Triphenylphosphine-substituted selenido and sulfido clusters of osmium derived from Ph3PSe or Ph3PS

Article abstract of DOI:10.1016/j.jorganchem.2005.07.038

Cleavage of PSe bonds occurs readily in the room-temperature treatment of [Os₃(CO)₁₀(MeCN)₂] with Ph₃PSe to give three new compounds, [Os₃(μ₃-Se) ₂(CO)₈(PPh₃)] (2), [Os₃(μ ₃-Se)(μ₃-CO)(CO)₇(PPh₃) ₂] (5) and [Os₃(μ-OH)₂(CO) ₈(PPh₃)₂] (6), respectively, and three known compounds, [Os₃(μ₃-Se)₂(CO)₉] (1), [Os₃(μ₃-Se)(μ-CO)₂(CO) ₇(PPh₃)] (3), and 1,2-[Os₃(CO) ₁₀(PPh₃)₂] (4).No evidence for any product containing a co-ordinated Ph₃PSe ligand was obtained.The analogous reaction between [Os₃(CO)₁₀(MeCN)₂] and Ph ₃PS produces five new compounds [Os₃(μ₃-S) ₂(CO)₈(PPh₃)] (7), [Os₃(μ ₃-S)(μ-CO)₂(CO)₇(PPh₃)] (8), [Os₃(μ₃-S)(μ₃- CO)(CO) ₇(PPh₃)₂] (9), [Os₃(μ ₃-)₂(CO)₇(PPh₃)₂] (11) and compound 6 in addition to the known compound 4. Treatment of 2 with Me ₃NO at 50 °C gives the trinuclear cluster [Os₃(μ ₃-Se)₂(CO)₇(PPh₃)(NMe₃)] (13) and the hexanuclear cluster [Os₆(μ₃-Se) ₄(CO)₁₄(PPh₃)₂] (12). Treatment of compound 1 with PPh₃ and Me₃NO at room temperature gives [Os₃(μ₃-Se)₂(CO)₇(PPh ₃)₂] (10). Compound 2 reacts with PPh₃ similarly to give 10. Compound 3 reacts with elemental selenium at 110 °C to give 2. The new compounds 2, 5, 6 and 8 were characterized by single-crystal X-ray diffraction. The compounds 3, 5, 8 and 9 contain Os₃(μ ₃-S) or Os₃(μ₃-Se)cluster cores with three metal-metal bonds while 2, 7, 10, 11 and 12 contain Os₃(μ ₃-S)₂or Os₃(μ₃-Se)₂ cores two metal-metal bonds. The two hydroxy ligands in the triosmium cluster 6 bridging the open osmium-osmium edge and are probably derived from water. A study of the dynamic exchange of PPh₃ ligands in 5 is also reported.

Full text of DOI:10.1016/j.jorganchem.2005.07.038

Journal of Organometallic Chemistry 690 (2005) 4628–4639
www.elsevier.com/locate/jorganchem
Triphenylphosphine-substituted selenido and sulfido clusters
of osmium derived from Ph3P@Se or Ph3P@S
Hamida Akter , Antony J. Deeming ,b, G.M. Golzar Hossain , Shariff E. Kabir
,
a
c
a,
*
*
a
d
a
b
Dwijendro N. Mondol , Ebbe Nordlander , Ayesha Sharmin , Derek A. Tocher
a
Department of Chemistry, Jahangirnagar University, Savar, Dhaka 1342, Bangladesh
Department of Chemistry,University College London, 20 Gordon Street, London WC1H 0AJ, UK
b
c
Department of Chemistry, Cardiff University, P.O. Box 912, Cardiff CF10 3TB, UK
Inorganic Chemistry, Center for Chemistry and Chemical Engineering, Lund University, Box 124, S-22100 Lund, Sweden
d
Received 24 June 2005; received in revised form 8 July 2005; accepted 11 July 2005
Available online 24 August 2005
Abstract
Cleavage of P@Se bonds occurs readily in the room-temperature treatment of [Os3(CO)10(MeCN)2] with Ph3P@Se to give three
new compounds, [Os3(l3-Se)2(CO)8(PPh3)] (2), [Os3(l3-Se)(l3-CO)(CO)7(PPh3)2] (5) and [Os3(l-OH)2(CO)8(PPh3)2] (6), respec-
tively, and three known compounds, [Os3(l3-Se)2(CO)9] (1), [Os3(l3-Se)(l-CO)2(CO)7(PPh3)] (3), and 1,2-[Os3(CO)10(PPh3)2] (4).
No evidence for any product containing a co-ordinated Ph3P@Se ligand was obtained. The analogous reaction between [Os3(CO)10-
(MeCN)2] and Ph3P@S produces five new compounds [Os3(l3-S)2(CO)8(PPh3)] (7), [Os3(l3-S)(l-CO)2(CO)7(PPh3)] (8), [Os3(l3-
S)(l3- CO)(CO)7(PPh3)2] (9), [Os3(l3-)2(CO)7(PPh3)2] (11) and compound 6 in addition to the known compound 4. Treatment of
2 with Me3NO at 50 ꢀC gives the trinuclear cluster [Os3(l3-Se)2(CO)7(PPh3)(NMe3)] (13) and the hexanuclear cluster [Os6(l3-
Se)4(CO)14(PPh3)2] (12). Treatment of compound 1 with PPh3 and Me3NO at room temperature gives [Os3(l3-Se)2(CO)7(PPh3)2]
(10). Compound 2 reacts with PPh3 similarly to give 10. Compound 3 reacts with elemental selenium at 110 ꢀC to give 2. The
new compounds 2, 5, 6 and 8 were characterized by single-crystal X-ray diffraction. The compounds 3, 5, 8 and 9 contain
Os3(l3-S) or Os3(l3-Se)cluster cores with three metal–metal bonds while 2, 7, 10, 11 and 12 contain Os3(l3-S)2or Os3(l3-Se)2 cores
two metal–metal bonds. The two hydroxy ligands in the triosmium cluster 6 bridging the open osmium-osmium edge and are prob-
ably derived from water. A study of the dynamic exchange of PPh3 ligands in 5 is also reported.
ꢁ 2005 Elsevier B.V. All rights reserved.
