Synthesis, characterization, and reactivity study of triosmium acetylide cluster complexes bearing a (C5Me5)W(O)2 fragment

Article abstract of DOI:10.1021/om970575d

The heterometallic cluster compound (C₅-Me₅)W(μ-O)₂Os ₃(μ-CCPh)(CO)₉(1), which possesses two edge-bridging oxo groups and an acetylide ligand in a μ-η² mode, has been obtained by addition Of (C₅Me₅)W-(O)₂(CCPh) to Os₃(CO)₁₀(NCMe)₂. The subsequent reactivity studies led to the isolation of Cp* W(μ-O)₂Os₃(μ-H)(CO)₉ (2) and Cp*W(O)(μ-O)Os₃(CCPh)(CO)₉ (3) through hydrogenation and treatment with pressurized CO, respectively. The structures of 1 and 3 reveal two distinctive bonding modes for the (C₅Me₅)W(O)₂ fragment on an Os₃ skeleton.

Full text of DOI:10.1021/om970575d

5368
Organometallics 1997, 16, 5368-5371
Syn th esis, Ch a r a cter iza tion , a n d Rea ctivity Stu d y of
Tr iosm iu m Acetylid e Clu ster Com p lexes Bea r in g a
(C5Me5)W(O)2 F r a gm en t
Chin-Wei Shiu,† Yun Chi,*,† Arthur J . Carty,*,‡ Shie-Ming Peng,*,§ and
Gene-Hsiang Lee§
Department of Chemistry, National Tsing Hua University, Hsinchu 30043, Taiwan, Steacie
Institute for Molecular Sciences, National Research Council Canada, 100 Sussex Drive,
Ottawa, Ontario K1A 0R6, Canada, and Department of Chemistry and Instrumentation
Center, National Taiwan University, Taipei 10764, Taiwan
Summary: The heterometallic cluster compound (C5-
Me5)W(µ-O)2Os3(µ-CCPh)(CO)9 (1), which possesses two
edge-bridging oxo groups and an acetylide ligand in a
µ-η2 mode, has been obtained by addition of (C5Me5)W-
(O)2(CCPh) to Os3(CO)10(NCMe)2. The subsequent re-
activity studies led to the isolation of Cp*W(µ-O)2Os3(µ-
H)(CO)9 (2) and Cp*W(O)(µ-O)Os3(CCPh)(CO)9 (3)
through hydrogenation and treatment with pressurized
CO, respectively. The structures of 1 and 3 reveal two
distinctive bonding modes for the (C5Me5)W(O)2 frag-
ment on an Os3 skeleton.
cleavage of an acyl functional group, provides a remark-
able milestone of this indirect approach.
In this study, we wish to report the synthesis and
identification of three WOs3 cluster complexes which
were prepared from a sequence initiated by combining
the dioxo acetylide complex (C5Me5)W(O)2(CCPh)5 and
the lightly stabilized triosmium complex Os3(CO)10-
(NCMe)2.6 The products obtained inherit a (C5Me5)W-
(O)2 fragment from their starting materials; therefore,
their structural and reactivity properties would differ
greatly from those of the previously reported WO3 oxo-
alkylidyne compounds4 as well as our WRe2 and WRe
oxo-acetylide complexes,7 which possess only one oxo
ligand in either an edge-bridging or terminal mode.
Organometallic complexes containing oxo ligands
serve as realistic models for metal-mediated oxidation
and other homogeneous and heterogeneous reactions
with high-valent metal species as catalysts.1 As a
result, a large number of transition-metal oxo complexes
have been synthesized; their reactivities with organic
substrates have been explored.2 The critical informa-
tion obtained has helped chemists to better understand
the mechanism of these oxidation reactions catalyzed
by discrete oxometal complexes.3 Alternatively, the
second approach is to synthesize complexes bearing both
oxo and hydrocarbyl ligands and to examine the role of
oxo ligands on the chemical reactivity of such complexes.
