Factors influencing the outcomes of intermolecular C-H activations of hydrocarbons initiated by CpW(NO)(CH2CMe3) (η3-allyl) complexes (Cp = η5-C5Me 5 (Cp*), η5-C5Me4H (Cp′))

Article abstract of DOI:10.1021/om201133r

Gentle thermolyses of CpW(NO)(CH₂CMe₃) (η³-allyl) complexes (Cp = η⁵-C₅Me ₅ (Cp*), η⁵-C₅Me₄H (Cp′)) in neat hydrocarbon solutions result in the loss of neopentane from the metal's coordination spheres and the transient formation of the 16-electron (16e) intermediate species CpW(NO)(η²-allene) and/or CpW(NO)(η²-diene). These transient intermediates can react with hydrocarbon substrates, RH (R = alkyl, aryl), to form three different types of organometallic products. The first products are the desired CpW(NO) (η³-allyl)(η¹-R) complexes that result from the selective single activation of a C-H bond of RH. The second class of products involves CpW(NO)(H)[η³-(R)-allyl] complexes that are isomers of the CpW(NO)(η³-allyl)(η¹-R) compounds resulting from an intramolecular R/allyl H exchange. Finally, the third type of products contains CpW(NO)(H)[η³-hydrocarbyl] species that result from three successive C-H activations of hydrocarbon substrates such as R′CH₂CH₂CH₃ and loss of the original allyl ligand. Just which organometallic products ultimately result from the reactions of the CpW(NO)(CH₂CMe₃)(η³-allyl) complexes with hydrocarbons depends on several factors, including the natures of the cyclopentadienyl and allyl ligands, the hydrocarbon substrates themselves, the electron density at the metal centers, and the experimental conditions employed. This article documents these dependences and identifies the optimum CpW(NO)(CH₂CMe₃)(η³-allyl) compounds and experimental conditions for effecting the selective single C-H bond activations of hydrocarbon substrates such as benzene as a representative arene and methylcyclohexane as a representative alkane. During the course of these investigations all new organometallic complexes have been characterized by conventional spectroscopic methods, and the solid-state molecular structures of several of them have been established by single-crystal X-ray crystallographic analyses.

Full text of DOI:10.1021/om201133r

Article
pubs.acs.org/Organometallics
Factors Influencing the Outcomes of Intermolecular C−H Activations
of Hydrocarbons Initiated by CpW(NO)(CH2CMe3)(η3-allyl) Complexes
(Cp = η5-C5Me5 (Cp*), η5-C5Me4H (Cp′))
Rhett A. Baillie, Tommy Tran, Kathryn M. Lalonde, Jenkins Y. K. Tsang, Michelle E. Thibault,
Brian O. Patrick, and Peter Legzdins*
Department of Chemistry, The University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1
S
* Supporting Information
ABSTRACT: Gentle thermolyses of CpW(NO)(CH2CMe3)-
(η3-allyl) complexes (Cp = η5-C5Me5 (Cp*), η5-C5Me4H
(Cp′)) in neat hydrocarbon solutions result in the loss of
neopentane from the metal’s coordination spheres and the
transient formation of the 16-electron (16e) intermediate
species CpW(NO)(η2-allene) and/or CpW(NO)(η2-diene).
These transient intermediates can react with hydrocarbon
substrates, RH (R = alkyl, aryl), to form three different types
of organometallic products. The first products are the desired
CpW(NO)(η3-allyl)(η1-R) complexes that result from the
selective single activation of a C−H bond of RH. The second
class of products involves CpW(NO)(H)[η3-(R)-allyl] com-
plexes that are isomers of the CpW(NO)(η3-allyl)(η1-R) compounds resulting from an intramolecular R/allyl H exchange.
Finally, the third type of products contains CpW(NO)(H)[η3-hydrocarbyl] species that result from three successive C−H
activations of hydrocarbon substrates such as R′CH2CH2CH3 and loss of the original allyl ligand. Just which organometallic
products ultimately result from the reactions of the CpW(NO)(CH2CMe3)(η3-allyl) complexes with hydrocarbons depends on
several factors, including the natures of the cyclopentadienyl and allyl ligands, the hydrocarbon substrates themselves, the
electron density at the metal centers, and the experimental conditions employed. This article documents these dependences and
identifies the optimum CpW(NO)(CH2CMe3)(η3-allyl) compounds and experimental conditions for effecting the selective
single C−H bond activations of hydrocarbon substrates such as benzene as a representative arene and methylcyclohexane as a
representative alkane. During the course of these investigations all new organometallic complexes have been characterized by
conventional spectroscopic methods, and the solid-state molecular structures of several of them have been established by single-
crystal X-ray crystallographic analyses.