Keywords: Osmium carbonyl clusters; Triphenylphosphine selenide; Triphenylphosphine sulfide; Crystal structures
1. Introduction
adopted and the triply-bridging sulfido ligand in particu-
lar has been exploited for the purpose of cluster growth
[2,3]. The larger tellurium atom stabilizes triangular
and square arrays of metal atoms [4]. Selenido ligands
should be similarly useful but have been studied rather
less [5]. Lewis et al. [6] reported that [Os3(CO)12] reacts
with elemental chalcogens in refluxing octane to give
[Os3(l-H)2(l3-X)(CO)9], [Os3(l3-X)2(CO)9] and [Os4(l-
H)2(l3-X)2(CO)12] (X = S, Se or Te), but a CO/H2 pres-
sure is required to prepare the ruthenium analogues
[Ru3(l-H)2(l3-X)(CO)9] and [Ru3(l3-X)2(CO)9]. It has
recently been reported that the treatment of Fe and Ru
Having a high affinity for later transition metals, chal-
cogen atoms are readily incorporated into transition-me-
tal carbonyl clusters [1]. Many different coordination
modes and geometries of the chalcogen atoms are
*
Corrresponding author. Present address: Department of Chemis-
try, University of Montana, 32 Campus Drive, Missoula, MT 59812,
USA. Tel.: +1 406 243 2592; fax: +1 406 243 2477.
E-mail addresses: a.j.deeming@ucl.ac.uk (A.J. Deeming), skabir_
ju@yahoo.com (S.E. Kabir).
0022-328X/$ - see front matter ꢁ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.07.038

H. Akter et al. / Journal of Organometallic Chemistry 690 (2005) 4628–4639
4629
carbonyl complexes with R3P@Se provides a simple,
one-step synthesis of phosphine-substituted selenido
clusters through oxidative transfer of the selenium to
low-valent metal clusters [7]. For example, Cauzzi et al.
[7a] reported the synthesis of tertiary phosphine-substi-
tuted selenido carbonyl Fe or Ru clusters in this way.
For Ru, the reaction selectively gives the disubstituted
trinuclear cluster [Ru3(l3-Se)2(CO)7(PPh3)2] in high
yield, together with only minor amounts of [Ru3-
(l3-Se)2(CO)8(PPh3)] and [Ru4(l4-Se)2(l-CO)2-(CO)7-
(PPh3)2]. In contrast the reaction for Fe afforded a series
of di- and tri-nuclear compounds. Although a range of
PPh3 derivatives of Ru and Fe compounds containing
Se ligand from Ph3P@Se has been described by Cauzzi
and co-workers, relatively little is known of the corre-
sponding Os chemistry. Adams et al. [8] recently reported
some Mn and mixed Fe-Mn carbonyl clusters containing
PPh3 and l3-Se ligands from the reactions of Ph3P@Se
with [Mn2(CO)9(MeCN)] and [CpFeMn-(CO)7] while
Braunstein et al. [9] reported mixed metal tri- and
tetra-nuclear clusters capped by Se ligands from treat-
ment of [MCo3(l-H)(CO)12] (M = Fe or Ru) with vari-
ous phosphine selenides. Applying this approach we
have synthesized compounds containing bridging dppm
and capping Se ligands from the reactions of [Os3-
(CO)10(MeCN)2] with dppmSe and dppmSe2 and used
these for the synthesis of higher nuclearity compounds
[10]. We now report the synthesis of some PPh3 substi-
tuted triosmium compounds containing capping Se and
S ligands from room-temperature reactions of [Os3
(CO)10(MeCN)2] with Ph3P@Se and Ph3P@S. During
the progress of this work Leong et al. [11] reported some
Os–Se compounds from the reactions of [Os3(CO)11-
(MeCN)] and [Os3(CO)10(MeCN)2] with Ph3P@Se, but
our results from similar investigations are significantly
different from theirs and in particular we have repeatedly
observed a wider range of products than they report.
2. Results and discussion
The lightly stabilized cluster [Os3(CO)10(MeCN)2]
reacts with Ph3P@Se at room temperature to give three
new compounds [Os3(l3-Se)2(CO)8(PPh3)] (2), [Os3(l3-
Se)(l3-CO)(CO)7(PPh3)2] (5) and [Os3(l-H)2(CO)8-
(PPh3)2] (6) in 10%, 16% and 7% yields, respectively,
and three previously reported compounds [Os3(l3-Se)-
(l-CO)2(CO)7(PPh3)] (3), [Os3(l3-Se)2(CO)9] (1) and
1,2-[Os3(CO)10(PPh3)2] (4) in 15%, 12% and 7% yields,
respectively (Scheme 1). We obtained no evidence for
[Os3(CO)10(MeCN)2]
CH2Cl2
+
Ph3P=E (E = Se, S)
25 O
C
(CO)3
Os
(CO)3
Os
(CO)3
Os
O
E
C
Se
E
E
Se
Os
(CO)3
(CO)(PPh )
Os
3
Os(CO)2(PPh3)
(CO)
3 Os
Os (CO)3
(CO)3 Os
C
O
2 (E = Se)
7 (E = S)
1
3 (E = Se)
8 (E = S)
(CO)3
Os
(CO)4
Os
CO
E
(PPh3)(CO)
3 Os
Os(CO)3(PPh3)
Os
(PPh3)(CO)2
(CO) (PPh )
Os
2
3
5 (E = Se)
9 (E = S)
4
(CO)4
Os
(CO)3
Os
E
E
OH
Os
(PPh3)(CO)2
Os (CO)2(PPh3)
(CO) (PPh )
(PPh3)(CO)2 Os
Os
2
3
OH
6
11 (E = S)
Scheme 1.

