Synthesis, Structure and Reactivity of Molybdenum Imido and Oxo Complexes. X-ray Structure of MoCl3(NAr)L2 (Ar = 2,6-diisopropylphenyl: L = N-2',6'-diisopropyl Phenyl-2,5-dimethyl Benzamide)

Article abstract of DOI:10.1016/S0022-328X(98)00626-3

The reaction of MoCl4(O) with ArNCO (Ar = 2,6-iPr2Ph) afforded a series of paramagnetic oxo and imido Mo(V) complexes depending on the nature of the solvent used-in each case.An X-ray study of one of this complexes, MoCl3(NAr)L2 (L = N-2',6'-diisopropyl p

Full text of DOI:10.1016/S0022-328X(98)00626-3

Journal of Organometallic Chemistry 564 (1998) 85–92
Synthesis, structure and reactivity of molybdenum imido and oxo
complexes. X-ray structure of MoCl3(NAr)L2 (Ar=2,6-diisopropyl
phenyl; L=N-2’,6’-diisopropyl phenyl-2,5-dimethyl benzamide)1
F. Javier de la Mata a,*, Joseph W. Ziller b
a Departamento de Qu´ımica Inorga´nica, Uni6ersidad de Alcala´, Campus Uni6ersitario, E-28871 Alcala´ de Henares, Spain
b Department of Chemistry, Uni6ersity of California, Ir6ine, California 92717, USA
Received 10 February 1998; received in revised form 24 April 1998
Abstract
The reaction of MoCl4(O) with ArNCO (Ar=2,6-iPr2Ph) afforded a series of paramagnetic oxo and imido Mo(V) complexes
depending on the nature of the solvent used in each case. An X-ray study of one of this complexes, MoCl3(NAr)L2
(L=N-2’,6’-diisopropyl phenyl-2,5-dimethyl benzamide) (3) (orthorhombic, P212121, a=10.8194(8), b=23.528(2), c=23.914(2)
3
˚
˚
A, V=6087.4(9) A , Z=4) supports a pseudo-octahedral structure with the imido group occupying one of the axial positions.
Reduction of Mo(VI) and Mo(V) oxo and imido complexes in the presence of three equivalents of P(OMe)3 yields complexes
MoCl2(E)[P(OMe)3]3 (E=O (5), NAr (6)). Spectroscopic data of 5 and 6 show a pseudo-octahedral structure with the oxo or
imido ligand occupying one of the axial positions and the three phosphite ligands placed in the equatorial plane. Complexes 5 and
6 react with 3,3-diphenylcyclopropene leading to olefin complexes which are thermally unstable and decompose at room
temperature affording 1,1,6,6 tetraphenyl hexatriene, presumably via intermediate molybdenum vinyl alkylidenes. © 1998 Elsevier
Science S.A. Ltd. All rights reserved.
Keywords: Alkylidene; Cyclopropene; Imido; Molybdenum; Oxo; Tungsten
1. Introduction
vinyl alkylidene complexes of type W(ꢀCH–
CHꢀCPh2)(E)(OR)2(PX3) (E=NAr, O; PX3ꢀP(OMe)3,
PMePh2; R=C(CH3)(CF3)2) have been prepared via
the reaction of 3,3 diphenylcyclopropene with appropri-
ate tungsten(IV) precursors and subsequent thermal
ring-opening of the cyclopropene ligand. The tung-
Tungsten, molybdenum and rhenium are the three
metals that show the greatest activity for metathesis of
ordinary olefins in classical metathesis systems [1]. In
the past several years well-characterised tungsten and
molybdenum alkylidene complexes have been prepared
and some of the most versatile and controllable catalyst
are those of the type M(CHR’)(NAr)(OR)2 (M=Mo,
W; Ar=2,6-diisopropyl phenyl; OR=various alkox-
ides) [2].
sten(IV)
precursors
are
complexes
of
type
WCl2(E)(PX3)3 (E=O [5], NAr [6], PX3=P(OMe)3,
PMePh2) and their selection for this study was based
upon their ability to form a variety of y-acceptor
complexes of the form WCl2(L)(E)(PX3)2 (L=y-accep-
tor ligand) via substitution of one phosphine or phos-
phite ligand [7]. It was thought that molybdenum vinyl
Recently a number of tungsten imido [3] and oxo [4]
alkylidene
complexes
of
type
Mo(ꢀCH–
* Corresponding author. Tel.: +34
1 8854654; fax: +34 1
CHꢀCPh2)(OR)2(E)(PX3) (E=NAr, O; PX3ꢀP(OMe)3,
PMePh2) should be accessible by an analogous ap-
proach. In general, molybdenum catalyst might have
8854683; e-mail: jmata@inorg.alcala.es
1 Dedicated to Professor P. Royo on the occasion of his 60th
birthday.
0022-328X/98/$19.00 © 1998 Elsevier Science S.A. Ltd. All rights reserved.
