Coupling reactions of an allenylcarbene complex with alkynes and styrene

Article abstract of DOI:10.1002/ejic.200601251

The allenylcarbene complex [OsCl₂{=CPh(η²-CH=C= CHPh)}(PPh₃)₂] undergoes coupling reactions with HC≡CSiMe₃ and PhC≡CC≡CPh to produce the fulvene complexes [OsCl₂{η⁶-C₅H₂(Ph) (SiMe₃)(=CHPh)}(PPh₃)] and [OsCl₂{η ⁶-C₅H(Ph)₂(C≡CPh)(=CHPh)}(PPh ₃)], respectively. A similar coupling reaction also occurs between [OsCl₂{=CPh(η²-CH=C=CHPh)}(PPh₃) ₂] and styrene. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.

Full text of DOI:10.1002/ejic.200601251

FULL PAPER
DOI: 10.1002/ejic.200601251
Coupling Reactions of an Allenylcarbene Complex with Alkynes and Styrene
Ting Bin Wen,[a] Wai Yiu Hung,[a] Herman H.-Y. Sung,[a] Zhongyuan Zhou,[b]
Ian D. Williams,[a] and Guochen Jia*[a]
Keywords: Osmium / Fulvenes / Carbenes / Alkynes / Alkenes
The allenylcarbene complex [OsCl2{=CPh(η2-CH=C=
CHPh)}(PPh3)2] undergoes coupling reactions with
HCϵCSiMe3 and PhCϵCCϵCPh to produce the fulvene
complexes [OsCl2{η6-C5H2(Ph)(SiMe3)(=CHPh)}(PPh3)] and
[OsCl2{η6-C5H(Ph)2(CϵCPh)(=CHPh)}(PPh3)], respectively. A
similar
coupling
reaction
also
occurs
between
[OsCl2{=CPh(η2-CH=C=CHPh)}(PPh3)2] and styrene.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2007)
coupling of the vinylidene ligand and the metallacyclopen-
tadiene ring (Scheme 1, path a). Reactions of preformed iri-
diacyclopentadiene compounds with terminal alkynes have
been shown to produce fulvene complexes.[5] In the reaction
involving a base (Scheme 1, path b), for example the tita-
nium aryloxide/LiCϵCtBu-catalyzed cyclotrimerization of
tert-butylacetylene, a metallacyclopentadiene-acetylide in-
termediate has been proposed. This intermediate undergoes
reductive coupling followed by an insertion to give the ful-
venyl complex, which reacts with alkyne to give fulvene and
regenerate the metallacyclopentadiene-acetylide intermedi-
ate.[7] In principle, fulvenes could also be formed via metall-
acyclobutene intermediates (Scheme 1, path c). This reac-
tion has been proposed for the formation of a fulvene com-
plex from the reaction of [RhCl(COD)]2 (COD = cycloocta-
1,5-diene) with HCϵCtBu in the presence of AgPF6.[4] In
this regard, it would be interesting to demonstrate that pre-
formed metallacyclobutene complexes could react with al-
kynes to give fulvene complexes.
Introduction
The [2+2+2] cyclotrimerization of alkynes to give six-
membered aromatic rings is one of the most common reac-
tions promoted by transition metal complexes and has been
utilized in the synthesis of many useful natural products
and novel organic materials.[1–3] In sharp contrast, examples
of metal-mediated [2+2+1] cyclotrimerization of alkynes to
give thermodynamically less stable isomeric fulvene deriva-
tives are limited to only a few scattered reports.
The stoichiometric formation of fulvene metal complexes
from formal [2+2+1] cyclotrimerizations of alkynes has
been reported for the reaction of rhodium,[4] iridium,[5] and
palladium[6] complexes with alkynes. Reported catalytic
cyclotrimerization reactions of alkynes to give fulvenes in-
clude the titanium aryloxide/LiCϵCtBu-catalyzed cyclo-
trimerization of tert-butylacetylene[7] and the [(η3-C3H5)-
PdCl]2/dppf-catalyzed cyclotrimerization of aliphatic al-
kynes.[8] Fulvene or fulvenyl intermediates may also be in-
volved in the reactions of terminal alkynes with transition
metal complexes to give complexes with ligands derived
from the oligomerization of alkynes.[9–15]
We have recently reported the synthesis of the η2-allenyl-
carbene
complex
[OsCl2{=CPh(η2-CH=C=CHPh)}-
(PPh3)2] (1),[16,17] which can be regarded as an isomer of an
osmacyclobutene, from the reaction of PhCϵCH with
the vinylidene complex [OsCl2(=C=CHPh)(PPh3)2] or
[OsCl2(PPh3)3]. In this work, we will describe its coupling
reactions with alkynes. Its reaction with styrene has also
been investigated for comparison.
There are several possible pathways that can lead to the
formation of fulvenes from the [2+2+1] cyclotrimerization
of alkynes; these are illustrated in Scheme 1. Fulvenes may
be formed via a metallacyclopentadiene route, which in-
volves oxidative coupling of two molecules of alkynes at the
metal to give a metallacyclopentadiene intermediate, isom-
erization of another molecule of alkyne to a vinylidene li-
gand, and reductive cyclization to a fulvene product by Results and Discussion
Coupling Reaction of [OsCl2{=CPh(η2-CH=C=CHPh)}-
(PPh3)2] (1) with Alkynes
[a] Department of Chemistry, The Hong Kong University of Sci-
ence and Technology,
Clear Water Bay, Kowloon, Hong Kong
Fax: +852-2358-1594
Treatment of 1 with HCϵCSiMe3 in dichloromethane
produced the η6-fulvene complex [OsCl2{η6-C5H2(Ph)-
(SiMe3)(=CHPh)}(PPh3)] (2), which was isolated as a green
solid in 81% yield (Scheme 2). The NMR spectroscopic
E-mail: chjiag@ust.hk
[b] Department of Applied Biology & Chemical Technology, The
Hong Kong Polytechnic University,
Hung Hom, Kowloon, Hong Kong
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G. Jia et al.
