Raft-like osmium- and ruthenium-antimony carbonyl clusters This article is dedicated to the late Lord Lewis of Newnham.

Article abstract of DOI:10.1016/j.jorganchem.2015.06.007

The higher nuclearity raft-like cluster Os₆(CO)₂₀(μ-SbPh₂)₂, 5-Os, was isolated from the base hydrolysis of Os₃(CO)₁₁(SbPh₂Cl), 1-Os. The ruthenium analogue, viz., Ru₆

Full text of DOI:10.1016/j.jorganchem.2015.06.007

Journal of Organometallic Chemistry xxx (2015) 1e9
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Raft-like osmium- and ruthenium-antimony carbonyl clusters
Ying-Zhou Li, Weng Kee Leong*
Division of Chemistry & Biological Chemistry, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
a r t i c l e i n f o
a b s t r a c t
Article history:
The higher nuclearity raft-like cluster Os6(CO)20
Os3(CO)11(SbPh2Cl), 1-Os. The ruthenium analogue, viz., Ru6(CO)20(m
the reduction of Ru3(CO)12, 7-Ru, with the benzophenone ketyl radical followed by treatment with
SbPh2Cl. These clusters undergo facile ligand substitution reactions with two-electron donors to afford
(
m
-SbPh2)2, 5-Os, was isolated from the base hydrolysis of
-SbPh2)2, 5-Ru, was obtained from
Received 15 May 2015
Received in revised form
4 June 2015
Accepted 6 June 2015
Available online xxx
the mono- and disubstituted derivatives M6(CO)20-n
(
m
-SbPh2)2(L)n, (M ¼ Ru or Os; n ¼ 1 (8) or 2 (9);
t
L ¼ PMe3 (a), PPh3 (b), or BuNC (c)).
This article is dedicated to the late Lord
Lewis of Newnham.
© 2015 Elsevier B.V. All rights reserved.
Keywords:
Raft-like clusters
Higher nuclearity carbonyl clusters
Osmium
Ruthenium
Antimony
1. Introduction
main group metal or metalloid include several with Ge or Sn, ob-
tained via the addition of germylene [5] or Ph3MH (M ¼ Ge or Sn)
[6], to M3(CO)12 (M ¼ Os or Ru), or via the pyrolysis of low-
nuclearity osmium [7], or ruthenium [8], clusters containing Ge
ligands; these cluster tend to be planar.
We have been investigating synthetic routes to osmium-
antimony clusters [9], and serendipitously uncovered the almost
planar, raft-like, higher nuclearity clusters M6(CO)20(m-SbPh2)2, 5-
A great number of high nuclearity homo- or heterometallic
Group 8 metal carbonyl clusters have been reported but most of
them adopt three-dimensional, polyhedral configurations, such as,
the (distorted) octahedron (for hexanuclear clusters) and more
complex polyhedra (for heptanuclear and higher nuclearity clus-
ters). Two-dimensional planar or quasi-planar (raft-like), higher
nuclearity clusters containing six or more metal atoms are rela-
tively rare. They usually show distinct physical and reactivity
properties [1] including some which show interesting magnetic
properties [2].
To our knowledge, the only high-nuclearity homometallic
osmium clusters with almost planar metal cores are
Os6(CO)21ꢀn(NCCH3)n, (n ¼ 0, 1 or 2), and their several phosphine,
acetylene, or 2-aldrithiol substitution derivatives [3]; ruthenium
analogues are unknown. Heterometallic examples containing
osmium or ruthenium include a number of clusters of the general
formulae M3(CO)12[M0(L)]n (M ¼ Os or Ru; M0 ¼ Pd or Pt; L ¼ PtBu3
or NHC; n ¼ 1e3) [1c,4]. The metal cores in the latter group of
clusters are rather distorted from planarity and have been referred
to simply as “two-dimensional” clusters. Examples containing a
M (where M ¼ Os or Ru). Our study into their formation and
their substitution chemistry is reported here.
2. Results and discussion
Oxidative addition of the SbeCl bond in SbPh2Cl to
Os3(CO)11(NCCH3) occurs via the substitution product
Os3(CO)11(SbPh2Cl), 1-Os, to eventually form Os3(CO)11(m-
SbPh2)(Cl), 2-Os [10]. During our investigations into the conversion
of 1-Os to 2-Os, we found that the addition of H2O and Na2CO3
afforded the previously reported clusters 2-Os, 3-Os and 4-Os, and
two other clusters, one of which is the new raft-like, higher
nuclearity cluster Os6(CO)20(m-SbPh2)2, 5-Os (Scheme 1).
Cluster 5-Os is stable under ambient conditions over several
months and has been fully characterized, including by an X-ray
crystallographic analysis. An ORTEP plot depicting its structure is
given in Fig. 1. The other unidentified product 6-Os was found to
* Corresponding author.
E-mail address: chmlwk@ntu.edu.sg (W.K. Leong).
http://dx.doi.org/10.1016/j.jorganchem.2015.06.007
0022-328X/© 2015 Elsevier B.V. All rights reserved.
