Chiral dioxomolybdenum(VI) complexes for enantioselective alkene epoxidation

Article abstract of DOI:10.1016/S0022-328X(00)00790-7

Chiral dioxomolybdenum(VI) complexes of the type MoO₂Cl₂(L*) (L=oxime), MoO₂(THF)₂L* (L=cis-p-menthane-3,8-diol) and MoO₂Cl(THF)L* (L=8-phenylthioneomenthol and 8-phenylthioisoneomenthol) have been prepared in good yields by reacting MoO₂Cl₂(THF)₂ with the appropriate chiral organic bidentate O,O-, O,N- and O,S-ligands. The complexes were characterised by solution NMR (¹H, ¹³C, ⁹⁵Mo) and IR spectroscopy as well as elementary analysis, and were evaluated as catalysts in solution for the asymmetric epoxidation of cis-β-methylstyrene by tert-butylhydroperoxide (TBHP). The cis-diol complex shows high catalytic activity and enantiomeric excesses of up to 25%. An attempt was made to immobilise the complex MoO₂(THF)Cl[(-)-8-phenylthioneomenthol] within the channels of MCM-41 mesoporous silica by using a tethering ligand [L=NC(CH₂)₃Si(OEt)₃]. The material was characterised by powder X-ray diffraction (XRD), IR spectroscopy and magic-angle-spinning (MAS) NMR (¹³C, ²⁹Si). Catalytic examinations demonstrated that it was active in the epoxidation of cyclooctene by TBHP.

Full text of DOI:10.1016/S0022-328X(00)00790-7

Journal of Organometallic Chemistry 626 (2001) 1–10
www.elsevier.nl/locate/jorganchem
Chiral dioxomolybdenum(VI) complexes for enantioselective alkene
epoxidation
Isabel S. Gonc¸alves a,b, Ana M. Santos c, Carlos C. Roma˜o a,*1, Andre´ D. Lopes a,
Jose´ E. Rodr´ıguez-Borges a,d, Martyn Pillinger b, Paula Ferreira b, Joa˜o Rocha b,
Fritz E. Ku¨hn c,*2
a Instituto de Tecnologia Qu´ımica e Biolo´gica da Uni6ersidade No6a de Lisboa, Quinta do Marqueˆs, EAN, Apt 127, 2781-901 Oeiras, Portugal
b Departamento de Qu´ımica, Uni6ersidade de A6eiro, Campus de Santiago, 3810-193 A6eiro, Portugal
c Anorganisch-chemisches Institut der Technischen Uni6ersita¨t Mu¨nchen, Lichtenbergstraße 4, D-85747 Garching bei Mu¨nchen, Germany
d Departamento de Qu´ımica Orga´nica, Facultade de Farmacia, Uni6ersidade de Santiago de Compostela, E-15706 Santiago de Compostela, Spain
Received 10 August 2000; received in revised form 15 August 2000; accepted 10 October 2000
Dedicated to Professor Dr Henri Brunner on the occasion of his 65th birthday
Abstract
Chiral dioxomolybdenum(VI) complexes of the type MoO2Cl2(L*) (L*=oxime), MoO2(THF)2L* (L*=cis-p-menthane-3,8-
diol) and MoO2Cl(THF)L* (L*=8-phenylthioneomenthol and 8-phenylthioisoneomenthol) have been prepared in good yields by
reacting MoO2Cl2(THF)2 with the appropriate chiral organic bidentate O,O-, O,N- and O,S-ligands. The complexes were
characterised by solution NMR (1H, 13C, 95Mo) and IR spectroscopy as well as elementary analysis, and were evaluated as
catalysts in solution for the asymmetric epoxidation of cis-b-methylstyrene by tert-butylhydroperoxide (TBHP). The cis-diol
complex shows high catalytic activity and enantiomeric excesses of up to 25%. An attempt was made to immobilise the complex
MoO2(THF)Cl[(−)-8-phenylthioneomenthol] within the channels of MCM-41 mesoporous silica by using a tethering ligand
[L=NC(CH2)3Si(OEt)3]. The material was characterised by powder X-ray diffraction (XRD), IR spectroscopy and magic-angle-
spinning (MAS) NMR (13C, 29Si). Catalytic examinations demonstrated that it was active in the epoxidation of cyclooctene by
TBHP. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Molybdenum complexes; Chiral ligands; Enantioselective epoxidations; Heterogeneous catalysis; Mesoporous materials; Supported
catalysts
1. Introduction
enantioselective epoxidation of unfunctionalized olefins
when coordinated to dioxo and peroxomolybde-
num(VI) fragments. However, the reported enan-
tiomeric excess (ee) values are modest (ca. 20–40%). In
the context of olefin epoxidation, some of us recently
reported the synthesis of a broad variety of cis-MoO22+
epoxidation catalysts of the type MoO2X2Ln (X=Cl,
Br, CH3) with mono- and bidentate nitrogen and oxy-
gen ligands [5]. This work was subsequently extended to
include chiral bis(oxazoline) and 2%-pyridyl alcohol lig-
ands [6]. The resulting chiral dioxomolybdenum(VI)
complexes exhibited good catalytic activity for the
epoxidation of trans-b-methylstyrene with t-butylhy-
droperoxide (TBHP) with optical induction values in
the range of those mentioned above. In these studies it
The well recognized catalytic activity of the oxo-
molybdenum(VI) complexes in oxidation reactions and
the recent increasing importance of enantioselective cat-
alytic processes led to the search of oxomolybdenum
catalysts able to perform enantioselective oxidation re-
actions [1]. Following the simplest approach to obtain
enantioselective transformations at a metal center, chi-
ral ligands like 2%-pyridyl alcohols [2,3] and phosphi-
noylalcohols [4] have been reported recently to induce
1 *Corresponding author. Tel.: +351-1-446-9751; fax: +351-1-
441-1277; e-mail: ccr@itqp.unl.pt
2 *Corresponding author. Tel.: +351-1-446-9751; fax: +351-1-
441-1277
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(00)00790-7

2
I.S. Gonc¸al6es et al. / Journal of Organometallic Chemistry 626 (2001) 1–10
was observed that the catalytic activity strongly de-
pends on the nature of the ligands X and L in the
MoO2X2Ln complexes. The higher electronegativity of
X clearly accelerates the epoxidation reaction but the
decisive effects of the ligands L are unclear either upon
the activity or upon the enantioselectivity.
2. Results and discussion
2.1. Chiral ligand synthesis
The starting materials used for the synthesis of the
chiral ligands were cis-p-menthane-3,8-diol (1) and (R)-
(+)-pulegone (4), a commercially available natural
product. Oxidation of 1 with CrO3 in pyridine/
dichloromethane gave the ketone derivative (+)-
(2R,5S)-2-(1-hydroxy-1-methylethyl)-5-methylcyclo-
hexanone (2) [10]. Treatment of 2 with hydroxylamine
In this situation we decided to take a further step in
the characterization of new MoO2X2Ln catalysts bear-
ing other simple chiral ligands of readily accessible
preparation before attempting the upgrade of this sys-
tem by means of the more recently elaborated concepts
on the mechanism of chirality control in enantioselec-
tive synthesis [1b]. The nature of the best performing
simple ligands in terms of activity and chiral properties
will certainly be of use for the design of more efficient
ligand sets.
hydrochloride
and
4-dimethylaminopyridine
in
methanol then gave the chiral oxime 3 (Scheme 1) [11].
