A comparative study of the reactivity of unsaturated triosmium clusters [Os3(CO)8{μ3-Ph2PCH2P(Ph)C6H4}(μ-H)] and [Os3(CO)9{μ3-η2-C7H3(2-Me)NS}(μ-H)] with tBuNC

Article abstract of DOI:10.1016/j.jorganchem.2008.08.032

Treatment of unsaturated [Os₃(CO)₈{μ₃-Ph₂PCH₂P(Ph)C₆H₄}(μ-H)] (2) with ^tBuNC at room temperature gives [Os₃(CO)₈(CNBu^t)){μ₃-Ph₂PCH₂P(Ph)C₆H₄}(μ-H)] (3) which on thermolysis in refluxing toluene furnishes [Os₃(CO)₇(CNBu^t){μ₃-Ph₂PCHP(Ph)C₆H₄}(μ-H)₂] (4). Reaction of the labile complex [Os₃(CO)₉(μ-dppm)(NCMe)] (5) with ^tBuNC at room temperature affords the substitution product [Os₃(CO)₉(μ-dppm)(CNBu^t)] (6). Thermolysis of 6 in refluxing toluene gives 4. On the other hand, the reaction of unsaturated [Os₃(CO)₉{μ₃-η²-C₇H₃(2-Me)NS}(μ-H)] (7) with ^tBuNC yields the addition product [Os₃(CO)₉(CNBu^t){μ-η²-C₇H₃(2-Me)NS}(μ-H)] (8) which on decarbonylation in refluxing toluene gives unsaturated [Os₃(CO)₈(CNBu^t){μ₃-η²-C₇H₃(2-Me)NS}(μ-H)] (9). Compound 9 reacts with PPh₃ at room temperature to give the adduct [Os₃(CO)₈(PPh₃)(CNBu^t){μ-η²-C₇H₃(2-Me)NS(μ-H)] (10). Compound 8 exists as two isomers in solution whereas 10 occurs in four isomeric forms. The molecular structures of 3, 6, 8, and 10 have been determined by X-ray diffraction studies.

Full text of DOI:10.1016/j.jorganchem.2008.08.032

Journal of Organometallic Chemistry 693 (2008) 3613–3621
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
A comparative study of the reactivity of unsaturated triosmium clusters
[Os3(CO)8{l3-Ph2PCH2P(Ph)C6H4}(l-H)] and [Os3(CO)9{l3-g
2-C7H3(2-Me)NS}-
t
(l-H)] with BuNC
Arun K. Raha a, Shishir Ghosh a, Md. Manzurul Karim a, Derek A. Tocher b, Noorjahan Begum c,
Ayesha Sharmin d, Edward Rosenberg d, Shariff E. Kabir a,
*
a Department of Chemistry, Jahangirnagar University, Savar, Dhaka 1342, Bangladesh
b Department of Chemistry, University College London, 20 Gordon Street, London WC1H OAJ, UK
c Department of Agricultural Chemistry, Sher-e-Bangla Agricultural University, Sher-e-Bangla Nagar, Dhaka 1207, Bangladesh
d Department of Chemistry, The University of Montana, Missoula, MT 59812, USA
a r t i c l e i n f o
a b s t r a c t
t
Article history:
Received 6 August 2008
Received in revised form 24 August 2008
Accepted 25 August 2008
Available online 31 August 2008
Treatment of unsaturated [Os3(CO)8{
l
3-Ph2PCH2P(Ph)C6H4}(
l-H)] (2) with BuNC at room temperature
gives [Os3(CO)8(CNBut)){
l3-Ph2PCH2P(Ph)C6H4}(l-H)] (3) which on thermolysis in refluxing toluene
furnishes [Os3(CO)7(CNBut){
l3-Ph2PCHP(Ph)C6H4}(l-H)2] (4). Reaction of the labile complex
[Os3(CO)9(
[Os3(CO)9(
l
l
-dppm)(NCMe)] (5) with tBuNC at room temperature affords the substitution product
-dppm)(CNBut)] (6). Thermolysis of 6 in refluxing toluene gives 4. On the other hand, the
t
reaction of unsaturated [Os3(CO)9{l3
uct [Os3(CO)9(CNBut){ 2-C7H3(2-Me)NS}(
gives unsaturated [Os3(CO)8(CNBut){l3 2-C7H3(2-Me)NS}(
room temperature to give the adduct [Os3(CO)8(PPh3)(CNBut){
-
g
2-C7H3(2-Me)NS}(
l
-H)] (7) with BuNC yields the addition prod-
Keywords:
Unsaturated clusters
Diphosphine
2-Methylbenzothiazole
tert-Butyl isocyanide
X-ray structures
l
-
g
l
-H)] (8) which on decarbonylation in refluxing toluene
-H)] (9). Compound 9 reacts with PPh3 at
2-C7H3(2-Me)NS(
-H)] (10). Com-
-
g
l
l
-
g
l
pound 8 exists as two isomers in solution whereas 10 occurs in four isomeric forms. The molecular struc-
tures of 3, 6, 8, and 10 have been determined by X-ray diffraction studies.
Ó 2008 Elsevier B.V. All rights reserved.
1. Introduction
1 [7], with H2 to form [Os3(CO)8(
acetylene to form [Os3(CO)8(PhC„CPh)(
phines (PR3) to give [Os3(CO)8(PR3){ 3-Ph2PCH2P(Ph)C6H4}(
and [Os3(CO)8(PR3)2( -dppm)] [10,11], with R3SiH to form [Os3
-H)] and [Os3(CO)7(SiR3){ 3-Ph2PCH2-
-H)2] [12], and with [Au(PPh3)]PF6 and HBF4 to form
3-Ph2PCH2P(Ph)C6H4}( -AuPPh3)
3-Ph2PCH2P(Ph)C6H4}( -H)2]BF4, respec-
l
-H)2(
l
-dppm)] [8], with diphenyl-
-dppm)] [9], with phos-
-H)]
l
It is well known that coordinatively unsaturated transition me-
tal cluster complexes, are much more reactive relative to their
electron precise counterparts [1–3]. Electron-deficiency in these
clusters makes them more vulnerable to attack by nucleophiles.
