Reaction of phosphoranes with Mo(N-2,6-i-Pr2C6H 3) (CHCMe3)[OCMe(CF3)2]2: Synthesis and reactivity of an anionic imido alkylidyne complex

Article abstract of DOI:10.1021/om060501e

The reaction of Ph₃P=CH₂ with Mo(NAr)(CHCMe ₃)[OCMe (CF₃)₂]₂ (Ar = 2,6-i-Pr ₂C₆H₃) produces the anionic alkylidyne complex {Ph₃PMe}{Mo(NAr)(CCMe₃)[OCMe(CF₃) ₂]₂}. An X-ray structure determination of the complex reveals a bent Mo-N-C angle for the imido group, as expected when a metal-carbon triple bond is present. The anion has been shown to react with electrophiles predominantly at the imido nitrogen.

Full text of DOI:10.1021/om060501e

Organometallics 2006, 25, 4301-4306
4301
Reaction of Phosphoranes with
Mo(N-2,6-i-Pr2C6H3)(CHCMe3)[OCMe(CF3)2]2: Synthesis and
Reactivity of an Anionic Imido Alkylidyne Complex
Zachary J. Tonzetich, Richard R. Schrock,* and Peter Mu¨ller
Department of Chemistry 6-331, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
ReceiVed June 6, 2006
The reaction of Ph3PdCH2 with Mo(NAr)(CHCMe3)[OCMe(CF3)2]2 (Ar ) 2,6-i-Pr2C6H3) produces
the anionic alkylidyne complex {Ph3PMe}{Mo(NAr)(CCMe3)[OCMe(CF3)2]2}. An X-ray structure deter-
mination of the complex reveals a bent Mo-N-C angle for the imido group, as expected when a metal-
carbon triple bond is present. The anion has been shown to react with electrophiles predominantly at the
imido nitrogen.
1
immediate color change from yellow to deep orange. The H
NMR spectrum of the product showed it to be a single com-
Introduction
Olefin metathesis catalysts of the type Mo(NR)(CHR′)-
(OR′′)2,1 and variations that contain chiral diolates,2 are known
to decompose either via bimolecular decomposition of alkyli-
denes or via rearrangement of some intermediate metalacyclo-
butane complex. The metal is “reduced” in the process by two
electrons to a d2 species of some type (e.g., a bimetallic species
that contains a MdM bond3). It would be highly desirable to
discover a way of regenerating the catalyst through the use of
an alkylidene source such as a phosphorus or sulfur ylide. The
first demonstration of a reaction of this type was transfer of an
alkylidene from an alkylidene phosphorane to a Ta(III) species
to generate a Ta(V) bis-cyclopentadienyl complex.4 Alkylidenes
also have been transferred from phosphorus to W(IV) species
to yield W(VI) alkylidene complexes.5 However, in no case was
the resulting alkylidene species a known metathesis catalyst.
Therefore we decided to turn to an exploration of potential
reactions between the prototypical metathesis catalyst Mo(NAr)-
(CHCMe3)[OCMe(CF3)2]2 (Ar ) 2,6-i-Pr2C6H3) and phosphorus
ylides, reasoning that if a Mo(NAr)(CHR)[OCMe(CF3)2]2 spe-
cies were to be regenerated from some “Mo(NAr)[OCMe-
(CF3)2]2” species in a reaction involving an alkylidene phos-
phorane, then the resulting alkylidene ideally would have to
react relatively slowly with that phosphorane in order to avoid
potentially destructive secondary reactions. We report here
reactions between Mo(NAr)(CHCMe3)[OCMe(CF3)2]2 and sev-
eral phosphoranes. Only one clean reaction was observed in
the case of one phosphorane; Mo(NAr)(CHCMe3)[OCMe-
(CF3)2]2 reacts with Ph3PdCH2 to give an anionic imido alkyl-
idyne complex, {Ph3PMe}{Mo(NAr)(CCMe3)[OCMe(CF3)2]2}.
pound that has no alkylidene HR resonance. The H and 13C
1
NMR features are consistent with the product being an anionic
alkylidyne complex (R ) Me, 1, or R ) Ph, 1′; eq 1). The
product can be isolated readily in high yield. Proton NMR
spectra reveal broad resonances for the isopropyl methyl groups
of the arylimido ligand, consistent with hindered rotation about
the N-Cipso bond. For 1, these resonances coalesce near 40 °C
at 500 MHz in benzene-d6. Spectra in tetrahydrofuran-d8 show
coalescence of the isopropyl methyl groups at 20 °C. Therefore
ion pairing may be responsible for a slightly more hindered
rotation in benzene. A 13C NMR spectrum of purified 1 shows
a resonance at 300.75 ppm in C6D6 that can be assigned to the
alkylidyne carbon atom. No JCP coupling was observed, con-
sistent with the ionic formulation shown in eq 1, while the 19
F
NMR spectrum displays two resonances for the diastereotopic
trifluoromethyl groups, as anticipated.
