Preparation of osmium η5-phospholide complexes and their reactions with acyl electrophiles: C=o bond cleavage and C-C bond formation within the metal coordination sphere

Article abstract of DOI:10.1021/om101060n

Two diphosphaosmocene species have been pre pared in excellent yields by the reaction of a lithium 2,5-dialkylphospholide (alkyl = cyclohexyl, (-)-menthyl) and [(η⁶-cymene)OsCl₂]₂ in THF. These are the first examples of phosphametallocenes with an osmium core. For the success of the phosphaosmocene synthesis, the use of a sterically demanding phospholide is crucial. A treatment of the 2,2′,5,5′- Cy₄-diphosphaosmocene with an AcCl/AlCl₃ mixture in dichloromethane gives a novel (μ-vinylidene)osmium complex via activation of the acetyl C=O double bond. In the osmium complex, a μ-vinylidene moiety bridges between the osmium atom and a phosphorus of the η⁴-(P- oxophospholide). In the presence of excess acetyl electrophile, the μ-vinylidene complex is subjected to further acetylation at the CH ₂ terminus of the μ-vinylidene moiety to give a (μ-acetylvinylidene)osmium complex. A stepwise application of acetyl chloride and phenylacetyl chloride to this transformation enabled production of a [μ-(phenylacetyl)vinylidene]osmium species by C-C bond formation between the two different acyl chlorides.

Full text of DOI:10.1021/om101060n

ARTICLE
pubs.acs.org/Organometallics
Preparation of Osmium η5-Phospholide Complexes and Their
Reactions with Acyl Electrophiles: CdO Bond Cleavage and
C-C Bond Formation within the Metal Coordination Sphere
Masamichi Ogasawara,*,† Minoru Shintani,† Susumu Watanabe,† Takeshi Sakamoto,† Kiyohiko Nakajima,‡
and Tamotsu Takahashi*,†
†Catalysis Research Center and Graduate School of Life Science, Hokkaido University, Kita-ku, Sapporo 001-0021, Japan
‡Department of Chemistry, Aichi University of Education, Igaya, Kariya, Aichi, 448-8542, Japan
S Supporting Information
b
ABSTRACT: Two diphosphaosmocene species have been pre-
pared in excellent yields by the reaction of a lithium 2,5-
dialkylphospholide (alkyl = cyclohexyl, (-)-menthyl) and
[(η6-cymene)OsCl2]2 in THF. These are the first examples of
phosphametallocenes with an osmium core. For the success of
the phosphaosmocene synthesis, the use of a sterically demanding phospholide is crucial. A treatment of the 2,20,5,50-Cy4-
diphosphaosmocene with an AcCl/AlCl3 mixture in dichloromethane gives a novel (μ-vinylidene)osmium complex via activation of
the acetyl CdO double bond. In the osmium complex, a μ-vinylidene moiety bridges between the osmium atom and a phosphorus
of the η4-(P-oxophospholide). In the presence of excess acetyl electrophile, the μ-vinylidene complex is subjected to further
acetylation at the CH2 terminus of the μ-vinylidene moiety to give a (μ-acetylvinylidene)osmium complex. A stepwise application of
acetyl chloride and phenylacetyl chloride to this transformation enabled production of a [μ-(phenylacetyl)vinylidene]osmium
species by C-C bond formation between the two different acyl chlorides.
’ INTRODUCTION
we became interested in the reactivity of osmium analogues. In
this article, we report the preparation and characterization of the
first (η5-phospholyl)osmium(II) complexes and their reactions
with acyl chlorides. The phosphaosmocene obtained in this study
reacts with 2 equiv of acyl electrophiles in a stepwise fashion to
give a μ-acylvinylidene complex via an initial CdO double-bond
cleavage followed by C-C bond formation within the osmium
coordination sphere.
Since the discoveries of a series of phosphametallocenes in the
late 1970s (phosphacymantrene in 1976;1 mono-2 and diphos-
phaferrecenes3 in 1977 and 1978, respectively), it has been
demonstrated that phospholide anions (phosphacyclopentadie-
nides; phospholyls) are capable of coordinating to various metal
cations, which include diverse transition metals as well as main-
group elements, in an η5 fashion.4 Among such phosphametal-
locene species, those with a central iron(II) cation (phospha-
ferrocenes) have been the most extensively investigated by far.
