Carbon-hydrogen bond activation of phenyldi(2-thienyl)phosphine at a triosmium cluster centre

Article abstract of DOI:10.1016/j.ica.2010.01.030

The phenyldi(2-thienyl)phosphine (PhPTh₂) complexes [Os₃(CO)_12-n(PhPTh₂)_n] (n = 1-3) (1-3) have been prepared. Thermolysis of 1 and either 2 or 3 in octane affords carbon-hydrogen bond activation products [Os₃(CO)₉{μ₃-PPhTh(C₄H₂S)}(μ-H)] (4) and [Os₃(CO)₈(PPhTh₂){μ₃-PPhTh(C₄H₂S)}(μ-H)] (5), respectively. Both exist as isomeric mixtures differing in the relative positions of phenyl and thienyl substituents with respect to the triosmium centre. The nature of the process has been confirmed by a single crystal X-ray diffraction analysis of 4.

Full text of DOI:10.1016/j.ica.2010.01.030

Inorganica Chimica Acta 363 (2010) 1611–1614
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Note
Carbon–hydrogen bond activation of phenyldi(2-thienyl)phosphine at a
triosmium cluster centre
Shishir Ghosh a, Graeme Hogarth b, Derek A. Tocher b, Ebbe Nordlander c, 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 0AJ, UK
c Inorganic Chemistry Research Group, Chemical Physics, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, SE-22100 Lund, Sweden
a r t i c l e i n f o
a b s t r a c t
Article history:
The phenyldi(2-thienyl)phosphine (PhPTh2) complexes [Os3(CO)12Àn(PhPTh2)n] (n = 1–3) (1–3) have been
prepared. Thermolysis of 1 and either 2 or 3 in octane affords carbon–hydrogen bond activation products
[Os3(CO)9{l3-PPhTh(C4H2S)}(l-H)] (4) and [Os3(CO)8(PPhTh2){l3-PPhTh(C4H2S)}(l-H)] (5), respectively.
Both exist as isomeric mixtures differing in the relative positions of phenyl and thienyl substituents with
respect to the triosmium centre. The nature of the process has been confirmed by a single crystal X-ray
diffraction analysis of 4.
Received 25 November 2009
Accepted 22 January 2010
Available online 29 January 2010
Keywords:
Triosmium clusters
Phenyldi(2-thienyl)phosphine
Carbon–hydrogen bond activation
X-ray structures
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
ligand [7]. In contrast, the reactions of PTh3 and PPh2Th with
Os3(CO)12 and [Os3(CO)10(l-H)2] lead to the formation of both sim-
The reactivity of thienyl phosphines with transition metal car-
bonyl clusters continues to of considerable interest since they ex-
ple substitution and metalated products [8,9]. As part of our work
on the reactivity of functionalized phosphines with trimetallic
clusters, we have studied the reactions of PPhTh2 with triosmium
clusters [Os3(CO)12Àn(NCMe)n] (n = 0, 1, 2), the results of which
are described herein.
hibit
a variety of coordination modes and cluster-mediated
rearrangements the nature of which has relevance to modeling
the industrially important catalytic hydrodesulfurization process
[1–9]. In this context, their reactivity with triruthenium and trios-
mium clusters has been investigated quite thoroughly in recent
years. In 1995, Vahrenkamp and co-workers reported that the reac-
tion of tri(2-thienyl)phosphine (PTh3) with Ru3(CO)12 gave low
yields of both [Ru3(CO)10(PTh3)2] and trans-[Ru(CO)3(PTh3)2] in
which the ligand acts as a simple tertiary phosphine [5]. In the fol-
lowing year, Deeming and co-workers detailed the reactivity of di-
phenyl(2-thienyl)phosphine (PPh2Th) with Ru3(CO)12 leading to
both carbon–hydrogen and carbon–phosphorus bond cleavage
2. Experimental
All manipulations were carried out under an inert atmosphere
of nitrogen using standard Schlenk techniques. Reagent-grade sol-
vents were dried and distilled by standard methods prior to use.
