Reaction of metal carbonyl anions with electrophilic alkynes: Synthesis of isomeric η3-acryloyl and σ-vinyl complexes

Article abstract of DOI:10.1016/j.jorganchem.2007.11.059

Treatment of the metal carbonylate anions [CpMo(CO)₂(L)]^- (Cp = η-C₅H₅; L = PPh₂Me, PPh₂Et) with the electrophilic alkynes methyl propiolate or DMAD (RC{triple bond, long}CCO₂Me, where R = H or CO₂Me, respectively) followed by protonation affords the η³-acryloyl (1-oxoallyl) complexes [CpMo(η³-COCR{double bond, long}CHCO₂Me)(CO)(L)] (3a-d) as the major products, together with the isomeric vinyl complexes trans-[CpMo(CR{double bond, long}CHCO₂Me)(CO)₂(L)] (4a-d). On the basis of the regioselectivity of the reaction, it is proposed that nucleophilic attack of the carbonylate anion occurs at the alkyne carbon bearing R; migration of the anionic vinyl ligand to a CO followed by protonation gives 3, whereas protonation without insertion gives 4. The X-ray structures of the acryloyl complex [CpMo(η³-COCH{double bond, long}CHCO₂Me)(CO)(PPh₂Me)] (3b) and its vinyl isomer [CpMo(σ-CH{double bond, long}CHCO₂Me)(CO)₂(PPh₂Me)] (4b) have been determined.

Full text of DOI:10.1016/j.jorganchem.2007.11.059

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 693 (2008) 709–716
www.elsevier.com/locate/jorganchem
Reaction of metal carbonyl anions with electrophilic alkynes:
Synthesis of isomeric g3-acryloyl and r-vinyl complexes
´
Harry Adams, Peter Blenkiron, Louise J. Gill, Raoul Herve, Anne-Go¨nke Huesmann,
Michael J. Morris *
Department of Chemistry, University of Sheffield, Sheffield S3 7HF, UK
Received 30 October 2007; received in revised form 27 November 2007; accepted 29 November 2007
Available online 8 December 2007
Abstract
Treatment of the metal carbonylate anions [CpMo(CO)2(L)]À (Cp = g-C5H5; L = PPh2Me, PPh2Et) with the electrophilic alkynes
methyl propiolate or DMAD (RC„CCO2Me, where R = H or CO2Me, respectively) followed by protonation affords the g3-acryloyl
(1-oxoallyl) complexes [CpMo(g3-COCR@CHCO2Me)(CO)(L)] (3a–d) as the major products, together with the isomeric vinyl com-
plexes trans-[CpMo(CR@CHCO2Me)(CO)2(L)] (4a–d). On the basis of the regioselectivity of the reaction, it is proposed that nucleo-
philic attack of the carbonylate anion occurs at the alkyne carbon bearing R; migration of the anionic vinyl ligand to a CO followed
by protonation gives 3, whereas protonation without insertion gives 4. The X-ray structures of the acryloyl complex [CpMo
(g3-COCH@CHCO2Me)(CO)(PPh2Me)] (3b) and its vinyl isomer [CpMo(r-CH@CHCO2Me)(CO)2(PPh2Me)] (4b) have been determined.
Ó 2007 Elsevier B.V. All rights reserved.
Keywords: Molybdenum; Phosphine; Acryloyl; Vinyl; Migratory insertion
1. Introduction
The nucleophilic properties of metal carbonyl anions
make them an invaluable synthetic tool for the organome-
tallic chemist, allowing access to alkyl and acyl complexes
through reaction with organic halides, and to compounds
with metal–element bonds by reaction with main group
or transition metal halides. A series of papers by Beck
and co-workers described the attack of metal carbonyl
anions on (usually cationic) complexes with p-bound
ligands such as alkenes, alkynes and arenes, leading in
favourable cases to hydrocarbon-bridged species [2]. In
contrast, the reactions of metal carbonyl anions with
uncomplexed alkynes appear to be limited to only a few
examples. For example, Mitsudo and co-workers showed
that [PPN][FeH(CO)4] reacted with activated alkynes
RC„CCO2Me (R = H, CO2Me) to give the acryloyl com-
plexes [PPN][Fe{COC(CO2Me)@CHR}(CO)3] by insertion
of the alkyne into the metal–hydride bond followed by
vinyl to carbonyl migration [3]. Wojcicki has reported that
Na[Re(CO)5] reacts with RC„CCO2Me (R = H, Me,
CO2Me) to give initially anionic metallacyclobutenones,
The formation of a carbon–carbon bond between a
coordinated organic fragment and a carbonyl ligand by
migratory insertion is one of the cornerstones of organo-
metallic chemistry, and forms a key step in many industrial
processes [1]. Because (at least in part) of the increased
metal–carbon bond strength, migratory insertion reactions
involving M–C(sp2) or M–C(sp) bonds are less common
than those of simple alkyl groups and consequently exam-
ples of the insertion of CO into metal-vinyl or metal-
acetylide bonds are comparatively rare. As a result the
chemistry of complexes containing the acryloyl (vinylacyl)
ligand (g1- or g3-COCH@CH2) remains relatively
unexplored.
*
Corresponding author. Tel.: +44 0114 2229363; fax: +44 0114
2229346.
E-mail address: M.Morris@sheffield.ac.uk (M.J. Morris).
0022-328X/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.11.059

710
H. Adams et al. / Journal of Organometallic Chemistry 693 (2008) 709–716
which can be alkylated at oxygen to give rhenacyclobutadi-
enes [4]. Most relevantly Lee et al. have found that the
reaction of [CpM(CO)3]À (M = Mo, W) with HC„CCOMe
in a THF/MeOH/H2O solvent mixture afforded initially
the vinyl complexes [CpM(CO)3(CH@CHCOMe)] which
then underwent carbonylation to the cyclic lactone
[CpM(CO)2{g3-CHCHC(Me)OCO}]; an g3-acryloyl com-
plex was implicated in this process but not isolated [5].
