An easily accessed molybdenum Lewis acid as a catalyst for imine aziridination

Article abstract of DOI:10.1021/om010958i

The complex [MoCl(n³-C₃H₅)(CO)₂(phen)] was prepared in a one-pot manner from Mo-(CO)₆, allyl chloride, and 1,10-phenanthroline (phen). This complex reacted with AgOTf to afford [Mo(OTf)(n³-C₃H₅)(CO)₂(phen)] (1). The reaction of 1 with NaBAr′₄ (Ar′ = 3,5-bis-(trifluoromethyl)phenyl) in CH₂Cl₂ yielded a solution that catalyzed (1% load of the catalyst) the reaction of ethyl diazoacetate with N-benzylideneaniline to give a mixture of cis-(carboxyethyl)-1,3-diphenylaziridine and two enamines. Replacemenst of phen by chiral ligands based on trans-1,2-diaminocyclohexane failed to induce asymmetry on the obtained aziridine.

Full text of DOI:10.1021/om010958i

1540
Organometallics 2002, 21, 1540-1545
Articles
An Ea sily Accessed Molybd en u m Lew is Acid a s a
Ca ta lyst for Im in e Azir id in a tion
Dolores Morales,† J ulio Pe´rez,*,† Luc´ıa Riera,† V´ıctor Riera,† Rau´l Corzo-Sua´rez,‡
Santiago Garc´ıa-Granda,‡ and Daniel Miguel§
Departamento de Quı´mica Orga´nica e Inorga´nica/ IUQOEM and Departamento de Quı´mica
Fı´sica y Anal´ıtica, Facultad de Quı´mica, Universidad de Oviedo-CSIC, 33071 Oviedo, Spain,
and Departamento de Qu´ımica Inorga´nica, Facultad de Ciencias, Universidad de Valladolid,
47071 Valladolid, Spain
Received November 6, 2001
The complex [MoCl(η3-C3H5)(CO)2(phen)] was prepared in a one-pot manner from Mo-
(CO)6, allyl chloride, and 1,10-phenanthroline (phen). This complex reacted with AgOTf to
afford [Mo(OTf)(η3-C3H5)(CO)2(phen)] (1). The reaction of 1 with NaBAr′4 (Ar′ ) 3,5-bis-
(trifluoromethyl)phenyl) in CH2Cl2 yielded a solution that catalyzed (1% load of the catalyst)
the reaction of ethyl diazoacetate with N-benzylideneaniline to give a mixture of cis-
(carboxyethyl)-1,3-diphenylaziridine and two enamines. Replacement of phen by chiral
ligands based on trans-1,2-diaminocyclohexane failed to induce asymmetry on the obtained
aziridine.
In tr od u ction
Pseudooctahedral [MoX(η3-allyl)(CO)2(N-N)] (X )
halide, N-N ) 2,2′-bipyridine, 1,10-phenanthroline)5
are inexpensive compounds that can be easily prepared,
can be handled in the air for short periods of time, and
are compatible with the presence of water in their
solutions.6
Curtis found that the cationic 16-electron fragment
{Mo(η3-allyl)(CO)2(N-N)}+ (N-N ) bipy) acts as a
strong Lewis acid.7 We felt that if a straightforward and
clean method were available for the generation of
fragments of this kind or the related [Mo(S)(η3-allyl)-
(CO)2(N-N)]+ solvates, these species could be attractive
Lewis acidic reagents. Here we report our results on the
generation of these molybdenum cationic compounds
and their application to the catalytic synthesis of
aziridines from N-benzylideneaniline (BDA) and ethyl
diazoacetate (EDA).8
Organic molecules with heteroatoms bearing lone
electron pairs can be activated toward different stoi-
chiometric or catalytic processes by coordination to
Lewis acids.1 Main-group Lewis acids are the most
widely used, although transition-metal or lanthanide
chlorides or triflates have been increasingly applied.2
More sophisticated transition-metal complexes3 offer
little or no compensation in exchange for their multistep
preparation and higher cost. Lewis acidic reagents based
on group 6 metal carbonyl complexes, which are the
most pertinent to the work described here, include
[W(SbF6)(CO)3(NO)(PMe3)]3a,4b and aldehyde adducts of
{MCp(CO)3}+ 3a or {MTp(CO)(RCtCMe)}+ 4c,d frag-
ments (M ) Mo, W).4
* To whom correspondence should be addressed. E-mail: japm@
sauron.quimica.uniovi.es.