The 8-phenylthiomenthones 5 and 6 were obtained
from 4 as a mixture of cis and trans isomers but
otherwise highly pure as evidenced by spectral analysis
(see experimental) (Scheme 2). Separation of the iso-
mers was achieved by careful medium pressure chro-
matography on silica gel [12]. The chiral oxime 7 was
prepared from 5 as described above for 3. Following
the method of Vollhardt [13a], reduction of 5 and 6
Under this light we now wish to report on the
exploration of the catalytic behaviour of a series of
dioxomolybdenum(VI) complexes with chiral cis-diol
and cis-8-phenylthiomenthol ligands derived from (R)-
(+)-pulegone, and their corresponding oxime deriva-
tives both in homogeneous and heterogeneous
(supported) conditions with respect to olefin epoxida-
tion. These ligands, e.g. oximes, thioethers, were chosen
because they represent less studied types of ligands in
this field of chemistry, are very easily accessible and
have appropriate properties for the heterogenization in
mesoporous supports. In fact, the relatively small size
of these ligands allows their confinement in the large-
pore molecular sieves, a process that may provide a
route to effective asymmetric heterogeneous catalysts
[7]. As an example, the tethering of chiral dioxomolyb-
denum(VI) complexes with bidentate O,O-ligands to
the internal surface of a mesoporous USY-zeolite af-
forded a catalyst for the asymmetric epoxidation of
allylic alcohols [8]. We recently described the hetero-
genisation of the dioxomolybdenum(VI) fragment
MoO2X2 within ordered mesoporous MCM-41 silica by
using a tethering ligand [L=NC(CH2)2Si(OEt)3] [9].
We have applied the same methodology in the work
reported here to try to immobilize a chiral dioxomolyb-
denum(VI) complex.
with
L-Selectride gave the optically active 8-phenyl-
thiomenthols 8 and 9 that were straightforwardly sepa-
rated by chromatography on silica gel [13]. All the
desired ligands were available in high optical purity and
were fully characterised.
2.2. Synthesis of chiral dioxomolybdenum(VI) complexes
The complexes obtained by reacting the organic lig-
ands 1, 3 and 7–9, with MoO2Cl2(THF)2 in CH2Cl2
solvent, in a 1:1 molar ratio, are numbered 1a, 3a and
7a–9a, respectively. They are formed in good yield
after evaporation of the reaction mixture and washing
with hexane. The complexes were characterized by ele-
mental analysis and spectroscopic techniques.
Analysis of 1a indicates the stoichiometry
MoO2(THF)2{(+)-cis-p-menthane-3,8-olato} implying
that 2 equivalents of HCl were liberated during the
reaction (Chart 1). With this stoichiometry the complex
has a 6-coordinated environment with two THF ligands
attached. The complex is very air sensitive decomposing
within a few seconds when exposed to air. The IR
indicates that this complex has a cis-MoO2 stereochem-
istry. Since only one signal is observed in the 95Mo-
NMR, either only one isomer is present or, most likely,
the complex 1a is fluxional or labile in solution. We did
not pursue the definitive structural assigment further.
Treatment of one equivalent of the oxime ligands 3
and 7 with MoO2Cl2(THF)2 gave the complexes of the
type MoO2Cl2L* (L*=oxime ligand) in nearly quanti-
tative yields (Chart 1). The product complexes 3a and
7a are soluble in dichloromethane and precipitated
Scheme 1. (a) CrO3/Py/Ch2Cl2/r.t./45 min. (b) H2NOH·HCl/DMAP/
MeOH/r.t./24 h.

I.S. Gonc¸al6es et al. / Journal of Organometallic Chemistry 626 (2001) 1–10
3
Scheme 2. (a) HSPh/NaOH/Zn/CuBr/THF/D/8 h. (b) H2NOH·HCl/DMAP/MeOH/r.t./24 h. (c) (i) L-selectride/THF/0°C/4 h. (ii) NaOH/H2O2
(30%)
or pentane. These characteristics are similar to those
reported by us for the corresponding chiral 2%-pyridyl
alcoholate derivatives with the same general formula
MoO2Cl(THF)L* [6].
from the reaction mixture upon addition of ether. They
are stable at room temperature and can be handled in
air for brief periods of time (several minutes). The
stoichiometry of 3a and 7a indicates that a simple
adduct was formed and no HCl was liberated. Their IR
spectra clearly show the presence of the OH groups but
it is not easy to decide between a O/N and a O/O
coordination. As depicted in Chart 1, we believe that
the complexes have a O/N coordination based upon
their higher stability, a more favorable chelating ring
and the 95Mo data, discussed below.
The complexes 1a, 3a, 6a–9a display their symmetric
and asymmetric IR MoꢀO stretching vibrations in the
expected range (916–962 cm−1) [5,6,14]. The other
bands in the IR spectra are assigned to the vibrational
signals of the bound ligands. This shows that the
thioether ligands were not oxidized by oxygen transfer
from the Mo to the S atom. Besides, no colour change
indicative of Mo(VI) reduction to Mo(IV) (or MoV)
was observed. With this evidence in hand, the thioether
ligands are considered to play their usual role as weak,
labile ligands to the hard MoVIO2 center.
The solubility of the dioxomolybdenum complexes
enable good quality 95Mo-NMR spectra to be obtained,
which displayed their signals in the region between 150
and 320 ppm (Table 1). The 95Mo-NMR signals of
complexes 1a and 8a, with O,O- and O,S-ligands, re-
spectively, appear at higher field [l(95Mo)=183 and
153 ppm] compared to complexes 3a and 7a
with O,N-ligands [l(95Mo)=241 and 320 ppm].
These results are in agreement with data obtained
for other MoO2Cl2L2 complexes containing oxygen lig-
ands L, e.g. MoO2Cl2(CH3COCHC(N(H)Me)CH3)2
Chart 1.
The complexes of stoichiometry MoO2Cl(THF)L*
(8a and 9a) were also prepared from MoO2Cl2(THF)2
and the thioether-alcohol ligands (Scheme 3). Again,
liberation of HCl took place and both complexes are
air and moisture sensitive and can only be handled and
stored under moisture-free inert gas atmosphere. Com-
plex 9a could be characterised in the solid state (analy-
sis and IR) but a solution of the complex in deuterated
solvent was too unstable and it was not possible to
obtain consistent NMR data. These complexes (8a and
9a) are more soluble in organic solvents compared to
the oxime derivatives 3a and 7a, and do not precipitate
from the reaction mixtures. They are soluble in diethyl
ether and can only be purified by washing with hexane
Scheme 3.

4
I.S. Gonc¸al6es et al. / Journal of Organometallic Chemistry 626 (2001) 1–10
Table 1
ment of the chiral ligand.
95Mo-NMR data of the complexes (CD2Cl2, room temperature)
We recently showed that the dioxomolybdenum(VI)
fragment MoO2X2 could be confined within the chan-
nels of the mesoporous silica MCM-41 by reaction of
MoO2Cl2(THF)2 with the nitrile-functionalised material
MCM-41-Si(OEt)nCH2CH2CN [9]. The nitrile groups
replace coordinated THF molecules. Interest in the
synthesis of asymmetric heterogeneous catalysts led us
to examine whether this methodology could be used to
immobilise the chiral complex 8a.