We have previously reported that the anion
[CpMo(CO)2(PPh2COMe)]À, prepared by deprotonation
of [CpMo(CO)2(PPh2H)(COMe)] at room temperature
(which induces a migration of the acyl group from molyb-
denum to phosphorus) reacts with RC„CCO2Me (R = H,
CO2Me) to give the acryloyl complexes [CpMo(CO)(PPh2-
COMe)(g3-COCR@CHCO2Me)] together with much
lower yields of associated vinyl complexes [6]. We therefore
sought to establish whether this was a general reaction of
substituted carbonyl anions of the type [CpMo(CO)2(L)]À
with tertiary phosphine ligands, and in this paper we report
our results which show that this is indeed the case.
2.2. Reaction with activated alkynes
Addition of a slight excess of the activated alkyne to
solutions of anions 1a or 1b causes an immediate darkening
in colour in the case of DMAD, and a somewhat slower
reaction (about 10 min) for methyl propiolate. In each case
protonation with a weak acid (in this work [Et2NH2][Br]
was routinely used as it was found to give the cleanest reac-
tion) yielded two products that could be separated by col-
umn chromatography (Scheme 1). The lowest yields of
both products were found in the reaction of the least nucle-
ophilic anion (L = PPh2Me) with the least electrophilic
alkyne (methyl propiolate).
The major products were the g3-acryloyl complexes
[CpMo(g3-COCR@CHCO2Me)(CO)(L)] (3a–d), produced
in ca. 50% yield as orange, air-stable crystalline solids dis-
playing a single strong terminal m(CO) peak in their IR
spectra, together with weaker peaks due to the acryloyl car-
1
bonyl and the ester groups. Their H NMR spectra are
unremarkable but in the case of the complexes derived
from methyl propiolate, show that the carbonyl group of
the acryloyl ligand is joined to the CH terminus of the
alkyne, and the magnitude of the J(HH) coupling constant
indicates that the two protons of the acryloyl ligand are in
a cis conformation. The distinguishing feature in the spec-
troscopic data of 3 is the peak at approximately 250 ppm in
the 13C NMR spectrum due to the carbonyl of the g3-acry-
loyl unit; this carbon atom also shows coupling to the 31P
nucleus of the phosphine whereas the other two acryloyl
carbons, which occur at unusually low chemical shifts
(25–45 ppm) do not.
2. Results and discussion
2.1. Anion synthesis
The substituted carbonyl anions [CpMo(CO)2(L)]À 1a
(L = PPh2Me) and 1b (L = PPh2Et) were conveniently pre-
pared in THF solution in one of two ways. The first method
was that used previously by us, involving cleavage of the
corresponding substituted dimers [Cp2Mo2(CO)4L2] with
sodium amalgam; these dimers were prepared in ca. 75%
yield by addition of two equiv. of L to [Cp2Mo2(CO)4],
made in situ from [Cp2Mo2(CO)6] [7,8]. However an
alternative route was also used in this work, in which
[Cp2Mo2(CO)6] was first cleaved with iodine to give
[CpMo(CO)3I], followed by substitution with L in the pres-
ence of Me3NO to give [CpMo(CO)2(L)I] 2a, 2b. Although
2a has been previously mentioned in a paper and a patent
[9], no preparative details or characterising data have
previously been published for either of these compounds;
therefore we include them in Section 5. Sodium amalgam
reduction of these iodide complexes provided the requisite
anions. The advantages of this second route are that both
of the reactions to prepare [CpMo(CO)2(L)I] are rapid, in
contrast to the overnight reflux required for the generation
of [Cp2Mo2(CO)4], and secondly the generation of the anion
is also more rapid, probably due to the greater solubility of
the phosphine iodide complexes compared to the dimers.
The overall yield of both methods is comparable.
A number of related acryloyl complexes of Group 6
metals are known. While this work was in progress, Lin
In this paper, we restrict ourselves to discussion of the
complexes with L = PPh2Me and PPh2Et, but in principle
L can be any tertiary phosphine ligand. We have shown
that the reaction below also works for L = PPh3 and
PnBu3; however in the former case the relative insolubility
of [Cp2Mo2(CO)4(PPh3)2] resulted in lower yields, and in
the latter case oily products were formed which could not
be isolated as analytically pure materials.
Scheme 1. Synthesis of the g3-acryloyl and r-vinyl complexes.

H. Adams et al. / Journal of Organometallic Chemistry 693 (2008) 709–716
711
and co-workers reported a similar reaction between
Li[CpMo(CO)2(PPh3)] (prepared in this instance from
[CpMo(CO)2(PPh3)I] by treatment with BuLi) and methyl
propiolate to afford the analogous acryloyl complex
[CpMo (g3-COCH@CHCO2Me)(CO)(PPh3)] [5]. The
unsubstituted acryloyl [CpMo(g3-COCH@CH2)(CO)
(PPh3)] was prepared by decomposition of the alkyl
complex [CpMo{CHMe(OMe)}(CO)2(PPh3)] with loss of
MeOH, a reaction which also involves vinyl-to-carbonyl
migration [10]. Similar treatment of the tungsten
analogue produced exclusively the isomeric vinyl complex
[CpW(r-CH@CH2)(CO)2(PPh3)] instead. Some years ago,
Guerchais and co-workers reported that the photochemical
reaction of [CpM(CO)3H] (M = Mo, W) with hexafluoro-
is again regioselective. The magnitude of the J(HH) cou-
pling constants in these two compounds (16.8 Hz in 4b,
16.5 Hz in 4d) indicates a trans-disposition of the two
hydrogens across the vinylic double bond, as opposed to
the cis arrangement seen in 3. In the 13C NMR spectra,
the a-carbon of the vinyl group appears at approximately
180 ppm, with the b-carbon at approximately 130 ppm
(in some cases the latter is hidden by the phenyl reso-
nances). In the 31P NMR spectra, it is noticeable that the
signals for the vinyl complexes appear at higher chemical
shift than those of the isomeric acryloyls, with the differ-
ence being approximately 20 ppm for L = PPh2Me and
about 10 ppm for L = PPh2Et.