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Scheme 1.
data (in CD2Cl2) of the isolated solid suggest the presence
The interaction of osmium and the exocyclic double
of two isomers (2a and 2b) in a ratio of 4.5:1 in solution bond in complex 2a is indicated by the inclination of the
(Scheme 2). C(1)–C(6) bond toward osmium, with an angle of 26.9°
The structure of 2a was determined by X-ray diffraction from the fulvene ring plane. The displacement of C(6) from
analysis of a single crystal grown from a CH2Cl2 solution the fulvene ring plane is 0.625 Å. However, this interaction
of 2 layered with hexane. Selected bond lengths and angles is weak, as reflected by the rather long Os–C(6) separation
are shown in Table 1. The structure shown in Figure 1 [2.632(4) Å] and the relatively short exocyclic double bond
clearly reveals that coupling of HCϵCSiMe3 with the allen- [the C(1)–C(6) distance being 1.380(5) Å]. Three extreme
ylcarbene ligand has occurred to give the η6-4,6-diphenyl- canonical forms (see Scheme 3), namely an η6-triene (2), an
2-(trimethylsilyl)fulvene complex 2.
η5-cyclopentadienido-σ-alkyl (“tucked-in”, 2Ј), and a zwit-
Scheme 2.
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Coupling of an Allenylcarbene Complex with Alkynes and Styrene
FULL PAPER
Table 1. Selected bond lengths [Å] and angles [°] for [OsCl2{η6- in an η6-triene fashion. As shown in Table 2, the Os–C-
C5H2(Ph)(SiMe3)(=CHPh=}(PPh3)] (2a).
(exocyclic) bond lengths in the structurally characterized
osmium fulvene complexes [(η5-C5Me5)Os{η6-C5Me4-
Os(1)–C(1)
Os(1)–C(3)
Os(1)–C(5)
Os(1)–Cl(1)
Os(1)–P(1)
C(2)–C(3)
C(4)–C(5)
C(1)–C(6)
C(4)–C(11)
C(1)–Os(1)–P(1) 156.95(10)
C(2)–Os(1)–P(1) 123.38(10)
C(3)–Os(1)–P(1)
C(1)–Os(1)–Cl(1) 110.50(10)
C(2)–Os(1)–Cl(1) 96.06(10)
2.143(3)
2.183(4)
2.184(4)
2.3920(9) Os(1)–Cl(2)
2.3547(9) C(1)–C(2)
1.421(5)
1.417(5)
1.380(5)
1.481(5)
Os(1)–C(2)
Os(1)–C(4)
Os(1)–C(6)
2.182(4)
2.288(3)
2.632(4)
2.3952(9)
1.480(5)
1.429(5)
1.461(5)
1.882(4)
1.449(5)
95.76(9)
(=CPh2)}](PF6),[19]
[(η5-C5Me5)Os{η6-C5Me4(=CH2)}]-
(BPh4),[20] and [(η5-C5Me5)Os{η6-C5Me4(=CHC6F5)}]-
(PF6)[21] are significantly shorter and the exocyclic C–C
bond lengths significantly longer than those in complex 2a,
which is indicative of a “tucked-in” bonding type in these
complexes. As expected, the inclination angles in these com-
plexes are also significantly larger (35.6–41.8°) than that in
2a (26.9°).
C(3)–C(4)
C(1)–C(5)
C(2)–Si(1)
C(6)–C(21)
C(4)–Os(1)–P(1)
C(5)–Os(1)–P(1) 127.21(10)
C(6)–Os(1)–P(1) 170.78(9)
C(4)–Os(1)–Cl(1) 155.96(10)
C(5)–Os(1)–Cl(1) 148.68(10)
The 31P{1H} NMR spectrum of 2 in C6D6 at room tem-
perature displays two singlets at δ = –0.3 (major) and
–7.8 ppm (minor), thereby indicating the presence of two
93.60(10)
C(3)–Os(1)–Cl(1) 118.77(10)
C(1)–Os(1)–Cl(2) 109.88(10)
C(2)–Os(1)–Cl(2) 148.99(10)
C(3)–Os(1)–Cl(2) 152.39(10)
C(6)–Os(1)–Cl(1)
C(4)–Os(1)–Cl(2) 115.23(10)
87.50(10)
1
isomers in solution. In the H NMR spectrum, the major
isomer displays a singlet at δ = 6.51 ppm and two doublets
at δ = 5.00 and 7.83 ppm for the three fulvene protons. The
splitting of the signals at δ = 5.00 and 7.83 ppm is due to
coupling with the 31P nuclei, as suggested by 1H{31P} NMR
C(5)–Os(1)–Cl(2)
C(6)–Os(1)–Cl(2)
P(1)–Os(1)–Cl(2)
C(1)–Os(1)–C(2)
C(3)–C(2)–C(1)
C(5)–C(4)–C(3)
C(6)–C(1)–Os(1)
C(6)–C(1)–C(5)
94.71(11)
88.80(10)
87.55(3)
40.00(13)
104.3(3)
106.4(3)
94.2(2)
P(1)–Os(1)–Cl(1)
83.99(3)
Cl(1)–Os(1)–Cl(2) 88.80(3)
C(5)–C(1)–C(2)
C(2)–C(3)–C(4)
C(4)–C(5)–C(1)
C(6)–C(1)–C(2)
107.9(3)
112.6(3)
108.7(3)
119.6(3)
1
experiments. The H NMR spectrum of the minor isomer
exhibits three singlets in the 1H NMR spectrum at δ = 5.49,
6.31, and 6.80 ppm for the fulvene protons. Fulvene com-
plexes such as [Re(C6F5){(η6-C5Me4(=CH2)}(CO)2][18a,18b]
and [RuCl2(py){(η6-C5Me4(=CPh2)}][22] also exist as two
isomers in solution. This isomerism has been attributed to
the presence of conformational isomers due to restricted
rotation about the metal-fulvene bond. A similar isomerism
can be proposed for 2. Scheme 4 shows three possible con-
formers of 2. On the basis of steric reasons, one would ex-
pect the stability of these three conformers to be in the or-
der 2a Ͼ 2b Ͼ 2c.
122.8(4)
C(1)–C(6)–C(21) 129.8(4)
The two isomers observed in solution by NMR spec-
troscopy can be attributed to 2a and 2b. The major isomer
can be assigned to the conformer revealed by the X-ray
structure (2a), in which the exocyclic double bond is trans
to PPh3. In agreement with the structure, the 1H NMR
spectrum shows two signals at δ = 7.83 (JP,H = 5.8 Hz) and
5.00 ppm (JP,H = 4.0 Hz) assignable to C(6)H and C(5)H,
respectively, and a singlet at δ = 6.51 ppm assignable to
C(3)H. The minor isomer observed in solution may corre-
spond to conformer 2b in which the exocyclic double bond
is cis to PPh3. The three fulvene signals at δ = 5.49, 6.31,
and 6.80 ppm observed for the minor isomer can be as-
signed to C(5)H, C(3)H, and C(6)H, respectively.