Furthermore, the cluster-bound ligands within these unsaturated
compounds frequently interact with other substrates to give new
products that are not obtainable by conventional organic synthesis
[4–6]. As a consequence, these electron-deficient triosmium clus-
ters have attracted considerable interest for many years and their
chemistry has been thoroughly investigated during the last decade
to reveal their catalytic potential as well as applications in organic
synthesis [4–27].
l
l
l
(CO)9(SiR3)(
P(Ph)C6H4}(
l
l
-dppm)(
l
l
the cationic clusters [Os3(CO)8{
-H)]PF6 and [Os3(CO)9{
tively [13].
l
l
(l
l
l
On the other hand, the reactions of the electron-deficient
benzoheterocyclic triosmium clusters of the type [Os3(CO)9
(
l
-H)(l3
benzothiazole, benzoxazole) obtained from decarbonylation of
the corresponding decacabonyls [Os3(CO)10 -H)(
2-L-H)], with
-g
2-L-H)] (L = quinoline, quinoxaline, benzimidazole,
(l
l-g
One of the most interesting unsaturated triosmium clusters
neutral nucleophiles such as phosphine and amines results in
ligand addition at the metal core along with rearrangements
whereas reactions with anionic nucleophiles such as hydride or
carbanions results in attack at the carbocyclic ring [4–6,17–20,23]
(Scheme 2).
[Os3(CO)8{l3-Ph2PCH2P(Ph)C6H4}(l-H)] (2), derived from the
decarbonylation of the decacarbonyl compound [Os3(CO)10
(l-
dppm)] (1), shows unique chemical properties and its reactivity
with various ligands has been studied extensively (Scheme 1).
For example, it reacts with CO to form first [Os3(CO)9{l3
-
The reactivity of the dihydrido unsaturated cluster [Os3(CO)10
-H)2] with isocyanides have been reported to give the simple
adduct [Os3(CO)10(L)(
-H)2] (L = MeNC, tBuNC). Interestingly, tBuNC
-
Ph2PCH2P(Ph)C6H4}( -H)] and finally the decacarbonyl compound
l
(l
l
adduct exists as two isomers in solution of which the trans isomer
was crystallographically characterized [22]. In the light of these
* Corresponding author. Tel.: +880 406 243 2592; fax: +880 406 243 2477.
E-mail address: skabir_ju@yahoo.com (S.E. Kabir).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.08.032

3614
A.K. Raha et al. / Journal of Organometallic Chemistry 693 (2008) 3613–3621
(CO)3
Os
Ph2
P
Os
(OC)4
Os
P
(CO)3 Ph2
110 oC
CO, 2d
- 2CO
Ph
P
Ph
P
CO, 2h
110 oC
Os
(OC)3
Os
Os
(OC)3
Os
(CO)3
(CO)3
H
Os
P
H
Os
P
(CO)2 Ph2
(CO)3 Ph2
PR3
80 oC H2
CO
Os
R3P
R3P
(CO)3
Os
Ph2
P
CO
+
Os
P
(CO)3 Ph2
H
(CO)2
Os
Ph2
Ph
P
Os
(OC)4
P
Os
P
Ph2
(CO)2
Os
(OC)3
Os
(CO)3
H
H
R3P
Os
P
(CO)2 Ph2
Scheme 1.
N
N
H
- CO
+ CO
(OC)3Os
Os(CO)3
(OC)3Os
Os(CO)3
H
Os
Os
(CO)4
(CO)3
PR3
-C(CH3)2CN (2 eqv)
N
OC
Os
Os(CO)3
R3P
H+
H
Os
OC
(CO)3
NC
NC
H
H
H
N
N
(OC)3Os
Os(CO)3
(OC)3Os
Os(CO)3
+
H
Os
(CO)3
H
Os
(CO)3
Scheme 2.
results and as an extension of our previous studies on the reactiv-
ities of these electron-deficient triosmium clusters with various or-
ganic and inorganic ligands, we have now examined the reactivity
2. Experimental
All reactions were performed under a nitrogen atmosphere. Re-
agent grade solvents were dried by the standard procedures and
t
of these clusters with BuNC and studied the effect of isocyanide–
carbonyl replacement on the reactivity of the resultant complexes.
These studies reveal that isocyanide coordination impacts the ther-
mal reactivity of these two types of unsaturated triosmium clusters
differently.
were freshly distilled prior to use. The clusters [Os3(CO)8{l3
Ph2PCH2P(Ph)C6H4}( -H)] (2) [7], [Os3(CO)9( -dppm)(NCMe)] (5)
[27] and [Os3(CO)9{l3 -H)] (7) [20] were pre-
2-C7H3(2-Me)NS}(
pared according to the published procedures. Tert-butylisocyanide
-
l
l
-
g
l

A.K. Raha et al. / Journal of Organometallic Chemistry 693 (2008) 3613–3621
3615
was purchased from Strem Chemicals and used as received. Infra-
red spectra were recorded on a Shimadzu FTIR 8101 spectropho-
tometer. 1H and 31P-{1H} NMR spectra were recorded on a Bruker
DPX 400 instrument. All chemical shifts are reported in d units
with reference to the residual protons of the deuterated solvents
for proton and to external 85% H3PO4 for 31P chemical shifts. Ele-
mental analyses were performed by Microanalytical Laboratories,
University College London. Fast atom bombardment mass spectra
were obtained on a JEOL SX-102 spectrometer using 3-nitrobenzyl
alcohol as matrix and CsI as calibrant.
(CDCl3): d 7.66–7.19 (m, 20H), 5.05 (m, 2H), 1.48 (s, 9H); 31P-
{1H} NMR (CDCl3): d À27.3 (s); MS (FAB): m/z 1291 (M+).
2.4. Thermolysis of [Os3(CO)9(l
-dppm)(CNBut)] (6)
A toluene solution (10 mL) of 6 (25 mg, 0.019 mmol) was re-
fluxed for 3 h. The solvent was removed under reduced pressure
and the residue separated by TLC on silica gel. Elution with hex-
ane/CH2Cl2 (7:3, v/v) gave two bands. The major band was identi-
fied as 4 (12 mg, 50%) and the minor band as unconsumed 6 (5 mg).