† Departamento de Qu´ımica Orga´nica e Inorga´nica/IUQOEM, Uni-
versidad de Oviedo-CSIC.
Resu lts a n d Discu ssion
‡ Departamento de Qu´ımica F´ısica y Anal´ıtica, Universidad de
Oviedo-CSIC.
Cationic [Mo(S)(η3-allyl)(CO)2(N-N)]+ complexes have
been generated by treatment of the halo precursors
[MoX(η3-allyl)(CO)2(N-N)] with silver tetrafluorobo-
rate.9 The resulting solutions may be poorly defined
regarding their use in catalysis, since traces of silver
§ Universidad de Valladolid.
(1) (a) Narasaka, K. Synthesis 1991, 1, 1. (b) Kagan, H. B.; Riant,
O. Chem. Rev. 1992, 92, 1007. (c) Lewis Acid Reagents; Yamamoto,
H., Ed.; Oxford University Press: Oxford, U.K., 1999. (d) Fukuzumi,
S.; Satoh, N.; Okamoto, T.; Yaswi, K.; Suenobu, T.; Seko, Y.; Fujitsuka,
M.; Ito, O. J . Am. Chem. Soc. 2001, 123, 7756. (e) Asao, N.; Asano, T.;
Yamamoto, Y. Angew. Chem., Int. Ed. 2001, 40, 3206. (f) Yang, D.;
Gu, S.; Yan, Y.; Zhu, N.; Cheung, K. J . Am. Chem. Soc. 2001, 123,
8612.
(2) (a) Xie, W.; J in, Y.; Wang, P. G. Chemtech 1999, 29, 23. (b)
Kobayashi, S.; Busujima, T.; Nagayama, S. Chem. Eur. J . 2000, 6,
3491.
(3) (a) Bonnesen, P. V.; Puckett, C. L.; Honeychuck, R. V.; Hersh,
W. H. J . Am. Chem. Soc. 1989, 111, 6070. (b) Ku¨ndig, E. P.; Bourdin,
B.; Bernardinelli, G. Angew. Chem., Int. Ed. Engl. 1994, 33, 1856. (c)
Ellis, W. W.; Gavrilova, A.; Liable-Sands, L.; Rheingold, A. L.; Bosnich,
B. Organometallics 1999, 18, 332. (d) Faller, J . W.; Parr, J . Organo-
metallics 2000, 19, 1829.
(4) (a) Hersh, W. H. J . Am. Chem. Soc. 1985, 107, 4599. (b)
Honeychuck, R. V.; Bonnesen, P. V.; Farahi, J .; Hersh, W. H. J . Org.
Chem. 1987, 52, 5293. (c) Caldarelli, J . L.; Wagner, L. E.; White, P.
S.; Templeton, J . L. J . Am. Chem. Soc. 1994, 116, 2878. (d) Gunnoe,
T. B.; Caldarelli, J . L.; White, P. S.; Templeton, J . L. Angew. Chem.,
Int. Ed. 1998, 37, 2093.
(5) tom Dieck, H.; Friedel, H. J . Organomet. Chem. 1968, 14, 375.
(6) Brisdon, B. J .; Cartwright, M.; Hodson, A. G. J . Organomet.
Chem. 1984, 277, 85.
(7) Curtis, M. D.; Fotinos, N. A. J . Organomet. Chem. 1984, 172,
43.
10.1021/om010958i CCC: $22.00 © 2002 American Chemical Society
Publication on Web 03/14/2002

Mo Lewis Acid as a Aziridination Catalyst
Organometallics, Vol. 21, No. 8, 2002 1541
salts may act as Lewis acids as well,3a and the isolation
of the cationic labile complexes in a pure state proved
difficult. In addition, the tetrafluoroborate anion is
known to participate in hydrolyses and fluoride transfer
pathways, which can result in catalyst deactivation.10
The complex [Mo(OTf)(η3-C3H5)(CO)2(phen)] (1) is
synthesized by the reaction of silver triflate with [MoCl-
(η3-C3H5)(CO)2(phen)], which in turn can be prepared
in a one-pot manner from Mo(CO)6, allyl chloride, and
1,10-phenanthroline (see Experimental Section). The
neutral complex 1 could be purified by crystallization
to remove traces of silver salts. We found that 1 does
not catalyze the reaction of BDA and EDA, a fact that
we attribute to insufficient lability of the triflate group
in 1.
