Studies directed toward the synthesis of chiral tungsten and molybdenum carbonyl complexes

Article abstract of DOI:10.1016/j.jorganchem.2008.02.008

A major challenge that must be met for an asymmetric intermolecular Pauson-Khand reaction is to be able to limit the possible positions on the metal complex for the organic partners. Toward this end, the synthesis of monometallic systems derived from M(CO)₆ and two bidentate ligands, in which the number of possible coordination sites is reduced to two, has been investigated.

Full text of DOI:10.1016/j.jorganchem.2008.02.008

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 693 (2008) 1841–1849
www.elsevier.com/locate/jorganchem
Studies directed toward the synthesis of chiral tungsten
and molybdenum carbonyl complexes
Pathik Maji, Wei Wang, Andrew E. Greene, Yves Gimbert *
De´partement de Chimie Mole´culaire (SERCO) UMR-5250, ICMG FR-2607, CNRS-Universite´ Joseph Fourier, BP-53, 38041 Grenoble Cedex 9, France
Received 25 January 2008; received in revised form 7 February 2008; accepted 7 February 2008
Available online 15 February 2008
Abstract
A major challenge that must be met for an asymmetric intermolecular Pauson–Khand reaction is to be able to limit the possible posi-
tions on the metal complex for the organic partners. Toward this end, the synthesis of monometallic systems derived from M(CO)6 and
two bidentate ligands, in which the number of possible coordination sites is reduced to two, has been investigated.
Ó 2008 Elsevier B.V. All rights reserved.
Keywords: Pauson–Khand; Bidentate; Ligand; Electrodeficient; Chiral complexes; Molybdenum
1. Introduction
(Fe [9], Ru [10]), and IX (Rh [11], Ir [12]). Various enantio-
selective versions of the Pauson–Khand reaction have been
reported, most recently catalytic and with chiral ligands;
however, to date, the only generally useful procedures are
for intramolecular reactions. Intermolecular protocols that
are enantioselective have been disclosed, but serve in part
to underscore the difficulty in developing procedures that
are truly efficient and general [13]. Moyano et al., for exam-
ple, have nicely used non-symmetric bidentate ligands with
Co2(CO)8 for intermolecular reactions, but to date have
not been able to avoid the formation of diastereomers dur-
ing their introduction, necessitating in most cases a separa-
tion [14]. The situation is rather comparable with
monometallic and bimetallic complexes: several afford sat-
isfactory results in the intramolecular version, but are not
generally effective in the intermolecular.
A major challenge that needs to be met for an asymmet-
ric intermolecular Pauson–Khand reaction is to be able to
limit the possible positions on the complex for the organic
partners. (In the case of the intramolecular reaction, the
number of ultimate coordination sites is geometrically
restricted because of the tethering of the double and triple
bonds.) Toward this end, we decided to investigate the syn-
thesis of monometallic systems derived from M(CO)6 and
two bidentate ligands [15], in which the number of possible
The preparation of well designed chiral metal carbonyl
complexes with a limited number of coordination sites
for use in asymmetric synthesis is a timely objective. A sali-
ent example of a transformation in which such complexes
already find application is the Pauson–Khand reaction.
This reaction, which unites an alkene, an alkyne, and car-
bon monoxide to form a cyclopentenone derivative, contin-
ues even after several decades to be the subject of
considerable research [1], and provides still fertile ground
for the development new chiral metal carbonyl complexes.
It was our interest in the intermolecular version of this
reaction that led us to study the preparation of novel chiral
metal carbonyl complexes with a limited number of coordi-
nation sites, a study that produced unexpected, but inter-
esting results, which are now reported.
The Pauson–Khand reaction is normally mediated by
bimetallic complexes (Co–Co [1], Mo–Mo [2], Co–Mo [3],
Co–W [4], Co–Rh [5], etc.), but it can also be performed
with monometallic carbonyl complexes, such as those of
metals from columns IV (Ti [6]), VI (Mo [7], W[8]), VIII
*
Corresponding author. Tel.: +33 4 76 51 43 44; fax: +33 4 76 51 44 94.
E-mail address: Yves.Gimbert@ujf-grenoble.fr (Y. Gimbert).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.02.008

1842
P. Maji et al. / Journal of Organometallic Chemistry 693 (2008) 1841–1849
2. Results and discussion
In an early example of the use of tungsten in the Pau-
son–Khand reaction, Hoye and Suriano [8] reported
W(CO)5 ꢀ THF, obtained photochemically from W(CO)6
in THF, to be an effective reaction mediator. We found
that with chiral complexes derived from W(CO)5 ꢀ THF
and monophosphine ligands, the yields for an intramolecu-
lar reaction were good (58–63%), but the enantiomeric
excesses, not surprisingly, turned out to be essentially nil
(<2%). The bicyclization with 3 different tungsten com-
plexes is shown in Scheme 1.
L1
P1
L1
P1
CO
CO
M
P2
L2
Mo
L2
Thus, as previously surmised, a reduction in the number
of possible coordination sites was required, which led us to
study the introduction of 2 different bidentate ligands;
however, the introduced bidentate ligands could not be
coplanar (mer isomer), for this would make the subsequent
Pauson–Khand reaction geometrically impossible (axial
disposition of the remaining coordination sites). Few
examples, though, of selective ligand introduction in a
bidendate-coordinated carbonyl complex have been
described in the literature [16]. A possible means to control
the regiochemistry of the insertion of the second bidentate
ligand might be to introduce initially an electron-rich
bidentate ligand, which would result in a relative labiliza-
tion of the cis positions (‘‘cis labilization effect” [17]), but
this strategy has possible pitfalls [18].