2.5. Reaction of [Os3(CO)9{l3-g l-H)] (7)
2-C7H3(2-Me)NS}(
with ter-butylisocyanide
2.1. Reaction of [Os3(CO)8{
tert-butylisocyanide
l3-Ph2PCH2P(Ph)C6H4}(l-H)] (2) with
A dichloromethane solution (20 mL) of 7 (50 mg, 0.051 mmol)
and BuNC (14 mg, 0.17 mmol) was stirred at room temperature
To a dichloromethane solution of 2 (100 mg, 0.085 mmol) was
added a solution (10 mL) of tBuNC (14 mg, 0.17 mmol) in the same
solvent over a period of 30 min. The reaction mixture was stirred at
room temperature for a further 1.5 h during which time the color
changed from green to yellow. The solvent was removed under re-
duced pressure and the residue separated by TLC on silica gel. Elu-
tion with hexane/CH2Cl2 (7:3, v/v) developed one major and two
very minor bands. The major band afforded [Os3(CO)8(CN-
t
for 30 min during which time the color changed from green to yel-
low. The solvent was removed under reduced pressure and the res-
idue separated by TLC on silica gel. Elution with hexane/CH2Cl2 (7:3,
v/v) developed one band which afforded [Os3(CO)9(CNBut){ g2
l- -
C7H3(2-Me)NS}(l-H)] (8) (45 mg, 85%) as yellow crystals from hex-
ane/CH2Cl2 at À4 oC. Anal. Calc. for C22H16N2O9Os3S: C, 25.04; H,
1.53; N, 2.65. Found: C, 25.24; H, 1.72; N, 2.82%. IR (mCO, CH2Cl2):
But)){
l3-Ph2PCH2P(Ph)C6H4}(l-H)] (3) (42 mg, 39%) as yellow crys-
2075 w, 2043 vs, 2029 vs, 1979 vs, cmÀ1, (
s cmÀ1 1H NMR (CDCl3) major isomer (95%): d 7.97 (dd, 1H,
mCN, CH2Cl2): 2181
tals after recrystallization from hexane/CH2Cl2 at 4 oC. Anal. Calc.
for C38H31NO8Os3P2: C, 36.16; H, 2.48; N, 1.11. Found: C, 36.45;
;
J = 7.0, 0.6 Hz), 7.16 (dd, 1H, J = 7.0, 0.6 Hz), 6.97 (t, 1H, J = 7.0 Hz),
3.0 (s, 3H), 1.42 (s, 9H), À11.88 (s, 1H); MS (FAB): m/z 1056.
H, 2.69; N, 1.18%. IR (
m
CO, CH2Cl2): 2052 vs, 2015 vs, 1995 s,
1975 s, 1951 m, 1921 w cmÀ1, (
m
CN, CH2Cl2): 2178 s cmÀ1 1H
;
NMR (CDCl3): d 7.99 (d, 1H, J = 5.1 Hz), 7.28–7.03 (m, 15H), 6.46
(d, 1H, J = 4.8 Hz,), 6.13 (t, 1H, J = 4.8 Hz), 6.07 (t, 1H, J = 5.1 Hz),
5.36 (m, 1H), 3.48 (m, 1H), 1.41 (s, 9H), À16.62 (d, 1H,
J = 7.6 Hz); 31P-{1H} NMR (CDCl3): d 12.7 (d, 1P, J = 75.6 Hz,), 16.5
(d, 1P, J = 75.6 Hz); MS (FAB): m/z 1263 (M+).
2.6. Thermolysis of [Os3(CO)9(CNBut){ 2-C7H3(2-Me)NS}(
l-g l-H)] (8)
A toluene solution (10 mL) of 8 (25 mg, 0.024 mmol) was
heated to reflux for 3 h during which time the color changed to
green. Work up followed by chromatographic separation as above
afforded unreacted 8 (4 mg) and [Os3(CO)8(CNBut){l3 g2-C7H3(2-
-
2.2. Thermolysis of [Os3(CO)8(CNBut))
Me)NS}(l-H)] (9) (15 mg, %) as green crystals from hexane/CH2Cl2
by slow evaporation of the solvents as room temperature. Anal.
{
l3-Ph2PCH2P(Ph)C6H4}(
l-H)] (3)
Calc. for C21H16N2O8Os3S: C, 25.04; H, 1.53; N, 2.65. Found: C,
A toluene solution (20 mL) of 3 (30 mg, 0.023 mmol) was heated
25.24; H, 1.72; N, 2.82%. IR (
m
CO, CH2Cl2): 2059 vs, 2015 vs, 1993
1H NMR (CDCl3): d
vs, 1978 s, cmÀ1, ( CN, CH2Cl2): 2164 s cmÀ1
m
;
to reflux for 2 h. The solvent was removed under reduced pressure
and the residue separated by TLC on silica gel. Elution with hexane/
CH2Cl2 developed one major and several very minor bands. The major
8.43(m, 1H), 8.35 (m, 1H), 6.94 (m, 1H), 2.96 (s, 3H), 1.41 (s, 9H),
À12.93 (s, 1H); MS (FAB): m/z 1028.
band afforded [Os3(CO)7(CNBut){
l
3-Ph2PCHP(Ph)C6H4}
(l-H)2]
(4) (13 mg, 45%) as yellow crystals from hexane/CH2Cl2 at À20 oC.
2.7. Reaction of [Os3(CO)8(CNBut){l3 2-C7H3(2-Me)NS}(
-g l-H)] (9)
with PPh3
Anal. Calc. for C37H31NO7Os3P2: C, 36.00; H, 2.53; N, 1.13. Found: C,
36.32; H, 2.75; N, 1.22%. IR (
m
CO, CH2Cl2): 2057 s, 2008 vs, 1987 m,
1977 sh, 1950 m, 1938 m cmÀ1, (
m
CN, CH2Cl2): 2183 s cmÀ1 1H
;
A dichloromethane solution (10 mL) of 9 (10 mg, 0.010 mmol)
and triphenylphosphine (4 mg, 0.015 mmol) was stirred at room
temperature for 30 min. The color changed from green to yellow.
The solvent was removed under reduced pressure and the residue
separated by TLC on silica gel. Elution with hexane developed one
major and two very minor bands. The major band afforded [Os3-
NMR (CDCl3): d 7.66 (d, 1H, J = 7.8 Hz), 7.51–6.96 (m, 15H), 6.84(t,
1H, J = 7.8 Hz), 6.72 (d, 1H, J = 7.8 Hz), 6.06 (t, 1H, J = 7.8 Hz), 5.10
(dd, 1H, J = 11.7, 4.0 Hz), 1.41 (s, 9H), À13.86 (d, 1H, J = 12.4 Hz),
À16.85 (d, 1H, J = 11.2, 4.8 Hz); 31P-{1H} NMR (CDCl3): d À13.7 (d,
1P, J = 53.5 Hz), À61.8 (d, 1P, J = 53.5 Hz); MS (FAB): m/z 1235 (M+).
(CO)8(PPh3)(CNBut){ 2-C7H3(2-Me)NS(
l-g l-H)] (10) (7 mg, 56%)
2.3. Reaction of [Os3(CO)9(
with tert-butylisocyanide
l-dppm)(NCMe)] (5)
as yellow crystals after recrystallization from hexane/CH2Cl2 at
4 oC. Anal. Calc. for C39H31N2O8Os3PS: C, 36.32; H, 2.43; N, 2.17.