bond at 50 °C via η2-allene and η2-diene intermediate
INTRODUCTION
■
complexes and forms the expected phenyl complex Cp*W-
(NO)(Ph)(η3-CH2CHCMe2) in good yields.4 In contrast,
thermolyses of the dimethylallyl compound in alkane solvents
appear to afford mixtures of allyl hydride complexes resulting
from three successive C−H bond activations at different places
on the alkanes following loss of the original 1,1-dimethylallyl
ligand.4
The situation is reversed for the monomethylallyl compound
Cp*W(NO)(CH2CMe3)(η3-CH2CHCHMe) and the phenyl-
allyl complex Cp*W(NO)(CH2CMe3)(η3-CH2CHCHPh)
(Scheme 2). In the presence of linear alkanes, both compounds
initiate sp3 C−H activations of the hydrocarbons exclusively at
their terminal carbon atoms and cleanly form Cp*W(NO)(n-
alkyl)(η3-CH2CHCHR) (R = Me, Ph) complexes via either an
η2-diene or an η2-allene intermediate complex.5,6 In contrast,
Current interest in effecting the activation and functionalization
of hydrocarbon C−H bonds continues to be motivated by the
long-term goal to develop new synthetic pathways to a broad
range of industrially important products beginning with
unfunctionalized starting materials.1 Our recent contributions
to this area of chemistry have involved the family of
Cp*W(NO)(alkyl)(η3-allyl) (Cp* = η5-C5Me5) complexes,2
which initiate various types of C−H activations. However, a
more complete understanding of the mechanisms of these
activations is required before these organometallic nitrosyl
complexes can be utilized productively by synthetic chemists
for the selective functionalization of C−H bonds.3 Specifically,
explanations must first be found for the strikingly differing
reactivities exhibited by various members of this family of
compounds even though similar C−H-activating intermediate
complexes are involved. For instance, as summarized in Scheme
1, the dimethylallyl complex Cp*W(NO)(CH2CMe3)(η3-
CH2CHCMe2) effects the clean activation of a benzene C−H
Received: November 15, 2011
Published: January 20, 2012
© 2012 American Chemical Society
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compounds in order to fully understand their chemistry. A
portion of this work has been communicated previously.7
Scheme 1
RESULTS AND DISCUSSION
■
Reactions of the CpW(NO)(CH2CMe3)(η3-CH2CHCHMe)
Complexes (Cp = Cp*, Cp′) with Benzene. The first system
that we investigated in detail involved the monomethylallyl
compounds, since the Cp* complex was known to form a
“complex mixture of organometallic compounds” in benzene.5
As a result of our investigations, the various transformations
extant in the monomethylallyl systems can be summarized as
shown in Scheme 3 with C6D6 as the reactive substrate. The
1
conversions depicted in Scheme 3 have been monitored by H
NMR spectroscopy, and they have also been effected on a
preparative scale with C6H6 as the reactant. As illustrated in
Scheme 3, the η2-diene intermediate complexes A (i.e., either
A* or A′)8 activate C6D6 in the anticipated manner to form the
corresponding phenyl derivatives as the two isomers 2a-d6 and
2b-d6. However, 2a-d6 and 2b-d6 ultimately convert to the
hydrido complexes 3-d6 and 4-d6, respectively, by intra-
molecular exchange of the newly formed phenyl ligand with a
terminal hydrogen atom on the allyl ligand. To the best of our
knowledge, this type of isomerization, which is probably
mediated by the metal center, is without precedent in the
chemical literature.
the monomethylallyl compound loses neopentane at ambient
temperatures in benzene solutions and forms a brown solution
that contains a “complex mixture of organometallic com-
Our elucidation of the chemistry initiated by these reactants
was facilitated by our discovery that replacement of the Cp*
ligand in the monomethylallyl reactant by the less sterically
demanding Cp′ group results in significantly slower reaction
rates.7 Thus, as illustrated in Figure 1, the C−H activation of
benzene at 26 °C by Cp′W(NO)(CH2CMe3)(η3-
CH2CHCHMe)9 (1′) affords only the isomeric phenyl
complexes 2a′ and 2b′ during the first 24 h.9 In contrast, the
identical reaction involving 1* results after 4 h in the
production of at least five new organometallic complexes
(counting the isomer of 3, which is not shown in Scheme 3).