The reaction of the salt NaBAr′4 (Ar′ ) 3,5-bis-
(trifluoromethyl)phenyl)11 with covalent triflato com-
plexes in CH2Cl2 solution was used by Bergman12 and
Caulton13 for the generation of cationic dichloromethane
complexes. Addition of NaBAr′4 to a CH2Cl2 solution of
1 caused it to become cloudy, due to the formation of
insoluble sodium triflate. The νCO bands of the resulting
solution were shifted to higher wavenumbers, as ex-
pected for the formation of a cationic species (νCO 1963,
1875 cm-1 vs 1948, 1864 cm-1 for 1). This solution was
found to catalyze the reaction of BDA and EDA in CH2-
Cl2 at 20 °C. Thus, in the presence of 1% of the catalyst,
EDA reacted with BDA in 8 h to afford a mixture of
cis-(carboxyethyl)-1,3-diphenylaziridine (A) and enam-
ines B and C (aziridine:enamine ) 1:1) (see Scheme 1
In the absence of BDA, the solution obtained by
mixing 1 and NaBAr′4 in CH2Cl2 did not catalyze the
decomposition of EDA. Accordingly, diethyl fumarate
and diethyl maleate were absent in the aziridine-
enamine mixture obtained in the catalytic reaction.
Therefore, a mechanism involving carbene intermedi-
ates can be, in principle, excluded.14
All our attempts to isolate the product of the reaction
between 1 and NaBAr′4 failed, and only broad nonin-
formative bands could be observed in the 1H NMR
spectrum. We attribute this to the extremely labile
nature of the resulting species. Furthermore, more than
one cationic complex could be present, CH2Cl2 and water
being obvious possible ligands in Mo solvates.
Addition of BDA to the CH2Cl2 solutions resulting
from the mixture of 1 and NaBAr′4 did not make
possible the isolation of any pure compound either.
On the other hand, when benzophenone imine was
added instead, the imine complex [Mo(HNdCPh2)(η3-
C3H5)(CO)2(phen)]BAr′4 (2) could be isolated and char-
acterized by microanalysis and IR and NMR (1H and
13C) spectroscopy (see Scheme 2 and Experimental
Section).
Sch em e 2
Sch em e 1
This confirms that one or more labile complexes [Mo-
(S)(η3-C3H5)(CO)2(phen)]BAr′4 are present in the cata-
lytically active solutions obtained from the reaction of
the triflato complex 1 and NaBAr′4 in CH2Cl2.
The fact that benzophenone imine, but not BDA,
allowed the isolation of an imine complex is not surpris-
ing in view of the previously known chemistry of
transition-metal complexes with monodentate imine
ligands. Thus, whereas adducts of N-H imines can be
obtained with relative ease,15 coordination of N-CH3
imines required more forcing conditions15a and, to our
knowledge, no N-bound transition-metal BDA complex
has been reported, reflecting the importance of the steric
hindrance caused by the substituent on the nitrogen
atom.16 It was suggested above that [Mo(OH2)(η3-C3H5)-
(CO)2(phen)]+ could be present in the catalytic solution.
Such a cationic aquo complex can show a significant
Brønsted acidity. To suppress its possible effect on the
catalysis, 2,6-di-tert-butylpyridine was added to the
precatalyst (see Experimental Section). This hindered,
noncoordinating base has been used by several groups
and Experimental Section). The formation of enamines
as byproducts in Lewis acid catalyzed syntheses of
aziridines has been previously noted and has been
explained by a 1,2-shift of either a hydrogen or an alkyl
group.8b
(8) For previously reported Lewis acid catalyzed reactions of imines
and diazoesters see ref 2a and: (a) Zhu, Z.; Espenson, J . H. J .
Organomet. Chem. 1995, 60, 7090. (b) Casarrubios, L.; Pe´rez, J . A.;
Brookhart, M.; Templeton, J . L. J . Org. Chem. 1996, 61, 8358. (c)
Rasmussen, K. G.; J ørgensen, K. A. J . Chem. Soc., Perkin Trans. 1
1997, 1287. (d) Antilla, J . C.; Wulff, W. D. J . Am. Chem. Soc. 1999,
121, 5099.
(9) Powell, P. J . J . Organomet. Chem. 1997, 129, 175.
(10) (a) Strauss, S. H. Chem. Rev. 1993, 93, 927. (b) Su¨nkel, K.;
Urban, G.; Beck, W. J . Organomet. Chem. 1983, 252, 187.
(11) Brookhart, M.; Grant, B.; Volpe, A. F. Organometallics 1992,
11, 3920.
(14) (a) Hansen, K. B.; Finney, N. S.; J acobsen, E. N. Angew. Chem.,
Int. Ed. Engl. 1995, 34, 676. (b) Rasmussen, K. G.; J ørgensen, K. A.
