Oxidative addition of silanes R3SiH to the unsaturated cluster [Os3(μ-H){μ3-Ph2PCH2PPh(C 6H4)}(CO)8]: Evidence for reversible silane formation in the dynamic behaviour of [Os3(μ-H)-(SiR 3)(CO)9(μ-dppm)]

Article abstract of DOI:10.1039/b411833b

Oxidative addition of the silanes R₃SiH (R₃ = Ph ₃, Et₃, EtMe₂) to the unsaturated cluster [Os₃(μ-H){μ₃-Ph₂PCH₂PPh(C ₆H₄)}(CO)₈] leads to the saturated clusters [Os₃(μ-H)(SiR₃)(CO)₉(μ-dppm)] (SiR ₃ = SiPh₃ 1, SiEt₃ 2 and SiEtMe₂ 3) and the unsaturated clusters [Os₃(μ-H)₂(SiR ₃){μ₃-Ph₂PCH₂PPh(C ₆H₄)}(CO)₇] (SiR₃ = SiPh₃ 4, SiEt₃ 5 and SiEtMe₂ 6). Structures are based on spectroscopic evidence and a XRD structure of [Os₃(μ-H)(SiPh ₃)(CO)₉(μ-dppm)] 1 in which all non-CO ligands are coordinated equatorially and the hydride and the silyl groups are mutually cis. From variable-temperature ¹H NMR spectra of the SiEt₃ compound 2, exchange of the P nuclei is clearly apparent. Simultaneous migrations of the SiEt₃ group and of the hydride from one Os-Os edge to another generate a time-averaged mirror plane in the molecule. VT ¹H NMR spectra of the somewhat less bulky compound [Os ₃(μ-H)(SiMe₂Et)(CO)₉(μ-dppm)] 3 have been analysed. Two isomers 3a and 3b are observed with the hydride ligand located on different Os-Os edges. Synchronous migration of the hydride and SiMe ₂Et groups is faster than the observed interconversion of isomers which occurs by hydride migration alone. The synchronous motion of H and SiR₃ only occurs when these ligands are mutually cis as in the major isomer 3a and we propose that this process requires the formation of a transient silane complex of the type [Os₃(η²-HSiR ₃)(CO)₉(μ-dppm)]. Turnstile rotation within an Os(CO)₃(η²-HSiR₃) group leads to the observed exchange within the major isomer 3a without exchange with the minor isomer. This process is not observed for the minor isomer 3b because the hydride and the silyl group are mutually trans. Protonation to give [Os ₃(μ-H)₂(SiR₃)(CO)₉(μ-dppm)] ⁺ totally suppresses the dynamic behaviour because there are no edge vacancies.

Full text of DOI:10.1039/b411833b

View Article Online / Journal Homepage / Table of Contents for this issue
F U L L P A P E R
Oxidative addition of silanes R3SiH to the unsaturated cluster
[Os3(l-H){l3-Ph2PCH2PPh(C6H4)}(CO)8]: Evidence for
reversible silane formation in the dynamic behaviour of [Os3(l-H)-
(SiR3)(CO)9(l-dppm)]
Antony J. Deeming,*a Md. Manjur Hassan,b Shariff E. Kabir,*b Ebbe Nordlanderc and
Derek A. Tochera
a
Department of Chemistry, University College London, 20 Gordon Street, London,
UK WC1H 0AJ. E-mail: a.j.deeming@ucl.ac.uk
Department of Chemistry, Jahangirnagar University, Savar, Dhaka 1342, Bangladesh
Inorganic Chemistry, Center for Chemistry and Chemical Engineering, Lund University,
b
c
Box 124 SE-22100, Lund, Sweden
Received 2nd August 2004, Accepted 26th August 2004
First published as an Advance Article on the web 7th October 2004
Oxidative addition of the silanes R3SiH (R3 = Ph3, Et3, EtMe2) to the unsaturated cluster [Os3(l-H){l3-
Ph2PCH2PPh(C6H4)}(CO)8] leads to the saturated clusters [Os3(l-H)(SiR3)(CO)9(l-dppm)] (SiR3 = SiPh3 1, SiEt3 2
and SiEtMe2 3) and the unsaturated clusters [Os3(l-H)2(SiR3){l3-Ph2PCH2PPh(C6H4)}(CO)7] (SiR3 = SiPh3 4, SiEt3
5 and SiEtMe2 6). Structures are based on spectroscopic evidence and a XRD structure of [Os3(l-H)(SiPh3)(CO)9(l-
dppm)] 1 in which all non-CO ligands are coordinated equatorially and the hydride and the silyl groups are