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Y.-Z. Li, W.K. Leong / Journal of Organometallic Chemistry xxx (2015) 1e9
Scheme 1. Base hydrolysis of Os3(CO)11(SbPh2Cl), 1-Os.
gradually convert to 5-Os, especially in a polar solvent such as
MeOH, as was evident by monitoring the conversion through 1H
NMR spectroscopy (see Supplementary data Fig. S3). Its HRMS
basic conditions employed. Based on these observations, the pro-
posed reaction pathways to all the products are as given in Scheme
2.
spectrum showed
Supplementary data Fig. S22(a) and (b)), suggesting that it was
probably an isomer.
We have also carried out some studies into the reaction pathway
in the hope of increasing the yield of 5-Os. As mentioned above, we
have shown earlier that 2-Os resulted from oxidative addition of
the SbeCl bond in 1-Os [20]. Cluster 4-Os was presumably the
result of reaction of 3-Os with SbPh2Cl, generated from 1-Os via
ligand dissociation or decomposition [11]. On monitoring the base
hydrolysis of 1-Os (in d-THF) by 1H NMR spectroscopy, four metal
a
similar pattern to that of 5-Os (see
It is suggested that 3-Os is formed via two competitive path-
ways (I and II), through 2-Os or the intermediate A. Presumably,
there are two possible isomers of A, corresponding to the different
relative orientation of the SbPh2Cl and the terminal H ligands;
oxidative addition of the SbeCl bond across an OseOs bond in one
leads to B and further on to 3-Os via a chloride elimination, while
the other leads to C and further on to an electron-deficient cluster D
via a similar pathway. This latter quickly converts to 5-Os and 6-Os
through further elimination of H2 and CO.
The metal hydride resonances at
d
¼ ꢀ8.27 and ꢀ8.97 ppm may
hydride resonances (
observed after 8 h (see Supplementary data Fig. S5).
d
¼ ꢀ8.72, ꢀ8.27, ꢀ8.97 and ꢀ9.19 ppm) were
thus be assigned to B (and its isomer with the opposite orientation
of H) and the other two resonances observed in the reaction of 1-Os
may be assigned to A and/or C. We have observed through 1H NMR
monitoring of these resonances that the conversion of B to 3-Os (in
the hydrolysis of 2-Os) was more favourable in DCM; the conver-
sion did not occur in THF/H2O even after 72 h but upon removal of
the solvents and re-dissolution in DCM, the conversion was com-
plete within 5 min. A similar observation was made for the con-
version of C to 5-Os and 6-Os (in the hydrolysis of 1-Os). These
observations are consistent with the more favourable elimination
of NaCl (as depicted in the proposed pathways) in DCM than in THF/
Treatment of 2-Os under the same reaction conditions gave 3-
Os as the sole separable product in a much higher yield (ca. 75%),
albeit with a much longer reaction time (ca. 72 h) for completion
[12]; no 5-Os was observed. This suggested that the formation of 5-
Os (and 6-Os) followed a different reaction pathway from that for
clusters 2-Os to 4-Os. The 1H NMR spectrum of this latter reaction
showed only two metal hydride resonances
(
d
¼ ꢀ8.27
and ꢀ8.97 ppm) after 24 h (see Supplementary data Fig. S4). These
hydride species probably resulted from a Hieber reaction under the
Fig. 1. ORTEP plot of the molecular structure of 5-Os (one of two asymmetrical molecules) with thermal ellipsoids at the 50% probability level. Organic hydrogen atoms have been
omitted for clarity.
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Y.-Z. Li, W.K. Leong / Journal of Organometallic Chemistry xxx (2015) 1e9
3
Scheme 2. Proposed reaction pathways for the base hydrolysis of 1-Os.
H2O, which helps drive the conversion towards completion.
It has been pointed out that the chemical shifts of the metal
hydride resonances may not be a reliable guide to the nature of the
hydrides (terminal vs bridging) [13,14]. We have attempted to
verify our assignments of the resonances to terminal metal hy-
drides through a GIAO calculation; the calculated terminal hydride
resonances for AeC ranged from ꢀ6.28 to ꢀ8.32, in fairly good
agreement with the experimental values (see Supplementary data
Table S2). We have also attempted to optimize alternative struc-
tures of these intermediates with bridging hydride ligands but
were unsuccessful; the final optimized structures all adopted ter-
minal hydrides.
The two competitive pathways I and II for the hydrolysis of 1-Os
also account for the lower reaction rate and higher yield observed
in the hydrolysis of 2-Os; the lower yield of 3-Os from 1-Os via
pathway II may be accounted for by the attack of OHꢀ on the
SbPh2Cl ligand in 1-Os, leading to other side-products. Our
computational study using density functional theory gives the
Gibbs' free energies for steps III and IV to be about ꢀ72 and ꢀ40 kJ/
mol, respectively. Unlike A and B, the two likely isomers for C have a
significantly large difference in energy; the value given here is for
the reaction to the more stable isomer. This suggests that pathway
III is thermodynamically more favourable than IV, and may account
for the higher yield of 3-Os compared to that of 5-Os and/or 6-Os.