In an initial test of this approach, it was planned that
bis(diphenylphosphino)ethane (dppe) would be introduced
first, followed by an electron-poor binol derivative having
on each oxygen a dipyrrolylphosphino group (Scheme 2).
The dppe complex 5 could be conveniently prepared in
77% yield from the stable intermediate 4 by using the pro-
cedure described by Darensbourg and Kump [19] but,
unfortunately, the introduction of the binol derivative
proved to be impossible. This failure is probably the conse-
quence of both the electron donating properties of dppe,
which makes all of the CO ligands less labile [20], and
P2
M = Mo
L1-L1 = dppe
L2-L2* = bis(dipyrrolylphosphino)-binol
Fig. 1. Molecular modeling (PM3) of a possible M(CO)2(L1–L1)(L2–L2)*
complex.
coordination sites would be reduced to two. Limiting the
number of sites in this way and having chirality on one
or both of the ligands appeared to offer an effective strategy
for achieving enantioselective Pauson–Khand reactions.
An example of a possible complex of this type is shown
in Fig. 1. A successful approach along these lines would
eliminate the loss of alkyne substrate occurring on separa-
tion of diastereomers, which seems to be nearly inevitable
(for good enantioselectivity) when using bimetallic com-
plexes with non-symmetric, and sometimes symmetric,
ligands. With the envisaged strategy, in contrast, the diaste-
reomeric complexes would first be separated, if necessary,
and then allowed to react with the organic partners leading,
hopefully, to a selective reaction.
TsN
CO
W
CO
W
OC
OC
CO
L-x
OC
OC
2
CO
L-x
TsN
O
THF
CO
CO
H
1
3
1L-x
Me
Ts
N
Me
O
F3C
F3C
O
O
O
O
H
H
P
NEt2
P
P
N
Me
N
Me
Ph
Ts
L-a
L-c
L-b
Scheme 1.

P. Maji et al. / Journal of Organometallic Chemistry 693 (2008) 1841–1849
1843
CO
W
CO
W
CO
W
CO
W
Ph2
P
Ph2
P
OC
OC
CO
CO
OC
OC
piperidine
dppe
OC
OC
OC
P
NH
NH
X
diglyme
150 °C
24h
toluene
110 °C, 2h
P
P
Ph2
Ph2
CO
CO
CO
P
*
5
6
4
N
P
P
P
N
O
O
=
N
P
N
Bis(dipyrrolylphosphino)-binol
Scheme 2.
the electrodeficient character of the phosphorus atoms in
the binol derivative.
displace two of the DMF ligands, whereupon the next group
displaced could be expected to be the remaining DMF to
yield ultimately the diastereomeric fac-[Mo(CO)2(L1–L1)-
(L2–L2)*] complexes (Scheme 3).
However, while the fac isomer M(CO)3L3 in brackets is
electronically favored because of Mo to CO back-dona-
tion, the mer-isomer should be preferred sterically. Thus,
conceivably, a fac to mer isomerization involving migration
of the first L2 (or an L1) might take place through L and
CO interchange prior to the final Mo–L2 bond formation.
This isomerization, though, could also occur in the final
fac-isomers Mo(CO)2(L1–L1)(L2–L2)* (Scheme 4).
Isomerizations of this kind are well precedented. Rou-
sche and Dobson [22] observed a migration of a monoden-
tate ligand, through dissociation–association, on heating
fac-[Mo(CO)3(g2-dppe){P(OPri)3}] at 120 °C to give mer-
[Mo(CO)3(g2-dppe){P(OPri)3}]. The same research group
[23] has also described the isomerization of fac-
[Mo(CO)3(g2-dppe)(PPh3)] at 125 °C (but, in contrast,
fac-[Mo(CO)3(g2-dppe)(C6H11NH2)] was found to be sta-
ble even at elevated temperatures). Darensbourg et al.
[24] observed that fac-[W(CO)3(13CO)(g2-dppe)] undergoes
thermal transformation to a mixture of facial and meridional
In order to overcome this problem of reactivity, it was
decided that the generally more reactive molybdenum com-
plexes should be examined in place of the tungsten com-
plexes. In 2005, Carretero et al. reported a Pauson–
Khand reaction using Mo(CO)3(DMF)3 (7), which was
found to be reactive under mild conditions [7c]. Relevant
to the present work, the X-ray structure of this complex
showed that it was the fac isomer (Fig. 2) [21]. Thus, start-
ing from Mo(CO)3(DMF)3, it appeared that it could be
possible to control the introduction of the bidentate
ligands: the first bidentate ligand would undoubtedly
CO
OC
CO
DMF
7
Mo
DMF
DMF
fac-[Mo(CO)3(DMF)3]
Fig. 2. Fac disposition of DMF ligands in complex 7.
CO
OC
L1
L2
L2
Mo
*
CO
Mo
L1
CO
Mo
L1
CO
Mo
L1
+
OC
L1
CO
L2
OC
L1
CO
OC
CO
L1-L1
L2-L2*
L2
DMF
DMF
DMF
L2
*
DMF
*
OC
L1
CO
Mo
L1
fac-Mo(CO)3(DMF)3
L2
fac-[Mo(CO)2(L1-L1)(L2-L2)*]
diastereomers
Scheme 3.