mutually cis. From variable-temperature 1H NMR spectra of the SiEt3 compound 2, exchange of the P nuclei is
clearly apparent. Simultaneous migrations of the SiEt3 group and of the hydride from one Os–Os edge to another
generate a time-averaged mirror plane in the molecule. VT 1H NMR spectra of the somewhat less bulky compound
[Os3(l-H)(SiMe2Et)(CO)9(l-dppm)] 3 have been analysed. Two isomers 3a and 3b are observed with the hydride
ligand located on different Os–Os edges. Synchronous migration of the hydride and SiMe2Et groups is faster than
the observed interconversion of isomers which occurs by hydride migration alone. The synchronous motion of H
and SiR3 only occurs when these ligands are mutually cis as in the major isomer 3a and we propose that this process
requires the formation of a transient silane complex of the type [Os3(g2-HSiR3)(CO)9(l-dppm)]. Turnstile rotation
within an Os(CO)3(g2-HSiR3) group leads to the observed exchange within the major isomer 3a without exchange
with the minor isomer. This process is not observed for the minor isomer 3b because the hydride and the silyl group
are mutually trans. Protonation to give [Os3(l-H)2(SiR3)(CO)9(l-dppm)]+ totally suppresses the dynamic behaviour
because there are no edge vacancies.
Introduction
Results and discussion
Complexes and clusters of transition metals containing M–Si
bonds have been intensively studied in recent years because of
theoretical challenges and applications (see, for example, ref. 1).
The main entry into this chemistry is by the facile oxidative
addition of silanes to unsaturated transition metal clusters
which commonly generates clusters with bridging hydride and
terminal silyl groups.2 Agostic M–H–Si interactions are impor-
tant in several clusters2 and have been implicated in catalytic
processes such as hydrosilation.3–5 Since agostic bonds are read-
ily formed, they have been studied as analogues of the agostic
M–H–C bonds and C–H bond activation. In some cases agostic
M–H–Si bonds have been found in ground-state structures and
have been characterised by XRD.2 In other cases they appear as
intermediates in reactions.6
Synthesis and characterisation of oxidative addition products
Treatment of the unsaturated cluster [Os3(l-H){l3-
Ph2PCH2PPh(C6H4)}(CO)8] with a trisubstituted silane R3SiH
(R3 = Ph3, Et3, EtMe2) in refluxing toluene for 8 to 10 hours
leads to a mixture which can be separated chromatographically
into the saturated product [Os3(l-H)(SiR3)(CO)9(l-dppm)]
(R = SiPh3 1, SiEt3 2 and SiEtMe2 3) and the unsaturated [Os3(l-
H)2(SiR3){l3-Ph2PCH2PPh(C6H4)}(CO)7] (R = SiPh3 4, SiEt3 5
and SiEtMe2 6) (Scheme 1) in similar yields. The Ph groups are
omitted from dppm in this and following schemes.
Examples of the oxidative addition of silanes to triosmium
clusters are the addition of (EtO)3SiH to [Os3(CO)10(MeCN)2]7,8
and of Et3SiH (and related Ge and Sn compounds) or Ph2SiH2
to [Os3(l-H)2(CO)10].6,9 Other examples of silyl osmium clus-
ters10,11 and silyl ruthenium clusters have been reported.12,13
In this paper we will describe examples of the oxidative
addition of silanes R3SiH to an unsaturated triosmium cluster
[Os3(l-H){l3-Ph2PCH2PPh(C6H4)}(CO)8]14 and present an
analysis of dynamic behaviour of one of the products which
is of the type [Os3(l-H)(SiR3)(CO)9(l-dppm)]. Evidence is
presented for the transient existence of an agostically bonded
complex [Os3(HSiR3)(CO)9(l-dppm)] in the dynamic behaviour
of one isomer of the cluster [Os3(l-H)(SiMe2Et)(CO)9(l-
dppm)].