Compound
l(95Mo) (ppm)
Dw1/2 (Hz)
1a
3a
7a
8a
183
241
320
153
180
210
370
102
MCM-41 was prepared as described in the literature
using [(C14H29)NMe3]Br as the surfactant template. The
powder XRD pattern of the calcined MCM-41 can be
indexed on a hexagonal unit cell (using the strongest
,
reflection, d100, a=45.73 A). The pattern also displays
a broad secondary feature at about 4.6° 2q where (110)
and (200) reflections would be expected for a hexago-
nally ordered material such as MCM-41 (Fig. 1). The
absence of resolved peaks indicates that any structural
order of the material did not extend over a long range.
A very similar result was obtained by Schmidt et al. for
a purely siliceous MCM-41 prepared as in this work
using the same surfactant [15].
The derivatised material MCM-41–Si(OEt)nCH2-
CH2CH2CN (10) was prepared by diffusion of an ex-
cess of 4-(triethoxysilyl)butyronitrile in toluene, into
calcined and dehydrated MCM-41 for 48 h (Scheme 4).
The powder was washed repeatedly with dichloro-
methane to remove the unreacted nitrile and dried in
vacuum at room temperature for several hours. Reac-
tion of the nitrile-functionalised material 10 with the
dioxomolybdenum complex 8a in CH2Cl2 at room tem-
perature gave a visibly air-sensitive pale blue powder
(11) that contained 0.5 mass% Mo and 0.76% Cl. The
powder XRD data for the functionalised materials 10
and 11 were consistent with retention of the hexagonal
mesoporous structure throughout the grafting and teth-
ering processes (Figure 1).
Fig. 1. Powder XRD patterns of calcined (pristine) MCM-41 and
functionalised samples 10 and 11.
The 29Si-MAS and CP MAS-NMR spectra of MCM-
41-Si(OEt)nCH2CH2CH2CN (10) displayed peaks be-
tween l= −110 and −92 assigned to Qn units of the
silica framework [Qn=Si(OSi)n(OH)4−n, n=2–4] and
additional peaks between l= −62 and −54 assigned
to Tm units of the grafted organosilica species [Tm=
RSi(OSi)m(OEt)3−m, m=1–2] (Fig. 2). As expected,
grafting of the triethoxysilyl ligand on the internal silica
surface of MCM-41 resulted in a decrease in the rela-
tive intensity of the Q2/Q3 resonances and a concomi-
tant increase in the intensity of the Q4 resonance. This
is consistent with the IR spectrum which showed char-
acteristic absorption bands for the covalently-linked
organic groups [w(NꢁC)=2257 cm−1]. The 29Si-NMR
spectra changed only slightly after material 10 was
treated with complex 8a. IR bands for the two cis-
MoꢀO stretching modes could not be seen clearly due
to the small percentage of molybdenum in the material.
Scheme 4.
[l(95Mo)=160 ppm] [5b] and also with data obtained
for MoO2Cl2L% complexes containing imine ligands L%
2
which give l(95Mo) signals in the region of 220 ppm
[5b] and pyridine–alcoolate (py–O) derivatives of
MoO2Cl(py–O) which have these resonances at ca. 260
ppm [6].
2.3. Synthesis of deri6atised mesoporous materials
Complex 8a is labile. When prepared in dichloro-
methane or THF, the formulation MoO2Cl(THF)L*
(8a) is obtained but dissolution and recrystalisation
from NCMe gave the NCMe adduct MoO2Cl-
(NCMe)L* (1H-NMR evidence). However, reaction of
8a with pyridine in dichloromethane leads to decom-
postition to unidentified products with total displace-

I.S. Gonc¸al6es et al. / Journal of Organometallic Chemistry 626 (2001) 1–10
5
The 13C CP MAS-NMR spectrum of MCM-41-
Si(OEt)nCH2CH2CH2CN (10) exhibited one faint peak
at l=118.3 attributed to NCR, two peaks at l=58.3
and 19.1 attributed to the ethoxide group, and two
well-defined peaks at l=16.6 and 10.5 attributed to
NC–CH2– and –CH2–CH2–Si respectively. The 13C
CP MAS-NMR spectrum of material MCM-41-
Si(OEt)n(CH2)3CN/8a (11) was similar except that the
peaks corresponding to the ethoxide group were rela-
tively less intense compared to the peaks corresponding
to the NC–(CH2)3–Si fragment. Also, the resonance at
l=119.4 attributed to NꢁC was shifted downfield
slightly compared to 10 as a result of coordination to
the MoO2Cl fragment. The spectrum did not display
any additional resonances that could be assigned to the
chiral ligand, suggesting that the latter was lost during
the reaction of 8a with 10.
2.4. Dioxomolybdenum(VI) complexes in epoxidation
catalysis
Fig. 2. 29Si-MAS and CP MAS-NMR spectra of calcined (pristine)
MCM-41 and functionalised samples 10 and 11.
The design of new metal catalysts for highly enan-
tioselective epoxidation of unfunctionalised olefins is
still an area of active research despite the success of
Mn–salen and metalloporphyrin complexes [1]. Some
effort has focussed on the isolation of highly reactive
and chiral oxometal complexes. It is hoped that exami-
nation of their reactivities towards asymmetric alkene
epoxidations will partly provide a clue to the factors
affecting enantioselectivity [16]. A chiral dioxorutheni-
um(VI) porphyrin complex was recently shown to
catalyse enantioselective aerobic oxidation of cis-b-
methylstyrene with 70% ee [16c]. In the field of molyb-
denum(VI) chemistry, enantiomeric excesses of up to
53% are known with functionalised olefins as substrate,
e.g. allylic alcohols [17], whereas for unfunctionalised
olefins enantioselective epoxidation is much more
difficult. For example, reaction of squalene with TBHP
in the presence of 1 mol% of MoO2(acac)2/diisopropyl
tartrate gives 2,3-oxidosqualene in only 14% ee [18].
More recent studies report ee’s of up to 25% for the
oxidation of trans-b-methylstyrene by TBHP in the
presence of chiral dioxomolybdenum(VI) pyridyl alco-
holate complexes [2,6].
Complexes 1a, 3a and 7a–9a were evaluated as cata-
lysts for the asymmetric epoxidation of cis-b-methyl-
styrene using tert-butylhydroperoxide as oxidant and
toluene as solvent at 55°C. The ratio sub-
strate:oxidant:catalyst used was 100:200:1. Catalytic
runs are shown in Fig. 3 and results are summarized in
Table 2. For the five complexes studied, the reactions
proceeded with high retention of configuration and
high selectivity to the epoxide but only the cis-diolato
complex 1a produces significant optical induction. The
(1R,2R)-cis-b-methylstyrene oxide was formed in 20–
24% ee from the initial stages of the reaction to the end
(24 h). After a quick increase in the yield within the first
Fig. 3. Kinetic profile of epoxidation of cis-b-methylstyrene by TBHP
at 55°C in the presence of the chiral cis-diol complex 1a and oxime
3a, cis-phenylthiomenthol complexes 8a and 9a, and oxime 7a.
Table 2
Results of catalytic epoxidation of cis-b-methylstyrene by TBHP at
55°C in the presence of the chiral cis-diol complex 1a and oxime 3a,
cis-phenylthiomenthol complexes 8a and 9a, and oxime 7a a
Compound TOF b/mol
Conversion c (%) ee (%)
−1
cat
(mol
min−1
)
1a
3a
7a
8a
9a
7.05
0.52
0.59
7.00
3.30
72
63
72
67
82
23.8 (R,R)
1.3 (R,R)
1.5 (R,R)
2.2 (R,R)
–
a See text and Section 3 for reaction details.
b Initial turnover frequency, calculated after 5 min reacting.
c Conversion and ee calculated after 4 h reacting.