The proposed mechanism for the reaction is shown in
Scheme 2. Initial nucleophilic attack of the carbonylate
anion occurs regioselectively at the alkyne terminus which
bears the R group; protonation of this anionic intermediate
produces the vinyl complexes 4. However it can also
undergo a migratory insertion to give a r-COCR@
CCO2MeÀ group, which on protonation forms the
g3-COCR@CHCO2Me ligand in complexes 3. Since vinyl
complexes 4 are stable and do not rearrange to 3 at room
temperature, the migration reaction must occur while the
ligand is still in the anionic state. In order to explain the
observed stereochemistry, the migration reaction of
the intermediate in which the R and CO2Me groups are
situated trans to each other, leading to the acryloyl, would
have to be faster than that of the intermediate in which
they are cis to each other. It is not immediately obvious
why this should be so, though one possibility might be
the temporary coordination of a CO2Me lone pair to the
metal which might assist the CO migration.
but-2-yne
produced
the
acryloyl
complexes
[CpM(CO)2{g3-COC(CF3)@CHCF3}], which could be
converted into their r-vinyl isomers [CpM(CO)3
{r-C(CF3)@CHCF3}] by heating; photolysis reversed this
transformation [11]. Reaction of the tungsten acryloyl
complex with phosphine ligands afforded [CpW(CO)(L)
{COC(CF3)@CHCF3}] (L = PPh3, P(OMe)3, PMe3,
PMe2Ph), with the organic ligand remaining intact; these
substituted acryloyls could also be interconverted with
their vinyl isomers [CpW(CO)2(L){r-C(CF3)@CHCF3}].
Similar acryloyl complexes were prepared by Brix and Beck
from the alkyne HC„CNEt2 [12]. However photochemical
reactions of [CpM(CO)3R] (R = H, alkyl) with other
alkynes R1C„CR2 are known to lead to cyclic alkenylke-
tone complexes of the type [CpM(CO)2(CR1@CR2
CR@O)], which have been studied in detail by Alt [13].
The minor product of each reaction was the correspond-
ing vinyl complex trans-[CpMo(r-CR@CHCO2Me)
(CO)2(L)] (4a–d), i.e. the isomers of 3a–d. Their IR spectra
show the two-peak pattern typical of a trans dicarbonyl
geometry. Those derived from methyl propiolate show a
low-field signal due to the a-CH proton in their 1H
NMR spectra (coupled to the other vinylic proton and
the phosphine ligand) and demonstrating that the reaction
However we can also not rule out a mechanism in which
CO insertion occurs in all cases to give an acryloyl ligand,
but on protonation only those molecules which have a cis-
arrangement of the two original alkyne substituents (i.e. in
the case of methyl propiolate, a trans-arrangement of the
two hydrogens) undergo a subsequent de-insertion to give
Scheme 2. Proposed mechanism of the reaction.

712
H. Adams et al. / Journal of Organometallic Chemistry 693 (2008) 709–716
the vinyl complex. This would also explain the differing ste-
reochemistries of the two products. Careful examination of
the chemical shifts of the other reported complexes of this
type [11] suggests that the disubstituted acryloyl complexes
(containing COCR@CHR groups) all share the same ste-
reochemistry in which the R groups are trans to each other,
and inspection of the structure of 3b below suggests that
having the substituent on the terminal carbon pointing
down towards the phosphine ligand might be sterically
unfavourable.
It is notable that the regiochemistry of the linking of the
CO and alkyne ligands is different to that observed by Mit-
sudo [3] and Wojcicki [4]. In these cases, the CCO2Me-ter-
minus of methyl propiolate becomes attached to the CO; in
the latter case this was explained by a mechanism involving
nucleophilic attack of this b-carbon on the carbonyl ligand.
In our work it is the CH-terminus which becomes linked to
the CO; assuming that the initial nucleophilic attack is reg-
iospecific (as we would expect from previous work, and
from the regiochemistry of 4) this implies a migratory
insertion of CO into the metal-a-C bond. The synthesis
of the unsubstituted acryloyl [CpMo(g3-COCH@CH2)
(CO)(PPh3)] was proposed to occur by a similar vinyl to
CO migration [10].
As mentioned above, Lin and co-workers also explored
the reaction of the unsubstituted anion [CpW(CO)3]À with
methyl propiolate and DMAD, and discovered that it gave
exclusively the vinyl complexes [CpW(CO)3(r-CR@
CHCO2Me)] (R = H, CO2Me) [5]. When we treated
[CpMo(CO)3]À with DMAD in a similar manner, an imme-
diate reaction of the two compounds occurred, but on addi-
tion of H+, the only isolated product was [Cp2Mo2(CO)6].
It appears that the r-vinyl complexes of tungsten may
be rather more stable than those of molybdenum.
Fig. 1. Molecular structure of complex 3b in the crystal (50% probability
ellipsoids).