Scheme 1
These products have been characterised by the usual spectro-
scopic methods (see Experimental) and the structures confirmed
by X-ray diffraction on the compounds 1 and 4. We report the
structure of 1 in this paper because it is relevant to the dynamic
behaviour of compounds 1 to 3 which is the subject of this
paper. The structure of 4 will be reported in a following paper
T h i s j o u r n a l i s
©
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 4
D a l t o n T r a n s . , 2 0 0 4 , 3 7 0 9 – 3 7 1 4
3 7 0 9

View Article Online
Table 1 Selected bond lengths (Å) and angles (°) for the cluster [Os3(l-
H)(SiPh3)(CO)9(l-dppm)] 1
ence the Os(1)–Os(2)–P(2) angle of 89.19(2)° is smaller than
the Os(2)–Os(1)–P(1) angle of 93.27(2)°. Fig. 2 shows how the
hydride location has a larger impact on the whole cluster, than
its size alone would imply. This has consequences in considering
the dynamic behaviour of the cluster (see below).
Os(1)–Os(2)
Os(2)–Os(3)
Os(3)–Os(1)
Os(1)–P(1)
Os(2)–P(2)
Os(3)–Si(1)
Si(1)–C(65)
Si(1)–C(71)
Si(1)–C(77)
2.9008(3)
3.0220(2)
2.8711(3)
2.3129(9)
2.3517(9)
2.4503(9)
1.892(4)
1.902(4)
1.910(4)
Os(1)–C(11)
Os(1)–C(12)
Os(1)–C(13)
Os(2)–C(21)
Os(2)–C(22)
Os(2)–C(23)
Os(3)–C(31)
Os(3)–C(32)
Os(3)–C(33)
1.932(4)
1.891(4)
1.925(4)
1.949(4)
1.898(4)
1.935(4)
1.928(4)
1.875(4)
1.946(4)
Os(1)–Os(2)–P(1)
Os(2)–Os(1)–P(2)
Os(3)–Os(2)–P(2)
Os(3)–Os(1)–P(1)
Os(2)–Os(3)–Si(1)
89.19(2)
93.27(2)
146.50(2)
152.49(2)
116.46(2)
Os(1)–Os(3)–Si(1)
Os(2)–Os(3)–C(32)
Si(1)–Os(3)–C(32)
Os(1)–Os(3)–C(32)
174.22(2)
146.34(12)
97.20(12)
87.49(12)
which will describe the structures and full range of reactivities
of compounds 1 to 6 and related compounds. Interestingly the
compound [Os3(l-H){Si(OMe)3}(CO)10(dppm-P)] has been
reported to be formed from the treatment of [Os3(l-H){Si-
(OMe)3}(CO)10(MeCN)] with dppm.8 The monodentate nature
of dppm was established spectroscopically but loss of CO to give
[Os3(l-H){Si(OMe)3}(CO)9(l-dppm)] analogous to compounds
1 to 3 was not reported. We believe that compounds of the type
1 to 3 are reported here for the first time.
Fig. 2 Structure of the cluster [Os3(l-H)(SiPh3)(CO)9(l-dppm)]
showing the effect of the bridging hydride on the positions of the other
equatorial ligands.