Heavier homologues of the group 8 triad, however, have received
little attention. Phospharuthenocenes are relatively newer entries
to this field: the first mono-5 and diphospharuthenocenes6 were
reported in 1994 and 2002, respectively.7 To the best of our
knowledge, none of such complexes with an osmium core have
been described to date.8,9
During our investigations of the diphospharuthenocene com-
plexes, we disclosed an unprecedented reaction mode of phos-
phametallocenes.10 A reaction between the Cy4-diphospharuthe-
nocene 1 and an acyl electrophile produced the μ-vinylidene
species 2, where the vinylidene moiety bridges the Ru center and
the phosphorus atom, via activation of the acyl CdO double
bond (Scheme 1, top). The homologous Cy4-diphosphaferro-
cene 4 afforded the conventional Friedel-Crafts acylation
product 5 under identical conditions (Scheme 1, bottom). Due
to the striking differences between the iron(II) and the rut-
henium(II) complexes in the reactions with acetyl electrophile,
’ RESULTS AND DISCUSSION
Preparation of Diphosphaosmocenes. Preparation of a yet
unknown diphosphaosmocene complex is examined. As an initial
trial, the conditions reported for preparation of the analogous
diphospharuthenocenes6 are studied. The reaction of polymeric
[OsCl2(cod)]n11 and lithium 2,5-dicyclohexylphospholide (7a; 2
equiv with respect to Os), which is generated in situ from the
corresponding phosphole 6a and lithium metal, in THF leads to
formation of the 1,10-biphospholyl 8 as a major product (∼60%
determined by 31P NMR) by oxidative homocoupling of the
phospholide (Scheme 2, top).12 The expected diphosphaosmo-
cene is not detected in the 1H and 31P NMR spectra or by LRMS
analysis. It is found that the use of the dimeric dichloroosmium
complex [(η6-cymene)OsCl2]2,13 which is soluble in THF, in the
Received: November 11, 2010
Published: February 21, 2011
r
2011 American Chemical Society
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Scheme 1. Reactions of Diphospharuthenocene 1 and Diphosphaferrocene 4 with Acetyl Electrophile
Scheme 2. Synthesis of Diphosphaosmocenes 9a,b
Figure 1. ORTEP drawing of 9a with thermal ellipsoids at the 30%
probability level. All hydrogen atoms are omitted for clarity. Selected
bond lengths (Å) and angles (deg): P(1)-C(1) = 1.793(2), P(1)-
C(4) = 1.784(3), C(1)-C(2) = 1.417(4), C(2)-C(3) = 1.429(4),
C(3)-C(4) = 1.417(3), Os(1)-phospholyl = 1.819(4); C(1)-P(1)-
C(4) = 90.2(1), P(1)-C(1)-C(2) = 111.9(2), C(1)-C(2)-C(3) =
112.6(2), C(2)-C(3)-C(4) = 113.3(2), P(1)-C(4)-C(3) =
111.9(2).
reaction with the phospholide 7a affords the desired dipho-
sphaosmocene 9a cleanly in 84% isolated yield (Scheme 2,
bottom). The diphosphaosmocene 9a is a slightly air-sensitive
colorless solid and can be purified by silica gel chromatography or
sublimation under high vacuum. The method of diphosphaos-
mocene synthesis is highly sensitive to substituents on phospho-
lide anions. While the diphosphaosmocenes 9a,b are obtained in
good yields using phospholides with bulky R substituents (7a,b),
attempts to prepare analogous diphosphaosmocenes using steri-
cally more compact phospholides, such as 7c,d, were unsuccess-
ful in giving complex mixtures. Apparently, steric protection of
the nucleophilic phosphorus atoms in 7a,b is the key to success in
the preparation of 9a,b.