Found: C, 36.65; H, 2.75; N, 2.32% IR (
s, 1987 s, 1960 m, 1936 w, 1915 w cmÀ1, (
s cmÀ1 1H NMR (CDCl3) for major isomer (89%): d 7.35 (m, 1H),
7.27–7.08 (m, 15H), 6.86 (d, 1H, J = 7.4 Hz), 6.39 (t, 1H,
J = 7.4 Hz), 2.93 (s, 3H), 1.42 (s, 9H), À11.15 (d, 1H, J = 16.4 Hz);
31P-{1H} NMR (CDCl3): d 12.1 (s); MS (FAB): m/z 1289.
m
CO, CH2Cl2): 2051 w, 2022
A mixture [Os3(CO)9(l-dppm)(NCMe)] (5) (80 mg, 0.064 mmol)
mCN, CH2Cl2): 2178
and tBuNC (7 mg, 0.072 mmol) in dichloromethane (10 mL) was
stirred at room temperature for 16 h. The solvent was removed
in vacuo and the residue separated by TLC on silica gel. Elution with
hexane/CH2Cl2 (4:1, v/v) gave three bands. The first band afforded
;
[Os3(CO)10
[Os3(CO)9(
(
l
l
-dppm)] (1) (7 mg, 9%) while the second band yielded
-dppm)(CNBut)] (6) (42 mg, 51%) as orange crystals
2.8. Reaction of 9 with CO
after recrystallization from hexane/CH2Cl2 at À20 oC. Anal. Calc.
for C36H23NO9Os3P2: C, 36.30; H, 2.42; N, 1.09. Found: C, 36.66;
Carbon monoxide gas was bubbled through a CDCl3 solution of
9 (15 mg, 0.015 mmol) in an NMR tube for 2 min. The 1H NMR
spectrum indicated complete conversion to cluster 8.
H, 2.65; N, 1.15%. IR (
m
CO, CH2Cl2): 2053 s, 2012 s, 1998 vs, 1980
vs, 1950 m, 1930 m cmÀ1, (
m
CN, CH2Cl2): 2177 m cmÀ1 1H NMR
;

3616
A.K. Raha et al. / Journal of Organometallic Chemistry 693 (2008) 3613–3621
2.9. X-ray structure determinations
compound 4 represents a rare example in which activation of both
aromatic and aliphatic C–H bonds has occurred. There is no evi-
dence for the formation of [Os3(CO)8(CNBut)2(
-dppm)] although
Single crystals of 3, 6, 8 and 10 suitable for X-ray diffraction
were grown by slow diffusion of hexane into a dichloromethane
solution at 4 °C. All geometric and crystallographic data for 3, 6,
8 and 10 were collected at 150 K on a Bruker SMART APEX CCD dif-
l
such a disubstituted product was expected by further addition of
t
second molecule of BuNC ligand to 3 followed by reductive elim-
ination of the orthometallated phenyl ring of the dppm ligand.
Both compounds have been characterized by IR, 1H and 31P-{1H}
NMR, mass spectroscopy and elemental analysis together with sin-
gle crystal X-ray diffraction studies for 3.
An ORTEP diagram of the molecular structure of 3 is depicted in
Fig. 1, and selected bond distances and angles are listed in the cap-
tion. Compound 3 consists of an approximate isosceles triangle of
osmium atoms with one long {Os(1)–Os(3) = 3.0546(3) Å} and
two shorter bonds {Os(1)–Os(2) = 2.8961(3) and Os(2)–
Os(3) = 2.8714(3) Å}. The eight carbonyl ligands are all terminal,
three of which are bonded to each of Os(2) and Os(3) while the
other two bonded to Os(1). The tBuNC ligand is axially coordinated
to Os(1) and lies on the opposite side of the Os3 plane with respect
fractometer using Mo Ka radiation (k = 0.71073 Å). Data reduction
and integration was carried out with SAINT+ and absorption cor-
rections were applied using the program SADABS [28]. Structures
were solved by direct methods and developed using alternating cy-
cles of least-squares refinement and difference-Fourier synthesis.
All non-hydrogen atoms were refined anisotropically. Hydrogen
atoms were placed in the calculated positions and their thermal
parameters linked to those of the atoms to which they were at-
tached (riding model). The SHELXTL PLUS V6.10 program package
was used for structure solution and refinement [29]. Final differ-
ence maps did not show any residual electron density of stereo-
chemical significance. The details of the data collection and
structure refinement are given in Table 1.
to the
l3-Ph2PCH2P(Ph)C6H4 ligand. The addition of this ligand to
the unsaturated cluster 2 changes the coordination mode of the
orthometallated phenyl ring. The bridging orthometallated phenyl
group in 2 now adopts a terminal axial coordination site on Os(3)
3. Results and discussion
3.1. Reaction of electron-deficient [Os3(CO)8{l3
Ph2PCH2P(Ph)C6H4}(l-H)] (2) with BuNC
-
in 3. As expected, the phosphorus atoms of the l3
-
t
Ph2PCH2P(Ph)C6H4 ligand also occupy axial coordination sites to
facilitate the coordination of one of the phenyl groups of this ligand
to Os(3). The hydride ligand was not located in the X-ray analysis
but is believed to bridge across the Os(1)–Os(3) edge which is con-
sistent with the lengthening of this bond and also with the opening
out of the CO ligands along this edge {C(2)–Os(1)–
Os(3) = 117.65(13) and C(9)–Os(3)–Os(1) = 111.60(14)°}. The
Os(3)–C(32) and Os(1)–C(1) bond distances in 3 {2.170(4) and
t
Reaction of the unsaturated cluster 2 with BuNC at room tem-
perature, followed by the usual workup and chromatographic sep-
aration, furnishes [Os3(CO)8(CNBut)){
l
3-Ph2PCH2P(Ph)C6H4}(
(3) in 39% yield which decarbonylates at 110 °C to give [Os3
(CO)7(CNBut){
3-Ph2PCHP(Ph)C6H4}( -H)2] (4) in 45% yield
l-H)]
l
l
t
(Scheme 3). Compound 3 is an adduct of 2 and BuNC whereas