1844
P. Maji et al. / Journal of Organometallic Chemistry 693 (2008) 1841–1849
L2
*
*
CO
Mo
L1
CO
Mo
L1
L2
Mo
L1
L2
CO
OC
L1
OC
L1
L2
CO
CO
L2
OC
L1
L2
fac-[Mo(CO)2(L1-L1)(L2-L2)*]
isomerization
isomerization
*
fac-isomer
mer-isomer
mer-[Mo(CO)2(L1-L1)(L2-L2)*]
Scheme 4.
isomers, as later seen with [W(CO)3(g2-diphos)(g1-
diphos0)] (diphos = diphosphine ligand) by Hsu and Yeh
[25]. More recently, Fukumoto and Nakazawa[26] have
demonstrated the ability of silanes to catalyze fac to mer
isomerization in fac-[Mo(CO)3{P(OR)3}3]. Interestingly,
Schenk and Hilpert[27] described a switching of ligands,
but without isomerization, on heating the four-membered
chelate fac-[Mo(CO)3(g2-dppm)(NCMe)] and dppe to
afford the more stable five-membered chelate fac-[Mo-
(CO)3(g2-dppe)(g1-dppm)]; in contrast, Krishnamurthy et al.
reported that treatment of fac-[Mo(CO)3(NCMe){g2-Ph2-
PN(Pri)PPh(dmpz)}] (dmpz = 3,5-dimethylpyrazol-1-yl) with
dppe produced both fac- and mer-[Mo(CO)3{g2-Ph2PN-
(Pri)PPh(dmpz)}(g1-dppe)], in which the four-membered
diphosphazane ring remains intact and the dppe is coordi-
nated in an g1-fashion [28]. What distills from the ensemble
of this work is that predictions of stereochemistry in these
systems can be quite hazardous. In light of this, we pru-
dently began our work on this approach by introducing
first dppe in fac-[Mo(CO)3(DMF)3] (7) and then different
monophosphorus ligands (triphenyl phosphite, triethyl
phosphite, and tripyrrolylphosphine) in the resulting
complex. These experiments, together with an X-ray struc-
ture of mer-[Mo(CO)3(dppe)(P(pyrrolyl)3)] (mer-9c), are
shown in Scheme 5.
Both the facial and meridional isomers were generally
formed, but in different ratios at a given temperature.
For example, at 90 °C triphenyl phosphite produced an
equimolar mixture of the two isomers, while triethyl phos-
phite afforded mainly the fac and tripyrrolylphosphine
mostly the mer. Not surprisingly, when the reactions were
performed at 135 °C, the mer isomers were formed prefer-
entially with all three ligands. With tripyrrolylphosphine,
the mer isomer was produced exclusively. The 31P NMR
displayed for P(pyrrolyl)3 one signal at 135.4 ppm (dd,
2
2JPꢁPcis = 27 Hz, JPꢁPtrans = 119 Hz) for this isomer (one
signal at 128.2 ppm (t, 2JPꢁPcis = 32 Hz) for the fac deriva-
tive) [29]. The mer isomers would seem to suffer fewer
severe steric interactions, which could explain most of these
results; however, electronic factors may also be involved.
The investigation was continued with the bidentate
ligand bis(dipyrrolylphosphino)-binol, the hope being that
after the formation of the first P–Mo bond, the subsequent
P–Mo bond formation leading to chelation would be faster
CO
CO
Mo
CO
CO
Mo
OC
OC
CO
OC
OC
L
CO
L
CO
L
dppe
Mo
Mo
+
90 or 135 °C
Ph2P
toluene
20 °C, 3 h
Ph2P
DMF
Ph2P
DMF
DMF
CO
12 h
PPh2
PPh2
DMF
PPh2
7
8
fac-[Mo(CO)3(η2-dppe)(DMF)]
fac-9 a-c
mer-9 a-c
fac- [Mo(CO)3(DMF)3]
L
temperature (°C) yield(%) mer-9/fac-9
50/50
90/10
5/95
90
135
90
77
78
85
85
P(OPh)3
a
b
c
P(OEt)3
135
70/30
P(pyrrolyl)3
90
70
71
80/20
100/0
135
ortep of mer-9c
Scheme 5.

P. Maji et al. / Journal of Organometallic Chemistry 693 (2008) 1841–1849
1845
than any fac to mer P–CO rearrangement and that the
product would be stable to isomerization. The reaction of
fac-8 with the bis(dipyrrolylphosphino)-binol ligand for
12 h at 135 °C (at 90 °C, the reaction was extremely slow)
led, however, to a totally unexpected complex, mer-10
(Scheme 6).
at 135 °C for 12 h (31P NMR: unique singlet at
108.3 ppm), as is the [Mo(CO)4(bis(dipyrrolylphosphino)-
binol)] complex [30] (31P NMR: unique singlet at
147.6 ppm). Thus, the unexpected events must begin with
the introduction of the second bidentate ligand. In Scheme
7, we show a plausible pathway to explain the formation of
mer-10 from fac-8.
Again unexpectedly, the complex mer-10 was also
obtained
starting
from
fac-[Mo(CO)3{g2-bis(dip-
Isomerizations analogous to that of fac-11 to mer-11
have previously been observed (see above), but the
subsequent steps are, to the best of our knowledge,
yrrolylphosphino)-binol}(DMF)] and dppe. The bis(dip-
yrrolylphosphino)-binol ligand itself is stable in toluene
CO
Ph2
CO
Ph2
OC
P
OC
OC
bis(dipyrrolylphosphino)-binol
Mo
CO
P
O
O
P
N
Mo
P
Ph2
toluene, 135 °C, 12 h
P
Ph2
59%
DMF
fac-8
mer-10
ortep of mer-10
Scheme 6.
CO
Ph2
CO
Mo
Ph2
P
OC
OC
O
P
OC
P
pyrrolyl
pyrrolyl
(pyrrolyl)2P
Mo
P
O
P
O
Ph2
Ph2
CO
P(pyrrolyl)2
O
fac-8
P
pyrrolyl
pyrrolyl
fac- 11
mer- 11
CO
CO
Ph2
P
Ph2
P
OC
OC
pyrrolyl
O
Mo
CO
Mo
Pyr
O
P
P
P
P
Ph2
Ph2
O
CO
O
P
pyrrolyl
mer-10
pyrrolyl
P(pyrrolyl)3
+
+
pyrrolyl
Scheme 7.

