Reactivity of the 30-electron dimolybdenum anion [Mo2(η5-C5H5)2(μ-PCy2)(μ-CO)2]- towards β,γ-unsaturated organic halides: Alkenyl, allenyl and alkoxycarbyne derivative

Article abstract of DOI:10.1016/j.jorganchem.2009.08.003

The 30-electron dimolybdenum anion [Mo₂Cp₂(μ-PCy₂)(μ-CO)₂]^- reacts at room temperature with allyl chloride to give the unsaturated σ:π-bonded alkenyl derivative trans-[Mo₂Cp₂(μ-η

Full text of DOI:10.1016/j.jorganchem.2009.08.003

Journal of Organometallic Chemistry 694 (2009) 3864–3871
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Reactivity of the 30-electron dimolybdenum anion
[Mo2(
g
5-C5H5)2(
l-PCy2)(
l
-CO)2]ꢀ towards b,
c
-unsaturated organic halides:
Alkenyl, allenyl and alkoxycarbyne derivatives
*
M. Angeles Alvarez, M. Esther García, Alberto Ramos, Miguel A. Ruiz
Departamento de Química Orgánica e Inorgánica/IUQOEM, Universidad de Oviedo, E-33071 Oviedo, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 20 July 2009
Received in revised form 4 August 2009
Accepted 4 August 2009
Available online 8 August 2009
The 30-electron dimolybdenum anion [Mo2Cp2(l-PCy2)(l
-CO)2]ꢀ reacts at room temperature with allyl
r:p-bonded alkenyl derivative trans-[Mo2Cp2(l- :g
g1 2-CMeCH2)-
chloride to give the unsaturated
-PCy2)(CO)2], this requiring 2,1-hydrogen shift in the allyl moiety probably induced by the
unsaturated nature of the dimetal center. In a similar way, the dimolybdenum anion reacts with trans-
1-chloro-2-butene (crotyl chloride) to give a mixture of the alkenyl complexes trans-[Mo2Cp2(
2-CEtCH2)( 2-CMeCHMe)(
-PCy2)(CO)2] and trans-[Mo2Cp2( -PCy2)(CO)2] in a 3:2 ratio, which
could not be separated by column chromatography. All these alkenyl species exhibit a dynamic behavior
in solution (fast on the NMR timescale even at low temperatures) involving alternative -bonding of the
(
l
a
l- :
g1
g
l
l
-
g1
:
g
l
Keywords:
Molybdenum
p
Metal–metal interactions
Alkenyl ligands
Carbyne ligands
Carbonyl ligands
Metal carbonyl anions
alkenyl ligand to each metal center. In contrast, the title anion reacts with propargyl chloride (ClCH2–
C„CH) without further rearrangement of the propargyl moiety, to afford the allenyl derivative trans-
[Mo2Cp2{
reacts with the title anion to give a mixture of two products, the carbyne complex [Mo2Cp2{
COC(O)CHCH2}( -PCy2)( -CO)] and the vinyl trans-[Mo2Cp2( -PCy2)(CO)2], in a 1:1
2-CHCH2)(
l- :g l-PCy2)(CO)2] as the major species. Acryloyl chloride (ClC(O)–CH@CH2) also
g2 3-CH2CCH)}(
l
-
l
l
l-
g1
:g
l
ratio. This reaction is a unique case in which a single electrophile can attack both nucleophilic positions
in the dimolybdenum anion, these being located at the O(carbonyl) and metal sites, respectively. The for-
mation of the vinyl derivative requires the decarbonylation of a metal-bound acryloyl group, which
proved to be an irreversible reaction, since the addition of CO to the above alkenyl complex gave instead
the tricarbonyl vinyl derivative cis-[Mo2Cp2(l- :g l-PCy2)(CO)3]. The structure of this elec-
g1 2-CHCH2)(
tron-precise complex was confirmed through
a
single-crystal X-ray diffraction analysis
(MoꢀMo = 3.0858(7) Å).
Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
num anions [Mo2Cp2(
sponding chloro complexes [Mo2Cp2(
l
-PA2)(
l
-CO)2]ꢀ (A = Cy, Ph, Et) via the corre-
-Cl)( -PA2)(CO)2] [3]. In that
l
l
The chemistry of metal carbonyl anions is of paramount impor-
tance in organometallic synthesis mainly due to their high nucleo-
philicity, which allows these molecules to react with a great
variety of electrophiles to form new MꢀE bonds (E = H, C, p- or
d-block elements) [1]. Although the number of mono- and polynu-
clear metal carbonyl anions reported in the literature is consider-
preliminary report, the synthetic potential of these unsaturated
species was already evident for the most stable member of that
group, the dicyclohexylphosphide-bridged anion [Mo2Cp2-
(l-PA2)(l
-CO)2]ꢀ (1), which showed two different nucleophilic
sites located at the metal atoms and the O atoms of the CO ligands,
respectively. It was also noticed then that, due to the unsaturated
nature of the anion, some rearrangements in the incoming electro-
phile could be induced, as shown by the reaction with allyl chloride
able, dinuclear anions bearing
a
metal–metal bond are
comparatively scarce. Among these ones, there are only a few com-
pounds bearing a multiple metal–metal bond according to the
Effective Atomic Number (EAN) formalism, and in most of these
cases no reactivity studies have been carried out, due to their insta-
bility or synthetic difficulties [2]. A few years ago, we discovered an
efficient synthetic route leading to the triply bonded dimolybde-
to give the alkenyl derivative trans-[Mo2Cp2(l- :g l-
g1 2-CMeCH2)(
PCy2)(CO)2], this requiring an unprecedented 2,1-hydrogen shift in
the hydrocarbon fragment [3].
We have reported recently a detailed study on the reactivity of
the anion 1 towards simple hydrocarbon halides RX revealing that,
depending on the electrophile being used, three main type of
products might be formed: (a) agostic alkyl complexes
* Corresponding author. Fax: +34 985103446.
E-mail address: mara@uniovi.es (M.A. Ruiz).
[Mo2Cp2(l-R)(l-PCy2)(CO)2], (b) alkoxycarbyne complexes
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.08.003

M.A. Alvarez et al. / Journal of Organometallic Chemistry 694 (2009) 3864–3871
3865
from comparable H-shifts, these being identified as trans-
[Mo2Cp2( -PCy2)(CO)2] (2b) and trans-[Mo2Cp2-
2-CEtCH2)(
2-CMeCHMe)(
-PCy2)(CO)2] (2c), which are obtained in a
l-
g1
:g
l
(l-
g1
:g
l
3:2 ratio (Chart 1). Unfortunately, this mixture could not be sepa-
rated using chromatographic techniques. To check the relevance of
the observed H-shifts in the above reactions the anion 1 was trea-
ted with ClCH2–CMe@CH2, a molecule in which an H-shift from the
C2 atom was not possible, but this gave only a complex reaction
mixture under similar conditions. Although we could not isolate
nor characterize the corresponding products being formed, the
spectroscopic data of the crude reaction mixture clearly denote
that no alkenyl derivatives are there present in significant
amounts.
