Host-guest properties of the trinuclear arene-ruthenium cluster cation [H3Ru3(C6H6)(C6Me 6)2(O)]+

Article abstract of DOI:10.1016/j.ica.2004.03.045

The trinuclear arene-ruthenium cluster cation [H₃Ru ₃(C₆H₆)(C₆Me₆) ₂(O)]⁺, containing a μ₃-oxo cap and three arene ligands that span a hydrophobic pocket above the metal skeleton, has been crystallised as tetrafluoroborate salt in the presence of various guest molecules. The host-guest complexes have been characterised by single-crystal X-ray structure analysis. With chloroform as the guest molecule, a CHCl ₃ molecule sits perfectly in the hydrophobic pocket, the hydrogen atom being encapsulated inside the cavity. When dioxane is added during the crystallisation process, the cluster forms infinite chains which are connected by a complex network of hydrogen bonds involving the μ₃-oxo ligand, water and dioxane molecules. Interestingly, in the presence of phenol, a water molecule is hydrogen-bonded between the μ₃-oxo ligand and the phenol molecule, forming a one-dimensional μ₃-O?H ₂O?HO hydrogen-bonded chain. Finally, with benzoic acid, a head-to-tail host-guest chain is obtained, the phenyl ring being incorporated in the hydrophobic pocket, while the acid group is hydrogen-bonded to the μ₃-oxo ligand.

Full text of DOI:10.1016/j.ica.2004.03.045

Inorganica Chimica Acta 357 (2004) 3289–3294
www.elsevier.com/locate/ica
Host–guest properties of the trinuclear arene–ruthenium
cluster cation [H3Ru3(C6H6)(C6Me6)2(O)]þ
*
€
Bruno Therrien , Ludovic Vieille-Petit, Georg Suss-Fink
Institut de Chimie, Universitꢀe de Neuch^atel, Case postale 2, CH-2007 Neuch^atel, Switzerland
Received 27 February 2004; accepted 20 March 2004
Available online 10 May 2004
Abstract
The trinuclear arene–ruthenium cluster cation [H3Ru3(C6H6)(C6Me6)2(O)]þ, containing a l3-oxo cap and three arene ligands
that span a hydrophobic pocket above the metal skeleton, has been crystallised as tetrafluoroborate salt in the presence of various
guest molecules. The host–guest complexes have been characterised by single-crystal X-ray structure analysis. With chloroform as
the guest molecule, a CHCl3 molecule sits perfectly in the hydrophobic pocket, the hydrogen atom being encapsulated inside the
cavity. When dioxane is added during the crystallisation process, the cluster forms infinite chains which are connected by a complex
network of hydrogen bonds involving the l3-oxo ligand, water and dioxane molecules. Interestingly, in the presence of phenol, a
water molecule is hydrogen-bonded between the l3-oxo ligand and the phenol molecule, forming a one-dimensional l3-
O ꢀ ꢀ ꢀ H2O ꢀ ꢀ ꢀ HO hydrogen-bonded chain. Finally, with benzoic acid, a head-to-tail host–guest chain is obtained, the phenyl ring
being incorporated in the hydrophobic pocket, while the acid group is hydrogen-bonded to the l3-oxo ligand.
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: Arene ligands; Cluster compounds; Host–guest systems; Hydrophobic forces; Molecular recognition
1. Introduction
the three ruthenium atoms are capped by a l3-oxo li-
gand, the single-crystal X-ray structure analysis of the
tetrafluoroborate salt showed the l3-oxo ligand to be
strongly hydrogen-bonded to a water molecule [7].
Furthermore, we observed for two derivatives of the
parent cluster 1, [H3Ru3{C6H5(CH2)2OH}(C6Me6)2-
(O)]þ(2) and [H3Ru3{C6H5(CH2)3OH}(C6Me6)2(O)]þ-
(3), that a benzene molecule can be hosted in the
hydrophobic pocket spanned by the three arene ligands
[8], see Scheme 1. Therefore, we postulated that in the
presence of cluster 1, molecules which possess a phenyl
ring and a functional group suitable for the formation of
hydrogen-bonds will self-assemble in a predictable
fashion.