Infrared spectra were recorded on a Shimadzu FTIR 8101 spectro-
photometer. NMR spectra were recorded on Bruker DPX 400
instruments. Elemental analyses were performed by Microanalyti-
cal Laboratories, University College London. Os3(CO)12 was pur-
chased from Strem Chemicals Inc. and used without further
purification and the clusters [Os3(CO)11(NCMe)] and [Os3(-
CO)10(NCMe)2] were prepared according to the literature methods
[10].
and affording complexes containing cyclometalated
and 4-thiophyne ligands [6]. More recently, we reported the reac-
tivity of [Ru3(CO)10 -dppm)] with PTh3. This initially affords the
simple substitution product [Ru3(CO)9(PTh3)( -dppm)] which
l3-Ph2PC4H2S
l
(l
l
upon mild heating undergoes carbon–hydrogen, carbon–phospho-
rus and carbon–sulfur bond cleavage to afford the thiophyne clus-
ter [Ru3(CO)7(
thiophyne ring-opened cluster [Ru3(CO)5(
SC4H2){ -PTh2}], the latter being a unique example of an open
l
-dppm)(l3
-
g
2-C4H2S){
l
-PTh2}(
l
l
-H)] and the
-dppm)(l3
2.1. Reaction of [Os3(CO)11(NCMe)] with PPhTh2
l-CO)(
- -
g3
l
PPhTh2 (45 mg, 0.164 mmol) was added to a CH2Cl2 solution
(30 mL) of [Os3(CO)11(NCMe)] (151 mg, 0.164 mmol) and the reac-
tion mixture was then stirred at 25 °C for 24 h. The solvent was re-
moved under reduced pressure and the residue chromatographed
by TLC on silica gel. Elution with hexane/CH2Cl2 (9:1, v/v)
triruthenium cluster containing a capping 1-thia-1,3-butadiene
* Corresponding author.
E-mail address: skabir_ju@yahoo.com (S.E. Kabir).
0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.01.030

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S. Ghosh et al. / Inorganica Chimica Acta 363 (2010) 1611–1614
developed only one band which afforded [Os3(CO)11(PPhTh2)] (1)
(165 mg, 87%) as yellow crystals from hexane/CH2Cl2 at 4 °C. Spec-
tral data for 1: Anal. Calc. for C25H11O11Os3PS2: C, 26.04; H, 0.96.
was then heated to reflux for 8 h. The solvent was removed by ro-
tary evaporation and the residue subjected to TLC on silica gel for
chromatographic separation. Elution with hexane/CH2Cl2 (7:3, v/v)
Found: C, 26.38; H, 1.01%. IR (
m
co, CH2Cl2): 2109 m, 2056 s, 2036
developed four bands. The first band gave unreacted [Os3(CO)12]
m, 2019 s, 1989 m, 1977 m, 1954 w cmÀ1
.
1H NMR (CDCl3): d
(trace). The second band gave a mixture of 1 and 4 (98 mg) while
the third band afforded a mixture of 2 and 5 (71 mg). Compounds
1 and 4 had not been separated by chromatographic techniques
due to their similar Rf value while fractional crystallization tech-
nique was doubtful in this case since the crystals of both com-
pounds have the same yellow color. The same arguments are
true for compound 2 and 5. The fourth band afforded [Os3(-
CO)9(PPhTh2)3] (3) (17 mg, 5%) as red crystals from hexane/CH2Cl2
at 4 °C. Spectral data for 5: Anal. Calc. for C51H33O9Os3P3S6: C,
7.67 (m, 2H), 7.43 (m, 4H), 7.34 (m, 3H), 7.20 (m, 2H). 31P{1H}
NMR (CDCl3): d À30.5 (s). MS (m/z): 1152 (M+).