Figure 1. Molecular structure of [OsCl2{η6-C5H2(Ph)(SiMe3)-
(=CHPh)}(PPh3)] (2a).
terionic form (2"), can be considered for the fulvene com-
plex.[18] The structural data of 2a suggest that the fulvene
Scheme 5 shows a plausible mechanism for the formation
ligand in 2a can be regarded as being bound to the osmium of 2 from the coupling reaction. Complex 1 could rearrange
Scheme 3.
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Table 2. Principal structural parameters of selected osmium fulvene complexes.
Scheme 4.
to metallacyclobutene A, which undergoes cycloaddition reductive elimination, followed by coordination of the ful-
with HCϵCSiMe3 to give the metallacyclohexadiene inter- vene to osmium and loss of one PPh3 ligand to give 2. A
mediate B or B1. Complex B or B1 could then undergo similar mechanism has been proposed previously.[4,9]
Scheme 5.
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Eur. J. Inorg. Chem. 2007, 2693–2701

Coupling of an Allenylcarbene Complex with Alkynes and Styrene
The reaction of 1 with PhCϵC–CϵCPh produced the Table 3. Selected bond lengths [Å] and angles [°] for [OsCl2{η6-
FULL PAPER
C5H(CϵCPh)(Ph)2(=CHPh)}(PPh3)]·3C6D6 (3·3C6D6).
analogous fulvene complex 3 (Scheme 1), although the reac-
tion is slow in dichloromethane at room temperature. When
a mixture of 1 and PhCϵC–CϵCPh in benzene was re-
fluxed for 1 h, a brown solution containing 3 along with
small amounts of unreacted 1 and an unidentified species
with a 31P chemical shift of δ = –16.0 ppm was produced.
Complex 3 was isolated in 43% yield from the reaction mix-
ture. Attempts to isolate and identify the unknown species
with a 31P chemical shift of δ = –16.0 ppm failed. The struc-
ture of 3 was also confirmed by a single-crystal X-ray dif-
fraction study. A view of the molecular structure is shown
in Figure 2 and selected bond lengths and angles are listed
in Table 3.
Os(1)–C(1)
Os(1)–C(3)
Os(1)–C(5)
2.199(4)
2.287(4)
2.097(4)
Os(1)–C(2)
Os(1)–C(4)
Os(1)–C(6)
2.276(4)
2.188(4)
2.392(4)
2.3840(11)
1.398(6)
1.437(6)
1.445(6)
1.483(6)
1.486(6)
1.190(6)
Os(1)–Cl(1)
Os(1)–P(1)
2.3898(11) Os(1)–Cl(2)
2.3686(12) C(1)–C(2)
C(2)–C(3)
C(4)–C(5)
C(5)–C(6)
C(6)–C(21)
1.462(6)
1.453(6)
1.424(6)
1.461(6)
1.442(6)
C(3)–C(4)
C(1)–C(5)
C(2)–C(11)
C(3)–C(41)
C(31)–C(32)
C(4)–C(31)
C(32)–C(33)
1.444(6)
C(1)–Os(1)–P(1)
C(2)–Os(1)–P(1)
C(3)–Os(1)–P(1)
C(1)–Os(1)–Cl(1)
C(2)–Os(1)–Cl(1)
C(3)–Os(1)–Cl(1)
C(1)–Os(1)–Cl(2)
C(2)–Os(1)–Cl(2)
C(3)–Os(1)–Cl(2)
P(1)–Os(1)–Cl(1)
Cl(1)–Os(1)–Cl(2)
C(2)–C(1)–C(5)
C(4)–C(3)–C(2)
C(1)–C(5)–C(4)
C(6)–C(5)–C(1)
C(5)–C(6)–C(21)
C(31)–C(32)–C(33)
C(31)–C(4)–C(5)
159.92(11)
152.66(11)
117.11(11)
91.24(11)
110.52(11)
147.87(11)
116.47(11)
86.85(11)
90.49(11)
94.06(4)
85.34(4)
109.5(4)
106.8(4)
106.5(4)
121.6(4)
125.3(4)
176.8(5)
125.2(4)
C(4)–Os(1)–P(1)
C(5)–Os(1)–P(1)
C(6)–Os(1)–P(1)
C(4)–Os(1)–Cl(1) 146.74(12)
C(5)–Os(1)–Cl(1) 107.24(12)
102.79(12)
120.96(12)
95.15(11)
C(6)–Os(1)–Cl(1)
85.47(11)
C(4)–Os(1)–Cl(2) 124.62(12)
C(5)–Os(1)–Cl(2) 150.61(12)
C(6)–Os(1)–Cl(2) 170.55(11)
P(1)–Os(1)–Cl(2)
C(5)–Os(1)–C(4)
C(1)–C(2)–C(3)
C(3)–C(4)–C(5)
C(6)–C(5)–Os(1)
C(6)–C(5)–C(4)
83.30(4)
39.58(16)
108.6(4)
108.6(4)
83.3(3)
117.6(4)
C(4)–C(31)–C(32) 176.2(5)
C(3)–C(4)–C(31) 126.3(4)
clear. The possibility that the fulvene ring is rotating very
rapidly in 3 was excluded as additional 31P signals were not
observed for a CD2Cl2 solution of 3 at low temperature
(220 K). Since in situ 31P NMR spectroscopy showed a
minor 31P signal along with that of 3 (see above), we tenta-
tively assume that another conformer of 3 may also be pro-
duced in the reaction, although we were not able to isolate
or identify it. We note that two isomers have been observed
for [RuCl2(py){(η6-C5Me4(=CPh2)}] whereas only one iso-
mer was observed for the closely related complex
[RuCl2(dmso){(η6-C5Me4(=CPh2)}].[22]
It is interesting to note that complexes 2a and 3 adopt
different conformations in the solid state. This difference
could be related to the relative bulkiness of SiMe3, Ph, and
CϵCPh. One might expect that the steric effects of these
groups are in the order SiMe3 Ͼ Ph Ͼ CϵCPh, therefore
the bulky PPh3 ligand tends to be in a position close to
CϵCPh rather than Ph in 3, but close to Ph rather than
SiMe3 in 2a.
