High oxidation state molybdenum imido heteroatom-substituted alkylidene complexes

Article abstract of DOI:10.1021/om400584f

Reactions between Mo(NAr)(CHR)(Me₂Pyr)(OTPP) (Ar = 2,6-i-Pr ₂C₆H₃, R = H or CHCMe₂Ph, Me ₂Pyr = 2,5-dimethylpyrrolide, OTPP = O-2,3,5,6-Ph₄C ₆H) and CH₂=CHX where X = B(pin), SiMe₃, N-carbazolyl, N-pyrrolidinonyl, PPh₂, OPr, or SPh lead to Mo(NAr)(CHX)(Me₂Pyr)(OTPP) complexes in good yield. All have been characterized through X-ray studies (as an acetonitrile adduct in the case of X = PPh₂). The efficiencies of metathesis reactions initiated by Mo(NAr)(CHX)(Me₂Pyr)(OTPP) complexes can be rationalized on the basis of steric factors; electronic differences imposed as a consequence of X being bound to the alkylidene carbon do not seem to play a major role. Side reactions that promote catalyst decomposition do not appear to be a serious limitation for Mo=CHX species.

Full text of DOI:10.1021/om400584f

Article
pubs.acs.org/Organometallics
High Oxidation State Molybdenum Imido Heteroatom-Substituted
Alkylidene Complexes
Erik M. Townsend,† Stefan M. Kilyanek,† Richard R. Schrock,*,† Peter Muller,† Stacey J. Smith,†
̈
and Amir H. Hoveyda‡
†Department of Chemistry 6-331, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
‡Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, United States
S
* Supporting Information
ABSTRACT: Reactions between Mo(NAr)(CHR)(Me2Pyr)(OTPP)
(Ar = 2,6-i-Pr2C6H3, R = H or CHCMe2Ph, Me2Pyr = 2,5-
dimethylpyrrolide, OTPP = O-2,3,5,6-Ph4C6H) and CH2CHX
where X = B(pin), SiMe3, N-carbazolyl, N-pyrrolidinonyl, PPh2, OPr,
or SPh lead to Mo(NAr)(CHX)(Me2Pyr)(OTPP) complexes in good
yield. All have been characterized through X-ray studies (as an
acetonitrile adduct in the case of X = PPh2). The efficiencies of
metathesis reactions initiated by Mo(NAr)(CHX)(Me2Pyr)(OTPP)
complexes can be rationalized on the basis of steric factors; electronic
differences imposed as a consequence of X being bound to the
alkylidene carbon do not seem to play a major role. Side reactions that
promote catalyst decomposition do not appear to be a serious
limitation for MoCHX species.
the last several years, especially Z-selective reactions,5−7 and
because the OTPP ligand lowers the solubility and therefore
INTRODUCTION
The vast majority of high oxidation state imido alkylidene
■
facilitates isolation of what can otherwise be highly soluble
complexes of Mo and W contain CHX alkylidenes in which X is
carbon-based or, rarely, X = H.1 A few MCHX complexes are
MAP compounds. (An improved synthesis of 2,3,5,6-
known in which X is based on Si1 or Ge.1,2 However, to our
tetraphenylphenol (HOTPP) is described in the Supporting
Information.)
knowledge no complexes have been described in which X is
based on a heteroatom (B, N, O, S, P, halide, etc.). The only
In order to increase the simplicity of a reaction between a
Mo alkylidene complex and CH2CHX (eq 1), we prepared
report of MCHX derivatives among high oxidation state
alkylidene complexes concerns Re derivatives of the type Re(C-
t-Bu)(CHX)[OCMe(CF3)2](THF)2 where X is OR, SR, or
pyrrolidinonyl.3 In contrast, several RuCHX derivatives have
been described in which X is based on O, S, or N and for which
selected reactions with olefins have been explored.4a Also,
several Ru-catalyzed metatheses involving enol ethers have
been published.4b−e As olefin metathesis investigations evolve
to include CH2CHX derivatives where X is not carbon-based
(for example, Z-selective cross-metathesis reactions where X =
OR5 or B(pinacolate)6), it becomes more important to
establish what Mo and W MCHX complexes can be
prepared and how they react with ordinary olefins. Studies of
high oxidation state MCHX compounds also would help
clarify to what extent the electronic structure and reactivity of
the MoC bond are influenced by the presence of a
heteroatom substituent.
