Reactivity of the heteronuclear cluster RuOs3(μ-H)2(CO)13 with indene

Article abstract of DOI:10.1016/j.jorganchem.2006.10.010

The heteronuclear cluster RuOs₃(μ-H)₂(CO)₁₃ (1) reacts with indene under thermal activation to afford the novel clusters RuOs₃(μ-H)(CO)₉(μ-CO)₂(η ⁵-C₉H₇) (3), RuOs₃(μ-H)(CO)₉(μ₃,η ⁵:η²:η²-C₉H₇) (4) and Ru₂Os₃(μ-H)(CO)₁₁(μ₃, η⁵:η²:η²-C₉H ₇) (5), the latter two possessing indenyl ligands in the μ₃,η⁵:η²:η² bonding mode. Cluster 5 exists as a mixture of two isomers. The inter-relationship among the clusters has also been investigated.

Full text of DOI:10.1016/j.jorganchem.2006.10.010

Journal of Organometallic Chemistry 692 (2007) 768–773
www.elsevier.com/locate/jorganchem
Reactivity of the heteronuclear cluster RuOs3(l-H)2(CO)13
with indene
*
Yong Leng Kelvin Tan, Weng Kee Leong
Department of Chemistry, National University of Singapore, Kent Ridge, Singapore 119260, Singapore
Received 18 September 2006; received in revised form 6 October 2006; accepted 6 October 2006
Available online 13 October 2006
Abstract
The heteronuclear cluster RuOs3(l-H)2(CO)13 (1) reacts with indene under thermal activation to afford the novel clusters RuOs3(l-
H)(CO)9(l-CO)2(g5-C9H7) (3), RuOs3(l-H)(CO)9(l3,g5:g2:g2-C9H7) (4) and Ru2Os3(l-H)(CO)11(l3,g5:g2:g2-C9H7) (5), the latter two
possessing indenyl ligands in the l3,g5:g2:g2 bonding mode. Cluster 5 exists as a mixture of two isomers. The inter-relationship among
the clusters has also been investigated.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Heterometallic clusters; Ruthenium; Osmium; Isomers; Indene
1. Introduction
of the cluster framework compared to homonuclear ruthe-
nium clusters, and yet may react under relatively milder
conditions than homonuclear osmium clusters. In this arti-
cle, we present the results of our investigations into the
reaction of 1 with indene.
Studies of polycyclic aromatics such as indene enable a
direct comparison on the reactivity of multiple rings to
be made, in addition to providing an insight into the inter-
actions between p-systems and metal centers. Awareness of
transition metal complexes incorporating the indenyl
ligand as an important class of compounds for stoichiom-
etric and catalytic asymmetric induction has increased over
the last decade, with mono- and binuclear indenyl com-
plexes being tested as potential Ziegler–Natta and
Fischer–Tropsch catalysts [1]. This has revived interest in
the reactivity of indene and indenyl derivatives with orga-
nometallic clusters. The reactivity of homonuclear car-
bonyl clusters with indene has been examined by several
groups [2], although there has been comparatively few
reports on their reactions with heteronuclear clusters [3].
We have recently initiated investigations into the chemistry
of the group 8 heterotetranuclear cluster RuOs3(l-H)2-
(CO)13 (1). It was envisaged that the ruthenium vertex in
1 would be more reactive than the osmium vertices. Hence,
cluster 1 was expected to be less inclined to fragmentation
2. Results and discussion
The reaction of 1 with indene at 120 ꢁC afforded, upon
TLC separation, besides unreacted 1 and Os3(l-H)2-
(CO)10 (2) (probably a decomposition product of 1), three
novel clusters, viz., RuOs3(l-H)(CO)9(l-CO)2(g5-C9H7)
(3), RuOs3(l-H)(CO)9(l3,g5:g2:g2-C9H7) (4) and Ru2Os3-
(l-H)(CO)11(l3,g5:g2:g2-C9H7) (5) in 35%, 9% and 24%
yields (calculated with respect to consumed 1), respectively.
Shortening the reaction time afforded 3 and 5 but no 4. All
three novel clusters 3–5 have been studied by single crystal
X-ray diffraction methods.
