Reactivity of electron-deficient triosmium quinoline cluster [Os 3(CO)9(μ3-η2-C 9H6N)(μ-H)] with alkynes

Article abstract of DOI:10.1016/j.ica.2011.08.023

Reactions of the electron-deficient triosmium cluster [Os ₃(CO)₉(μ₃-η²-C ₉H₆N)(μ-H)] (1) with various alkynes are described. Cluster 1 readily reacts with the activated alkyne dimethyl acetylenedicarboxylate (dmad) upon mild heating (65-70 °C) to give the adduct [Os₃(CO)₉(μ-C₉H₆N) (μ₃-MeO₂CCCHCO₂Me)] (2). In contrast, a similar reaction of 1 with diphenylacetylene affords previously reported compounds [Os₃(CO)₁₀(μ-η²-C ₉H₆N)(μ-H)] (3), [Os₃(CO) ₉(μ-C₄Ph₄)] (4) and [Os₃(CO) ₈{μ₃-C(C₆H₄)C₃Ph ₃}(μ-H)] (5) while with 2-butyne gives only the known compound [Os₃(CO)₇(μ-C₄Me₄) (μ₃-C₂Me₂)] (6). The new cluster 2 has been characterized by a combination of spectroscopic data and single crystal X-ray diffraction analysis.

Full text of DOI:10.1016/j.ica.2011.08.023

Inorganica Chimica Acta 378 (2011) 307–310
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Note
Reactivity of electron-deficient triosmium quinoline cluster
[Os3(CO)9(l3 -H)] with alkynes
2-C9H6N)(
-g
l
Shishir Ghosh a, Md. Rafique Al-Mamun a, G.M. Golzar Hossain b, Shariff E. Kabir a,
⇑
a Department of Chemistry, Jahangirnagar University, Savar, Dhaka 1342, Bangladesh
b Department of Chemistry, Dhaka University, Dhaka 1000, Bangladesh
a r t i c l e i n f o
a b s t r a c t
Reactions of the electron-deficient triosmium cluster [Os3(CO)9(l3-g l-H)] (1) with various
2-C9H6N)(
Article history:
Received 24 July 2010
Received in revised form 9 July 2011
Accepted 11 August 2011
Available online 25 August 2011
alkynes are described. Cluster 1 readily reacts with the activated alkyne dimethyl acetylenedicarboxylate
(dmad) upon mild heating (65–70 °C) to give the adduct [Os3(CO)9( -C9H6N)( 3-MeO2CCCHCO2Me)] (2).
In contrast, a similar reaction of 1 with diphenylacetylene affords previously reported compounds
[Os3(CO)10 -H)] (3), [Os3(CO)9( -C4Ph4)] (4) and [Os3(CO)8{ 3-C(C6H4)C3Ph3}( -H)] (5)
2-C9H6N)(
while with 2-butyne gives only the known compound [Os3(CO)7( -C4Me4)( 3-C2Me2)] (6). The new clus-
l
l
(
l
-g
l
l
l
l
l
l
Keywords:
Triosmium clusters
Carbonyls
Alkenyl complexes
X-ray structure
ter 2 has been characterized by a combination of spectroscopic data and single crystal X-ray diffraction
analysis.
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
complexes B and C (Scheme 1). We also showed that B cleanly
transformed to C under similar conditions thereby established B
The chemistry of electron-deficient triosmium clusters is
spurred by their excellent reactivity compared to their electron-
precise counterparts as most of them are chemically inert under
mild conditions [1–3]. Among various types of electron-deficient
triosmium clusters, the benzoheterocyclic clusters of the general
as the kinetic product and C as the thermodynamic product
(Scheme 1). As part of our study of the reactivity of these unsatu-
rated clusters with alkynes we have now studied the reactions of
another triosmium unsaturated cluster of this series namely the
quinoline cluster [Os3(CO)9(l3-g l-H)] (1) with various
2-C9H6N)(
formula [Os3(CO)9{l3
-
g
2-(L-H)}(
l-H)] (L = quinoline, benzothia-
alkynes the results of which are described herein.
zole, benzimidazole, quinoxaline, benzoxazole, phenanthridine,
5,6-benzoquinoline) are one of the well studied class of unsatu-
rated 46-electron triosmium hydride clusters. Their reactivity has
been thoroughly investigated over the past ten years from which
it has been found that they are reactive towards a wide range of
substrates [4–15]. For examples, reactions of phosphine and
amines with this type of clusters result in ligand addition at the
metal core along with rearrangements whereas reactions with an-
ionic neocleophiles such as hydride or carbanions results in attack
at the carbocyclic ring [4,5,7–12].
2. Experimental
All reactions were carried out under a dry nitrogen atmosphere
using standard Schlenk techniques but work-up was carried out in
air unless otherwise stated. Reagent grade solvents were dried
using appropriate drying agents and distilled prior to use by stan-
dard methods. Dimethyl acetylenedicarboxylate, diphenylacety-
lene and 2-butyne were purchased from Aldrich and used as
received. Cluster [Os3(CO)9(l3-g l-H)] (1) was prepared
2-C9H6N)(
The reactivity of this type of clusters so far studied was mainly
with neutral two electron donors or carbanions. Surprisingly we
found that no reactions of these clusters with alkynes have been
reported to date albeit alkynes are an important class of organic
ligands with carbon donor atoms. So, we have decided to investi-
gate their reactivity with various alkynes and recently reported that
according to the literature method [4,9]. Infrared spectra were re-
corded on a Shimadzu FTIR 8101 spectrophotometer. NMR spectra
were recorded on Varian Unity Plus 400 instruments. Elemental
analyses were performed by BCSIR Laboratories, Dhaka.
2.1. Reaction of 1 with dimethyl acetylenedicarboxylate
the benzothiazole cluster [Os3(CO)9(l3-g l-H)] (A) [13],
2-C7H4NS)(
reacts with dmad resulting in the formation of two isomeric alkenyl
To a hexane solution (50 mL) of 1 (150 mg, 0.158 mmol) was
added dimethyl acetylenedicarboxylate (110 mg, 0.774 mmol)
and the mixture was heated at 65–70 °C for 15 h during which
time the colour of the reaction mixture changed from green to
⇑
Corresponding author.
E-mail address: skabir_ju@yahoo.com (S.E. Kabir).
0020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2011.08.023