Characterization of Diphosphaosmocenes. Prismatic crys-
tals of 9a suitable for X-ray analysis were grown by slow cooling
of the hot octane solution. The crystal structure is shown in
Figure 1 with selected bond lengths and angles, which confirms
the η5 coordination of the phospholyl ligand to the osmium(II)
core (see the Supporting Information for details). The crystal
structures of the homologous 2,20,5,50-tetracyclohexyl-1,10-di-
phosphaferrocene 4 and -ruthenocene 1 were reported previ-
ously.6 All three complexes are almost isostructural. The osmium
atom in 9a is located at the center of symmetry, and the two
phospholyl rings are parallel and attain a staggered conforma-
tion. The nearly planar phospholyl ligands are slightly distorted,
and the phosphorus atom lies out of the C(1)C(2)C(3)C(4)
plane by 0.047 Å away from the central osmium atom. The
distance between a least-squares plane of the phospholyl ligand
and the metal center is 1.819(4) Å in 9a; this value is similar
to that in 1 (1.811(2) Å) and is ca. 9% longer than that in 4
(1.671(3) Å).6
The 1H and 13C NMR characteristics of 9a are similar to those
of 1 and 4. A resonance for the β-phospholyl hydrogens is
detected at δ 5.28 as a doublet with a small JPH value (4.7 Hz) in
the 1H NMR spectrum. The R-phospholyl and the β-phospholyl
carbons show doublets at δ 101.6 (JPC = 65.3 Hz) and 75.2 (JPC
=
5.8 Hz), respectively, in the 13C{1H} NMR spectrum. The
31P{1H} NMR spectrum shows a sharp singlet at δ -70.0, which
is at higher field compared to those of 1 and 4.6
Although the diphosphaosmocene 9b is not crystalline, the
η5 coordination (not η1 coordination) of the 2,5-bis[(-)-
menthyl]phospholides in 9b is confirmed by its NMR spectra.
The C2 symmetry of the free phospholide, which has two chiral
(-)-menthyl substituents, is broken by the η5 coordination to
the Os(II) center. Thus, the two β-hydrogens of an η5-phos-
pholyl in 9b are inequivalent with each other and give two
resonances at δ 5.30 and 5.58 in the 1H NMR spectrum.
Likewise, the 13C NMR spectrum of 9b shows two CR signals
with large 1JPC couplings at δ 100.1 (JPC = 66.1 Hz) and 103.0
1
(JPC = 66.9 Hz) as well as two Cβ signals with small JPC
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Scheme 3. Reactions of Diphosphaosmocene 9a with Acetyl Electrophile
and the nonbonding distance between Os(1) and the oxidized
phosphorus P(1) is 2.654(2) Å. The dihedral angle between
the P(1)C(3)C(6) plane and the C(3)C(4)C(5)C(6) plane is
18.17°, and P(1) lies out of the C(3)C(4)C(5)C(6) plane by
0.400 Å away from Os(1). The vinylidene moiety C(1)dC-
(2)H(1)H(2) bridges between Os(1) and P(1). The C(2)C-
(1)P(1)Os(1) plane is nearly perpendicular to the η4-C(3)-
C(4)C(5)C(6) plane (89.08°), which makes the two hydrogens
at the vinylidene terminus inequivalent with each other.
The C(1)-C(2) bond length is 1.317(9) Å, which is within
the normal range for typical CdC double bonds. Analogous
η4 coordination of a P-oxophospholide was described in an
iron complex.14
With free rotation of the η5-phospholyl ligand about the
Os(1)-phospholyl axis, the complex 10 is Cs symmetric in
1
solution and the H, 13C, and 31P NMR spectra are consistent
with the solid-state structure. The complex 10 shows two signals
of equal intensities at δ -53.6 and -17.9 in the 31P NMR
spectrum. The two hydrogen nuclei of the μ-vinylidene moiety in
10 are detected as two doublets at δ 5.66 (JPH = 65.8 Hz) and
6.70 (JPH = 37.7 Hz) in the 1H NMR spectrum. The former, with
the larger JPH value, is assigned to a signal of H(2) that is trans to
P(1) and the latter to that of H(1).
While a reaction of the diphospharuthenocene 1 with AcCl/
AlCl3 gives the Friedel-Crafts acetylation product 3 as a minor
product together with 2 (Scheme 1, top), the reaction of 9a does
not afford the comparable acetyl compound 11. These observa-
tions are consistent with the reported reactivity of Cp2Ru and
Cp2Os: the parent osmocene is less reactive than the parent
ruthenocene toward electrophilic substitutions and tends to give
Friedel-Crafts acylation products in lower yields.15 The rela-
tively low yield of 10 is not improved, even with a large excess of
acetyl electrophile and longer reaction time. The reaction of 9a
with AcCl/AlCl3 (10 equiv to 9a) for 72 h in refluxing dichlor-
omethane affords the previously undetected osmium complex 12
in 45% yield together with several uncharacterized side products.