In contrast to the above reactions, no H-shifts were observed in
the reactions of the lithium salt of 1 with the propargyl halides
XCH2–C„CH (X = Br, Cl), which instead lead to the formation of
Scheme 1. Pathways in the reactions of the anion 1 with simple hydrocarbon
halides. (Mo = MoCp; P = PCy2).
the corresponding allenyl derivative trans-[Mo2Cp2{
CH2CCH)}( -PCy2)(CO)2] (4) as the major product in both cases,
the reaction being completed after 5 min (X = Br) or 2 h (X = Cl)
at room temperature. Some trans-[Mo2Cp2( -Br)( -PCy2)(CO)2]
l- : -
g2 g3
l
[Mo2Cp2(l-COR)(
l-PCy2)(
l-CO)] and (c) the halide derivatives
[Mo2Cp2(
l
-PCy2)(
l
-X)(CO)2] (Scheme 1). The formation of these
l
l
products can be rationalized by assuming that three different
elemental processes might be involved in these reactions: (1)
nucleophilic attack of the anion through the metal center to give
the alkyl-bridged derivatives, (2) nucleophilic attack of the anion
through the oxygen atom of the carbonyl ligand to give the
carbyne-bridged derivatives, and (3) electron transfer, mainly to
give the halide-bridged derivatives [2].
[2] and another uncharacterized product were respectively formed
as minor products in these reactions, depending on the halide used.
Although the reaction was much faster when using allyl bromide, it
turned out to be less reproducible, and quite variable amounts of
the bromoderivative were actually obtained. Therefore, propargyl
chloride was preferred as a precursor in the formation of the alle-
nyl complex 4.
In this paper we report our results on the reactions of the unsat-
urated anion 1 with several b,c-unsaturated organic halides,
The result of the reaction of 1 with acryloyl chloride was hardly
predictable. Previously, we had found that the reaction of 1 with a
related electrophile as benzoyl chloride led to the quantitative for-
including allyl chloride. These substrates were of special interest
as potential candidates to observe unusual rearrangements after
coordination to the metal centers, as found in our preliminary
study of the reaction with allyl chloride mentioned above [3]. At
the same time, the unsaturated nature of the dimetal center might
also induce the coordination of the multiple CꢀC bonds present in
the added electrophile. As it will be discussed below, unusual 2,1-H
shift processes indeed prevail in the reactions with allyl chlorides
of the formula ClCH2–CR@CR0H (R = H; R0 = H, Me) to afford unsat-
mation of the corresponding carbyne complex [Mo2Cp2(
COC(O)Ph}( -CO)] [2]. In contrast, acryloyl chloride reacts with 1
to give a 1:1 mixture of the corresponding alkoxycarbyne derivative
[Mo2Cp2( -PCy2){ -COC(O)CH@CH2}( -CO)] (5) and the vinyl com-
plex trans-[Mo2Cp2( -PCy2)(CO)2] (2d) (Chart 1).
2-CHCH2)(
l-PCy2){l-
l
l
l
l
l
l-
g1
:g
To account for this difference in reactivity, we propose that the high-
er steric demand of the phenyl vs. the vinyl group prevents the
urated
r:p-bound alkenyl derivatives, but no rearrangement oc-
curs in the reaction with propargyl chloride (ClCH2–C„CH), this
giving an electron-precise allenyl compound. Finally, the reaction
with acryloyl chloride (ClC(O)–CH@CH2) provides a unique case
in which a single electrophile can attack to both nucleophilic posi-
tions in the dimolybdenum anion. When compared to the results
obtained in the reactions of 1 with simple hydrocarbon halides,
the results here reported reveal at least two substantial differences
in the behavior of the b,c-unsaturated organic halides: (a) the elec-
tron-transfer processes essentially are no longer under operation
and (b) agostic interactions (C–Hꢁ ꢁ ꢁMo) are not observed. The latter
was to be expected due to the presence of multiple C–C bonds in
the incoming electrophile, which are electron-donors more effi-
cient than single C–H bonds.
2. Results and discussion
2.1. Reactions of the anion 1 with allyl, propargyl and acryloyl
chlorides
The reaction of the lithium salt of 1 with allyl chloride (ClCH2–
CH@CH2) takes place readily at room temperature to give the
32-electron alkenyl complex trans-[Mo2Cp2(
-PCy2)(CO)2] (2a), this requiring a rare 2,1-H shift in the allyl
l- :g
g1 2-CMeCH2)-
(l
ligand, as discussed below. In a similar way, the room temperature
reaction of 1 with the trans isomer of crotyl chloride [ClCH2–
CH@CHMe] gives a mixture of two alkenyl compounds derived
Chart 1.

3866
M.A. Alvarez et al. / Journal of Organometallic Chemistry 694 (2009) 3864–3871
benzoyl fragment from accessing to the intermetallic region, thus
suppressing the formation of any acyl or related metal derivative.
The formation of the vinyl complex 2d requires the spontaneous
liberation of a CO at some intermediate stage of the reaction, a
matter to be discussed below. In any case, such a decarbonylation
process is irreversible, since the reaction of 2a with CO (1 atm)
takes place readily to yield the corresponding electron-precise tri-
carbonyl derivative cis-[Mo2Cp2(l- :g l-PCy2)(CO)3]
g1 2-CHCH2)(
(3), the reaction being completed in ca. 1 h at room temperature.
Scheme 2. Isomerization process proposed for compounds 2 in solution (P = PCy2).
We note that the carbonylation reaction of the related complex
trans-[Mo2Cp2{l- :g l-PCy2)(CO)2] to give an
g1 2-CHCH(ptol)}(
analogous tricarbonyl derivative requires 24 h for completion [4],
a difference possibly reflecting the higher protection of the unsat-
urated center provided by the ptol substituent.
ca. 1840 cmꢀ1, and the shoulder (not detected for 2a) at ca.