Crystallization of 2′ from pentane provides crystals that contain
both 2a′ and 2b′ in the lattice (Figure 2), but similar treatment
of 2* produces crystals that contain only 2a* (Figure 3) whose
intramolecular dimensions are essentially identical with those of
2a′. As in other Cp*W(NO)(alkyl)(η3-allyl) complexes,2 the
allyl ligands of complexes 2 are in endo orientations with the
pounds”.5
These observations clearly indicate that it is not the nature of
the 16e intermediate formed by thermolysis of the Cp*W-
(NO)(alkyl)(η3-allyl) precursor complex that determines the
eventual outcomes of the C−H activations initiated by that
complex. Consequently, we decided to investigate these
Cp*W(NO)(CH2CMe3)(η3-allyl) systems more fully with a
view to finding the explanations for their differing chemical
behaviors, particularly why some C−H activations produce just
a single organometallic product whereas others afford a
plethora of products. In this article we present the results of
our investigations, which in some cases have been extended to
encompass the Cp′ analogues (Cp′ = η5-C5Me4H) of these
Scheme 2
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Scheme 3
Figure 2. Solid-state molecular structures of 2a′ (right) and 2b′ (left)
as they occur in the asymmetric unit with 30% probability thermal
ellipsoids shown. Selected interatomic distances (Å) and angles (deg):
2a′, W(2)−C(29) = 2.360(3), W(2)−C(30) = 2.331(3), W(2)−
C(31) = 2.291(3), W(1)−C(33) = 2.214(3), W(2)−N(2) = 1.775(3),
N(2)−O(2) = 1.223(4), C(29)−C(30) = 1.378(5), C(30)−C(31) =
1.423(5), C(31)−C(32) = 1.512(5), C(29)−C(30)−C(31) =
118.2(3), W(2)−N(2)−O(2) = 172.1(3); 2b′, W(1)−C(10) =
2.232(3), W(1)−C(11) = 2.357(3), W(1)−C(12) = 2.506(3),
W(1)−C(14) = 2.210(3), W(1)−N(1) = 1.773(3), N(1)−O(1) =
1.225(4), C(10)−C(11) = 1.424(5), C(11)−C(12) = 1.367(5),
C(12)−C(13) = 1.501(5), C(10)−C(11)−C(12) = 119.2(3),
C(11)−C(12)−C(13) = 123.1(4), C(30)−C(31)−C(32) =
120.4(3), W(1)−N(1)−O(1) = 169.0(3).
Figure 1. Distribution of organometallic complexes during the C−H
activation of benzene by 1′ at 26 °C.
meso protons pointing away from the cyclopentadienyl rings.
Furthermore, there is a σ−π distortion of the allyl ligands
brought about by the electronic asymmetry at the metal
centers.10 The spectroscopic properties of complexes 2 indicate
that they retain their “piano-stool” molecular structures in
solution. Interestingly, dissolution of crystals of 2a* in C6D6
two substituents on C(13) (Figure 4).11 The final H NMR
1
1
immediately results in a solution whose H NMR spectrum
spectrum of the mixture of 3* and 4* in C6D6 also exhibits
resonances that may be assigned to the minor coordination
isomer of 3*, in which the phenyl substituent on the allyl ligand
is situated at the opposite end, adjacent to the nitrosyl group.
Kinetic analyses of the benzene-activation reactions yield
pseudo-first-order rate constants (s−1) and Arrhenius activation
energies (kJ mol−1) of (8.5 0.2) × 10−5 and 79.1 1.9 and
(3.6 0.1) × 10−5 and 93.2 6.6 for 1* and 1′, respectively.
The corresponding Eyring parameters ΔH⧧ (kJ mol−1) and ΔS⧧
(J K−1 mol−1) are 76.5 1.9 and −66.6 3.0 and 90.6 6.6
and −27.4 3.4, respectively. The subsequent isomerizations
of 2a,b to the hydrido complexes 3 and 4 also occur more
rapidly for the Cp* complexes. Thus, signals due to 3* and 4*
exhibits signals attributable to both 2a* and 2b*, thereby
indicating that the two isomers are in rapid equilibrium with
each other.
The synthesis of isomeric complexes 3* (minor) and 4*
(major) is facilitated by warming of the reaction mixture to 45
°C for 24 h. Their molecular structures have been deduced
1
from their diagnostic H and 13C APT NMR spectra, and the
structure of 4* has been confirmed by an X-ray crystallographic
analysis (Figure 4). The signals due to the hydride ligands in 3*
and 4* occur at δ −0.63 ppm (1JWH = 124 Hz) and −0.05 (1JWH
= 127 Hz), respectively, and the intramolecular metrical
parameters of 4* are similar to those of the other new
complexes isolated during this work. Interestingly, the allyl
ligand in 4* is in an exo orientation, probably because of the
1
begin to appear in the H NMR spectrum of the benzene
reaction mixture after 4 h at 26 °C when only 75% of 1* has
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forms Cp′W(NO)(n-alkyl)(η3-CH2CHCHMe) complexes such
as 5′ and 6′ shown in Scheme 4, but at a slower rate than the
Cp* complex. The practical advantage of the Cp′ system is
again that the product n-alkyl complexes are generally more
thermally stable at a particular temperature than are their Cp*
analogues.