1846
P. Maji et al. / Journal of Organometallic Chemistry 693 (2008) 1841–1849
unprecedented. It is possible, though, that loss of P(pyrrol-
yl)3 occurs prior to fac to mer isomerization. We have never
observed the formation of any 9c in the reaction; however,
the free ligand has been identified in the crude mixture by
31P NMR (78.4 ppm). Finally, the leaving group ability
of the phosphorus substituant is important [31], which is
consistent with the proposed pathway.
cooled to ꢁ78 °C, PCl3 (0.090 mL, 1.03 mmol) was added
slowly, and the temperature was allowed to rise to 20 °C
over 2 h. The mixture was then cooled again to ꢁ78 °C
and (S)-a-methylbenzylamine (0.210 mL, 1.63 mmol) was
added dropwise. After 2 h, the mixture was allowed to
warm to 20 °C and was then stirred overnight. The sol-
vent was removed under reduced pressure and the residue
was taken up in toluene/EtOAc (95/5), which was filtered
though a thin pad of silica gel to remove the amine salt.
The filtrate was then concentrated under reduced pressure
and the residue was purified by flash chromatography on
silica gel, eluting first with 5% ethyl acetate in pentane
and then with 5% ethyl acetate in toluene, to afford (1S)-
N-(meso-4,5-bis(trifluoromethyl)-1,3-ditosyl-1,3,2-diaza-
phospholidin-2-yl)-1-phenylethanamine (L-a, 0.140 g with
0.056 g of recovered starting material, 55% yield) as a
colorless oil: 31P NMR (121.49 MHz, CDCl3) d 102.86;
1H NMR (300 MHz, CDCl3) d 1.64 (d, J = 6.8 Hz, 3H),
2.40 (s, 3H), 2.46 (s, 3H), 3.88 (t, J = 10 Hz, 1H),
4.06–4.26 (m, 2H), 4.61–4.74 (m, 1H), 7.13 (d, J =
8.0 Hz, 2H), 7.30–7.38 (m, 7H), 7.51 (d, J = 8.3 Hz,
2H), 7.75 (d, J = 8.2 Hz, 2H); 19F NMR (282.4 MHz,
CDCl3) d ꢁ66.23 to ꢁ66.34 (m, 3F), ꢁ66.48 to ꢁ66.58
(m, 3F).
3. Conclusion
It has been shown in this initial study that introduction
of a second bidentate ligand in a molybdenum tetracar-
bonyl complex is fraught with complications, inter alia fac
to mer isomerism and unprecedented ligand fragmentation.
However, the preparation of enantiopure molybdenum
carbonyl complexes, with only 2 available sites for coordi-
nation, for use in asymmetric synthesis warrants further
study.
4. Experimental
Thin-layer chromatography was performed on (0.2 mm)
silica sheets, which were visualized under ultraviolet light
and by heating the plate after treatment with phosphomo-
lybdic acid in ethanol, a p-anisaldehyde staining solution
(80 mL of 95% ethanol, 2.9 mL of sulfuric acid, 0.86 mL
of acetic acid, 2.1 mL of p-anisaldehyde), nihydrin in etha-
nol, ceric ammonium molybdate in ethanol, or basic, aque-
ous KMnO4. Silica gel (0.040–0.063 mm) was employed for
flash column chromatography. Melting points were
obtained on a Buchi melting point apparatus and are
uncorrected. A Nicolet Impact 400 infrared spectrometer
was used to record IR spectra. NMR spectra were recorded
on a Bruker AV 300 apparatus and are reported in ppm.
Mass spectra were recorded using an Esquire 3000 Bruker
spectrometer (ESI mode). Microanalyses were performed
by the analytical service of the DCM. Toluene and tetrahy-
drofuran were distilled from sodium-benzophenone, trieth-
ylamine and pyrrole from CaH2, and dimethylformamide
from BaO prior to use. All solvents were degassed before
reactions, which were carried out under argon. W(CO)6
and Mo(CO)6 were purchased from Acros Organics. The
complexes W(CO)5 ꢀ THF [8], W(CO)4(piperidine)2 [19],
W(CO)4dppe [19], Mo(CO)4(piperidine)2 [19], and
Mo(CO)3(DMF)3 [7c] and chlorodipyrrolylphosphine
[32], menthyl phosphorodichloridite, and the binol
ligands[33] were synthesized through literature procedures.
A solution of W(CO)5 ꢀ THF in THF [8] (27 mL, ca.
1.8 mmol) was added to amine derivative L-a (0.480 g,
0.73 mmol) in 4 mL of THF under argon, and the resultant
mixture was stirred at 20 °C overnight. The solvent was
then removed by rotary evaporation and the excess tung-
sten reagent was eliminated at 45 °C under high vacuum.
The residue was dissolved in dichloromethane, which was
filtered. The filtrate was concentrated to afford 0.620 g
(86%) of complex 1L-a:
31P NMR (121.49 MHz, CDCl3) d
102.75 (1J183W–31P = 368 Hz); 1H NMR (300 MHz, ace-
tone-d6) d 1.67 (d, J = 6.6 Hz, 3H), 2.46 (s, 3H), 2.50 (s,
3H), 4.47–4.52 (m, 2H), 4.62–4.73 (m, 2H), 7.27–7.81 (m,
13H); 19F NMR (282.4 MHz, CDCl3) d ꢁ112.38 to
ꢁ112.31 (m, 3F), ꢁ111.95 to ꢁ111.88 (m, 3F); IR 2081,
1948 cmꢁ1
.