Figure 2. Molecular structure of [OsCl2{η6-C5H(CϵCPh)(Ph)2-
(=CHPh)}(PPh3)] (3).
Like complex 2, the fulvene ligand in 3 is also η6-coordi-
nated to osmium. However, the interaction between the
exocyclic double bond and the osmium center is stronger
for 3. Thus, the Os–C(6) bond length is 2.392(4) Å and the
exocyclic C–C double bond [C(5)–C(6)] bond length is
1.424(6) Å. For comparison, the Os–C(exocyclic) bond
length is 2.632(4) Å and the exocyclic C–C bond length is
1.380(5) Å in complex 2a. The inclination angle of 3 (38.2°)
is also significantly larger than that of 2a (26.9°). The struc-
tural features associated with the Os(η6-fulvene) moiety in
3 are similar to those of the previously reported osmium
fulvene complexes [(η5-C5Me5)Os{η6-C5Me4(=CPh2)}]-
(PF6),[19] [(η5-C5Me5)Os{η6-C5Me4(=CH2)}](BPh4),[20]
and [(η5-C5Me5)Os{η6-C5Me4(=CHC6F5)}](PF6)[21] (see
Table 2).
We also studied the reaction of 1 with SiMe3CϵC–
CϵCSiMe3. However, the reaction produced many un-
identified phosphorus-containing species which proved dif-
ficult to separate and identify.
1
Consistent with the solid-state structure, the H NMR
spectrum displays two signals at δ = 6.00 and 6.62 ppm as-
signable to the ring proton and the exocyclic =CH proton,
respectively. The 31P{1H} NMR spectrum shows a singlet
at δ = –8.0 ppm (in CD2Cl2). It is interesting to note that
two isomers are observed for 2 in solution but only one
isomer is observed for 3. Complex 3 can, in principle, also
Coupling Reaction of [OsCl2{=CPh(η2-CH=C=CHPh)}-
(PPh3)2] (1) with Styrene
The easy formation of fulvene complexes from the reac-
exhibit conformational isomerism in solution, and the exact tion of [OsCl2{=CPh(η2-CH=C=CHPh)}(PPh3)2] (1) with
reason why only one conformer is observed for 3 is not alkynes promoted us to investigate the reaction of 1 with
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G. Jia et al.
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styrene. Treatment of complex 1 with an excess of styrene
in wet CH2Cl2 leads to the formation of the bimetallic com-
plex [(PPh3)2ClOs(µ-Cl)3Os(H2O)(PPh3)2] (4) as the only
phosphorus-containing product (Scheme 6).
Scheme 6.
Complex 4 was isolated as a light-brown solid in 75%
yield and was characterized by elemental analysis, NMR
spectroscopy, and mass spectrometry. The 31P{1H} NMR
spectrum of 4 in C6D6 displays four sets of doublets of
equal intensity at δ = –6.5, –7.8 (JP,P = 11.4 Hz), –16.4, and
–17.4 ppm (JP,P = 16.7 Hz), thereby indicating the presence
of four inequivalent phosphorus nuclei. This pattern is
closely analogous to that of the dinuclear complex
[(PPh3)2ClOs(µ-Cl)3Os{=C=CH[C(OH)Ph2]}(PPh3)2][23]
and suggests the formation of a bimetallic complex of the
type [(PPh3)2ClOs(µ-Cl)3Os(L)(PPh3)2].
Definite proof of the structure came from a single-crystal
X-ray structure analysis. Crystals suitable for X-ray diffrac-
tion were grown from a CH2Cl2 solution of 4 layered with
hexane. Selected bond lengths and angles are given in
Table 4 and a view of the molecular geometry of 4 is shown
in Figure 3. The structure of 4 is similar to that of [(PPh3)2-
ClOs(µ-Cl)3Os{=C=CH[C(OH)Ph2]}(PPh3)2],[23] with re-
placement of the vinylidene ligand in the latter complex by
an aqua ligand, and deserves no further comments.
Figure 3. Molecular structure of [(PPh3)2ClOs(µ-Cl)3Os(H2O)-
(PPh3)2] (4).
several organic products, among which compound 5 is the
most dominant (ca. 78%). A sample of compound 5 could
be isolated as an oil by column chromatography on silica
gel using hexane as the eluent, and its structure was readily
deduced from spectroscopic data. Thus, the FAB mass spec-
trum shows an ion peak at m/z 308.1, indicating that it is
composed of a molecule of styrene and the original allenyl-
1
carbene unit of 1. The H NMR spectrum (C6D6) shows
two multiplets at δ = 2.98 and 3.29 ppm, which could be
assigned to the two diastereotopic CH2 ring protons
C(4)Ha and C(4)Hb, respectively (see Scheme 6 for label-
1
1
ling). The H and H-1H COSY NMR spectra clearly indi-
cate that the CH2 group is adjacent to a CH group, which
1
has its H NMR signal at δ = 4.16 ppm and is assignable
Table 4. Selected bond lengths [Å] and angles [°] for [(PPh3)2-
ClOs(µ-Cl)3Os(H2O)(PPh3)2]·CH2Cl2 (4·CH2Cl2).