2.2. Reaction of [Os3(CO)10(NCMe)2] with PPhTh2
To a CH2Cl2 solution (30 mL) of [Os3(CO)10(NCMe)2] (200 mg,
0.214 mmol) was added PPhTh2 (121 mg, 0.441 mmol) and the
mixture was stirred at 25 °C for 24 h. The solvent was removed un-
der reduced pressure and the residue chromatographed by TLC on
silica gel. Elution with hexane/CH2Cl2 (7:3, v/v) developed two
bands which afforded 1 (45 mg, 18%) and [Os3(CO)10(PPhTh2)2}]
(2) (190 mg, 63%) as orange crystals after recrystallization from
hexane/CH2Cl2 at 4 °C. Spectral data for 2: Anal. Calc. for
C38H22O10Os3P2S4: C, 32.61; H, 1.58. Found: C, 32.87; H, 1.64%. IR
37.22; H, 2.02. Found: C, 37.53; H, 2.08%. IR (mCO, CH2Cl2): 2001
m, 1979 s, 1947 m cmÀ1 1H NMR (CDCl3): d 7.57 (m, 6H), 7.39
.
(m, 21H), 7.14 (m, 6H). 31P{1H} NMR (CDCl3): d À33.7 (s). MS
(m/z): 1644 (M+).
2.6. Thermolysis of 3
(mco, CH2Cl2): 2088 w, 2033 s, 2014 m, 2001 vs 1972 m, 1957
w cmÀ1 1H NMR (CDCl3): d 7.62 (m, 4H), 7.39 (m, 14H), 7.18 (m,
.
An octane solution (15 mL) of 3 (17 mg, 0.010 mmol) was
heated to reflux for 45 min. A similar chromatographic separation
to that above afforded 5 (5 mg, 36%).
4H). 31P{1H} NMR (CDCl3): major isomer: d À31.6 (br, s); minor
isomer: d À34.8 (br, s). MS (m/z): 1398 (M+).
2.3. Thermolysis of 1
2.7. Crystallography
An octane solution (15 mL) of 1 (45 mg, 0.039 mmol) was
heated to reflux for 5 h. The solvent was removed under reduced
pressure. Preparative TLC of the residue on silica gel, using hex-
ane/CH2Cl2 (4:1, v/v) as eluent developed two bands. The second
Single crystals of 4 suitable for X-ray diffraction were grown by
slow diffusion of hexane into a dichloromethane solution at 4 °C.
All geometric and crystallographic data were collected at 150 K
on a Bruker SMART APEX CCD diffractometer using Mo K
a radia-
band afforded [Os3(CO)9{l3-PPhTh(C4H2S)}(l-H)] (4) (16 mg,
tion (k = 0.71073 Å). Data reduction and integration was carried
out with SAINT+ and absorption corrections were applied using the
program SADABS [11]. The structure was solved by direct methods
and developed using alternating cycles of least-squares refinement
37%) as yellow crystals from hexane/CH2Cl2 at 4 °C while the first
band gave too little product for complete characterization. Spectral
data for 4: Anal. Calc. for C23H11O9Os3PS2: C, 25.18; H, 1.01. Found:
C, 25.49; H, 1.05%. IR (mco, CH2Cl2): 2087 s, 2059 s, 2031 s, 2015 m,
1988 m, 1959 w cmÀ1. 1H NMR (CDCl3): aromatic region (both iso-
mers): d 7.93 (m, 5H), 7.82 (m, 1H), 7.58 (m, 9H), 7.39 (m, 1H), 7.30
(m, 9H), 7.04 (m, 4H), 6.83 (m, 1H); hydride region: major isomer:
d À17.89 (d, J = 15.2 Hz), minor isomer: d À18.20 (d, J = 15.2 Hz).
31P{1H} NMR (CDCl3): major isomer: d À21.8 (s); minor isomer: d
À17.9 (s).
Table 1
Crystallographic data and structure refinement for 4.
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
C23H11O9Os3PS2
1097.01
150(2)
0.71073
Monoclinic
P21/c
2.4. Thermolysis of 2
10.3403(13)
12.5841(16)
20.625(3)
90
92.279(2)
An octane solution (20 mL) of 2 (75 mg, 0.054 mmol) was heated
to reflux for 5 h. The solvent was removed under reduced pressure
and the residue chromatographed by TLC on silica gel. Elution with
hexane/CH2Cl2 (7:3, v/v) developed two bands. The slower moving
b (Å)
c (Å)
a
(°)
b (°)
band afforded [Os3(CO)8(PPhTh2){l3-PPhTh(C4H2S)}(l-H)] (5)
c
(°)
90
2681.6(6)
4
2.717
14.445
1984
0.42 Â 0.38 Â 0.22
1.90–28.40
À13 6 h P 13
À16 6 k P 16
À27 6 l P 26
22141
Volume (Å3)
(40 mg, 55%) as orange crystals from hexane/CH2Cl2 at 4 °C while
the content of the faster moving band was too small for complete
characterization. Spectral data for 5: Anal. Calc. for
C37H22O8Os3P2S4: C, 32.18; H, 1.65. Found: C, 32.44; H, 1.71%. IR
Z
Dcalc (mg/m3)
Absorption coefficient (mmÀ1
F(0 0 0)
)
(m .