4.2. Preparation of W(CO)5 complex 1L-b
A solution of W(CO)5 ꢀ THF in THF [8] (75 mL, ca.
2.8 mmol) was added to a solution of the (R)-binol phos-
phoramidite ligand (L-b) (0.324 g, 0.84 mmol) in 5 mL of
THF and the resultant mixture was stirred at 60 °C for 2.
The solvent was then removed under reduced pressure
and the excess tungsten reagent was eliminated at 75 °C
under high vacuum. The residue was subjected to flash
chromatography on silica gel with 10% ethyl acetate in pen-
tane to afford the tungsten pentacarbonyl complex 1L-b
(0.483 g, 81%): mp 148–151 °C (dec); 31P NMR
(121.49 MHz, CDCl3) d 159.2 (1J183W–31P = 379 Hz); 1H
NMR (300 MHz) d 1.02 (m, 6H), 2.83 (m, 2H), 3.13 (m,
2H), 7.0–7.4 (m, 8H), 7.59 (d, J = 6.0 Hz, 1H), 7.83 (m,
2H), 7.94 (d, J = 8.0 Hz, 1H); IR (CH2Cl2) 2076, 1984,
1938 cmꢁ1; MS (ESI+) m/z 712 [M+H]+ (100%). Anal.
4.1. Preparation of W(CO)5 complex 1L-a
A solution of meso-1,1,1,4,4,4-hexafluoro-N2,N3-dito-
sylbutane-2,3-diamine [34] (0.252 g, 0.50 mmol) in
2.0 mL of THF was cooled to ꢁ78 °C under argon and
0.68 mL of a solution of n-BuLi (1.6 M in hexane,
1.1 mmol) was added dropwise. The mixture was stirred
at ꢁ78 °C for 30 min and then allowed to warm to
20 °C. After 2 h, the resulting dark brown mixture was

P. Maji et al. / Journal of Organometallic Chemistry 693 (2008) 1841–1849
1847
Calc. for C29H22NO7PW: C, 48.97; H, 3.12; N, 1.97.
Found: C, 49.29; H, 3.11; N, 2.01%.
1858 cmꢁ1. Anal. Calc. for C35H39O6P3Mo: C, 56.47; H,
5.28. Found: C, 56.61; H, 5.26%.
Complexes 9a (at 90 °C, 77% combined yield; at 135 °C,
78% combined yield) and 9c (at 90 °C, 70% combined yield;
at 135 °C, 71% combined yield) were prepared in the same
manner. fac-9a: 31P NMR (121.49 MHz, CDCl3) d 145.0 (t,
2JPꢁPcis = 35 Hz, 1P), 52.3 (br s, 2P);mer-9a. 31P NMR
4.3. Preparation of W(CO)5 complex 1L-c
A solution of W(CO)5 ꢀ THF in THF [8] (75 mL, ca.
2.8 mmol) was added to a solution of the (R)-binol
(1R,2S,5R)-menthol phosphite ligand (L-c) (0.432 g,
0.92 mmol) in 5 mL of THF and the resultant mixture
was stirred at 60 °C for 2 h. The solvent was then removed
under reduced pressure and the excess tungsten reagent was
eliminated at 75 °C under high vacuum. The residue was
subjected to flash chromatography on silica gel with 10%
ethyl acetate in pentane to afford the tungsten pentacar-
bonyl complex 1L-c (0.525 g, 72%): mp 172–174 °C (dec);
2
(121.49 MHz, CDCl3) d 164.9 (dd, JPꢁPcis = 31 Hz,
2
2JPꢁPtrans 141 Hz, 1P), 62.4 (d, JPꢁPtrans = 141 Hz, 1P),
53.4 (s, 1P); MS (ESI+) m/z 889 [M+H]+ (20%), 415
(100%). fac-9c: 31P NMR (121.49 MHz, CDCl3) d 128.2
2
(t, JPꢁPcis = 32 Hz, 1P), 52.4 (br s, 2P); 1H NMR
(300 MHz) d 1.39 (s, 2H), 2.48 (s, 2H), 6.12 (s, 6H), 6.31
(s, 6H), 7.19-7.39 (m, 16H), 7.72 (m, 4H); IR (CH2Cl2)
2014, 1949, 1896, 1868 cmꢁ1. mer-9c: mp 220–224 °C
(dec); 31P NMR (121.49 MHz, CDCl3) d 135.4 (dd,
31P NMR (121.49 MHz, CDCl3) d 149.3 (1J183W–31P
=
1
2
407 Hz); H NMR (300 MHz) d 0.40 (d, J = 6.9 Hz, 3H),
0.70 (d, J = 7.0 Hz, 3H), 0.80 (m, 4H), 1.20 (m, 4H), 1.50
(m, 2H), 1.85 (m, 1H), 2.15 (m, 1H), 4.20 (br s, 1H), 7.18
(m, 4H), 7.36 (m, 2H), 7.54 (d, J = 8.0 Hz, 1H), 7.87 (m,
4H), 7.95 (d, J = 6.0 Hz, 1H); IR(CH2Cl2) 2078, 1991,
1935 cmꢁ1; MS (ESI+) m/z 817 [M+Na]+ (100%). Anal.
Calc. for C35H30O8PW: C, 52.98; H, 3.81. Found: C,
53.15; H, 3.93%.