J . Chem. Soc., Chem. Commun. 1995, 1401.
(15) (a) Knight, D. A.; Dewey, M. A.; Stark, G. A.; Bennett, B. K.;
Arif, A. M.; Gladysz, J . A. Organometallics 1993, 12, 4523. (b)
Ferna´ndez, J . M.; Gladysz, J . A. Organometallics 1989, 8, 207. (c)
Faller, J . W.; Ma, Y.; Smart, C. J .; DiVerdi, M. J . J . Organomet. Chem.
1991, 420, 237. (d) Gunnoe, T. B.; White, P. S.; Templeton, J . L. J .
Am. Chem. Soc. 1996, 118, 6916.
(12) Arndtsen, B. A.; Bergman, R. G. Science 1995, 270, 1970.
(13) Huang, D.; Huffman, J . C.; Bollinger, J . C.; Eisenstein, O.;
Caulton, K. G. J . Am. Chem. Soc. 1997, 119, 7398.
(16) A tin complex of an N-phenylimine was reported, which was
reacted with EDA to yield aziridines: Ramussen, K. G.; Hazell, R. G.;
J ørgensen, K. A. Chem. Commun. 1997, 1103.

1542 Organometallics, Vol. 21, No. 8, 2002
Ta ble 1. Cr ysta l Da ta a n d Refin em en t Deta ils for Com p lexes 3-5
Morales et al.
3
4
5
formula
fw
C
28H30Cl2Mo2N4O6
C26H20Mo2N4O8‚CH2Cl2
793.27
C28H30Cl2Mo2N4O4‚CH2Cl2
834.27
781.34
cryst syst
space group
a, Å
b, Å
c, Å
monoclinic
P21/c
15.978(11)
15.24(3)
13.721(6)
90
113.04(4)
90
3074(6)
4
monoclinic
P2/c
15.7554(14)
8.8730(8)
23.293(2)
90
103.182
90
3170.4(5)
4
triclinic
P1h
11.1246(19)
12.823(2)
12.928(2)
82.526(3)
69.071(3)
83.352(3)
1703.1(5)
2
R, deg
â, deg
γ, deg
V, Å3
Z
T, K
200(2)
1.688
1568
293(2)
1.662
1576
299(2)
1.627
836
Dc, g cm-3
F(000)
λ(Mo KR), Å
cryst size, mm
µ, mm-1
scan range, deg
abs cor
no of rflns measd
no of indep rflns
no. of data/restraints/params
goodness of fit on F2
R1/wR2 (I > 2σ(I))
R1/wR2 (all data)
0.710 73
0.13 × 0.13 × 0.10
1.037
1.38 e θ e 26.01
ψ scan
6303
6037
6037/0/379
0.962
0.0438/0.0965
0.1396/0.1230
0.710 73
0.08 × 0.22 × 0.35
1.012
1.33 e θ e 23.27
SADABS
13 874
4557
4557/3/394
1.037
0.710 73
0.10 × 0.15 × 0.20
1.089
1.61 e θ e 23.26
SADABS
7760
4865
4865/0/388
1.0037
0.0475/0.1376
0.0522/0.1428
0.0396/0.1089
0.0470/0.1150
Ch a r t 1. Liga n d s LN2O2 a n d LN4
as a proton scavenger in Lewis acid catalyzed reactions.3a
Its addition did not have an appreciable effect on the
Mo-catalyzed aziridination. Hence, we assume that a
Lewis acid, but not a Brønsted acid, is the catalytically
active species.
We wanted to explore the possibility of enantioselec-
tive catalytic aziridine synthesis17 using cationic com-
plexes of the type described above.
The chiral ligand trans-1,2-bis(2-pyridinecarboxam-
ide)cyclohexane (LN2O2; Chart 1) has been recently
employed by Trost in combination with the labile
complex [Mo(CO)3(NCMe)3] for asymmetric molybdenum-
catalyzed allylic alkylation.18
F igu r e 1. Molecular structure and numbering scheme of
3 with hydrogen atoms omitted for clarity. Thermal el-
lipsoids are drawn at the 30% probability level. Selected
bond lengths (Å): Mo(1)-C(30) ) 2.346(7), Mo(1)-C(31)
) 2.203(7), Mo(1)-C(35) ) 2.285(8), Mo(1)-C(24) ) 1.933-
(7), Mo(1)-C(41) ) 1.931(7), Mo(1)-Cl(2) ) 2.570(2), Mo-
(1)-N(14) ) 2.226(6), Mo(1)-O(8) ) 2.209(4).