Slow cooling of a saturated toluene/pentane solution of 1
afforded red spars suitable for X-ray diffraction. The solid-state
structure contains two independent ion pairs in the asymmetric
unit. A POV-ray rendering of one of the molecules is displayed
in Figure 1, and relevant crystallographic details are listed in
Table 1. The imido alkylidyne formulation is consistent with
the large Mo1-C1-C2 bond angle (168.2(2)°) and the bent
Mo1-N1-C21 angle (141.16(17)°; cf. 169-175° in typical
four-coordinate alkylidenes of this type1). The anions in each
molecule are virtually identical except for the Mo-Nimido-Cipso
bond angle, which is 141.16(17)° in the compound shown in
Figure 1 and 158.66(17)° in the other (see Table S1 in the
Supporting Information). The reason for the large difference in
bond angles might be ascribed to a closer approach of the phos-
phonium cation in the compound shown in Figure 1 versus the
Results
Addition of 1 equiv of Ph3PdCH2 to Mo(NAr)(CHCMe2R)-
[OCMe(CF3)2]2 (R ) Me or Ph) in benzene-d6 resulted in an
* To whom corresondence should be addressed. E-mail: rrs@mit.edu.
(1) Schrock, R. R. Chem. ReV. 2002, 102, 145.
(2) Schrock, R. R.; Hoveyda, A. H. Angew. Chem., Int. Ed. 2003, 42,
4592.
(3) Lopez, L. P. H.; Schrock, R. R.; Mu¨ller, P. Organometallics 2006,
25, 1978.
(4) Sharp, P. R.; Schrock, R. R. J. Organomet. Chem. 1979, 171, 43.
(5) (a) Johnson, L. K.; Virgil, S. C.; Grubbs, R. H.; Ziller, J. W. J. Am.
Chem. Soc. 1990, 112, 5384. (b) Johnson, L. K.; Frey, M.; Ulibarri, T. A.;
Virgil, S. C.; Grubbs, R. H.; Ziller, J. W. J. Am. Chem. Soc. 1993, 115,
8167.
10.1021/om060501e CCC: $33.50 © 2006 American Chemical Society
Publication on Web 08/03/2006

4302 Organometallics, Vol. 25, No. 18, 2006
Tonzetich et al.
sensitive to ion pairing. Therefore it is likely that crystal-packing
effects are responsible for the observed differences in the solid
state. Because of the presence of the triple bond to carbon and
π bonding of the imido group to the metal, Cipso of the aryl
group must lie in the N-Mo-C plane. The aryl group points
toward the alkylidyne ligand, away from the phosphonium
cation, which is nestled into the NOO face of the tetrahedral
central core.
{Ph3PMe}{Mo(NAr)(CCMe3)[OCMe(CF3)2]2} is isoelec-
tronic with the known rhenium(VII) complex Re(NAr)(CCMe3)-
[OCMe(CF3)2]2.6 In the Re compound, the CR resonance is found
at 304.28 ppm (vs 300.75 ppm in the Mo species above) and
the isopropyl methyl groups appear as a single doublet resonance
at room temperature, consistent with facile rotation of the aryl
ring about the Nimido-Cipso bond on the NMR time scale. No
structural study of Re(NAr)(CCMe3)[OCMe(CF3)2]2 was carried
out.
The benzylidene phosphorane, Ph3PdCHPh, did not react
with Mo(NAr)(CHCMe3)[OCMe(CF3)2]2 at concentrations of
∼0.01 M in benzene-d6, even upon heating to 40 °C. Presumably
for steric reasons this phosphorane can neither deprotonate the
alkylidene readily nor create adducts through addition to the
metal, as described below.
Figure 1. POV-ray rendering (thermal ellipsoids at 50%) of one
of the two independent molecules of {Ph3PMe}{Mo(NAr)(CCMe3)-
[OCMe(CF3)2]2} in the unit cell. Hydrogen atoms are removed for
clarity. Molybdenum is shown in purple, oxygen in red, nitrogen
in blue, fluorine in green, and phosphorus in orange. Relevant bond
distances (Å) and angles (deg): Mo1-C1, 1.754(2); Mo1-N1,
1.813(2); Mo1-O1, 1.9838(18); Mo1-O2, 1.9763(18); C100-
Mo1, 3.566(3); Mo1-C1-C2, 168.2 (2); Mo1-N1-C23, 141.16-
(17); N1-Mo1-C1, 105.82(11).