Mo(NAr)(CH2)(Me2Pyr)(OTPP) (1b) in 79% yield, the Mo
analogue of the tungsten complex, W(NAr)(CH2)(Me2Pyr)-
(OTPP),1c by treating Mo(NAr)(CHCMe2Ph)(Me2Pyr)-
(OTPP)9 (1a) with ethylene. The proton NMR spectrum of
1b in C6D6 contains the methylidene proton resonances at
11.77 and 11.58 ppm (JHH = 5 Hz).
Both 1a and 1b react cleanly with CH2CHB(pin) to give
RESULTS AND DISCUSSION
■
Mo(NAr)[CHB(pin)](Me2Pyr)(OTPP) (2a), which is ob-
We targeted Mo(NAr)(CHX)(Me2Pyr)(OTPP) complexes
(Ar = 2,6-i-Pr2C6H3, Me2Pyr = 2,5-dimethylpyrrolide, OTPP
= O-2,3,5,6-Ph4C6H), in part because monoalkoxide pyrrolide
(MAP) complexes have produced new and interesting results in
Received: June 20, 2013
© XXXX American Chemical Society
A
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tained as an orange solid in 83% yield. An X-ray study of 2a
(Figure 1) reveals that it contains an anti alkylidene ligand (i.e.,
calculations or the Mo1···O2 distance (2.837 Å) that there is
any significant electronic interaction between Mo1 and O2. A
few structurally characterized 16e anti alkylidene complexes
(i.e., five-coordinate intramolecular or intermolecular adducts)
of this general type are known in which the M−C−C angle is
135−150°.1,10
The proton NMR spectrum of 2a (Figure 3) at 20 °C reveals
broad alkylidene α proton resonances characteristic of
Figure 1. Thermal ellipsoid drawing of 2a from XRD study.
the B(pin) substituent points away from the imido ligand) with
a MoC bond length of 1.8825(1) Å and a MoC−B bond
angle of 106.19(7)° (Table 1). These values should be
Table 1. Selected MoC Bond Lengths (Å) and MoC−X
Bond Angles (deg) for Mo(NAr)(CHX)(Me2Pyr)(OTPP)
Complexes
1
Figure 3. Temperature-dependent H NMR spectra of 2a in toluene-
d8 in the alkylidene proton region.
cmpd
X
MoC
C−X
MoC−X
a
1a
2a
2b
2c
2d
2e′
2f
CMe2Ph
1.881(5)
1.518(7)
145.2(4)
bc
,
B(pin)
SiMe3
1.8825(1)
1.875(2)
1.5525(16)
1.862(1)
106.19(7)
139.96(8)
143.60(10)
117.47(7)
126.1(1)
interconverting syn and anti isomers. Variable-temperature
NMR studies (Figure 3) show one alkylidene resonance at high
temperature and deconvolution and sharpening of two
resonances at low temperature. Modeling the temperature
dependence yields values of ΔH⧧ = 8.7(3) kcal/mol and ΔS⧧ =
0.02 kcal/(mol K); at 298 K the rate of interconversion is 28
s−1. Therefore, both syn and anti isomers are accessible on a
subsecond time scale in 2a (at 298 K) and have approximately
the same energies. The relatively high rate of alkylidene
rotation is consistent with a Mo(+)−CB(−) resonance form,
although the π component of the MoC bond is only slightly
decreased according to NBO calculations (vide supra).