1870 cmꢀ1 to the C–O stretching bands of the isomers of type A,
whereas the more separated bands and having similar relative
intensities, at ca. 1890 (vs) and 1810 (vs) cmꢀ1 can be safely as-
signed to the isomers of type B. Both isomers would be intercon-
verting through a dynamic process well established for bridging
alkenyl compounds, known as the windshield wiper movement
[5]. In our case, this dynamic process is an isomerization process,
since as a result of it the CHR group gets close to either a CO ligand
(isomer A) or to a Cp ring (isomer B). This process is fast on the
NMR timescale for compounds 2, since the corresponding NMR
spectra suggest the presence of a single species in each case and
are not significantly modified even when recorded at ca. 213 K.
The 31P NMR spectra of compounds 2a–d exhibit a single and
relatively shielded resonance in the range 128–135 ppm. These
values are analogous to those found for the related alkenyl com-
pounds mentioned above [4] and are also consistent with the for-
mulation of a metal–metal double bond for these compounds. The
1H and 13C NMR spectra are also in good agreement with the pres-
ence in each case of a single species in solution having no symme-
try elements. Thus, compounds 2a–d all exhibit separate
resonances for the inequivalent Cp (1H, 13C), CO (13C) and Cy
groups (twelve different signals in the 13C NMR spectra). The
chemical shifts and coupling constants of these resonances (Table
1 and experimental section) are comparable to those measured
2.2. Solution structure of the dicarbonyl alkenyl complexes 2a–d
The spectroscopic data for compounds 2a–d are comparable to
those of the alkenyl complexes trans-[Mo2Cp2(
CRCHR’)( -PCy2)(CO)2] (R, R’ = H, ptol, CO2Me), recently prepared
by us through the reaction of the unsaturated hydride
[Mo2Cp2( -H)( -PCy2)(CO)2] with the pertinent 1-alkynes [4].
l- : -
g1 g2
l
l
l
The solution structure of the latter compounds has been discussed
at length already, and therefore only the relevant details for com-
pounds 2a–d will be discussed here. First, we note that compounds
2a–d also exhibit three or even four CꢀO stretching bands in the IR
spectra, when recorded in petroleum ether (Table 1). This can be
explained analogously by assuming the presence in solution of
two different and interconverting trans-dicarbonyl isomers (A
and B in Scheme 2). Isomer A would exhibit an almost antiparallel
arrangement of the CO ligands, with a relative angle close to 180°,
whereas in the isomer B this angle would be close to 90°. Note that
in both isomers the R0 group is proposed to point away from the di-
metal center, which should be sterically favoured over the alterna-
tive possibility (R0 pointing towards the dimetal center) when
R0 = Me. In any case, the different arrangement of the carbonyl li-
gands in both isomers would then account for the pattern observed
in the IR spectra of 2a–d, so that we can assign the strong band at
for the above mentioned alkenyl complexes trans-[Mo2Cp2(
2-CRCHR’)( -PCy2)(CO)2] (R, R0 = H, ptol, CO2Me) [4], and
therefore deserve no further comments.
l-
g1
:g
l
Table 1
Selected IRa and NMRb spectroscopic data for new compounds.
Compound
mCO (cmꢀ1
)
dP
dH/H [JHH
]
dC/C
a
a
Hb, [JHH
c
]
Cb,
c
[Mo2Cp2(
l
-
g1
:
g
2-CMeCH2)(
l
-PCy2)(CO)2] (2a)
1888 (vs), 1838 (s)
131.2
174.6
79.6d
1808 (vs)c
5.07 [2.6], 4.68 [2.6]
5.03 [2], 4.76 [2]
6.17
[Mo2Cp2(
[Mo2Cp2(
[Mo2Cp2(
l
l
l
-
-
-
g1
g1
g1
:
:
:
g
g
g
2-CEtCH2)(
l
-PCy2)(CO)2] (2b)
1883 (vs), 1873 (m, sh) 1841 (s), 1806 (vs)c
1883 (vs), 1873 (m, sh) 1841 (s), 1806 (vs)c
1886 (m), 1871 (m, sh) 1843 (vs), 1821 (m, sh)c
128.4
130.5
135.0
2-CMeCHMe)(
l-PCy2)(CO)2] (2c)
-
2-CHCH2)(
l
-PCy2)(CO)2] (2d)
8.56 [12,9]
153.2
84.2e
148.2
32.7f
5.28 [12,3], 4.91 [9,3]
8.93 [9,9]
[Mo2Cp2(
l
-
g1
:
g
2-CHCH2)(
l
-PCy2)(CO)3] (3)
1937 (vs), 1864 (m) 1834 (m)
1867 (m, sh), 1844 (vs)
1743 (w, C@O)
250.5e
163.3
3.34 [9], 1.07 [9]f
4.17 [1.5], 4.00 [1.1]
4.72 [1.5, 1.1]
[Mo2Cp2{
[Mo2Cp2{
l
-
g2
:
g
3-CH2CCH}(
l
-PCy2)(CO)2](4)
68.9, 112.5
61.0
l
-COC(O)CHCH2}(
l
-PCy2)( -CO)] (5)
l
6.12 [17, 10]g
159.7i
128.5j
132.4k
1684 (vs,
l-CO)
229.6
6.44 [17, 1.5]h, 5.93 [10, 1.5]h
a
Recorded in dichloromethane solution, unless otherwise stated.
Recorded at 300.13 (1H), 121.50 (31P{1H}) or 75.47 MHz (13C{1H}) at 290 K in CD2Cl2 solutions unless otherwise stated, d in ppm relative to TMS (1H, 13C{1H}) or external
b
85% aqueous H3PO4 (
31P{1H}), J in Hz; the bridgehead carbon atoms of the alkenyl or allenyl ligands are referred to as C .
a
c
In petroleum ether.
At 100.63 MHz and 213 K.
In C6D6.
d
e
f
In CDCl3.
g
h
i
–C(O)–CH@CH2.
–C(O)–CH@CH2.
–C(O)–CH@CH2.
–C(O)–CH@CH2.
–C(O)–CH@CH2.
j
k

M.A. Alvarez et al. / Journal of Organometallic Chemistry 694 (2009) 3864–3871
3867
Table 2
2.3. Structure of the tricarbonyl complex 3
Selected bond lengths (Å) and angles (deg) for compound 3.