to the signal of C(5)H. The presence of the stereogenic cen-
ter at C5 is responsible for the different environments
around C(4)Ha and C(4)Hb. The coupling constant between
C(4)Ha and C(4)Hb is 17.3 Hz, while the coupling constants
between C(5)H and C(4)Hs are 3.7 and 8.3 Hz for C(4)Ha
and C(4)Hb, respectively, consistent with the assignment
Os(1)–P(1)
Os(1)–P(2)
Os(1)–Cl(1)
Os(1)–Cl(2)
Os(1)–Cl(3)
Os(1)–O(1)
2.337(3)
2.335(3)
2.439(2)
2.463(3)
2.403(3)
2.294(9)
99.51(10)
168.96(10)
168.35(9)
165.29(18)
93.65(10)
100.64(10)
90.13(9)
79.18(9)
91.70(9)
81.66(9)
79.03(8)
92.64(17)
91.41(19)
92.49(17)
84.88(19)
87.48(8)
84.97(8)
Os(2)–P(3)
Os(2)–P(4)
Os(2)–Cl(1)
Os(2)–Cl(2)
Os(2)–Cl(3)
Os(2)–Cl(4)
2.278(3)
2.287(3)
2.392(3)
2.523(3)
2.540(2)
2.401(3)
98.21(10)
161.17(8)
170.58(9)
164.24(9)
93.34(9)
94.19(10)
96.76(10)
100.03(10)
87.51(9)
79.03(8)
89.56(10)
95.59(9)
77.40(8)
85.80(9)
77.85(8)
84.10(8)
1
that the latter is formally trans to C(5)H. In the H NMR
P(2)–Os(1)–P(1)
P(1)–Os(1)–Cl(1)
P(2)–Os(1)–Cl(2)
O(1)–Os(1)–Cl(3)
P(1)–Os(1)–Cl(3)
P(2)–Os(1)–Cl(3)
P(2)–Os(1)–Cl(1)
Cl(3)–Os(1)–Cl(1)
P(1)–Os(1)–Cl(2)
Cl(3)–Os(1)–Cl(2)
Cl(1)–Os(1)–Cl(2)
O(1)–Os(1)–P(1)
O(1)–Os(1)–P(2)
O(1)–Os(1)–Cl(1)
O(1)–Os(1)–Cl(2)
Os(2)–Cl(1)–Os(1)
Os(1)–Cl(3)–Os(2)
P(3)–Os(2)–P(4)
Cl(1)–Os(2)–Cl(4)
P(3)–Os(2)–Cl(2)
P(4)–Os(2)–Cl(3)
P(3)–Os(2)–Cl(1)
P(4)–Os(2)–Cl(1)
P(3)–Os(2)–Cl(4)
P(4)–Os(2)–Cl(4)
P(4)–Os(2)–Cl(2)
Cl(1)–Os(2)–Cl(2)
Cl(4)–Os(2)–Cl(2)
P(3)–Os(2)–Cl(3)
Cl(1)–Os(2)–Cl(3)
Cl(4)–Os(2)–Cl(3)
Cl(2)–Os(2)–Cl(3)
Os(1)–Cl(2)–Os(2)
spectrum, the signal of the C(2)H ring proton appears at δ
= 6.32 ppm and the signal of the exocyclic CHPh proton
[C(6)H] appears as a triplet at δ = 7.51 ppm due to coupling
with the protons of the CH2 group.
Scheme 7 shows a plausible mechanism for the formation
of 4 and 5 from the reaction of 1 with styrene. Complex 1
can rearrange to metallacyclobutene A, which can undergo
cycloaddition with styrene to give the metallacyclic interme-
diate C or C1. Subsequent reductive elimination of C or C1
would give 5 and the transient OsCl2(PPh3)2 fragment,
which reacts with water in solution to give 4. Although we
have no direct evidence for intermediates C and C1, they
are closely related to intermediates B and B1.
The allenylcarbene complex 1 was originally derived
from the coupling of two molecules of phenylacetylene.
Obviously, the hydrocarbon ligand of 1 has been elimin- Thus, the net transformation involving formation of 1 and
1
ated from the metal center in the reaction. The H NMR the coupling of 1 with styrene represenst a rare example of
spectrum of the reaction mixture shows the formation of a [2+2+1] co-cyclotrimerization of alkynes and alkenes.
2698
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© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 2693–2701

Coupling of an Allenylcarbene Complex with Alkynes and Styrene
FULL PAPER
Scheme 7.
extract produced a green precipitate, which was collected by fil-
tration, washed with hexane (2ϫ30 mL), and dried under vacuum
overnight. The 31P{1H} and 1H NMR spectra indicate the presence
of two isomers in a ratio of about 1:4.5. Yield: 0.34 g (81%). FAB-
MS (NBA): m/z 826 [M+]. C39H37Cl2OsP2Si: calcd. C 56.72, H
4.52; found C 56.68, H 4.61.
While many examples of [2+2+2] co-cyclotrimerization of
alkynes and alkenes to give cyclohexadienes are known,[24]
the related [2+2+1] co-cyclotrimerization of alkynes and al-
kenes, to the best of our knowledge, is still unknown.
In summary, we have demonstrated that the allenylcar-
bene complex [OsCl2{=CPh(η2-CH=C=CHPh)}(PPh3)2]
(1), which is originally derived from the coupling of two
molecules of phenylacetylene at osmium, can undergo
coupling reactions with alkynes to give fulvene complexes.
The reactions reported here support a previously proposed
mechanism that [2+2+1] cyclotrimerization of alkynes
could occur via metallacyclobutene intermediates. We have
also shown that complex 1 can undergo a similar coupling
reaction with styrene. This result is interesting as it repre-
sents a rare example of metal-mediated [2+2+1] co-cyclo-
trimerization of alkynes and alkenes.
2a (PPh3 is trans to the exocyclic double bond): 1H NMR
(300.13 MHz, CD2Cl2, see Scheme 1 for labels): δ = 0.45 (s, 9 H,
SiMe3), 5.00 [d, JP,H = 4.0 Hz, 1 H, C(5)-H], 6.51 [s, 1 H, C(3)-H],
7.06–7.65 (m, C6H5, PPh3, mixed with those of 2b), 7.83 [d, JP,H
5.8 Hz, 1 H, C(6)-H] ppm. 13C{1H} NMR (100.4 MHz, CD2Cl2):
δ = 0.5 (s, SiMe3), 73.3 (s, C-3), 82.00 (s, C-5), 83.4 (d, JP,C
=
=
2.6 Hz, C-2), 98.1 (s, C-1), 108.1 (s, C-4), 108.5 (d, JP,C = 16.4 Hz,
C-6), 127.6–135.9 (m, C6H5, PPh3, mixed with those of 2b) ppm.
31P{1H} NMR (121.5 MHz, C6D6): δ = –0.3 (s) ppm.