Although the unreacted 9a is recovered in 12% yield, the
μ-vinylidene species 10 is not found among the minor products
under these conditions (Scheme3).
Figure 2. ORTEP drawing of 10 with thermal ellipsoids at the 30%
probability level. All hydrogen atoms, except H(1) and H(2), are
omitted for clarity. Selected bond lengths (Å) and angles (deg):
Os(1)-P(1) (nonbonding) = 2.654(2), Os(1)-P(2) = 2.440(2), Os-
(1)-C(1) = 2.159(6), P(1)-C(1) = 1.738(4), P(1)-O(1) = 1.480(5),
C(1)-C(2) = 1.317(9); Os(1)-C(1)-P(1) = 85.1(2), C(3)-P(1)-
C(6) = 90.1(2), Os(1)-C(1)-C(2) = 140.6(4), P(1)-C(1)-C(2) =
134.3(5).
couplings at δ 74.6 (JPC = 4.8 Hz) and 79.9 (JPC = 5.3 Hz). The
31P NMR spectrum of 9b shows a broad signal at 23 °C, which is
sharpened at higher temperature. The variable-temperature
NMR behavior of 9b can be attributed to restricted rotation
of the η5-bis(menthyl)phospholides about the phospholyl-
Os-phospholyl axis, as observed in the homologous tetrakis-
(menthyl)diphosphaferrocene and tetrakis(menthyl)diphos-
pharuthenocene.7b
Reactions of Diphosphaosmocene 9a with Acetyl Chlor-
ide/AlCl3. Treatment of the diphosphaosmocene 9a with 2
equiv of an acetyl electrophile, which is generated from equimo-
lar CH3COCl and AlCl3, in dichloromethane at room tempera-
ture for 36 h gave the off-white crystalline product 10 in 40%
yield together with recovered 1 in 48% yield (Scheme 3). The
product 10 is air and moisture stable and was easily purified
by conventional silica gel column chromatography. Prismatic
crystals of 10 were grown from the hot ethyl acetate solution,
and X-ray crystallography reveals the identity of 10 as being
a μ-vinylidene complex, as for the ruthenium analogue 2
(Figure 2).10 One of the two phospholyl ligands in 10 coordi-
nates to Os(1) in an η4 fashion at the C(3)C(4)C(5)C(6) core,
The complex 12 is isolated as an off-white crystalline solid by
silica gel chromatography, and its X-ray crystal structure is shown
in Figure 3. The μ-vinylidene moiety is acetylated at C(2) in 12,
and the acetyl group takes a position trans to Os(1). Due to
conjugation between the C(1)dC(2) and the C(3)dO(2)
double bonds, the C(1)-C(2) bond length is slightly longer
(1.335(7) Å) compared to that of the CdC vinylidene in 10. The
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overall structure of 12 is, however, very similar to that of 10. The
complex 12 is insensitive to both oxygen and moisture and can be
handled under air without appreciable decomposition. The 31P
NMR spectrum of 12 shows two signals of equal intensities at
δ -44.8 and -18.3. The vinylidene hydrogen H(1) is detected at
δ 6.77 in the 1H NMR spectrum with a strong coupling with P(1)
(JPH = 58.0 Hz), which is consistent with the E configuration
(with respect to the C(1)dC(2) double bond) shown by the
X-ray structure analysis.
Reactions of the Os μ-Vinylidene Complex 10 with Acyl
Chloride/AlCl3. Whereas the formation of 12 is assumed to take
place by way of 10, a reaction between the isolated 10 and the
acetyl electrophile (AcCl/AlCl3) should be examined. As ex-
pected, treatment of 10 with AcCl/AlCl3 (2 equiv with respect to
10) in refluxing dichloromethane for 24 h cleanly converts 10
into 12, and the Ac-vinylidene complex 12 is obtained in a nearly
quantitative yield (Scheme 4, top). The vinylidene moiety in 10
can be acylated using acylium reagents other than AcCl/AlCl3:
i.e., the reaction of 10 with phenylacetyl chloride under condi-
tions otherwise identical with those above provides the
[μ-(phenylacetyl)vinylidene]osmium complex 13 in 78% yield.