Dynamic behaviour of the cluster [Os3(l-H)(SiEt3)(CO)9(l-
dppm)] 2
Crystal structure of the cluster [Os3(l-H)(SiPh3)(CO)9(l-
dppm)] 1
1
The limiting low temperature and high temperature H NMR
The molecular structure of compound 1 is shown in Fig. 1 and
selected bond lengths and angles are in Table 1. Each Os atom
has two equatorial and two axial ligands as in [Os3(CO)12] and
its simple substitution derivatives. Also the smaller (CO) ligands
are positioned axially with longer Os–CO distances than those
that are coordinated equatorially because of unfavourable com-
petition of mutually trans CO for p-electron density.
spectra in the hydride region are a double doublet and a 1:2:1
triplet respectively. The limiting spectra are not fully achieved in
Fig. 3 since higher and lower temperatures would be needed. The
oberved spectra can be well modelled by gNMR15 for a process
which exchanges the P nuclei of the dppm ligand. It is reason-
able to assume that it is the H, SiEt3 and CO ligands that are in
Fig. 1 Molecular structure of the cluster [Os3(l-H)(SiPh3)(CO)9(l-
dppm)] (ORTEP plot with 30% thermal ellipsoids).
As expected the bulky SiPh3 group is equatorially coordinated.
The position of the hydride ligand was clearly established and
refined in the X-ray analysis but various geometric features are
totally consistent with its position as shown in Fig. 1. The hydride
bridges the longest Os–Os edge [Os(2)–Os(3) 3.0220(2) Å] and
significantly the SiPh3 is cis to the hydride in the sterically least
crowded equatorial site. The coordination geometries of the Os
atoms are closely octahedral with the hydride occupying one
of the octahedral sites at each of Os(2) and Os(3). As a conse-
quence there is more crowding on the Os(1)–Os(3) edge than the
Os(2)–Os(3) edge. For example, the Os(3)–Os(2)–C(22) angle
is 115.29(11)° whereas the corresponding angle at the other
edge, Os(3)–Os(1)–C(12) is 107.46(12)°. Related to this differ-
Fig. 3 Observed and computed (using gNMR15) 1H NMR spectra
for cluster [Os3(l-H)(SiEt3)(CO)9(l-dppm)] measured in CDCl3 at
500 MHz.
3 7 1 0
D a l t o n T r a n s . , 2 0 0 4 , 3 7 0 9 – 3 7 1 4

View Article Online
motion rather than the dppm ligand. In the crystal structure of
the SiPh3 complex (Fig. 1) the dppm-bridge is non-planar and
there are two axial and two equatorial Ph groups. Inversion of
the dppm ligand is very rapid because the CH2 group gives a
1:2:1 triplet at all temperatures. For the purposes of this dis-
cussion we can therefore consider the OsPCPOs set of atoms
associated with the dppm bridge to be planar. Scheme 2 shows
that hydride migration and motion of the Os(SiEt3)(CO)3 group
are necessary to give PA–PB exchange which is a moderately
complex process with the following activation parameters: DG‡
(298 K) = (63.9 ± 2.3) kJ mol−1, DH‡ = (70.2 ± 2.3) kJ mol−1,
DS‡ = (21.2 ± 7.7) J K−1 mol−1.
Scheme 2
If the motion of the hydride occurs as a separate process
from the motion of the Os(SiEt3)(CO)3 group we would expect
another isomer with the hydride trans to SiEt3 to be involved in
the exchange.
Dynamic behaviour of the cluster [Os3(l-H)(SiMe2Et)(CO)9(l-
dppm)] 3
There are significant differences between the solution behaviour
of the SiEt3 and the SiMe2Et clusters, most notable the pres-
ence of a second minor isomer 3b in dynamic equilibrium with
the major isomer of [Os3(l-H)(SiMe2Et)(CO)9(l-dppm)] 3a.
1
Fig. 4 shows the variation in hydride H NMR spectra with
temperature. Species 3a gives a low-temperature double doublet
at d −18.75 [JPH = 24.0 and 5.0 Hz] which corresponds to that at
d −18.90 for the compound [Os3(l-H)(SiEt3)(CO)9(l-dppm)]. In
addition there is a smaller double doublet at d −17.75 [JPH = 26.5
and 4.5 Hz] with essentially the same two coupling constants to
31P as 3a. The hydride and the dppm ligand must be similarly dis-
posed with respect to each other in both isomers. The isomer 3a
corresponds to that in the crystal of [Os3(l-H)(SiPh3)(CO)9(l-
dppm)] 1 and in solution for [Os3(l-H)(SiEt3)(CO)9(l-dppm)] 2.