Table 1
Crystal data and structure refinement for 2, 5, 6 and 8
Complex
2
5
6
8
Chemical formula
Formula weight
T (K)
k (A)
Space group
C
26H15O8Os3PSe2
C44H30O8Os3P2Se Æ CH2Cl2
1483.11
150(2)
C44H32O10Os3P2
1353.24
150(2)
0.71073
P21/n
C27H15O9Os3PS
1117.02
150(2)
0.71073
P21/n
1214.87
293(2)
0.71073
˚
0.71073
ꢀ
ꢀ
P1
P1
Unit cell parameters
˚
a (A)
8.8222(6)
12.6657(9)
10.60210(10)
11.3496(2)
13.1197(6)
17.8055(8)
14.7118(9)
9.6925(6)
˚
b (A)
˚
c (A)
14.7417(10)
69.4710(10)
76.5650(10)
83.0960(10)
1499.05(18)
2
2.691
15.209
1092
0.44 · 0.21 · 0.14
1.72–28.29
À11 6 h 6 11,
À16 6 k 6 16,
À18 6 l 6 19
13307
6906
0.0388
20.3179(3)
89.7097(8)
87.1785(8)
66.6625(6)
2241.83(6)
2
2.197
9.359
1384
0.24 · 0.16 · 0.16
2.95–27.49
À13 6 h 6 13,
À23 6 k 6 23,
À26 6 l 6 26
37690
10185
0.0772
8989
17.5309(18)
90
94.4190(10)
90
4081.4(3)
4
2.202
9.455
2536
0.23 · 0.15 · 0.08
1.87–28.29
À17 6 h 6 17,
À14 6 k 6 14,
À22 6 l 6 22
35789
9715
0.0283
8989
20.3593(12)
90
99.2290(10)
90
2865.5(3)
4
2.589
13.450
2032
0.38 · 0.16 · 0.12
1.59–28.30
À18 6 h 6 18,
À12 6 k 6 12,
l À27 6 l 6 27
24769
6834
0.0361
6419
a (ꢀ)
b (ꢀ)
c (ꢀ)
3
˚
V (A )
Z
Dcalc (g/cm3)
Absorption coefficient l (mmÀ1
F(000)
)
Crystal size (mm3)
h Range for data collection (ꢀ)
Index ranges
Reflection collected
Independent reflections
Rint
Reflections with F2 > 2r
5942
Minimum and maximum transmission
Refinement method
Data/restraints/parameters
R indices [F2 > 2r]
R indices (all data)
Goodness-of-fit on F2
0.0573 and 0.2333
Full-matrix least-square on F2
6906/0/463
R1 = 0.0465, wR2 = 0.1125
R1 = 0.0540, wR2 = 0.1178
1.042
0.3107 and 0.2081
Full-matrix least-square on F2
10185/0/550
R1 = 0.0387, wR2 = 0.0919
R1 = 0.0498, wR2 = 0.0978
1.012
0.2197 and 0.5184
Full-matrix least-square on F2
9715/0/540
R1 = 0.0221, wR2 = 0.0430
R1 = 0.0255, wR2 = 0.0439
1.087
0.0799 and 0.2952
Full-matrix least-square on F2
6834/0/371
R1 = 0.0274, wR2 = 0.0560
R1 = 0.0304, wR2 = 0.0572
1.172
Largest and mean shift (su)
Largest difference in peak
0.000 and 0.000
2.189 and À3.071
0.000 and 0.000
2.776 and À2.489
0.004 and 0.000
0.876 and À0.767
0.001 and 0.000
2.515 and À0.945
À3
˚
and hole (e A
)

H. Akter et al. / Journal of Organometallic Chemistry 690 (2005) 4628–4639
4631
Table 2
any clusters with co-ordinated Ph3P@Se ligands so the
˚
Selected bond distances (A) and angles (ꢀ) for [Os3(l3-Se)2(CO)8(PPh3)]
(2)
P@Se bond cleavage to give selenido clusters must occur
rapidly following coordination. This observation is dif-
ferent from that of Ho and Wong [12] who reported
[Os3(CO)10{Ph2(SH)NP(S)Ph2-S,S}] and [(l-H)Os3-
(CO)9{Ph2P(S)NP(S)Ph2-S,S}] containing undissociated
bis(diphenylthiophosphinoyl)amine ligand from the
reaction between [Os3(CO)10(MeCN)2] and Ph2P(S)-
NHP(S)Ph2. The new compounds 2, 5 and 6 have been
characterized spectroscopically and by single-crystal X-
ray diffraction. The solid-state molecular structure of 2
(Fig. 1 and Table 2) consists of an open Os3 cluster with
two metal–metal bonds, eight terminal CO, a PPh3 and
two triply-bridging selenido ligands. The structure was
refined with two equally populated disordered orienta-
tions of the phenyl groups as shown superimposed in
Fig. 1. Both disordered arrangements have the same
Os3(l3-Se)2(CO)8P core structure and small variations
within the core as a result of the disorder are believed
to be insignificant.
Os(1)–Os(3)
Os(2)–Os(3)
Os(1)–Se(1)
Os(2)–Se(2)
Os(2)–Se(1)
Os(3)–Se(1)
Os(3)–Se(2)
Os(1)–Se(2)
Os(2)–P(1)
2.7741(5)
2.8551(5)
2.5074(10)
2.4893(11)
2.5066(9)
2.5535(9)
2.5525(10)
2.5064(11)
2.310(2)
P(1)–Os(2)–Se(2)
P(1)–Os(2)–Se(1)
Os(1)–Os(3)–Os(2)
Se(1)–Os(1)–Os(3)
Se(2)–Os(2)–Se(1)
Se(1)–Os(3)–Os(1)
Se(2)–Os(2)–Os(3)
Se(2)–Os(3)–Os(2)
Os(2)–Se(1)–Os(1)
Os(2)–Se(1)–Os(3)
Os(2)–Se(2)–Os(1)
Os(1)–Se(2)–Os(3)
Se(2)–Os(1)–Se(1)
Se(2)–Os(1)–Os(3)
P(1)–Os(2)–Os(3)
Se(2)–Os(3)–Se(1)
Se(2)–Os(3)–Os(1)
Se(1)–Os(3)–Os(2)
Os(1)–Se(1)–Os(3)
Os(2)-Se(2)–Os(3)
Se(1)–Os(2)–Os(3)
104.21(6)
106.15(5)
85.810(13)
57.56(2)
80.10(3)
55.97(2)
56.56(2)
54.47(2)
99.71(3)
68.69(2)
100.21(3)
66.50(3)
79.76(3)
57.54(3)
153.82(5)
78.04(3)
55.95(3)
54.88(2)
66.47(2)
68.97(3)
56.43(2)
The two Os–Os distances in 2 [Os(1)–Os(3) =
˚
2.7741(5) and Os(2)–Os(3) = 2.8551(5) A] are rather dif-
ferent, with that involving Os(2) bound to the PPh3 li-
gand being longer. The Os(1)Á Á ÁOs(2) separation at
˚
3.833 A is similar to that observed in [Os3(l3-Se)2-
˚
(CO)6(l-dppm)(PPh3)] [3.835 A] [10] but is significantly
˚
longer than that in [Os3(l3-S)2(CO)9] [3.662(1) A] [13].
The Os3Se2 core is square pyramidal with two Os and
two Se atoms alternating in base and the third Os atom at
the vertex. The two Se atoms cap the Os triangle
asymmetrically. The Os–Se distances to the central
seven-coordinate metal atom Os(3) [Os(3)–Se(1) =
˚
˚
2.5535(9) A and Os(3)–Se(2) = 2.5525(10) A] are longer
than those to Os(1) and Os(2), which are in the range
2.4893(11)–2.5074(10) A. The PPh3 ligand is coordinated
˚
Fig. 1. Solid-state molecular structure of [Os3(l3-Se)2(CO)8(PPh3)] (2) showing the two equally populated disordered arrangements of the phenyl
groups of the PPh3 ligand.