The investigation on the chemistry of a heterometallic
complex with the formula CpW(µ-O)Os3(µ3-CCH2Tol)-
(CO)9,4 which was prepared from the direct C-O bond
Exp er im en ta l Section
Gen er a l In for m a tion a n d Ma ter ia ls. Infrared spectra
were recorded on a Perkin-Elmer 2000 FT-IR spectrometer.
1H and 13C NMR spectra were recorded on a Bruker AM-400
(400.13 MHz) or a Bruker AMX-300 (300.6 MHz) instrument.
Mass spectra were obtained on a J EOL-HX110 instrument
operating in the fast atom bombardment mode (FAB). All
reactions were performed under a nitrogen atmosphere using
solvents dried with an appropriate reagent. The products were
separated on commercially available preparative thin-layer
chromatographic plates (Kieselgel 60 F254, E. Merck). Elemen-
tal analyses were performed at the NSC Regional Instrumen-
tation Center at National Cheng Kung University, Tainan,
Taiwan.
R ea ct ion of Os3(CO)10(NCMe)2 w it h (C5Me5)W(O)2-
(CCP h ). A toluene solution (60 mL) of Os3(CO)10(NCMe)2 (247
mg, 0.265 mmol) and (C5Me5)W(O)2(CCPh) (100 mg, 0.224
mmol) was heated at 80 °C for 30 min. The solvent was
removed under vacuum, the mixture was dissolved in a
minimum amount of CH2Cl2, and this solution was subjected
to thin-layer chromatography with a 1:1 mixture of CH2Cl2
and hexane, affording 160 mg of orange (C5Me5)W(µ-O)2Os3-
(µ-CCPh)(CO)9 (1; 0.125 mmol, 56%). Crystals of complex 1
suitable for X-ray diffraction study were recrystallized from a
mixture of CH2Cl2 and methanol at room temperature.
Spectral data for 1 are as follows. MS (FAB, 184W, 192Os):
m/z 1280 (M+). IR (C6H12): ν(CO) 2088 (m), 2069 (vs), 2026
† National Tsing Hua University.
‡ National Research Council Canada.
§ National Taiwan University.
X Abstract published in Advance ACS Abstracts, November 1, 1997.
(1) (a) Nugent, W. A.; Mayer, J . M. Metal-Ligand Multiple Bonds;
Wiley-Interscience: New York, 1988. (b) Bottomley, F.; Sutin, L. Adv.
Organomet. Chem. 1988, 28, 339. (c) Schauer, C. K.; Voss, E. J .; Sabat,
M.; Shriver, D. F. J . Am. Chem. Soc. 1989, 111, 7662. (d) Atagi, L.
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113, 870. (e) Legzdins, P.; Phillips, E. C.; Rettig, S. J .; Trotter, J .;
Veltheer, J . E.; Yee, V. C. Organometallics 1992, 11, 3104. (f) Dobbs,
D. A.; Bergman, R. G. J . Am. Chem. Soc. 1993, 115, 3836. (g) Hao, L.;
Xiao, J .; Vittal, J .; Puddephatt, R. J . Angew. Chem., Int. Ed. Engl. 1995,
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457.
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Donahue, J . P. Polyhedron 1993, 12, 571. (c) Woo, L. K. Chem. Rev.
1993, 93, 1125. (d) Dickman, M. H.; Pope, M. T. Chem. Rev. 1994, 94,
569. (e) Herrmann, W. A.; Kuehn, F. E. Acc. Chem. Res. 1997, 30,
169.
(3) (a) Clarke, R.; Gahagan, M.; Mackie, R. K.; Foster, D. F.; Cole-
Hamilton, D. J .; Nicol, M.; Montford, A. W. J . Chem. Soc. Dalton Trans.
1995, 1221. (b) Herrmann, W. A.; Fischer, R. W.; Rauch, M. U.;
Scherer, W. J . Mol. Catal. 1994, 86, 243. (c) Herrmann, W. A. J .
Organomet. Chem. 1995, 500, 149. (d) Herrmann, W. A.; Correia, J .