An X-ray diffraction analysis was performed on compound 3
(Fig. 1 and Table 2). The molecule of 3 is built from MoCp(CO)
and MoCp(CO)2 moieties arranged in a cisoid conformation and
Mo(1)–Mo(2)
Mo(1)–C(5)
Mo(2)–C(5)
Mo(2)–C(4)
Mo(1)–P(1)
Mo(2)–P(1)
C(4)–C(5)
Mo(1)–C(1)
Mo(1)–C(2)
Mo(2)–C(3)
3.0858(7)
2.240(2)
2.107(2)
2.298(2)
2.5702(6)
2.3292(6)
1.413(3)
1.956(2)
1.952(2)
1.927(2)
Mo(2)–P(1)–Mo(1)
C(2)–Mo(1)–C(1)
C(2)–Mo(1)–Mo(2)
C(1)–Mo(1)–Mo(2)
C(3)–Mo(2)–Mo(1)
C(4)–C(5)–Mo(2)
C(4)–C(5)–Mo(1)
C(4)–Mo(2)–Mo(1)
C(5)–C(4)–Mo(2)
Mo(2)–C(5)–Mo(1)
C(1)–Mo(1)–P(1)
C(2)–Mo(1)–P(1)
C(3)–Mo(2)–P(1)
C(4)–Mo(2)–P(1)
C(5)–Mo(2)–P(1)
77.90(2)
79.0 (1)
115.5(1)
104.5(1)
117.2(1)
78.8(1)
125.0(2)
72.9(1)
64.1(1)
90.4(1)
116.5(1)
72.8(1)
86.0(1)
100.8(1)
95.9(1)
bridged by PCy2 and vinyl ligands. The latter one is
r-bound to
the dicarbonyl fragment and -bound to the monocarbonyl frag-
p
ment. The intermetallic separation, 3.0858(7) Å, is very similar to
the corresponding distance measured for the isostructural and iso-
electronic compound [Mo2Cp2(l- :g l-PMe2)-
g1 2-CMeCHMe)(
(CO)3] (3.056(1) Å) [6], and consistent with the presence of a single
Mo–Mo bond, as it should be proposed for this 34-electron mole-
cule under the EAN formalism. As expected, this intermetallic
separation is much longer (by ca. 0.4 Å) than that measured for
the 32-electron dicarbonyl compound trans-[Mo2Cp2(
2-CMeCHMe)(
-SPh)(CO)2] [7], the latter being isoelectronic with
compounds 2a–d and bearing a double Mo@Mo bond according to
the same formalism. The -bond of the vinyl group in 3 [Mo(1)–
l- :
g1
g
l
tion in solution of the solid-state conformation. Compound 3
exhibits a characteristically deshielded resonance in the 31P NMR
spectrum at 250.5 ppm, some 115 ppm downfield from that of its
precursor 2d and consistent with the presence of a single metal–
metal bond in this 34-electron molecule. Its 1H NMR exhibits
strongly shielded Hb vinyl resonances at 3.34 and 1.07 ppm, several
ppm below those of the dicarbonyl precursor 2d. This can be ex-
r
C(5), 2.240(2) Å] is more than 0.1 Å longer than the corresponding
values in the mentioned alkenyl compounds [6,7]. In contrast, the
Mo(2)–C(5) and Mo(2)–C(4) distances of 2.107(2) and 2.298(2) Å,
respectively, are in all cases shorter than the corresponding values
in the mentioned compounds. This is suggestive of a particularly
strong
g
2-bonding interaction of the vinyl ligand with the Mo(2)
plained by recalling the high strength of the vinyl-Mo(2)
tion apparent in the crystal structure, perhaps approaching the
p-interac-
atom. As for the C–C distance within the vinyl ligand, 1.413(3) Å,
it is similar to those measured in other alkenyl compounds and
is ca. 0.07 Å longer than that found for ethylene, as expected. The
coordination of the dicyclohexylphosphide ligand is very asym-
metric, it being placed much closer to the monocarbonyl center
(P–Mo(1) = 2.3292(6) Å) than to the dicarbonyl center (P–
Mo(1) = 2.5702(6) Å), thus counterbalancing the difference in the
coordination numbers of both metal centers. Thus we could for-
mally consider the phosphide ligand to act as a two-electron donor
to the Mo(1), and as a one-electron donor to the dicarbonyl center
Mo(2). Under this view, the formal oxidation states of the metal
centers would be III and I, respectively. The same effect has been
observed for other dinuclear alkenyl complexes having different
description of the Mo(2)–C –Cb triangle as a metallacyclopropane
a
ring. A similar shielding effect is observed in the 13C NMR reso-
nances, with the one corresponding to Cb appearing at 32.7 ppm,
some 50 ppm upfield of the corresponding resonance in the dicar-
bonyl 2d.
2.4. Solution structure of the allenyl complex 4
Crystals suitable for an X-ray diffraction analysis could not be
obtained for this compound. Regardless of this fact, the spectro-
scopic data collected in solution for 4, when combined with the
data available for a significant number of allenyl-bridged com-
plexes described in the literature, are enough to support the pro-
posed structure (Chart 1). Its IR spectrum exhibits two bands
with the typical pattern of a trans-dicarbonyl complex, at 1867
(m, sh) and 1844 (vs) cmꢀ1. The NMR spectra are in good agree-
ment with the asymmetric structure of 4, this implying the appear-
ance of separate resonances for the pairs of CO and Cp ligands, and
also for all C atoms in the Cy rings (see experimental section). The
allenyl ligand gives rise to three distinct 1H NMR resonances in the
range 4.72–4.00 ppm, all of them exhibiting very small H–H
couplings. These chemical shifts are somewhat lower than those
coordination numbers at each metal center, such as [Mn2(
2-CHCH2)(
-PPh2)(CO)7] [8], (Mn–P: 2.255(2) and
2.367(1) Å) and the mentioned [Mo2Cp2(
2-CMeCHMe)(
PMe2)(CO)3] [6], (Mo–P: 2.300(3) and 2.515(3) Å).