Attempts at increasing the yields of 5-Os and/or 6-Os through the
use of different bases (NaOH or KOH) were unsuccessful.
destruction of the ketyl radical by the SbPh2Cl. Surprisingly, treat-
ment of 7-Ru with a stoichiometric amount of the ketyl radical
followed by the addition of excess SbPh2Cl afforded the ruthenium
analogue of 5-Os, viz. Ru6(CO)20(m-SbPh2)2, 5-Ru, in moderate yield
(Scheme 3). The reaction time for the first step had to be kept short
(~15 min) in order to avoid the over-reduction of 7-Ru to divalent
anionic species [16], and the second step was essentially instanta-
neous; prolonged stirring led to a reduced yield. An attempt at
extending this methodology for the synthesis of 5-Os failed,
probably due to the lower reactivity of Os3(CO)12 towards the ketyl
radical.
Cluster 5-Ru is not stable in coordinating solvents such as
methanol and THF, but is relatively stable in DCM under ambient
conditions; there were no signs of decomposition over several days.
It has been fully characterized, including by single-crystal X-ray
diffraction studies on two different crystals, with one being a sol-
vate. The ORTEP plot from the non-solvate, depicting its molecular
structure, is shown in Fig. 2.
2ꢀ
It is known that 7-Ru can be reduced to [Ru6(CO)18
]
or
2ꢀ
[Ru3(CO)11
]
with one or two equivalents of the ketyl radical,
2ꢀ
respectively [16,17], and it has been suggested that [Ru6(CO)18
came from the further reaction of [Ru3(CO)11
]
2ꢀ
]
with 7-Ru,
although there has been little mechanistic information on this. The
possibility that 5-Ru was formed from an Ru6 carbonyl species,
possibly a precursor to [Ru6(CO)18
]
2ꢀ, was ruled out as the reaction
2ꢀ
of [Ru3(CO)11
]
(prepared in accordance with the literature
Our attempt at preparing a ruthenium analogue to 5-Os through
a similar procedure was unsuccessful because the synthesis of
Ru3(CO)11(SbPh2Cl), 1-Ru, via the reaction of Ru3(CO)11(NCCH3)
with SbPh2Cl in various solvents (DCM, THF or CH3CN) failed;
decomposition was rapid even at 0 ꢁC, with only small amounts of
Ru3(CO)12, 7-Ru, being recovered. Radical-initiated substitution in
7-Ru with benzophenone ketyl had been shown to be stoichio-
metrically specific and occurred under mild conditions [15]. Our
attempt at the substitution of 7-Ru with SbPh2Cl using catalytic
amount of the ketyl radical failed, however, presumably due to
method) with one equivalent of 7-Ru (to form the higher nucle-
arity, anionic cluster in situ), followed by SbPh2Cl, afforded no
identifiable product.
We believe that radical-initiated substitution in 7-Ru did occur
according to the pathway established by Bruce (Scheme 4) [15b],
i.e., an initial single electron transfer to 7-Ru to form the radical
anion E followed by a ligand addition to F. In the case of tri-
organophosphanes, -arsanes and -stibanes, that is followed by loss
of a CO and electron-transfer, resulting in overall radical-catalysed
ligand substitution. In our case, however, a stoichiometric amount
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Y.-Z. Li, W.K. Leong / Journal of Organometallic Chemistry xxx (2015) 1e9
Scheme 3. Reaction of 7-Ru with SbPh2Cl in the presence of ketyl radical.
Fig. 2. ORTEP plot of the molecular structure of 5-Ru with thermal ellipsoids at the 50% probability level. Organic hydrogen atoms have been omitted for clarity.
Scheme 4. Proposed formation pathway to 5-Ru.
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Y.-Z. Li, W.K. Leong / Journal of Organometallic Chemistry xxx (2015) 1e9
5
t
of the ketyl radical was required and was added to 7-Ru prior to the
addition of SbPh2Cl. This indicated that the ketyl radical acted as a
reducing agent rather than as a catalyst. From F, the reaction
probably proceeded via chloride elimination and formation of an
RueSb bond to the 17-electron intermediate G, which then
dimerised to 5-Ru through a decarbonylation. Attempts at trapping
one or more of the radical intermediates with TEMPO afforded
unidentified mixtures.
The electronic spectrum (DCM solution) of 5-Os exhibited two
absorption bands at 488 nm and 572 nm, while that for 5-Ru were
at 565 nm and 678 nm (see Supplementary data Fig. S11), sug-
gesting that 5-Ru has a smaller HOMO-LUMO gap, and may thus be
more readily attacked by nucleophiles. Experimentally, both reac-
ted with two-electron donors to afford substituted derivatives
(Scheme 5). The reaction with t-butylisonitrile was significantly
faster, and only the mono-substituted derivative was isolated; at-
tempts at obtaining more highly substituted products afforded a
complex mixture. Both mono- and di-substituted derivatives were
obtained for the phosphanes, and these did not undergo further
substitution.
The monosubstituted derivatives 8 are soluble in most organic
solvents but are unstable in coordinating solvents, while the
disubstituted derivatives 9 are poorly soluble. The molecular
structures of 8b-Ru, 9a-Os, 9b-Ru and 8c-Ru have been charac-
terized by single-crystal diffraction studies, although the data
quality for the latter two were poor but sufficient to allow unam-
biguous determination of the heavy atom positions; the ligand
positions are less clear. The ORTEP plots depicting the molecular
structures of 8b-Ru and 9a-Os are given in Figs. 3 and 4,
respectively.
positions while BuNC occupies the axial position [18]. While the
PPh3 ligands in 8b-Ru and 9b-Ru occupy equatorial positions cis to
the adjacent antimony, the two PMe3 ligands in 9a-Os adopt trans
configurations with respect to their corresponding adjacent anti-
mony atoms; it is unclear why this is so. The electronic spectra of
these derivatives show that the main absorption maxima of 8a-Os
and 9a-Os (585 nm and 598 nm, respectively) are red-shifted with
respect to that for 5-Os (see Supplementary data Fig. S11). This is
also the case with 5-Ru; the main absorption maxima of 8b-Ru and
9b-Ru are red-shifted to 570 nm and 575 nm, respectively. These
red shifts presumably point to a decrease in the HOMO-LUMO gap
with stronger electron-donors in equatorial positions.