Table 1
˚
Selected bond lengths (A) and angles (°) for complex 3b
Mo(1)–C(1)
Mo(1)–C(8)
Mo(1)–P(1)
O(2)–C(7)
C(8)–C(9)
1.944(8)
2.291(6)
2.5002(19)
1.206(8)
1.435(9)
Mo(1)–C(7)
Mo(1)–C(9)
O(1)–C(1)
C(7)–C(8)
2.106(6)
2.304(6)
1.178(8)
1.448(9)
C(1)–Mo(1)–C(7)
C(7)–Mo(1)–C(8)
C(7)–Mo(1)–C(9)
C(1)–Mo(1)–P(1)
C(8)–Mo(1)–P(1)
C(9)–C(8)–C(7)
78.4(3)
38.2(2)
66.0(2)
82.7(2)
90.21(18)
113.3(6)
C(1)–Mo(1)–C(8)
C(1)–Mo(1)–C(9)
C(8)–Mo(1)–C(9)
C(7)–Mo(1)–P(1)
C(9)–Mo(1)–P(1)
86.1(2)
118.9(2)
36.4(2)
125.40(19)
80.17(18)
Me)(CO)2(PPh2Me)] (4b), shown in Fig. 2 with details
given in Table 2. The trans orientation of the two carbonyl
ligands and the trans arrangement of the two vinylic hydro-
gens were both confirmed. The Mo(1)–C(21) bond length
3. Crystal structure determinations
˚
of 2.173(6) A and the C(21)–C(22) bond length of
The crystal structure of [CpMo(g3-COCH@CHCO2-
Me)(CO)(PPh2Me)] (3b) has been determined and is shown
in Fig. 1, with selected bond lengths and angles collected in
Table 1. The bond lengths within the CpMo(CO)(PPh2Me)
unit all lie within the usual ranges and require little com-
ment. In the g3-acryloyl ligand, the carbonyl carbon is sit-
uated trans to the phosphine ligand (in keeping with the
observation of 31P coupling to this carbon in the 13C
NMR spectrum) and forms the shortest bond to the molyb-
˚
1.325(10) A are both comparable to the corresponding dis-
tances in other structurally characterised molybdenum
vinyl species such as [CpMo(r-CH@CHtBu){P(OMe)3}3]
and [CpMo(r,g2-CPh@CPhCH2CH@CH2){P(OMe)3}2]
[14]. The vinylic bond length is longer than the average
˚
C@C bond length of 1.26 A observed in the two indepen-
˚
denum atom [Mo(1)–C(7) 2.106(6) A], whereas the other
˚
two carbons are equidistant [Mo(1)–C(8) 2.291(6) A;
˚
Mo(1)–C(9) 2.304(6) A]. The corresponding distances in
the unsubstituted complex [CpMo(g3-COCH@CH2)
˚
(CO)(PPh3)] were 2.105(28), 2.339(28) and 2.349(28) A
[10]. The carbon–carbon distances in the acryloyl ligand
˚
of 3b are of equal length [C(7)–C(8), 1.448(9) A and
˚
C(8)–C(9), 1.435(9) A], emphasising the validity of the
alternative 1-oxoallyl bonding description.
We also carried out a crystal structure determination of
the isomeric vinyl complex trans-[CpMo(r-CH@CHCO2-
Fig. 2. Molecular structure of complex 4b in the crystal (50% probability
ellipsoids).

H. Adams et al. / Journal of Organometallic Chemistry 693 (2008) 709–716
713
alent of PPh2Me (0.17 cm3, 0.912 mmol) was added, fol-
lowed by a slight excess of anhydrous Me3NO (80.4 mg,
1.07 mmol). After stirring for 90 min, no starting material
remained as shown by the IR spectrum of an aliquot of
the solution; the solvent was removed. Column chromatog-
raphy of the residue produced a single red band, eluted
with dichloromethane-light petroleum (2:3), which yielded
an orange-red powder of [CpMo(CO)2(PPh2Me)I]
(453.7 mg, 91%). The compound exists as a mixture of
trans and cis isomers in a ratio of 2:1 [18].
Table 2
Selected bond lengths (A) and angles (°) for complex 4b
˚
Mo(1)–C(1)
Mo(1)–C(21)
O(1)–C(1)
1.963(6)
2.173(6)
1.157(7)
1.325(10)
Mo(1)–C(2)
Mo(1)–P(1)
O(2)–C(2)
1.977(6)
2.4677(14)
1.152(7)
C(21)–C(22)
C(1)–Mo(1)–C(2)
C(2)–Mo(1)–C(21)
C(2)–Mo(1)–P(1)
O(1)–C(1)–Mo(1)
C(22)–C(21)–Mo(1)
99.8(2)
74.5(2)
80.57(16)
178.9(5)
135.9(5)
C(1)–Mo(1)–C(21)
C(1)–Mo(1)–P(1)
C(21)–Mo(1)–P(1)
O(2)–C(2)–Mo(1)
72.6(2)
76.70(16)
135.97(17)
177.7(5)
In
a
similar reaction, [CpMo(CO)3I] (503.3 mg,
1.353 mmol) reacted with PPh2Et (0.28 cm3, 1.353 mmol)
in the presence of Me3NO (112.3 mg, 1.497 mmol) to give
[CpMo(CO)2(PPh2Et)I] (577.8 mg, 76%). The compound
exists as a mixture of trans and cis isomers in a ratio of 7:3.
Data for [CpMo(CO)2(PPh2Me)I] (2a): IR: m(CO)
1963s, 1879s cmÀ1. trans-Isomer 1H NMR: d 7.50–7.35
(m, 10 H, Ph), 5.24 (s, 5 H, Cp), 2.50 (d, J 8.2 Hz, 3 H,
Me); 13C NMR: d 232.4 (d, JPC 26 Hz, CO), 136.4 (d,
JPC 46 Hz, Cipso), 134.2–127.8 (m, Ph), 93.4 (s, Cp), 21.8
(d, JPC 31 Hz, Me); 31P NMR 27.0 ppm. cis-Isomer 1H
NMR d 7.50–7.35 (m, 10H, Ph), 5.02 (d, J 1.9 Hz, 5H,
Cp), 2.24 (d, J 8.6 Hz, 3H, Me); 13C NMR d 250.8 (d,
JPC 30.1 Hz, CO), 238.2 (d, JPC 5.7 Hz, CO), 138.6 (d,
JPC 45.5 Hz, Cipso), 134.2–127.8 (m, Ph), 93.5 (s, Cp),
21.8 (d, JPC 31.4, Me); 31P NMR: 46.3 ppm. Mass spec-
trum: m/z 544 (M+), 516 (MÀCO)+. Anal. Calc. for
C20H18IMoO2P: C, 44.12; H, 3.31; I, 23.35. Found: C,
44.93; H, 3.08, I, 23.54%.
dent molecules of [(g-C5H4Me)W(r-CH@CH2)(CO)2
(PPh3)], though the e.s.d.’s in this structure were relatively
large [10].