D. G.; Kuehn, F. E.; Artus, G. R. J .; Romao, C. C. Chem. Eur. J . 1996,
2, 168. (e) Belgacem, J .; Kress, J .; Osborn, J . A. J . Mol. Catal. 1994,
86, 267.
(vs), 2003 (s, br), 1969 (m), 1933 (w) cm-1 1H NMR (300 MHz,
.
CDCl3, 297 K): δ 7.38-7.20 (m, 5H), 2.12 (s, 15H). 13C NMR
(75 MHz, CDCl3, 297 K): δ 186.8 (1CO, J WC ) 9 Hz), 185.1
(2CO), 178.3 (2CO), 172.8 (2CO), 169.5 (2CO); δ 130.9 (2C,
o-C6H5), 128.5 (1C, p-C6H5), 128.4 (2C, m-C6H5), 127.9 (1C,
(5) Shiu, C.-H.; Su, C.-J .; Pin, C.-W.; Chi, Y.; Peng, S.-M.; Lee, G.-
H. J . Organomet. Chem., in press.
(6) Nicholls, J . N.; Vargas, M. D. Inorg. Synth. 1990, 28, 232.
(7) (a) Chi, Y.; Cheng, P.-S.; Wu, H.-L.; Hwang, D.-K.; Peng, S.-M.;
Lee, G.-H. J . Chem. Soc., Chem. Commun. 1994, 1839. (b) Lai, N.-S.;
Tu, W.-C.; Chi, Y.; Peng, S.-M.; Lee, G.-H. Organometallics 1994, 13,
4652. (c) Chi, Y.; Wu, H.-L.; Chen, C.-C.; Su, C.-J .; Peng, S.-M.; Lee,
G.-H. Organometallics 1997, 16, 2443.
(4) (a) Shapley, J . R.; Park, J .-T.; Churchill, M. R.; Ziller, J . W.;
Beanan, L. R. J . Am. Chem. Soc. 1984, 106, 1144. (b) Park, J . T.;
Shapley, J . R.; Churchill, M. R.; Bueno, C. Inorg. Chem. 1983, 22, 1579.
S0276-7333(97)00575-X CCC: $14.00 © 1997 American Chemical Society

Notes
Organometallics, Vol. 16, No. 24, 1997 5369
Ta ble 1. X-r a y Str u ctu r a l Da ta for Com p lexes 1
a n d 3a
i-C6H5), 115.8 (C5Me5), 102.9 (CCPh), 75.6 (CCPh), 12.2
(C5Me5). Anal. Calcd for C27H20O11Os3W: C, 25.31; H, 1.57.
Found: C, 25.31; H, 1.61.
compd
1
3
formula
mol wt
cryst syst
space group
a (Å)
C27H20O11Os3W
1274.88
orthorhombic
Pbca
18.392(8)
19.453(4)
33.906(9)
C29H20O13Os3W
1330.91
monoclinic
P21/n
12.417(4)
12.468(5)
21.896(3)
95.26(3)
3376(2)
4
Hyd r ogen a tion of 1. A toluene solution (30 mL) of (C5-
Me5)W(µ-O)2Os3(µ-CCPh)(CO)9 (1; 107 mg, 0.084 mmol) was
heated under a hydrogen atmosphere (50 psig) at 100 °C for 2
h, during which the color changed from orange to orange-red.
After removal of the solvent in vacuo, the residue was taken
up in CH2Cl2 and subjected to chromatographic workup on
TLC plates using a 1:1 mixture of CH2Cl2 and hexane, giving
38 mg of orange-red (C5Me5)W(µ-O)2Os3(µ-H)(CO)9 (2; 0.032
mmol, 39%). Crystals of 2 were obtained from a mixture of
CH2Cl2 and methanol at room temperature.