3. Crystallographic discussion
Selected bond parameters for 5-Os and 5-Ru, and their
substituted derivatives 8b-Ru and 9a-Os, are collected in Table 1.
There are two independent molecules in the asymmetric unit of 5-
Os, with each molecule located at an inversion centre. For 5-Ru, a
THF solvate (5-Ru·THF) was also obtained. All the clusters have a
valence electron count of 94, which is consistent with the seven
OseOs or RueRu bonds observed. The M6Sb2 cluster cores are all
fairly planar; the maximum deviation from the metal plane in 5-Os
was <0.05 Å, slightly larger (0.15e0.18 Å) in 5-Ru, and slightly
larger still upon substitution (0.14 Å and 0.32 Å for 9a-Os and 8b-
Ru, respectively). As mentioned earlier, the several homometallic
Ru carbonyl clusters with two-dimensional metal cores which have
been reported prior to this work either exhibited large deviations
from planarity [19], or were supported by ancillary ligands on one
side of that (quasi-)plane [19a,b,h]. The Ru6Sb2 clusters here
represent the first truly raft-like clusters of ruthenium not struc-
turally supported by ancillary ligands.
Substitution appears to favour an “outer” ruthenium atom, i.e.,
the “spike” atom with respect to the transition metal framework. As
expected on the basis of homometallic osmium and ruthenium
cluster chemistry, the phosphanes tend to occupy equatorial
The central M4 tetrametallic unit tend to be associated with the
shortest (M2-M3 and M5-M6) and the longest (M2-M6 and M3-
Scheme 5. Reaction of clusters 5 with two-electron donors.
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Y.-Z. Li, W.K. Leong / Journal of Organometallic Chemistry xxx (2015) 1e9
Fig. 3. ORTEP plot of the molecular structure of 8b-Ru. Thermal ellipsoids are drawn at the 50% probability level. Organic hydrogen atoms have been omitted for clarity.
M5) metalemetal bond lengths. As has already been pointed out,
group 15 ligand substitution tends to lengthen the MeM bond cis to
it [15d,20]. Among the MꢀSb bonds, those trans to an MeM bond
are shorter than those trans to a CO or PR3. We had earlier advo-
cated considering the metal-carbonyl bond in terms of the sum of
the MꢀC and CeO bond lengths rather than either of the individual
bond parameters [10]. As expected, the metal-carbonyl bond
lengths associated with equatorial CO ligands are shorter than
those for the axial CO ligands, with a clear gap (>0.01 Å) between
their ranges. The exception are for the equatorial CO ligands trans to
an Sb atom (M-CO(trans)), which tend to lie within the range for the
axial carbonyls, indicating that the SbPh2 group has a strong trans
influence.
5. Experimental section
5.1. General data
All manipulations were carried out in an argon atmosphere with
standard Schlenk techniques. Reagent grade solvents were dried by
the standard procedures and were freshly distilled prior to use. The
ketyl radical (ca. 0.025 M) was prepared according to the literature
method [15b]. Compounds SbPh2Cl [21], and Os3(CO)11(NCCH3)
[22], were prepared as described in the literature. TLC separations
were carried out on 20 ꢂ 20 cm2 plates coated with silica gel 60
F254, from Merck. NMR spectra were recorded on a JEOL ECA-
400 MHz NMR spectrometer. 1H and 13C{1H} chemical shifts were
referenced to the residual resonances of the respective deuterated
solvents; 31P{1H} chemical shifts were referenced to external 85%
aqueous H3PO4. Mass spectra were recorded in electrospray ioni-
zation (ESI) mode on a Waters Q-Tof Premier mass spectrometer.
Elemental analyses were carried out in-house. Electronic spectra
were recorded on a Perkin Elmer Lambda 900 spectrometer as DCM
solutions.
4. Concluding remarks
In this study, we reported the synthesis and characterization of
two higher nuclearity, raft-like, M6Sb2 (M ¼ Ru or Os) clusters.
These were obtained via two very different synthetic routes, and
reaction pathways leading to their formation were proposed. These
raft-like clusters readily underwent ligand substitution with two-
t
electron donors, exemplified by PPh3, PMe3 and BuNC. Remark-
5.2. Preparation of 5-Os
ably, ligand substitution did not appear to induce any significant
distortion in the structures.
Os3(CO)11(NCCH3) (40 mg, 43 mmol) was dissolved in dry THF
Fig. 4. ORTEP plot of the molecular structure of 9a-Os. Thermal ellipsoids are drawn at the 30% probability level. Organic hydrogen atoms have been omitted for clarity.