2b (PPh3 is cis to the exocyclic double bond): 1H NMR
(300.13 MHz, CD2Cl2): δ = 0.50 (s, 9 H, SiMe3), 5.49 [s, 1 H, C(5)-
H], 6.31 [s, 1 H, C(3)-H], 6.80 [s, 1 H, C(6)-H], 7.06–7.65 (m, C6H5,
PPh3, mixed with those of 2a) ppm. 13C{1H} NMR (100.4 MHz,
CD2Cl2): δ = –0.1 (s, SiMe3), 79.2 (s, C-5), 82.6 (s, C-6), 94.5 (s, C-
Experimental Section
4), 97.5 (s, C-1), 100.4 (d, JP,C = 10.3 Hz, C-2), 111.5 (d, JP,C
=
All manipulations were carried out under nitrogen using standard
Schlenk techniques unless otherwise stated. Solvents were distilled
under nitrogen from sodium benzophenone (hexane, diethyl ether,
thf), sodium (benzene), or calcium hydride (CH2Cl2).
[Os{=CPh(η2-CH=C=CHPh)}(PPh3)2][16] was prepared according
to the literature method. All other reagents were used as received
from Aldrich Chemical Co. USA.
8.9 Hz, C-3), 127.9–137.1 (m, C6H5, PPh3, mixed with those of 2a)
ppm. 31P{1H} NMR (121.5 MHz, C6D6): δ = –7.8 (s) ppm.
[OsCl2{η6-C5H(CϵCPh)(Ph)2(=CHPh)}(PPh3)] (3): A mixture of
[Os{=CPh(η2-CH=C=CHPh)Cl2(PPh3)2] (0.20 g, 0.20 mmol) and
PhCϵC–CϵCPh (0.20 g, 0.99 mmol) in benzene (15 mL) was re-
fluxed for 1 h. Unreacted [OsCl2{=CPh(CH=C=CPh)(PPh3)2] was
then removed by filtration and residue was washed with benzene
(2ϫ5 mL). The solvent was removed from the brown filtrate under
vacuum and the residue dissolved in CH2Cl2 (2 mL). Addition of
diethyl ether (8 mL) to the residue gave a greenish brown precipi-
tate, which was collected by filtration, washed with diethyl ether
(3ϫ2 mL), and dried under vacuum. The residue was recrystallized
from benzene to give a red precipitate, which was collected by fil-
tration, washed with benzene (2 mL) and diethyl ether (2ϫ3 mL),
Microanalyses were performed by M-H-W Laboratories (Phoenix,
1
AZ). H, 13C{1H}, and 31P{1H} NMR spectra were recorded with
a JEOL EX-400 spectrometer (400 MHz) or a Bruker ARX-300
1
spectrometer (300 MHz). H and 13C NMR shifts are quoted rela-
tive to TMS, and 31P chemical shifts relative to 85% H3PO4. Mass
spectra were recorded with a Finnigan TSQ7000 spectrometer.
[OsCl2{η6-C5H2(Ph)(SiMe3)(=CHPh)}(PPh3)] (2): HCϵCSiMe3
(0.43 mL, 3.0 mmol) was added to a solution of [OsCl2(=CPh-
CH=C=CPh)(PPh3)2] (0.50 g, 0.50 mmol) in CH2Cl2 (50 mL) and
the reaction mixture was stirred at room temperature for 72 h to
give a brown solution. The volume of the mixture was reduced to
about 1 mL, then diethyl ether (20 mL) was added slowly with stir-
ring and the mixture was filtered to remove a small amount of
dark brown precipitate. The filtrate was evacuated to dryness under
vacuum and the residue was extracted with 1 mL of benzene to
give a brown solution. Addition of hexane (30 mL) to the benzene
and
C50H37Cl2OsP·0.25CH2Cl2: calcd. C 63.45, H 3.97; found C 63.70,
H 4.20. 1H NMR (300.13 MHz, CD2Cl2): δ = 6.00 (d, JP,H
dried
under
vacuum.
Yield:
80 mg
(43%).
=
2.1 Hz, 1 H, =CH), 6.62 (d, JP,H = 5.1 Hz, 1 H, =CHPh), 6.30–
7.74 (m, 35 H, C6H5, PPh3) ppm. 31P{1H} NMR (121.5 MHz,
CD2Cl2): δ = –8.0 (s) ppm.
[(PPh3)2ClOs(µ-Cl)3Os(H2O)(PPh3)2] (4) and 5: Styrene (0.18 mL,
1.6 mmol) was added to
a
solution of [OsCl2{=CPh-
Eur. J. Inorg. Chem. 2007, 2693–2701
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2699

G. Jia et al.
FULL PAPER
Table 5. Crystallographic details for complexes 2a, 3, and 4.
2a
3·3C6D6
4·CH2Cl2
Empirical formula
Formula weight
Temperature [K]
Radiation (Mo-Kα) [Å]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
C39H37Cl2OsPSi
825.85
293(2)
0.71073
tetragonal
P42/n
26.474(3)
26.474(3)
9.9105(15)
90
C50H37Cl2OsP·3C6D6
1164.19
100(2)
C72H62Cl4OOs2P4·CH2Cl2
1674.22
293(2)
0.71073
0.71073
triclinic
triclinic
¯
¯
P1
P1 (no. 2)
12.6406(9)
14.4993(10)
14.6828(10)
86.7760(10)
89.6520(10)
2622(3)
14.162(5)
14.612(5)
20.423(7)
77.944(8)
76.462(9)
3870(2)
β [°]
90
V [Å3]
6945.8(15)
8
1.579
3.933
3280
Z
2
2
dcalcd, [gcm–3]
Absorption coefficient [mm–1]
F(000)
1.475
2.607
1176
1.437
3.608
1648
Crystal size [mm]
θ range [°]
Reflections collected
Independent reflections
Data / restraints / parameters
Goodness-of-fit on F2
Final R [I Ͼ 2σ(I)]
0.35ϫ0.30ϫ0.30
2.18 to 27.55
45630
7989 (Rint = 0.0488)
7989 / 0 / 409
0.930
R1 = 0.0287
wR2 = 0.0631
1.177 and –0.747
0.20ϫ0.15ϫ0.05
1.39 to 25.00
25255
9174(Rint = 0.0499)
9174 / 0 / 649
0.992
R1 = 0.0379
wR2 = 0.0654
1.137 and –1.506
0.12ϫ0.04ϫ0.04
1.54 to 25.00
18978
12237 (Rint = 0.0937)
12237 / 62 / 780
0.943
R1 = 0.0770
wR2 = 0.1186
1.542 and –1.062
Largest diff. peak and hole [eÅ–3]
(CH=C=CPh)(PPh3)2] (0.32 g, 0.32 mmol) in CH2Cl2 (20 mL) and
the reaction mixture was stirred at room temperature for 24 h to
give a light-brown solution. The volume of the reaction solution
was reduced to about 1 mL and hexane (30 mL) was then added
slowly with stirring to produce a light-brown precipitate. The mix-
ture was further stirred for 10 min and then filtered. The solid was
collected by filtration, washed with diethyl ether (2ϫ15 mL) and
hexane (15 mL), and dried under vacuum to give 4. Yield: 0.19 g
(75%). C72H62Cl4P4Os2: calcd. C 54.41, H 3.93; found C 54.52, H
4.12. FAB-MS (NBA): m/z 1570.8 [M – H2O]+. 1H NMR
perature for 2 and 4, and at 100 K for 3. Data reduction and ab-
sorption correction were performed using SAINT v.6.26 and SAD-
ABS v.2.03, respectively. Structure solution and refinement were
performed using the SHELXTL v.6.10 software package. All three
structures were solved by direct methods, expanded by difference
Fourier syntheses, and refined by full-matrix least-squares on F2.