co, CH2Cl2): 2073 s, 2029 s, 2010 s, 1991 m, 1983 m, 1955 m cmÀ1
Crystal size (mm3)
1H NMR (CDCl3): aromatic region (both isomers): d 7.85 (m, 2H),
7.64 (m, 2H), 7.50 (m, 3H), 7.43 (m, 1H), 7.28 (m, 1H), 7.14 (m,
4H), 7.01 (m, 1H), 6.95 (m, 2H), 6.78 (m, 2H), 6.46 (m, 2H), 6.24
(m, 1H); hydride region: major isomer: d À17.22 (dd, J = 15.6,
10.8 Hz), major isomer: d À17.42 (dd, J = 15.6, 10.8 Hz). 31P{1H}
NMR (CDCl3): major isomer: d À21.5 (s), À17.6 (s); minor isomer:
d À18.5 (s), À11.5 (s).
h Range for data collection (°)
Index ranges
Reflections collected
Independent reflections
Completeness to h = 67.10°
Refinement method
Maximum and minimum transmission
Data/restraints/parameters
Goodness-of-fit on F2
6382 [Rint = 0.0551]
99.80%
Full-matrix least-squares on F2
0.1433 and 0.0645
6382/0/332
1.086
2.5. Reaction of [Os3(CO)12] with PPhTh2
Final R indices [I > 2
r
(I)]
R1 = 0.0435, wR2 = 0.1041
R1 = 0.0480, wR2 = 0.1070
3.833 and À2.689
R indices (all data)
PPhTh2 (121 mg, 0.441 mmol) was added to a toluene solution
(30 mL) of [Os3(CO)12] (200 mg, 0.221 mmol) and the mixture
Largest difference in peak and hole (e ÅÀ3
)

S. Ghosh et al. / Inorganica Chimica Acta 363 (2010) 1611–1614
1613
and difference-Fourier synthesis. All non-hydrogen atoms were re-
3. Results and discussion
fined anisotropically. Hydrogen atoms were placed in the calcu-
lated positions and their thermal parameters linked to those of
the atoms to which they were attached (riding model). The SHELXTL
PLUS V6.10 program package was used for structure solution and
refinement [12]. Final difference maps did not show any residual
electron density of stereochemical significance. The details of the
data collection and structure refinement are given in Table 1.
3.1. Synthesis of simple substitution complexes [Os3(CO)12Àn(PPhTh2)n]
Treatment of [Os3(CO)11(NCMe)] with PPhTh2 at ambient tem-
perature afforded the mono-phosphine substituted cluster [Os3(-
CO)11(PPhTh2)] (1) (87%), while with [Os3(CO)10(NCMe)2] both 1
(18%) and [Os3(CO)10(PPhTh2)2}] (2) (63%) were isolated. Refluxing
Os
Os
L = PPhTh2
Os
Os
Os
Os
L
L
L
L
trans-trans
cis-trans
Chart 1.
Th
S
H
Ph
(CO)3
P
125 oC
125 oC
Os
1
2 or 3
CO
L
Os
Os
CO
(CO)3
4 L = CO; 5 L = PPhTh2
Scheme 1.
Fig. 1. Molecular structure of [Os3(CO)9{l3-PPhTh(C4H2S)}(l-H)] (4) with thermal ellipsoids drawn at the 50% probability level. Ring hydrogen atoms are omitted for clarity.