PII S 0 0 2 2 - 3 2 8 X ( 9 8 ) 0 0 6 2 6 - 3

86
F. Ja6ier de la Mata, J.W. Ziller / Journal of Organometallic Chemistry 564 (1998) 85–92
certain advantages such as a greater tolerance of func-
tional groups. However, possible disadvantages could
be a greater tendency to be reduced and a lower
activity.
reacted with an excess of ArNCO in refluxing p-xylene
to give MoCl3(NAr)(L2) (3) in a 40–50% yield (Eq. 2).
In this paper we described the synthesis of oxo and
imido
molybdenum
complexes
of
type
MoCl2(E)[P(OMe)3]3 (E=O, NAr; Ar=2,6-iPr2–Ph)
and their reactivity with 3,3 diphenylcyclopropene.
In this particular case the imido molybdenum com-
plex was obtained without oxo impurities, perhaps due
to stabilisation of the final product by the new ligand,
N-2’,6’-diisopropyl phenyl-2,5-dimethyl benzamide.
ArNCO and p-xylene do not react in refluxing p-xylene
by themselves, which means that the formation of this
new ligand is likely due to electrophilic attack of the
isocyanate to a p-xylene molecule in a metal-catalysed
reaction.
Complex 3 reacted with THF giving paramagnetic
species (presumably MoCl3(NAr)(THF)2) and liberat-
ing two molecules of the benzamide ligand that could
now be characterised by NMR spectroscopy [10].
An X-ray study of complex 3 confirmed the nature
proposed for this complex and provided information
about the structure of some of these paramagnetic
2. Results and discussion
2.1. Synthesis and characterization of starting materials
Our first choices as precursors for the synthesis of
MoCl2(E)[P(OMe)3]3 (E=O, NAr; Ar=2,6-iPr2–Ph),
were MoCl4(O) and MoCl4(NAr), given the good re-
sults observed in the analogous chemistry of tungsten
[3,5](b). However, MoCl4(NAr) was not know at the
outset of this work. Schrock and coworkers reported
[2](c) that it is not possible to prepare this compound
using a synthetic protocol similar to that described for
MoCl4(Ntol)(THF) (prepared from MoCl4 and tolyl
azide [8]) or by reaction of MoCl4(O) and ArNCO in
octane (analogous to the synthesis of WCl4(NAr) from
WCl4(O) [9]).
Nevertheless, we decided to re-examine this last reac-
tion and carried it out in different solvents. In all cases,
paramagnetic yellow solids with different compositions
depending on the solvent used in the reaction were
obtained—the composition of these new compounds
was proposed on the basis of their reactivity (see next
section in this paper).
molybdenum(V) complexes. This complex has
a
pseudo-octahedral structure around the Mo atom with
the imido group occupying one of the axial positions
and the three chloride ligands placed in the equatorial
plane. The remaining axial and equatorial positions are
occupied by the benzamide ligands (Fig. 1).Selected
bond distances and angles are listed in Table 1.
The reaction of MoCl4(O) and ArNCO in refluxing
benzene, toluene and octane over 2–3 days gave
‘MoCl3(O)’ (1). We believe that this result is a conse-
quence of the great tendency of molybdenum to be
reduced and the necessity of higher reaction tempera-
tures in the case of benzene and toluene. In the case of
octane, the same result was obtained—despite the fact
that the temperature could be high enough—pre-
sumably due to solubility problems.
Other solvents were then examined, such as
chlorobenzene and p-xylene, where the solubility of
MoCl4(O) and the boiling temperature are high enough.
In chlorobenzene
a mixture of ‘MoCl3(O)’ and
‘MoCl3(NAr)’ (2) was obtained. The amount of 2 in-
creased slowly with increasing reaction times but could
not be driven to complexion (Eq. 1).
The reaction in p-xylene is particularly interesting
due to the nature of the product obtained. MoCl4(O)
Fig. 1.

F. Ja6ier de la Mata, J.W. Ziller / Journal of Organometallic Chemistry 564 (1998) 85–92
87
˚
The distances Mo–N(3) (1.731(7) A), Mo–Cl(1), Mo–
Complex 5 is a diamagnetic green solid, soluble in
˚
Cl(2) and Mo–Cl(3) (2.367(2), 2.408(2) and 2.413(2) A,
respectively) are in the expected range. The distances
Mo–O(1) and Mo–O(2) (2.102(5) and 2.239(5) A) are
aromatic hydrocarbons, tetrahydrofuran and chlorinated
1
solvents. The H and 13C-NMR spectra in deuterated
˚
benzene show a triplet and a doublet that correspond,
respectively, to two mutually trans phosphite ligands and
one phosphite ligand trans to a chloride ligand. The
31P-NMR spectrum shows coupling between the unequiv-
alent phosphite ligands that gives rise to two resonances
that appear as a doublet and a triplet in a 2:1 ratio. These
data are similar to those of analogous complexes such as
WCl2(O)[P(OMe)3]3 [5](a) and are consistent with the
expectedmeridionalarrangementofthephosphiteligands
[3].
shorter than the Mo–O distances found for the coordi-
nation of an oxygen-containing ligand to a molybdenum
centre [11] and in particular the Mo–O(1) bond length
is considerably shorter. The different length of both
Mo–O distances could be due to the strong trans influence
of the imido ligand over the Mo–O(2) bond [12].