We thought that knowing the structure of the catalyst
would help to rationalize this lack of asymmetric induc-
tion. However, repeated attempts to obtain X-ray-
quality crystals of a cationic complex from the catalyti-
cally active solutions were unsuccessful. We then turned
our attention to the neutral precatalyst resulting from
Equimolar mixtures of [MoCl(η3-C3H5)(CO)2(NCMe)2]
and LN2O2 in CH2Cl2 were treated sequentially with
silver triflate and, after filtration to remove AgCl, with
NaBAr′4 and 2,6-di-tert-butylpyridine. The resulting
solution was found to catalyze the reaction of BDA and
EDA to afford aziridine-enamine mixtures analogous
to those obtained with the achiral phen catalyst. The
shift reagent [Eu(hfc)3]19 was added to the CD2Cl2
solutions of the resulting aziridines to separate the
signals due to each enantiomer in the 1H NMR spec-
trum, which were then integrated. No observable enan-
tiomeric excess was found.
the reaction of [MoCl(η3-C3H5)(CO)2(NCMe)2] and LN2O2
.
Our attempts at crystallization using these equimolar
mixtures failed. We observed that the IR spectrum of
the solution in the 2200-1800 cm-1 region, consistent
with the occurrence of a single species 3, remained the
same when a LN2O2:Mo ) 1:2 ratio was employed (νCO
1936, 1845 cm-1). Red crystals of compound 3, with an
IR spectrum identical with that of the mother solution,
were obtained by slow diffusion of hexanes into a
solution of the 1:2 mixture in CH2Cl2. We therefore
concluded that 3 has a LN2O2:Mo ) 1:2 ratio and that
(17) Osborn, H. M. I.; Sweeney, J . Tetrahedron: Asymmetry 1997,
8, 1693.
(18) Trost, B. M.; Hachiya, I. J . Am. Chem. Soc. 1998, 120, 1104.
(19) hfc ) tris[3-(heptafluoropropylhydroxymethylene)-(+)-camphor-
ato], europium(III) derivative.

Mo Lewis Acid as a Aziridination Catalyst
Organometallics, Vol. 21, No. 8, 2002 1543
Sch em e 3
the difficulty experienced trying to grow crystals from
the 1:1 solution was due to the presence of a mixture of
3 and free LN2O2 in it.
The bis(bidentate) Schiff-base ligand trans-1,2-bis(2-
pyridylimine)cyclohexane (LN4; Chart 1), also based on
trans-1,2-diaminocyclohexane, has been recently used
by Puddephatt in the field of platinum chemistry.25 This
ligand features four potential donor nitrogens, two of
which are directly bonded to the stereogenic carbons.
The neutral compound [{MoCl(η3-C3H5)(CO)2}2(µ-
The structure of 3 was determined by X-ray diffrac-
tion (Figure 1 and Table 1). Its molecule consists of two
identical {MoCl(η3-C3H5)(CO)2} units bridged by one
LN2O2 ligand, which chelates the molybdenum atom
through the oxygen and the pyridine nitrogen. The
coordination geometry around each molybdenum can be
described as approximately octahedral, with the allyl
group and the two CO ligands defining one face of the
octahedron. This is common to most known [MoX(η3-
allyl)(CO)2(L-L)] compounds,20 as are the orientation
of the allyl ligand, with its open face pointing toward
the carbonyls,21 and the acute OC-Mo-CO angles.22
The Cl and oxygen donor atoms are trans to the CO
groups, and the pyridine nitrogen is trans to the allyl
ligand.
To our knowledge, the bimetallic complex 3 is the first
complex of the ligand LN2O2 to be structurally charac-
terized. The crystal structures of Cu(II) and Ni(II)
complexes of the doubly deprotonated form of LN2O2
have been reported,23 and in both complexes, the ligand
acts as a tetradentate species through the four nitrogens
toward a single metal. The structure found for 3 was
somewhat unexpected, since a carbonyl oxygen should
be a poor ligand for an organometallic fragment. A
structurally related bridge bis(chelate) involving coor-
dination of a carbonyl oxygen and a phosphine to each
metal has been recently reported.24 The structure of the
bis(pyridylamide) complex 3 shows that the molybde-
num atom is far from the stereogenic centers, and the
chiral ligand does not surround the metal, as was
suggested to occur in the Mo/LN2O2 catalyzed allylic
alkylation.18
L
N4)] (5) was prepared by two methods: (a) the reaction
of LN4 with [Mo(CO)6] to yield [{Mo(CO)4}2(µ-LN4)] (4),
followed by oxidative addition of allyl chloride, and (b)
the reaction of LN4 with [MoCl(η3-C3H5)(CO)2(NCMe)2]
(see Scheme 3).