l-
g1
:g
l
l-
g1
:g
l-
The spectroscopic data for compound 3 (Table 1) are in good
agreement with the solid-state structure discussed above and are
comparable to those of the related tricarbonyl [Mo2Cp2{
CHCH(ptol)}( -PCy2)(CO)3] previously reported by us [4]. Com-
pound 3 exhibits three bands in the IR spectrum with the expected
pattern for tricarbonyl derivatives of type [M2Cp2( -X)( -Y)(CO)3]
l- : -
g1 g2
l
l
l
(X, Y = 3-electron donor group) having a cisoid arrangement of the
CpM(CO)2 and CpM(CO) fragments [9], thus indicating the reten-
measured previously for the related cations of formula [Mo2L2(
:
l-
g2
g3-RC„C–CR0R00)(CO)4]+ (R, R0, R00@H, alkyl or aryl group;
L = Cp or related ligand) [10], a fact that can be attributed to the
differences in the overall charges in these complexes. The allenyl
ligand also gives rise to three resonances in the 13C spectrum,
easily assigned through a standard DEPT experiment, at 61.0
(CH), 112.5 (C) and 68.9 (CH2) ppm, close to those found for
[Mo2Cp0 (
l-
g2
:
g3-HC„C–CH2)(CO)4][BF4] (Cp0 =
g
5-C5H4Me) [10f],
2
a complex isoelectronic with 4 and characterized through an
X-ray diffraction study. Finally, the 31P NMR spectrum exhibits a
resonance at 163.3 ppm, a chemical shift some 30-35 ppm higher
than those measured for the 32-electron alkenyl compounds 2a–
d (Table 1), but much lower than that found for the electron-pre-
cise 3 (see above). We note, however, that there are other examples
of related electron-precise compounds displaying similar 31P
chemical shifts, such as the structurally characterized formimidoyl
derivative [Mo2Cp2(
Unfortunately, in the absence of diffraction data for compound 4
l-g, j:g, j l-PCy2)(CO)2] [11].
-CHNtBu)(
Fig. 1. ORTEP diagram (30% probability) of compound 3, with H atoms (except those
of the vinyl group) and Cy rings (except the C1 atoms) omitted for clarity.

3868
M.A. Alvarez et al. / Journal of Organometallic Chemistry 694 (2009) 3864–3871
we cannot define with precision the exact coordination mode of its
allenyl ligand since, due to the high unsaturation of the dimetal
center, this ligand might be acting as a five- (I in Fig. 2) or three-
(II in Fig. 2) electron-donor ligand or, most likely, somehow be-
tween these extreme coordination modes.
2.5. Solution structure of the alkoxycarbyne complex 5
The spectroscopic data for 5 are completely analogous to those
of other 30-electron alkoxycarbyne compounds previously charac-
terized by our group [2,3]. These unsaturated molecules can be
properly described as having a triple intermetallic bond, according
to the EAN formalism and to DFT calculations on the meth-
oxycarbyne complex [Mo2Cp2(l-COMe)(l-PCy2)(l-CO)] [12].
Therefore, a detailed structural discussion is not needed for com-
pound 5. We note, however, that its IR spectrum exhibits, in addi-
tion to the strong band characteristic of the C–O stretch of the
bridging carbonyl ligand (1684 cmꢀ1), a weak band due to the C–
O stretch of the acryloyl moiety (1743 cmꢀ1), these positions being
comparable to those measured for the benzoyl derivative
[Mo2Cp2{l-COC(O)Ph}(l-PCy2)(l-CO)] [2]. We also note that com-
pound 5 exhibits the same fluxional behavior observed for the al-
koxycarbyne complexes mentioned above, this involving the
rotation of the alkoxy group around the O–C(carbyne) bond, thus
creating an apparent symmetry plane relating both metal centers.
The most relevant NMR resonances are those arising from the
bridging
C atoms, which appear at 342.5 (carbyne) and
300.7 ppm (carbonyl), in positions comparable to those of the
mentioned alkoxycarbyne dimolybdenum complexes, whereas
the 1H and 13C NMR resonances arising from the acryloyl moiety
fall in the regions expected for organic acryloyl derivatives.
Scheme 3. Proposed pathways for the formation of the alkenyl complexes
(Mo = MoCp).
2
To our knowledge, the transformation of an allyl complex into
its alkenyl isomer through a 2,1-H shift has no precedent in the lit-
erature. Instead, the reverse process, that is, the isomerization of an
alkenyl complex to render the corresponding allyl isomer, is well
documented for mononuclear species [15], and there are also a
few examples involving dinuclear compounds. Thus, the photo-
2.6. Proposed mechanism for the reaction of complex 1 with allyl
chloride
The mechanism we propose for the formation of the alkenyl
derivatives 2a–c involves the coordination of the allyl group at
the dimetal center to form an intermediate allylic species C which
could not be detected (Scheme 3). We note, however, that a related
allyl-bridged product could be obtained and fully characterized
from the reaction of allyl chloride with the electron-precise binu-
chemical reactions of the hydrides [Mn2(
[MnMoCp( -H)( -PPh2)(CO)6] in the presence of 1-propyne have
been shown to yield the allyl compounds [Mn2(
3-C3H5)-
-PPh2)(CO)7] and [MnMoCp( -PPh2)(CO)5], respec-
3-C3H5)(
l-H)(l-PPh2)(CO)8] and
l
l
g
(l
g
l
clear anion [Fe2(l-SEt)(l
-CO)(CO)6]ꢀ [13]. Moreover, from our pre-
tively [16]. Although no vinyl precursor could be detected in the
latter reactions, the authors propose the occurrence of a 1,2-H shift
in a vinyl intermediate, ruling out the possibility of a 1,3-shift on
the basis of additional experiments using deuterated alkynes.
Finally, we can quote an example in which an allyl group eventu-
ally transforms into an alkenyl ligand, but possibly through an
vious studies on the reactions of 1 with MeI and PhCH2Cl to give
the corresponding agostic alkyl-bridged derivatives [14], we can
safely assume that such an intermediate is likely to have a transoid
arrangement of its CpMo(CO) fragments. This intermediate then
would undergo a 2,1-hydrogen shift giving rise to the alkenyl li-
gand present in the final products. Under this scheme, the reaction
with crotyl chloride should yield exclusively the dimethyl-substi-
tuted vinyl derivative 2c. As stated above, however, this reaction
gives a mixture of complexes 2c and 2b. To account for the forma-
tion of the isomer having an ethyl-substituted vinyl ligand (2b) in
this reaction we suggest that an isomerization in the allylic inter-
mediate (C to D) is taking place at some extent prior to the 2,1-shift
of the hydrogen atom.
1,3-shift, this occurring in the reaction of [Fe2(
(CO)6( -Ph2PCH2PPh2)] with Ph2PCH2CH@CH2 to
[Fe2( -PPh2)( -Ph2PCH2PPh2)] [17].
2-CHCHMe)(CO)6(
l
-CO)-
give
l
l
l-
g1
:g
l
2.7. Proposed mechanism for the reaction of compound 1 with acryloyl
chloride
As stated above, this is the only instance in which the anion 1
gives simultaneously products resulting in the attachment of a C-
based electrophile to either the metal center or to the oxygen atom
of the carbonyl ligand. As a result of this, a mixture of the vinyl
complex 2d and the carbyne complex 5 is obtained in the reaction
of 1 with acryloyl chloride (Scheme 4). The formation of the vinyl
complex requires the binding of the acryloyl fragment to the
molybdenum atoms, likely to give an a,b-unsaturated acyl-bridged
intermediate E, followed by decarbonylation to give a terminally-
bound vinyl intermediate F, which would finally rearrange into
Fig. 2. Extreme views of the binding of a l- :g
g2 3-allenyl ligand to a dimetal center.