4. Conclusions
The reaction of the substituted anions [CpMo(CO)2
(L)]À with the activated alkynes RC„CCO2Me provides
a general and regioselective route to g3-acryloyl complexes
[CpMo(g3-COCR@CHCO2Me)(CO)(L)] when
L is a
phosphine ligand, through a process involving vinyl to
carbonyl migration.
5. Experimental
General experimental techniques were as detailed in pre-
vious papers from this laboratory [15]. Infra-red spectra
were recorded in CH2Cl2 solution on a Perkin–Elmer
Data for [CpMo(CO)2(PPh2Et)I] (2b): IR: m(CO) 1963s,
1
1
1600 FT-IR machine using 0.5 mm NaCl cells. The H,
1879s cmÀ1. trans-Isomer H NMR d 7.62–7.35 (m, 10H,
13C and 31P NMR spectra were obtained in CDCl3 solution
on a Bruker AC250 Fourier transform machine with auto-
mated sample-changer or on Bruker AMX400 or DRX-500
spectrometers. Chemical shifts are given on the d scale rel-
Ph), 5.26 (s, 5H, Cp), 2.65 (dq, JPH 7.4, JHH 7.4 Hz, 2H,
CH2), 1.15 (dt, JPH 16.2 Hz, JHH 7.4 Hz, 3H, Me); 13C
NMR: d 233.2 (d, JPC 27 Hz, CO), 136.0 (d, JPC 41 Hz,
C
ipso), 134.4–127.8 (m, Ph), 93.2 (s, Cp), 26.8 (d, JPC
ative to SiMe4 = 0.0 ppm for H and 13C, and relative to
28 Hz, CH2), 10.4 (JPC 3 Hz, Me); 31P NMR 38.5 ppm.
1
1
85% H3PO4 for 31P. The 13C{1H} NMR spectra were rou-
tinely recorded using an attached proton test technique
(JMOD pulse sequence). Mass spectra were recorded on
a Kratos MS 80 instrument operating in either electron
impact mode or fast atom bombardment mode with
3-nitrobenzyl alcohol as matrix; the figures reported are
the highest intensity peak of each isotope envelope. Ele-
mental analyses were carried out by the Microanalytical
Service of the Department of Chemistry. The complexes
[Cp2Mo2(CO)6] [16] and [Cp2Mo2(CO)4(L)2] [8] were pre-
pared by the literature methods. The iodide compound
[CpMo(CO)3I] was prepared by treatment of a CH2Cl2
solution of [Cp2Mo2(CO)6] with a solution of one equiva-
lent of I2 dissolved in the same solvent [17]. Commercial
Me3NO Á 2H2O was rendered anhydrous by azeotropic dis-
tillation in toluene and stored under nitrogen.
cis-Isomer H NMR d 7.62–7.35 (m, 10H, Ph), 4.97 (d, J
1.8 Hz, 5H, Cp), 2.94 (dq, JPH 7.6 Hz, JHH 7.6 Hz, 2H,
CH2), 1.16 (m, 3H, Me); 13C NMR: d 251.4 (d, JPC
29 Hz, CO), 238.4 (d, JPC 5 Hz, CO), 134.6 (d,
JPC = 42 Hz, Cipso), 134.4–127.8 (m, Ph), 93.5 (s, Cp),
27.1 (d, JPC 33 Hz, CH2), 9.0 (d, JPC 3 Hz, Me); 31P
NMR 57.0 ppm. Mass spectrum m/z 558 (M+), 530, 502
(MÀnCO)+, n = 1, 2. Anal. Calc. for C21H20IMoO2P: C,
45.16; H, 3.58; I, 22.76. Found: C, 45.17; H, 3.45; I,
22.72%.
5.2. Synthesis of [CpMo{g3-COC(CO2Me)@CHCO2Me}
(CO) (PPh2Me)] (3a) and [CpMo(CO)2
{C(CO2Me)@CHCO2Me}(PPh2Me)] (4a)
A
solution of the sodium salt of the anion
[CpMo(CO)2(PPh2Me)]À was generated by stirring
[Cp2Mo2(CO)4(PPh2Me)2] (500 mg, 0.60 mmol) in THF
(40 cm3) with an excess of sodium amalgam (0.3 g,
13.0 mmol Na in 5 cm3 Hg). The solution was shaken
until the initially sparingly soluble purple powder had
5.1. Synthesis of [CpMo(CO)2(L)I] (2a, 2b)
The complex [CpMo(CO)3I] (339.4 mg, 0.912 mmol)
was dissolved in dichloromethane (15 cm3) and one equiv-

714
H. Adams et al. / Journal of Organometallic Chemistry 693 (2008) 709–716
completely dissolved to give an olive green solution which
was transferred to a second Schlenk tube by syringe.
Addition of two molar equivalents of DMAD (0.16 cm3,
1.30 mmol) caused an instantaneous colour change to
orange-brown which darkened further on stirring for
10 min. The solution was then treated with [Et2NH2][Br]
(190 mg, 1.23 mmol), which produced no visible change,
and then stirred for a further 25 min before removal of
the solvent in vacuo. The resulting brown oily residue was
then dissolved in the minimum volume of CH2Cl2 and
loaded onto a silica column. Elution with light petro-
leum-CH2Cl2 (1:1) yielded 60 mg of the starting material
[CpMo(CO)2(PPh2Me)]2 (12% recovery). An orange band
was removed using CH2Cl2–acetone (99:1) which gave a
yellow powdery solid (90 mg, 13%), identified as vinyl
complex 4a. Further elution using a 9:1 mixture of the same
solvents led to the isolation of acryloyl complex 3a as a
bright orange powder (310 mg, 46%).