6
I.S. Gonc¸al6es et al. / Journal of Organometallic Chemistry 626 (2001) 1–10
hour the reaction velocity slowed down and conversion
reached 86% after 24 h. The complexes 7a–9a, contain-
ing one alcoholate and one phenylthio ligand did not
give rise to significant enantiomeric excesses in the
epoxidation of cis-b-methylstyrene. However, complex
9a proved to be the more active catalyst in this series.
After 30 minutes the conversion was similar to that
obtained with complex 1a but it didn’t slow down so
rapidly, proceeding to complete conversion of the sub-
strate within 24 h with 100% selectivity to the epoxide.
Quite interestingly, complex 8a with another enan-
tiomeric form of the same ligand exhibited a slightly
different kinetic profile in which, after a very rapid
increase in yield in the first 5 min, product formation
increased slowly but steadily from 40% after 30 min to
90% after 24 h reaction. These results deserve some
comment in the context of exploring new ligands for
the catalytic epoxidation with MoO2X2L2 systems. In
fact, at first sight sulfur ligands do not seem to be
appropriate for this kind of oxidative chemistry since
the S atom will quite likely be oxidized to a sulfoxide or
a sulphone. In the present study we did not try to
establish these facts but the results obtained with 9a
clearly show that the sulphur containing ligand 9 pro-
vides one of the most active, selective and chemically
resistant catalyst of all the MoO2X2L2 systems that we
studied so far [5]. Unfortunately, it wasn’t possible to
ascertain the degree of lability of the thioether ligand in
9a. However, it is quite likely that the dissociation of
the SPh group under catalytic conditions leads to the
formation of a S(O)Ph ligand which can bind the
Mo(VI) center by its O atom in the same fashion as
DMSO or DMF [22] or phosphine oxides [4] coordi-
nate such centers to produce catalytic oxygen transfer
systems. One can thus speculate that the expected labil-
ity of the sulphoxide ligand and its chemical resistance
to oxidation may provide an explanation for the higher
activity and chemical stability of this system since the
Mo centre becomes easily accessible to reactants (by
S(O)Ph dissociation) and readily protected (by ready
association of the pendant S(O)Ph group.
requires the chiral ligand to remain chelated the
MoVIO2 center. Opening of the chelating ring will con-
tribute to a faster reaction but to a loss of enantioselec-
tivity. Such opening may be accelerated by the
accumulation of excess t-BuOH in the reaction mixture
as by product of the oxidation. A lowering of the
enanstioselectivity along increasing conversion was de-
scribed by Haider in the epoxidation of cis-b-methyl-
styrene catalysed by a chiral 2%-pyridine alcoholate
derived from fenchone, MoO2(fenpy)2 [1c]. The loss of
selectivity along the reaction evolution was attributed
to opening of the chelation by protonation of the
Mo–O bond of one fenpy ligand. A similar behaviour
can be expected to take place in a diolate complex like
1a.
The dioxomolybdenum-functionalised MCM (11)
was tested as a catalyst for the epoxidation of cy-
clooctene with TBHP as oxygen source at 55°C (see
Section 3 for more details). After a very quick increase
in the yield within the first 5 min the reaction velocity
slowed down. Similar results were obtained with MCM-
41-grafted MoO2Cl2NCCH2CH2Si(OEt)3 [9]. The yield
of cyclooctene oxide formed was 31% after 15 min,
increasing to 41% after 4 h (65–70% selectivity to the
epoxide). An initial turnover frequency of 0.86 mmol
cyclooctene oxide per g of catalyst per min was
achieved, or 1.7 mol cyclooctene oxide per mol molyb-
denum atoms per min. A possible explanation for the
sudden decrease in activity is the reaction of the teth-
ered dioxomolybdenum complex with tert-butanol. It
has previously been reported that the epoxidation of
1-octene by a TiO2-on-SiO2 catalyst and TBHP in
benzene at 80 °C exhibits marked autoretardation, at-
tributed to the formation of tert-butanol during the
epoxidation process [17]. Reactions were also per-
formed with parent calcined MCM-41 and the ligand-
grafted material MCM-41-Si(OEt)n(CH2)3CN (10) and,
as expected, neither material showed significant activity
in the epoxidation of cyclooctene. After 4 h reacting,
conversions were 5% for MCM-41 and 10% for 10.
MCM-41 was found previously to be inactive in cyclo-
hexene epoxidation with TBHP [18].
In contrast, the reaction in the presence of the oxime
derivatives 3a and 7a was sluggish and conversion of
the substrate only reached ca. 30% after about 1 h.
Nevertheless, the reaction proceeded smoothly and the
product yield increased to 90% after 24 h. Both profiles
are essentially parallel showing that the presence of an
oxidizable sulfur in the thioether ligand is not impor-
tant for the rate of the reaction. Instead, the presence of
the N bound oxime ligand clearly slows down the
reactivity of these complexes compared to the alcoho-
lates. In any case, the optical induction of all the
thioether and oxime containing complexes is very low.
The latter observation together with the fact that 9a
does not produce any optical induction seems to rein-
force our belief that enantioselectivity in this systems
In conclusion we note that the most active catalysts
or catalyst precursors studied in this work, 1a and 9a,
were very moisture sensitive alcoholates. Their overall
activity in olefin epoxidation is among the best of all
MoO2X2L2 and MoO2(py–O)2 complexes studied so
far. This excellence also complies for the enantioselec-
tivity of 1a (but not 9a) which also ranks very high
among all previous results with the above mentioned
MoO2 derived complexes. The difference in activity
between 8a and 9a is most remarkable since the only
noticeable difference between both complexes is the
chirality of the ligand. Definitive benchmark tests as
well as tests with other diols are presently under way in
our laboratories. In particular, BINOL and other biaryl

I.S. Gonc¸al6es et al. / Journal of Organometallic Chemistry 626 (2001) 1–10
7
alcohols are under careful observation because they can
open an entry to more advanced configuration control
as discussed by Bolm in his recent critical review [1b].
Theoretical and experimental studies are also being
carried out in order to clarify the mechanism of oxida-
tion with the MoO2X2L*/TBHP system. NMR results
The hexagonal channel host MCM-41 was synthe-
sised using [(C14H29)NMe3]Br according to published
procedures [19]. After calcination (540°C/6 h), the ma-
terial was characterised by powder XRD and FTIR
spectroscopy. The precursor materials MoO2Cl2 [20]
and MoO2Cl2(THF)2 [21] were prepared as described
previously. (+)-cis-p-menthane-3,8-diol (1) and (R)-
(+)-pulegone (4) were purchased from Aldrich and
used as received.
1
(17O, H, 95Mo) have shown that TBHP interacts with
MoO2Cl2L (L=2%-pyridyl alcoholate) complexes to
produce slightly displaced resonances which are repro-
ducible experimentally [6]. A peroxometal reaction
pathway is therefore assumed whereby the electron
deficient d0 metal center acts as a Lewis acid activating
the hydroperoxide.
Due to the lability of the chiral ligands these com-
plexes are not appropriate to prepare eneantioselective
catalysts by support on mesoporous MCM-41
materials.