Herein, we report on the crystallisation of the cluster
cation [H3Ru3(C6H6)(C6Me6)2(O)]þ (1) as the tetraflu-
oroborate salt in the presence of chloroform, dioxane,
phenol or benzoic acid and on the single-crystal X-ray
characterisation of the solids obtained. The results show
that the hydrophobic pocket, spanned by the three arene
ligands in 1, plays a crucial role in the formation of the
crystalline products.
Host–guest chemistry is a flourishing research area, in
particular in view of crystal engineering; self-assembly,
templation, and molecular encapsulating are amongst the
most studied phenomena [1]. They are governed by sev-
eral factors such as hydrogen bonding [2], p–p interac-
tions [3], and C–H ꢀ ꢀ ꢀ p interactions [4], but the prediction
on the formation of a host–guest complex remains a dif-
ficult task. The inclusion of small organic molecules such
as acetonitrile, nitromethane or diethylether in the or-
ganic ligand cavity of organometallic complexes has been
observed in the case of [(1,5-COD)6Ir6W4O16]2ꢁ [5] and
[(p-MeC6H4Pri)Ru(CTV)]2þ as well as [(C6Me6)Ru-
(CTV)]2þ (CTV ¼ 2,3,7,8,12,13-hexamethoxy-5,10-dihy-
dro-15H-tribenzo[a,d,g]-cyclononene) [6].
Recently, we synthesised in aqueous solution the
cluster cation [H3Ru3(C6H6)(C6Me6)2(O)]þ (1), in which
* Corresponding author. Tel.: +41-32-718-2499; fax: +41-32-718-
2511.
E-mail address: bruno.therrien@unine.ch (B. Therrien).
0020-1693/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2004.03.045

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B. Therrien et al. / Inorganica Chimica Acta 357 (2004) 3289–3294
H
(O)][BF4] (1 mg). The solution is left at room tempera-
ture overnight, the test tube being slightly open, until
small red plates are observed.
+
+
O
H
O
Ru
O
H
H O
H
Ru
H
Ru
H
2.2.2. Preparation of [1][BF4] ꢀ H2O ꢀ 0.5C4H8O2
In a test tube, 1 ml of dioxane is added to an acetone
solution (3 ml) of [H3Ru3(C6H6)(C6Me6)2(O)][BF4] (1
mg). The solution is left at room temperature for several
days, the test tube being slightly open, until red blocks
are observed.
H
Ru
Ru
Ru
H
[1 · H2O]+
[C6H6⊂2]+
Scheme 1.
2.2.3. Preparation of [1][BF4] ꢀ H2O ꢀ C6H5OH
In a test tube, 1 mg of phenol is added to an acetone
solution (3 ml) of [H3Ru3(C6H6)(C6Me6)2(O)][BF4] (1
mg). The solution is left at room temperature for two
days, the test tube being slightly open, until red crys-
talline blocks are observed.
2. Experimental
2.1. General remarks
Solvents (technical grade) and other reagents were
purchased (Aldrich, Fluka) and used as received. The
starting compound [H3Ru3(C6H6)(C6Me6)2(O)][BF4]
(cation 1) was prepared according to published methods
[7].
2.2.4. Preparation of [C6H5COOHꢂ1][BF4]
To an acetone solution (3 ml) of [H3Ru3(C6H6)-
(C6Me6)2(O)][BF4] (1 mg) is added benzoic acid (1 mg).
The mixture is left slightly opened overnight, and two
days later small orange plates are observed.