Hg), was treated sequentially with methyl propiolate
(0.21 cm3, 2.36 mmol) and [Et2NH2][Br] (0.37 g,
2.40 mmol). Column chromatography as above gave the
vinyl complex 4b as a yellow band eluted in dichloromethane
(40 mg, 3.5%) followed by a dark orange band of acryloyl
complex 3b (330 mg, 29%). Yields for this reaction were con-
sistently lower than for the other three reported here.
1
Data for 3b: IR: m(CO) 1959m, 1733m cmÀ1. H NMR:
d 7.68–7.27 (m, 10H, Ph); 4.84 (d, JPH 0.8, 5H, Cp); 3.62 (s,
3H, CO2Me); 3.08 (dd, JPH 11.3, JHH 5.4, 1H, CHCO2Me);
1.87 (d, JPH 7.3, 3H, PMe); 1.79 (dd, JPH 2.1, JHH 5.4, 1H,
COCH). 13C NMR: d 258.2 (d, J 15, acyl CO); 239.1 (d, J
15, CO); 178.0 (s, CO2Me); 135.1 (d, J 38, Cipso); 134.4–
127.9 (m, Ph); 92.2 (s, Cp); 50.9 (s, CO2Me); 44.5 (d, J 4,
CHCO2Me); 29.7 (s, COCH); 17.7 (d, J 29, PMe). 31P
NMR: 37.4 ppm. Mass spectrum m/z 502 (M+). Anal.
Calc. for C24H23MoO4P: C, 57.38; H, 4.61. Found: C,
56.25; H, 4.74%.
1
In a similar reaction an anion solution prepared by the
Data for 4b: IR: m(CO) 1953m, 1870s, 1693m cmÀ1. H
reduction
of
[CpMo(CO)2(PPh2Me)I]
(189.6 mg,
NMR: d 9.89 (dd, JPH 1.8, JHH 16.8, 1H, MoCH); 7.47–
7.28 (m, 10H, Ph); 6.34 (dd, JPH 0.8, JHH 16.8, 1H,
CHCO2Me); 4.99 (d, JPH 1.3, 5H, Cp); 3.66 (s, 3H,
CO2Me); 2.14 (d, JPH 8.2, 3H, PMe). 13C NMR: d 232.9
(d, J 24, CO); 179.8 (d, J 11, MoCH); 163.5 (s, CO2Me);
137.1 (d, J 43, Cipso); 132.0 (s, CHCO2Me); 131.6–128.4
(m, Ph); 93.3 (s, Cp); 50.6 (s, CO2Me); 21.0 (d, J 34,
PMe). 31P NMR: 48.5 ppm. Mass spectrum m/z 502
(M+). Anal. Calc. for C24H23MoO4P.0.5CH2Cl2: C,
54.01; H, 4.44. Found: C, 53.76; H, 4.34%.
0.349 mmol) in 40 ml freshly distilled THF with sodium
amalgam (0.30 g, 13.0 mmol sodium in 5 cm3 mercury)
was treated with DMAD (0.04 cm3, 0.349 mmol) followed
by diethylammonium bromide (59.8 mg, 0.388 mmol).
The yields of products after chromatography were 4a,
35.2 mg (18.1%) and 3a, 117.4 mg (60.2%).
Data for 3a: IR: m(CO) 1949s, 1744sh, 1728m, 1691m
1
cmÀ1. H NMR: d 7.88–7.17 (m, 10H, Ph); 4.70 (s, 5H,
Cp); 3.66 (d, JPH 11.9, 1H, CH); 3.65 (s, 3H, CO2Me); 3.64
(s, 3H, CO2Me); 1.80 (d, JPH 7.3, 3H, PMe). 13C NMR: d
251.5 (d, J 6, acyl CO); 236.0 (d, J 14, CO); 177.2 (s, CO2Me);
173.0 (s, CO2Me); 138.9 (d, J 41, Cipso); 133.7–128.8 (m, Ph);
132.1 (d, J 36, Cipso); 93.0 (s, Cp); 51.8 (s, CO2Me); 50.9 (s,
CO2Me); 40.4 (s, COCCO2Me); 40.4 (s, CHCO2Me); 14.2
(d, J 15, PMe). 31P NMR: 29.1 ppm. Mass spectrum m/z
560 (M+). Anal. Calc. for C26H25MoO6P: C, 55.73; H,
4.50. Found: C, 55.54, H, 4.49%.
5.4. Synthesis of [CpMo{g3-COC(CO2Me)@CHCO2Me}
(CO)(PPh2Et)] (3c) and [CpMo(CO)2{r-C(CO2Me)
@CHCO2Me}(PPh2Et)] (4c)
An olive-green solution of Na[CpMo(CO)2(PPh2Et)]
was prepared by reduction of [Cp2Mo2(CO)4(PPh2Et)2]
(1.00 g, 1.16 mmol) in 40 cm3 freshly distilled THF with
an excess of sodium amalgam (0.30 g, 13.0 mmol of sodium
in 5 cm3 mercury). The solution was syringed into a second
Schlenk tube and treated with DMAD (0.40 cm3,
3.25 mmol), causing a colour change to red-brown. After
stirring for 10 min, diethylammonium bromide (0.51 g,
2.97 mmol) was added. After 20 min, the solvent was
removed. Column chromatography, eluting with acetone/
dichloromethane (1:99) produced a yellow band consist-
ing of the vinyl complex [CpMo(CO)2{r-C(CO2Me)
@CHCO2Me}(PPh2Et)] (4c) (40 mg, 3.2%). Further elution
with a 1:19 mixture of the same solvents gave an orange
band containing the acryloyl compound [CpMo{g3-COC
(CO2Me)@CHCO2Me}(CO)(PPh2Et)] (3c) (620 mg, 49.6%).