Table 1
Crystallographic data for 3, 6, 8 and 10
3
6
8
10
Empirical formula
Formula weight (Å)
Temperature (K)
Wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
C41H37NO8Os3P2
1304.26
150(2)
0.71073
Monoclinic
C2/c
C39H31NO9Os3P2
1290.19
293(2)
C22H16N2O9Os3S
1055.03
150(2)
0.71073
Monoclinic
P21/c
C39H31N2O8Os3PS
1289.21
293(2)
0.71073
0.71073
Triclinic
Triclinic
ꢀ
ꢀ
P1
P1
21.4807(14)
32.796(2)
11.7777(8)
90
11.388(3)
11.807(3)
14.889(4)
83.844(4)
15.668(4)
9.122(3)
20.026(6)
90
15.3857(14)
15.7811(14)
17.1195(15)
92.651(2)
b (Å)
c (Å)
a
(°)
b (°)
100.8740(10)
90
8148.1(9)
81.697(4)
89.544(4)
1969.5(8)
2
2.176
9.789
1204
112.798(4)
90
2638.5(13)
4
2.656
14.543
102.657(2)
101.664(2)
3954.0(6)
c
(°)
Volume (Å3)
Z
8
4
Density (calculated) (Mg/m3)
Absorption coefficient (mmÀ1
F(000)
2.126
9.464
4896
2.166
9.763
2408
)
1912
Crystal size (mm)
h Range for data collection (°)
Index ranges
0.38 Â 0.22 Â 0.20
2.48–28.33
À27 6 h 6 27,
À43 6 k 6 43,
À15 6 1 6 15
34902
9749 [Rint = 0.0378]
Full-matrix least-squares on
F2
0.28 Â 0.12 Â 0.08
2.50–28.28
À14 6 h 6 15,
À15 6 k 6 15,
À19 6 1 6 19
17021
9020 [Rint = 0.0399]
Full-matrix least-squares on
F2
0.32 Â 0.14 Â 0.08
2.64–28.33
À20 6 h 6 20,
À12 6 k 6 12,
À26 6 1 6 25
21818
6290 [Rint = 0.0592]
Full-matrix least-squares on
F2
0.18 Â 0.05 Â 0.03
1.22 to 28.29
À20 6 h 6 20,
À20 6 k 6 20,
À22 6 l 6 22
34561
18147 [Rint = 0.0523]
Full-matrix least-squares on
F2
Reflections collected
Independent reflections
Refinement method
Data/restraints/parameters
9749/0/516
0.859
9020/0/488
0.932
6290/0/339
1.094
18147/0/908
0.920
Goodness-of-fit on F2
Final R indices [I > 2
r
(I)]
R1 = 0.0261,
wR2 = 0.0696
R1 = 0.0314,
wR2 = 0.0727
1.497 and À1.139
R1 = 0.0383,
wR2 = 0.0959
R1 = 0.0458,
wR2 = 0.1002
3.117 and À1.707
R1 = 0.0411,
wR2 = 0.0983
R1 = 0.0447,
wR2 = 0.1003
5.399 and À1.925
R1 = 0.0470,
wR2 = 0.0991
R1 = 0.0800,
wR2 = 0.1225
2.779 and À2.324
R indices (all data)
Largest difference in peak and hole
(e ÅÀ3
)

A.K. Raha et al. / Journal of Organometallic Chemistry 693 (2008) 3613–3621
3617
Ph
P
(CO)3
Os
Ph2
P
Os
(OC)4
Os
(OC)3
Os
P
110 oC
- 2CO
(CO)3
Os
P
H
Os
(CO)3 Ph2
(CO)2 Ph2
2
1
CNBut
RT
MeCN
RT
Me3NO
Ph
P
NCMe
Os
OC
OC
(CO)3
Os
Ph2
P
Os
(OC)3
Os
(CO)3
(CO)2
Os
OC
Os
P
H
P
(CO)3 Ph2
Ph2
tBuNC
5
3
110 oC
CNBut
RT
Ph
P
CNBut
Os
CH
H
OC
OC
(CO)3
Os
Ph2
Os
(OC)2
Os
P
(CO)3
P
110 oC
(CO)2
Os
OC
H
Os
P
Ph2
(CO)3 Ph2
tBuNC
6
4
Scheme 3.
2.021(4) Å} are quite similar to those observed in related com-
plexes [10,30] while the Os–P and C–N bond distances are within
the range found in literature [11,30–33].
The spectroscopic data for 3 are consistent with the solid-state
structure. The infrared spectrum shows the mCN absorption band at
groups which is consistent with our assigned formulation. The 1H
NMR spectrum of 4 displays two sets of hydride resonances at d
À13.86 and À16.85 indicating that intramolecular activation of
two C–H bonds has taken place. In addition to the usual aromatic
resonances for phenyl protons, the aliphatic region of the spectrum
shows a doublet of doublets at d 5.10 (JP–H = 11.7, 4.0 Hz) with a
relative intensity of 1H for the methylene proton of the dppm li-
gand and a singlet at d 1.41 (integrated to 9H) due to the methyl
2178 cmÀ1, which is characteristic of a terminally coordinated iso-
cyanide ligand [34]. The FAB mass spectrum shows the parent
molecular ion peak at m/z 1263 and peaks due to sequential loss
of eight carbonyl groups. The hydride region of the 1H NMR spec-
trum shows a doublet at d À16.62 (JP–H = 7.6 Hz) indicating the
presence of a hydride coupled to a phosphorus atom while the
31P-{1H} NMR spectrum displays two doublet resonances at d
12.7 (JP–P = 75.6 Hz,) and 16.5 (JP–P = 75.6 Hz) due to nonequivalent
phosphorus atoms of the dppm ligand.
t
protons of the BuNC ligand which suggest that one of the methy-
lene protons of the dppm ligand has been activated. On the other
hand, the 31P-{1H} NMR spectrum shows two doublets at d À13.7
(JP–P = 53.5 Hz) and À61.8 (JP–P = 53.5 Hz) for the phosphorus
atoms of the dppm ligand which is in accord with our proposed
structure.
Since we were unable to grow single crystals of 4 in different
solvent systems under different conditions, its molecular structure
was deduced from spectroscopic data and elemental analysis. The
infrared spectrum shows a strong absorption band at 2183 cmÀ1
for the terminally coordinated BuNC ligand [34] while the car-
bonyl region of the spectrum is very similar to that observed for
3.2. Reaction of the labile complex [Os3(CO)9(
with BuNC
l
-dppm)(NCMe)] (5)
t
t
In a related study, we carried out the reaction of the labile ace-
tonitrile complex [Os3(CO)9( -dppm)(NCMe)] (5) derived from the
decacarbonyl compound [Os3(CO)10
l
t
[Os3(CO)7(CNPr){l3-Ph2PCHP(Ph)C6H4}(
l-H)2]
[30]
which
(l-dppm)] (1) with BuNC to
indicates that they have similar distribution of carbonyl ligands.