The ORTEP plot showing the molecular structure,
together with selected bond parameters, for 3 is given in
Fig. 1. Cluster 3 retains the tetrahedral metal framework
of the parent cluster 1, with the indenyl ligand capping
the ruthenium atom. It is structurally similar to the reported
cluster RuOs3(l-H)(CO)9(l-CO)2(g5-C5H5), 3a, which was
synthesized from the reaction of [Ru(C5H5)(MeCN)3]+ with
*
Corresponding author.
E-mail address: chmlwk@nus.edu.sg (W.K. Leong).
0022-328X/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.10.010

Y.L.K. Tan, W.K. Leong / Journal of Organometallic Chemistry 692 (2007) 768–773
769
ligands, with the five-membered ring tilted at an angle of
33.6ꢁ with respect to the triosmium basal plane. This may
be ascribed to steric interaction with the two bridging car-
bonyl ligands; the bridging carbonyl ligands enable the clus-
ter to take up the additional electron density from the
‘electron rich’ Ru(g5-C9H7) fragment [5].
1
The H NMR spectrum of 3 at ambient temperature
shows a broad resonance at d À21.66 ppm. On cooling to
183 K three resonances are prominent: a major singlet at
d À22.39 ppm and two minor singlets at d À19.07 and
À20.13 ppm, with relative intensity ratio of 57:1.0:1.0
(Fig. 2). These resonances may be ascribed to the presence
of three isomers in solution. The major isomer may be
assigned as that found in the solid state, while the other
two presumably corresponded to the hydride bridging dif-
ferent metal–metal bonds. In accordance with previous
observations for tetranuclear RuOs3 clusters, where the
hydrides bridging Ru–Os edges were found to resonate at
a lower field relative to the hydrides bridging Os–Os edges
[6], it may be assumed that the two minor isomers have the
hydride bridging an Os–Ru edge but we could not be more
definite about their structures.
Fig. 1. ORTEP diagram (50% probability thermal ellipsoids, organic
hydrogens omitted) and selected bond lengths (A) and angles (deg) for 3.
Os(1)Os(1A) = 2.9489(3); Os(1)Os(2) = 2.7839(3); Os(1)Ru(3) = 2.8175(5);
Os(2)Ru(3) = 2.7635(5); Os(1)C(31A) = 2.224(5); Ru(3)C(31A) = 1.978(5);
Ru(3)C(31)Os(1A) = 83.99(17).
˚
The ORTEP plot showing the molecular structure,
together with selected bond parameters, for 4 is given in
Fig. 3. The metal framework of 4 consists of a closed tetra-
hedron with the indenyl group lying over one triangular
face. As for 3, it also has a total valence electron count
of 60, consistent with the tetrahedral cluster framework.
A hydride ligand bridges the Os(1)–Os(3) vector, but the
longest metal-metal bonds involve Ru(4). All nine carbon
[Os3H(CO)11]À [4]. The crystal structure of 3 possesses mir-
ror symmetry; the crystallographic mirror plane passes
through the Os(2)–Ru(3) vector and bisects the Os(1)–
Os(1A) edge and the indenyl ligand. The distance from
Ru(3) to the centroid of the five-membered ring is
˚
1.929(6) A. The indenyl ligand in 3 is oriented such that
the six-membered ring is above the bridging carbonyl
Fig. 2. Variable temperature 1H NMR spectra (d8-toluene) for 3.

770
Y.L.K. Tan, W.K. Leong / Journal of Organometallic Chemistry 692 (2007) 768–773
Fig. 3. ORTEP diagram (50% probability thermal ellipsoids, organic
˚
hydrogens omitted) and selected bond lengths (A) for 4.
Os(1)Os(2) = 2.7909(7); Os(1)Os(3) = 2.8560(11); Os(1)Ru(4) = 2.9079(9);
Os(2)Os(3) = 2.6670(8); Os(2)Ru(4) = 2.9749(12); Os(3)Ru(4) = 2.9543(9);
Os(1)C(6) = 2.373(7);
Os(1)C(7) = 2.197(7);
Os(2)C(4) = 2.203(7);
Os(2)C(5) = 2.250(6); Ru(4)C5ring(centroid) = 1.893(7).