The reaction between 1b and CH2CHSiMe3 yields
Mo(NAr)(CHSiMe3)(Me2Pyr)(OTPP) (2b) as an orange
solid in 47% yield. Compound 2b is a single (syn) isomer in
the solid state (see Table 1 and SI) and in solution (1H NMR
in C6D6). Syn and anti isomers of Mo(NAr)(CHSiMe3)(OAr)2
and W(NAr)(CHSiMe3)(OAr)2 have been observed in
solution11 and have been shown to interconvert readily at
room temperature with a relatively low barrier (not
quantified).12 Since the amount of anti 2b in solution is
small, we cannot know whether syn and anti isomers of 2b also
interconvert readily.
d
Carbaz
1.9140(13)
1.9578(11)
1.904(2)
1.3797(16)
1.3968(12)
1.812(2)
ce
,
Pyrrol
f
PPh2
OPr
SPh
1.921(3)
1.343(4)
142.7(3)
2g
1.9112(15)
1.7179(16)
130.20(9)
a
b
c
d
See ref 6. B(pin) = B(pinacolate). Anti configuration. Carbaz = N-
carbazolyl. Pyrrol = N-pyrrolidinonyl. Acetonitrile adduct.
e
f
compared with those for Mo(NAr)(CHCMe2Ph)(Me2Pyr)-
(OTPP) (1a, Table 1).6 NBO calculations reveal that the
empty p orbital on B is conjugated with the MoC π orbital
(Figure 2), but the contribution from the B orbital (99% p) is
only 3.7% of the MoC π natural localized molecular orbital
(NLMO). There is no evidence from either the NBO
The reaction between 1b and CH2CH(Carbaz) (Carbaz =
N-carbazolyl) yields Mo(NAr)[CH(Carbaz)](Me2Pyr)-
(OTPP) (2c) as an orange solid in 81% yield. Compound 2c
is a single syn isomer in the solid state (see Table 1) and in
solution (JCH = 134 Hz; 1H NMR in C6D6). The structure of 2c
(Figure 4) is consistent with previously characterized MAP
complexes.
The reaction between 1b and CH2CH(Pyrrol) (Pyrrol =
N-pyrrolidinonyl) yields Mo(NAr)[CH(Pyrrol)](Me2Pyr)-
(OTPP) (2d) as a pink solid in 81% yield. Compound 2d is
approximately a trigonal bipyramid (τ = 0.70)13 in which the
Figure 2. Overlap of the filled MoC π bond and the empty B p
orbital in 2a (preorthogonalized NBOs at the 0.02 isovalue). H atoms
and OTPP phenyl rings have been omitted for clarity.
B
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Figure 4. Thermal ellipsoid drawing of 2c from XRD study.
Figure 6. Thermal ellipsoid drawing of 2e′ from XRD study.
carbonyl group is coordinated to the metal in an apical position
(Figure 5). The alkylidene is anti with JCH = 166 Hz; this
Figure 5. Thermal ellipsoid drawing of 2d from XRD study.
Figure 7. Temperature-dependent 1H NMR spectra of 2e in the
alkylidene proton region in toluene-d8.
2e (the downfield doublet). Small (including zero)2 JHP values
in general are not unusual.15
configuration is expected on the basis of similar structures being
observed for Re (JCH = 173 Hz)3 and Ru4 complexes. The
MoC bond distance in 2d is longer than MoC bond
distances in Table 1, probably as a consequence of the anti
orientation of the alkylidene along with the fact that 2d is five-
coordinate. However, CN multiple-bond character (and a
consequent increase in the MoC bond length) is also
suggested through NBO calculations.
The 1H NMR spectrum of 2e′ (in toluene-d8 or C6D6; Figure
8) at 20 °C is virtually the same as the corresponding 1H NMR
spectrum of 2e (Figure 7), consistent with acetonitrile not
being bound strongly to the metal in solution at room
temperature under these conditions. The temperature-depend-
The reaction between 1b and CH2CHPPh2 yields
Mo(NAr)(CHPPh2)(Me2Pyr)(OTPP) (2e) as a red solid in
63% yield. Crystals were isolated as an orange acetonitrile
adduct of 2e (2e′) in 79% yield. The X-ray crystal structure of
2e′ is shown in Figure 6. Compound 2e′ is approximately a
square pyramid (τ = 0.20) with a syn orientation of the
alkylidene in the apical position and an acetonitrile coordinated
in a basal position trans to the pyrrolide. The MoC distance
and MoC−P angle are normal, and the phosphorus is
essentially pyramidal. NBO calculations reveal little to no
contribution of the phosphorus lone pair to the MoC π
bond, which is reasonable considering that the phosphorus lone
pair is predominantly of s character and the reduced capacity of
heavier main group elements to form multiple bonds to
carbon.14 In solution, 2e is a mixture of syn and anti isomers, as
judged from its temperature-dependent proton NMR spectrum
(Figure 7). The constant for coupling of the alkylidene proton
to phosphorus in 2e (the upfield resonance with JCH = 130 Hz)
is essentially zero, but approximately 5 Hz in the anti analog of
Figure 8. Temperature-dependent 1H NMR spectra of 2e′ (13 mM in
toluene-d8) in the alkylidene proton region in the presence of ∼1.5
equivalents of MeCN.