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Y.-Z. Li, W.K. Leong / Journal of Organometallic Chemistry xxx (2015) 1e9
7
Table 1
Common atom-labelling scheme and selected bond lengths (Å) and angles (deg) for 5-Os, 5-Ru, 8b-Ru and 9a-Os.
5-Os
5-Ru
5-Ru∙THF
8b-Ru
9a-Os
M ¼ Os; L1 ¼ L2 ¼ L3 ¼ L4 ¼ CO
Molecule 1; molecule 2
M ¼ Ru; L1 ¼ L2 ¼ L3 ¼ L4 ¼ CO
M ¼ Ru; L1 ¼ L2 ¼ L3 ¼ CO;
L4 ¼ PPh3;
M ¼ Os; L1 ¼ L3 ¼ PMe3;
L2 ¼ L4 ¼ CO
M1eM2
M2eM3
M2eM6
M3eM6
M3eM5
M4eM5
M5eM6
M1eSb2
2.9295(5); 2.9293(4)
2.8736(5); 2.9293(4)
2.9325(4); 2.9364(4)
2.8903(7); 2.9142(6)
2.9325(4); 2.9364(4)
2.9295(5); 2.9293(4)
2.8736(5); 2.9293(4)
2.6579(7); 2.6594(6)
2.6225(7); 2.6272(6)
2.6579(7); 2.6594(6)
2.6225(7); 2.6272(6)
3.074e3.099; 3.073e3.093
3.019e3.044; 3.024e3.057
3.083; 3.088
2.9080(5)
2.8730(5)
2.9230(5)
2.9352(7)
2.9230(5)
2.9080(5)
2.8730(5)
2.6507(5)
2.6168(5)
2.6507(5)
2.6168(5)
3.070e3.091
3.011e3.059
3.097
2.9274(5)
2.8938(5)
2.9166(5)
2.8767(5)
2.9594(5)
2.9097(5)
2.8476(5)
2.6396(5)
2.6124(5)
2.6579(5)
2.5976(5)
3.074e3.095
3.011e3.069
3.090, 3.095
e
2.939(6)
2.860(5)
2.922(6)
2.909(6)
2.920(6)
2.914(5)
2.852(5)
2.663(6)
2.642(5)
2.655(5)
2.612(5)
3.057e3.105
3.004e3.042
3.082
2.9564(5)
2.8885(5)
2.9420(5)
2.9085(6)
2.9420(5)
2.9564(5)
2.8885(5)
2.6452(6)
2.6302(5)
2.6452(6)
2.6302(5)
3.068e3.085
3.013e3.038
e
M3eSb1
M4eSb1
M6eSb2
MeCO(ax)a
MeCO(eq)a
MeCO(trans)a,b
MeP
e
e
2.373(13)
0.225 (0.322)
2.392(2)
0.137 (0.156)
Mean (maximum) deviation
of metal core (Å)
0.036 (0.040); 0.049 (0.050)
0.149 (0.154)
0.166 (0.185)
a
Sum of MꢀC and CeO bond lengths.
b
Equatorial CO trans to Sb.
(14 ml) followed by the addition of SbPh2Cl (14 mg, 45
mmol). The
(1C), 166.07 (1C), d (Ph) 134.70, 130.33, 129.18, 125.82 ppm. Anal.
resulting yellow mixture was stirred at room temperature for 12 h;
the IR spectrum showed the formation of 1-Os and depletion of
Os3(CO)11(NCCH3). To the reaction mixture, Na2CO3 (30e50 mesh,
Calcd for C44H20O20Os6Sb2: C 23.45, H 0.89. Found: C 23.51, H 0.60.
ESI-MSþ (m/z): 2254 [M þ H]þ, 2149 [M þ H-CO-Ph]þ.
Band 5, very light yellow, was identified as Os3(CO)11(Cl)(
SbPh2), 2-Os. Rf ¼ 0.30. Yield ¼ 1.0 mg (2.0%).
m-
4.7 mg, 44 mmol) and deionized water (0.70 ml) were added and
stirred at room temperature for another 6 h, leading to an orange
solution. The solvents were then removed in vacuo to give a bluish
yellow residue. Redissolution in dry DCM (10 ml) and stirring for
another 0.5 h afforded a bluish yellow solution. Removal of the
solvent followed by separation of the residue by TLC, with DCM/
hexane (1:1, v/v) as the eluent, gave several bands.
5.3. Reaction of 5-Os with PMe3
Cluster 5-Os (12 mg, 5.3
dissolved in dry DCM (10 ml) and the mixture maintained at 0 ꢁC. A
solution of TMNO in dry CH3CN (0.80 ml, 10.6 mol) was added
mmol) and PMe3 (1.5 mg, 20 mmol) were
m
Band 1, yellow, was identified as Os3(CO)10
Rf ¼ 0.70. Yield ¼ 14 mg (28%).
(
m
-H)(
m
-SbPh2), 3-Os.
dropwise. The resulting light purple solution turned a darker blue
after stirring for 6 h, after which the solution was allowed to warm
up to room temperature and stirred for another 72 h. The solvents
were then removed by rotary evaporator and the residue separated
on silica TLC with DCM/Hexane (3:2, v/v) as eluent, giving two
separable bands.
Band 2, light yellow, was identified as Os3(CO)10
Os. Rf ¼ 0.55. Yield ¼ 2.0 mg (7.0%).