308
S. Ghosh et al. / Inorganica Chimica Acta 378 (2011) 307–310
S
N
S
N
S
N
65-70 oC
(CO)3
Os
RC CR
65-70 oC
(CO)3
(OC)
3Os
Os
(OC)
3Os
(OC)3
Os
Os (CO)3
H
H
C
C
Os(CO)3
Os
H
Os(CO)3
C
(CO)3
C
R = CO2Me
C
C
O
O
MeO
MeO
R
R
A
B
C
Scheme 1. Reactivity of the benzothiazole cluster [Os3(CO)9(l3-g l-H)] (A) towards dmad.
2-C7H4NS)(
Table 1
yellow. The solvent was removed under reduced pressure and the
residue chromatographed by TLC on silica gel. Elution with hexane/
CH2Cl2 (7:3, v/v) developed two bands. The major band afforded
Crystallographic data and structure refinement for 2.
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
C24H13NO13Os3
1093.95
150(2)
[Os3(CO)9(l-C9H6N)(l3-MeO2CCCHCO2Me)] (2) (64 mg, 37%) as
yellow crystals after recrystallization from hexane/CH2Cl2 at
20 °C while the minor band gave unreacted 1 (trace). Spectral data
for 2: Anal. Calc. for C24H13NO13Os3: C, 26.35; H, 1.20; N, 1.28.
0.71073
triclinic
ꢀ
P1
Found: C, 26.62; H, 1.37; N, 1.38%. IR (
2064 s, 2029 m, 2018 sh, 1993 s,br, 1967 w, 1942 w, 1923 w,
1918 cmÀ1 1H NMR (CDCl3): d 9.21 (m, 1H), 8.20 (m, 1H), 8.13
m(CO), CH2Cl2): 2087 w,
9.639(2)
9.927(2)
16.204(4)
79.81(2)
b (Å)
c (Å)
.
(m, 1H), 7.09 (m, 3H), 3.73 (s, 3H), 3.58 (s, 3H), 2.48 (s, 1H).
a
(°)
b (°)
81.84(3)
c
(°)
62.96(2)
1355.9(5)
2.2. Reaction of 1 with diphenylacetylene
Volume (Å3)
Z
2
A heptane solution (50 mL) of 1 (190 mg, 0.199 mmol) and
diphenylacetylene (175 mg, 0.972 mmol) was heated to reflux for
6 h. A similar chromatographic separation to that above gave the
Density (calculated) (Mg/m3)
Absorption coefficient (mmÀ1
F(0 0 0)
2.680
14.091
992
)
Crystal size (mm3)
h range for data collection (°)
Index ranges
0.15 Â 0.15 Â 0.15
following compounds in order of elution: [Os3(CO)10
H)] (3) (24 mg, 12%), [Os3(CO)8{ 3-C(C6H4)C3Ph3}(
(33 mg, 14%), [Os3(CO)9( -C4Ph4)] (4) (30 mg, 13%) and 1 (10 mg).
(l
-C9H6N)(l-
2.32–24.88
l
l
-H)] (5)
À10 ꢀ h ꢁ 5
À11 ꢀ k ꢁ 11
À17 ꢀ l ꢁ 18
4701
3586 (Rint = 0.0621)
full-matrix least-squares on F2
0.2264 and 0.2264
3586/228/372
1.010
l
Reflections collected
Independent reflections
Refinement method
2.3. Reaction of 1 with 2-butyne
A reaction similar to that above of 1 (100 mg, 0.105 mmol)
and 2-butyne (40 mg, 0.741 mmol) in refluxing hexane for 15 h
followed by similar chromatographic separation afforded [Os3-
Maximum and minimum transmission
Data/restraints/parameters
Goodness-of-fit (GOF) on F2
Final R indices [I > 2
r
(I)]
R1 = 0.0409, wR2 = 0.1152
R1 = 0.0475, wR2 = 0.1166
2.343 and À2.232
(CO)7(l-C4Me4)(l3-C2Me2)] (6) (36 mg, 37%).
R indices (all data)
Largest difference peak and hole (e ÅÀ3
)
2.4. X-ray crystallography
Single crystals of 2 suitable for X-ray diffraction were grown by
slow diffusion of hexane into a dichloromethane solution at 20 °C.
Crystallographic data were collected at 150(2) K, using Enraf–Non-
of the quinoline ligand and six methyl protons of the carboxylate
groups of dmad. In addition the absence of any hydride resonance
and appearance of a singlet at d 2.48 (integrated to 1H) indicates
that the hydride is transferred to the alkyne moiety which was also
observed for B and C (vide supra). The pattern of the IR spectrum of
2 is very similar to those of B and C that differ by the orientation of
the benzothiazole ring. In view of the similarity of spectroscopic
data of 2 with those of B and C it was not possible to identify which
isomeric form of 2 was isolated. In order to elucidate the precise
nature of 2 an X-ray crystallographic study was carried out the re-
sults of which are summarized in Fig. 1.
ius CAD4 diffractometer with graphite monochromated Mo K
a
radiation (k = 0.71073 Å). All calculations were carried out using
the WinGX package [16] and all data sets were corrected for
absorption using DIFABS [17]. The structure was solved by direct
methods and refined on F2 by full matrix least-squares using SHELXL
[18] using all unique data. All non-hydrogen atoms were directly
located from difference Fourier maps and refined using anisotropic
displacement parameters without any geometrical restraints. The
hydrogen atoms were included in calculated positions (riding
model). All pertinent crystal data and other experimental condi-
tions and refinement details are summarized in Table 1.
The molecule consists of an open trinuclear cluster of three os-
mium atoms with two distinctly different osmium–osmium bonds
[Os(1)–Os(2) 2.8138(12) and Os(2)–Os(3) 2.9263(11) Å]. The nine
carbonyl atoms are all terminal and equally distributed to three os-
mium atoms. The quinoline ligand bridges the Os(1)–Os(2) edge so
that the nitrogen atom is bonded to the central osmium atom,
Os(2), of the open cluster [Os(2)–N(1) 2.249(13) and Os(1)–C(21)
2.133(15) Å] which is also observed in the thermodynamic product
C obtained from the reaction between A and dmad (vide supra). The
3. Results and discussion
Treatment of 1 with excess dmad (RC„CR, R = CO2Me) at 65–
70 °C in hexane furnished [Os3(CO)9(l-C9H6N)(l3-MeO2CCCH-
CO2Me)] (2) in 37% yield (Scheme 2). Apparently, the alkyne ligand
is inserted into the metal hydride bond to form alkenyl cluster. The
1H NMR spectrum of 2 displays resonances for six aromatic protons
alkenyl ligand is coordinated to the triosmium core in a l3
j1 fashion, i.e., one carbon, C(13), bridges an osmium–osmium
– , ,
g2 g1