Since 3a is in exchange with 3b, the two isomers must be closely
related. Isomer 3b cannot have an axially coordinated SiPh3
since the CH2 (dppm) 1H NMR signals appear as 1:2:1 triplets
for both 3a and 3b indicating that both have a plane of symmetry
through the Os3 plane. We therefore propose that isomer 3b is as
shown in Scheme 3 with a mutually trans arrangement of the
hydride and silyl group.
Fig. 4 Observed 1H NMR spectra in the hydride region for the cluster
[Os3(l-H)(SiMe2Et)(CO)9(l-dppm)] measured in CDCl3 at 500 MHz.
The signal for major isomer 3a is on the right and for the minor isomer
3b on the left.
Isomer 3a follows the same pattern of exchange as [Os3(l-
H)(SiEt3)(CO)9(l-dppm)] with exchange of the two P nuclei
but this occurs by a process independent of isomer 3b. Over the
temperature range 258 to 298 K there is no evidence for a similar
exchange for isomer 3b. The first indication of dynamic behav-
iour for 3b is an exchange between 3a and 3b.
Simulation of the NMR spectra of compound 3 by an
intraisomer process A for 3a (rate coefficient ka, see Scheme 3)
and a slower 3a–3b isomerisation B (rate coefficient kb) leads
to the spectra in Fig. 5. Good matches of observed and
experimental spectra are obtained with the rate coefficients
given in the figure. The intraisomer process A is about 15
times faster than isomer interconversion B. Therefore isomer
3b cannot be an intermediate in process A for 3a. The intra-
isomer process C shown in Scheme 3 is too slow to be detected.
An independent measure of the rate of 3a–3b isomerisation
was obtained by analysis of the line-shapes of the coalescing
dppm methylene triplets for the two isomers. The rate data are
Scheme 3
presented together as the Eyring plots shown in Fig. 6. From
these the activation parameters were obtained: process A, DG‡
(298 K) = (63.7 ± 2.3) kJ mol−1, DH‡ = (62.7 ± 2.3) kJ mol−1,
DS‡ = (−3.3 ± 7.1) J K−1 mol−1 while those for process B are DG‡
(298 K) = (70.5 ± 2.6) kJ mol−1, DH‡ = (62.0 ± 2.6) kJ mol−1,
DS‡ = (−28.5 ± 10.0) J K−1 mol−1.
D a l t o n T r a n s . , 2 0 0 4 , 3 7 0 9 – 3 7 1 4
3 7 1 1

View Article Online
Mechanisms of the dynamic behaviour for isomers 3a
Neither hydride migration or turnstile rotation at the
Os(CO)3(SiMe2Et) group in 3a are sufficient to account for
process A. A combination of the two are necessary to account
for the exchange shown in Scheme 2 and furthermore these must
occur without the intermediacy of isomer 3b. Also we believe it
is fundamental to process A that the hydride and SiMe2Et group
are mutually cis. We propose that the cis arrangement allows
the reductive elimination of the silane which remains agosti-
cally bonded. A turnstile process at the resultant Os(CO)3(g2-
HSiMe2Et) group as in Scheme 4 followed by an oxidative
addition regenerate isomer 3a with exchange of the P-nuclei
of the dppm ligand. This explains why there is no analogous
process when the H and SiMe2Et ligands are trans as in isomer
3b because reductive elimination is not possible in that case.
There are examples of agostic bonding in compounds such as
[Ru2(l-g2-SiTol2H)(SiTol2H)(CO)5(l-dppm)] which contain the
fragment shown in Fig. 7. Such a unit might possibly be on the
reaction path of the process shown in Scheme 4.
Scheme 4
Fig. 5 gNMR15 simulated 1H NMR spectra in the hydride region for
the cluster [Os3(l-H)(SiMe2Et)(CO)9(l-dppm)] 3a and 3b, where ka is for
the faster process (P–P exchange) and kb for the slower process (intercon-
version of isomer 3a with 3b). The signal for major isomer 3a is on the
right and for the minor isomer 3b on left.
Fig. 7 Agostically bonded silyl unit found in metal–metal bonded
systems.