2.2. Crystallisations
2.3. X-ray crystallographic study
2.2.1. Preparation of [CHCl3ꢂ1][BF4] ꢀ CHCl3
In a test tube, 1 ml of chloroform is added to an
acetone solution (3 ml) of [H3Ru3(C6H6)(C6Me6)2-
The data were measured using a Bruker SMART
CCD diffractometer, using Mo Ka graphite mono-
Table 1
Crystallographic and selected experimental data of [CHCl3ꢂ1][BF4] ꢀ CHCl3, [1][BF4] ꢀ H2O ꢀ 0.5C4H8O2, [1][BF4] ꢀ H2O ꢀ C6H5OH, and
[C6H5COOHꢂ1][BF4]
[CHCl3ꢂ1][BF4] ꢀ CHCl3
32H47BCl6F4ORu3
[1][BF4] ꢀ H2O ꢀ 0.5C4H8O2 [1][BF4] ꢀ H2O ꢀ C6H5OH
[C6H5COOHꢂ1][BF4]
C37H51BF4O3Ru3
Chemical formula
Formula weight
Crystal system
C
C32H51BF4O3Ru3
873.75
C36H53BF4O3Ru3
923.80
1050.42
orthorhombic
Cmcm
red plate
0.36 ꢃ 0.29 ꢃ 0.08
20.867(3)
10.891(2)
20.855(3)
90
933.80
orthorhombic
P212121
orange plate
0.48 ꢃ 0.25 ꢃ 0.05
13.129(2)
13.711(2)
19.901(3)
90
triclinic
ꢁ
monoclinic
P21=c
Space group
Crystal colour and shape
Crystal size
P1
red block
0.28 ꢃ 0.22 ꢃ 0.08
9.289(2)
red block
0.25 ꢃ 0.25 ꢃ 0.15
15.986(2)
10.550(2)
21.402(3)
90
ꢂ
a (A)
ꢂ
b (A)
13.194 (2)
13.550(2)
85.308(3)
84.475(3)
87.940(3)
1646.7(5)
2
ꢂ
c (A)
a (° )
b (° )
c (° )
90
90
90.965(2)
90
90
90
ꢂ
V (A3)
4739.4(12)
4
173(2)
3608.8(9)
4
173(2)
3582.5(8)
4
100(2)
Z
T (K)
173(2)
1.762
1.412
Dcalc (g cmꢁ3
)
1.472
1.319
1.700
1.294
1.731
1.305
l (mmꢁ1
)
Scan range (°)
Unique reflections
3:90 < 2h < 56:92
2983
3:10 < 2h < 56:98
7328
4219
2:54 < 2h < 56:86
8599
6345
3:60 < 2h < 57:14
8612
7187
Reflections used ½I > 2rðIÞꢄ 2314
Rint
0.0755
0.0607
0.0827
0.0856
Final R indices ½I > 2rðIÞꢄ
R indices (all data)
Goodness-of-fit
0.0458, wR2 0.1174
0.0634, wR2 0.1247
1.038
0. 0651, wR2 0.1457
0.1190, wR2 0.1702
0.927
0.0361, wR2 0.0764
0.0600, wR2 0.0914
1.007
0.0357, wR2 0.0668
0.0522, wR2 0.0723
1.009
Maximum,ꢁm3 inimum
1.218, )1.153
1.727, )1.138
0.821, )0.731
0.842, )0.763
ꢂ
Dq=e (A
)

B. Therrien et al. / Inorganica Chimica Acta 357 (2004) 3289–3294
3291
ꢂ
chromated radiation (k ¼ 0:71073 A). The structures
were solved by direct methods using the program
SHELXS-97 [9]. The refinement and all further calcula-
tions 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. Crystallo-
graphic details are summarised in Table 1. Figs. 1, 3, 5
and 6 were drawn with ORTEP [11] and Figs. 2, 4 and 7
with MERCURY [12].
CCDC-232284 [CHCl3ꢂ1][BF4] ꢀ CHCl3, 232 285
[1][BF4] ꢀ H2O ꢀ 0.5C4H8O2, 232 286 [1][BF4] ꢀ H2O ꢀ
C6H5OH, and 232 287 [C6H5COOHꢂ1][BF4] contain
the supplementary crystallographic data for this paper.
These data can be obtained free of charge via www.ccdc.
cam.ac.uk/data_request/cif, by emailing data_request
@ccdc.cam.ac.uk, or by contacting The Cambridge
Crystallographic Data Centre, 12, Union Road, Cam-
bridge CB2 1EZ, UK; fax: +44 1223 336033.
Fig. 2. Space filling representation of the host–guest complex
[CHCl3ꢂ1]þ.
molecules, according to molecular modelling studies
[13].