The reaction is somewhat slower in the latter case, and the
unreacted 10 is recovered in 20% yield (Scheme 4, bottom).
Complex 13 is obtained as a single isomer exclusively, and its
configuration is determined as E on the basis of the large coupling
constant between the bridged phosphorus and the alkenylidene
hydrogen (JPH = 57.7 Hz).
A possible mechanism for the formation of the μ-(acetyl-
vinylidene) complex 12 is shown in Scheme 5. Because osmium
tends to take a higher oxidation state compared to ruthenium, a
resonance structure such as 100, in which the formal oxidation
state of Os is þ4, contributes to the reactivity of 10 to a certain
extent. As a consequence, the terminal vinylidene carbon in 10
becomes nucleophilic. An electrophilic attack of the acetylium
species at the vinylidene carbon followed by a nucleophilic
abstraction of one of the hydrogens in the Ac-CH2- moiety
by the AlCl4- anion affords the μ-(acetylvinylidene) complex 12.
The cationic charge in the intermediate 14 is stabilized by
the Os4þ center. The overall process of converting 10 into 12
(or 13) can be regarded as an olefinic electrophilic substitu-
tion (Friedel-Crafts-type acylation).16 It was reported that
electrophilic acylation of enamines17 and ketene dithioacetals
(and related compounds)18 took place in a similar fashion, in
which cationic intermediates were stabilized by the heteroatom
substituents.
Figure 3. ORTEP drawing of 12 with 30% thermal ellipsoids. All
hydrogen atoms except H(1) are omitted for clarity. Selected bond
lengths (Å) and angles (deg): Os(1)-P(1) (nonbonding) = 2.660(1),
Os(1)-P(2) = 2.450(1), Os(1)-C(1) = 2.125(5), P(1)-C(1) =
1.780(5), P(1)-O(1) = 1.484(4), C(1)-C(2) = 1.335(7), C(2)-
C(3) = 1.490(8), C(3)-O(2) = 1.201(7); Os(1)-C(1)-P(1) =
85.4(2), C(5)-P(1)-C(8) = 90.0(2), Os(1)-C(1)-C(2) =
136.1(4), P(1)-C(1)-C(2) = 138.1(4), C(1)-C(2)-C(3) =
128.2(5).
Scheme 4. Reactions of μ-Vinylidene Osmium Complex 10
with Acyl Electrophiles
The transformation of 9a into 12 involves CdO bond
cleavage and C-C coupling within the osmium coordination
sphere, and two molecules of acetyl electrophile play different
roles during the transformation. When the first acetyl electro-
phile reacts with 9a at the osmium center, the polarity of the C2
Scheme 5. Possible Reaction Pathway of Formation of 12 from 10 and AcCl/AlCl3
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moiety is reversed to nucleophilic via reductive CdO cleavage by
the phospholyl ligand to give 10 in the same way as for the
analogous ruthenium complex 1.10 Subsequently, the second
acetyl electrophile attacks the vinylidene CH2 terminus in 10
to furnish the β-acetylvinylidene complex 12, as shown in
Scheme 5.
(d, JPC = 7.4 Hz), 22.0, 22.1, 23.06, 23.07, 26.1, 26.3, 28.4 (2C), 34.68,
34.71, 36.1, 36.3, 41.7 (d, JPC = 15.8 Hz), 44.3 (d, JPC = 11.8 Hz), 46.4
(t, JPC = 4.2 Hz), 48.5 (dd, JPC = 6.6 and 5.5 Hz), 51.4, 53.7, 74.6 (d, JPC
4.8 Hz), 79.9 (d, JPC = 5.3 Hz), 100.1 (d, JPC = 66.1 Hz), 103.0 (d, JPC
=
=
=
66.9 Hz). 31P{1H} NMR (toluene-d8, 80 °C): δ -59.3. [R]25.3
D
-213° (c 1.65, CHCl3). Anal. Calcd for C48H80OsP2: C, 63.40; H, 8.87.