Despite the possible use of this new imido molybde-
num(V)complex(3)asprecursorforthesynthesisofimido
complexes of molybdenum(IV), it was decided to explore
otherwaystosynthesizethedesiredproductMoCl4(NAr).
The corresponding imido complex MoCl2(NAr)-
[P(OMe)3]3 (6) could be prepared by reduction of the
mixture MoCl3(NAr)(dme) and ‘MoCl4(NAr)’ with Na/
Hg in the presence of P(OMe)3. Since the exact ratio of
these complexes was unknown, it was not possible to
calculate which is the stochiometric amount of sodium
that was necessary for the reduction which could decrease
the overall yield. Nevertheless, using 1.5 equivalents of
a 6% Na amalgam it was possible to obtain 6 as a yellow
solid in :60% yield. There are other ways to synthesize
6 (Eq. 5) but final yields were always lower than using
the synthetic route described above [15].
Schrock
and
co-workers
have
shown
that
MoCl2(NAr)2(dme) can be prepared from MoCl2O2 and
ArNH2 in high yield [2](c). We tried a similar reaction
for the synthesis of MoCl4(NAr) from MoCl4(O).
The addition of two equivalents of 2,6-lutidine, five
equivalents of Me3SiCl and one equivalent of ArNH2 to
a solution of MoCl4(O) in dimethoxyethane cooled to
−30°C, leads the formation of a orange–red solution
from
which
yellow
crystalline,
paramagnetic
MoCl3(NAr)(dme) (4) could be isolated. It was identified
on the basis of its reactivity (see next section) and its
elemental analysis (see experimental part). Complex 4
reacted with THF, forming a new organometallic species
(presumably MoCl3(NAr)(THF)2) and liberating
1
dimethoxyethane which can be observed by H-NMR.
Complex 4 was not the only product obtained in this
reaction and the presence of a more soluble diamagnetic
complex, probably MoCl4(NAr) [13], that decreased the
yield of 4, was also noticed (Eq. 3).
We have tried to isolate this Mo(VI) complex from the
reaction mixture several times but significant amounts of
complex 4 were always found, that we have not been able
to remove so far.
2.2. Synthesis of complexes of type MoCl2(E)
[P(OMe)3]3 (E=O, NAr)
Complex MoCl2(O)[P(OMe)3]3 (5) was prepared by
direct reduction of MoCl4(O) with two equivalents of Na
amalgam in the presence of trimethyl phosphite [14] (Eq.
4).

88
F. Ja6ier de la Mata, J.W. Ziller / Journal of Organometallic Chemistry 564 (1998) 85–92
1
Table 1
The H-NMR spectrum of 6 presents resonances at
l=6.99 (m, Haromatic), l=4.62 (sp, 2, JH–H=6.6 Hz,
CH-CMe2) and l=1.32 (d, 12, JH–H=6.6 Hz, CH-
Selected bond lengths and angles for 3
˚
6
Bond lengths (A)
CMe2) corresponding to the protons of the imido group
and resonances at l=3.69 (t, 18, JPH=5.1 Hz) and
l=3.59 (d, 9, JPH=10.5 Hz) corresponding to the
three phosphite ligands. These data are consistent with
the expected meridional arrangement of the phosphite
ligands. Accordingly, we propose for complexes 5 and 6
the same pseudo-octahedral structure found in
analogous tungsten complexes WCl2(E)[P(OMe)3]3 [3,5]
(E=O, NAr).
Mo(1)–Cl(1)
Mo(1)–Cl(3)
Mo(1)–O(2)
O(1)–C(1)
N(1)–C(1)
N(2)–C(22)
N(3)–C(43)
2.367(2) Mo(1)–Cl(2)
2.408(2)
2.102(5)
1.731(7)
1.253(9)
1.461(10)
1.443(10)
2.413(2) Mo(1)–O(1)
2.239(5) Mo(1)–N(3)
1.258(9) O(2)–C(22)
1.311(10) N(1)–C(10)
1.327(10) N(2)–C(31)
1.390(10)
Bond angles (°)
Cl(1)–Mo(1)–Cl(2) 92.7(1)
Cl(2)–Mo(1)–Cl(3) 170.5(1)
Cl(2)–Mo(1)–O(1) 89.7(1)
Cl(1)–Mo(1)–O(2) 83.6(1)
Cl(3)–Mo(1)–O(2) 89.2(1)
Cl(1)–Mo(1)–N(3) 100.7(2)
Cl(3)–Mo(1)–N(3) 94.9(2)
O(2)–Mo(1)–N(3) 174.0(2)
Cl(1)–Mo(1)–Cl(3) 91.1(1)
Cl(1)–Mo(1)–O(1) 162.7(2)
Cl(3)–Mo(1)–O(1) 84.2(1)
Cl(2)–Mo(1)–O(2) 82.5(1)
O(1)–Mo(1)–O(2)
Cl(2)–Mo(1)–N(3) 93.1(2)
O(1)–Mo(1)–N(3) 96.2(3)
79.8(2)
2.3. Reacti6ity of MoCl2(E)[P(OMe)3]3 with
3,3-diphenylcyclopropene
Complexes of type MoCl2(E)[P(OMe)3]3 (E=O (5),
E=NAr (6)) react with one equivalent of 3,3-diphenyl-
cyclopropene to give p2-cyclopropene derivatives simi-
lar to those obtained for the analogous tungsten(IV)
complexes.