(m-SbPh2)2, 4-
Band 3, green, was 6-Os the identity of which has not been
established. Rf ¼ 0.45. Yield ¼ 2.5 mg. IR (CH2Cl2):
n(CO) 2117w,
2101s, 2060sh, 2037s, 2017w, 1990w, 1969w cmꢀ1; 1H NMR (C6D6)
Band 1, blue, afforded 8a-Os as the minor product. Rf ¼ 0.65.
d
7.76 (d, 4H, PhH), 7.69 (d, 4H, PhH), 6.90e7.05 (dd,12H, PhH) ppm.
Yield ¼ 1.0 mg (8.2%). IR (CH2Cl2):
n(CO) 2111m, 2077s, 2044sh,
ESI-MSþ (m/z): 2254 [M þ H]þ, 2177 [M þ H-Ph]þ, 2149 [M þ H-CO-
2033sh, 2027vs, 2002s, 1981w, 1975w, 1965w cmꢀ1 1H NMR
.
Ph]þ.
(MeOD): d 7.45e7.50 (m, 8H, Ph), 7.31e7.43 (m, 12H, Ph), 1.34 (s, 9H,
Band 4, purple, was identified as Os6(CO)20
(m-SbPh2)2, 5-Os.
CH3) ppm; 31P{1H} NMR (C6D6)
d
ꢀ60.98 (s) ppm. ESI-MSþ (m/z):
Rf ¼ 0.40. Yield ¼ 2.5 mg (5.0%). IR (CH2Cl2):
n(CO) 2118w, 2105s,
2303 [M þ H]þ.
2038s, 2014w, 1993m, 1971w cmꢀ1. 1H NMR (CD2Cl2)
d
d
7.50 (dd, 8H,
7.60 (dd, 8H,
Band 2, greenish blue, afforded 9a-Os as the major product.
PhH), 7.39e7.44 (m, 12H, PhH) ppm; 1H NMR (C6D6)
Rf ¼ 0.50. Yield ¼ 9.0 mg (72%). IR (CH2Cl2):
2005vs, 1975w, 1965w, 1923w cmꢀ1. 1H NMR (CD2Cl2):
(m, 8H, Ph), 7.54e7.56 (m, 12H, Ph), 1.33 (s, 18H, CH3) ppm; 31P{1H}
n
(CO) 2056m, 2021w,
PhH), 6.87e6.97 (m, 12H, PhH) ppm. 13C{1H} NMR (CD2Cl2):
d
(CO)
d
7.69e7.71
197.12 (2C), 185.02 (2C), 184.61 (1C), 179.63 (1C), 173.44 (2C), 172.65
Please cite this article in press as: Y.-Z. Li, W.K. Leong, Journal of Organometallic Chemistry (2015), http://dx.doi.org/10.1016/
j.jorganchem.2015.06.007

8
Y.-Z. Li, W.K. Leong / Journal of Organometallic Chemistry xxx (2015) 1e9
NMR (C6D6)
d
ꢀ33.68 (s) ppm. Anal. Calcd for C48H38O18P2Os6Sb2: C
afford two main bands.
24.54, H 1.63. Found: C 24.54, H 1.20. ESI-MSþ (m/z): 2350 [M þ H]þ.
5.4. Preparation of 5-Ru
Band 1, blue-purple, was identified as unreacted 5-Ru (5 mg).
Band 2, blue-purple, afforded 8c-Ru as the major product.
Rf ¼ 0.60. Yield ¼ 8.0 mg (52% based on consumed 5-Ru). IR
(CH2Cl2):
n(NC) 2193w, 2173w;
n
(CO) 2103m, 2073s, 2031vs,
The cluster Ru3(CO)12, 7-Ru (40 mg, 62
dry THF (8 ml). To this was added the ketyl radical (0.025 M, 2.5 ml,
62 mol). The resulting mixture was stirred at room temperature
mmol) was dissolved in
2008w, 1991w, 1966w cmꢀ1. 1H NMR (CD2Cl2)
7.5e7.58 (m, 6H, PhH), 7.33e7.40 (m, 12H, PhH), 1.11 (s, 9H, Bu)
ppm. 13C{1H} NMR (CD2Cl2):
(CO) 218.83 (1C), 218.55 (1C), 218.24
d
7.66 (dd, 2H, PhH),
t
m
d
for 15 min during which the colour gradually changed from orange
to dark red. Then SbPh2Cl (40 mg, 0.13 mmol) was added and the
colour immediately changed to blue-purple. The reaction mixture
was stirred for another 2 min. After removing the solvent, the
residue was separated by TLC, with DCM/hexane (1:2, v/v) as the
eluent, to give two main bands.
(1C), 218.17 (1C), 215.53 (1C), 214.57 (1C), 213.97 (1C), 213.58 (1C),
201.11 (1C), 200.71 (1C),199.84 (1C),198.41 (1C),196.96 (1C),195.62
(1C), 195.57 (1C), 195.29 (1C), 194.14 (1C), 191.97 (1C), 190.50 (1C),
d
(Ph) 135.51, 135.09, 134.95, 134.89, 134.81, 133.50, 132.66, 132.17,
131.28, 129.70, 129.51, 129.39, 129.23, 129.06, 128.96, 128.88, 29.99
(C(CH3)3), 29.22 (C(CH3)3) ppm. The 13C resonance for the CNtBu
ligand was not observed, probably due to its accidental overlap
with signals of CO ligands or its low intensity probably caused by its
fluxionality or a process of dynamic loss and reattachment to Ru.