The FAB mass spectrum exhibits the parent molecular ion peak
at m/z 1235 and peaks due to successive loss of seven carbonyl
observe the effect of isocyanide–carbonyl replacement at the
unique metal of 1. Compound 5 reacts with tBuNC at room temper-
ature to give the simple substitution product [Os3(CO)9

3618
A.K. Raha et al. / Journal of Organometallic Chemistry 693 (2008) 3613–3621
Fig. 1. Molecular structure of [Os3(CO)8{l3-Ph2PCH2P(Ph)C6H4}(l-H)] (3) showing
Fig. 2. Molecular structure of [Os3(CO)9(l
-dppm)(CNBut)] (6) showing 50% prob-
50% probability thermal ellipsoids. Hydrogen atoms are omitted for clarity. Selected
bond lengths (Å) and angles(°): Os(1)–Os(2) 2.8961(3), Os(1)–Os(3) 3.0546(3),
Os(2)–Os(3) 2.8714(3), Os(1)–C(1) 2.021(4), Os(3)–C(32) 2.170(4), Os(1)–P(1)
2.3837(11), Os(2)–P(2) 2.3575(11), C(1)–N(1) 1.153(5), C(10)–N(1) 1.467(5), C(3)–
Os(1)–Os(3) 138.92(13), C(2)–Os(1)–Os(3) 117.65(13), P(1)–Os(1)–Os(2) 89.03(3),
Os(2)–Os(1)–Os(3) 57.627(6), Os(3)–Os(2)–Os(1) 63.959(5), Os(2)–Os(3)–Os(1)
58.413(6), P(2)–Os(2)–Os(1) 88.63(3), C(32)–Os(3)–Os(2) 93.69(11), C(9)–Os(3)–
Os(1) 111.60(14), C(32)–Os(3)–Os(1) 96.17(11), C(7)–Os(3)–Os(1) 149.69(15),
C(8)–Os(3)–Os(1) 88.93(12), P(1)–C(14)–P(2) 107.6(2).
ability thermal ellipsoids. Hydrogen atoms are omitted for clarity. Selected bond
lengths (Å) and angles (°): Os(1)–Os(2) 2.8514(6), Os(1)–Os(3) 2.8772(6), Os(2)–
Os(3) 2.8703(7), Os(2)–C(10) 2.034(6), Os(1)–P(1) 2.3105(17), Os(3)–P(2)
2.3424(17), C(11)–N(1) 1.458(8), C(10)–N(1) 1.149(8), P(1)–Os(1)–Os(3) 92.21(4),
P(2)–Os(3)–Os(1) 93.90(4), Os(2)–Os(1)–Os(3) 60.137(18), Os(1)–Os(2)–Os(3)
60.379(14), Os(2)–Os(3)–Os(1) 59.484(10), C(10)–N(1)–N(11) 178.0(7), P(1)–
C(15)–P(2) 117.5(4).
(
l
-dppm)(CNBut)] (6) in which the MeCN group is replaced by the
3.3. Reaction of the unsaturated 2-methylbenzothiazole triosmium
t
tBuNC in 51% yield. Decarbonylation of 6 at 110 °C again furnishes
4 in 51% yield (Scheme 3). The structure of compound 6 is similar
cluster [Os3(CO)9{l3
-
g
2-C7H3(2-Me)NS}(
l-H)] (7) with BuNC
to the PhCH2NC analog [Os3(CO)9(CNCH2Ph)(
l-dppm)] [30]. An
The unsaturated cluster [Os3(CO)9{l3
-
g2-C7H3(2-Me)NS}(
(7) reacts with BuNC at room temperature to furnish the adduct
[Os3(CO)9(CNBut){ g2-C7H3(2-Me)NS}(
-H)] (8) which decarb-
onylates at 110 oC to give unsaturated cluster [Os3(CO)8(CN-
l-H)]
t
ORTEP drawing of the molecular structure of 6 is shown in Fig. 2
and selected bond distances and angles are listed in the caption.
The molecule consists of a trimetallic core of three osmium atoms,
nine terminal carbonyl groups, a bridging dppm ligand and a
terminal tBuNC ligand. The three osmium atoms form an isosceles
triangle with two long {Os(1)–Os(3) = 2.8772(6) and Os(2)–
Os(3) = 2.8703(7) Å} and one short {Os(1)–Os(2) = 2.8514(6) Å}
metal-metal edge. Each osmium atom is coordinated by three car-
bonyl ligands and the tBuNC ligand is axially coordinated to Os(2).
The bridging dppm ligand lie in the equatorial plane and the Os–P
bond lengths are very similar to those observed in [Os3
(CO)9(CNCH2Ph)(l-dppm)] [30]. The Os(2)–C(10) bond distance
{2.034(6) Å} and the C–N bond distances within the BuNC ligand
{C(11)–N(1) = 1.458(8), C(10)–N(1) = 1.149(8) Å} are also similar
to those found in 3 and [Os3(CO)9(CNCH2Ph)(l-dppm)] [30].
The infrared spectrum of compound 6 shows a characteristic
absorption band for a terminally coordinated isocyanide ligand at
2178 cmÀ1 [34] while the carbonyl region of the spectrum is very
l-
l
But){l3 g2-C7H3(2-Me)NS}(
- l-H)] (9) (Scheme 4). Compounds 8
and 9 have been characterized by IR, 1H and 31P-{1H} NMR, mass
spectroscopy and elemental analysis together with a single crystal
X-ray diffraction study for 8.
An ORTEP drawing of the molecular structure of [Os3(CO)9(CN-
But){ g2-C7H3(2-Me)NS}(
l- l-H)] (8) is depicted in Fig. 3 and se-
lected bond distances and angles are listed in the caption. The
molecule consists of an isosceles triangle of osmium atoms with
one short {Os(1)–Os(3) = 2.8910(7) Å} and two longer bonds
{Os(1)–Os(2) = 2.9136(8) and Os(2)–Os(3) = 2.9150(8) Å}, each of
which is bonded to three terminal carbonyl groups. The hydride li-
gand is located crystallographically but not refined. Both the het-
erocyclic ligand and hydride bridge the same metal–metal edge.
t
t
The BuNC ligand is axially coordinated to Os(1), with the Os(1)–
C(10) bond distance {2.039(7) Å} very similar to those found in 3
and 6 and oriented on the opposite side of the Os3 plane relative
to the heterocyclic ligand. The heterocyclic ligand is roughly per-
pendicular to the Os3 plane with the C(15)–Os(2)–Os(3) and
N(1)–Os(3)–Os(2) angles being 84.52(18) and 84.50(16)°, respec-
tively. The dihedral angle between the Os3 plane and the mean
plane of the heterocyclic ligand is 98.4o. The Os(2)–C(15) and
Os(3)–N(1) distances {2.148(7) and 2.174(6) Å} are within the
range reported for related compounds [17–22,35–38].
similar to that of [Os3(CO)9(CNCH2Ph)(l-dppm)] [30]. In addition
to the usual aromatic resonances for phenyl protons, the 1H NMR
spectrum shows a multiplet at d 5.05 for the methylene protons
of the dppm ligand while the 31P-{1H} NMR spectrum displays a
singlet at d À27.3 for the phosphorus atoms of the dppm ligand.