Non-hydrogen atoms were refined anisotropically, except for the
CH2Cl2 solvent in 4. This was found to be severely disordered and
its atoms were given split occupancies and refined isotropically
using C–Cl bond length restraints. Some phenyl rings of the PPh3
(300.13 MHz, C6D6): δ = 7.00–7.16 (m, 22 H), 7.26–7.35 (m, 26 ligands in 4 also exhibited extensive disorder and were refined with
H), 7.80–8.03 (m, 12 H), (PPh3) ppm. 31P{1H} NMR (121.5 MHz, ideal C–C distances and planarity restraints. All hydrogen atoms
C6D6): δ = –6.5 (d), –7.8 (d), (JP,P = 11.4 Hz), –16.4 (d), –17.4 (d)
(JP,P = 16.7 Hz) ppm. The filtrate and the washing solution ob-
tained above were collected together and the solvent was pumped
off. The residue was extracted with 1 mL of benzene and loaded
onto a silica gel column. The column was eluted with hexane to
give the organic compound 5 along with a small amount of other
unidentified organic species as a yellow solution, which was evapo-
rated to dryness on a rotary evaporator and dried under vacuum
were placed in geometrical positions and with riding parameters.
Further crystallographic details are given in Table 5.
CCDC-631969 (for 2a), -631970 (for 3), and -631971 (for 4) contain
the supplementary crystallographic data for this paper. These data
can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
to give a yellow oil. FAB-MS (NBA): m/z 308.1 [M+]. 1H NMR Acknowledgments
(300.13 MHz, C6D6, see Scheme 6 for labels): δ = 2.98 [m,
3
4
2JC(4)-H ,C(4)-H = 17.3, JC(4)-H ,C(5)-H = 3.7, JC(4)-H ,C(6)-H ≈ 1.8,
This work was supported by the Hong Kong Research Grant
Council (project no. 601804) and the National Natural Science
Foundation of China through the Outstanding Young Investigator
Award Fund (project no. 20429201).
a
b
a
a
4JC(4)-H ,C(2)-H ≈ 0.9 Hz, 1 H, C(4)-Ha], 3.29 [m, JC(4)-H ,C(4)-H
17.3, JC(4)-H,C(5)-H = 8.3, JC(4)-H ,C(6)-H ≈ 2.0, JC(4)-H ,C(2)-H
=
≈
8.3,
2
a
b
3 a
4
4
b
b
3
0.9 Hz,
1
H, C(4)-Hb], 4.16 [ddd, JC(4)-H ,C(5)-H
=
b
3JC(4)-H ,C(5)-H = 3.7, 4JC(2)-H,C(5)-H = 2.5 Hz, 1 H, C(5)-H], 6.32 [br.
a
4
s, W1/2 = 4.5 Hz, 1 H, C(2)-H], 7.51 [br. t, JC(4)-H, C(6)-H = 1.8 Hz,
[1] a) S. Kotha, E. Brahmachary, K. Lahiri, Eur. J. Org. Chem.
2005, 4741–4767; b) S. Saito, Y. Yamamoto, Chem. Rev. 2000,
100, 2901–2915; c) M. Lautens, W. Klute, W. Tam, Chem. Rev.
1996, 96, 49–92; d) H. W. Frühauf, Chem. Rev. 1997, 97, 523–
596.
[2] For examples of recent work on the catalytic cyclotrimerization
of alkynes, see: a) V. Cadierno, S. E. García-Garrido, J. Gi-
meno, J. Am. Chem. Soc. 2006, 128, 15094–15095; b) M. Kak-
eya, T. Fujihara, T. Kasaya, A. Nagasawa, Organometallics
2006, 25, 4131–4137; c) Y. Yamamoto, T. Hashimoto, K. Hat-
1 H, C(6)-H], 6.77–7.77 (m, 15 H, Ph) ppm.
Crystallographic Details for 2a, 3, and 4: Crystals of 2 and 4 suitable
for X-ray diffraction were grown from CH2Cl2 solutions of 2 and
4 layered with hexane, and crystals of 3 were grown from a CH2Cl2
solution layered with benzene. Data collections were performed
with a Bruker AXS diffractometer equipped with a SMART APEX
CCD area detector. Intensity data were collected using graphite-
monochromated Mo-Kα radiation (λ = 0.71073 Å) at room tem-
2700
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Eur. J. Inorg. Chem. 2007, 2693–2701

Coupling of an Allenylcarbene Complex with Alkynes and Styrene
FULL PAPER
tori, M. Kikuchi, H. Nishiyama, Org. Lett. 2006, 8, 3565–3568;
d) N. Saino, F. Amemiya, E. Tanabe, K. Kase, S. Okamoto,
Org. Lett. 2006, 8, 1439–1442; e) K. Tanaka, G. Nishida, M.
Ogino, M. Hirano, K. Noguchi, Org. Lett. 2005, 7, 3119–3121;
f) Y. Yamamoto, J. I. Ishii, H. Nishiyama, K. Itoh, J. Am.
[13] K. W. Chiu, C. G. Howard, H. S. Rzepa, R. N. Sheppard, G.
Wilkinson, A. M. R. Galas, M. B. Hursthouse, Polyhedron
1982, 1, 441–451.
[14] T. B. Wen, Z. Y. Zhou, G. Jia, Angew. Chem. Int. Ed. 2006, 45,
5842–5846.