The structures of the molybdenum(0) tetracarbonyl
complex 4 and the molybdenum(II) dicarbonyl complex
5 were determined by X-ray diffraction, and the results
are shown in Figure 2. In both complexes, LN4 bridges
two molybdenum atoms, chelating each one through one
imine and one pyridine. A pseudooctahedral geometry
was found for the molybdenum atoms of 5, with the two
carbonyls and the allyl group in a facial disposition.
Unlike the case in 3, now the CO ligands are trans to
the Cl and pyridine donors, whereas the allyl group is
trans to the imine.
The chloro complex 5 was treated with AgOTf, and
the resulting triflato complex was treated with NaBAr′4
and 2,6-di-tert-butylpyridine in CH2Cl2. The resulting
solution was found to catalyze the aziridination of BDA
and EDA. Dissappointingly, no asymmetric induction
was found in the products. A search of chiral ligands
able to catalyze the asymmetric synthesis of aziridines
employing cationic molybdenum complexes continues in
this laboratory, as well as an exploration of these
molybdenum compounds as catalysts for other reactions.
Exp er im en ta l Section
Gen er a l P r oced u r es. General conditions and the labeling
scheme for the BAr′4 anion were given elsewhere.26
(20) Baker, P. K. Adv. Organomet. Chem. 1995, 40, 45.
(21) Curtis, M. D.; Eisenstein, O. Organometallics 1984, 3, 887.
(22) Frohnapfel, D. S.; White, P. S.; Templeton, J . L.; Ru¨egger, H.;
Pregosin, P. S. Organometallics 1997, 16, 3737.
(23) Mulgi, M.; Stephens, F. S.; Vagg, R. S. Inorg. Chim. Acta 1981,
51, 9, 73.
Syn th esis of [Mo(OTf)(η3-C3H5)(CO)2(p h en )] (1). A mix-
ture of the chloro complex [MoCl(η3-C3H5)(CO)2(phen)] (0.10
(24) Butts, C. P.; Crosby, J .; Lloyd-J ones, G. C. Chem. Commun.
1999, 1707.
(25) Baar, C. R.; J ennings, M. C.; Puddephatt, R. J .; Muir, K. W.
Organometallics 1999, 18, 4373.

1544 Organometallics, Vol. 21, No. 8, 2002
Morales et al.
dissolved in CH2Cl2 and filtered (Celite). 1H NMR showed a
mixture of cis-carboxyethyl-1,3-diphenylaziridine (A; 55%, 1H
NMR integration) and enamines B and C (Scheme 1). cis-
(Carboxyethyl)-1,3-diphenylaziridine (A): 1H NMR (CDCl3; δ)
1.03 (t, 3H, J ) 7.05 Hz, CH3), 3.25 (d, 1H, J ) 6.8 Hz, CHPh),
3.63 (d, 1H, J ) 6.8 Hz, CHCO), 3.97-4.13 (m, 2H, CH2), 6.90-
7.58 (m, 10H, C6H5).
Syn th esis of [Mo(HNdCP h 2)(η3-C3H5)(CO)2(ph en )]BAr ′4
(2). To a solution of 1 (0.060 g, 0.11 mmol) in CH2Cl2 (20 mL)
was added NaBAr′4 (0.11 g, 0.11 mmol) and benzophenone
imine (19 µL, 0.11 mmol). The mixture was stirred for 1 h at
room temperature and filtered via cannula. The solution was
concentrated by in vacuo evaporation to a volume of 5 mL.