Fig. 4. ORTEP diagram (50% probability thermal ellipsoids, organic
hydrogens omitted) and selected bond lengths (A) for 5.
˚
Os(1)Os(2) = 2.7283(5); Os(1)Os(3) = 2.7609(5); Os(1)Ru(4) = 2.6563(7);
Os(1)Ru(5) = 2.8190(7); Os(2)Os(3) = 2.7723(5); Os(2)Ru(5) = 2.9241(7);
Os(3)Ru(4) = 2.8203(7); Os(3)Ru(5) = 2.7989(7); Ru(4)Ru(5) = 2.8638(9);
atoms of the indenyl moiety are coordinated to the
Os(1)Os(2)Ru(4) trimetallic face, in what may be described
as involving an g5-cyclopentadienyl in addition to a g2,g2-
diene. Thus the indenyl ligand acts formally as a nine-
electron donor, reminiscent of the bonding situation found
in the related homonuclear clusters Os4(l-H)(CO)9-
(l3,g5:g2:g2-C13H15), Os4(l-H)(CO)9(l3,g5:g2:g2-C19H17),
Ru4(l-H)(CO)9(l3,g5:g2:g2-C19H17) and Ru4(l-H)(CO)9-
(l3,g5:g2:g2-C22H19) [2c,7]. Cluster 4 has also been charac-
terized by infrared and proton NMR spectroscopies as well
as FAB mass spectrometry.
The ORTEP plot showing the molecular structure,
together with selected bond parameters, for 5 is given in
Fig. 4. The metal core of 5 consists of a trigonal bipyrami-
dal Ru2Os3 framework, with a valence electron count of 72,
as predicted by the EAN rule [8]. The indenyl ligand is
bonded in a similar fashion as found for 4. It is noted that
the ruthenium atom capped by the five-membered ring is
found in an equatorial position in the metal core; there
was no evidence for an isomer with the cyclopentadienyl
ring of the indenyl ligand capping a metal atom at the axial
site. This observation is consistent with that observed for
the closely related toluene analogue Ru2Os3(CO)12-
(l-CO)(g6-C6H5Me) (5a) [9], and is also in line with previ-
ous reports on trigonal bipyramidal pentanuclear osmium
and ruthenium clusters containing arene or cyclopentadie-
nyl ligands; without exception, the aromatic ligand always
occupies an equatorial position on the pentanuclear metal
framework. It has been suggested that having the M(g5-
C5H5) fragment in the equatorial position enhanced the
electron density donation from the equatorial to the axial
sites, thereby stabilizing the cluster [5].
Os(3)C(4) = 2.216(9);
Os(3)C(5) = 2.390(9);
Ru(4)C(6) = 2.233(10);
Ru(4)C(7) = 2.227(10); Ru(5)C5 ring(centroid) = 1.869(9).
model corresponds to two different isomers and is consis-
1
tent with the solution-state H NMR spectrum. Two iden-
1
tical sets of signals appear in the organic region of the H
NMR spectrum for 5 in a 3:1 integration ratio. Assignment
of the spectral features for the isomers was aided by 2D
NOESY and COSY experiments, and the coupling con-
stants have also been elucidated via selective decoupling
experiments. The proposed solution-state structures and
tentative NMR assignments for the two isomers are shown
in Fig. 5.
We have carried out a number of experiments to under-
stand the inter-relationship among 3–5; the results are sum-
marised in Scheme 1. Cluster 5 is thermally stable and does
not fragment under prolonged heating. It is thus the ther-
modynamic sink. It was postulated that 3 may be the pre-
cursor to 4 since these two clusters differed by two
carbonyl groups. However, thermolysis of 3 only resulted
in fragmentation of the cluster. On the other hand, the yields
of 3 and 5 from the reaction of 1 with indene were dependent
on the reaction time; prolonged thermolysis resulted in an
increase in the proportion of 5 with respect to 1. The forma-
tion of 5 must involve fragmentation of 3. Cluster 5 was also
obtainable from the co-thermolysis of 1 and 3 in cyclohex-
ane; in the absence of 1 no conversion of 3 to 5 takes place.