Found: C, 63.45; H, 9.02. EI-HRMS: m/z calcd for C48H80OsP2
910.5350, found 910.5366.
’ CONCLUSIONS
Reactions of Phosphaosmocenes with Acyl Electrophiles.
A typical procedure is given for the reaction of the diphosphaosmocene
9a with 2 equiv of AcCl/AlCl3. To a suspension of AlCl3 (209 mg, 1.57
mmol) in dichloromethane (15 mL) was added acetyl chloride (127 mg,
1.62 mmol) at room temperature. The mixture was stirred at this
temperature for 1 h and was then added to a dichloromethane (5 mL)
solution of the diphosphaosmocene 9a (561 mg, 819 μmol). The
mixture was stirred for 36 h at room temperature. The reaction was
quenched by the addition of water (0.5 mL) at 0 °C and then evaporated
to dryness under vacuum. The residue was extracted with dichloro-
methane, and the extract was further purified by silica gel chromatog-
raphy (eluents: chloroform then EtOAc). The μ-vinylidene complex 10
was obtained as a major product (238 mg, 327 μmol, 40%) together with
the recovered 9a (269 mg, 393 μmol, 48%). The characterization data of
the products are given below.
Two novel diphosphaosmocenes have been prepared and
characterized by X-ray crystallography and/or NMR spectrosco-
py. The 2,20,5,50-Cy4-1,10-diphosphaosmocene obtained in this
study reacts with 2 equiv of acyl electrophiles in a stepwise
fashion. The initial step is formation of a (μ-vinylidene)osmium
complex via activation of the acetyl CdO double bond, in which
a μ-vinylidene moiety bridges between the osmium core and a
phosphorus of the η4-(P-oxophospholide). The second step
takes place in the presence of excess acetyl electrophile, and the
μ-vinylidene complex is acetylated at the CH2 terminus of the
μ-vinylidene ligand to give a (μ-acetylvinylidene)osmium com-
plex by C-C bond formation within the metal coordination
sphere.
(η5-2,5-Dicyclohexyl-1-phosphacyclopentadienyl)(2,3,4,5-
η4-2,5-dicyclohexyl-1-oxo-1-phosphacyclopentadienyl)
(μ-vinylidene-Os,P)osmium(II) (10). 1H NMR (CDCl3): δ
1.05-1.38 (m, 22H), 1.56-1.75 (m, 16H), 1.82-1.85 (m, 6H), 5.48
(d, JPH = 14.0 Hz, 2H), 5.51 (d, JPH = 4.0 Hz, 2H), 5.66 (d, JPH = 65.8
Hz, 1H), 6.70 (d, JPH = 37.7 Hz, 1H). 13C NMR (CDCl3): δ 25.88 (s),
25.92 (s), 26.3 (s), 26.55 (s), 26.57 (s), 26.8 (s), 33.6 (d, JPC = 3.6 Hz),
’ EXPERIMENTAL SECTION
General Considerations. All anaerobic and/or moisture-sensi-
tive manipulations were carried out with standard Schlenk techniques
under predried nitrogen or with glovebox techniques under prepurified
argon. 1H NMR (at 400 MHz) and 13C NMR (at 101 MHz) chemical
shifts are reported in ppm downfield of internal tetramethylsilane. 31P
NMR (at 162 MHz) chemical shifts are externally referenced to 85%
H3PO4. Tetrahydrofuran and benzene were distilled from benzophe-
none-ketyl under nitrogen prior to use. Dichloromethane was distilled
from CaH2 under nitrogen prior to use. The phospholes (6a,6 6b,19 6c,20
34.3 (d, JPC = 14.1 Hz), 35.3 (d, JPC = 5.4 Hz), 38.4 (s), 39.0 (d, JPC
12.3 Hz), 40.3 (d, JPC = 8.0 Hz), 78.5 (d, JPC = 18.0 Hz), 84.9 (d, JPC
=
=
73.3 Hz), 93.2 (d, JPC = 5.8 Hz), 110.6 (d, JPC = 68.2 Hz), 118.5 (s),
127.9 (d, JPC = 52.8 Hz). 31P NMR (CDCl3): δ -53.6, -17.9. Anal.