3.2. Chiral ligand synthesis
3.2.1. (+)-(2R,5S)-2-(1-Hydroxy-1-methylethyl)-5-
methylcyclohexanone (2)
To a solution of pyridine (22.4 g, 278 mmol) in
dichloromethane (230 ml) at 0°C was added CrO3
(13.92 g, 139.20 mmol). The solution was stirred for 15
min at room temperature and then treated with a
solution of (+)-cis-p-menthane-3,8-diol (4.0 g, 23.2
mmol) in dichloromethane (40 ml). After stirring for 45
min, the mixture was filtered through Celite and the
residue washed several times with diethyl ether (150
ml). The combined filtrate and washings were concen-
trated and washed with 10% NaOH (2×60 ml) and
brine (100 ml). The combined organic layers were dried
over Na2SO4 and the solvent removed to give an oil
(4.1 g) purified by flash chromatography (hex-
ane:EtOAc; 3:7). Yield: 3.52 g (89%). Anal. Calc. for
C10H18O2 (170.25): C, 70.55; H, 10.66. Found: C, 70.23;
H, 10.46%. [h]2D0 +3.7 (c 1, CDCl3). IR (neat, w cm−1):
3479 vs, 2957 vs, 2930 vs, 2874 s, 1699 vs, 1458 s, 1377
3. Experimental
3.1. Materials and methods
All preparations and manipulations were carried out
using standard Schlenk techniques under an atmo-
sphere of nitrogen. Solvents were dried by standard
procedures (THF, n-hexane and Et2O over Na/ben-
zophenone ketyl; CH2Cl2 and NCMe over CaH2), dis-
,
tilled under argon and kept over 4A molecular sieves
,
(3A for NCMe).
Microanalyses were performed at the ITQB and the
Mikroanalytische Labor of the Technical University of
Munich (M. Barth). IR spectra were measured on a
Unican Mattson Mod 7000 FTIR spectrometer and a
Perkin–Elmer FT-IR spectrometer using KBr pellets.
Powder XRD data were collected on a Phillips X’pert
diffractometer using Cu–Ka radiation filtered by Ni.
1H-NMR solution spectra were recorded at 300 MHz
and 400 MHz on Bruker CXP 300 and Bruker Avance
DPX-400 spectrometers respectively. 13C-NMR solu-
tion spectra were measured at 100.28 MHz on a JEOL
JNM GX-400 and a Bruker Avance DPX-400. 95Mo-
NMR solution spectra were measured at 26.07 MHz on
a Bruker Avance DPX-400. 29Si- and 13C- solid-state
NMR spectra were recorded at 79.49 and 100.62 MHz
respectively, on a (9.4 T) Bruker MSL 400P spectrome-
ter. 29Si MAS-NMR spectra were recorded with 40°
pulses, spinning rates 5.0–5.5 kHz and 60 s recycle
delays. 29Si CP MAS-NMR spectra were recorded with
1
s, 1362 s, 1160 s, 943 s, 804 m, 619 m, 548 m. H-NMR
(CDCl3, 300 MHz, r.t., l ppm): 3.95 (s, 1H, OH);
2.40–2.32 (m, 2H); 2.22–1.89 (m, 4H); 1.57–1.40 (m,
2H); 1.23 (d, 6H, CH3); 1.02 (d, 3H, CH3). 13C-NMR
(CDCl3, 300 MHz, r.t., l ppm): 216.44; 72.44; 60.17;
52.85; 36.92; 35.30; 30.09; 26.90; 23.37.
3.2.2. (+)-(2S,5S)-2-(1-Hydroxy-1-methylethyl)-5-
methylcyclohexanone oxime (3)
Into a 100 ml round-bottomed flask containing an
efficient stirring bar was added a solution of 2 (3.0 g,
17.62 mmol), hydroxylamine hydrochloride (6.18 g,
88.0 mmol), 4-dimethylaminopyridine (DAMP) (2.37 g,
19.4 mmol) and MeOH (58 ml). The reaction mixture
was stirred for 24 h at room temperature (r.t.). The
mixture was diluted with water (200 ml) and extracted
with ether (4×80 ml). The combined organic layers
were washed with 1.0 M HCl (2×60 ml) and brine (100
ml). The organic solution was dried over Na2SO4 and
the solvent removed to give a yellow solid (3.2 g)
purified by recrystallization from cyclohexane to yield a
white solid (3.13 g, 96%). Anal. Calc. for C10H19NO2
(185.27): C, 64.83; H, 10.34; N, 7.56. Found: C, 64.68;
H, 10.22; N, 7.66%. M.p. 115–117°C. [h]2D0 +34.5 (c 1,
CHCl3). IR (KBr, w cm–1): 3416 vs (OH), 3234 vs, 3103
1
5.5 ms H 90° pulses, 8ms contact time, a spinning rate
of 4.5 kHz and 4 s recycle delays. Chemical shifts are
quoted in parts per million from TMS. 13C CP MAS-
1
NMR spectra were recorded with a 4.5 ms H 90° pulse,
2 ms contact time, a spinning rate of 8 kHz and 4 s
recycle delays. Chemical shifts are quoted in parts per
million from TMS.

8
I.S. Gonc¸al6es et al. / Journal of Organometallic Chemistry 626 (2001) 1–10
vs, 2971 vs, 2921 s, 2868 s, 1668 vs, 1467 s, 1402 s, 1381
s, 1251 s, 1170 s, 964 s, 941 s, 891 m, 768 m, 673 s, 642
s, 545 m. H-NMR (CDCl3, 300 MHz, r.t., l ppm):
vs (OH), 3055 m, 2951 vs, 2924 vs, 2866 s, 1651 vs,
1445 s, 1381 s, 1229 s, 1134 s, 939 s, 899 m, 754 m, 695
s, 665 s, 594 m. H-NMR (CDCl3, 300 MHz, r.t., l
1
1
8.43 (s, 1H, OH); 5.24 (s, 1H, OH); 3.45–3.39 (m, 2H);
2.20–2.15 (m, 2H); 2.01–1.95 (m, 2H); 1.81 (m, 2H);
1.19 (d, 6H, CH3); 1.00 (d, 3H, CH3).
ppm): 7.52 (s, 1H, OH); 7.51–7.26 (m, 5H, Ph), 3.31–
3.26 (m, 1H); 2.57–2.52 (m, 1H); 2.17–2.12 (m, 1H);
1.92–1.87 (m, 1H); 1.61–1.57 (m 2H); 1.41 (d, 6H,
CH3); 1.35–1.31 (m, 1H); 1.27–1.15 (m, 1H); 0.98 (d,
3H, CH3). 13C-NMR (CDCl3, 300 MHz, r.t., l ppm):
161.19; 138.06; 132.80; 128.83; 125.11; 52.63; 52.01;
34.94; 34.00; 30.07; 28.41; 25.47; 22.19.
3.2.3. (−)-(2R,5R)-2-[1-Methyl-1-(phenylthio)ethyl]-5-
methylcyclohexanone (5)
A suspension of thiofenol (14.4 g, 130.7 mmol), zinc
(1.0 g, 15.3 mmol), copper (I) bromide (1.8 g, 12.5
mmol), (R)-(+)-pulegone (18.1 g, 118.9 mmol), 10%
NaOH (1 ml) and THF (60 ml) was stirred and refluxed
for 8 h under a nitrogen atmosphere. The reaction was
allowed to cool to ambient temperature, followed by
the addition of 1.0 M HCl (200 ml) and diethyl ether
(100 ml). The mixture was filtered through Celite and
the residue washed several times with diethyl ether (100
ml). The combined organic layers were washed with 1.0
M HCl (2×100 ml), brine (200 ml), dried over Na2SO4,
and the solvent removed to give a mixture of 5 and 6
(33.7 g) as indicated by NMR (5:6=86:14). The mix-
ture was purified by flash chromatography (hex-
ane:ether; 9:1) to afford the pure phenylthioketone 5
(9.2 g, 29%) and a mixture of 5+6 (18.1 g, 58%) with
a diastereomeric relation 79:21 as indicated by 1H-
NMR. Anal. Calc. for C16H22OS (262.41) 5: C, 73.24;
H, 8.45. Found: C, 73.03; H, 8.41%. M.p. 30–32 °C.