3. Results and discussion
To gain further insight in the host–guest properties of
1, we attempted to crystallise [1][BF4] in a first series
with simple molecules such as methanol, ethanol,
tetrahydrofuran, dioxane, dichloromethane and chlo-
roform. In the presence of methanol, ethanol, tetrahy-
drofuran, and dichloromethane, no crystals containing a
guest molecule could be obtained; only the already
known complex containing a water molecule hydrogen-
bonded to the l3-oxo ligand was obtained [7]. Interest-
ingly, in one instance [1][BF4] ꢀ H2O was found to
crystallise in a higher symmetry group, but it shows the
The trinuclear cluster cation [H3Ru3(C6H6)(C6Me6)2-
(O)]þ (1), accessible in aqueous solution from the
dinuclear precursor [H3Ru2(C6Me6)]þ and the mono-
nuclear building block [Ru(C6H6)(H2O)3]2þ, precipi-
tates as the tetrafluoroborate salt, which is well soluble
in acetone, dimethylsulfoxide, dichloromethane and
ethanol, and sparingly soluble in water, methanol and
chloroform [7]. The hydrophobic pocket spanned by the
three arene ligands in 1 is capable of hosting small
1
same geometric parameters. However, in the presence
of chloroform and dioxane host–guest systems have
been observed.
The crystallisation of [1][BF4] in a mixed acetone–
chloroform solution gave the host–guest complex
[CHCl3ꢂ1][BF4] ꢀ CHCl3, see Fig. 1. In the crystal, two
chloroform molecules per asymmetric unit are present,
one being hosted in the hydrophobic pocket of 1 and the
second being involved in a weak hydrogen bond with the
tetrafluoroborate anion. The guest chloroform molecule
sits perfectly in the hydrophobic pocket of 1 with its
hydrogen atom being encapsulated inside the cavity. The
distance between the carbon atom of the incorporated
ꢂ
chloroform molecule and the Ru3 plane is 4.144(7) A.
1
X-ray data for [1][BF4] ꢀ H2O; C30H47BF4O2Ru3, M ¼ 829:70 g
molꢁ1
,
monoclinic, P21=n, a ¼ 10:0820ð15Þ, b ¼ 16:329ð2Þ, c ¼
3
ꢂ
ꢂ
18:767ð3Þ A, b ¼ 90:964ð2Þ°, U ¼ 3089:2ð8Þ A , T ¼ 173 K, Z ¼ 4, l
(Mo Ka) ¼ 1.498 mmꢁ1, 7293 reflections measured, 6129 unique
(Rint ¼ 0:0608) which were used in all calculations. The final wRðF 2Þ
was 0.0775 (all data). CCDC-232203 contains the supplementary
crystallographic data for this structure.
Fig. 1. ORTEP drawing of [CHCl3ꢂ1]þ. Displacement ellipsoids are
drawn at the 50% probability level. Hydrogen atoms, hydrogen-bon-
ded chloroform molecule and tetrafluoroborate anion are omitted for
clarity.

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B. Therrien et al. / Inorganica Chimica Acta 357 (2004) 3289–3294
In the [CHCl3ꢂ1]þ host–guest system; Ru1, O1, C1,
C9, and the Cl2 atoms lie on a mirror plane. Therefore,
the Cl3 and Ru3 moieties are by symmetry in a perfect
staggered conformation, minimising steric repulsions,
see Fig. 2.
In the crystals obtained in the presence of dioxane, no
solvent molecule was observed in the hydrophobic
pocket of the cluster cation 1. Instead, a dioxane mol-
ecule, situated on the centre of symmetry, forms a hy-
drogen-bonded network with two water molecules,
which are as well hydrogen-bonded to the l3-oxo ligand
of a cluster cation, see Fig. 3. Thus, a l3-oxo-H2O-di-
oxane-H2O-l3-oxo hydrogen-bonded chain is obtained.
The O–O distances of the hydrogen bonds are, respec-
Fig. 4. Infinite chain of [1]þ in [1][BF4] ꢀ H2O ꢀ 0.5C4H8O2.
ꢂ
tively, 2.753(6) A for the l3-oxo ligand and H2O, and
ꢂ
2.807(6) A between the dioxane and the water molecule.
The total distance between the two bridged l3-oxo li-
ꢂ
gands is 11.27(1) A.