M.A. Alvarez et al. / Journal of Organometallic Chemistry 694 (2009) 3864–3871
3869
vents were purified according to literature procedures, and
distilled prior to their use [20]. Tetrahydrofuran (THF) solutions
of the lithium salt of the anion [Mo2Cp2(l-PCy2)(l
-CO)2]ꢀ (1) were
prepared ‘‘in situ” as described previously [2,3], and all other re-
agents were obtained from the usual commercial suppliers and
used as received, unless otherwise stated. Petroleum ether refers
to that fraction distilling in the range 338–345 K. Filtrations were
carried out through diatomaceous earth. Low-temperature chro-
matographic separations were carried out using jacketed columns
refrigerated by a closed 2-propanol circuit kept at the desired tem-
perature with a cryostat, or by tap water. Commercial aluminum
oxide (activity I, 150 mesh) was degassed under vacuum prior to
use. The latter was mixed under nitrogen with the appropriate
amount of water to reach the activity desired. IR stretching fre-
quencies of CO ligands were measured in solution (using CaF2 win-
dows) and are referred to as
(NMR) spectra were routinely recorded at 300.13 (1H), 121.50
31P{1H}) or 75.47 MHz (13C{1H}) at 290 K in CD2Cl2 solutions un-
m(CO). Nuclear Magnetic Resonance
(
less otherwise stated. Chemical shifts (d) are given in ppm, relative
to internal tetramethylsilane (1H, 13C) or external 85% aqueous
H3PO4 solutions (31P). Coupling constants (J) are given in Hertz.
The metal-bound carbon atoms of the alkenyl ligands are referred
to as C and Cb, with C corresponding to the bridgehead carbon
a
a
atom, and the corresponding H atoms are labeled analogously.
3.1. Preparation of trans-[Mo2Cp2(l- :g l-PCy2)(CO)2]
g1 2-CMeCH2)(
(2a)
An excess of allyl chloride (0.1 mL, 1.2 mmol) was added to a
solution of 1 (Li+ salt, ca. 0.1 mmol) in THF (10 mL) and the mixture
was stirred for 30 min at room temperature to yield a red solution.
After removal of the solvent under vacuum, the residue was ex-
tracted with toluene and the extract was filtered through diatoma-
ceous earth. The solvent was removed again under vacuum, the
residue was then extracted with CH2Cl2–petroleum ether (1:4)
and the extracts were chromatographed through an alumina col-
umn (activity IV) at 253 K. Elution with the same solvent mixture
gave a red fraction (yellow-greenish in the column) which yielded,
after removal of solvents under vacuum, compound 2a as an or-
ange-yellow air-sensitive solid (0.028 g, 45%). Anal. Calc. for
C27H37Mo2O2P: C, 52.60; H, 6.05. Found: C, 52.36; H, 6.29%. 1H
NMR: d 5.36, 5.31 (2 ꢂ s, Cp, 2 ꢂ 5H), 5.07, 4.68 (2 ꢂ d, JHH = 2.6,
CH2, 2 ꢂ 1H), 2.27 (s, CH3, 3H), 2.10–1.00 (m, Cy, 22H). 13C{1H}
NMR (213 K): d 250.0 (d, JCP = 14, CO), 237.9 (d, JCP = 13, CO),
Scheme 4. Reaction pathways of the anion 1 with acryloyl chloride (Mo = MoCp).
the more stable vinyl-bridged geometry. In the second case, the SN
reaction would take place at the hardest nucleophilic site of the
anion, located at the oxygen atom of the bridging CO ligands. There
are some reports in the literature where decarbonylation have
been observed or proposed to occur in
bridged complexes. For instance, the thermolysis of the diiron acyl
complexes [Fe2(CO)4{ -PPh2)( -dppm)] has been
-C(O)CR@CHR0}(
shown to give the corresponding alkenyl derivatives [Fe2(CO)4(
CR=CHR’)(
-dppm)] (R, R0 = H, Ph) [18]. A similar process is
proposed to occur spontaneously in the reaction of the anionic
compounds [Mo2Cp2(
-PPhR)(CO)4]ꢀ (R = H, Ph) with acryloyl
a,b-unsaturated acyl-
l
l
l
l-
l
l
chloride. In this case, a vinyl intermediate might be also involved
174.6 (s, C ), 90.0, 89.0 (2 ꢂ s, Cp), 79.3 (s, Cb), 44.8 (d, JCP = 21,
a
but was not detected, and the products obtained are the phos-
C1–Cy), 42.5 (d, JCP = 17, C1–Cy), 38.7 (s, CH3), 34.4, 33.9, 32.5,
31.7 (4 ꢂ s, C2–Cy), 28.2 (d, JCP = 12, C3–Cy), 28.1 (d, JCP = 13,
C3–Cy), 27.9 (d, JCP = 12, C3–Cy), 27.7 (d, JCP = 11, C3–Cy), 26.3 (s,
2 ꢂ C4–Cy).
phaalkene complex [Mo2Cp2(l- :g
j1 2-PhP@CHMe)(CO)4] and the
alkenylphosphine complex [Mo2Cp2(
l- :g
j1 2-Ph2PCH@CH2)(CO)4],
respectively [19].
In summary, we have shown that the unsaturated anion 1 re-
acts with b, -unsaturated organic chlorides to give products of
c
3.2. Reaction of compound 1 with crotyl chloride
nucleophilic substitution mainly involving the dimetal site, while
the electron-transfer processes are almost absent in these reac-
tions. The high unsaturation of the dimetal center in 1 allows
and induces different rearrangements in the incoming electro-
phile: In the reaction with allyl halides, a rare 2,1-H shift to give
the corresponding alkenyl derivatives is observed. In the reaction
with acryloyl chloride, decarbonylation takes place to give a vinyl
derivative. The latter reaction is a unique case in which both nucle-
ophilic sites of the anion (Mo and O atoms) are involved to bind the
incoming electrophile.