Addition of hexane (20 mL) caused the precipitation of 2 as a
red solid, which was washed with hexane (3 × 10 mL) and
dried under reduced pressure. Yield: 0.09 g, 78%. IR (CH2-
1
Cl2; cm-1): 1963, 1875 (νCO). H NMR (CD2Cl2; δ): 8.92, 8.53,
7.96, and 7.43 (m, 2H each, phen), 8.85 (s, br, 1H, imine N-H),
7.75 (m, 8H, H-Co), 7.55 (m, 4H, H-Cp), 7.09 (m, 6H, 2Ph),
6.18 (m, 4H, 2Ph), 3.50 (d (6.5), 2H, Hsyn), 2.96 (m, 1H, CH of
η3-C3H5), 1.77 (d (9.7), 2H, Hanti). 13C{1H} NMR (CD2Cl2; δ):
223.51 (CO), 186.70 (CdN), 162.13 (q (49.79), Ci), 152.89,
144.26, 139.52, 129.34, 129.03, and 128.32 (phen), 135.16 (Co),
128.16 (q (31.1), Cm), 124.94 (q (272.5), CF3), 117.87 (Cp), 74.26
(C2 of η3-C3H5), 60.37 (C1 and C3 of η3-C3H5). Anal. Calcd for
C
62H36BF24MoN3O2: C, 52.53; H, 2.56; N, 2.96. Found: C,
52.41; H, 2.48; N, 2.71.
Syn th esis of 3. To a solution of [MoCl(η3-C3H5)(CO)2-
(NCMe)2] (0.10 g, 0.32 mmol) in CH2Cl2 (30 mL) was added
the ligand LN2O2 (0.052 g, 0.16 mmol). The reaction mixture
was stirred for 15 min at room temperature. The solvent was
removed, and the residue was washed twice with hexane (20
mL). Recrystallization from CH2Cl2/hexanes yielded 0.12 g of
1 (95%) in two crops as red crystals. IR (CH2Cl2; cm-1): 1936,
1
1845 (νCO). H NMR (CD2Cl2; δ): δ 9.36 (s, br, 2H, Cy-NH),
F igu r e 2. (a) Molecular structure and numbering scheme
of 4 with hydrogen atoms omitted for clarity. Thermal
ellipsoids are drawn at the 30% probability level. Selected
bond lengths (Å): Mo(1)-C(1) ) 2.040(7), Mo(1)-C(2) )
1.964(7), Mo(1)-C(3) ) 1.947(7), Mo(1)-C(4) ) 2.034(6),
Mo(1)-N(1) ) 2.249(4), Mo(1)-N(2) ) 2.277(4). (b) Molec-
ular structure and numbering scheme of 5 with hydrogen
atoms omitted for clarity. Thermal ellipsoids are drawn at
the 30% probability level. Mo(1)-C(1) ) 1.973(7), Mo(1)-
C(2) ) 1.974(7), Mo(1)-C(3) ) 2.330(7), Mo(1)-C(4) )
2.192(6), Mo(1)-C(5) ) 2.308(6), Mo(1)-Cl ) 2.5511(14),
Mo(1)-N(1) ) 2.232(3), Mo(1)-N(3) ) 2.282(5).
9.08, 7.99, 7.83, 7.61 (m, 2H each, pyridine H), 3.84 (m, 4H,
Cy + allyl), 3.43 (s, br, 2H, allyl), 2.22 (m, 2H, allyl), 1.95 (m,
Cy + allyl), 1.43 (m, 6H, Cy + allyl). Anal. Calcd for C28H30
-
Cl2Mo2N4O6: C, 43.04; H, 3.87; N, 7.17. Found: C, 42.91; H,
4.02; N, 7.21.
Syn th esis of 4. A stirred suspension of [Mo(CO)6] (0.10 g,
0.38 mmol) and LN4 (0.055 g, 0.19 mmol) in THF (30 mL) was
heated to reflux under nitrogen for 8 h, giving a purple
solution. The solvent was evaporated to dryness. The residue
was extracted with CH2Cl2 and filtered through Celite. The
volatiles were removed in vacuo, and the residue was washed
with hexane (3 × 10 mL). Slow diffusion of hexane into a
solution of 4 in CH2Cl2 at room temperature produced red
crystals. A single crystal obtained in this way was used for
the X-ray analysis. Yield: 0.106 g, 79%. IR (CH2Cl2; cm-1):
2016, 1908, 1877, 1836 (νCO). 1H NMR (CD2Cl2; δ): 8.98 (m,
2H), 8.82 (s, 2H, NdCH), 7.83 (m, 2H), 7.75 (m, 2H), 7.38 (m,
2H), 4.48 (m, 2H, NCH), 2.00 (m, 6H), 1.93 (m, 2H). Anal. Calcd
for C26H20Cl2Mo2N4O8: C, 44.09; H, 2.85; N, 7.91. Found: C,
44.21; H, 2.77; N, 7.85.
Syn th esis of 5. (a ) F r om [MoCl(η3-C3H5)(CO)2(NCMe)2].