S. Ghosh et al. / Inorganica Chimica Acta 378 (2011) 307–310
309
N
C
N
RC CR
65-70 oC
(CO)3
Os
(OC)
3Os
(OC)3Os
Os (CO)3
H
C
Os
H
Os(CO)3
(CO)3
C
R = CO2Me
O
MeO
R
1
2
Scheme 2. Reaction of the quinoline cluster [Os3(CO)9(l3-g l-H)] (1) with dmad.
2-C9H6N)(
edge, Os(1)–Os(2), which is also bridged by the benzoheterocyclic
ligand while the other carbon of the alkenyl moiety, C(10), is
bonded to the third osmium, Os(3), which is also bound to a car-
bonyl oxygen of one of the carboxylate group and a hydrogen
atom. The doubly bridged osmium–osmium edge is shorter than
the other. The carboxylate groups of the hydrocarbyl ligand are
in cis-orientation with respect to each other and located on the
opposite face of the Os3 triangle relative to the benzoheterocyclic
ligand. The C(10)–C(13) distance of 1.53(2) Å is similar to the car-
bon–carbon single bond distances formed by using sp3 hybrid orbi-
tals which clearly indicates the presence of a single bond between
them. The formation of only one product (2) in this reaction which
resembles the thermodynamic product (C) obtained from the reac-
tion between A and dmad suggesting that the kinetic product of
this reaction (product analogous to B) is thermally unstable under
the reaction conditions which readily convert to 2 after its forma-
tion. This also implies that the benzothiazole binds more strongly
to the cluster compare to quinoline as bond rearrangement is nec-
essary for this isomeric conversion. This phenomenon was also ob-
served by Rosenberg and coworkers during their study relating to
the displacement of these heterocycles by acetonitrile from cluster
surface after functionalization [5]. Later they also showed that the
nitrogen atom of the five-membered heterocyclic ring is more ba-
sic than that of six-membered heterocyclic ring thereby the former
forms stronger bond with metals [10]. Apart from C, Lin and Leong
Fig. 1. The solid-state molecular structure of 2. The thermal ellipsoids were drawn
at 50% probability level. Hydrogen atoms are omitted for clarity. Selected
interatomic distances (Å) and angles (°): Os(1)–Os(2) 2.8137(12), Os(2)–Os(3)
2.9263(11), Os(3)–O(12) 2.164(10), Os(2)–N(1) 2.248(12), Os(1)–C(21) 2.132(15),
Os(1)–C(13) 2.106(16), Os(2)–C(13) 2.227(16), Os(3)–C(10) 2.175(16), C(10)–C(13)
1.531(19), Os(1)–Os(2)–Os(3) 107.09(4), C(14)–O(12)–Os(3) 103.8(9), C(13)–C(10)–
Os(3) 89.2(9), Os(1)–C(13)–Os(2) 80.9(5), C(10)–C(13)–Os(1) 128.0(11), C(10)–
C(13)–Os(2) 108.0(10).
also reported
C5H3O2)( 3-MeO2CCCHCO2Me)] akin to 2 which was obtained
from the reaction between the -pyrone cluster [Os3(CO)10
C5H3O2)( -H)] and dmad [19].
a
triosmium cluster namely [Os3(CO)9(l-c-
l
c
(l-c-
l
To gain more insight into the reaction of 1 and alkynes we have
investigated its reaction with diphenylacetylene and 2-butyne.
Ph
Ph
Ph
C
C
C
C
N
(OC)3
Os
(OC)3
Os
C
C
Ph
Ph
H
Os
Os
(CO)3
(OC)3
(i)
4Os
Os
(OC)3
(OC)
+
+
C
C
Os
Os
Os
Ph
Ph
(CO)4
(CO)2
(CO)2
98 oC
3
4
5
1
(ii)
80 oC
Me
C
Me
Me
C
(i)
(ii)
=
PhC CPh
MeC CMe
Me
C
C
=
C
Me
Me
C
Os
Os
Os
(OC)2
6
(OC)3
(CO)3
Scheme 3. Reactions of the quinoline cluster [Os3(CO)9(l3-g l-H)] (1) with diphenylacetylene and 2-butyne.
2-C9H6N)(