Selected bond lengths (Å) and angles (°): Os(1)–Os(2) 2.8689(6), Os(1)–Os(3) 3.0171(6), Os(2)–Os(3) 2.7701(5), Os(1)–P(1) 2.344(2), Os(2)–C(10) 2.341(8), Os(3)–C(11)
2.110(9), Os(2)–C(11) 2.343(9), Os(2)–Os(1)–Os(3) 56.082(11), Os(3)–Os(2)–Os(1) 64.667(14), Os(2)–Os(3)–Os(1) 59.251(13), P(1)–Os(1)–Os(2) 73.15(5), P(1)–Os(1)–Os(3)
85.89(5), C(11)–Os(3)–Os(1) 84.8(2), C(10)–Os(2)–Os(1) 77.29(19), C(11)–Os(3)–Os(2) 55.4(2), C(11)–Os(2)–Os(3) 47.8(2), C(11)–Os(2)–Os(1) 84.4(2), C(10)–Os(2)–C(11)
35.4(3), C(1)–Os(1)–Os(3) 115.3(3), C(9)–Os(3)–Os(1) 114.7(3).

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S. Ghosh et al. / Inorganica Chimica Acta 363 (2010) 1611–1614
a toluene solution of Os3(CO)12 and two equivalents of PhPTh2 gave a
complex mixture of five compounds including 1–2 and tris-substi-
tuted [Os3(CO)9(PPhTh2)3] (3) (5%). All three were easily character-
ized by spectroscopic methods, the patterns of their IR spectra
being very similar to those of phosphine-substituted triosmium
clusters [8,9,13–18]. The mass spectra of all three show molecular
ions (m/z 1152 for 1, m/z 1398 for 2, m/z 1644 for 3) together with
ions due to successive loss of all carbonyls, while 1H NMR spectra
showed only aromatic resonances indicating that metalation had
not taken place. The 31P{1H} NMR spectrum of 1 and 3 both consist
only of a singlet, the latter showing that all three phosphines occupy
equivalent sites. In contrast the room temperature 31P{1H} NMR
spectrum of 2 displays two broad singlets in 3:1 intensity ratio. This
is consistent with existence of an interconverting mixture of trans–
trans and cis–trans isomers (cis or trans with respect to the Os–Os
vector, Chart 1) [8,9,16,17]. Nordlander and co-workers have previ-
ously noted a similar mixture of isomers for [Os3(CO)10(PPh2Th)2]
their interconversion being slow on the NMR timescale at À60 °C
and have crystallographically characterized the cis–trans isomer. A
similar conversion of isomers clearly occurs in 2 [8].
Th
Ph
S
H
S
H
Ph
Th
P
P
Os
Os
(CO)3
(CO)3
Os
Os(CO)3
Os
(CO)3
Os(CO)3
(CO)3
4a
4b
Chart 2.
two doublets at d À17.89 and À18.20 (J = 15.2 Hz) for 4, while
two doublets of doublets at d À17.22 and À17.42 (J = 15.6,
10.8 Hz) are seen for 5. This isomerism is almost certainly a result
of the different orientations of the phenyl and thienyl groups with
respect to the osmium triangle. Thus in the crystal structure of 4
the phenyl group is orientated on the same side of the molecule
as the metalated thienyl ligand (4a), while a second orientation
is also possible (4b) (Chart 2). On the basis on the NMR data dis-
cussed above we cannot discern which isomer is which and simply
suggest that it is likely that the most abundant isomer in solution is
that seen in the X-ray structure. Similar isomers are also observed
for 5 and the disorder noted in the X-ray structure is presumably a
result of the co-crystallization of these.
3.2. Carbon–hydrogen bond activation of a coordinated PPhTh2 ligand
Heating
1 and 2 in refluxing octane affords [Os3(CO)9
{
{
l
l
3-PPhTh(C4H2S)}(
l
-H)] (4) (37%) and [Os3(CO)8(PhPTh2)
-H)] (5) (55%), respectively (Scheme 1) both
Acknowledgement
3-PPhTh(C4H2S)}(
l
resulting from activation of a carbon–hydrogen bond of a coordi-
nated PPhTh2 ligand. Likewise, heating 3 under similar conditions
gave 5 (36%).
Financial support of this work by the University Grants Com-
mission of Bangladesh is gratefully acknowledged.