2JPꢁPcis = 27 Hz, JPꢁPtrans = 119 Hz, 1P), 60.9 (d, P,
2JPꢁPtrans = 119 Hz, 1P), 52.9 (s, 1P); 1H NMR
(300 MHz) d 1.38 (s, 2H), 2.44 (s, 2H), 6.06 (s, 6H), 6.29
(s, 6H), 7.17–7.37 (m, 16H), 7.68 (m, 4H); IR (CH2Cl2)
2074, 2022, 1988, 1886, 1833 cmꢁ1; MS (ESI+) m/z 832
[M+Na]+ (5%), 453 (100%). Anal. Calc. for
C41H36N3O3P3Mo: C, 60.98; H, 4.49; N, 5.20. Found: C,
61.23; H, 4.50; N, 5.31%. For crystallographic data, see
Table 1.
4.4. Preparation of fac-mer-9a–c. Representative procedure
(9b)
4.5. Preparation of Mo(CO)4(bis(dipyrrolylphosphino)-
binol)
A stirred solution of freshly prepared Mo(CO)3(DMF)3
(0.600 g, 1.50 mmol) and bis(diphenylphosphino)ethane
(0.598 g, 1.50 mmol) in 25 mL of dry toluene–DMF (4:1)
was stirred at 20 °C for 3 h. Triethyl phosphite
(0.257 mL, 1.50 mmol) in 5 mL of toluene was then added
and the reaction mixture was heated at 90 °C for 12 h.
After being allowed to cool to 20 °C, the reaction mixture
was filtered through a pad of celite and the filtrate was con-
centrated under reduced pressure to give the crude product
(95:5, fac:mer, by 31P NMR). Purification of this material
was accomplished by flash chromatography on silica gel
with 20% ethyl acetate in pentane to give the more polar
complex, fac-9b (0.903 g, 81%): mp 209–212 °C (dec); 31P
A stirred solution of (R)-bis(dipyrrolylphosphino)-binol
(0.647 g, 1.06 mmol) and molybdenum tetracarbonyl dipi-
peridine complex (0.420 g, 1.11 mmol) in 40 mL of toluene
was heated at 100 °C for 3 h. After being allowed to cool to
20 °C, the reaction mixture was filtered through a pad of
celite and the filtrate was concentrated under reduced pres-
sure to give the crude product. Purification of this material
was accomplished by flash chromatography on silica gel
with 10% ethyl acetate in pentane to yield the title complex
(0.650 g, 75%): mp 228–230 °C (dec); 31P NMR
(121.49 MHz, CDCl3)
d
147.6 (s, 2P); 1H NMR
(300 MHz) d 1.72 (s, 4H), 5.86 (s, 4H), 6.27 (d,
J = 9.0 Hz, 2H), 6.44 (s, 4H), 7.10 (s, 4H), 7.42 (d,
J = 3.8 Hz, 4H), 7.54 (br s, 2H), 7.88 (d, J = 9.0 Hz, 2H),
7.95 (d, J = 9.0 Hz, 2H); IR (CH2Cl2) 2082, 2048,
1948 cmꢁ1; MS (ESI+) m/z 843 [M + Na]+ (15%), 624
(17%), 453 (100%). Anal. Calc. for C40H28N4O6P2Mo: C,
58.69; H, 3.45; N, 6.84. Found: C, 59.05; H, 3.50, N, 6.64%.
2
NMR (121.49 MHz, CDCl3) d 156.6 (t, JPꢁPcis = 41 Hz,
1
1 P), 52.7 (br s, 2P); H NMR (300 MHz) d 1.89 (m, 9H),
2.48 (m, 2H), 2.84 (m, 2H), 3.38 (m, 6H), 7.27 (s, 12H),
7.55 (s, 4H), 7.68 (s, 4H); IR (CH2Cl2) 1937, 1848,
1826 cmꢁ1; MS (ESI+) m/z 769 [M + Na]+ (86%), 747
[M+H]+ (100%).
The reaction was repeated, but at 135 °C, and the crude
product (70:30, mer:fac, by 31P NMR) was purified by flash
chromatography on silica gel with 20% ethyl acetate in pen-
tane to give the more less polar complex, mer-9b (0.669 g,
60%): mp 215–218 °C (dec); 31P NMR (121.49 MHz,
4.6. Preparation of mer-10
A stirred solution of freshly prepared Mo(CO)3(DMF)3
(0.600 g, 1.50 mmol) and bis(diphenylphosphino)ethane
(0.598 g, 1.50 mmol) in 25 mL of dry toluene–DMF (4:1)
was stirred at 20 °C for 3 h. Bis(dipyrrolylphosphino)-
(R)-binol (0.916 g, 1.50 mmol) in 5 mL of toluene was then
added and the reaction mixture was heated at 135 °C for
12 h. After being allowed to cool to 20 °C, the reaction
2
2
CDCl3) d 176.2 (dd, JPꢁPcis = 24 Hz, JPꢁPtrans = 134 Hz,
2
1 P), 62.7 (d, JPꢁPtrans = 134 Hz, 1 P), 53.4 (s, 1P); 1H
NMR (300 MHz) d 1.12 (t, J = 5.6 Hz, 9 H), 2.39 (br s,
2H), 2.45 (bs, 2H), 3.90 (q, J = 5.6 Hz, 6H), 7.34 (s,
12H), 7.59 (m, 8H); IR (CH2Cl2) 2075, 2023, 1974, 1944,

1848
P. Maji et al. / Journal of Organometallic Chemistry 693 (2008) 1841–1849
Table 1
Crystallographic data for mer-9c and mer-10
mer-9c
mer-10
Identification code
Crystal colour
Crystal habit
Crystal size (mm3)
Crystal behaviour under ambient
conditions
C2
Yellowish
Platelet
P212121
Colourless
Block
0.40 ꢂ 0.40 ꢂ 0.08
0.40 ꢂ 0.22 ꢂ 0.10
Stable
Stable
Empirical formula
(C53H40NMoO5P3)1,13(C7H8)
C41H36N3MoO3P3
˚
a (A)
21.575(4)
11.638(2)
˚
b (A)
10.609(2)
24.918(5)
17.389(3)