The FAB mass spectrum shows the parent molecular ion peak at
m/z 1291 and peaks due to stepwise loss of nine carbonyl ligands
which also supports the solid-state structure.

A.K. Raha et al. / Journal of Organometallic Chemistry 693 (2008) 3613–3621
3619
S
S
Me
Me
N
N
CNBut
RT
H
(OC)3Os
Os(CO)3
(OC)3Os
Os(CO)3
CO
Os
H
Os
(CO)3
CO
OC
CNBut
7
8
+ CO
- CO
S
S
Me
Me
Os(CO)3
N
N
H
Ph3P
Os
PPh3
RT
(OC)3Os
Os(CO)3
OC
OC
CO
Os
H
Os
CNBut
CO
CO
OC
OC
CNBut
10
9
Scheme 4.
the parent molecular ion peak at m/z 1056 and peaks due to
sequential loss of nine carbonyl groups which is consistent with
the solid-state structure.
Single crystals of compound 9 could not be obtained after sev-
eral attempts, so its molecular structure was deduced from ele-
mental analysis and spectroscopic data. The infrared spectrum
exhibits the m
CN absorption band at 2164 cmÀ1 which is character-
istic of a terminally coordinated isocyanide ligand [34] while the
FAB mass spectrum exhibits the parent molecular ion peak at
m/z 1028 together with fragment peaks due to successive loss of
eight carbonyl groups which is in accord with our proposed formu-
lation. The 1H NMR spectrum exhibits a hydride resonance at d
À12.93 while the aromatic region of the spectrum displays three
equal intensity multiplets at d 8.43, 8.35 and 6.94 due to the ring
protons of the heterocylic ligand. In addition to this, the aliphatic
region shows two singlets at d 2.96 and 1.41 with a relative inten-
sity of 1:3 for the methyl protons of the heterocyclic ligand and the
tBuNC ligand respectively which are consistent with our proposed
structure.
3.4. Reaction of the unsaturated cluster [Os3(CO)8(CNBut){l3
- -
g2
Fig. 3. Molecular structure of [Os3(CO)9(CNBut){ g2-C7H3(2-Me)NS}(
l- l-H)] (8)
C7H3(2-Me)NS}( -H)] (9) with CO and PPh3
l
showing 50% probability thermal ellipsoids. Hydrogen atoms are omitted for clarity.
Selected bond lengths (Å) and angles (°): Os(1)–Os(2) 2.9136(8), Os(1)–Os(3)
2.8910(7), Os(2)–Os(3) 2.9150(8), Os(1)–C(10) 2.039(7), Os(2)–C(15) 2.148(7),
Os(3)–N(1) 2.174(6), C(11)–N(2) 1.453(10), C(10)–N(2) 1.144(10), C(6)–Os(2)–
Os(3) 119.0(2), C(15)–Os(2)–Os(3) 84.52(18), C(7)–Os(3)–Os(2) 123.3(2), Os(3)–
Os(1)–Os(2) 60.289(17), Os(1)–Os(2)–Os(3) 59.471(10), Os(1)–Os(3)–Os(2)
60.24(2), N(1)–Os(3)–Os(2) 84.50(16), C(10)–N(2)–C(11) 172.6(7).
The electron deficiency in compound 9 has been demonstrated
by its reactions with CO and PPh3. Treatment of 9 with CO (1 atm)
S
N
S
N
Me
Os(CO)3
Me
Os(CO)3
The 1H NMR spectrum of 8 shows one major isomer (relative
intensity = 0.95) in solution with a hydride signal at À11.88. In
addition a second hydride resonance is observed at À12.07 (rela-
tive intensity = 0.05). The major isomer 8a is assumed to have
the same structure as found in the solid-state, while the minor iso-
mer 8b has an alternative position for the isocyanide ligand (Chart
H
H
(OC)3Os
(OC)3Os
tBuNC
OC
Os
Os
CO
CO
OC
OC
CNBut
CO
8a
8b
1) [27]. The infrared spectrum shows the characteristic
mCN absorp-
tion band at 2178 cmÀ1 whereas the FAB mass spectrum exhibits
Chart 1.

3620
A.K. Raha et al. / Journal of Organometallic Chemistry 693 (2008) 3613–3621
at room temperature leads to the quantitative formation of 8.
S
N
S
N
Me
Me
Similarly reaction of
9
with PPh3 affords the adduct
[Os3(CO)8(PPh3)(CNBut){
l
-g
2-C7H3(2-Me)NS(
l-H)] (10) in 56%
H
H
Ph3P
OC
Ph3P
OC
yield. In order to establish the molecular geometry and in particu-
lar to obtain precise details on the disposition of the PPh3 and the
isocyanide ligand, crystal structure analysis of 10 was undertaken.
The asymmetric unit contains two chemically indistinguishable
molecules and an ORTEP diagram of the molecular structure of
one of these is shown in Fig. 4 and selected bond distances and an-
gles are listed in the caption. The structure consists of an irregular
triangle of osmium atoms {Os(4)–Os(5) = 2.8723(6), Os(5)–
Os(6) = 2.8877(5) and Os(4)–Os(6) = 2.9323(5) Å}, two of which
(Os(4) and Os(5)) are coordinated by three carbonyl ligands, while
the other, Os(6), is coordinated by two carbonyls. The hydride li-
gand was not located in the X-ray experiment but from the length-
ening of the Os(4)–Os(6) edge, and from the opening out of the
carbonyl ligands along this edge {C(11)–Os(4)–Os(6) = 115.8(3)°},
it seems it is likely that it is located on the Os(4)–Os(6) edge. The
heterocyclic ligand bridges the same edge, as in 8, and is almost
perpendicular to the Os3 plane, as shown by the C(60)–Os(6)–
Os(5) and N(3)–Os(4)–Os(5) angles of 91.4(2) and 90.2(2)°,
respectively. The dihedral angle between the mean plane of the
heterocyclic ligand and the plane of the three metal atoms is
85.2o. The tBuNC ligand is axially coordinated Os(5) and is oriented
in the opposite side of the Os3 plane with respect to the heterocy-
clic ligand, similarly to 8. The PPh3 ligand occupies an equatorial
coordination site and is located under the C-7 carbon of the hetero-
cyclic ligand as in related complexes reported in literature [18,19].