[h]D20 −38.2 (c 1, CHCl3). IR (KBr, w cm–1): 3088 m,
3059 m, 3022 m, 2955 vs, 2926 vs, 2872 vs, 1710 vs,
1496 s, 1364 s, 1205 s, 1122 s, 1091 s, 771 s, 700 vs, 565
3.2.5. (−)-(1S,2R,5R)-2-[1-Methyl-1-
(phenylthio)ethyl]-5-methylcyclohexanol (8) and
(−)-(1R,2S,5R)-2-[1-methyl-1-(phenylthio)ethyl]-
5-methylcyclohexanol (9)
Method (a): to an L-Selectride solution (2.86 ml 1.0
M in THF, 2.86 mmol) at 0°C was added dropwise via
syringe a solution of 5 (0.5 g, 1.9 mmol) in THF (4 ml).
The reaction mixture was stirred for 4 h at 0°C after
which aqueous 3 M NaOH (1 ml) was added dropwise
followed by slow addition of 30% H2O2 (1 ml), result-
ing in an exothermic reaction. The solution was allowed
to warm to ambient temperature, stirred for 30 min,
and extracted with diethyl ether (4×40 ml). The com-
bined organic portions were washed with water (50 ml),
brine (60 ml) and dried over Na2SO4. The solvent was
removed to give an oil (0.51 g) purified by flash chro-
matography (hexane:ether; 9:1) to afford the pure
phenylthioalcohol 8 (0.49g, 99%).
Method (b): to an L-Selectride solution (97.0 ml 1.0
M in THF, 97.1 mmol) at 0°C was added dropwise via
syringe a solution of the diastereomeric mixture (5:6=
79:21) (16.98 g, 64.75 mmol) in THF (75 ml). Using the
treatment from method (a) we isolated a mixture of
diastereomers of the two alcohols (8:9=78:22 by
NMR) which were purified by flash chromatography
(hexane:ether; 19:1). The first fraction was identified as
9 (3.55 g, 20.7%). Anal. Calc. for C16H24OS (264.43): C,
72.68; H, 9.15. Found: C, 72.47; H, 9.02%. M.p. 60–
61°C. [h]2D0 −1.2 (c 1, CHCl3). IR (KBr, w cm–1): 3545
vs, 3065 m, 2943 vs, 2912 vs, 2872 s, 2852 m, 1651 vs,
1456 s, 1437 s, 1359 s, 1257 m, 1203 s, 1130 s, 1069 m,
1
s. H-NMR (CDCl3, 300 MHz, r.t., l ppm): 7.51–7.31
(m, 5H, Ph); 2.83–2.77 (m, 2H); 2.36–2.25 (m, 2H);
1.96–1.94 (m, 2H); 1.63–1.57 (m, 2H); 1.39 (d, 6H,
CH3); 1.01 (d, 3H, CH3). 13C-NMR (CD2Cl2, 300 MHz,
r.t., l ppm): 212.18; 151.63; 129.24; 127.28; 126.69;
60.63; 53.65; 40.26; 37.67; 36.06; 31.09; 27.07; 25.94;
23.44.
3.2.4. (+)-(2R, 5R)-2-[1-Methyl-1-(phenylthio)ethyl]-
5-methyl cyclohexanone oxime (7)
Into a 50 ml round-bottomed flask containing an
efficient stirring bar was added a solution of 5 (1.0 g,
3.81 mmol), hydroxylamine hydrochloride (1.34 g, 19.1
mmol), 4-dimethylaminopyridine (0.51 g, 4.19 mmol)
and MeOH (13 ml). The reaction mixture was stirred
for 24 h at r.t.. The mixture was diluted with water (70
ml) and extracted with diethyl ether (4×40 ml). The
combined organic layers were washed with 1.0 M HCl
(2×30 ml) and brine (50 ml). The organic solution was
dried over Na2SO4 and the solvent removed to give a
yellow solid (1.07 g) purified by recrystallization from
cyclohexane to yield a white solid (1.03 g, 97%). Anal.
Calc. for C16H23NOS (277.43): C, 69.27; H, 8.36; N,
5.05. Found: C, 69.43; H, 8.45; N, 4.99%. M.p. 85–
86°C. [h]2D0+35.5 (c 1, CHCl3). IR (KBr, w cm–1): 3393
1
958 s, 833 m, 750 s, 705 s, 692 s, 536 m. H-NMR
1
(CDCl3, 300 MHz, r.t., l ppm): H-NMR (CDCl3, 300
MHz, r.t., l ppm): 7.52–7.29 (m, 5H, Ph); 4.36 (s, 1H,
OH); 2.27–2.25 (m, 1H); 1.95–1.55 (m, 8H); 1.57 (s,
3H, CH3); 1.27 (s, 3H, CH3); 1.20 (d, 3H, CH3).
13C-NMR (CDCl3, 300 MHz, r.t., l ppm): 137.08;
131.34; 127.84; 127.76; 124.06; 68.33; 50.01; 39.06;
31.89; 27.63; 26.63; 25.94; 20.31; 17.95.
A second fraction was identified as pure 8 (11.1 g,
64.9%). Anal. Calc. for C16H24OS (264.43): C, 72.68; H,
9.15. Found: C, 72.47; H, 9.02%. [h]2D0 −5.0 (c 1,
CHCl3). IR (KBr, w cm–1): 3448 vs, 3059 m, 2947 vs,
2922 vs, 2868 s, 2845 m, 1651 vs, 1456 s, 1363 s, 1253
s, 1190 m, 1126 s, 1026 s, 950 s, 841 m, 750 s, 694 s.

I.S. Gonc¸al6es et al. / Journal of Organometallic Chemistry 626 (2001) 1–10
9
1H-NMR (CDCl3, 300 MHz, r.t., l ppm): 7.52–7.32
3.3.5. MoO2(THF)Cl{(−)-(1S,2R,5R)-2-[1-methyl-1-
(phenylthio)ethyl]-5-methylcyclohexanolato} (8a)
(m, 5H, Ph); 4.37 (s, 1H, OH); 2.38–2.37 (m, 1H);
1.90–1.69 (m, 6H); 1.43 (s, 3H, CH3); 1.26 (s, 3H,
CH3); 1.09–0.89 (m, 2H); 0.88 (d, 3H, CH3). 13C-NMR
(CD2Cl2, 300 MHz, r.t., l ppm): 137.86; 132.08; 128.94;
128.64; 124.06; 68.18; 50.39; 43.43; 35.57; 28.65; 27.36;
26.19; 22.11; 21.08.
Yield, 88%. Anal. Calc. for C20H31MoClO3S
(498.92): C, 48.15; H, 6.26. Found: C, 47.88; H, 5.98%.
IR (Nujol, w cm–1): 962 vs (MoꢀO), 922 vs (MoꢀO).
1H-NMR (CD2Cl2, 300 MHz, r.t., l ppm): 7.51–7.31
(m, 5H, Ph); 4.14 (THF); 2.07 (THF); 2.07–1.71 (m,
6H); 1.34 (s, 3H, CH3); 1.25 (s, 3H, CH3); 1.04–0.93
(m, 2H); 0.86 (d, 3H, CH3).