To a solution of [MoCl(η3-C3H5)(CO)2(NCMe)2] (0.10 g, 0.32
mmol) in CH2Cl2 (20 mL) was added the ligand LN4 (0.047 g,
0.16 mmol). Inmediately the initially yellow solution turned
red. The mixture was stirred for 30 min. Pure 5 was obtained
by slow diffusion of hexane into a solution of 5 in CH2Cl2 at
-20 °C. One of the resulting crystals was used for the X-ray
determination. Yield: 0.097 g, 81%. IR (CH2Cl2; cm-1): 1937,
1852 (νCO). 1H NMR (CD2Cl2; δ): 8.98 (m, 2H), 8.37 (s, 2H,
NdCH), 8.02 (m, 2H), 7.69 (m, 2H), 7.35 (m, 2H), 3.88 (m, 2H,
NCH), 3.16 (d (J ) 6.2 Hz), 2H, Hsyn), 2.27 (m, 6H), 1.57 (d (J
) 9.1), 2H, Hanti), 1.26 (m, 2H). Anal. Calcd for C28H30Cl2-
Mo2N4O4: C, 44.88; H, 4.03; N, 7.48. Found: C, 45.06; H, 4.17;
N, 7.29.
g, 0.24 mmol), AgOTf (0.063 g, 0.24 mmol), and acetone (1 mL)
was stirred in the dark for 2 h. The solvent was removed under
vacuum, and the residue was extracted in CH2Cl2 (30 mL) and
filtered through Celite. The solvent was evaporated under
reduced pressure, hexane was added, and the complex 1 was
obtained as a red precipitate (0.11 g, 86%). IR (CH2Cl2; cm-1):
1948, 1864 (νCO). 1H NMR (CD2Cl2; δ): 9.54, 8.62, 8.04, and
8.00 (m, 2H each, phen), 4.24 (m, 1H, CH of η3-C3H5), 3.90 (d
(6.4), 2H, Hsyn), 1.70 (d (9.7), 2H, Hanti). 13C{1H} NMR (CD2-
Cl2; δ): 225.72 (CO), 152.96, 144.90, 139.29, 130.34, 127.74,
and 125.59 (phen), 73.81 (C2 of η3-C3H5), 55.92 (C1 and C3 of
η3-C3H5). 19F NMR (CD2Cl2; δ): -79.21. Anal. Calcd for
C16H13F3MoN2O5S: C, 41.39; H, 2.51; N, 5.36. Found: C, 41.13;
H, 2.49; N, 5.29.
Azir id in a t ion R ea ct ion . To a solution of 1 (6 mg, 0.01
mmol) in 20 mL of CH2Cl2 was added NaBAr′4 (10 mg, 0.01
mmol), and the mixture was stirred for 15 min. 2,6-Di-tert-
butylpyridine (5 µL, 0.02 mmol) was added, and then BDA (208
mg, 1.15 mmol) and EDA (0.12 mL, 1.15 mmol) were added.
The mixture was stirred under nitrogen for 8 h, and then the
volatiles were removed in vacuo. The remaining solid was
(b) F r om Com p ou n d 4. To a solution of 4 (0.07 g, 0.09
mmol) in THF (20 mL) was added allyl chloride (0.1 mL, 1.23
(26) Morales, D.; Pe´rez, J .; Riera, L.; Riera, V.; Miguel, D. Organo-
metallics 2001, 20, 4517.

Mo Lewis Acid as a Aziridination Catalyst
Organometallics, Vol. 21, No. 8, 2002 1545
mmol), and the mixture was heated to reflux for 45 min. The
solvent was evaporated to dryness. The residue was extracted
with CH2Cl2 and filtered through Celite. The solvent was
evaporated under reduced pressure, hexane was added, and
the complex 5 was obtained as a red precipitate. Yield: 0.059
g, 87%. The product exhibits the same spectroscopic properties
as the compound obtained in (a).
Aziridination reactions using compounds 3 and 5 were
conducted as described above for the achiral complex obtained
from 1.
0470-C02-01, and CICYT BQU2000-0219) for financial
support and for a predoctoral fellowship (to L.R.) and
the FICYT (PR-01-GE-7) for financial support and for
a postdoctoral scholarship (to D.M.).
Su p p or tin g In for m a tion Ava ila ble: Text giving a gener-
al description of crystal structure determination for compounds
3-5 and tables giving positional and thermal parameters,
bond distances, and bond angles for 3, 5, and 6. This material
is available free of charge via the Internet at http://pubs.acs.org.
Ack n ow led gm en t. We thank the Ministerio de
Ciencia y Tecnolog´ıa (Projects MCT-00-BQU-0220, PB97-
OM010958I