Treatment of cluster 3 with CO at atmospheric pressure dis-
places Me2EtSiH and forms the cluster [Os3(CO)10(dppm)]. This
provides circumstantial evidence that the reductive elimination
is facile.
Protonation of cluster 1
Treatment of a CD2Cl2 solution of the cluster [Os3(l-H)-
(SiPh3)(CO)9(l-dppm)] 1 with HBF4·Et2O leads to the formation
of a non-fluxional cationic dihydride [Os3(l-H)2(SiPh3)(CO)9(l-
dppm)][BF4] 7.
1
The H NMR spectrum of 7 shows two closely positioned
hydride signals at d −17.49 (JPH = 16.8, 1.8 Hz and JHH
=
1.8 Hz) and d −17.57 (JPH = 12.0, 1.0 Hz and JHH = 1.8 Hz).
Each signal appears as a doublet of triplets, but these are
more correctly analysed (gNMR15) as double double doublets.
Since the hydrides are different and not exchanging, as
expected, there are also two corresponding 31P{1H} NMR
signals appearing as two AB doublets at d −35.80 and −35.21
(JPP = 18.0 Hz). A structure consistent with these data is shown
in Scheme 5. Significantly the cluster is not dynamic at the same
Fig. 6 Plots of ln(ka/T) against 1/T (points ) and of ln(kb/T) against
1/T (points D and ) for the two processes A and B occurring for isomers
3a and 3b of the cluster [Os3(l-H)(SiMe2Et)(CO)9(l-dppm)]. Points D
are from the coalescence of the CH2 NMR triplets and  and  from
changes in the hydride signals with temperature.
3 7 1 2
D a l t o n T r a n s . , 2 0 0 4 , 3 7 0 9 – 3 7 1 4

View Article Online
gave [Os3(l-H)2(SiMe2Et){l3-Ph2PCH2PPh(C6H4)}(CO)7]
6
(0.058 g, 54%) as yellow crystals from a hexane–CH2Cl2 mix-
ture at 0 °C. Anal. for 6: calc. for C36H34O7Os3P2Si, C, 34.89;
H, 2.77. Found: C, 34.98; H, 2.86%; IR [m(CO), CH2Cl2]:
2065s, 2012s, 1998vs, 1989s, 1940s cm−1 and the cluster
[Os3(l-H)(SiMe2Et)(CO)9(dppm)] 3 (0.036 g, 32%) as orange
crystals from a hexane–CH2Cl2 mixture at 0 °C. Anal. for 3:
calc. for C38H34O9Os3P2Si, C, 35.23; H, 2.65. Found: C, 35.38;
H, 2.78%; IR [m(CO), CH2Cl2]: 2082w, 2042s, 2000vs, 1968m,
1958m cm−1.
Scheme 5
Crystal structure determination for compound 1
temperatures as the neutral precursor and this is likely to be
because there are no edge vacancies to allow the migration of
hydride ligands.
All geometric and intensity data were obtained for a red
single crystal of compound 1 on a Bruker SMART APEX
CCD diffractometer using Mo-Ka radiation (k = 0.71073 Å)
at 150 ± 2 K. Data reduction and integration was carried out
with SAINT+ and absorption corrections were applied using
the programme SADABS.16 Structures were solved by direct
methods and developed using alternating cycles of least-squares
refinement and difference-Fourier synthesis. All non-hydrogen
atoms were refined anisotropically. Hydrogen atoms, except
that bonded to Os, were placed in calculated positions and their
thermal parameters linked to those of the atoms to which they
were attached (riding model). The hydrogen atom bridging Os
atoms was located and its position refined using fixed isotropic
thermal parameters. There is an indication of disorder of one
phenyl ring, C(47)–C(52), but this was not included in the
model. The SHELXTL PLUS V6.10 program package was used
for structure solution and refinement.17
Experimental
The cluster [Os3(l-H){l3-Ph2PCH2PPh(C6H4)}(CO)8] was
synthesised by a reported method14 and the silanes Ph3SiH,
Et3SiH and Me2EtSiH were obtained from Aldrich plc and used
as supplied.
