1. Synthesis of cations 1–4.

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0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1
2
3
4
250
300
350
400
450
500
550
600
Wavelength (nm)
Fig. 2. UV–Vis absorption data of 1–4 in acetonitrile at 298 K.
Fig. 3. Molecular structure of 1 at 50% probability level with hydrogen atoms, benzene molecules and hexafluorophosphate anion have been omitted for
clarity.
In the mass spectra they give rise to the corresponding
of the pdpt ligand are shifted downfield, especially the Ha
of the coordinated pyridyl group which is observed at
d > 9.0 ppm, while the Hd is observed at only 8.7 ppm.
Accordingly, the aromatic protons of the phenyl groups
are observed as multiplet at d ꢄ 7.45 and 7.75 ppm. The
1H NMR spectrum of 3 exhibits two doublets for the dia-
stereotopic methyl protons of the isopropyl group. Like-
wise, the diastereotopic CH protons of the p-cymene
[M]+ molecular peaks m/z at 525, 539, 581 and 609, respec-
1
tively. The H NMR spectra of 1–4 exhibit, other than the
signals corresponding to the g6-aromatic ligand, a charac-
teristic set of fourteen signals for the diastereotopic protons
of the pdpt ligand. The ruthenium atom is stereogenic due
to the coordination of four different ligator atoms. Upon
coordination to the ruthenium atom, the aromatic protons

B. Therrien et al. / Inorganica Chimica Acta 361 (2008) 2601–2608
2605
Fig. 4. Molecular structure of 2 at 50% probability level with hydrogen atoms, acetonitrile molecules and hexafluorophosphate anion have been omitted
for clarity.
ligand give rise to four doublets observed between d = 5.8–
6.1 ppm. A septet at d = 2.89 ppm is observed for the CH
proton of the isopropyl group. Similarly, the aromatic pro-
tons of the toluene ligand in 2 give rise to five multiplets
observed between d = 5.79–6.18 ppm and a singlet at
d = 2.17 ppm for the methyl group.
Me)RuCl(2,3-bis(a-pyridyl)quinoxaline)][PF6] [13], [(g6-
C6H6)RuCl(dpqMe2)][PF6] (dpqMe2 = 6,7-dimethyl-2,3-
di(pyridine-2-yl)quinoxaline) and [(g6-p-PriC6H4Me)RuCl-
(dpqMe2)][PF6] [14]. Accordingly, there is no significant
difference in the Ru–Cl bond lengths in 1 and 2 [2.387(1)
˚
and 2.391(3) A] and reported values [12–14]. The N(1)–
The UV–Vis data of complexes 1–4 have been recorded
in acetonitrile, see Fig. 2. The electronic spectra display a
low energy absorption band in the visible region at
ꢄ440 nm and an intense band at ꢄ300 nm. The low inten-
sity band at ꢄ440 nm is assigned to the metal-to-ligand
charge transfer transition (MLCT), while the high-energy
band at ꢄ300 nm is assigned to intra-ligand p–p* transi-
tions [11].
Ru(1)–N(2) bond angles [76.5(1) in 1; 76.3(4)° in 2] are sim-
ilar to those of complexes [(g6-p-PriC6H4Me)RuCl(2,3-
bis(2-pyridyl)pyrazine)]+
[N(1)–Ru(1)–N(2) = 76.5(2)°]
[12], [(g6-p-PriC6H4Me)RuCl(2,3-bis(a-pyridyl)quinoxa-
line)]+ [N(1)–Ru(1)–N(2) = 76.2(2)°] [13], [(g6-C6H6)
RuCl(dpqMe2)][PF6] [N(1)–Ru(1)–N(2) = 76.04(15)°] and
The molecular structures of [(g6-C6H6)RuCl(pdpt)]+ (1)
and [(g6-C6H5Me)RuCl(pdpt)]+ (2) have been established
by single-crystal X-ray structure analysis of their hexa-
fluorophosphate salts. The complexes show typical piano-
stool geometry with the metal centre coordinated by the
arene ligand, a terminal chloride and the chelating pdpt
ligand. The molecular structures of [1][PF6] and [2][PF6]
are shown in Figs. 3 and 4, respectively, and a series of
selected geometrical parameters are presented in
Table 2.
Table 2
˚
Selected bond lengths (A) and angles (°) for [1][PF6] ꢀ (C6H6)2.5 and
[2][PF6] ꢀ (CH3CN)2
[1][PF6]
[2][PF6]
Interatomic distances
Ru1–N1
Ru1–N2
Ru1–Cl1
Ru1–centroid (arene)
C1–C2
2.052(3)
2.054(10)
2.087(3)
2.387(1)
1.681
1.469(5)
1.344(4)
2.091(10)
2.391(3)
1.684
1.464(15)
1.349(13)
N1–N3
In the mononuclear complexes 1 and 2, the metal centres
are stereogenic. However, since none of the ligands con-
tains chiral information, they are both obtained as a race-
mic mixture and crystallised in the centrosymmetric space
Angles
N1–Ru1–N2
N1–Ru1–Cl1
N2–Ru1–Cl1
Ru1–N1–C1
Ru1–N1–N3
Ru1–N2–C2
76.5(1)
86.38(9)
84.79(9)
118.3(2)
121.8(2)
116.9(2)
76.3(4)
84.4(3)
86.6(3)
118.7(7)
121.1(7)
116.3(7)
˚
group P 21/n. The Ru–N bond distances 2.05 and 2.09 A
in 1 and 2 are comparable to those in [(g6-p-PriC6H4Me)R-
uCl(2,3-bis(2-pyridyl)pyrazine)][BF4] [12], [(g6-p-PriC6H4-