The precise nature of this process was confirmed via a single
crystal X-ray diffraction (Fig. 1) of 4. The molecule contains a trian-
gular core of osmium atoms with three distinctly different metal–
metal bonds [Os(1)–Os(2) 2.8689(6), Os(1)–Os(3) 3.0171(6) and
Appendix A. Supplementary material
CCDC 753392 contains the supplementary crystallographic data
for 4. These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif. Supplementary data associated with this article can
be found, in the online version, at doi:10.1016/j.ica.2010.01.030.
Os(2)–Os(3) 2.7701(5) Å] ligated by nine carbonyls,
PPhTh(C4H2S) ligand and a bridging hydride. The 3-PPhTh(C4H2S)
ligand is axially coordinated to Os(1) through the phosphorus
atom, to Os(3) through a Os–C -bond [Os(3)–C(11) 2.110(9) Å]
and to Os(2) through an g2
)-interaction between C(10), C(11)
and Os(2) [Os(2)–C(10) 2.341(8) and Os(2)–C(11) 2.343(9) Å], thus
producing a -vinyl type bridge between Os(2) and Os(3). As a
a l3-
l
r
(p
References
r,p
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Trans. (1999) 1153.
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result the thienyl ring is tilted towards Os(2). This type of coordi-
nation mode of the thienyl moiety is also observed in the related
clusters [Ru3(CO)9{
l3-PPh2(C4H2S)}(
l
-H)] [6], [Os3(CO)9{l3
-
PPh2(C4H2S)}( -H)] [8] and [Os3(CO)9{
l
l
3-PTh2(C4H2S)}( -H)] [9].
l
The hydride ligand is not located in the structural analysis, but
from the lengthening of the Os(1)–Os(3) edge compared to the
other two edges of the cluster (vide supra) and spread out of the
Os–Os–CO angles along this edge [C(1)–Os(1)–Os(3) 115.3(3),
C(9)–Os(3)–Os(1) 114.7(3)°] we speculate that the hydride span
across this Os(1)–Os(3) edge. This assumption is also akin to the
observation that the hydride bridges the metalated edge in related
clusters [6,8,9]. We also undertook a solid-state investigation of
compound 5, and partially determined its molecular structure
[19]. The refinement of this structure is poor due to severe disorder
associated with the phenyl and thienyl rings which precludes dis-
cussion of the structural details. However, the structure gives suf-
ficient information about the geometry of the cluster and the
orientation of the ligands on the cluster surface. Cluster 5 differs
from 4 only in the substitution of a carbonyl by a PPhTh2 ligand,
which occupies an equatorial coordination site on Os(2).
[9] M.A. Mottalib, S.E. Kabir, D.A. Tocher, A.J. Deeming, E. Nordlander, J.
Organomet. Chem. 692 (2007) 5007.
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[15] M.I. Bruce, M.L. Williams, B.K. Nicholson, J. Organomet. Chem. 258 (1983) 63.
[16] R.F. Alex, R.K. Pomeroy, Organometallics 6 (1987) 2437.
[17] A.J. Deeming, S. Donovan-Mtunzi, S.E. Kabir, P.J. Maning, J. Chem. Soc., Dalton
Trans. (1985) 1037.
In solution both 4 and 5 exist in two isomeric forms. Thus, the
31P{1H} NMR spectrum of 4 displays two singlets at d À21.8 and
À17.9 (relative intensity 2.5:1), while 5 shows four singlets at d
À21.5, À18.5, À17.6 and À11.5 in 7:1:7:1 intensity ratio. Consis-
tent with this, the hydride region of the 1H NMR spectra display
[18] M.I. Bruce, M.J. liddell, C.A. Hughes, J.M. Patrick, B.W. Skelton, A.H. White, J.
Organomet. Chem. 347 (1988) 181.
[19] Crystallographic data of 5: space group P212121, with a = 12.5603 Å,
b = 15.0321 Å, c = 20.1179 Å,
a = 90°, b = 90°, c = 90°, Os(1)–Os(2) 2.7775,
Os(1)–Os(3) 2.8592, Os(2)–Os(3) 3.0182, Os(2)–P(2) 2.3204, Os(3)–P(1)
2.3476 Å.