An excess of crotyl chloride (0.1 mL, 0.98 mmol) was added to a
solution of 1 (Li+ salt, ca. 0.1 mmol) in THF (10 mL) and the mixture
was stirred for 10 min at room temperature to yield a red solution
containing a 3:2 mixture of the compounds trans-[Mo2Cp2(
2-CEtCH2)
-PCy2)(CO)2] (2b) and trans-[Mo2Cp2(
CMeCHMe)(
l
-
-
g1
:g
l
l- :
g1 g2
l
-PCy2)(CO)2] (2c). After removal of the solvent under
vacuum, the residue was extracted with toluene (2 ꢂ 7 mL) and fil-
tered through diatomaceous earth. Workup as described for 2a
gave a 3:2 mixture of compounds 2b and 2c as an orange-yellowish
air-sensitive solid (0.035 g, 54%). Anal. Calc. for C28H39Mo2O2P: C,
53.34; H, 6.24. Found: C, 52.95; H, 5.98%. 1H NMR data for 2b: d
5.35, 5.31 (2 ꢂ s, Cp, 2 ꢂ 5H), 5.03, 4.76 (2 ꢂ d, JHH = 2, EtC = CH2,
2 ꢂ 1H), 2.68, 2.04 (2 ꢂ dq, JHH = 14, 7, CH3CH2C@CH2, 2 ꢂ 1H),
1.15 (t, JHH = 7, CH3CH2C@CH2, 3H). The resonances due to the H
3. Experimental
All manipulations and reactions were carried out under a nitro-
gen (99.995%) atmosphere using standard Schlenk techniques. Sol-

3870
M.A. Alvarez et al. / Journal of Organometallic Chemistry 694 (2009) 3864–3871
atoms of the Cy group are overlapping with those of the isomer 2c
(2.40–1.10 ppm). 1H NMR data for 2c: d 6.17 (q, JHH = 5.5, CHMe,
1H), 5.29, 5.20 (2 ꢂ s, Cp, 2 ꢂ 5H), 2.10 (s, CH3C, 3H), 1.91 [d,
JHH = 5.5, CH(CH3), 3H]. The resonances due to the H atoms of the
Cy group are overlapping with those of the isomer 2b (2.40–
1.10 ppm).
3.5. Preparation of trans-[Mo2Cp2{l- :g l-PCy2)(CO)2]
g2 3-CH2CCH)}(
(4)
Propargyl chloride (50 lL, 70% w/w in toluene, 0.45 mmol) was
added to a solution of 1 (Li+ salt, ca. 0.07 mmol) in THF (10 mL), and
the mixture was stirred for 2 h at room temperature to give an or-
ange solution containing compound 4 as the major product, along
with minor amounts of another compound that could not be iso-
lated or purified. After removal of the solvent, the residue was ex-
tracted with CH2Cl2–petroleum ether (1:4) and the extracts were
chromatographed through alumina (activity IV) at 253 K. Elution
with the same solvent mixture gave an orange fraction which
yielded, after removal of solvents, compound 4 as an orange solid
(0.030 g, 70%). Anal. Calc. for C27H35Mo2O2P: C, 52.78; H, 5.74.
Found: C, 52.56; H, 5.82%. 1H NMR: d 5.06, 4.98 (2 ꢂ s, Cp,
2 ꢂ 5H), 4.72 (ddd, JPH = 3.5, JHH = 1.5, 1.1, CH, 1H), 4.17 (t,
JPH = JHH = 1.5, CH2, 1H), 4.00 (t, JPH = JHH = 1.1, CH2, 1H), 2.20–1.10
(m, Cy, 22H). 13C{1H} NMR: d 244.4 (d, JCP = 11, CO), 236.0 (d,
JCP = 8, CO), 112.5 (s, CH2CCH), 91.0, 87.2 (2 ꢂ s, Cp), 68.9
(s, CH2CCH), 61.0 (d, JCP = 21, CH2CCH), 51.2 (d, JCP = 15, C1–Cy),
47.3 (d, JCP = 10, C1–Cy), 35.4 (d, JCP = 5, C2–Cy), 35.3 (d, JCP = 4,
C2–Cy), 34.9 (d, JCP = 1, C2–Cy), 34.8 (d, JCP = 1, C2–Cy), 28.8 (d,
JCP = 10, C3–Cy), 28.7 (d, JCP = 12, C3–Cy), 28.6, 28.5 (2 ꢂ d,
JCP = 10, 2 ꢂ C3–Cy), 26.8, 26.7 (2 ꢂ d, JCP = 1, 2 ꢂ C4–Cy).
3.3. Reaction of compound 1 with acryloyl chloride
Neat acryloyl chloride (20 lL, 0.25 mmol) was added to a solu-
tion of 1 (Li+ salt, ca. 0.1 mmol) in THF (10 mL) and the mixture was
stirred for 5 min at room temperature to give a deep red solution
containing a 1:1 mixture of the complexes trans-[Mo2Cp2(
2-CHCH2)(
-PCy2)(CO)2] (2d) and [Mo2Cp2( -PCy2){ -CO-
C(O)CH@CH2}( -CO)] (5). After removal of the solvent under
l-
g1
:g
l
l
l
l
vacuum, the residue was extracted with CH2Cl2–petroleum ether
(1:4) and the extracts were chromatographed through alumina
(activity IV) at 285 K. Elution with the same solvent mixture gave
a green fraction, and further elution with neat dichloromethane
gave a red fraction. Removal of solvents from the first fraction
yielded compound 2d as a yellow-greenish solid (0.027 g, 45%),
and compound 5 was analogously obtained as a red solid from
the second fraction (0.025 mg, 40%). Selected data for compound
2d: Anal. Calc. for C26H35Mo2O2P: C, 51.84; H, 5.86. Found: C,
51.96; H, 6.09%. 1H NMR: d 8.56 (ddd, JPH = 1, JHH = 12, 9, H , 1H),
a
3.6. X-ray structure determination of compound 3
5.39, 5.33 (2 ꢂ s, Cp, 2 ꢂ 5H), 5.28 (dd, JHH = 12, 3, Hb, 1H), 4.91
(dd, JHH = 9, 3, Hb, 1H), 2.80–0.90 (m, Cy, 22H). 13C{1H} NMR
(C6D6): d 252.2 (d, JCP = 13, CO), 236.3 (d, JCP = 13, CO), 153.2 (s,
The X-ray intensity data for compound 3 were collected on a
Smart-CCD-1000 BRUKER diffractometer using graphite-mono-
chromated Mo Ka radiation at 120 K. Cell dimensions and orienta-
tion matrixes were initially determined from least-squares
C ), 89.5, 89.2 (2 ꢂ s, Cp), 84.2 (s, Cb), 45.4 (d, JCP = 20, C1–Cy),
a
45.3 (d, JCP = 18, C1–Cy), 34.7, 34.2 (2 ꢂ d, JCP = 3, 2 ꢂ C2–Cy), 33.0,
32.9 (2 ꢂ s, 2 ꢂ C2–Cy), 28.4 (d, JCP = 13, 2 ꢂ C3–Cy), 28.3 (d,
JCP = 10, C3–Cy), 28.1 (d, JCP = 11, C3–Cy), 26.5, 26.4 (2 ꢂ s, C4–Cy).