Calcd for C34H50OOsP2: C, 56.18; H, 6.93. Found: C, 55.92; H, 6.92.
EI-HRMS: m/z calcd for C34H50OOsP2 728.2952, found 728.2929.
(η5-2,5-Dicyclohexyl-1-phosphacyclopentadienyl)(2,3,4,5-
η4-2,5-dicyclohexyl-1-oxo-1-phosphacyclopentadienyl)-
(μ-(E)-3-oxo-1-butenylidene-Os,P)osmium(II) (12). 1H NMR
(CDCl3): δ 1.04-1.30 (m, 18H), 1.38-1.84 (m, 26H), 2.72 (s, 3H),
5.60 (d, JPH = 3.9 Hz, 2H), 5.63 (d, JPH = 15.0 Hz, 2H), 6.77 (d, JPH = 58.0
Hz, 1H). 13C NMR (CDCl3): δ 25.7 (s), 25.8 (s), 26.2 (s), 26.4 (s), 26.5
(s), 26.8 (s), 28.7 (s), 32.6 (d, JPC = 3.5 Hz), 34.3 (d, JPC = 14.1 Hz), 36.2
(d, JPC = 3.9 Hz), 38.3 (s), 39.0 (d, JPC = 11.9 Hz), 40.9 (d, JPC = 7.5 Hz),
78.2 (d, JPC = 19.5 Hz), 81.5 (d, JPC = 79.9 Hz), 94.6 (d, JPC = 5.7 Hz),
115.3 (d, JPC = 68.8 Hz), 138.8 (s), 153.3 (d, JPC = 36.6 Hz), 196.7 (d, JPC
= 15.9 Hz). 31P NMR (CDCl3): δ -44.8, -18.3. Anal. Calcd for
C36H52O2OsP2: C, 56.23; H, 6.82. Found: C, 56.19; H, 6.62. EI-HRMS:
m/z calcd for C36H52O2OsP2 770.3057, found 770.3047.
and 6d21), [OsCl2(cod)]n,11 and [(η6-cymene)OsCl2]2 were pre-
pared as reported. All other chemicals were obtained from commercial
sources.
13
Bis(η5-2,5-dicyclohexyl-1-phosphacyclopentadienyl)-
osmium(II) (9a). A THF (20 mL) solution of the phosphole 6a (1.05
g, 3.24 mmol) was treated with lithium metal (300 mg, 43.2 mmol), and
the mixture was stirred overnight at room temperature. The mixture was
filtered through a glass filter, and to the filtrate was added anhydrous
AlCl3 (145 mg, 1.09 mmol) at 0 °C.22 After the mixture was warmed to
room temperature, a THF (5 mL) solution of [(η6-cymene)OsCl2]2
(600 mg, 1.52 mmol/Os) was added, and then the mixture was refluxed
for 24 h. After the mixture was cooled, all the volatiles were removed
under reduced pressure. The residue was purified by silica gel chroma-
tography (elution with hexane) to give the title compound in pure form.
Alternatively, the compound could be recrystallized from hot octane.
1
Yield: 873 mg (84%). H NMR (CDCl3): δ 1.06-1.26 (m, 20H),
(η5-2,5-Dicyclohexyl-1-phosphacyclopentadienyl)(2,3,4,5-
η4-2,5-dicyclohexyl-1-oxo-1-phosphacyclopentadienyl)-
(μ-(E)-3-oxo-4-phenyl-1-butenylidene-Os,P)osmium(II) (13). 1H
NMR (CDCl3): δ 1.01-1.80 (m, 44H), 4.54 (s, 2H), 5.58 (d, JPH = 3.7 Hz,
2H), 5.62 (d, JPH = 15.1 Hz, 2H), 6.83 (d, JPH = 57.7 Hz, 1H), 7.16-7.20 (m,
1H), 7.25-7.30 (m, 2H), 7.35-7.37 (m, 2H). 13C NMR (CDCl3): δ 25.6
(s), 25.7 (s), 26.2 (s), 26.4 (s), 26.5 (s), 26.7 (s), 32.9 (d, JPC = 3.3 Hz), 34.3
(d, JPC = 13.9 Hz), 35.9 (d, JPC = 4.8 Hz), 38.2 (s), 39.0 (d, JPC = 12.0 Hz),
40.5 (d, JPC = 8.1 Hz), 45.4 (s), 78.2 (d, JPC = 20.2 Hz), 81.7 (d, JPC = 79.5
Hz), 94.4 (d, JPC = 5.7 Hz), 115.2 (d, JPC = 68.6 Hz), 126.1, (s), 128.1 (s),
129.7 (s), 136.2 (s), 138.2 (s), 152.9 (d, JPC = 38.3 Hz), 195.2 (d, JPC = 15.3
Hz). 31PNMR(CDCl3):δ-44.5, -17.7. Anal. Calcd for C42H56O2OsP2:C,
59.69; H, 6.68. Found: C, 58.99; H, 6.83. EI-HRMS: m/z calcd for
C42H57O2OsP2 (M þ H) 847.3449, found 847.3440.