b (Å)
c (Å)
â (deg)
V (Å3)
12 131(7)
16
2.792
9068
45.0
Z
Dc (g/cm3)
F(000)
2.619
2379
50.0
2θ(max) (deg)
hkl ranges
cryst size (mm)
µ(Mo KR) (cm-1
Spectral data for 2 are as follows. MS (FAB, 184W, 192Os):
m/z 1180 (M+). IR (C6H12): ν(CO) 2094 (m), 2069 (s), 2056
(vw), 2024 (vs), 2013 (s), 2005 (m), 1987 (w), 1958 (m), 1936
0-19, 0-20, 0-36 -14 to 14, 0-14, 0-26
0.30 × 0.40 × 0.50 0.05 × 0.20 × 0.25
)
164.62
147.95
1.000, 0.371
(m) cm-1 1H NMR (300 MHz, CDCl3, 297 K): δ 2.07 (s, 15H),
.
transmission: max, min 1.000, 0.607
no. of data in refinement 3653 with I g 2σ(I) 3064 with I g 2σ(I)
no. of atoms and params 124, 758
weight modifier, g
max ∆/σ ratio
RF; Rw
-15.71 (s, 1H); 13C NMR (75 MHz, CDCl3, 297 K); CO δ 192.6,
184.0 (2CO), 174.7 (2CO), 172.0 (2CO), 169.1 (2CO); δ 116.5
(C5Me5), 11.8 (C5Me5). Anal. Calcd for C19H16O11Os3W: C,
19.43; H, 1.37. Found: C, 19.49; H, 1.41.
66, 416
0.0001
0.020
0.041; 0.039
1.39
0.000 01
0.045
0.054; 0.051
1.52
GOF
Tr ea tm en t of 1 w ith CO. A toluene solution (35 mL) of
(C5Me5)W(µ-O)2Os3(µ-CCPh)(CO)9 (1; 107 mg, 0.084 mmol) was
placed in a 100 mL stainless steel Parr high-pressure reactor
and then charged with 800 psig of CO atmosphere. After the
temperature was increased to 80 °C, the solution was continu-
ously stirred for 2 h. The CO was then released, and the
solvent was removed in vacuo; the residue was taken up in
CH2Cl2 and separated by thin-layer chromatography (1:1 CH2-
Cl2-hexane), giving 87 mg of orange (C5Me5)W(O)(µ-O)-
Os3(CCPh)(CO)11 (3; 0.065 mmol, 77%) and 7 mg of (C5Me5)W-
(O)2(CCPh) (0.016 mmol, 19%). Crystals suitable for X-ray
diffraction study were recrystallized from a mixture of CHCl3
and methanol at room temperature.
D map, max/min (e/Å3)
+2.42/-2.19
+1.79/-1.58
a
Features common to all determinations: Nonius CAD-4 dif-
fractometer, λ(Mo KR) ) 0.7107 Å; function minimized ∑(w|Fo
-
-
2
Fc| ); weighting scheme w-1 ) σ2(Fo) + |g|Fo2; GOF ) [∑w|Fo
2
Fc| /(No - Nv)]1/2 (No ) number of observations; Nv ) number of
variables).
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) of 1 (Esd ’s in P a r en th eses)
W-Os(1)
W-Os(3)
Os(1)-Os(3)
W-O(10)
Os(1)-O(10)
Os(1)-C(10)
Os(2)-C(11)
2.981(2)
2.603(3)
2.891(2)
1.76(2)
2.10(2)
2.13(4)
2.33(4)
W-Os(2)
3.014(2)
3.841(3)
2.938(3)
1.76(3)
2.16(2)
2.34(3)
1.11(5)
Os(1)‚‚‚Os(2)
Os(2)-Os(3)
W-O(11)
Os(2)-O(11)
Os(2)-C(10)
C(10)-C(11)
Spectral data for 3 are as follows. MS (FAB, 184W, 192Os):
m/z 1336 (M+). IR (C6H12): ν(CO) 2119 (w), 2092 (vs), 2045
(vs), 2019 (vs), 2012 (s), 1989 (s), 1979 (m), 1975 (w), 1967 (vw),
1958 (vw) cm-1, ν(CC) 2141 (vw) cm-1
.