4632
H. Akter et al. / Journal of Organometallic Chemistry 690 (2005) 4628–4639
Table 3
at Os(2), trans to an Os–Os bond. The Os–P bond dis-
˚
Selected bond distances (A) and angles (ꢀ) for [Os3(l3-Se)(l3-
CO)(CO)7(PPh3)2] Æ CH2Cl2 (5)
˚
tance of 2.310(2) A is comparable to that in [Os3(l3-
˚
S)2(CO)8(PMe2Ph)] [2.298(3) A] [12], and overall, the
Os(1)–Os(3)
Os(2)–Os(3)
Os(1)–Os(2)
Os(1)–Se(1)
Os(2)–Se(1)
Os(3)–Se(1)
Os(1)–C(8)
Os(2)–C(8)
Os(3)–C(8)
Os(2)–P(1)
Os(2)–P(2)
2.8917(3)
2.8752(3)
2.8418(3)
2.5140(6)
2.5093(6)
2.5101(6)
2.193(6)
2.154(6)
2.141(6)
2.3528(15)
2.3557(15)
structure is similar to that of this sulfur analogue. Spec-
troscopic data for 2 indicate that it retains its solid-state
structure in solution. As expected the 31P{1H} NMR
spectrum of 2 is a singlet (d 19.1) and the FAB mass spec-
trum contains the molecular ion peak at m/z 1216.
The solid-state molecular structure of [Os3(l3-Se)-
(l3-CO)(CO)7(PPh3)2] (5) (Fig. 2 and Table 3) consists
of three mutually bonded Os atoms with a triply-bridg-
ing CO, seven terminal CO, a triply-bridging Se and two
PPh3 ligands. The Os–Os separations are only slightly
Os(2)–Os(1)–Os(3)
Os(1)–Os(2)–Os(3)
Os(2)–Os(3)–Os(1)
Se(1)–Os(3)–Os(2)
Se(1)–Os(2)–Os(1)
Se(1)–Os(2)–Os(3)
Se(1)–Os(1)–Os(3)
Se(1)–Os(1)–Os(2)
Se(1)–Os(3)–Os(1)
P(2)–Os(3)–Os(1)
P(1)–Os(2)–Os(3)
P(1)–Os(2)–Os(1)
C(8)–Os(1)–Os(3)
C(8)–Os(2)–Os(3)
C(8)–Os(3)–P(2)
C(8)–Os(3)–Se(1)
C(8)–Os(3)–Os(2)
C(8)–Os(1)–Se(1)
C(8)–Os(1)–Os(2)
P(2)–Os(3)–Se(1)
C(8)–Os(2)–Se(1)
P(2)–Os(3)–Os(2)
C(8)–Os(3)–Os(1)
Os(2)–Se(1)–Os(1)
Os(2)–Se(1)–Os(3)
Os(3)–Se(1)–Os(1)
60.188(8)
60.765(8)
68.905(16)
55.041(14)
55.625(15)
55.064(15)
54.797(15)
55.470(15)
54.925(15)
99.32(4)
122.67(4)
111.89(4)
47.40(15)
47.80(15)
133.32(16)
89.19(17)
48.16(16)
87.96(16)
48.58(16)
97.53(4)
different
[Os(1)–Os(2) = 2.8418(3),
Os(2)–Os(3) =
˚
2.8752(3) and Os(1)–Os(3) = 2.8917(3) A]. Each Os
atom has a different co-ordination sphere and the phos-
phine ligands are co-ordinated inequivalently; P(1) is
trans to Se(1) while P(2) is cis to Se(1). The tetrahedral
Os3Se core contains a symmetrically capped Se atom
˚
˚
˚
[Os(1)–Se(1) = 2.5140(6) A, Os(2)–Se(1) = 2.5093(6) A,
Os(3)–Se(1) = 2.5101(6) A]. In contrast, the l3-CO
forms shorter bonds to the more electron-rich Os centers
[Os(1)–C(8) = 2.193(6), Os(2)–C(8) = 2.154(6), Os(3)–
˚
C(8) = 2.141(6) A].
The 31P{1H} NMR spectrum of 5 (CDCl3 solution)
at 223 K shows two equal intensity sharp singlets at
d 14.6 and À7.4, as expected for the molecular structure
found in the crystal. However, at 323 K these signals
have coalesced to a single resonance at d 5.8 as a result
of the interconversion of the two enantiomers 5a and 5b
(Scheme 2). The calculated weighted-average signal
would be at d 3.6. Fig. 3 shows spectra over this temper-
ature range with our best simulations using the program
gNMR (Version 4.1, Cherwell Scientific, 1999) based on
88.94(16)
151.11(4)
48.91(17)
68.905(16)
69.895(17)
70.278(17)
Fig. 2. Solid-state molecular structure of [Os3(l3-Se)(l3-CO)(CO)7(PPh3)2] (5). Thermal ellipsoids are drawn at the 50% probability level.

H. Akter et al. / Journal of Organometallic Chemistry 690 (2005) 4628–4639
4633
Scheme 2.
groups would then not occur synchronously but as sep-
arate processes.
The molecular structure of 6 (Fig. 4 and Table 4)
consists of an open triangular cluster of three Os atoms
with eight terminal CO, two bridging OH and two
PPh3 ligands. The non-bonded Os(1)Á Á ÁOs(2) distance
˚
of 3.1197(2) A is significantly longer than the Os(1)–
Os(3) and Os(2)–Os(3) distances [2.8572(2) and
˚
2.8585(2) A]. The three metal atoms are electron-pre-
cise without the Os(1)–Os(2) bond. Both OH groups
symmetrically span the open Os(1)Á Á ÁOs(2) edge and
the Os-O distances [Os(1)–O(1) = 2.140(2), Os(1)–
O(2) = 2.148(2), Os(2)–O(1) = 2.126(2) and Os(2)–
˚
O(2) = 2.141(2) A] are comparable to the Os-O
distances in other OH-bridged triosmium clusters:
˚
[Os3(l-H)(l-OH)(CO)10] [2.146(7), 2.136(7) A] [14]
[Os3(l-H)(l-OH)(CO)9(PMe2Ph)] [2.135(5), 2.118(5)
˚
A] [15] and [Os3(l-H)(l-OH)(CO)8(l-dppm)] [2.157(8),
˚
2.167(8) A] [16]. We believe that the shortness of the
non-bonded Os(1)Á Á ÁOs(2) edge is attributed to the
presence of two light-atom bridges. A similar shorten-
ing of the open edges has been reported in [Ru3-
˚
(l-OH)2(CO)8(l-BINAP)] [3.023(2) A] [17] and
[Ru3(l-OH)2(CO)8{l-g2-Fe(C5H4PPh2)2}]
[3.0358(8)
˚
A] [18]. The good quality X-ray data allowed us to lo-
cate the hydroxy H-atoms. One is exo and the other
endo with respect to the Os(CO)4 group. Although this
makes the OH bridges inequivalent there is no evidence
for this in positions of the oxygen atoms. The origin of
the hydroxy ligands in 6 may be dioxygen or more
likely water and there are examples of the formation
of OH ligands in triosmium and triruthenium clusters
from water or dioxygen [19–21].