18.716(2)
˚
c (A)
a (°)
b (°)
c (°)
90
105.55(1)
90
5495(2)
90
90
90
3787.5(9)
3
˚
V (A )
˚
k (A)
0.71073
0.71073
Crystal system
Triclinic
Orthorhombic
Space group
C2
P212121
Z
4
4
Type of diffractometer
Method of data collection
Reflections collected
Independent reflections [I > 2r(I)]
Completeness of h (°)
Absorption correction
R [I > 2r(I)] w = 1/[r2(Fo)]
Number of parameters
Refinement method
Hydrogen atoms
Bruker-Enraf-Nonius kappaCCD
/ and x scans
33214
4127 [R(int) = 0.0151]
1.00 (60)
None
R1 = 0.0500; wR2 = 0.0450
460
Full-matrix least-squares on F
Were set geometrically and recalculated before the last
refinement cycle
Bruker-Enraf-Nonius kappaCCD
/ and x scans
35710
10926 [R(int) = 0.0120]
1.00 (54)
None
R1 = 0.0435; wR2 = 0.0612
645
Full-matrix least-squares on F
Were set geometrically and recalculated before the last
refinement cycle
mixture was filtered through a pad of celite and the filtrate
was concentrated under reduced pressure to give the crude
product. Purification of this material was accomplished by
flash chromatography on silica gel with 20% ethyl acetate
in pentane to yield complex mer-10 (0.848 g, 59%): mp
258–262 °C; 31P NMR (121.49 MHz, CDCl3) d 187.8 (dd,
2JPꢁPcis = 28 Hz, 2JPꢁPtrans = 134 Hz, 1P), 61.8 (d,
2JPꢁPtrans = 140 Hz, 1P), 54.4 (s, 1P); 1H NMR
(300 MHz) d 2.10–2.72 (m, 4H), 5.80 (s, 2H), 6.50–6.57
(m, 2H), 6.70 (m,2H), 6.87–7.95 (m, 30H); IR (CH2Cl2)
1992, 1962, 1937, 1882, 1836 cmꢁ1; HRMS [M+Na]+: calc.
for C53O5P3H40NMoNa: 984.10711; Found: 984.10631.
For crystallographic data, see Table 1.
molecular modeling. Financial support from the CNRS
´
and the Universite Joseph Fourier (UMR 5250, ICMG
FR 2607) is gratefully acknowledged.
References
[1] For recent reviews on various aspect of the Pauson–Khand reaction,
see: D. Struebing, M. Beller, Top. Organometall. Chem. (2006) 165–
178;
T. Shibata, Adv. Synth. Catal. 348 (2006) 2328–2336;
S. Laschat, A. Becheau, T. Bell, A. Baro, Synlett (2005) 2547–2570;
S.E. Gibson, N. Mainolfi, Angew. Chem. Int. Ed. 44 (2005) 3022–
3037.
[2] C. Mukai, M. Uchiyama, M. Hanaoka, J. Chem. Soc., Chem.
Commun. (1992) 1014–1015;
N. Jeong, S.J. Lee, B.Y. Lee, Y.K. Chung, Tetrahedron Lett. 34
(1993) 4027–4030.
Supplementary material
[3] D.T. Rutherford, S.D.R. Christie, Tetrahedron Lett. 39 (1998) 9805–
9808;
R. Rios, S. Paredes, M.A. Pericas, A. Moyano, J. Organomet. Chem.
690 (2005) 358–362.
[4] R. Rios, M.A. Pericas, A. Moyano, Tetrahedron Lett. 43 (2002)
4903–4906.
CCDC 675266, 675267 contain the supplementary crys-
tallographic data for compounds mer-9c and mer-10. These
data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
[5] J.H. Park, S.Y. Kim, S.M. Kim, S.I. Lee, Y.K. Chung, Synlett (2007)
453–459.
[6] R.B. Grossmann, S.L. Buchwald, J. Org. Chem. 57 (1992) 5805–5807;
F.A. Hicks, S.L. Buchwald, J. Am. Chem. Soc. 118 (1996) 11688–
11689;
F.A. Hicks, S.L. Buchwald, J. Am. Chem. Soc. 121 (1999) 7026–7033.
[7] (a) C. Mukai, M. Uchiyama, M. Hnaoka, J. Chem. Soc., Chem.
Commun. (1992) 1014–1015;
Acknowledgements
We thank Professor P. Dumy for his interest in our
work, Dr. C. Philouze for the X-ray structure determina-
tions, and Ms. M.-L. Dheu-Andries for help with the

P. Maji et al. / Journal of Organometallic Chemistry 693 (2008) 1841–1849
1849
(b) N. Jeong, S.J. Lee, B.Y. Lee, Y.K. Chung, Tetrahedron Lett. 34
(1993) 4027–4030;
(c) J. Adrio, M.R. Rivero, J.C. Carretero, Org. Lett. 7 (2005) 431–
434;
(d) A.K. Gupta, D.I. Park, C.H. Oh, Tetrahedron Lett. 46 (2005)
4171–4174.
[17] J.D. Atwood, T.L. Brown, J. Am. Chem. Soc. 98 (1976) 3160–3166;
A. Kovacs, G. Frenking, Organometallics 20 (2001) 2510–2524.
[18] The importance of using electrodeficient ligands to avoid diminishing
the reactivity of the metal carbonyl complexes has already been
mentioned.15 This is even more important with complexes of W and
Mo because the first dissociative step (loss of CO) is more difficult
with these metals than with Co. Bond dissociation energy for loss of
the first CO has been shown to increase in the order: Co <Mo < W.