1H NMR (300 MHz,
W-O(10)-Os(1)
Os(1)-C(10)-C(11) 163(3)
101(1)
W-O(11)-Os(2)
C(10)-C(11)-C(12) 156(4)
100(1)
CDCl3, 297 K): δ 7.25 (d, 2H, J HH ) 7.3 Hz), 7.17 (t, 2H, J HH
) 7.3 Hz), 7.06 (t, 1H, J HH ) 7.3 Hz), 2.10 (s, 15H). 13C NMR
(75 MHz, CDCl3, 297 K): CO δ 193.3, 189.0, 186.9, 183.5,
178.9, 177.7 (2C), 176.7, 174.5, 173.1, 162.7; δ 131.4 (2C,
o-C6H5), 127.7 (2C, m-C6H5), 127.1 (1C, i-C6H5), 125.7 (1C,
p-C6H5), 117.1 (C5Me5), 112.2 (CCPh), 65.3 (CCPh), 11.5
(C5Me5). Anal. Calcd for C29H20O13Os3W: C, 26.17; H, 1.51.
Found: C, 26.08; H, 1.59.
Ta ble 3. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) of 3 (Esd ’s in P a r en th eses)
W-Os(1)
2.723(1)
2.933(1)
1.71(1)
2.15(1)
1.20(3)
W-Os(2)
2.942(1)
2.880(1)
1.83(1)
2.08(2)
Os(1)-Os(2)
W-O(12)
Os(2)-Os(3)
W-O(13)
Os(2)-O(13)
C(12)-C(13)
Os(3)-C(12)
Th er m olysis of 3. A toluene solution (30 mL) of 3 (48 mg,
0.036 mmol) was heated at 100 °C for 2 h, during which time
the color changed from yellow to light orange. The solvent
was evaporated in vacuo, and the residue was dissolved in 3
mL of CH2Cl2. Workup of the mixture on TLC plates using a
1:2 mixture of dichloromethane and hexane gave 32 mg of 1
(0.024 mmol, 67%) followed by 2 mg of unreacted 3 (0.002
mmol, 4%).
Os(1)-Os(2)-Os(3) 174.12(4)
Os(3)-C(12)-C(13) 176(2)
W-O(13)-Os(2)
Os(1)-W-O(12)
95.1(5)
99.0(4)
O(12)-W-O(13)
Os(2)-W-O(12)
106.8(6)
97.9(3)
Resu lts a n d Discu ssion
As indicated in Scheme 1, the heterometallic acetylide
cluster compound (C5Me5)W(µ-O)2Os3(µ-CCPh)(CO)9 (1),
which possesses two edge-bridging oxo ligands, was
prepared by addition of the mononuclear acetylide
precursor (C5Me5)W(O)2(CCPh) to the bis(acetonitrile)
complex Os3(CO)10(NCMe)2. This high-yield conversion
to the isolated 1:1 adduct clearly shows the effective
coordination of the acetylide ligand to an Os atom of
the triosmium triangle at the initial stage of reaction,
which is evidenced by the facile coordination of alkyne
to Os3(CO)10(NCMe)2.8 We anticipate that the electron-
withdrawing capability of the (C5Me)5W(O)2 fragment
decreases the relative energy of the acetylide π*-orbitals
X-r a y Cr ysta llogr a p h y. The X-ray diffraction measure-
ments were carried out on a Nonius CAD-4 diffractometer at
room temperature. Lattice parameters were determined from
25 randomly selected high-angle reflections. Three standard
reflections were monitored every 3600 s. No significant change
in intensities (e2%) was observed during the course of data
collection. Intensities of the diffraction signals were corrected
for Lorentz, polarization, and absorption effects (ψ scans). The
structure was solved by using the NRCC-SDP-VAX package.
All of the non-hydrogen atoms had anisotropic temperature
factors, while the hydrogen atoms of the organic substituents
were placed at the calculated positions with UH ) UC + 0.1.
The crystallographic refinement parameters of complexes 1
and 3 are given in Table 1, while their selected bond distances
and angles are presented in Tables 2 and 3, respectively.