Fig. 3. Observed 31P{1H} NMR spectra (162 MHz) of cluster 5 in
CDCl3 solution and those simulated using the program gNMR.
Spectra are annotated with temperatures and calculated rate
coefficients.
site exchange between the two 31P nuclei. Activation
parameters were determined [DGꢀ = 50.4 0.8 kJ molÀ1
at 298 K; DHꢀ = 51.4 0.9 kJ molÀ1; DSꢀ = 3.2 6.2 J
KÀ1 molÀ1] but these data should be considered with
caution because of the unsymmetrical nature of the coa-
lescing signals was not modelled. Although only one iso-
mer is detected at 223 K, we believe that at higher
temperatures there is a partial population of another
isomer or isomers in equilibrium with the main isomer
found in the crystal leading to distortion.
Scheme 2 is a possible mechanism. A symmetrical
intermediate in the conversion of the enantiomers 5a
to 5b such as that shown may be partially populated
leading to the distortion of the coalescing signals. If this
is correct, turnstile rotations of the two Os(CO)2(PPh3)
In spite of their inequivalence in the solid-state struc-
ture, the OH protons in 6 give a single triplet at d À0.18
(JPH = 3.6 Hz) in the 1H NMR spectrum. The high-field
chemical shift and JPH for the OH protons in 6 are in the
range of values found for other structurally characterized
OH-bridged trimetallic clusters: [Ru3(l-OH)2(CO)8-
(l-BINAP)] [d À1.48, JPH = 4.0 Hz] [17], [Ru3(l-OH)2-
(CO)8{l-g2-Fe(C5H4PPh2)2}] [d À0.68, JPH = 4.0 Hz]
[18], [Os3(l-H)(l-OH)(CO)8(l-dppm)] [d 0.44, JPH
=
4.3 Hz] [16] and [Os3(l-OH)(l-MeOCO)(CO)9(PPh3)]
[d À1.98, JPH = 4.8 Hz] [22]. The 31P{1H} NMR singlet
at d 11.6 indicates that the 31P nuclei are equivalent.
The FAB MS shows the parent ion at m/z 1354 and IR
spectrum contains a broad absorption at 3505 cmÀ1
,
assignable to m(OH).

4634
H. Akter et al. / Journal of Organometallic Chemistry 690 (2005) 4628–4639
Fig. 4. Solid-state molecular structure of [Os3(l-OH)2(CO)8(PPh3)2] (6). Thermal ellipsoids are drawn at the 50% probability level.
The corresponding treatment of [Os3(CO)10(MeCN)2]
with Ph3P@S at room temperature gives five new com-
pounds [Os3(l3-S)2(CO)8(PPh3)] (7), [Os3(l3-Se)(l-
CO)2(CO)7(PPh3)] (8), [Os3(l3-S)(l-CO)(CO)7(PPh3)2]
(9), [Os3(l3-S)2(CO)7(PPh3)2] (11) and 6 in 9%, 29%,
15%, 8% and 5% yields, respectively, in addition to the
known compound 4 in 14% yield (Scheme 1).
Table 4
The solid-state molecular structure of compound 8
(Fig. 5 and Table 5) consists of a closed Os3 triangle with
three CO ligands bonded to each Os atom, a l3-S ligand
˚
Selected bond distances (A) and angles (ꢀ) for [Os3(l-
OH)2(CO)8(PPh3)2] (6)
Os(1)–Os(3)
Os(2)–Os(3)
Os(1)–Os(2)
Os(1)–O(1)
Os(2)–O(1)
Os(1)–O(2)
Os(1)–P(1)
Os(2)–P(2)
Os(2)–O(2)
2.8572(2)
2.8585(2)
3.1197(2)
2.140(2)
2.126(2)
2.148(2)
2.3682(8)
2.3864(8)
2.141(2)
˚
and a PPh3 ligand. The Os(2)–Os(3) bond [2.7531(3) A] is
the shortest while the Os(1)–Os(2) bond trans to PPh3
˚
[2.8214(4) A] is the longest. Two of the three CO ligands
attached to Os(1) are semi-bridged to an adjacent Os cen-
tre with Os(2)Á Á ÁC(11) and Os(3)Á Á ÁC(13) distances of
˚
2.682 and 2.581 A, respectively, and O(13)–C(13)–Os(1)
and O(11)–C(11)–Os(1) angles of 159.8(5)ꢀ and
163.7(4)ꢀ, respectively. The semibridging mode is due to
the sterically congested and electron-rich nature of
Os(1). The l3-sulfido ligand is bonded unsymmetrically
[Os(2)–S(1) = 2.3911(11), Os(1)–S(1) = 2.4283(12) and
Os(2)–O(2)–Os(1)
Os(2)–O(1)–Os(1)
Os(1)–Os(3)–Os(2)
Os(3)–Os(2)–Os(1)
C(12)–Os(1)–P(1)
O(1)–Os(1)–Os(3)
O(2)–Os(1)–P(1)
O(1)–Os(2)–P(2)
O(1)–Os(2)–O(2)
O(1)–Os(1)–P(1)
O(1)–Os(1)–O(2)
C(11)–Os(1)–P(1)
O(2)–Os(1)–Os(3)
P(1)–Os(1)–Os(3)
C(21)–Os(2)–P(2)
C(22)–Os(2)–P(2)
O(2)–Os(2)–Os(3)
O(2)–Os(2)–Os(3)
O(1)–Os(2)–Os(3)
O(2)–Os(1)–Os(3)
O(2)–Os(2)–P(2)
93.34(9)
93.99(10)
66.160(5)
56.901(4)
94.05(11)
81.64(7)
93.46(6)
98.28(7)
73.25(9)
92.67(7)
72.84(9)
91.95(11)
84.92(6)
118.53(2)
94.02(11)
90.70(11)
85.02(6)
85.02(6)
81.83(7)
84.92(6)
93.49(6)
˚
Os(3)–S(1) = 2.4041(12) A] but the average Os-S distance
˚
[2.411(2) A] is comparable to those found for the l3-S li-
˚
gands in [Os3(l3-S)(l3-CO)(CO)7(l-dppm)] [2.393(4) A]
˚
[23], [Os3(l3-S)(l3-CO)(CO)9] [2.378(3) A] [24], [Os4(l3-
˚
S)(CO)12] [2.381(3) A] [25] and [Os3(l3-Se)(l3-CO)-
˚
(CO)7(l-dppm)] [2.5123(14)-2.5302(15) A] [10]. The
PPh3 ligand is coordinated to Os(1) in an equatorial posi-
tion. The 31P{1H} NMR spectrum contains a singlet at d
8.0 and the MS shows the molecular ion at m/z 1118.