310
S. Ghosh et al. / Inorganica Chimica Acta 378 (2011) 307–310
Heating a heptane solution of 1 and diphenylacetylene at 98 °C re-
sulted in the isolation of three known compounds [Os3(CO)10
C9H6N)( -H)] (3) (12%), [Os3(CO)9( -C4Ph4)] (4) (13%) and [Os3(-
CO)8{ 3-C(C6H4)C3Ph3}( -H)] (5) (14%) (Scheme 3). Cluster 3 [9] is
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.
2011.08.023.
(l-
l
l
l
l
the parent decacarbonyl clusterof 1 while compound 4 was reported
by Ferraris et al. from the reaction between Os3(CO)12 and PhC2Ph
and 5 from the thermal decarbonylation of 4 followed by subsequent
C–H activation of one of the phenyl groups of the coordinated C4Ph4
ligand [20,21]. A similar reaction of 1 with 2-butyne gave only [Os3(-
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cluster 1 which carries a l3–g
2-quinoline ligand with dmad led
to retention of the quinoline ligand and metal–metal bond scission,
resulting in the formation of the monosubstituted dmad product.
In contrast, with diphenylacetylene the previously reported alkyne
only derivatives 4 and 5 were obtained. Furthermore, the reaction
between 1 and 2-butyne followed a different course to those
describe above affording 6 incorporating both mono and dimerized
alkyne.
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Acknowledgements
Financial support of this work by the University Grants Com-
mission of Bangladesh is gratefully acknowledged.
Appendix A. Supplementary material
CCDC 785241 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The