Selected data for compound 5: Anal. Calc. for C27H35Mo2O3P: C,
51.44; H, 5.60. Found: C, 51.26; H, 5.85%. 1H NMR: d 6.44 (dd,
refinements of reflections measured in three sets of 30 exposures
collected in three different
x regions and eventually refined
against all reflections. The software SMART [21] was used for collect-
ing frames of data, indexing reflections, and determining lattice
parameters. The collected frames were then processed for integra-
tion by the software SAINT [21], and a multi-scan absorption
JHH = 17, 1.5, Hb, 1H), 6.12 (dd, JHH = 17, 10, H , 1H), 5.93 (dd,
a
JHH = 10, 1.5, Hb, 1H), 5.82 (s, Cp, 10H), 2.80–0.40 (m, Cy, 22H).
13C{1H} NMR: d 342.5 (d, JCP = 17,
l-COR), 300.7 (d, JCP = 9, CO),
159.7 [s, C(O)R], 132.4 (s, Cb), 128.5 (s, C ), 95.7 (s, Cp), 41.8 (d,
a
JCP = 18, C1–Cy), 41.5 (d, JCP = 19, C1–Cy), 33.6, 33.2 (2 ꢂ s, C2–Cy),
27.6 (d, JCP = 13, C3–Cy), 27.5 (d, JCP = 12, C3–Cy), 26.4, 26.3 (2 ꢂ s,
C4–Cy).
Table 3
Crystal data for compound 3.
Molecular formula
Molecular weight
Crystal System
Space group
Radiation (k, Å)
a (Å)
C27H35Mo2O3P
630.40
monoclinic
P21/c
0.71073
10.820(2)
12.901(2)
18.133(4)
90
91.810(3)
90
2529.9(8)
3.4. Preparation of cis-[Mo2Cp2(l- :g l-PCy2)(CO)3] (3)
g1 2-CHCH2)(
A Schlenk flask containing compound 2d (0.027 g 0.045 mmol)
was filled with CO. Dichloromethane (8 mL) was then added, and
the mixture was stirred at room temperature for 1 h to give an or-
ange solution. After removal of the solvent under vacuum, the res-
idue was extracted with CH2Cl2–petroleum ether (1:4) and the
extracts were chromatographed through alumina (activity IV) at
285 K. Elution with the same solvent mixture gave an orange frac-
tion which yielded, after removal of solvents, compound 3 as an or-
ange solid (0.022 g, 78%). The crystals of 3 used in the X-ray
diffraction study were grown by the slow diffusion of a layer of
petroleum ether into a concentrated solution of the compound in
toluene at 253 K. Anal. Calc. for C27H35Mo2O3P: C, 51.44; H, 5.60.
Found: C, 51.17; H, 5.92%. 1H NMR (CDCl3): d 8.93 (td, JHH = 9,
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
Z
4
DCalc (g cmꢀ3
)
1.655
1.081
120
1.88–26.41
Absorption coefficient (mmꢀ1
T (K)
)
h range (°)
Index ranges (h, k, l)
Reflections collected
Independent reflection
Reflection with I > 2
R indexes (I > 2
(I))a
R indexes (all data)a
ꢀ13, 13; 0, 16; 0, 22
21417
5181 [Rint = 0.0264]
4595
r(I)
JPH = 1, H , 1H), 5.16, 5.15 (2 ꢂ s, Cp, 2 ꢂ 5H), 3.34 (d, JHH = 9, Hb,
a
r
R1 = 0.0192, wR2 = 0.0472b
R1 = 0.0238, wR2 = 0.0490b
1.074
1H), 2.70–0.20 (m, Cy, 22H), 1.07 (d, JHH = 9, Hb, 1H). 13C{1H} NMR
(CDCl3): d 242.3 (d, JCP = 23, CO), 239.6 (d, JCP = 20, CO), 237.3 (d,
Goodness-of-fit (GOF)
Restraints/parameters
0/438
0.382, ꢀ0.407
JCP = 1, CO), 148.2 (d, JCP = 9, C ), 92.9, 91.0 (2 ꢂ s, Cp), 59.1 (d,
a
D
q
(max., min.) (e Åꢀ3
)
JCP = 11, C1–Cy), 46.6 (s, C2–Cy), 42.2 (d, JCP = 17, C1–Cy), 36.8 (d,
JCP = 2, C2–Cy), 32.8 (s, C2–Cy), 32.7 (d, JCP = 6, Cb), 29.1 (d, JCP = 11,
C3–Cy), 28.3 (d, JCP = 8, C3–Cy), 28.2 (s, C2–Cy), 27.9 (d, JCP = 11,
C3–Cy), 27.3 (d, JCP = 13, C3–Cy), 26.5, 26.0 (2 ꢂ s, C4–Cy).
a
R1
=
R
||Fo| ꢀ |Fc||/
R
|Fo|. wR2 = [
R
w(|Fo|2 ꢀ |Fc|2)2/
R
w|Fo|2]1/2
;
w = 1/[r
2(F2o) +
(aP)2 + bP] where P = (Fo2 þ 2Fc2)/3.
b
a = 0.0224, b = 1.4423.

M.A. Alvarez et al. / Journal of Organometallic Chemistry 694 (2009) 3864–3871
3871
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on F2 with SHELXL97 [24]. All non-hydrogen atoms were refined
anisotropically. All hydrogen atoms were located in the Fourier
map and were given an overall isotropic thermal parameter. Crys-
tallographic data and structure refinement details for compound 3
are collected in Table 3.
Acknowledgments
(c) H. El Amouri, J. Vaissermann, Y. Besace, K.P.C. Vollhardt, G.E. Ball,
Organometallics 12 (1993) 605;
We thank the MEC of Spain for a grant (to A.R.) and financial
support (projects BQU2003-05471 and CTQ2006-01207/BQU).
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Appendix A. Supplementary material
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CCDC 740498 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via http://www.ccdc.ca-
m.ac.uk/data_request/cif. Supplementary data associated with this
article can be found, in the online version, at doi:10.1016/
j.jorganchem.2009.08.003.
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