1.60-1.63 (m, 4H), 1.68-1.84 (m, 20H), 5.28 (d, JPH = 4.7 Hz,
4H). 13C{1H} NMR (CDCl3): δ 26.5 (s), 27.0 (s), 27.1 (s), 36.9
(d, JPC = 8.8 Hz), 37.1 (d, JPC = 4.4 Hz), 40.7 (d, JPC = 13.7 Hz), 75.2
(d, JPC = 5.8 Hz), 101.6 (d, JPC = 65.3 Hz). 31P{1H} NMR (CDCl3):
δ -70.0 (s). Anal. Calcd for C32H48OsP2: C, 56.12; H, 7.06. Found: C,
55.98; H, 7.09. EI-HRMS: m/z calcd for C32H48OsP2 686.2846, found
686.2845.
Bis[η5-2,5-bis((-)-menthyl)-1-phosphacyclopentadienyl]-
osmium(II) (9b). The compound was prepared in the same way as
described above and purified by silica gel chromatography (elution with
1
hexane). Yield: 96%. H NMR (toluene-d8, 80 °C): δ 0.80-1.29 (m,
56H), 1.58-1.83 (m, 14H), 2.06-2.09 (m, 2H), 2.17-2.25 (m, 2H),
2.35-2.42 (m, 2H), 5.30 (dd, JPH = 4.3 and 2.6 Hz, 2H), 5.58 (dd, JPH
=
4.9 and 2.5 Hz, 2H). 13C{1H} NMR (toluene-d8, 80 °C): δ 16.4, 16.6
1491
dx.doi.org/10.1021/om101060n |Organometallics 2011, 30, 1487–1492

Organometallics
ARTICLE
’ ASSOCIATED CONTENT
(12) Analogous oxidative homocoupling of phospholide anions
was reported using phosgene or iodine as an oxidizing agent; see:
(a) Charrier, C.; Bonnard, H.; Mathey, F.; Neibecker, D. J. Organomet.
Chem. 1982, 231, 361. (b) Holand, S.; Mathey, F.; Fischer, J.; Mitschler,
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(13) (a) Werner, H.; Zenkert, K. J. Organomet. Chem. 1988, 345,
151. (b) Castarlenas, R.; Esteruelas, M. A.; O~nate, E. Organometallics
2005, 24, 4343.
Supporting Information. Figures giving 1H, 13C, and 31
P
S
b
NMR spectra for all new compounds and CIF file giving crystal-
lographic data for 9a, 10, and 12. This material is available free of
charge via the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION
(14) Deschamps, B.; Fischer, J.; Mathey, F.; Mitschler, A. Inorg.
Chem. 1981, 20, 3252.
(15) Rausch, M. D.; Fischer, E. O.; Grubert, H. J. Am. Chem. Soc.
1960, 82, 76.
Corresponding Author
*To whom correspondence should be addressed. E-mail: ogasawar@
cat.hokudai.ac.jp (M.O.).
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’ ACKNOWLEDGMENT
This work was supported by a Grant-in-Aid for Scientific
Research on Priority Areas “Synergistic Effects for Creation of
Functional Molecules” from the Ministry of Education, Culture,
Sports, Science and Technology of Japan. S.W. has been a
recipient of the JSPS Research Fellowship for the Young
Scientists.
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