(8) (a) Aime, S.; Deeming, A. J . J . Chem. Soc., Dalton Trans. 1983,
1807. (b) Deeming, A. J .; Senior, A. M. J . Organomet. Chem. 1992,
439, 177.

5370 Organometallics, Vol. 16, No. 24, 1997
Notes
Sch em e 1
F igu r e 1. Molecular structure and atomic labeling scheme
of the complex (C5Me5)W(µ-O)2Os3(µ-CCPh)(CO)9 (1) with
thermal ellipsoids shown at the 30% probability level.
is depicted in Figure 1. The molecule contains a WOs3
butterfly core in which the tungsten atom is capped by
a C5Me5 functional group, while each of the osmium
atoms is linked to three terminal CO ligands. An
unusual feature is the bridging oxo ligands, which are
located on the two W-Os bonds of nearly equal length
(2.981(2) and 3.014(2) Å). The bond lengths to the oxo
ligands (average W-O ) 1.76(3) Å, Os-O ) 2.13(3) Å)
are similar to that of the WdOfOs bonding mode,11 and
the average Os-O distance is slightly longer than the
Os-O distance (2.06(2) Å) in Os6(µ3-O)(µ3-CO)(CO)18,12
and [Os(µ3-O)(CO)3]4.13 In addition, the W-Os(3) dis-
tance (2.603(3) Å) is significantly shorter than the other
W-Os distances which support the bridging oxo ligands.
In fact, this W-Os distance is the shortest W-Os single
bond ever observed in the related W-Os carbonyl
cluster complexes.14 We believe that this unusually
short W-Os distance is caused by a combined effect of
the contraction of the atomic radius for the tungsten
atom due to the greater formal nuclear charge and the
lack of a bridging oxo ligand.
and therefore increases the metal-to-acetylide ligand
back-π-bonding, serving as the key factor in improving
the yields with respect to the poor yields (∼11%) for the
similar cluster-building reactions using (C5Me5)W(CO)3-
(CCPh) and Os3(CO)10(NCMe)2.9 The second possibility
involves the prior coordination of the oxo ligand lone
pair with the triosmium framework, which then induces
the subsequent capping of the acetylide ligand. This
reaction pathway is supported by examples in the
literature where coordination of a lone pair is the initial
step in the reaction of Os3(CO)10(NCMe)2 with donor
molecules and where C-H and C-X bonds are also
activated.10 We cannot differentiate these two possibili-
ties at present; however, it is certain that the transfor-
mation was completed by the cleavage of the W-C(acetyl-
ide) σ-bonding and generation of the observed Os-
C(acetylide) σ-interaction and strengthening of the
bonding between the (C5Me5)W(O)2 fragment and the
triosmium framework.
The Os(1)‚‚‚Os(2) distance (3.841(3) Å) is clearly out
of the range expected for an Os-Os single bond; e.g.,
the average Os-Os distance in Os3(CO)12 is 2.877(1) Å.15
The acetylide ligand is linked to the Os(1) and the Os-
(11) (a) Churchill, M. R.; Bueno, C.; Park, J . T.; Shapley, J . R. Inorg.
Chem. 1984, 23, 1017. (b) Chi, Y.; Shapley, J . R.; Churchill, M. R.; Li,
Y.-J . Inorg. Chem. 1986, 25, 4165. (c) Chi, Y.; Shapley, J . R.; Ziller, J .
W.; Churchill, M. R. Organometallics 1987, 6, 301. (d) Park, J .-T.;
Chung, M.-K.; Chun, K. M.; Yun, S. S.; Kim, S. Organometallics 1992,
11, 3313. (e) Gong, J .-H.; Chen, C.-C.; Chi, Y.; Wang, S.-L.; Liao, F.-
L. J . Chem. Soc., Dalton Trans. 1993, 1829. (f) Park, J . T.; Chi, Y.;
Shapley, J . R.; Churchill, M. R.; Ziller, J . W. Organometallics 1994,
13, 813.