C
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ent NMR spectrum of 2e′ in the presence of ∼1.5 additional
equivalents of MeCN (2.5 total MeCN per Mo) reveals similar
coalescence behavior upon heating to the spectrum of 2e. Upon
cooling the sample, however, it appears that acetonitrile binds
weakly to the syn isomer, as judged by a strong downfield shift
of the syn alkylidene resonance at low temperatures (Figure 8).
In contrast, the alkylidene proton of the anti isomer is relatively
unaffected at low temperatures (Figure 8 versus Figure 7). We
attribute lack of binding of acetonitrile to the anti isomer to
donation of the phosphorus electron pair to the σ* component
of the MoN bond in anti-2e, which is the orbital that receives
electron density in an agostic CHα interaction in a typical syn
alkylidene isomer.16
The reaction between 1a or 1b and CH2CHOPr yields
Mo(NAr)(CHOPr)(Me2Pyr)(OTPP) (2f) as an orange solid
in 51% isolated yield. Its proton NMR spectrum at 22 °C shows
a single alkylidene resonance with JCH = 140 Hz, which should
be compared with JCH = 135 Hz for the syn isomer of Re(C-t-
Bu)(CHOEt)[OCMe(CF3)2](THF)2 and 163 Hz for the anti
isomer of Re(C-t-Bu)(CHOEt)[OCMe(CF3)2](THF)2 in
solution.3 An X-ray study confirms that 2f is a syn isomer in
the solid state (Figure 9) with a MoC1 bond that is slightly
Figure 10. NLMO of the O lone pair (0.02 isovalue) showing an O
lone pair overlapping with the MoC π antibonding orbital in 2f. H
atoms and the OTPP phenyl rings have been omitted for clarity.
Figure 11. Thermal ellipsoid drawing of 2g from XRD study.
Figure 9. Thermal ellipsoid drawing of 2f from XRD study.
Table 2. Percent Conversion for Metathesis Homocoupling
of 1-Octene by 1a and 2a−g (5 mol %) in C6D6 at 22 °C
(closed system)
elongated and a C1−O bond that is shortened (1.343(4) Å)
compared to the C2−O bond length of 1.435(5) Å. NBO
calculations reveal that the O lone pair donates electron density
into the MoC π* orbital (Figure 10). The NLMO of the
lone pair contains a 7.0% contribution from the alkylidene
carbon and a 3.4% contribution from Mo (98% d character).
The reaction between 1a or 1b and CH2CHSPh yields
Mo(NAr)(CHSPh)(Me2Pyr)(OTPP) (2g), which can be
isolated as a red solid in 68% yield. Its proton NMR spectrum
at 22 °C shows a single alkylidene resonance with JCH = 146
Hz. An X-ray study shows that 2g is the syn isomer in the solid
state (Figure 11) with a MoC1 bond that is slightly
elongated (1.9112(15) Å), a C1−S bond (1.7179(16) Å) that is
shorter than the C2−S bond (1.7803(16) Å), and a C2−S−C2
bond angle of 105.99(8)°. The NLMO of the S lone pair
contains a 5.1% contribution from the alkylidene carbon and a
4.7% contribution from Mo (98% d character).
X
0.5 h
1 h
2 h
10 h
1a
2a
2b
2c
2d
2e
2f
CMe2Ph
B(pin)
TMS
47
47
55
50
0
48
47
54
50
0
48
47
54
50
3
51
49
54
53
12
53
49
58
Carbaz
Pyrrol
PPh2
48
47
53
48
47
54
49
47
54
OPr
2g
SPh
except the one involving 2d. The slow initiation by 2d is no
surprise, given the relatively strong binding of the pyrrolidinone
carbonyl group to the metal. In general, conversions are limited
by equilibria that involve ethylene under the conditions
employed.