These results also account for the low yield of 4. Under ther-
mal activation, fragmentation of 3 is apparently favoured
over decarbonylation to form 4, and the resultant Ru(g5-
C9H7) fragment combines with 1 to afford 5. This presum-
ably occurs via a pathway previously proposed for 5a, [9]
which would involve the capping of the Ru(g5-C9H7) frag-
ment onto an RuOs2 face in 1 and subsequent polyhedral
The crystal structure of 5 exhibited disorder, which was
modelled as a disorder of one of the ruthenium atoms over
two sites – M(3) and M(4). The ruthenium occupancies
refined to about 0.22 and 0.78, respectively. This disorder

Y.L.K. Tan, W.K. Leong / Journal of Organometallic Chemistry 692 (2007) 768–773
771
δ
H 4.29d
H
δ
H 4.01d
H1
δ
H 4.70d
δ
H 5.45d
δH 5.68dd
H
δ
H 5.78dd
H7
δ
H
H2
δ
H 5.07dd
H 4.90dd
H6
H
H3
H
δ
H 4.29d
Ru
Ru
δ
H 3.89d
Ru
Os
H4
Ru
H
Os
H
H
H5
δ
Hδ
δ
H -11.92s
H 5.07dd
δH -14.67s
H 5.22dd
δ
H 4.70d
δ
H 3.91d
Os
Os
Os
major isomer
Os
minor isomer
Fig. 5. Proposed solution state structures and tentative NMR assignments for 5 (carbonyls omitted). The following assignments for the minor isomer are
ambiguous: H1 with H3; H4,H5 with H7,H6, respectively.
were purified, dried, distilled, and stored under nitrogen
prior to use. Routine NMR spectra were acquired on a
Bruker ACF300 NMR spectrometer. Selective decoupling
Ru
Os
Os
H
experiments and 2D NMR spectra were acquired on a
Bruker Advance DRX500 or Bruker AMX500 machine.
The solvent used was deuterated chloroform unless other-
wise stated. Chemical shifts reported are referenced to
H
Os
1
indene
cyclohexane
120 oC, 12 h
1
that for the residual proton of the solvent for H. Mass
spectra were obtained on a Finnigan MAT95XL-T spec-
trometer in an m-nitrobenzyl alcohol matrix. Microanaly-
ses were carried out by the microanalytical laboratory at
the National University of Singapore. The preparation
of cluster 1 appears in our earlier report [10]. All other
reagents were from commercial sources and used as
supplied.
Ru
Ru
Ru
Ru
Os
H
Os
H
+
+
Os
Os
Os
Os
Os
H
Os
Os
4
3
5
-2CO
+1
4.2. Reaction of 1 with indene
Scheme 1.
To a Carius tube containing 1 (22.6 mg, 0.022 mmol)
and cyclohexane (30 mL) was added indene (0.5 mL).
The reaction mixture was degassed by three freeze–
pump–thaw cycles, and stirred at 120 ꢁC for 12 h. Solvent
was removed under reduced pressure, and the residue so
obtained was redissolved in the minimum volume of
dichloromethane and chromatographed on TLC plates.
Elution with hexane/dichloromethane (7:3, v/v) yielded
four bands. The first and second bands were identified
from their infrared spectra as 2 (1.7 mg) and unreacted
1 (3.4 mg), respectively.
rearrangement, via a Berry pseudo-rotation, to place the
fragment in an equatorial position, followed by decarbony-
lation and bonding of the six-membered ring of the indenyl
moiety to the pentanuclear cluster [5].
3. Concluding remarks
We have thus shown that cluster 1 reacts readily with
indene, initially to form 3. The latter subsequently frag-
ments to afford an Ru(g5-C9H7) fragment which can then
undergo capping reaction with 1 to give 5, which exists
as mixture of two non-interconverting isomers in solution.
Decarbonylation of 3 to form 4 appears not to be favoured.
Clusters 4 and 5 exhibit the novel l3,g5:g2:g2 bonding
mode for the indenyl moiety.
Band 3 (Rf = 0.44) afforded dark brown crystals of 3.