Reaction of the cluster [Os3(l-H){l3-Ph2PCH2PPh(C6H4)}-
(CO)8] with triphenylsilane
A benzene solution (60 cm3) of the cluster [Os3(l-H){l3-
Ph2PCH2PPh(C6H4)}(CO)8] (0.165 g, 0.140 mmol) and Ph3SiH
(0.182 g, 0.699 mmol) was heated to reflux for 8 h during which
time the colour changed from green to orange. The solvent was
removed under reduced pressure and the residue chromato-
graphed by TLC on silica. Elution with hexane–dichloro-
methane (2:2 by volume) gave two bands. The faster moving
band gave [Os3(l-H)2(SiPh3){l3-Ph2PCH2PPh(C6H4)}(CO)7] 4
(0.099 g, 50%) as yellow crystals from a hexane–CH2Cl2 mixture
at 4 °C. Anal. for 4: calc. for C50H38O7Os3P2Si, C, 42.54; H, 2.72.
Found: C, 42.64; H, 2.78%; IR [m(CO), CH2Cl2]: 2070vs, 2020s,
2004s, 1993s, 1950m cm−1; 1H NMR (CD2Cl2): d 7.82–6.68
(m, 30H), 6.96 (m, 1H), 6.63 (m, 1H), 6.21 (m, 1H), 6.46 (t,
1H), 4.81 (m, 1H), 3.76 (m, 1H), −12.43 (dd, 1H, J = 36.0,
8.8 Hz), −15.05 (d, 1H, J = 10.8 Hz); 31P{1H} NMR (CD2Cl2):
d −14.7 (d, J = 62.6 Hz), −22.2 (d, J = 62.6 Hz). The slower
band gave the cluster [Os3H(SiPh3)(CO)9(dppm)] 1 (0.092 g,
45%) as orange crystals from a hexane–CH2Cl2 mixture at 4 °C.
Anal. for 1: calc. for C52H38O9Os3P2Si, C, 42.56; H, 2.62. Found:
C, 42.69; H, 2.72%; IR [m(CO), CH2Cl2]: 2087m, 2049s, 2004vs,
1977m cm−1; 1H NMR (CD2Cl2): d 7.60–7.18 (m, 35H), 5.25 (t,
2H, J = 10.8 Hz), −18.32 (apparent d similar to the spectrum
at 298 K in Fig. 3, 1H, J = 30.4 Hz); 31P{1H} NMR (CD2Cl2):
d −30.2 (d, J = 46.5 Hz), −41.8 (d, J = 46.5 Hz).
Crystal data. C52H38O9Os3P2Si, M = 1467.45, monoclinic,
a = 19.3866(16), b = 10.2591(8), c = 24.713(2) Å, b =
102.8060(10)°, U = 4793.0(7) Å3, T = 150 K, space group P21/c,
Z = 4, l(Mo-Ka) = 8.082 mm−1, 41583 reflections measured,
11406 unique (Rint = 0.0280) which were used in all calculations.
The final R1 = 0.0269 and wR2 = 0.0555 (all data).
CCDC reference number 246431.
See http://www.rsc.org/suppdata/dt/b4/b411833b/ for crystal-
lographic data in CIF or other electronic format.
Acknowledgements
A. J. D. thanks the Wenner-Gren Foundation (Stockholm) for a
fellowship to work at Lund University and Dr Ebbe Nordlander
for being his host. The Royal Society (London) and the Swedish
Academy of Sciences are also thanked for supporting the
collaboration between A. J. D., E. N. and S. E. K. acknowledges
support from the Royal Society (London), the Swedish
International Development Agency and the Swedish Science
Research Council.
Reaction of the cluster [Os3(l-H){l3-Ph2PCH2PPh(C6H4)}-
(CO)8] with triethylsilane
References
A similar reaction to that above using [Os3(l-H){l3-Ph2PCH2-
PPh(C6H4)}(CO)8] (0.097 g, 0.082 mmol) with Et3SiH (262 lL,
1.643 mmol) for 10 h followed by a similar chromatographic
separation gave two bands. The first band gave [Os3(l-
1 P. Braunstein and M. Knorr, J. Organomet. Chem., 1995, 500, 21;
P. Braunstein, M. Knorr and C. Stern, Coord. Chem. Rev., 1998,
178–180, 903.