The reaction of Mo(NAr)(CHCMe3)[OCMe(CF3)2]2 and
Me3PdCHPh in benzene-d6 was followed by NMR and shown
to give a mixture of two compounds initially (Scheme 1). The
main component of the mixture is an alkylidene-containing
species with a neopentylidene HR resonance at 11.65 ppm that
is coupled weakly to phosphorus (JPH ) 1.5 Hz). Only one
methyl resonance for the hexafluoro-tert-butyl group is observed,
which suggests that the molecule possesses mirror symmetry.
The imido aryl ring also shows free rotation, as judged by the
single doublet resonance for the methyl protons of the isopropyl
groups. These spectral features are all consistent with an adduct
in which the ylide is bound to the NOO face of the original
tetrahedral core. Base adducts of this type have been observed
in several instances,7 and some have been structurally character-
ized.8 Interestingly, the ylide coordinating to the Mo center is
no longer a benzylidene but rather a methylidene, as judged by
the doublet resonance at 2.48 ppm that integrates to two protons
(PCH2Ph). The minor component of the initial mixture shows
no alkylidene resonance. The minor species also possesses
mirror symmetry, and the methyl protons of the isopropyl groups
are broadened significantly. These features are consistent with
an alkylidyne anion-phosphonium cation ion pair (1′′) formed
by deprotonation of the alkylidene by the ylide (Scheme 1,
Figure S1). The mechanism of formation of the methylene
species is not known, although formation of {Me3PCH2Ph}-
{Mo(NAr)(CCMe3)[OCMe(CF3)2]2} followed by abstraction of
a methyl proton in the phosphonium salt by the alkylidyne
R carbon atom is one attractive possibility.
Table 1. Crystallographic Data and
Refinement Parameters for 1
empirical formula
fw
C44H50F12MoNO2P
979.76 g/mol
temperature
wavelength
cryst syst
100(2) K
0.71073 Å
monoclinic
space group
unit cell dimens
P21/c
a ) 25.3522(10) Å, R ) 90°
b ) 17.7046(7) Å, â ) 97.2830(10)°
c ) 20.2127(8) Å, γ ) 90°
8999.3(6) Å3
volume
Z
8
density (calcd)
absorp coeff
F(000)
cryst size
θ range for data collection
index ranges
1.446 g/cm3
0.413 mm-1
4016
0.30 × 0.25 × 0.10 mm3
1.67 to 29.57°
-34 e h e 35,
-24 e k e 24,
-28 e l e 27
198 822
25 247 [R(int) ) 0.0558]
100%
semiempirical from equivalents
0.9598 and 0.8860
full-matrix least-squares on F2
25 247/2270/1299
no. of reflns collected
no. of indep reflns
completeness to θ ) 29.57°
absorp corr
max. and min. transmn
refinement method
no. of data/restraints/
params
Upon standing at room temperature for several hours, the
reaction evolves into a new mixture of products. The major
component is now the alkylidyne anion (>70%), and the initial
adduct is gone. The minor component is again an alkylidene-
containing species with the neopentylidene HR resonance at
12.71 ppm (JPH coupling could not be resolved). The spectrum
is consistent with the lack of any symmetry element, suggesting
goodness-of-fit on F2
final R indices [I > 2σ(I)]
R indices (all data)
largest diff peak and hole
1.031
R1 ) 0.0374, wR2 ) 0.0841
R1 ) 0.0549, wR2 ) 0.0928
0.844 and -0.502 e‚Å-3
latter (compare 3.566(3) versus 4.054(3) Å for the distance from
the carbon atom of the methyl group of the phosphonium cation
to the molybdenum center). Only one species is observed in
solution, and the low barrier to Nimido-Cipso bond rotation in
arene solvents suggests that the potential energy surface for
flexing of the Mo-Nimido-Cipso angle may be quite flat and
(6) Schrock, R. R.; Weinstock, I. A.; Horton, A. D.; Liu, A. H.; Schofield,
M. H. J. Am. Chem. Soc. 1988, 110, 2686.
(7) Schrock, R. R.; Crowe, W. E.; Bazan, G. C.; DiMare, M.; O’Regan,
M. B.; Schofield, M. H. Organometallics 1991, 10, 1832.
(8) (a) Schrock, R. R.; Gabert, A. J.; Singh, R.; Hock, A. S. Organo-
metallics 2005, 24, 5058. (b) Adamchuk, J.; Schrock, R. R.; Tonzetich, Z.