Yield = 7.1 mg, 35%. IR (CH2Cl2) v(CO): 2088 m, 2062
ms, 2033 s, 2005 m, 1950 w(br), 1835 w(br) cmÀ1
NMR (300 K): d 7.52 (d, 2H, JHH = 2.6 Hz), 7.30 (d,
.
1H
3
3
3
2H, JHH = 2.6 Hz), 5.49 (d, 2H, JHH = 2.5 Hz), 4.23
3
(dd, 1H, JHH = 2.5 Hz), À21.66 (s, br, 1H, OsHOs). MS
(FAB): m/z 1096 (M+), calcd for M+: 1096. Calcd for
C20H8O11Os3Ru.0.25C6H14: C, 23.11; H, 1.04. Found: C,
22.78; H, 0.70%. Presence of hexane in the analytical sam-
4. Experimental
1
4.1. General procedures
ple was verified by H NMR spectroscopy.
Band 4 (Rf = 0.12) afforded a mixture of red and black
crystals, which had to be separated by hand. The red crys-
tals were identified to be 4. Yield = 1.7 mg, 9%. IR
All reactions and manipulations were carried out under
nitrogen by using standard Schlenk techniques. Solvents

772
Y.L.K. Tan, W.K. Leong / Journal of Organometallic Chemistry 692 (2007) 768–773
1
(CH2Cl2) v(CO): 2068 s, 2022 s cmÀ1. H NMR (300 K): d
5.67 (m, 1H), 5.17 (m, 2H), 4.83 (m, 2H), 4.17 (m, 2H),
À15.48 (s, 1H, OsHOs). MS (FAB): m/z 1039 (M+), calcd
for M+: 1040.
4.4. Reaction of 1 and 3
To a Carius tube containing cyclohexane (20 mL) was
added 1 (8.1 mg, 0.008 mmol) and 3 (6.4 mg, 0.006 mmol).
The reaction mixture was degassed by three freeze–pump–
thaw cycles, and stirred at 120 ꢁC for 4 h. Subsequent treat-
ment as above yielded four bands which were identified as 2
(1.5 mg), unreacted 1 (1.3 mg), unreacted 3 (2.7 mg) and 5
(2.3 mg), respectively.
The black crystals were identified to be 5.
Yield = 5.3 mg, 24%. IR (CH2Cl2) v(CO): 2077 w, 2069
w, 2030 m, 2003 s, 1975 w, 1935 vw cmÀ1. H NMR: d
1
3
3
5.68 (dd, 1H, JHH = 3.0 Hz, JHH = 3.0 Hz), 5.07 (dd,
3
3
2H, JHH = 4.1 Hz, JHH = 2.5 Hz), 4.70 (dd, 2H,
3JHH = 4.1 Hz), 4.29 (d, 2H, JHH = 3.0 Hz), À11.92 (s,
2
1H, RuHOs) [major isomer]; 5.78 (dd, 1H,3JHH = 3.0 Hz,
4.4.1. X-ray crystal structure determinations
3JHH = 3.0 Hz), 5.45 (d, 1H, JHH = 5.9 Hz), 5.22 (dd,
Crystals were mounted on quartz fibres. X-ray data were
collected on a Bruker AXS APEX system, using Mo Ka
radiation, at 223 K with the SMART suite of programs
[11]. Data were processed and corrected for Lorentz and
polarisation effects with SAINT [12], and for absorption
effects with SADABS [13]. Structural solution and refinement
were carried out with the SHELXTL suite of programs [14].
Crystal and refinement data are summarised in Table 1.
The structures were solved by direct methods to locate
the heavy atoms, followed by difference maps for the light,
non-hydrogen atoms. The hydrides in 3 and 4 were located
via low angle difference maps; they were refined freely,
except that the hydride for 4 was given a fixed isotropic ther-
mal parameter. The hydrides for 5 were placed by potential
energy calculations with the program XHYDEX [15], given
fixed isotropic thermal parameters, and refined riding on
the osmium atom to which they we both attached. Organic
hydrogen atoms were placed in calculated positions and
refined with a riding model. All non-hydrogen atoms were
generally given anisotropic displacement parameters in the
final model. Cluster 5 exhibited disorder of the heavy atom
3
3
3
1H, JHH = 5.9 Hz, JHH = 5.1 Hz), 4.90 (dd, 1H,
3JHH = 5.9 Hz,
3JHH = 5.1 Hz),
4.01
(d,
1H,
3JHH = 3.0 Hz), 3.91 (d, 1H, JHH = 5.9 Hz), 3.89 (d, 1H,
2JHH = 3.0 Hz), À14.67 (s, 1H, RuHOs) [minor isomer].