Chem. Soc. 2005, 127, 9625–9631; g) L. V. R. Boñaga, H. C. [15] E. Becker, K. Mereiter, M. Puchberger, R. Schmid, K. Kirch-
Zhang, A. F. Moretto, H. Ye, D. A. Gauthier, J. Li, G. C. Leo,
B. E. Maryanoff, J. Am. Chem. Soc. 2005, 127, 3473–3485; h)
E. Rüba, R. Schmid, K. Kirchner, M. J. Calhorda, J. Or-
ganomet. Chem. 2003, 682, 204–211; i) K. Kirchner, M. J. Cal-
horda, R. Schmid, L. F. Veiros, J. Am. Chem. Soc. 2003, 125,
11721–11729.
ner, A. Doppiu, A. Salzer, Organometallics 2003, 22, 3164–
3170.
[16] T. B. Wen, W. Y. Hung, H. H. Y. Sung, I. D. Williams, G. Jia,
J. Am. Chem. Soc. 2005, 127, 2856–2857.
[17] Allenylcarbene complexes are still rare. For examples of other
reported allenylcarbene complexes, see: a) E. Rüba, K. Mere-
iter, R. Schmid, V. N. Sapunov, K. Kirchner, H. Schotten-
berger, M. J. Calhorda, L. F. Veiros, Chem. Eur. J. 2002, 8,
3948–3961; b) E. Rüba, K. Mereiter, R. Schmid, K. Kirchner,
H. Schottenberger, J. Organomet. Chem. 2001, 637–639, 70–74;
c) R. Schmid, K. Kirchner, Eur. J. Inorg. Chem. 2004, 2609–
2626.
[18] a) A. H. Klahn, B. Oelckers, F. Godoy, M. T. Garland, A.
Vega, R. N. Perutz, C. L. Higgitt, J. Chem. Soc., Dalton Trans.
1998, 3079–3086; b) A. H. Klahn, M. H. Moore, R. N. Perutz,
J. Chem. Soc., Chem. Commun. 1992, 1699–1701; c) F. G. N.
Cloke, J. P. Day, J. C. Green, C. P. Moreley, A. C. Swain, J.
Chem. Soc., Dalton Trans. 1991, 789–804.
[3] For examples of the formation of benzene complexes, see: a)
Y. Yamamoto, T. Arakawa, R. Ogawa, K. Itoh, J. Am. Chem.
Soc. 2003, 125, 12143–12160; b) C. Bianchini, K. G. Caulton,
T. J. Johnson, A. Meli, M. Peruzzini, F. Vizza, Organometallics
1995, 14, 933–943; c) C. Bianchini, K. G. Caulton, C. Chardon,
M. L. Doublet, O. Eisenstein, S. A. Jackson, T. J. Johnson, A.
Meli, M. Peruzzini, W. E. Streib, A. Vacca, F. Vizza, Organo-
metallics 1994, 13, 2010–2023; d) C. Bianchini, M. Graziani, J.
Kaspar, A. Meli, F. Vizza, Organometallics 1994, 13, 1165–
1173; e) C. Bianchini, P. Frediani, M. Graziani, J. Kaspar, A.
Meli, M. Peruzzini, F. Vizza, Organometallics 1993, 12, 2886–
2887.
[4] G. Moran, M. Green, A. G. Orpen, J. Organomet. Chem. 1983, [19] U. Turpeinen, A. Z. Kreindlin, P. V. Petrovskii, M. I. Rybin-
250, C15–C20.
skaya, J. Organomet. Chem. 1992, 441, 109–116.
[20] M. I. Rybinskaya, A. Z. Kreindlin, Y. T. Struchkov, A. I.
Yanovsky, J. Organomet. Chem. 1989, 359, 233–243.
[21] A. Z. Kreindlin, K. Y. Suponitsky, F. M. Dolgushin, Z. A. Sta-
rikova, M. I. Rybinskaya, Russ. Chem. Bull. Int. Ed. 2001, 50,
1616–1619.
[22] L. Fan, C. Wei, F. I. Aigbirhio, M. L. Turner, O. V. Gusev,
L. N. Morozova, D. R. T. Knowles, P. M. Maitlis, Organome-
tallics 1996, 15, 98–104.
[5] a) J. M. O’Connor, K. Hübner, R. Merwin, P. K. Gantzel, B. S.
Fong, J. Am. Chem. Soc. 1997, 119, 3631–3632; b) J. M.
O’Connor, A. Closson, K. Hübner, R. Merwin, P. Gantzel,
D. M. Roddick, Organometallics 2001, 20, 3710–3717.
[6] H. J. Kim, N. S. Choi, S. W. Lee, J. Organomet. Chem. 2000,
616, 67–73.
[7] E. S. Johnson, G. J. Balaich, P. E. Fanwick, I. P. Rothwell, J.
Am. Chem. Soc. 1997, 119, 11086–11087.
[8] U. Radhakrishnan, V. Gevorgyan, Y. Yamamoto, Tetrahedron
Lett. 2000, 41, 1971–1974.
[9] W. S. Han, S. W. Lee, Organometallics 2005, 24, 997–1003.
[10] A. D. Burrows, M. Green, J. C. Jeffery, J. M. Lynam, M. F. Ma-
hon, Angew. Chem. Int. Ed. 1999, 38, 3043–3045.
[11] H. Komatsu, Y. Suzuki, H. Yamazaki, Chem. Lett. 2001, 998–
999.
[23] T. B. Wen, Z. Y. Zhou, M. F. Lo, I. D. Williams, G. Jia, Orga-
nometallics 2003, 22, 5217–5225.
[24] See, for example: a) V. Gandon, N. Agenet, K. P. C. Vollhardt,
M. Malacria, C. Aubert, J. Am. Chem. Soc. 2006, 128, 8509–
8520; b) M. J. Eichberg, R. L. Dorta, D. B. Grotjahn, K. Lam-
ottke, M. Schmidt, K. P. C. Vollhardt, J. Am. Chem. Soc. 2001,
123, 9324–9337 and references cited therein.
[12] J. Moreto, K. Maruya, P. M. Bailey, P. M. Maitlis, J. Chem.
Soc., Dalton Trans. 1982, 1341–1347.
Received: December 28, 2006
Published Online: April 23, 2007
Eur. J. Inorg. Chem. 2007, 2693–2701
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2701