3. Conclusions
Reaction of 5 and 3,3-diphenylcyclopropene gave rise
to the formation of Mo(p2-diphenylcyclopropene)Cl2
(O)[P(OMe)3]2 (7). Spectroscopic data of 7 (See experi-
mental part) are analogous to those of W(p2-diphenyl-
cyclopropene)Cl2(O)[P(OMe)3]2 [4]. These data suggest
a distorted octahedral structure for 7 with the olefin
carbons occupying one position in the equatorial plane
and the oxygen atom occupying one of the axial posi-
tions cis to the cyclopropene ligand. The two phosphite
groups have to be mutually trans and the two chloride
ligands occupy the remaining equatorial and axial posi-
tions. Complex 7 is thermally unstable, has a half-live
time of 3 h at room temperature, and decomposes
leading to the dimerization product of the diphenylcy-
clopropene (Ph2CꢀCH–CHꢀCH–CHꢀCPH2) and re-
covering some of the starting material 5 (See Scheme 2).
Recently it has been shown [4] that the same result is
obtained with analogous tungsten complexes and the
presence of carbene species in the dimerization pro-
cess was demonstrated. In the tungsten case, it was
also probed that the change of P(OMe)3 by phosphines
such as PMe2Ph or PMePh2 gives rise to more
stable p2-cyclopropene complexes. We infer similar be-
haviour for analogous phosphine molybdenum
complexes, which are currently under investig-
ation.
The reaction of MoCl4(O) with ArNCO afforded
paramagnetic oxo and amido Mo(V) complexes. The
X-ray structure of one of these complexes,
MoCl3(NAr)L2 (L=N-2’,6’-diisopropyl phenyl-2,5-
dimethyl benzamide) (3), supports a pseudo-octa-
hedric arrangement around the molybdenum atom
with the imido group occupying one of the axial po-
sitions.
Reduction of these Mo(V) complexes with Na
amalgam in the presence of three equivalents of
P(OMe)3 yielded MoCl2(E)[P(OMe)3]3 (E=O (5),
NAr (6)). These molybdenum(IV) complexes react
with 3,3-diphenylcyclopropene affording olefin com-
plexes Mo(p2-diphenylcyclopropene)Cl2(E)[P(OMe)3]
(E=O, NAr) similar to those obtained with
analogous tungsten complexes [4]. The thermal stabil-
ity of the molybdenum derivatives is quite low and
they decompose within hours at room temperature to
give 1,1,6,6,-tetraphenyl hexatriene.
4. Experimental details
All manipulations were carried out under argon us-
ing standard Schlenck techniques or in a nitrogen-filled
glove box equipped with a −40°C freezer. Argon was
purified by passage through columns Chemalog R3-11
Complex 6 also reacts with 3,3-diphenylcyclopropene
at room temperature to yield Mo(p2-diphenylcyclo-
propene)Cl2(NAr)[P(OMe)3] (8), which presents again a
low thermal stability and decomposes over 40°C, gener-
ating once again the dimerization product of 3,3-
diphenylcyclopropene, Ph2CꢀCH–CHꢀCH–CHꢀCPh2
(Scheme 1).
˚
catalyst and Lynde 4-A molecular sieves. NMR spectra
were recorded with either a JEOL FX-90Q (89.60 MHz
1H, 22.53 MHz 13C, 36.20 MHz 31P) or a QE-300 Plus
(300.10 MHz 1H, 75.49 MHz 13C) spectrometer. All
1
coupling constants are reported in Hz. For the H and

F. Ja6ier de la Mata, J.W. Ziller / Journal of Organometallic Chemistry 564 (1998) 85–92
89
Scheme 1.
13C-NMR virtual triplets resonances of the trans phos-
phite ligands, the coupling constant N=[2JHP+4JHP
are given, where N is the separation of the outer lines of
the triplet [16].
chlorobenzene as solvent gave a yellow product that
was identified as a mixture of 1 and 2 according to the
reactivity exhibited by this solid.