The NMR spectrum indicates that compound 10 exists in four
isomeric forms in solution (Chart 2) [27,36]. In the 1H NMR spec-
trum the major isomer 10a (relative intensity = 0.89) is assumed
to have the solid-state structure and shows a hydride signal at d
À11.15 (d, J = 16.4 Hz). In addition, we observe three additional
weak hydride resonances at d À11.35 (d, J = 16.4 Hz), À12.41 (d,
J = 16.4 Hz) and À15.20 (d, J = 16.4 Hz) (relative intensity = 0.03,
0.03, 0.05). The equal and relatively large JP–H values are consistent
Os
Os(CO)3
Os
Os(CO)3
CO
Os
CO
Os
OC
OC
CO
CO
OC
OC
CNBut
CNBut
10a
10b
S
S
Me
Me
N
N
PPh3
CO
PPh3
CO
H
CO
Os
H
(OC)3Os
Os
CO
(OC)3Os
Os
CO
CNBut
Os
CO
CO
OC
OC
CNBut
10d
CO
10c
Chart 2.
with our proposed structures for the isomers since the phosphine
ligand is stereochemically equivalent relative to the hydride in
all isomers [36]. The 31P-{1H} NMR spectrum also displays four
singlets at d 12.8, 12.1, 10.0 and 0.5 (relative intensity = 0.05,
0.89, 0.03, 0.03). The infrared spectrum exhibits a strong absorp-
tion band at 2178 s cmÀ1 characteristic for terminally coordinated
isocyanide ligand while the FAB mass spectrum shows the parent
molecular ion peak at m/z 1289 and peaks due to sequential loss
of eight terminal carbonyl ligands which are consistent with the
solid-state structure.
4. Conclusions
t
In summary, reaction of the unsaturated cluster 2 with BuNC
gives the adduct 3 which on decarbonylation furnishes the unusual
saturated cluster 4 in which both aromatic and aliphatic C–H bond
activation has occurred. Similar reaction of the unsaturated cluster
7 with tBuNC affords the addition product 8 which decarbonylates
to give the unsaturated cluster 9. This difference is difficult to ex-
plain in the absence of detailed knowledge of the reaction path-
way. Some feature of the substitution of the isocyanide for CO
prevents the reformation of a three-center two-electron bond,
involving two osmium atoms and the carbon atom of the ortho-
metallated phenyl ring, in 4. In addition, decarbonylation of 6,
t
the BuNC derivative of the decacarbonyl compound 1, also fur-
nishes 4, again pointing to the special impact of this ligand on
the formation of the 3-center 2-electron bonding mode. Subse-
quent reaction of the unsaturated cluster 9 with PPh3 again affords
the saturated cluster 10 in which the phosphine ligand lies under
the C-7 carbon of the heterocyclic ligand as in other related unsat-
urated triosmium clusters [18,19]. Thus, we conclude that isocya-
nide–carbonyl replacement modifies the chemical behavior of the
unsaturated cluster 2 while it has virtually no effect on that of
the unsaturated cluster 7.
Fig. 4. Molecular structure of [Os3(CO)8(PPh3)(CNBut){ 2-C7H3(2-Me)NS(
l-g l-H)]
(10) showing 50% probability thermal ellipsoids. Hydrogen atoms are omitted for
clarity. Selected bond lengths (Å) and angles (°): Os(4)–Os(5) 2.8723(6), Os(5)–
Os(6) 2.8877(5), Os(4)–Os(6) 2.9323(5), Os(6)–C(60) 2.161(10), Os(5)–C(48)
2.058(12), Os(6)–P(2) 2.350(2), Os(4)–N(3) 1.169(8), C(48)–N(4) 1.121(13), C(49)–
N(4) 1.472(13), Os(5)–Os(4)–Os(6) 59.657(14), Os(4)–Os(5)–Os(6) 61.204(13),
Os(5)–Os(6)–Os(4) 59.139(14), P(2)–Os(6)–Os(5) 167.73(6), P(2)–Os(6)–Os(4)
109.48(6), C(11)–Os(4)–Os(6) 115.8(3), N(3)–Os(4)–Os(5) 90.2(2), N(3)–Os(4)–
Os(6) 83.9(2), C(48)–Os(5)–Os(4) 91.5(3), C(60)–Os(6)–Os(5) 91.4(2), C(48)–
Os(5)–Os(6) 90.5(3), C(48)–N(4)–C(49) 173.3(11), N(4)–C(48)-–Os(5) 171.7(9).
Supplementary material
CCDC 655913, 655914, 655915 and 673204 contain supplemen-
tary crystallographic data for 3, 6, 8 and 10, respectively. These
data may be obtained free of charge from The Cambridge Crystal-
lographic Data Center via www.ccdc.cam.ac.uk/data_request/cif.

A.K. Raha et al. / Journal of Organometallic Chemistry 693 (2008) 3613–3621
3621
[18] E. Rosenberg, M.J. Abedin, D. Rokhsana, A. Viale, W. Dastru’, R. Gobetto, L.
Milone, Inorg. Chim. Acta 334 (2002) 343.
Acknowledgements
[19] E. Arcia, E. Rosenberg, D.S. Kolwaite, K.I. Hardcastle, J. Ciurash, R. Duque, R.
Gobetto, L. Milone, D. Osella, M. Botta, W. Dastru’, A. Viale, J. Fiedler,
Organometallics 17 (1998) 415.
[20] M.J. Abedin, B. Bergman, R. Holmquist, R. Smith, E. Rosenberg, J. Ciurash, K.I.
Hardcastle, J. Roe, V. Vazquez, C. Roe, S.E. Kabir, B. Roy, S. Alam, K.A. Azam,
Coord. Chem. Rev. 190–192 (1999) 975.
A. K. R. gratefully acknowledges the University Grants Commis-
sion of Bangladesh for a scholarship and the Ministry of Education,
Government of the People’s Republic of Bangladesh for a study
leave.
[21] (a) E. Rosenberg, D. Rokhsana, C. Nervi, R. Gobetto, L. Milone, A. Vile, J. Fiedler,
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