In order to probe the competency of complexes 2a−g as
initiators for olefin metathesis reactions compared to 1a, the
conversion of 1-octene to E/Z 7-tetradecene by 5 mol %
catalyst in C6D6 in a closed system (J-Young NMR tube) was
monitored over time. The results are shown in Table 2. All
reactions reach equilibrium (∼50% E/Z 7-tetradecene) in 0.5 h
In Table 3 are shown the relative amounts of the initial M
CHX complex and the heptylidene complex formed from it in
the reactions between 1a and 2a−g and 20 equivalents of 1-
octene. All except 2b, 2d, and 2g form some observable and
relatively constant amount of heptylidene (MoCHR) over a
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Table 3. Ratios of MCHX to MCHR Complexes
Observed in Reactions of 1a and 2a−g with 1-Octene in
C6D6 at 22 °C
X
0.5 h
2 h
10 h
1a
2a
2b
2c
2d
2e
2f
CMe2Ph
B(pin)
TMS
0:100
60:40
100:0
77:23
100:0
77:23
13:87
100:0
0:100
57:43
100:0
79:21
100:0
70:30
14:86
100:0
0:100
63:37
100:0
79:21
100:0
70:30
15:85
100:0
Carbaz
Pyrrol
PPh2
preference to remain in the MoCHX form in the presence of
terminal olefins (see Table 3), so the same should be true in the
presence of an internal olefin.
OPr
2g
SPh
period of 10 h. Because 2b and 2g still carry out metathesis
homocoupling rapidly (Table 2), we ascribe the lack of
observable heptylidene to a thermodynamic preference for the
MoCHX species in each case. In the case of 2d, the slow rate
of homocoupling (vide supra) also suggests that the rate of
initiation is slow.
Table 4 lists the percentage alkylidene remaining in reactions
between MoCHX complexes and 1-octene in C6D6 at 22 °C
CONCLUSIONS
■
Molybdenum and tungsten imido MCHX complexes in
which X is based on B, Si, N, P, O, or S can be prepared readily.
Rates of metathesis reactions can be rationalized on the basis of
steric factors; electronic differences due to the presence of X
bound to the alkylidene carbon do not seem to play a major
role. However, the thermodynamic preference for catalyst
resting state during a reaction depends on the nature of X. Side
reactions do not appear to lead to a dramatic increase in rates of
catalyst decomposition. Therefore, MoCHX compounds
could be intermediates in the known metathesis reactions
that involve MoCHX complexes in which X is based on O5
or B,6 and metathesis reactions that involve S- or P-based
MoCHX complexes should be possible. The data so far
suggest that the presence of X on the alkylidene carbon does
not dramatically alter the nature of the alkylidene and olefin
metathesis reactions that involve them.
Table 4. Percent Total Alkylidene Remaining in Reactions
between MoCHX Complexes and 1-Octene (15 equiv) in
C6D6 at 22 °C as a Function of Time
a
X
0.5 h
2 h
10 h
24 h
1a
2a
2b
2c
2d
2e
2f
CMe2Ph
B(pin)
TMS
100
100
100
100
100
100
100
100
82
100
86
55
66
12
18
63
37
100
0
72
Carbaz
Pyrrol
PPh2
91
68
100
92
100
34
EXPERIMENTAL SECTION
■
OPr
95
53
18
36
Mo(NAr)(CH2)(Me2Pyr)(OTPP) (1b). A stir bar, 576 mg of 1a
(0.644 mmol, 1.0 equiv), and 30 mL of pentane were added to a 100
mL Schlenk bomb in a glovebox. (Compound 1a did not completely
dissolve.) The bomb was sealed, brought out of the box, and subjected
to three freeze−pump−thaw cycles on a vacuum line. The solution
was exposed to 1 atm ethylene and stirred for 3 h. The product
precipitated as a light red powder. The bomb was brought into the
glovebox, and the solid was filtered off and washed with cold pentane;
yield 395 mg (79%). Anal. Calcd for C49H48MoN2O: C, 75.76; H,
6.23; N, 3.61. Found: C, 75.59; H, 6.35; N, 3.55.