]
Toluene, benzene, diethyl ether and tetrahydrofuran
were purified by passage through a column of La
Roche A-2 alumina and Engelhard Q-5 reactant (sup-
ported copper oxide), degassed by freeze-pump-thaw
three times. Pentane was stirred over concentrated
H2SO4, dried over CaH2 and MgSO4 and vacuum
transferred from sodium–benzophenone ketyl. C6D6
and THF-d8 were dried over sodium–benzophenone
ketyl and vacuum transferred prior to use. P(OMe)3
was vacuum-transferred from Na and then subjected to
several freeze-pump-thaw cycles. MoCl4(O), ArNCO,
ArNH2, 2,6-lutidine and SiMe3Cl were purchased by
commercial sources and purified by distillation prior to
use. Finally 3,3-diphenylcyclopropene was prepared fol-
lowing a procedure by Moore [17].
4.1.3. Formation of MoCl3(NAr)(L2).
L=N-2’,6’-diisopropylphenyl-2,5-dimethyl benzamide 3
A 10 ml p-xylene solution of aryl isocyanate (2.5 ml,
11.7 mmol) was added over a red suspension of
MoCl4(O) (1 g, 3.9 mmol) in p-xylene. The resulting
mixture was refluxed for over 24 h and then allowed to
settle. Filtration afforded a yellow–brown solution.
This solution was concentrated under vacuum until
only 5 ml were left and then cooled to 0°C for 12 h to
give yellow crystals of 3 (1.77 g, 45%). Anal. Calcd. for
(C54H71Cl3O2N3Mo): C, 65.09; H, 7.18; N, 4.21%;
Found: C, 64.89; H, 7.12; N, 4.18%.
4.2. MoCl3(NAr)(dme) 4
4.1. Reaction of MoCl4(O) with ArNCO
Over a stirred solution of MoCl4(O) (0.67 g, 2.6
mmol) in dimethoxyethane (30 ml) cooled to −30°C,
the following were added were added in this order: 2,6
lutidine (0.56 ml, 5.2 mmol) in 5 ml of DME, Me3SiCl
(1.42 ml, 13.0 mmol) in 10 ml of DME and ArNH2
(0.46 ml, 2.6 mmol) in 5 ml of DME.
Addition of 2,6 lutidine resulted in a green suspen-
sion, and this colour persisted until all chemicals were
added. The mixture was allowed to warm to room
temperature over a period of 3 h. When the tempera-
ture began to increase the solution’s colour changed
from green to orange and at the same time began the
precipitation of a white solid.
4.1.1. Formation of ‘MoCl3(O)’ 1
A 5 ml benzene solution of 2,6-diisopropyl phenyl
isocyanate (0.81 ml, 3.8 mmol) was added to a red
suspension of MoCl4(O) (0.97 g, 3.8 mmol) in benzene,
toluene or octane. The resulting mixture was refluxed
over 24 h after which the colour of the suspension
changed from red to brown–yellow, then the mixture
was allowed to settle. Filtration afforded a brown–yel-
low solution. Solvent was removed under vacuum and
the resulting dark yellow residue washed three times
with pentane (10 ml) to yield a yellow powder charac-
terised as 1 on the basis of its paramagnetic character
and its reactivity (0.5 g, 60%).
When the reaction finished, the precipitate was
filtered and the solution concentrated in vacuo until
half of its initial volume remained. At this stage, a
crystalline yellow solid precipitated from the solution
4.1.2. Formation of ‘MoCl3(O)’ 1 and ‘MoCl3(NAr)’ 2
Repetition of the above procedure, employing

90
F. Ja6ier de la Mata, J.W. Ziller / Journal of Organometallic Chemistry 564 (1998) 85–92
Scheme 2.
4.4. MoCl2(NAr)[P(OMe)3]3 6
and was recovered by filtration, dried under vacuum
and characterised as the paramagnetic complex
MoCl3(NAr)(dme) (0.74 g, 60%). This solid presents
few solubility in C6D6 and CD2Cl2 but is soluble in
4.4.1. Method A
Over a sodium amalgam (6% of Na, 0.04 g of Na,
1.8mmol) a 30-ml toluene solution of 3 (0.9 g, 0.9
mmol) was transferred via canula, next P(OMe)3 (0.32
ml, 2.71 mmol) was added via syringe to the reaction
flask. The reaction mixture was stirred for 12 h and
then filtered leading to a brown-solution which was
evaporated to dryness. In addition to the desired
product, the brown residue contained two molecules of
1
THF-d8. The H-NMR spectrum in THF-d8 shows the
paramagnetic character of this solid and also shows
two signals corresponding to free DME. Anal. Calcd.
for (C16H27Cl3O2NMo): C, 41.1; H, 5.82; N, 2.99%;
Found: C, 41.37; H, 5.74; N, 3.03%.