However, in the solid state, the hydrophobic cavity is
not totally unoccupied. A benzene ligand of a symmetry
related neighbouring cluster cation is slightly incorpo-
rated in the hydrophobic pocket of 1. This benzene li-
gand is as well involved in a slipped-parallel p–p
stacking interactions with a second cluster cation, thus
forming a multimer of cations, see Fig. 4.
The benzene ligand inside the cavity of a neighbour-
ing cluster interacts weakly through hydrophobic and
van der Waals contacts. The shortest distances between
the metal-bound hydrogen atoms and the closest carbon
ꢂ
atoms of the benzene ligand are 3.41 and 3.90 A. The
distance observed between the p-stacking interacting
Fig. 5. ORTEP drawing of [1][BF4] ꢀ H2O ꢀ C6H5OH. Displacement
ellipsoids are drawn at the 50% probability level. Hydrogen atoms and
tetrafluoroborate molecule are omitted for clarity.
ꢂ
systems (centroid ꢀ ꢀ ꢀ centroid 3.65 A) is in good agree-
ment with the theoretical value calculated for these
stacking modes [14].
In a second series of crystallisation experiments,
molecules with phenyl substituents such as aniline, ani-
Fig. 3. ORTEP drawing of [1][BF4] ꢀ H2O ꢀ 0.5C4H8O2. Displacement
ellipsoids are drawn at the 50% probability level. Hydrogen atoms and
tetrafluoroborate anion are omitted for clarity.
Fig. 6. ORTEP drawing of [C6H5COOHꢂ1]þ. Displacement ellipsoids
are drawn at the 50% probability level. Hydrogen atoms and tetra-
fluoroborate molecule are omitted for clarity.

B. Therrien et al. / Inorganica Chimica Acta 357 (2004) 3289–3294
3293
Fig. 7. Infinite host–guest chain of [C6H5COOHꢂ1]þ, along the c-axis.
sole, benzaldehyde, benzoic acid, methyl benzoate,
phenol, and styrene have been added to an acetone so-
lution containing [1][BF4]. Crystals suitable for X-ray
diffraction studies were obtained only with phenol and
benzoic acid.
Surprisingly, addition of phenol to an acetone solu-
tion of [1][BF4] gives rise to the formation of
[1][BF4] ꢀ H2O ꢀ C6H5OH, in which the phenyl ring is not
incorporated in the hydrophobic pocket of 1. As ob-
served with dioxane, a water molecule is inserted be-
tween the l3-oxo ligand of cation 1, and the hydroxy
phobic pocket spanned by the three arene ligands can be
seen as a bowl to guest molecules, whereas the l3-oxo
ligand is a strong acceptor to form hydrogen bonds. We
have shown that these two different sites could be oc-
cupied by benzoic acid molecules, the phenyl group
being incorporated in the hydrophobic pocket and the
acid group hydrogen-bonded to the l3-oxo ligand of a
neighbouring molecule, thus giving rise to an infinite
host–guest chain.
function of
a
phenol molecule, forming
a
l3-
Acknowledgements
O ꢀ ꢀ ꢀ H2O ꢀ ꢀ ꢀ HO–C6H5 hydrogen-bonded monomer,
see Fig. 5.
The authors are grateful to the Fonds National Suisse
de la Recherche Scientifique for financial support. A
generous loan of ruthenium chloride hydrate from the
Johnson Matthey Technology Centre is gratefully
acknowledged.
ꢂ
The l3-O ꢀ ꢀ ꢀ OH2 distance is 2.771(4) A with an angle
of 166.6° and the H2O ꢀ ꢀ ꢀ O-phenol distance is 2.668(4)
ꢂ
A with an angle of 149.7°. The tetrafluoroborate anion
participates as well to a hydrogen bond with the water
ꢂ
molecule, F–OH2 distance is 2.771(5) A with an angle of
161.4°.
References
Finally, with benzoic acid, the phenyl ring acts as
predicted as a guest molecule inside the hydrophobic
pocket of a cluster cation ([C6H5COOHꢂ1]þ), while the
carboxylic acid function interacts with a l3-oxo ligand
of a second cluster cation. Thus, giving rise to a head to
tail host–guest chain. The atoms numbering scheme of
[C6H5COOHꢂ1]þ is presented in Fig. 6.
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