J.; Mu¨ller, P. Organometallics 2006, 25, 2364.

Reaction of Phosphoranes
Organometallics, Vol. 25, No. 18, 2006 4303
Scheme 1. Summary of Observed Reaction Products between Mo(NAr)(CHCMe3)[OCMe(CF3)2]2 and Me3PdCHPh
that the minor species is an adduct in which the ylide is bound
to the CNO face of the original tetrahedral MoCNOO core. The
spectrum shows a doublet resonance at 1.92 ppm with a relative
integration of two, demonstrating that the ylide is coordinating
through a methylidene carbon as above. It remains a possibility
that the NOO adduct is the initial product of reaction between
the benzylidene ylide and that both the alkylidyne anion and
the CNO adduct form from this initial complex (Scheme 1,
Figure S1). A variable-temperature NMR study between 20 and
80 °C revealed no exchange between the alkylidyne anion and
the ylide (CNO) adduct. Preparative-scale reactions in toluene
yielded the same mixture of compounds even after recrystalli-
zation from toluene.
The reaction between Me3PdCH2 and Mo(NAr)(CHCMe3)-
[OCMe(CF3)2]2 produced a crystalline product for which proton
and phosphorus NMR spectra suggest it to be a mixture of the
NOO (10%) adduct, the CNO (26%) adduct, and the alkylidyne
anion (64%).
The reactivity of 1 has been explored briefly. Treatment of 1
with [Me3O]BF4 in methylene chloride generates the new
alkylidyne species Mo(CCMe3)[N(Me)Ar][OCMe(CF3)2]2 (2,
Scheme 2). This new species is a pentane-soluble, colorless
solid, consistent with an alkylidyne amido bis-alkoxide complex
formed by methylation at nitrogen.9 The alkylidyne carbon
resonance appears at 319.47 ppm in benzene-d6 and the iso-
propyl methyl groups appear as well-resolved doublets in the
1H NMR spectrum, consistent with locked rotation about the
Nimido-Cipso bond. Treatment of the alkylidyne anion with Me3-
SiOSO2CF3 yields the related species Mo(CCMe3)[N(SiMe3)-
Ar][OCMe(CF3)2]2 (3). This compound is also colorless and
displays a resonance for CR at 322.79 ppm (benzene-d6). Both
reactions appear to be quantitative by NMR; however isolated
yields were only moderate due to the high solubility of the
alkylidyne complexes in pentane.
The net result of protonation of {Ph3PMe}{Mo(NAr)-
(CCMe3)[OCMe(CF3)2]2} with [HNMe2Ph]Cl or [Et3NH]Cl is
formation of Mo(NAr)(CHCMe3)[OCMe(CF3)2]2, as judged by
1H NMR. In the case of [HNMe2Ph]Cl, the dimethylaniline
byproduct does not coordinate to the metal and Mo(NAr)-
(CHCMe3)[OCMe(CF3)2]2 is formed cleanly (Scheme 2). With
[Et3NH]Cl, the triethylamine appears to coordinate weakly to
the metal, giving rise to two observed alkylidene species. The
reaction between {Ph3PMe}{Mo(NAr)(CCMe3)[OCMe(CF3)2]2}
and [H(OEt2)2]B[3,5-(CF3)2C6H3]4 appeared to be instantaneous
in benzene-d6, as judged by immediate precipitation of [Ph3-
PMe]B[3,5-(CF3)2C6H3]4 as a brown oil. Spectra indicated that
the major species formed was again Mo(NAr)(CHCMe3)-
[OCMe(CF3)2]2, though several resonances in the region of
8-9 ppm suggest that Mo(NHAr) species are present.
Reaction of 1 with carbon dioxide was rapid upon warming
the reaction mixture from 77 K to room temperature; the solution
decolorized and a white precipitate formed. NMR examination
of the precipitate in methylene chloride-d2 showed it to be the
κ2-carbamate complex (4, Scheme 2). The IR spectrum in
methylene chloride shows a strong peak at 1658 cm-1, consistent
with the CO stretch of the carbamate ligand.10 Heating the
(9) Schrock, R. R.; Jamieson, J. Y.; Araujo, J. P.; Bonitatebus, P. J.;
Sinha, A.; Lopez, L. P. H. J. Organomet. Chem. 2003, 684, 56.