Mo(NAr)(CHBpin)(Me2Pyr)(OTPP) (2a). In the glovebox, a 50
mL round-bottom flask was charged with a stir bar, 10 mL of toluene,
175 mg of 1b (0.225 mmol, 1.0 equiv), and 57.3 μL of vinylboronic
acid pinacol ester (0.338 mmol, 1.5 equiv). The flask was capped, and
the contents were stirred for 3 h at room temperature. The solvent was
removed in vacuo. Pentane (10 mL) was added, and the solvent was
removed in vacuo again. Pentane (10 mL) was again added, and the
red slurry was stirred and filtered to obtain 135 mg of pale orange
product (66% yield). Compound 2a can also be synthesized using the
same procedure from Mo(NAr)(CHCMe2Ph)(Me2Pyr)(OTPP) and
2 equivalents of vinylboronic acid pinacol ester in 83% yield. Anal.
Calcd for C55H59MoBN2O3: C, 73.17; H, 6.59; N, 3.10. Found: C,
72.82; H, 6.81; N, 2.93.
Mo(NAr)(CHSiMe3)(Me2Pyr)(OTPP) (2b). In the glovebox, a 50
mL round-bottom flask was charged with a stir bar, 10 mL of toluene,
166 mg of 1b (0.214 mmol, 1.0 equiv), and 157 μL of
trimethylvinylsilane (1.07 mmol, 5.0 equiv). The flask was capped,
and the contents were stirred for 2 h at RT, after which time the
solvent was removed in vacuo. Pentane was added (10 mL), and the
solvent was removed in vacuo again. Pentane was again added (5 mL),
and the red slurry was stirred and filtered to obtain 86 mg of pure
orange solid product (47% yield). Anal. Calcd for C52H56MoN2OSi: C,
73.56; H, 6.65; N, 3.30. Found: C, 73.24; H, 6.66; N, 3.21.
2g
SPh
92
60
a
Initial alkylidene present after 0.5 h is defined as 100%.
versus an internal standard as a function of time. All except 2d,
which is essentially inert, have decomposed to a significant
degree after 24 h. In most cases decomposition is likely to
involve bimolecular coupling of alkylidenes (especially
methylidenes) or rearrangement of metallacyclobutane com-
plexes, including unsubstituted metallacycles.17
In order to investigate the relative reactivity of the
heteroatom-substituted alkylidene complexes toward internal
olefins, compounds 1a and 2a−g were treated with 15
equivalents of cis-4-octene in C6D6 and the disappearance of
1
MoCHX was monitored over time by H NMR versus an
internal standard. Complexes 1a, 2b, 2c, 2d, 2e, and 2g showed
little to no conversion, even after 2 days. In contrast, 2a and 2f
were rapidly converted to butylidene in a pseudo-first-order
fashion.
A kinetic study of the rate of conversion to butylidene (eq 2)
yielded first-order rate constants of 9.9 × 10−5 M−1 s−1 for 2a
and 1.2 × 10−3 M for 2f (see SI for details). Compound 2f
reacts with cis-4-octene about 10 times faster than 2a reacts
with cis-4-octene, perhaps largely because the CHOPr ligand in
2f is much smaller than the CHB(pin) ligand in 2a near the
metal. The relative rates of reaction of the syn or the anti
isomers of 2a are not known. Of the remaining unreactive
species, 1a, 2c, and 2e contain alkylidenes that are relatively
sterically demanding. Finally, 2b, 2d, and 2g show a strong
E
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Mo(NAr)(CHCarbaz)(Me2Pyr)(OTPP) (2c). In the glovebox, a 50
mL round-bottom flask was charged with a stir bar, 10 mL of toluene,
165 mg of 1b (0.213 mmol, 1.0 equiv), and 41 mg of N-vinylcarbazole
(0.213 mmol, 1.0 equiv). The flask was capped, and the contents were
stirred for 4 h at RT. The solvent was removed in vacuo, pentane was
added (10 mL), and the solvent was removed in vacuo again. Pentane
was again added (10 mL), and the red slurry was filtered to obtain 163
mg of pure orange solid product (81% yield). Anal. Calcd for
C61H55MoN3O: C, 77.77; H, 5.88; N, 4.46. Found: C, 77.47; H, 6.15;
N, 4.20.