Band 1 was identified as unreacted Ru3(CO)12 (Rf ¼ 0.75;
yield ¼ 3 mg).
Band 2, blue, was identified as Ru6(CO)20(m-SbPh2)2, 5-Ru.
Rf ¼ 0.45. Yield ¼ 16 mg (30% based on consumed Ru3(CO)12). IR
(CH2Cl2): (CO) 2112w, 2096s, 2050sh, 2037s, 2016w, 1995m,
1975m cmꢀ1. 1H NMR (C6D6):
7.69 (dd, 8H, PhH), 6.90e7.00 (m,
12H, PhH) ppm; 1H NMR (CD2Cl2):
7.58 (dd, 8H, PhH), 7.41e7.44
(m, 12H, PhH) ppm; 13C{1H} NMR (CD2Cl2):
(CO) 217.56 (2C),
213.72 (2C), 199.62 (1C), 197.79 (1C), 194.99 (2C), 193.16 (1C), 189.88
(1C), (Ph) 134.89, 131.62, 129.86, 129.18 ppm. Anal. Calcd for
31P{1H} NMR (CD2Cl2)
d 32.49 (s) ppm. Anal. Calcd for
n
C48H29O19NRu6Sb2: C 32.50, H 1.65, N 0.79. Found: C 32.32, H 1.36,
d
N 0.74. ESI-MSþ (m/z): 2350 [M þ H]þ.
d
d
5.7. Crystallographic analyses
d
C
44H20O20Ru6Sb2: C 30.75, H 1.17. Found: C 31.30, H 1.38. ESI-MSþ
Diffraction-quality crystals were obtained by slow evaporation
of solutions of the clusters as follows: 5-Os (dark red) from meth-
anol/dichloromethane, 5-Ru (dark blue-purple), 8b-Ru (blue crys-
tals) and 8c-Ru (blue crystals) from dichloromethane/hexane, 5-
Ru·THF from THF/hexane, 9a-Os (green) and 9b-Ru (dark blue)
from DCM. For clusters 5-Ru, 5-Ru·THF and 8b-Ru, the X-ray
diffraction intensity data were collected on a Bruker Kappa
(m/z): 1719 [M þ H]þ.
5.5. Reaction of 5-Ru with PPh3
Cluster 5-Ru (20 mg, 12 mmol) and PPh3 (15 mg, 57 mmol) were
dissolved in dry DCM (10 ml). The resulting blue-purple solution
was stirred at room temperature for 48 h. The solution was then
concentrated (to about 5 ml) whereupon 9b-Ru precipitated out as
a greenish-blue crystalline powder, which was separated by
centrifugation, washed thrice with DCM/hexane (1:1, v/v), and air-
dried. Yield ¼ 10 mg (40% based on consumed 5-Ru). IR (CH2Cl2):
diffractometer equipped with a CCD detector, employing Mo K
radiation (
all the data were processed and corrected for Lorentz and polari-
zation effects with SAINT and for absorption effects with SADABS
[24]. For the others, intensity data was collected on a SuperNova
a
l
¼ 0.71073 Å), with the SMART suite of programs [23];
n
d
(CO) 2061s, 2040w, 2022s, 2007vs, 1962w cmꢀ1 1H NMR (C6D6)
.
(Dual source) Agilent diffractometer using either Mo
Ka
7.71 (dd, 20H, PhH), 7.12 (t,10H, PhH), 7.03 (m, 20H, PhH) ppm. 31
ꢀ33.68 (s) ppm. Anal. Calcd for
P
(l
¼ 0.71073 Å) (5-Os) or Cu K radiation ( ¼ 1.54184 Å) (9a-Os,
a
l
{1H} NMR (C6D6)
d
9b-Ru and 8c-Ru); the data was processed and corrected for ab-
sorption effects with CrysAlisPro [25]. All the structural solutions
and refinements were carried out with the SHELXTL suite of pro-
grams [26]. All non-hydrogen atoms were refined with anisotropic
thermal parameters. Crystal data, data collection parameters, and
refinement data are summarized in Table S1 (see supplementary
data).
C
78H50O18P2Ru6Sb2: C 42.83, H 2.30. Found: C 42.93, H 1.99. ESI-
MSþ (m/z): 2350 [M þ H]þ.
The supernatant was separated by TLC, with DCM/hexane (1:2,
v/v) as the eluent, to give two three bands.
Bands 1 and 3 were identified as unreacted 5-Ru (1 mg) and a
trace amount of 9b-Ru, respectively.
Band 2, blue, afforded 8b-Ru as the major product.