(10) Glueck, D. S.; Wu, J.; Hollander, F. J.; Bergman, R. G. J. Am. Chem.
Soc. 1991, 113, 2041.

4304 Organometallics, Vol. 25, No. 18, 2006
Scheme 2. Reaction of {Ph3PMe{Mo(NAr)(CCMe3)[OCMe(CF3)2]2} with Electrophiles
Tonzetich et al.
carbamate did not result in extrusion of aryl isocyante, but rather
decomposition to unidentifiable products.
phylidene, has been a troublesome side reaction whenever
alkoxides or diolates are added to Mo(NAr)(CHR)(OTf)2(dme)
(R ) CMe3 or CMe2Ph) species.14 (This approach has been the
standard method of preparing bis-alkoxide catalysts such as Mo-
(NAr)(CHCMe3)[OCMe(CF3)2]2.) Phosphorus ylides have been
employed as bases in early experiments; for example, Me3Pd
CH2 was employed as a base in order to cleanly deprotonate
[Cp2TaMe2]BF4 to yield Cp2TaMe(CH2).15 For all of these
reasons, therefore, we did not find deprotonation of the neo-
pentylidene ligand in Mo(NAr)(CHCMe3)[OCMe(CF3)2]2 to be
especially surprising. Nevertheless unambiguous examples are
relatively rare, and the example described here is first to our
knowledge of a structurally characterized four-coordinate high
oxidation state imido alkylidyne species. These species represent
isolable versions of intermediates thought to be present along
the proton transfer pathway from Mo(NR)(CHR′)(OR′′)2 to Mo-
(NHR)(CR′)(OR′′)2.14
Addition of several equivalents of 3-hexyne to {Ph3PMe}-
{Mo(NAr)(CCMe3)[OCMe(CF3)2]2} led to no reaction at room
temperature after several days. In contrast, Re(NAr)(CCMe3)-
[OCMe(CF3)2]2 has been reported to react with 3-hexyne to give
metallacyclobutadiene species.6 The more electron-rich nature
of the alkylidyne anion may disfavor alkyne binding.
Discussion
Deprotonation of a high oxidation state alkylidene was first
demonstrated in a reaction between Ta(CHCMe3)(CH2CMe3)3
and LiBu.11 Dehydrohalogenation of W(NPh)(CHCMe3)(PEt3)2-
Cl2 with Ph3PdCH2 has been shown to lead to W(NPh)-
(CCMe3)(PEt3)2Cl.12 Addition of HCl to this species regenerated
W(NPh)(CHCMe3)(PEt3)2Cl2. Moving a proton from an amido
nitrogen to a neopentylidyne R carbon atom was the first general
method of preparing imido alkylidene complexes of tungsten,13
while the reverse, deprotonation of a neopentylidene or neo-
On the basis of the results described here, it would seem that
regeneration of a metathetically active alkylidene complex
(13) Schaverien, C. J.; Dewan, J. C.; Schrock, R. R. J. Am. Chem. Soc.
1986, 108, 2771.
(14) Schrock, R. R.; Jamieson, J. Y.; Araujo, J. P.; Bonitatebus, P. J.,
Jr.; Sinha, A.; Lopez, L.; Pia, H. J. Organomet. Chem. 2003, 684, 56.
(15) Schrock, R. R.; Sharp, P. R. J. Am. Chem. Soc. 1978, 100, 2389.
(11) Guggenberger, L. J.; Schrock, R. R. J. Am. Chem. Soc. 1975, 97,
2935.
(12) Rocklage, S. M.; Schrock, R. R.; Churchill, M. R.; Wasserman, H.
J. Organometallics 1982, 1, 1332.

Reaction of Phosphoranes
Organometallics, Vol. 25, No. 18, 2006 4305
2 ArH), 7.02 (m, 10 ArH), 6.89 (m, 6 ArH), 3.79 (sep, 2 CHMe2),
3.10 (d, JPH ) 12.6 Hz, 3 PMe), 2.07 (s, 6 Me-RF6), 1.8-1.0 (v
br, 12 CHMe2), 1.29 (s, 9 CMe3); 13C{1H} (125 MHz) δ 300.75
(MotCR), 163.70, 137.99, 135.14 (d, JCP ) 3.0 Hz), 133.20 (d,
JCP ) 10.8 Hz), 130.69 (d, JCP ) 12.3 Hz), 126.28 (q, JCF ) 288
through transfer of an alkylidene from an alkylidene phospho-
rane could be problematic. From this point of view, the fact
that Ph3PdCHPh did not deprotonate Mo(NAr)(CHCMe3)-
[OCMe(CF3)2]2 is one of the more interesting results. However,
whether Ph3PdCHPh could serve as a source of a benzylidene
ligand in a reaction with some “Mo(NAr)[OCMe(CF3)2]2”
species to yield Mo(NAr)(CHPh)[OCMe(CF3)2]2 remains un-
known. We hope to explore such possibilities in future studies.