By analogy with the formation of [Os6(l3-Se)4(CO)12-
(l-dppm)2] [10] by treatment of [Os3(l3-Se)2(CO)7(l-
dppm)] with Me3NO, and [Ru6(l3-Se)4(CO)12(l-dppm)2]
[5b] by treatment of [Ru3(l3-Se)2(CO)7(l-dppm)] with
Me3NO, it was considered that the reaction of 2 with

H. Akter et al. / Journal of Organometallic Chemistry 690 (2005) 4628–4639
4635
Fig. 5. Solid-state molecular structure of [Os3(l3-S)(l-CO)2(CO)7(PPh3)] (8). Thermal ellipsoids are drawn at the 50% probability level.
Table 5
yields, respectively (Scheme 3). Cluster 12 has been char-
˚
Selected bond distances (A) and angles (ꢀ) for [Os3(l3-S)(l-
CO)2(CO)7(PPh3)] (8)
1
acterized by elemental analysis, infrared, H NMR, 31P
NMR and mass spectra. The singlet at d 5.9 in the 31P
NMR spectrum indicates equivalent 31P nuclei. The
FAB MS shows a molecular ion peak at m/z 2374 corre-
sponding to [Os6(l3-Se)4(CO)14 (PPh3)2]. We propose the
structure for 12 as shown in Scheme 3.
Os(1)–Os(3)
Os(2)–Os(3)
Os(1)–Os(2)
Os(1)–S(1)
Os(2)–S(1)
Os(3)–S(1)
Os(1)–P(1)
Os(1)–C(11)
Os(2)–C(11)
Os(1)–C(13)
Os(3)–C(13)
2,.7948(3)
2.7531(3)
2.8214(4)
2.4283(12)
2.3911(11)
2.4041(12)
2.3727(12)
1.958(5)
Compound 13 is formed by oxidation of CO by
Me3NO to give the corresponding NMe3 derivative.
This reaction is similar to the reported formation of
[FeCo3(l-H)(CO)11(NMe3)] and [FeCo3(l-H)(CO)10-
(PPh2H)(NMe3)] from the reaction of Me3NO with [Fe-
Co3(l-H)(CO)12] and [FeCo3(l-H)(CO)11(PPh2H)],
respectively. We grew X-ray quality crystals of 13 but
were unable to collect diffraction data because these
are unstable. In addition to the usual Ph resonances in
2.682
1.968(5)
2.5816(5)
Os(3)–Os(1)–Os(2)
Os(3)–Os(2)–Os(1)
Os(2)–Os(3)–Os(1)
S (1)–Os(1)–Os(3)
S (1)–Os(2)–Os(3)
S (1)–Os(2)–Os(1)
S(1)–Os(1)–Os(2)
S(1)–Os(3)–Os(1)
S (1)–Os(3)–Os(2)
P(1)–Os(1)–Os(3)
P(1)–Os(1)–Os(2)
P(1)–Os(1)-S (1)
Os(2)–S(1)–Os(3)
Os(3)-S (1)–Os(1)
Os(2)-S (1)–Os(1)
O(11)–C(11)–Os(1)
O(13)–C(13)–Os(1)
58.707(7)
60.164(7)
61.129 (7)
54.26(3)
55.18(3)
54.78(3)
53.56(3)
55.07(3)
54.74(3)
133.03(3)
136.22(3)
96.27(4)
70.08(3)
70.66(3)
71.66(3)
163.7(4)
159.8(5)
1
the H NMR spectrum, a singlet at d 2.80 is assigned
to the NMe3 ligand. The 31P{1H} NMR spectrum shows
a singlet at d 13.77. The FAB MS shows a molecular ion
peak at m/z 1247 corresponding to [Os3(l3-Se)2(CO)7-
(PPh3)(NMe3)].
The reaction of 2 with PPh3 and Me3NO at room
temperature results in substitution of one CO ligand to
produce [Os3(l3-Se)2(CO)7(PPh3)2] (10) (Scheme 4) in
44% yield. Compound 10 can also be obtained from
the reaction of 1 with PPh3 and Me3NO. Single crystals
of 10 for X-ray diffraction were unavailable. The IR
spectrum of 10 in CH2Cl2 is similar to that of [Ru3(l3-
Se)2(CO)7(PPh3)2], obtained from the reaction of
[Ru3(CO)12] and PPh3@Se and characterized by X-ray
diffraction [7a]. The two phosphorus atoms in 10 are
inequivalent, since the 31P{1H} NMR spectrum shows
singlets at d 25.7 and 13.5. The formation of 10 is also
confirmed by its FAB mass spectrum (m/z 1450).
Me3NO might give the corresponding hexanuclear com-
pound [Os6(l3-Se)4(CO)14(PPh3)2] (12). Indeed, treat-
ment of [Os3(l3-Se)2(CO)8(PPh3)] (2) with Me3NO in
toluene at 50 ꢀC gave a dark green hexanuclear cluster
[Os6(l3-Se)4(CO)14(PPh3)2] (12) and a trinuclear cluster
[Os3(l3-Se)2(CO)7(PPh3)(NMe3)] (13) in 46% and 32%

4636
H. Akter et al. / Journal of Organometallic Chemistry 690 (2005) 4628–4639
Os (CO)2(PPh3)
(CO)2
Os
(CO)3
Os
Se
Se
Os
Se
Os
(CO)2
(CO)
Se
3
(CO)3
Os
Os
(PPh3)(CO)2
12
70 O
C
Se
Se
(CO)3
Me3NO + MeCN
Os(CO)2(PPh3)
(CO)3 Os
Os
Se
Se
2
(CO) (PPh )
Os
Os
(MeCN)(CO)2
2
3
13
Scheme 3.
(CO)3
Os
(CO)3
Os
25 O
C
Se
Se
Se
Se
+ PPh3 + Me3NO
Os(CO)2(PPh3)
Os
(PPh3)(CO)2
(CO) (PPh )
Os
(CO)3
Os
2
3
10
2
Scheme 4.