Data for 4a: IR: m(CO) 1959m, 1877s, 1706m cmÀ1. H
1
NMR: d 7.60–7.33 (m, 10H, Ph); 6.13 (s, 1H, CHCO2Me);
4.89 (d, JPH 1.5, 5H, Cp); 3.81 (s, 3H, CO2Me); 3.63 (s, 3H,
CO2Me); 2.15 (d, JPH 7.6, 3H, PMe). 13C NMR: d 236.3 (d,
J 26, CO); 178.5 (d, J 33, MoCCO2Me); 161.9 (s, CO2Me);
161.9 (s, CO2Me); 136.6 (d, J 45, Cipso); 132.4 (s,
CHCO2Me); 131.6–128.7 (m, Ph); 93.7 (s, Cp); 50.9 (s,
CO2Me); 50.8 (s, CO2Me); 20.9 (d, J 35, PMe). 31P
NMR: 48.7 ppm. Mass spectrum m/z 532 (M+ÀCO). Anal.
Calc. for C26H25MoO6P: C, 55.73; H, 4.50. Found: C,
54.77; H, 4.56%.
5.3. Synthesis of [CpMo(g3-COCH@CHCO2Me)
(CO)(PPh2Me)] (3b) and [CpMo(CO)2
(CH@CHCO2Me)(PPh2Me)] (4b)
1
Data for 3c: IR: m(CO) 1950s, 1729s, 1692m cmÀ1. H
NMR: d 7.60–7.32 (m, 10H, Ph); 4.72 (s, 5H, Cp); 3.64
(d, JPH 11.5, 1H, CH); 3.60 (s, 3H, CO2Me); 3.58 (s, 3H,
CO2Me); 2.20 (m, 1H, CH2); 2.04 (dq, JPH 2.7, JHH 7.3,
1H, CH2); 0.90 (dt, JPH 15.0, JHH 7.3, 3H, Me of Et).
13C NMR: d 252.2 (d, J 6, acyl CO); 236.0 (d, J 14, CO);
177.1 (s, CO2Me); 172.9 (s, CO2Me); 133.9 (d, J 40, Cipso);
In
a similar manner, a solution of the anion
[CpMo(CO)2(PPh2Me)]À generated by stirring [Cp2Mo2
(CO)4(PPh2Me)2] (1.00 g, 1.12 mmol) in THF (40 cm3) with
an excess of sodium amalgam (0.3 g, 13.0 mmol Na in 5 cm3

H. Adams et al. / Journal of Organometallic Chemistry 693 (2008) 709–716
715
Table 3
133.6–128.5 (m, Ph); 132.0 (d, J 35, Cipso); 93.1 (s, Cp); 51.7
Summary of crystallographic data for complexes 3b and 4b
(s, CO2Me); 50.8 (s, CO2Me); 40.6 (d, J 4, CHCO2Me);
33.2 (s, COCCO2Me); 21.7 (d, J 22, CH2); 8.6 (d, J 5,
Me of Et). 31P NMR: 40.8 ppm. Mass spectrum m/z 575
(M+H)+. Anal. Calc. for C27H27MoO6P: C, 56.45; H,
4.70. Found: C, 55.94; H, 4.60%.
3b
4b
Empirical formula
Formula weight
T (K)
C24H23MoO4P
502.33
150(2)
C24H23MoO4P
502.33
150(2)
Crystal system
Monoclinic
P21=n
7.598(2)
14.725(4)
19.458(6)
90
97.869(5)
90
2156.4(10)
4
1.547
0.710
1024
0.35 Â 0.21 Â 0.12
Triclinic
1
Data for 4c: IR: m(CO) 1960m, 1875s, 1705w cmÀ1. H
ꢀ
Space group
P1
NMR: d 7.60–7.35 (m, 10H, Ph); 6.16 (s, 1H, CH); 4.81
(d, JPH 1.2, 5H, Cp); 3.76 (s, 3H, CO2Me); 3.59 (s, 3H,
CO2Me); 2.57 (dq, JPH 7.8, JHH 7.8, 2H, CH2); 1.01 (dt,
JPH 18.0, JHH 7.8, 3H, Me of Et). 13C NMR: d 236.8 (d,
J 26, CO); 179.1 (d, J 53, MoCCO2Me); 161.8 (s, 2
CO2Me); 135.0 (d, J 41, Cipso); 132.0–128.3 (m, Ph); 93.9
(s, Cp); 50.9 (s, CO2Me); 50.8 (s, CO2Me); 26.4 (d, J 33,
CH2); 8.8 (d, J 2, Me of Et). 31P NMR: 59.3 ppm. Mass
˚
a (A)
9.2168(7)
10.4978(8)
11.8163(10)
75.969(3)
89.314(3)
81.540(4)
1096.79(15)
2
˚
b (A)
˚
c (A)
a (°)
b (°)
c (°)
3
˚
V (A )
Z
Dcalc (Mg mÀ3
)
1.521
0.698
512
l (mmÀ1
F(000)
)
spectrum
m/z
574
(M+).
Anal.
Calc.
for
C27H27MoO6P.0.25CH2Cl2: C, 54.95; H, 4.65. Found: C,
54.79; H, 4.90%.
Crystal size (mm3)
0.28 Â 0.12 Â 0.09
h Range for data collection (°) 1.74–25.00
Reflections collected
1.78–25.00
20239
17062
5.5. Synthesis of [CpMo(g3-COCH@CHCO2Me)
(CO)(PPh2Et)] (3d) and [CpMo(CO)2(r-CH@
CHCO2Me)(PPh2Et)] (4d)
Independent reflections
3789
3861
[R(int) = 0.1701]
3789/159/273
0.960
[R(int) = 0.0200]
3861/151/275
1.353
Data/restraints/parameters
Goodness-of-fit on F2
Final R1, wR2 [I > 2r(I)]
R1 = 0.0630,
wR2 = 0.1300
R1 = 0.1061,
wR2 = 0.1445
0.878 and À1.027
R1 = 0.0523,
wR2 = 0.1612
R1 = 0.0524,
wR2 = 0.1613
0.663 and À1.649
A solution of Na[CpMo(CO)2(PPh2Et)] was prepared
by reduction of [Cp2Mo2(CO)4(PPh2Et)2] (900.7 mg,
1.026 mmol) in 40 cm3 freshly distilled THF with an excess
of sodium amalgam (0.32 g, 13.9 mmol of sodium in 5 cm3
mercury). The solution was syringed away from the amal-
gam into another Schlenk tube and methyl propiolate
(0.18 cm3, 2.025 mmol), was added, causing the solution to
turn to a red/brown colour. After stirring 10 min 2.1 equiv.