4.3. MoCl2(O)[P(OMe)3]3 5
N-2’,6’-diisopropyl
phenyl-2,5-dimethyl
bezamide
whose solubility is quite similar to 6 in the usual
solvents. Extracting several times with diethyl ether, it
was possible to remove this ligand and isolate the
complex MoCl2(NAr)[P(OMe)3]3 in low yield. 1H-NMR
(C6D6): l 6.99 (m, 3, Haromatic), 4.62 (sp, 2, JHH=6.6
Hz, –CHMe2), 3.69 (t, 18, N=10.5 Hz, P(OMe)3), 3.59
(d, 9, JHP=10.5 Hz, P(OMe)3), 1.32 (d, 12, JHH=6.6
Hz). Anal. Calcd. for (C21H44Cl2NO9P3Mo): C, 35.31;
H, 6.21; N, 1.96%: Found: C, 35.08; H, 5.87; N, 1.85%.
4.3.1. Method A
A toluene solution of MoCl4(O) (0.86 g, 3.4 mmol)
was added over a sodium amalgam (6% Na, 0.16 g of
Na, 6.8 mmol), and then P(OMe)3 (1.20 ml,
10.2mmol) was added via syringe.
The original solution turned green as the reaction
mixture was stirred for 12 h. This suspension was
filtered and the solvent removed under vacuum, the
resulting green residue was left under dynamic vacuum
for an additional 12 h period and then extracted with
diethyl ether (2×15 ml). This ether solution was con-
centrated in vacuo and cooled to −20°C, leading af-
ter 24 h to green crystals of MoCl2(O)[P(OMe)3]3 (1.31
4.4.2. Method B
A 30-ml toluene solution of MoCl3(NAr)(dme) and
‘MoCl4(NAr)’ (0.62 g) was added over a sodium
amalgam (6% of Na, 0.035 g of Na) and then P(OMe)3
(0.47 ml, 3.97 mmol) was incorporated to the reaction
mixture via syringe. This suspension was stirred for 12
h and then filtered and concentrated to dryness, the
resulting residue was left under dynamic vacuum for an
additional 12 h period in order to remove the excess of
phosphite. Next, the brown oily product was washed
with pentane (3×10 ml) giving rise to a yellow–brown
solid that was identified as complex 6 (0.55 g, 58%).
1
g, 70%). H-NMR (C6D6): l 3.77 (t, 18, N=10.5 Hz);
3.64 (d, 9, JHP=10.5 Hz). 13C-NMR (C6D6) l 52.8(t,
2 P(OMe)3); 52.6 (d, JC–P=5.36 Hz). 31P-NMR
(C6D6) l 142.8 (t, 1, JPP=21 Hz); 128.5 (d, 2, JPP
21 Hz). Anal. Calcd. for (C9H27Cl2O10P3Mo): C,
19.47; H, 4.90%; Found: C, 19.08; H, 4.87%.
=
4.3.2. Method B
A yellow toluene solution of ‘MoCl3(O)’ (0.4 g,
1.83 mmol) was added over a sodium amalgam (6%
Na, 0.042 g of Na, 1.83 mmol) and just prior to
stirring, P(OMe)3 (0.65 ml, 5.5 mmol) was added via
syringe.
Working up the reaction as in the method A, it was
also possible to get green crystals of 5 (0.35 g, 35%).
4.5. Obser6ation of Mo(p2-diphenylcyclopropene)Cl2-
(O)[P(OMe)3]2 7
A 0.5-ml solution of 3,3-diphenylcyclopropene (0.007
g, 0.036 mmol) in deuterated benzene was added over
MoCl2(O)[P(OMe)3]3 (0.02 g, 0.036 mmol) and the

F. Ja6ier de la Mata, J.W. Ziller / Journal of Organometallic Chemistry 564 (1998) 85–92
91
resulting mixture was monitored by 1H-NMR spec-
troscopy. After 10 min, signals appear which correspond
to complex 7, which keep increasing over a 12 h period.
After this time, joined to the signals corresponding to the
starting material and complex 7, it is possible to see the
signals corresponding to the dimerization product of
3,3-diphenyl cyclopropene in the spectrum. After 24 h
only the signals corresponding to 5 and Ph2CꢀCH–
Crystallographic Computing Package [20] or the
SHELXTL PLUS program set [21]. The analytical scat-
tering factors for neutral atoms were used throughout
the analysis [22]; both the real (Df %) and imaginary
(iDf %%) components of anomalous dispersion were in-
cluded. The quantity minimised during least-squares
analysis was Sw(Fo−Fc)2 where w−1=|2(F)+0.00102.