2 H. Hashimoto, Y. Hayashi, I. Aratani, C. Kabuto and M. Kira,
Organometallics, 2002, 21, 1534 and references therein.
3 R. D. Adams, J. E. Cortopassi and M. P. Pompeo, Organometallics,
1992, 11, 1.
4 H. Nagashima, A. Suzuki, T. Iura, K. Ryu and K. Matsubara,
Organometallics, 2000, 19, 3579.
5 K. Matsubara, K. Ryu, T. Maki, T. Iura and H. Nagashima,
Organometallics, 2002, 21, 3023.
6 R. J. Hall, P. Serguievski and J. B. Keister, Organometallics, 2000, 19,
4499.
H)2(SiEt3){l3-Ph2PCH2PPh(C6H4)}(CO)7]
5
(0.055 g, 53%)
as yellow crystals from a hexane–CH2Cl2 mixture at 0 °C.
Anal. for 5: calc. for C38H38O7Os3P2Si, C, 36.01; H, 3.03.
Found: C, 36.12; H, 3.15%; IR [m(CO), CH2Cl2]: 2064s, 2015s,
2000vs, 1989s, 1940s cm−1. The other band gave the cluster
[Os3H(SiEt3)(CO)9(dppm)] 2 (0.092 g, 45%) as orange crystals
from a hexane–CH2Cl2 mixture at 4 °C. Anal. for 2: calc. for
C40H38O9Os3P2Si, C, 36.30; H, 2.90. Found: C, 36.42; H, 2.98%;
IR [m(CO), CH2Cl2]: 2082w, 2042s, 2000vs, 1967m, 1957m cm−1.
7 R. D. Adams, J. E. Cortopassi and M. P. Pompeo, Inorg. Chem.,
1991, 30, 2960 and R. D. Adams, J. E. Cortopassi and M. P.
Pompeo, Inorg. Chem., 1992, 31, 2563.
Reaction of the cluster [Os3(l-H){l3-Ph2PCH2PPh(C6H4)}-
(CO)8] with dimethylethylsilane
8 B. F. G. Johnson, J. Lewis, M. Monari, D. Braga, F. Grepioni and
C. Gradella, J. Chem. Soc., Dalton Trans., 1990, 2863.
9 F. W. B. Einstein, R. K. Pomeroy and A. C. Willis, J. Organomet.
Chem., 1986, 311, 257.
Similarly using [Os3(l-H){l3-Ph2PCH2PPh(C6H4)}(CO)8]
(0.102 g, 0.087 mmol) with Me2EtSiH (210 lL, 1.74 mmol)
D a l t o n T r a n s . , 2 0 0 4 , 3 7 0 9 – 3 7 1 4
3 7 1 3

View Article Online
10 H. G. Ang, B. Chang, W. L. Kwik and E. S. H. Sim, J. Organomet.
Chem., 1994, 474, 153.
11 R. D. Adams, J. E. Cortopassi, J. Aust and M. Myrick, J. Am. Chem.
Soc., 1993, 115, 8877.
12 R. D. Adams, B. Captain and W. Fu, Organometallics, 2000, 19, 3670.
13 P. Braunstein, J. R. Galworthy and W. Massa, J. Chem. Soc., Dalton
Trans., 1997, 4677.
14 J. A. Clucas, D. F. Foster, M. M. Harding and A. K. Smith, J. Chem.
Soc., Chem. Commun., 1984, 949.
15 gNMR, Ver. 4.1, Cherwell Scientific Ltd., Oxford, UK, 1995.
16 SMART and SAINT+ software for CCD diffractometers, version 6.1,
Bruker AXS, Madison, WI, 2000.
17 G. M. Sheldrick, SHELXTL PLUS, version 6.1, Bruker AXS Inc.,
Madison, WI, 2000.
3 7 1 4
D a l t o n T r a n s . , 2 0 0 4 , 3 7 0 9 – 3 7 1 4