Yield ¼ 10 mg (46% based on consumed 5-Ru). IR (CH2Cl2):
2103m, 2075s, 2048w, 2029vs, 2006s, 1979w, 1969w cmꢀ1. 1H NMR
(CD2Cl2) 7.56 (br, s, 5H, PhH), 7.38 (br, s, 10H, PhH), 7.08e7.27 (m,
20H, PhH) ppm. 13C{1H} NMR (CD2Cl2):
(CO) 219.59 (2C), 218.62
n(CO)
d
5.8. Computational studies
d
(2C), 215.45 (2C), 213.89 (2C), 200.88 (1C), 200.16 (1C), 199.97 (2C,
DFT calculations were performed with the Gaussian 09 suite of
programs [27], utilizing B3LYP density-functional, together with an
“ultrafine” numerical integration grid. The LanL2DZ (Los Alamos
effective core potential double-z) basis set, together with d- or f-
type polarization functions [28], was employed for the Os and Sb
atoms while the 6-311G(2d, p) basis set was used for the remaining
atoms. Spin-restricted calculations were used for geometry opti-
mization. Harmonic frequencies were then calculated to charac-
terize the stationary points as equilibrium structures with all real
frequencies, and to evaluate zero-point energy (ZPE) corrections.
Isotropic nuclear magnetic shielding constants were calculated
using the gauge-including-atomic-orbital (GIAO) method at the HF
level of theory with the same basis sets above, in a solvated phase
2
2JP-C ¼ 8 Hz), 199.44 (1C, JP-C ¼ 5 Hz), 199.22 (1C), 198.22 (1C),
195.48 (2C), 194.20 (1C), 190.65 (1C),
d (Ph) 135.43, 134.93, 134.62,
134.16, 132.78, 132.67, 131.98, 130.75, 129.59, 129.17, 129.00, 128.76,
128.67 ppm. 31P{1H} NMR (CD2Cl2)
d
32.49 (s) ppm. Anal. Calcd for
C
61H35O19PRu6Sb2: C 37.52, H 1.81. Found: C 37.01, H 1.58. ESI-MSþ
(m/z): 2350 [M þ H]þ.
t
5.6. Reaction of 5-Ru with BuNC
To a solution of 5-Ru (20 mg, 12
added a solution of BuNC in dry hexane (0.20 ml, 12
m
mol) in dry DCM (10 ml) was
t
mmol), drop-
wise. The resulting blue-purple solution was stirred at room tem-
perature for 24 h before solvent removal and separation of the
residue on a silica column, with DCM/Hexane (1:1, v/v) as eluent, to
(THF) using the PCM model [29]; chemical shifts
d were obtained as
d
¼
sref sorb, in which sref is the shielding in TMS.
ꢀ
Please cite this article in press as: Y.-Z. Li, W.K. Leong, Journal of Organometallic Chemistry (2015), http://dx.doi.org/10.1016/
j.jorganchem.2015.06.007

Y.-Z. Li, W.K. Leong / Journal of Organometallic Chemistry xxx (2015) 1e9
9
[10] Y.-Z. Li, R. Ganguly, W.K. Leong, Organometallics 33 (2014) 3867e3876.
[11] W.K. Leong, G. Chen, J. Chem. Soc. Dalton Trans. (2000) 4442e4445.
[12] Cluster 2-Os (24 mg, 20 mol) was dissolved in dry THF (10 ml) followed by
addition of Na2CO3 (3.6 mg, 34 mol) and deionized H2O (0.5 ml), the
resulting mixture was stirred at room temperature for 78h, monitored by IR
spectra. The solvents were removed and the residue redissolved in DCM for
5 min. Then the residue was separated on silica TLC with DCM/Hexane (1:1, v/
v) as eluent to give 3-Os as the sole separable product (Yield ¼ 17.5 mg, 75%).
[13] M.A.M. Al-Ibadi, S.B. Duckett, J.E. McGrady, Dalton Trans. 41 (2012)
4618e4625.
[14] We wish to thank one of the reviewers for alerting us to this work.
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M.L. Williams, J. Chem. Soc. Chem. Commun. (1982) 442e444;
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321e343;
Acknowledgement
m
This work was supported by Nanyang Technological University
and the Ministry of Education (Research Grant No. M4011158). Y.-Z.
Li thanks the university for a Research Scholarship. We also
acknowledge Dr. Yan-Li Zhao for the use of his X-ray diffractometer
and Dr. Pei-Zhou Li for assistance with the data collection on
clusters 5-Os, 9a-Os, 9b-Ru and 8c-Ru.
m
Supplementary material
Crystallographic data (excluding structure factors) for the
structures in this paper have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication
numbers CCDC 1500549-53. Copies of the data can be obtained,
free of charge, on application to CCDC, 12 Union Road, Cambridge
CB2 1EZ, UK, (fax: þ44 1223 336033 or e-mail: deposit@ccdc.cam.
ac.uk). Spectroscopic and other data for all compounds, details of
computed structures, and ORTEP plots of 8c-Ru and 9b-Ru.
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2 (1983)
Appendix A. Supplementary data
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(1991) 1126e1127;
Supplementary data related to this article can be found at http://
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(b) S. Jeannin, Y. Jeannin, F. Robert, C. Rosenberger, Inorg. Chem. 33 (1994)
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(d) K.K.H. Lee, W.T. Wong, J. Organomet. Chem. 503 (1995) C43eC45;
(e) L.A. Hoferkamp, G. Rheinwald, H. Stoeckli-Evans, G. Süss-Fink, Organo-
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Please cite this article in press as: Y.-Z. Li, W.K. Leong, Journal of Organometallic Chemistry (2015), http://dx.doi.org/10.1016/
j.jorganchem.2015.06.007