According to the X-ray diffraction analysis, complex
1 was crystallized in an asymmetric unit possessing two
crystallographically distinct but structurally similar
molecules. A perspective view of one of these molecules
(12) Goudsmit, R. J .; J ohnson, B. F. G.; Lewis, J .; Raithby, P. R.;
Whitmire, K. H. J . Chem. Soc., Chem. Commun. 1983, 246.
(13) Bright, D. J . Chem. Soc. D 1970, 1169.
(9) (a) Chi, Y.; Lee, G.-H.; Peng, S.-M.; Wu, C.-H. Organometallics
1989, 8, 1574. (b) Chi, Y.; Wu, C.-H.; Peng, S.-M.; Lee, G.-H.
Organometallics 1990, 9, 2305. (c) Su, P.-C.; Chiang, S.-J .; Chang,
L.-L.; Chi, Y.; Peng, S.-M.; Lee, G.-H. Organometallics 1995, 14, 4844.
(d) Chi, Y.; Chung, C.; Chou, Y.-C.; Su, P.-C.; Chiang, S.-J .; Peng, S.-
M.; Lee, G.-H. Organometallics 1997, 16, 1702.
(10) (a) Day, M.; Espitia, D.; Hardcastle, K. I.; Kabir, S. E.;
McPhillips, T.; Rosenberg, E.; Gobetto, R.; Milone, L.; Osella, D.
Organometallics 1993, 12, 2309. (b) Azam, K. A.; Dilshad, R.; Kabir,
S. E.; Khatoon, K.; Nessa, L.; Rahman, M. M.; Rosenberg, E.;
Hursthouse, M. B.; Malik, K. M. A.; Deeming, A. J . J . Chem. Soc.,
Dalton Trans. 1996, 1731.
(14) (a) Churchill, M. R.; Hollander, F. J .; Shapley, J . R.; Foose, D.
S. J . Chem. Soc., Chem. Commun. 1978, 534. (b) Park, J . T.; Shapley,
J . R.; Bueno, C.; Ziller, J .W.; Churchill, M. R. Organometallics 1988,
7, 2307. (c) Gong, J .-H.; Hwang, D.-K.; Tsay, C.-W.; Chi, Y.; Peng,
S.-M.; Lee, G.-H. Organometallics 1994, 13, 1720. (d) Kuo, M.-T.;
Hwang, D.-K.; Liu, C.-S.; Chi, Y.; Peng, S.-M.; Lee, G.-H. Organome-
tallics 1994, 13, 2142. (e) Gong, J .-H.; Tsay, C.-W.; Tu, W.-C.; Chi,
Y.; Peng, S.-M.; Lee, G.-H. J . Cluster Sci. 1995, 6, 289. (f) Huang,
T.-K.; Chi, Y.; Peng, S.-M.; Lee, G.-H.; Wang, S.-L.; Liao, F.-L.
Organometallics 1995, 14, 2164.
(15) Churchill, M. R.; DeBoer, B. G. Inorg. Chem. 1977, 16, 878.

Notes
Organometallics, Vol. 16, No. 24, 1997 5371
(2) atoms via σ-bonding and π-interaction, respectively.
Such a µ2-η2 bonding interaction of an acetylide ligand
has been observed in a few acetylide cluster complexes,16
but complex 1 indicates an uncommon instance where
the acetylide fragment spans two nonbonding metal
atoms with nearly identical π-bonding distances: Os-
(2)-C(10) ) 2.34(3) Å and Os(2)-C(11) ) 2.33(4) Å.
Moreover, the acetylide ligand undergoes a facile σ f
π, π f σ rearrangement in solution (Scheme 1). This
is suggested by the 13C NMR spectrum, which exhibited
five sharp CO resonances at δ 186.8 (J WC ) 9 Hz), 185.1,
178.3, 172.8, and 169.5 in the ratio 1:2:2:2:2 at room
temperature, suggesting the presence of a dynamic
plane of mirror symmetry which bisects the whole
molecule. This behavior is consistent with the fluxion-
ality of edge-bridging alkenyl or acetylide ligands,17
which also showed similar σ f π, π f σ exchanging
between the two metal sites. When the temperature
was lowered to 183 K, the CO signals at δ 185.1, 178.3,
and 169.5 split to form three pairs of very broad signals
at δ 187.0 and 182.8, 178.8 and 175.7, and 170.8 and
166.8. From the coalescence temperature of 198 K, an
estimated ∆Gq value of 9 kcal/mol is obtained for the
activation energy barrier, which is slightly lower than
that observed in the prior cases (10-12 kcal/mol),16a
where the acetylide ligand undergoes exchange across
two bonded metal atoms.