3.3. Synthesis of chiral dioxomolybdenum(VI)
complexes
3.3.6. MoO2(THF)Cl{(−)-(1R,2S,5R)-2-[1-methyl-1-
(phenylthio)ethyl]-5-methylcyclohexanolato} (9a)
Yield, 74%. Anal. Calc. for C20H31MoClO3S
(498.92): C, 48.15; H, 6.26. Found: C, 47.88; H, 5.98%.
IR (Nujol, w cm–1): 960 vs (MoꢀO), 920 vs (MoꢀO).
3.3.1. General procedure
A solution of MoO2Cl2(THF)2 (1.36 g, 4.00 mmol) in
CH2Cl2 (15 ml) was treated with one equivalent of
ligand. The resulting turbid solution was stirred for a
further 2 h. The solvent was evaporated, and the
product washed with hexane and dried under vacuum.
3.4. Synthesis of deri6atised mesoporous materials
3.3.2. MoO2(THF)2{(+)-cis-p-menthane-3,8-olato}
(1a)
3.4.1. Preparation of MCM-41-
Si(OEt)nCH2CH2CH2CN (10)
Yield, 82%. Anal. Calc. for C18H32MoO6 (440.39): C,
49.09; H, 7.32. Found: C, 48.78; H, 6.80%. IR (Nujol,
w cm–1): 1653 s, 1540 m, 1456 s, 1376 m, 1310 m, 1256,
1217 m, 1152 s, 1024 m, 997 m, 957 vs w(MoꢀO), 920 vs
w(MoꢀO), 891 m, 866 m, 721 s, 580 m. 1H-NMR
(CD2Cl2, 300 MHz, r.t., l ppm): 3.90 (THF); 1.96
(THF); 1.96–1.69 (m, 6H); 1.36 (s, 3H); 1.29 (d, 3H,
CH3); 1.00–0.96 (m, 1H); 0.92 (d, 3H, CH3).
Calcined MCM-41 (1.0 g) was activated at 180°C
under vacuum (10−2 mbar) for 2 h and treated with
excess of a solution of NCCH2CH2CH2Si(OEt)3 in
toluene (30 ml). The mixture was stirred under reflux
for 48 h. The solution was filtered off and the white
solid washed four times with 20 ml portions of diethyl
ether, before drying under vacuum at 100°C for several
hours. Anal. Found: C, 12.46; H, 2.37; N, 2.11%. IR
(KBr, w cm−1): 2980 m, 2940 m, 2898 m, 2257 m
w(CꢁN). 29Si MAS-NMR spectrum exhibited broad res-
onances at l= −109.6, −61.9 and −54.3. 29Si CP
MAS-NMR spectrum exhibited two broad resonances
at l= −109.5 (Q4) and l= −100.8 (Q3), a faint peak
at l= −91.9 (Q2), and two broad overlapping signals
at l= −59.9 and −53.6. 13C CP MAS-NMR (r.t., l
ppm): 118.3 (CꢁN); 58.3 (O–CH2–); 19.1 (–CH3); 16.6
(NC–CH2–); 10.5 (broad signal).
3.3.3. MoO2Cl2{(+)-(2S,5S)-2-(1-olato-1-
methylethyl)-5-methylcyclohexanone oxime} (3a)
Yield, 92%. Anal. Calc. for C10H19MoCl2O4N
(384.11): C, 31.27; H, 4.99; N, 3.65. Found: C, 31.70;
H, 5.02; N, 3.34%. IR (KBr, w cm–1): 3421 vs (OH),
3151 m, 3103 m, 2964 s, 2870 m, 1651 s, 1475 s, 1394
m, 1334 m, 1168 s, 1143 s, 1124 s, 1091 s, 1052 m, 943
vs (MoꢀO), 918 vs (MoꢀO), 833 s, 802 m, 763 m, 663 s,
1
553 s. H-NMR (CD2Cl2, 300 MHz, r.t., l ppm): 4.05
(br, 1H); 3.61 (br, 1H); 3.29–3.22 (m, 2H); 3.09–3.05
(br, 2H); 2.89–2.87 (m, 1H); 2.77–2.62 (m, 2H); 1.95–
1.89 (m, 1H); 1.45 (s, 3H, CH3); 1.37 (s, 3H, CH3); 1.06
(s, 3H, CH3).
3.4.2. Reaction of MCM-41-Si(OEt)nCH2CH2CH2-
CN with MoO2(THF)Cl{(−)-(1R,2S,5R)-2-[1-methyl-
1-(phenylthio)ethyl]-5-methylcyclohexanolato} (11)
A suspension of MCM-41-Si(OEt)nCH2CH2CH2CN
(0.8 g) was treated with excess of a solution of
MoO2(THF)Cl{(−)-(1S,2R,5R)-2-[1-methyl-1-(phenyl-
thio)ethyl]-5-methylcyclohexanol} (8a) (0.4 g) in
CH2Cl2 (30 ml). The mixture was stirred at r.t. for 24 h.
The solution was filtered off and the pale blue solid
washed four times with 30 ml portions of CH2Cl2 (20
ml), before drying under vacuum at r.t. for several
hours. Anal. Found: C, 10.49; H, 3.09; Cl, 0.76; Mo,
0.5; N, 1.92%. IR (KBr, w cm–1): 2982 m, 2937 m, 2896
m, 2254 m w(CꢁN). 29Si MAS-NMR spectrum exhibited
broad resonances at l= −108.9, −60.8 and −51.4.
29Si CP MAS-NMR spectrum exhibited two broad
resonances at l= −109.3 (Q4) and l= −101.5 (Q3),
a faint peak at l= −91.9 (Q2), and two broad over-
3.3.4 MoO2Cl2{(+)-(2R,5R)-2-[1-methyl-1-
(phenylthio)ethyl]-5-methylcyclohexanone oxime} (7a)
Yield, 96%. Anal. Calc. for C16H23MoCl2O3NS
(476.27): C, 40.35; H, 4.87; N, 2.94. Found: C, 40.63;
H, 4.75; N, 3.06%. IR (KBr, w cm–1): 3395 vs (OH),
3140 m, 3087 m, 2959 s, 2928 s, 2870 m, 1587 s, 1447
vs, 1395 m, 1375 m, 1138 s, 1084 s, 949 vs (MoꢀO), 916
1
vs (MoꢀO), 752 s, 691 s, 559 m. H-NMR (CD2Cl2, 300
MHz, r.t., l ppm): 7.81–7.35 (m, 5H, Ph); 3.94 (br,
1H); 3.49 (d, 1H); 3.32 (d, 1H); 2.74–2.47 (m, 2H);
2.17–2.12 (m, 1H); 2.06–1.51 (m, 2H); 1.38 (s, 3H,
CH3); 1.35–1.31 (m, 1H); 1.25 (s, 3H, CH3); 1.17 (d,
3H, CH3).

10
I.S. Gonc¸al6es et al. / Journal of Organometallic Chemistry 626 (2001) 1–10
lapping signals at l= −60.3 and −51.4. 13C CP
MAS-NMR (r.t., l ppm): 119.4 (CꢁN); 58.6 (O–CH2–);
19.0 (–CH3); 16.2 (NC–CH2–); 10.8 (broad signal).
Haider, PhD thesis, Technischen Universita¨t Mu¨nchen, 1999. (d)
A.K. Duhme-Klair, G. Vollmer, C. Mars, R. Fro¨hlich, Angew.
Chem. Int. Ed. Engl. 39 (2000) 1626.
[2] W.A. Herrmann, J.J. Haider, J. Fridgen, G.M. Lobmaier, M.