Finally, the treatment of 3 with Se in refluxing tolu-
ene gives compound 2 in 38% yield.
Ph3P@Se [11]. They used identical reaction conditions
and we are unable to account for their different
observations.
In summary, in contrast to the reaction between
PPh3@Se and [Ru3(CO)12], the reaction of [Os3(CO)10-
(MeCN)2] with PPh3@Se gives six products: three (2, 3
and 5) are monosubstituted phosphine derivatives con-
taining capping Se ligands, two are phosphine-only
derivatives (4 and 6) and the unsubstituted capped Se
compound 1 is also formed. Notably [Os3(l3-Se)2-
(CO)7(PPh3)2], the osmium analogue of the open trian-
gular Ru3Se2 nido cluster [Ru3(l3-Se)2(CO)7(PPh3)2]
which was formed in 92% yield, was not detected from
the room temperature reaction between PPh3@Se and
[Os3(CO)10(MeCN)2]. This might be due to the rela-
tively high substitutional lability of the ruthenium
carbonyl clusters compared with that of osmium. As
shown in Scheme 1 the reaction of Ph3P@S with [Os3-
(CO)10(MeCN)2] takes a different course in terms of
the formation of capping sulfido compounds. The
details of the initial reaction are still unresolved but
it is likely that Os-S or Os–Se bonds are formed ini-
tially to give [Os3(CO)10(MeCN)(Ph3PE)] which looses
MeCN to give [Os3(l-EPPh3)(CO)10]. Cleavage of the
P@E bond would lead to free PPh3 and further reac-
tion with PPh3@E would lead to the disulfido and dise-
lenido products. Note that other authors reported the
formation of only 3 and [Os3(CO)11(PPh3)] with
3. Experimental
All reactions and manipulations were carried out
under an atmosphere of purified dinitrogen by using
standard Schlenk techniques. All solvents were dis-
tilled from appropriate drying agents. IR spectra were
recorded on a Shimadzu FTIR 8101 spectrophotome-
ter. NMR spectra were recorded on a Bruker DPX
400 spectrometer. Chemical shifts for the 31P{1H}
NMR spectra are relative to 85% H3PO4. Elemental
analyses were carried out by the Microanalytical Lab-
oratory at University College London. The cluster
[Os3(CO)10(MeCN)2] was prepared according to the
published method [26]. Fast atom bombardment mass
spectra were obtained on a JEOL SX-102 spectrome-
ter using 3-nitrobenzyl alcohol as matrix and CsI as
calibrant.
3.1. Reaction of [Os3(CO)10(MeCN)2] with Ph3P@Se
A dichloromethane solution (50 mL) of [Os3(CO)10-
(MeCN)2] (0.225 g, 0.241 mmol) and Ph3P@Se (0.165

H. Akter et al. / Journal of Organometallic Chemistry 690 (2005) 4628–4639
4637
g, 0.482 mmol) was stirred at room temperature for 48 h.
The solvent was removed under reduced pressure and
the residue dissolved in CH2Cl2 and separated by TLC
on silica. Elution with hexane/CH2Cl2 (10:3 by volume)
produced six bands. The first and fourth bands gave the
known compounds [Os3(l3-Se)2(CO)9] (1) (0.028 g, 12%)
and 1,2-[Os3(CO)10(PPh3)2] (4) (0.023 g, 7%). The third
band gave the recently reported cluster [Os3(l3-Se)(l-
CO)2(CO)7(PPh3)] (3) (0.042 g, 15%) [11] as orange
crystals from hexane/CH2Cl2 at À4 ꢀC (Calc. for
C27H15O9Os3PSe: C, 27.86; H, 1.30. Found: C, 27.99;
H, 1.42%). IR (m(CO), CH2Cl2): 2079s, 2039vs, 2019m,
S)(PPh3)2]
(9)
(0.049
g,
15%)
(Calc.
for
C44H30O8Os3P2S: C, 39.10; H, 2.24. Found: C, 39.25;
H, 2.34%). IR (m(CO), CH2Cl2): 2062s, 2019s, 2001vs,
1958w, 1942w cmÀ1; IR (m(CO), KBr): 1610m cmÀ1
;
31P {1H} NMR (CDCl3): d 9.25 (s); mass spectrum:
m/z 1352. [Os3(l3-S)2(CO)7(PPh3)2] (11) (0.025 g, 8%).
(Calc. for C43H30O7Os3P2S2: C, 38.1; H, 2.23. Found:
C, 38.26; H, 2.38%). IR (m(CO), CH2Cl2): 2046vs,
2014vs, 2004vs, 1965vs, 1934s cmÀ1 31P{1H} NMR
;
(CDCl3): d 25.62(s), 12.95(s); mass spectrum: m/z
1356. [Os3(l-OH)2(CO)8(PPh3)2] (6) (0.019 g, 5%).
1990s(br) and 1900br (KBr) cmÀ1
;
31P{1H} NMR
3.3. Thermolysis of compound 2 in the presence of
trimethylamine-N-oxide
(CDCl3): d 8.1 (s); mass spectrum: m/z 1164. The second
band gave [Os3(l3-Se)2(CO)8(PPh3)] (2) (0.033 g, 10%)
as yellow crystals after recrystallization from hexane/
CH2Cl2 at À4 ꢀC (Calc. for C26H15O8Os3PSe2: C,
25.70; H, 1.25. Found: C, 25.95; H, 1.35%). IR
(m(CO), CH2Cl2): 2079s, 2046vs, 2015s, 2000s, 1956w
On heating solution of 2 (0.015 g, 0.012 mmol) and
Me3NO Æ 2H2O (0.003 g, 0.039 mmol) in toluene (20
mL) at 50 ꢀC for 1 h, the color changed from yellow
to green. The solvent was pumped off and the residue
chromatographed by TLC on silica. Elution with hex-
ane/CH2Cl2 (2:1 by volume) gave three bands. The fas-
ter moving band (Rf = 0.82) gave the unreacted starting
material 2 (0.002 g). Second band (Rf = 0.61) afforded
[Os6(l3-Se)4(CO)14(PPh3)2] (12) (0.007 g, 46%) (Calc.