[19] D.J. Darensbourg, R.L. Kump, Inorg. Chem. 17 (1978) 2680–2682.
[20] For a study of the influence of the donor properties of diphosphine
ligands in tungsten carbonyl complexes, see: C. Crotti, E. Farnetti, T.
Celestino, M. Stener, S. Fontanaj, Organometallics 23 (2004) 5219–
5225.
[21] M. Pasquali, P. Leoni, P. Sabatino, D. Braga, Gazz. Chim. Ital. 120
(1992) 275–277.
[22] J.-C. Rousche, G.R. Dobson, Inorg. Chem. Acta 28 (1978) L139–
L141.
[23] G.R. Dobson, K.J. Asali, J. Marshall, C.R. McDaniel, J. Am. Chem.
Soc. 99 (1977) 8100–8108.
[24] D.J. Darensbourg, D.J. Zalewski, C. Plepys, C. Campana, Inorg.
Chem. 26 (1987) 3727–3737.
[8] R.T. Hoye, J.A. Suriano, J. Am. Chem. Soc. 115 (1993) 1154–1156.
[9] A.J. Pearson, R.A. Dubbert, J. Chem. Soc., Chem. Commun. (1991)
202–203.
[10] T. Kondo, N. Suzuki, T. Okada, T. Mitsudo, J. Am. Chem. Soc. 119
(1997) 6187–6188.
[11] N. Jeong, B.K. Sung, J.S. Kim, S.B. Park, S.D. Seo, J.Y. Shin, K.Y.
In, Y.K. Choi, Pure Appl. Chem. 74 (2002) 85–91;
F.Y. Kwong, Y.M. Li, W.H. Lam, L. Qiu, H.W. Lee, C.H. Yeung,
K.S. Chan, A.S.C. Chan, Chem.
3880;
– Eur. J. 11 (2005) 3872–
F. Nagaki, T. Kawamura, C. Mukai, Tetrahedron 63 (2007) 5154–
5160.
[12] T. Shibata, K. Takagi, J. Am. Chem. Soc. 122 (2000) 9852–9853;
Z.L. Lu, E. Neumann, A. Pfaltz, Eur. J. Org. Chem. 25 (2007) 4189–
4192.
[13] There are a number of challenging problems that must be overcome
to develop a general, catalytic, enantioselective intermolecular (or
intramolecular) Pauson–Khand varient. For a review on this topic,
see: S.E. Gibson, A. Stevenazzi, Angew. Chem. Int. Ed. 24 (2003)
1800–1810.
[14] X. Verdaguer, A. Moyano, M.A. Pericas, A. Riera, M.A. Maestro,
J. Mahia, J. Am. Chem. Soc. 122 (2000) 10242–10243;
X. Verdaguer, M.A. Pericas, A. Riera, M.A. Maestro, J. Mahia,
Organometallics 22 (2003) 1868–1877;
[25] S.C.N. Hsu, W.-Y. Yeh, J. Chem. Soc., Dalton Trans. (1998) 125–
132.
[26] K. Fukumoto, H. Nakazawa, Organometallics 26 (2007) 6505–6507.
[27] W.A. Schenk, G.H. Hilpert, Chem. Ber. 124 (1991) 433–437.
[28] R.P.K. Babu, S.S. Krishnamurthy, M. Nethaji, Organometallics 14
(1995) 2047–2052.
[29] The stereochemical assignments in the fac and mer complexes 9 have
been made by 31P NMR based on the 31P NMR of mer-9c, the
structure of which was determined by X-ray analysis.
[30] This complex was stable to purification and therefore used in place of
fac-[Mo(CO)3{g2-bis(dipyrrolylphosphino)-binol}(DMF)].
[31] The same type of transformation has been observed with bis(diet-
hoxyphosphino)-binol, but reaction with bis(diphenylphosphino)-
binol leads to a complex mixture of products devoid of both PPh3
and the complex analogous to 10.
X. Verdaguer, A. Lledo, C. Lopez-Mosquera, M.A. Maestro, M.A.
Pericas, A. Riera, J. Org. Chem. 69 (2004) 8053–8061;
J. Sola, M. Reves, A. Riera, X. Verdaguer, Angew. Chem. Int. Ed. 46
(2007) 5020–5023.
[15] For the inherent advantages in the use of bidentate, electrodeficient
ligands (C2-symmetric or not) in a bimetallic complex, see: Y.
Gimbert, F. Robert, A. Durif, M.-T. Averbuch, N. Kann, A.E.
Greene, J. Org. Chem. 64 (1999) 3492–3497;
[32] S.C. van der Slot, J. Duran, J. Luten, P.C.J. Kamer, P.W.N.M. van
Leeuwen, Organometallics 19 (2002) 3873–3883;
D. Konya, F. Robert, Y. Gimbert, A.E. Greene, Tetrahedron Lett.
45 (2004) 2975–2978.
[16] K.J. Asali, G.J. Zyl, G. Dobson, Inorg. Chem. 27 (1988) 3314–3319;
M. Ardon, G. Hogarth, D.T.W. Oscroft, J. Organomet. Chem. 689
(2004) 2429–2435.
J.-M. Brunel, G. Buono, J. Org. Chem. 58 (1993) 7313–7314.
[33] For the binol phosphoramidite (L-b) ligand, see: M.F.P. Ma, K. Li,
Z. Zhou, C. Tang, A.S.C. Chan, Tetrahedron: Asymmetry 10
(1999) 3259–3261.
[34] S. Zard, F. Gagosz, Fr. Demande (2004) FR 2844264.