Hz), 125.94 (q, JCF ) 289 Hz), 122.41, 120.30, 119.45 (d, JCP
)
89.2 Hz), 80.08 (sep, Cquat-RF6), 52.63, 32.29, 28.34, 24.2 (br,
CHMe2), 21.81, 9.91 (d, JCP ) 56.9 Hz); 31P{1H} (121 MHz) δ
22.29; 19F (282 MHz) δ -77.52 (q), -78.15 (q). Anal. Calcd for
C44H50F12MoNO2P: C, 53.94; H, 5.14; N, 1.43. Found: C, 54.08;
H, 5.17; N, 1.36.
Experimental Section
General Comments. All manipulations were performed in oven-
dried (200 °C) glassware under an atmosphere of nitrogen in a
Vacuum Atmospheres glovebox. HPLC-grade toluene, pentane, and
methylene chloride were purified by passage through an alumina
column and stored over 4 Å Linde-type molecular sieves prior to
use. Benzene-d6 was dried over sodium benzophenone ketyl and
distilled prior to use. Methylene chloride-d2 was dried over CaH2,
vacuum distilled, and stored over molecular sieves prior to use.
NMR spectra were recorded on a Varian Mercury or Varian Inova
spectrometer operating at 300 or 500 MHz (1H), respectively.
{Ph3PMe}{Mo(NAr)(CCMe2Ph)[OCMe(CF3)2]2}, 1′. A J-Young
type NMR tube was charged with 38.5 mg (50.3 µmol) of Mo-
(NAr)(CHCMe2Ph)[OCMe(CF3)2]2 and 14.2 mg (51.4 µmol) of
Ph3PdCH2. Approximately 0.7 mL of C6D6 was added to the solids,
producing an orange solution. 1H NMR observation of the mixture
indicated that the desired complex was present in ∼90% along with
a minor species that was not identified completely but appeared to
be a phosphorane adduct of the alkylidene. The C6D6 was removed
in vacuo and the residue dissolved in a minimal amount of 3:1
pentane/toluene. The solution was set aside at -25 °C for several
days, during which time the complex precipitated as 33.2 mg (63%)
of orange needles: NMR (C6D6) 1H (300 MHz) δ 7.74 (d, 2 ArH),
7.37 (d, 2 ArH), 7.23 (t, 2 ArH), 7.13 (t, 1 ArH), 6.99 (m, 10 ArH),
6.87 (m, 6 ArH), 3.80 (sep, 2 CHMe2), 3.08 (d, JHP ) 12.6 Hz,
3 PMe), 1.80 (s, 6 Me-RF6), 1.72 (s, 6 CMe2Ph), 1.56 (v br,
1
Spectra are referenced to the residual H/13C peaks of the solvent
(1H: C6D6, 7.16; CD2Cl2, 5.32; 13C: C6D6, 128.39; CD2Cl2, 54.00)
and are listed in ppm relative to tetramethylsilane. 19F and 31P NMR
were referenced externally to fluorobenzene (δ -113.15 ppm
upfield of CFCl3) and 80% H3PO4 (δ 0.00 ppm), respectively.
Combustion analyses were performed by H. Kolbe Mikroanalitis-
ches Laboratorium, Mu¨lheim an der Ruhr, Germany.
6 CHMe2), 1.09 (v br, 6 CHMe2); 31P{1H} (121 MHz) δ 21.70; 19
F
(282 MHz) δ -77.58 (q), -78.12 (q). Anal. Calcd for C49H52F12-
MoNO2P: C, 56.59; H, 5.03; N, 1.34. Found: C, 56.36; H, 5.12;
N, 1.29.
Mo(NAr)(CHCMe2R)[OCMe(CF3)2]2 (R ) Me and Ph) were
prepared according to published procedures. Me3PdCHPh, Ph3Pd
CHPh, and Me3PdCH2 were prepared by addition of n-BuLi to a
toluene suspension of the corresponding phosphonium halide salt,
followed by filtration and crystallization from pentane or toluene
(Me3PdCHPh and Ph3PdCHPh) or distillation (Me3PdCH2).