of diethylammonium bromide (330.2 mg, 2.143 mmol) was
added to the solution and it was stirred for 20 min. No
noticeable colour change was observed. The solvent was
removed on a rotary evaporator and the products of the
reaction were separated by column chromatography. A
yellow band was eluted in pure dichloromethane and shown
to be the vinyl compound, [CpMo(r-CH@CHCO2Me)
(CO)2(PPh2Et)] (4d), followed by a brown band in
acetone/dichloromethane (3:17), shown to be the acryloyl
All data
Largest diffraction peak and
À3
˚
hole (e A
)
7.42 (m, 10H, Ph); 6.37 (d, JHH 16.5, 1H, CH); 4.94 (d,
JPH 1.2, 5H, Cp); 3.68 (s, 3H, CO2Me); 2.62 (dq, JPH 7.8,
JHH 7.8, 2H, CH2); 1.09 (dt, JPH 18.0, JHH 8.0, 3H, Me
of Et). 13C NMR: d 233.5 (d, J 24, CO); 180.9 (d, J 11,
MoCH); 163.5 (s, CO2Me); 135.5 (d, J 41, Cipso); 132.3–
128.3 (m, Ph); 93.4 (s, Cp); 50.6 (s, CO2Me); 26.4 (d, J
32, CH2); 8.8 (s, Me of Et). 31P NMR: 59.4 ppm. Mass
spectrum m/z 516 (M+). Anal. Calc. for C25H25MoO4P:
C, 58.14; H, 4.84. Found: C, 57.78; H, 4.71%.
6. Crystal structure determinations
product,
[CpMo(g3-COCH@CHCO2Me)(CO)(PPh2Et)]
(3d). Final yields of the two isomeric products were
The crystal data for the two structures are collected in
Table 3. General procedures were as described in previous
publications. A Bruker Smart CCD area detector with
Oxford Cryosystems low temperature system was used
for data collection at 150(2) K. Complex scattering factors
were taken from the program package SHELXTL [19] as
implemented on a Viglen Pentium computer. Hydrogen
atoms were placed geometrically and refined in riding mode
(including torsional freedom for methyl groups) with Uiso
constrained to be 1.2 times Ueq of the carrier atom (1.5
for methyl groups).
24.1 mg (2.6%) and 308.8 mg (33.2%), respectively.
1
Data for 3d: IR: m(CO) 1957s, 1721m, 1677m cmÀ1. H
NMR: d 7.78–7.07 (m, 10H, Ph); 4.88 (s, 5H, Cp); 3.61 (s,
3H, Me); 3.02 (dd, JPH 10.8, JHH 5.3, 1H, COCH); 2.45 (m,
1H, CH2); 2.25 (m, 1H, CH2); 1.54 (dd, JPH 2.0, JHH 5.3,
1H, CHCO2Me); 0.96 (dt, JPH 17.4, JHH 7.8, 3H, Me of
Et). 13C NMR: d 258.3 (d, J 5, acyl CO); 239.5 (d, J 15,
CO); 177.7 (s, CO2Me); 133.8–128.2 (m, Ph); 91.8 (s, Cp);
50.8 (s, CO2Me); 44.4 (d, J 3, CHCO2Me); 25.1 (d, J 28,
CH2); 23.6 (s, COCH); 8.5 (s, Me of Et). 31P NMR:
49.3 ppm. Mass spectrum m/z 516 (M+). Anal. Calc. for
C25H25MoO4P: C, 58.14; H, 4.84. Found: C, 58.12; H,
4.90%.
Acknowledgements
Data for 4d: IR: m(CO) 1953w, 1870m, 1682m cmÀ1. 1H
NMR: d 9.90 (dd, JPH 1.1, JHH 16.5, 1H, MoCH); 7.78–
This work was supported by the University of Sheffield.
´
R.H. was a visiting Erasmus student from the Universite de

716
H. Adams et al. / Journal of Organometallic Chemistry 693 (2008) 709–716
(c) K.W. Barnett, P.M. Treichel, Inorg. Chem.
294;
(d) R.J. Haines, C.R. Nolte, J. Organomet. Chem. 24 (1970)
725;
(e) R.J. Klingler, W. Butler, M.D. Curtis, J. Am. Chem. Soc. 97
(1975) 3535.
6
(1967)
Rennes, France (1992–93), and A.-G.H. was an Erasmus
student from the University of Hamburg, Germany (2007).
Appendix A. Supplementary material
[8] H. Adams, N.A. Bailey, P. Blenkiron, M.J. Morris, J. Chem. Soc.,
Dalton Trans. (1997) 3589.
[9] (a) G.B. McVicker, Inorg. Chem. 14 (1975) 2087;
(b) G.B. McVicker, U.S. Patent 4124647 (1978).
[10] H. Adams, N.A. Bailey, J.T. Gauntlett, I.M. Harkin, M.J. Winter, S.
Woodward, J. Chem. Soc., Dalton Trans. (1991) 1117.
CCDC 665423 and 665422 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_re-
quest/cif. Supplementary data associated with this article
can be found, in the online version, at doi:10.1016/
j.jorganchem.2007.11.059.
´
´ ´
´
[11] (a) F.Y. Petillon, J.-L. LeQuere, F. Le Floch-Perennou, J.E.
Guerchais, M.-B. Gomes de Lima, L.J. Manojlovic-Muir, D.W.A.
Sharp, J. Organomet. Chem. 255 (1984) 231;
´
´
(b) F.Y. Petillon, F. Le Floch-Perennou, J.E. Guerchais, D.W.A.
Sharp, L. Manojlovic-Muir, K.W. Muir, J. Organomet. Chem. 202
(1980) 23.
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