MS (FAB): m/z 1196 (M+), calcd for M+: 1197. Calcd
for C20H8O11Os3Ru2.0.5C6H14: C, 22.26; H, 1.21. Found:
C, 22.10; H, 1.14%. Presence of hexane in the analytical
3
1
sample was verified by H NMR spectroscopy.
Decreasing the reaction time to 8 h resulted in the isola-
tion of 2 (1.5 mg), 1 (8.4 mg), 3 (8.3 mg, 55%) and 5
(1.9 mg, 12%), respectively.
4.3. Thermolysis of 3
To a Carius tube containing cyclohexane (20 mL) was
added 3 (7.3 mg, 0.007 mmol). The reaction mixture was
degassed by three freeze–pump–thaw cycles, and stirred
at 120 ꢁC for 6 h. Subsequent treatment as above yielded
two bands which were identified as Os3(CO)12 (2.6 mg)
and unreacted 3 (2.8 mg), respectively.
Table 1
Crystal and refinement data for 3–5
Identification code
3
4
5
Empirical formula
Formula weight
Crystal system
Space group
C
20H8O11Os3Ru
C18H8O9Os3Ru
1039.91
Monoclinic
P21/c
C20H8O11Os3Ru2
1197.00
Monoclinic
P21/c
1095.93
Monoclinic
P21/c
˚
a (A)
8.7050(2)
14.5480(3)
8.9654(2)
9.968(4)
15.047(6)
13.743(5)
14.1415(5)
9.3128(3)
17.2702(6)
˚
b (A)
˚
c (A)
b (ꢁ)
Volume (A )
91.0210(10)
1135.20(4)
2
3.206
17.448
96.688(7)
2047.2(13)
4
3.374
19.333
95.5620(10)
2263.72(13)
4
3.512
18.142
3
˚
Z
qc (Mg/m3)
l (mmÀ1
F(000)
)
976
1840
2128
Crystal size (mm3)
0.38 · 0.24 · 0.16
2.27 to 30.51
10492
0.19 · 0.12 · 0.10
2.01 to 26.37
28437
0.12 · 0.08 · 0.06
2.37 to 26.37
31158
Theta range for data collection, deg
Reflections collected
Independent reflections [R(int)]
Maximum and minimum transmission
Data/restraints/parameters
Goodness-of-fit on F2
3410 [0.0314]
0.1667 and 0.0578
3410/0/169
1.106
4187 [0.0405]
0.2480 and 0.1203
41877/0/283
1.067
4635 [0.0383]
0.4090 and 0.2194
4635/3/332
1.089
Final R indices [I > 2r(I)]
R indices (all data)
Largest difference in peak and hole, e A
R1 = 0.0272, wR2 = 0.0650
R1 = 0.0305, wR2 = 0.0662
1.343 and À2.503
R1 = 0.0271, wR2 = 0.0615
R1 = 0.0335, wR2 = 0.0639
2.816 and À1.023
R1 = 0.0354, wR2 = 0.0897
R1 = 0.0388, wR2 = 0.0914
2.472 and À3.338
À3
˚

Y.L.K. Tan, W.K. Leong / Journal of Organometallic Chemistry 692 (2007) 768–773
773
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Crystallographic data (excluding structure factors) for
the structures in this paper have been deposited with the
Cambridge Crystallographic Data Centre. CCDC 620444,
620445 and 620446 contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free
of charge via http://www.ccdc.cam.ac.uk/conts/retriev-
ing.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
(+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
Acknowledgements
This work was supported by the National University of
Singapore (Research Grant No. R143-000-267-112) and
one of us (Y.L.K.T.) thanks the University for a Research
Scholarship.
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