F igu r e 2. Molecular structure and atomic labeling scheme
of the complex (C5Me5)W(O)(µ-O)Os3(CCPh)(CO)11 (3) with
thermal ellipsoids shown at the 30% probability level.
(O)(µ-O)Os3(CO)11(CCPh) (3), which is produced by
addition of two CO molecules (Scheme 1), and a small
amount of acetylide complex (C5Me5)W(O)2(CCPh), pre-
sumably produced by unwanted cluster degradation.
Complex 3 was characterized by spectroscopic methods
and by an X-ray diffraction study (Figure 2). The key
features involve the formation of a terminal acetylide
group on the Os(3) atom and the shifting of one edge-
bridging oxo ligand to the terminal mode, which is
somewhat related to that observed in the cluster (C5-
Me5)W(O)2Ru4(CO)10(µ4-PPh)(CCPh).19 Again, the un-
bridged W-Os(1) distance (2.723(1) Å) is the shortest
metal-metal bond within the whole molecule (W-Os-
(2) ) 2.942(1) Å, Os(1)-Os(2) ) 2.933(1) Å, and Os(2)-
Os(3) ) 2.880(1) Å), a consequence related to the smaller
atomic radius for the tungsten atom at the higher
oxidation state. Finally, thermolysis of 3 in toluene
afforded 1 in high yield. This reactivity pattern sug-
gests that both the acetylide and the terminal oxo
ligands are good multiple electron donors,7 which are
capable of stabilizing the cluster by compensating the
unsaturation created by CO elimination, via edge-
bridging (i.e. µ-η2-CCPh and µ-O modes) through dona-
tion of their π-electrons and lone-pair electrons, respec-
tively.
With respect to the reactivity of 1, the acetylide ligand
can be easily removed upon treatment with dihydrogen,
giving the compound (C5Me5)W(µ-O)2Os3(CO)9(µ-H) (2),
in which the metal skeleton now adopts a tetrahedral
arrangement with a hydride spanning the unique Os-
Os edge (Scheme 1). The mass spectrum of 2 gave a
1
strong molecular ion. The H NMR spectrum showed
one high-field signal at δ -15.71 for the hydride ligand.
The five CO signals at δ 192.6, 184.0, 174.7, 172.0, and
169.1 with the expected 1:2:2:2:2 ratio were observed
in the 13C NMR spectrum, suggesting the existence of
Cs symmetry. Most importantly, the IR ν(CO) spectrum
showed a CO stretching pattern which is identical with
that of the structurally characterized Cp complex CpW-
(µ-O)2Os3(CO)9(µ-H).18 Thus, these spectroscopic data
provide unambiguous confirmation for the proposed
structure.
In addition to the hydrogenation reaction discussed,
we also examined the reaction of 1 with carbon mon-
oxide in order to better understand its reactivity. Thus,
we isolated the spiked triangular complex (C5Me5)W-
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Ack n ow led gm en t. This work was supported by
grants from the National Research Council of Canada,
the Natural Sciences and Engineering Research Council
of Canada (to A.J .C.), and the National Science Council
of Taiwan (to Y.C.; Grant No. NSC 86-2113-M007-035).
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates and the corresponding anisotropic thermal pa-
rameters for complexes 1 and 3 (12 pages). Ordering informa-
tion is given on any current masthead page.
OM970575D
(19) Blenkiron, P.; Carty, A. J .; Peng, S.-M.; Lee, G.-H.; Su, C.-J .;
Shiu, C.-W.; Chi, Y. Organometallics 1997, 16, 519.