The structure was solved by direct methods and
refined by full-matrix least-squares techniques. Hydro-
1
CHꢀCH–CHꢀCPh2 are present in the H-NMR spec-
trum. 1H-NMR of 7 (C6D6):l 7.05 (m, 10, Haromatic), 5.80
(t, 2, JHH=8.1 Hz, CHꢀCH), 3.61 (t, 18, N=10.8 Hz).
gen atoms were included using a riding model with
2
˚
˚
d(C–H)=0.96 A and U(iso)=0.08 A . There is a
molecule of C8H10 present per formula unit. Refinement
of positional and thermal parameters led to convergence
with RF=5.4%; RwF=6.5% and GOF=1.52 for 597
variables refined against those 2231 data with F\
2.0|(F). A final difference-Fourier synthesis yielded
4.6. Obser6ation of Mo(p2-diphenylcyclopropene)Cl2-
(NAr)[P(OMe)3] 8
A 0.5-ml solution of 3,3-diphenyl cyclopropene (0.004
g, 0.021 mmol) in deuterated benzene was added over
MoCl2(NAr)[P(OMe)3]3 (0.015 g, 0.021 mmol) placed in
z(max)=0.60 e A−3. The absolute structure was deter-
˚
1
mined by refinement of the Rogers’ p-parameter [23]
(p=0.93(15)).
a NMR tube. The reaction was followed by H-NMR
spectroscopy. The signals corresponding to complex 8
start to grow with the reaction time but the reaction
seems to stop after 16 h when the amount of 8 in the
mixture is :50%. Heating to 40–45°C at this stage
leads to the decomposition of the product, with the
appearance once again of the dimerization product of
3,3-diphenylcyclopropene. The identification of complex
8 and the assignment of the NMR signals of this
complex were made by comparison with the analogous
tungsten complex [3]. 1H-NMR of 8 (C6D6): l 7.1 (m, 13,
Haromatic), 5.35 (dd, 1, JHH=4.2 Hz, JHP=0.6 Hz,
5. Supplementary material
A complete description of the X-ray experiment for 3,
and tables of crystal data, atomic coordinates, thermal
parameters, distances and angles (17 pages), torsion
angles (2 pages), and structure factor amplitudes (10
pages). Ordering information is given on any current
masthead page.
CH
6 –CH), 5.04 (dd, 1, JHH=4.2 Hz, JHP=13.8 Hz),
Table 2
3.28 (d, 9, JHP=10.8 Hz, P(OMe)3), 1.31 (d, 6, JHH
6.6, CHCMeMe), 1.30 (d, 6, JHH=6.6, CHCMeMe).
=
Experimental data for the X-ray diffraction study of 3
Formula
FW
C54H69N3O2Cl3Mo–C8H10
1100.6
4.7. Collection of X-ray diffraction data
Temperature (K)
Crystal system
Space group
163
Orthorhombic
P212121
10.8194(8)
23.528(2)
23.914(2)
6087.4(9)
4
1.201
Siemens P3
Mo–Kh (u=0.710730 A)
Highly oriented graphite
A yellow crystal of approximate dimensions 0.27×
0.42×0.46 mm was oil-mounted [18] on a glass fibber
and transferred to the Siemens P3 diffractometer. The
determination of Laue symmetry, crystal class, unit cell
parameters and the crystal’s orientation matrix were
carried out according to procedures similar to those of
Churchill [19]. Intensity data were collected at 163 K
using a q−2q scan technique with Mo–Kh radiation
under the conditions described in Table 2. All 4502 data
were corrected for Lorentz and polarisation effects and
were placed on an approximately absolute scale. The
diffraction symmetry was mmm with systematic absences
h00 for h=2n+1, 0k0 for k=2n+1 and 00l for
l=2n+1. The non-centrosymmetric orthorhombic
space group P212121 is therefore uniquely defined.
˚
a, A
˚
b, A
˚
c, A
3
˚
V, A
Z
Dcalcd, g cm−3
Diffractometer
Radiation
˚
Monochromator
Data collected
Scan type
Scan width
Scan speed
+h, +k, +l
q−2q
1.2° plus Kh-separation
3.0° min−1 (in ꢀ)
2q range, °
4.0–45.0
0.389
4502
4147
597
5.4%
6.5%
1.52
m(Mo–Kh), mm−1
Reflections collected
Reflections with F\2.0|(F)
No. of variables
RF
4.8. Solution and refinement of the crystal structure
RwF
Goodness of fit
All crystallographic calculations were carried out us-
ing either our locally modified version of the UCLA

92
F. Ja6ier de la Mata, J.W. Ziller / Journal of Organometallic Chemistry 564 (1998) 85–92
[8] C.Y. Chou, J.C. Huffman, E.A.J. Maata, Chem. Soc. Chem.
Acknowledgements
Commun. (1984) 1184.
[9] R.R. Schrock, S.A. Krause, K. Knoll, J. Feldman, J.S. Murdzek,
D.C.J. Yang, Mol. Catal. 46 (1988) 243.
We gratefully acknowledge Prof. R.H. Grubbs for his
support and valuable help, and F.J.M. thanks the Min-
isterio de Educacion y Ciencia of Spain for a postdoc-
toral fellowship.