Ph3PdCH2 was prepared with LiN(SiMe3)2 in a similar fashion
and crystallized from toluene. [Me3O]BF4, Me3SiOSO2CF3, and
CO2 were purchased from commercial vendors and used as received.
Crystallography. Low-temperature diffraction data were col-
lected on a Siemens Platform three-circle diffractometer coupled
to a Bruker-AXS Smart Apex CCD detector with graphite-
monochromated Mo KR radiation (λ ) 0.71073 Å), performing θ-
and ω-scans. The structure was solved by direct methods using
SHELXS16 and refined against F2 on all data by full-matrix least
squares with SHELXL-97.17 All non-hydrogen atoms were refined
anisotropically. All hydrogen atoms were included into the model
at geometrically calculated positions and refined using a riding
model. Two disordered CMe(CF3)2 groups in one of the two
crystallographically independent molecules were refined with the
help of similarity restraints on 1-2 and 1-3 distances and dis-
placement parameters as well as rigid bond restraints for anisotropic
displacement parameters. Similar ADP restraints were also applied
to all atoms of the two [Ph3PMe]+ ions.
Mo(CCMe3)[N(Me)Ar][OCMe(CF3)2]2, 2. A flask was charged
with 0.147 g (0.15 mmol) of {Ph3PMe}{Mo(NAr)(CCMe3)[OCMe-
(CF3)2]2} and 8 mL of methylene chloride. The solution was cooled
to -25 °C, at which point 0.029 g (0.20 mmol) of [Me3O]BF4 was
added as a solid. The mixture was stirred at room temperature for
45 min, during which time the solution became pale yellow. All
volatiles were removed in vacuo, and the residue was extracted
with pentane. The pentane extract was filtered through Celite and
the solution volume reduced to ∼1 mL in vacuo. Slow cooling of
the pentane solution at -25 °C afforded 0.067 g (65%) of pale
1
yellow to colorless crystals: NMR (C6D6) H (500 MHz) δ 7.03
(m, 3 ArH), 3.28 (s, 3 NMe), 3.02 (sep, 2 CHMe2), 1.69 (s, 6 Me-
RF6), 1.26 (d, 6 CHMe2), 1.03 (d, 6 CHMe2), 0.66 (s, 9 CMe3);
13C{1H} (125 MHz) δ 319.47 (MotCR), 157.62, 142.07, 127.94,
124.61 (q, JCF ) 286 Hz, CF3), 124.41, 124.21 (q, JCF ) 287 Hz,
CF3), 81.59 (sep, JCF ) 29.4 Hz, Cquat-RF6), 54.99, 45.25 (NMe),
29.97, 28.05, 26.73, 23.79, 20.79; 19F (470 MHz) δ -78.26 (q),
-78.97 (q). Anal. Calcd for C26H35F12MoNO2: C, 43.52; H, 4.92;
N, 1.95. Found: C, 43.64; H, 5.05; N, 1.87.
Mo(CCMe3)[N(SiMe3)Ar][OCMe(CF3)2]2, 3. A flask was
charged with 0.174 g (0.178 mmol) of {Ph3PMe}{Mo(NAr)-
(CCMe3)[OCMe(CF3)2]2} and 8 mL of toluene and chilled to -25
°C. To the cold solution was added 40 uL (0.20 mmol) of Me3-
SiOSO2CF3, at which point the solution became pale yellow and
cloudy. The reaction was stirred at room temperature for 15 min,
and all volatiles were removed in vacuo. The residue was extracted
into pentane and filtered through Celite. The solvent volume was
reduced to ∼1 mL in vacuo and set aside at -25 °C. The product
crystallized as 0.0503 g (39%) of pale yellow to colorless cubes in
{Ph3PMe}{Mo(NAr)(CCMe3)[OCMe(CF3)2]2}, 1. A round-
bottom flask was charged with 1.035 g (1.47 mmol) of Mo(NAr)-
(CHCMe3)[OCMe(CF3)2]2 and 25 mL of toluene. To the stirring
yellow solution was added 0.410 g (1.48 mmol) of Ph3PdCH2 as
a solid in one portion, at which point the reaction solution became
orange-red. The mixture was stirred for 90 min at room temperature,
and the volatiles were removed in vacuo. The residue was dissolved
in toluene, and pentane was added until the solution became turbid.