for C50H30O14Os6P2Se4: C, 25.30; H, 1.27. Found: C,
26.12; H, 1.45%). IR (m(CO), CH2Cl2): 2066vs, 2023s,
2008s, 1961m, 1923w, 1907w cmÀ1; 1H NMR (CD2Cl2):
d 7.64(m), 31P{1H} NMR (CD2Cl2): d 25.9 (s); mass
spectrum: m/z 2374. The slower moving band
(Rf = 0.46) gave [Os3(l3-Se)2(CO)7(PPh3)(NMe3)] (13)
(0.005 g, 32%) (Calc. for C28H24O7Os3PSe2N: C,
26.99; H, 1.94; N, 1.13. Found: C, 27.25; H, 2.15; N,
1.34%). IR (m(CO), CH2Cl2): 2044s, 1996vs, 1976sh,
cmÀ1 31P{1H} NMR (CDCl3): d 19.1(s); mass spectrum:
;
m/z 1216. The fifth band gave [Os3(l3-Se)(CO)7(l3-
CO)(PPh3)2] Æ CH2Cl2 (5) (0.057 g, 16%) as yellow crys-
tals from hexane/CH2Cl2 at À4 ꢀC (Calc. for
C45Cl2H32O8Os3P2Se: C, 36.44; H, 2.18. Found: C,
36.65; H, 2.29%). IR (m(CO), CH2Cl2): 2064s, 2019s,
2002vs, 1959w, 1942w cmÀ1plus 1610m (KBr) cmÀ1
;
1H NMR (CDCl3): d 7.38 (m, 30H), 5.32 (s, 2H,
CH2Cl2); 31P{1H} NMR (À50 ꢀC, CDCl3): d 14.6(s),
7.4(s); mass spectrum: m/z 1398. The slowest moving
band gave [Os3(l-OH)2(CO)8(PPh3)2] (6) (0.024 g, 7%,)
as pale yellow crystals after recrystallization from hex-
ane/CH2Cl2 at À4 ꢀC (Calc. for C44H32O10Os3P2: C,
39.05; H, 2.39. Found C, 39.14; H, 2.48%). IR (m(CO),
CH2Cl2): 2062s, 2002vs, 1983s, 1961w, 1923m plus
1954m, 1886vw cmÀ1 1H NMR (CD2Cl2): 7.58(m),
;
3505br (KBr) cmÀ1
;
1H NMR (CDCl3): d 7.25 (m,
7.45(m), 2.80(s); d 31P{1H} NMR (CD2Cl2): d 13.77
(s); mass spectrum: m/z 1247.
30H), À0.18 (t, 2H, J = 3.6 Hz); 31P{1H} NMR
(CDCl3): d 11.6 (s); mass spectrum: m/z 1354.
3.4. Reaction of cluster 2 with PPh3
3.2. Reaction of [Os3(CO)10(MeCN)2] with Ph3P@S
Me3NO Æ 2H2O (0.003 g, 0.040 mmol) was added to
a CH2Cl2 solution (25 mL) of 2 (0.023 g, 0.019 mmol)
and PPh3 (0.010 g, 0.038 mmol) and the reaction
mixture was stirred at room temperature for 2 h. The
solution was filtered through a short silica column (4
cm) to remove the excess of Me3NO. The solvent
was removed at reduced pressure and the residue chro-
matographed by TLC on silica. Elution with hexane/
CH2Cl2(3:2 by volume) gave two bands. The first gave
unconsumed 2 (0.003 g) while the second band gave
[Os3(l3-Se)2(CO)7(PPh3)2] (10) (0.012 g, 44%) as orange
crystals after recrystallyzation from hexane/CH2Cl2
(Calc. for C43H30O7Os3P2Se2: C, 35.64; H, 2.09.
Found: C, 35.78; H, 2.24%). IR (m(CO), CH2Cl2):
A similar reaction to that above of [Os3(CO)10-
(MeCN)2] (0.225 g, 0.241 mmol) and Ph3P@S (0.142 g,
0.483 mmol) in CH2Cl2 (50 mL) for 48 h at room tem-
perature followed by similar TLC separation produced
six bands which gave the following compounds in order
of elution: [Os3(l3-S)2(CO)8(PPh3)] (7) (0.024 g, 9%)
(Calc. for C26H15O8Os3PS2: C, 27.85; H, 1.35. Found:
C, 28.05; H, 1.42%). IR (m(CO), CH2Cl2): 2079s,
2045vs, 2015s, 2000s,1956m cmÀ1
;
31P{1H} NMR
(CDCl3): d 19.15(s); mass spectrum: m/z 1122. [Os3(l3-
S)(l-CO)2(CO)7(PPh3)] (8) (0.078 g, 29%) as (Calcd.
for C27H15O9Os3PS: C, 29.03; H, 1.35. Found: C,
30.15; H, 1.52%). IR (m(CO), CH2Cl2): 2079s, 2040vs,
2023m, 1990s(br), 1902w, 1886w cmÀ1
;
31P{1H} NMR
2046vs, 2014s, 2000m, 1965m, 1934s cmÀ1 31P{1H}
;
(CDCl3): d 8.02 (s); mass spectrum: m/z 1118. [Os3-
(CO)10(PPh3)2] (4) (14%). [Os3(CO)7(l3-CO)(l3-
NMR (CDCl3): d 25.7 (s), 13.5 (s); mass spectrum:
m/z 1450.

4638
H. Akter et al. / Journal of Organometallic Chemistry 690 (2005) 4628–4639
3.5. Reaction of cluster 1 with PPh3
Appendix A. Supplementary material
Me3NO Æ 2H2O (0.005 g, 0.067 mmol) was added to a
dichloromethane solution (25 mL) of 1 (0.027 g, 0.028
mmol) and PPh3 (0.015 g, 0.057 mmol) (0.005 g, 0.067
mmol). The solution was stirred at room temperature
for 3 h, filtered through a short silica column and the
solvent was removed under reduced pressure. Chroma-
tography of the residue by TLC on silica gel, eluting
with hexane/CH2Cl2 gave a single band which afforded
compound 2 (0.010 g, 30%).
The crystal data, details of data collection and refine-
ment results are summarised in Table 1. Crystallo-
graphic data have been deposited with the Cambridge
Crystallographic Data Centre, CCDC Nos 273681 for
2, 241278 for 5, 273682 for 6, and 273683 for 8. Copies
of this information may be obtained free of charge from
the Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (fax: +44 1223 336033; e-mail: deposit@ccdc.
cam.ac.uk or www: http://www.ccdc.cam.ac.uk). Sup-
plementary data associated with this article can be
found, in the online version, at doi:10.1016/
j.jorganchem.2005.07.038.
3.6. Reaction of 3 with elemental selenium
A mixture of 3 (0.020 g, 0.018 mmol) and black sele-
nium (0.040 g, 0.037 mmol) in toluene (25 mL) was
heated to reflux for 2 h. The solvent was removed under
reduced pressure and the residue chromatographed by
TLC on silica. Elution with hexane/CH2Cl2 (10:3 by vol-
ume) gave a single band which afforded 2 (0.008 g, 38%).
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