Mo(NAr)(CHPyrrol)(Me2Pyr)(OTPP) (2d). In the glovebox, a 50
mL round-bottom flask was charged with a stir bar, 10 mL of toluene,
200 mg of 1b (0.257 mmol, 1.0 equiv), and 41 μL of N-
vinylpyrrolidinone (0.386 mmol, 1.5 equiv). The flask was capped,
and the contents were stirred for 4 h at RT. The solvents were
removed in vacuo, pentane was added, and the solvent was removed in
vacuo again. Pentane was again added, and the red slurry was filtered to
obtain 171 mg of dark pink product (77% yield). Anal. Calcd for
C53H53MoN3O2: C, 74.02; H, 6.21; N, 4.89. Found: C, 74.05; H, 6.28;
N, 4.76.
Mo(NAr)(CHPPh2)(Me2Pyr)(OTPP) (2e) and MeCN Adduct
(2e′). In the glovebox, a 50 mL round-bottom flask was charged with a
stir bar, 8 mL of toluene, 119 mg of 1b (0.153 mmol, 1.0 equiv), and
31 μL of diphenylvinylphosphine (0.153 mmol, 1.0 equiv). The flask
was capped, and the contents were stirred for 3 h at RT, after which
time the solvent was removed in vacuo. Pentane was added (10 mL),
and the solvent was removed in vacuo again. Pentane was again added
(10 mL), and the red slurry was stirred and filtered to obtain 92 mg of
red product (63% yield). The acetonitrile adduct of 2e can be obtained
as an orange powder in 79% yield by adding acetonitrile in place of
pentane in the workup. Compound 2e appears to decompose slowly in
the solid state, and 2e′ tended to lose acetonitrile. Therefore,
consistent elemental analyses of either could not be obtained.
Mo(NAr)(CHOPr)(Me2Pyr)(OTPP) (2f). In the glovebox, a 50 mL
round-bottom flask was charged with a stir bar, 10 mL of toluene, 170
mg of 1a (0.190 mmol, 1.0 equiv), and 43 μL of propyl vinyl ether
(0.380 mmol, 2.0 equiv). The flask was closed, and the contents were
stirred for 1 h at RT, after which time the solvent was removed in
vacuo. Pentane was added (10 mL), and the solvent was removed in
vacuo again. Pentane was again added (10 mL), and the red slurry was
filtered to obtain 81 mg of orange product (51% yield). Anal. Calcd for
C52H54MoN2O2: C, 74.80; H, 6.52; N, 3.36. Found: C, 74.88; H, 6.56;
N, 3.36.
Mo(NAr)(CHSPh)(Me2Pyr)(OTPP) (2g). In the glovebox, a 50 mL
round-bottom flask was charged with a stir bar, 10 mL of toluene, 200
mg of 1a (0.223 mmol, 1.0 equiv), and 58.3 μL of phenyl vinyl sulfide
(0.446 mmol, 2.0 equiv). The flask was closed, and the contents were
stirred for 19 h at RT, after which time the solvent was removed in
vacuo. Pentane was added (10 mL), and the solvent was removed in
vacuo again. Pentane was again added (10 mL), and the red slurry was
filtered to obtain 133 mg of pink solid product (68% yield). Anal.
Calcd for C55H52MoN2OS: C, 74.64; H, 5.92; N, 3.17. Found: C,
74.46; H, 5.89; N, 2.99.
ACKNOWLEDGMENTS
■
We are grateful to the National Science Foundation (CHE-
1111133 to R.R.S.) and to the National Institutes of Health
(Grant GM-59426 to R.R.S. and A.H.H.) for financial support.
We thank the National Science Foundation for departmental X-
ray diffraction instrumentation (CHE-0946721).
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ASSOCIATED CONTENT
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S
* Supporting Information
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http://pubs.acs.org.
́
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AUTHOR INFORMATION
■
Corresponding Author
*E-mail: rrs@mit.edu.
Notes
The authors declare no competing financial interest.
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dx.doi.org/10.1021/om400584f | Organometallics XXXX, XXX, XXX−XXX