Spiegler, J. Organomet. Chem. 603 (2000) 69.
[3] S. Bellemin-Laponnaz, K.S. Coleman, J.A. Osborn, Polyhedron
18 (1999) 2533.
[4] R.J. Cross, P.D. Newman, R.D. Peacock, D. Stirling, J. Mol.
Catal. A: Chem. 144 (1999) 273.
3.5. Dioxomolybdenum(VI) complexes in epoxidation
catalysis
3.5.1. Chiral dioxomolybdenum(VI) complexes in
solution
[5] (a) F.E. Ku¨hn, E. Herdtweck, J.J. Haider, W.A. Herrmann, I.S.
Gonc¸alves, A.D. Lopes, C.C. Roma˜o, J. Organomet. Chem. 583
(1999) 3. (b) F.E. Ku¨hn, A.D. Lopes, A.M. Santos, E.
Herdtweck, J.J. Haider, C.C. Roma˜o, A.G. Santos, J. Mol.
Catal. A: Chem. 151 (2000) 147. (c) A.D. Lopes, PhD thesis,
ITQB/Universidade Nova de Lisboa, 1999. (d) F.E. Ku¨hn, A.M.
Santos, A.D. Lopes, I.S. Gonc¸alves, E. Herdtweck, C.C. Roma˜o,
J. Mol. Cat. A: Chem. 164 (2000) 25. (e) F.E. Ku¨hn, A.M.
Santos, I.S. Gonc¸alves, C.C. Roma˜o, A.D. Lopes, Appl.
Organometal. Chem. 15 (2000) 43.
A total of 200 mg cis-i-methylstyrene (1.7 mmol),
100 mg mesitylene (internal standard) and 1.0 mol% 1a,
3a, 7a–9a as catalyst (17 mmol) were dissolved in 2 ml
of dry toluene. After addition of 615 ml tert-butylhy-
droperoxide solution (5.5 M in decane) the reaction
mixture was stirred for up to 24 h at 55°C.
[6] F.E. Ku¨hn, A.M. Santos, A.D. Lopes, I.S. Gonc¸alves, J.E.
Rodr´ıguez-Borges, M. Pillinger, C.C. Roma˜o, J. Organomet.
Chem. (2000) in press.
[7] J.M. Thomas, T. Maschmeyer, B.F.G. Johnson, D.S. Shephard,
J. Mol. Catal. A: Chem. 141 (1999) 139.
[8] A. Corma, A. Fuerte, M. Iglesias, F. Sa´nchez, J. Mol. Catal. A:
Chem. 107 (1996) 225.
[9] P. Ferreira, I.S. Gonc¸alves, F.E. Ku¨hn, A.D. Lopes, M.A.
Martins, M. Pillinger, A. Pina, J. Rocha, C.C. Roma˜o, A.M.
Santos, T.M. Santos, A.A. Valente, Eur. J. Inorg. Chem. (2000)
2263.
[10] (a) H.E. Ensley, C.A. Parnell, E.J. Corey, J. Org. Chem. 43
(1978) 1610. (b) R. Ratcliffe, R. Rodehorst, J. Org. Chem. 35
(1970) 4000.
[11] R.V. Stevens, F.C.A. Gaeta, D.S. Lawrence, J. Am. Chem. Soc.
105 (1983) 7713.
3.5.2. MCM-41-supported dioxomolybdenum(VI)
catalyst
A total of 800 mg (7.3 mmol) cis-cyclooctene, 800 mg
n-dibutylether (internal standard), 175 mg 11 as cata-
lyst and 2 ml 5.5 M TBHP were added to a ther-
mostated reaction vessel and stirred for 24 h at 50°C.
The course of the reactions were monitored by quan-
titative GC-analysis. Samples were taken every thirty
minutes, diluted with chloroform, and chilled in an
icebath. For the destruction of hydroperoxide and re-
moval of water a catalytic amount of manganese diox-
ide and manganese sulfate was added. After the gas
evolution ceased the resulting slurry was filtered over a
filter equipped Pasteur pipette and the filtrate injected
into the GC column. The enantiomeric excesses and
conversions were determined by chiral GC methods on
a Hewlett–Packard (HP5970 B) instrument equipped
with a Chiraldex g-TA column (Alltech), a mass-selec-
tive detecter (HP5970 B) and integration unit (HP
3394).
[12] E.L. Eliel, J.E. Lynch, F. Kume, S.V. Frye, Org. Synth. 65
(1987) 215.
[13] (a) R.L. Halterman, K.P.C. Vollhardt, Organometallics 7 (1988)
883. (b) O. Ort, Org. Synth. 8 (1993) 522. (c) D. Potin, F.
Dumas, J. Maddaluno, Synth. Commun. 20 (1990) 2805. (d) T.
Takahashi, N. Kurose, T. Koizumi, M. Shiro, Heterocycles 36
(1993) 1601.
[14] W.P. Griffith, J. Chem. Soc. (A) (1969) 211.
[15] R. Schmidt, M. Sto¨cker, E. Hansen, D. Akporiaye, O.H.
Ellestad, Microporous Mater. 3 (1995) 443.
[16] (a) T.-S. Lai, H.-L. Kwong, R. Zhang, C.-M. Che, J. Chem. Soc.
Dalton Trans. (1998) 3559. (b) R. Zhang, W.-Y. Yu, T.-S. Lai,
C.-M. Che, Chem. Commun. (1999) 409. (c) T.-S. Lai, R. Zhang,
K.-K. Cheung, H.-L. Kwong, C.-M. Che, Chem. Commun.
(1998) 1583.
[17] R.A. Sheldon, J.A. Van Doorn, J. Catal. 31 (1973) 427.
[18] R.D. Oldroyd, J.M. Thomas, T. Maschmeyer, P.A. MacFaul,
D.W. Snelgrove, K.U. Ingold, D.D.M. Wayner, Angew. Chem.
Int. Ed. Engl. 35 (1996) 2787.
[19] (a) C.T. Kresge, M.E. Leonowicz, W.J. Roth, J.C. Vartuli, J.S.
Beck, Nature 359 (1992) 710. (b) J.S. Beck, J.C. Vartuli, W.J.
Roth, M.E. Leonowicz, C.T. Kresge, K.D. Schmitt, C.T.-W.
Chu, D.H. Olson, E.W. Sheppard, S.B. McCullen, J.B. Higgins,
J.L. Schlenker, J. Am. Chem. Soc. 114 (1992) 10834.
[20] R. Colton, I.B. Tomkins, Aust. J. Chem. 18 (1965) 447.
[21] W.M. Carmichael, D.A. Edwards, G.W.A. Fowles, P.R. Mar-
shall, Inorg. Chim. Acta 1 (1967) 93.
Acknowledgements
This work was supported by PRAXIS XXI, Project
2/2.1/QUI/419/94. The authors are grateful to DAAD
and CRUP (INIDA and Acc¸o˜es Integradas Pro-
gramme), and to Profesor W.A. Herrmann for generous
support. ADL and JEB thank PRAXIS XXI, and AMS
acknowledges Bayerische Forschungsstiftung for
fellowship.
a
References
[1] (a) I. Ojima (Ed.), Catalytic Asymmetric Syntheses, VCH, Wein-
heim, 1993. (b) C. Bolm, Chem. Eur. J. 6 (2000) 2309. (c) J.J.
[22] F.J. Arna´ız, R. Aguado, J.M.M. de Ilarduya, Polyhedron 13
(1994) 3257.