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B. Therrien et al. / Inorganica Chimica Acta 361 (2008) 2601–2608
[(g6-p-PriC6H4Me)RuCl(dpqMe2)][PF6]
N(2) = 76.33(10)°] [14].
[N(1)–Ru(1)–
metric unit, thus giving rise to multiple intermolecular
interactions between the different components of the cell,
see Fig. 5. Among these intermolecular interactions, it is
noteworthy to mention the edge-to-face p-stacking inter-
In the presence of benzene, compound [1][PF6] crystal-
lises with two and a half molecules of benzene per asym-
Fig. 5. Crystal packing of [1][PF6] ꢀ (C6H6)2.5
.
Fig. 6. Network of 2 showing the intermolecular p-stacking interactions.

B. Therrien et al. / Inorganica Chimica Acta 361 (2008) 2601–2608
2607
late
ligand,
5,6-diphenyl-3-(pyridine-2-yl)-1,2,4-tri-
azine(pdpt). As shown by the X-ray structure analysis of
complexes 1 and 2, after coordination to the ruthenium
atom, the pdpt ligand possesses a free pyridyl function
for intermolecular interactions. The biological activity
and DNA interactions of these complexes are under
investigation.
Acknowledgements
Financial support of this work by the Swiss National
Science Foundation and a generous loan of ruthenium(III)
chloride hydrate from the Johnson Matthey Research Cen-
tre are gratefully acknowledged.
Appendix A. Supplementary material
CCDC 657156 and 647515 contain the supplementary
crystallographic data for [1][PF6] ꢀ (C6H6)2.5 and
[2][PF6] ꢀ (CH3CN)2. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif. Supplementary
data associated with this article can be found, in the online
version, at doi:10.1016/j.ica.2007.11.007.
Fig. 7. Interactions involving the hexafluorophosphate anion in
[2][PF6] ꢀ (CH3CN)2.
actions between the centrosymmetric benzene molecule
and the pdpt ligand of two molecules of 1; the C-cen-
References
˚
˚
troid separation is 3.67 A [H-centroid = 2.85 A] with a
C–Hꢀ ꢀ ꢀcentroid angle of 147.4°. Moreover, the hexa-
fluorophosphate anion interacts with neighbouring com-
plexes of 1 and solvent molecules through C–Hꢀ ꢀ ꢀF
contacts: the Cꢀ ꢀ ꢀF distances ranges from 3.22 to
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˚
3.50 A and the C–Hꢀ ꢀ ꢀF angles ranging from 126.5 to
163.8°.
In the crystal packing of [2][PF6] ꢀ (CH3CN)2, the mole-
cules of 2 form a network through p-stacking interactions
between parallel aromatic rings of adjacent complexes,
see Fig. 6. There are two types of p–p stacking interactions
involve in the multimeric system, a face-to-face and an
edge-to-face types. The centroid-centroid separation of
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´
´
ˇ ´
´
´
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˚
3.81 A, while the edge-to-face C-centroid separation is
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˚
˚
3.29 A [H-centroid = 2.58 A, C–Hꢀ ꢀ ꢀcentroid angle =
133.6°]. The distance observed between the p–p interacting
systems is in accordance with the theoretical value calcu-
lated for this stacking mode [15].
´
´
´
Novakova, O. Vrana, V. Brabec, Inorg. Chim. Acta 231 (1995) 57;
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In addition to the p-stacking interactions, in the crystal
packing of [2][PF6] ꢀ (CH3CN)2, the hexafluorophosphate
anion sits on top of the cationic complex and interacts with
adjacent acetonitrile molecules, see Fig. 7. The distance
between the centroid of the 1,2,4-triazine ring of the pdpt
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˚
ligand and the fluorine atom is 3.00 A. The hexafluoro-
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vent molecules through C–Hꢀ ꢀ ꢀF contacts: the Cꢀ ꢀ ꢀF
˚
distances being 3.72 and 3.82 A with C–Hꢀ ꢀ ꢀF angles of
167.6 and 116.5°, respectively.
In conclusion, we have synthesised and characterised
four arene ruthenium complexes with the polypyridyl che-
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