The solution was set aside at -25 °C for 18 h, during which time
1.093 g (76%) of orange microcrystals formed. Crystals suitable
for X-ray diffraction were grown by slow cooling of a saturated
1
two crops: NMR (C6D6) H (500 MHz) δ 7.06 (m, 3 ArH), 3.09
(sep, 2 CHMe2), 1.71 (s, 6 Me-RF6), 1.32 (d, 6 CHMe2), 1.13 (d,
6 CHMe2), 0.65 (s, 9 CMe3), 0.23 (s, 9 Me3Si); 13C{1H} (125 MHz)
δ 322.79 (MotCR), 156.76, 140.93, 126.47, 124.52, 124.50 (q,
JCF ) 287 Hz, CF3), 124.15 (q, JCF ) 287 Hz, CF3), 82.19 (sep,
JCF ) 29.7 Hz, Cquat-RF6), 56.05, 30.41, 28.27, 25.81, 25.68, 20.44,
0.98 (SiMe3); 19F (470 MHz) δ -77.14 (q), -78.55 (q). Anal. Calcd
1
toluene/pentane solution: NMR (C6D6) H (500 MHz) δ 7.33 (d,
(16) Sheldrick, G. M. Acta Crystallogr. A 1990, 46, 467.
(17) Sheldrick, G. M. SHELXL 97; Universita¨t Go¨ttingen: Go¨ttingen,
Germany, 1997.

4306 Organometallics, Vol. 25, No. 18, 2006
Tonzetich et al.
for C28H41F12MoNO2Si: C, 43.36; H, 5.33; N, 1.81. Found: C,
43.28; H, 5.30; N, 1.77.
JCF ) 287 Hz), 123.01, 120.12 (d, JCP ) 88.3 Hz), 81.21 (sep, JCF
) 28.4 Hz), 51.07, 29.83, 28.84, 25.22, 22.70, 20.19, 9.29 (JCP
)
{Ph3PMe}{Mo(CCMe3)[κ2-OC(O)NAr][OCMe(CF3)2]2}, 4. A
round-bottom flask was charged with 0.185 g (0.189 mmol) of {Ph3-
PMe}{Mo(NAr)(CCMe3)[OCMe(CF3)2]2} and 10 mL of toluene.
To the flask was connected a needle valve. The solution was
degassed by two consecutive freeze-pump-thaw cycles. The
degassed solution was then exposed to 1 atm of CO2 for 10 min
while stirring and warming from the melting point of the solvent
to room temperature. The flask was sealed and allowed to stir for
an additional 20 min at room temperature, during which time the
solution turned from orange to pale yellow with formation of a
white precipitate. All volatiles were removed in vacuo, and the
residue was triturated in a 10:1 mixture of pentane to toluene,
causing formation of a white solid. The solid was collected by
filtration, yielding 0.177 g (91%) of a white powder: NMR (CD2-
57.5 Hz); 31P{1H} (121 MHz) δ 22.58; 19F (470 MHz) δ -78.32
(q), -78.60 (q); IR (CH2Cl2) 1658 cm-1 (νCO). Anal. Calcd for
C45H50F12MoNO4P: C, 52.79; H, 4.92; N, 1.37. Found: C, 52.64;
H, 5.08; N, 1.34.
Acknowledgment. R.R.S. thanks the National Science
Foundation (CHE-0138495) for supporting this research. Z.J.T.
also acknowledges the Alan Davison Fellowship Fund for
financial support for one semester and Rojendra Singh for a
generous donation of Mo(NAr)(CHCMe2Ph)[OCMe(CF3)2]2.
Supporting Information Available: Crystallographic details,
fully labeled thermal ellipsoid diagrams for both molecules of {Ph3-
PMe}{Mo(NAr)(CCMe)[OCMe(CF3)2]2, and crystallographic in-
formation files. This material is available free of charge via the
Internet at http://pubs.acs.org. Data for the X-ray structure is also
available to the public at http://www.reciprocalnet.org/(number
06013).
1
Cl2) H (300 MHz) δ 7.72 (m, 15 ArH), 7.14 (m, 3 ArH), 3.08
(sep, 2 CHMe2), 3.00 (d, JPH ) 13.2 Hz, PMe), 1.88 (s, 6 Me-
RF6), 1.21 (d, 6 CHMe2), 1.03 (d, 6 CHMe2), 0.70 (s, 9 CMe3);
13C{1H} (125 MHz) δ 309.25 (MotCR), 165.54 (CdO), 151.673,
143.81, 135.32 (d, JCP ) 2.3 Hz), 133.87 (d, JCP ) 10.7 Hz), 130.70
(d, JCP ) 13.0 Hz), 126.17, 124.62 (q, JCF ) 288 Hz), 124.37 (q,
OM060501E