[10] 1H-NMR data of N-2’,6’-diisopropyl phenyl-2,5-dimethyl beza-
mide: 1H-NMR (THF-d8): l 8.65 (s br, 1, –NH
6
–), 7.13 (m, 6,
Haromatic), 3.3 (sp, 2, JHH=6.9 Hz, –CH6 CMe2), 2.46 (s, 3, CH3),
2.35 (s, 3, CH3), 1.23 (d, 12, JHH=6.9 Hz, –CHCMe2). 13C-
NMR ((THF-d8): l 169.2 (s, OꢀC–), 147.4, 138.0, 135.8, 134.2,
133.7, 131.5, 130.7, 128.3, 128.2 and 123.6 (10 aromatic carbons),
29.5 (s, –CHCMe2), 24.0 (s, –CHCMe2), 21.0 (s, CH3), 19.7 (s,
CH3).
References
[11] See for example: (a) H. Lam, G. Wilkinson, B. Hussain-Bates,
M.B.J. Hursthouse, Chem. Soc. Dalton Trans (1993) 781. (b)
Reference 2c.
[12] W.A. Nugent, J.M. Mayer, Metal–Ligand Multiple Bonds, Wi-
ley, New York, 1988 and references cited therein.
[13] This new complex of Mo(VI) is quite unstable and decomposes
easily in the presence of traces of moisture. The 1H-NMR
(C6D6): l 7.02 (t, JH–H=8.04 Hz, 1H), 6.90 (d, JH–H=8.04 Hz,
2H), 4.62 (sp, JH–H=6.90 Hz, 1H), 1.37 (d, JH–H=6.90 Hz,
2H).
[14] Complex 5 can be prepared also by reduction of ‘MoCl3(O)’ in
the presence of trimethyl phosphite but always in lower yields.
[15] The reduction of MoCl3(NAr)L2 (3) with Na/Hg in the presence
of three equivalents of phosphite leads the formation of 6
liberating two molecules of N-2’,6’-diisopropyl phenyl-2,5-
dimethyl benzamide, in low to moderate yields.
[1] (a) K.J. Ivin, Olefin Metathesis, Academic Press, London, 1983.
(b) R.H. Grubbs, In: G. Wilkinson, F.G.A. Stone, E.W. Abel
(Eds.), Comprehensive Organometallic Chemistry, Vol. 8, Perga-
mon, New York, 1982. (c) V. Dragutan, A.T. Balaban, M.
Dimonie, Olefin Metathesis and Ring Opening Polymerization of
Cyclo-Olefins, 2nd ed., Wiley-Interscience, New York, 1985. (d)
M. Leconte, J.M. Basset, F. Quignard, C. Larroche, In: P.R.
Braterman, (Ed.), Reactions of Coordinated Ligands, Plenum,
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M.J. O’Regan, Am. Chem. Soc. 112 (1990) 3875.
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[4] F.J. De la Mata, R.H. Grubbs, Organometallics 15 (1996) 577.
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[6] (a) D.C. Bradley, M.B. Hursthouse, K.M.A. Molik. A.J. Niel-
son, R.L.J. Short, Chem. Soc. Dalton. Trans. (1983) 2651–2656.
(b) A.J. Nielson, R.E. McCarley, S.L. Laughlin, C.D. Carlson,
In: J.M. Schreeve, (Ed.), Inorg. Syntheses, vol. 24, Wiley, New
York, 1986, pp. 194–200. (c) Reference 3.
[7] (a) F.-M. Su, C. Cooper, S.J. Geib, A.L. Rheingold, J.M.J.
Mayer, Am. Chem. Soc. 108 (1986) 3545–3547. (b) F.-M. Su,
J.C. Bryan, S. Jang, J.M. Mayer, Polyhedron 8 (1989) 1261–
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D.C.J. Ware, Chem. Soc. Dalton Trans (1990) 1173–1178.
[16] R.K. Harris, Can. J. Chem. 42 (1964) 2275.
[17] J.S. Moore, S.T. Nguyen, R.H. Grubbs, unpublished results.
[18] The crystal was immersed in a lube-oil additive which allows for
manipulation on the bench-top and prevents decomposition due
to air or moisture. The crystal was secured to a glass fibre (the
oil acts as the adhesive) which is attached to an elongated brass
mounting-pin. Further details appear in H. Hope, In: A.L.
Wayda, M.Y. Darensbourg (Eds.), Experimental Organometallic
Chemistry: A Practicum in synthesis and Characterization, ACS
Symposium Series No. 357, 1987.
[19] M.R. Churchill, R.A. Lashewycz, F.J. Rotella, Inorg. Chem. 16
(1977) 265–271.
[20] C. Strouse, UCLA Crystallographic Computing Package, Uni-
versity of California Los Angeles, 1981, personal communica-
tion.
[21] G.M. Sheldrick, Siemens Analytical X-Ray Instruments,
SHELXTL Program, Madison, WI, 1990.
[22] International Tables for X-Ray Crystallography, Vol. C, Dor-
drecht: Kluwer Academic Publishers, 1992.
[23] D. Rogers, Acta. Cryst. A37 (1981) 734–741.
.