Reactions of the CpW(NO)(CH2CMe3)(η3-CH2CHCHPh)
Complexes (Cp = Cp*, Cp′) with Benzene. Given the
results obtained with the monomethylallyl complexes 1 as
summarized in the preceding section, we decided to ascertain if
the situation was equally complex for the related phenylallyl
systems. The thermolysis of Cp*W(NO)(CH2CMe3)(η3-
CH2CHCHPh) (7*) in benzene at 75 °C for 1 day leads to
the exclusive formation of one new organometallic species
(Scheme 5). This pale yellow complex can be purified by
chromatography on alumina and crystallized from pentane/
Et2O as needles. An X-ray crystallographic analysis of one of
these needles has revealed this compound to be Cp*W(NO)-
(H)(η3-PhHCCHCHPh) (9*), whose solid-state molecular
structure is shown in Figure 5. In 9* the phenyl group resulting
from the C−H activation of benzene is attached to the
previously unsubstituted end of the phenylallyl ligand, thus
converting it into a 1,3-diphenylallyl ligand. A metal−hydride
linkage is also present in this compound, as evidenced by a
characteristic hydride signal at −0.15 ppm (1JWH = 124 Hz) in
Figure 3. Solid-state molecular structure of 2a* with 30% probability
thermal ellipsoids shown. Selected interatomic distances (Å) and
angles (deg): W(1)−C(11) = 2.378(5), W(1)−C(12) = 2.339(5),
W(1)−C(13) = 2.277(5), W(1)−C(15) = 2.216(5), W(1)−N(1) =
1.779(4), N(1)−O(1) = 1.220(5), C(11)−C(12) = 1.380(9), C(12)−
C(13) = 1.424(9), C(13)−C(14) = 1.476(9), C(11)−C(12)−C(13)
= 118.7(5), C(12)−C(13)−C(14) = 120.1(6), W(1)−N(1)−O(1) =
167.8(4).
1
the H NMR spectrum of 9* in C6D6. Labeling experiments
with benzene-d6 have confirmed that this transformation does
indeed proceed via an intermediate 16e η2-allene complex
(Scheme 5).
We next decided to synthesize the Cp′ analogue of 7* (i.e.,
7′) and to investigate its thermal behavior in benzene with a
view to acquiring additional evidence in support of the
mechanism depicted in Scheme 5. Cp′W(NO)(CH2CMe3)-
(η3-CH2CHCHPh) (7′) can be synthesized in moderate yields
by utilizing the procedure reported for its Cp* analogue,2 and
its solid-state molecular structure is shown in Figure 6. The
replacement of a methyl group by a hydrogen atom on a
cyclopentadienyl ligand is expected to decrease the inductive
electronic contribution of the ligand to the tungsten center.
Such an effect is manifested by the infrared nitrosyl-stretching
frequency of 7′, which at 1600 cm−1 is slightly higher in energy
than that exhibited by 7* at 1588 cm−1. As expected, our
investigations of the thermal chemistry of 7′ have revealed that
it generally parallels that of 7*, but the transformations proceed
at a significantly slower rate.
Thermolysis of 7′ in benzene at 55 °C for 6 days produces
the corresponding 1,3-diphenylallyl hydride derivative Cp′W-
(NO)(H)(η3-PhHCCHCHPh) (9′) (Scheme 6). As with
complex 1′, the reaction of 7′ proceeds at a rate slower than
that exhibited by the pentamethylcyclopentadienyl analogue 7*.
This fact facilitates the isolation of the phenyl derivative
Cp′W(NO)(C6H5)(η3-CH2CHCHPh) (8′), following thermol-
ysis of 7′ in benzene for 22 h and subsequent purification by
column chromatography. The isolation of 8′ supports the
mechanism depicted in Scheme 5, in which complex 9* is
formed via the initial C−H activation of benzene, leading to the
phenyl derivative 8*, followed by the subsequent aryl−
hydrogen isomerization. The rates of conversion of 7′ to 8′
and 8′ to 9′ are again slower than those observed for the
analogous transformations of 7* and 8*. Hence, the slower
rates of reaction of the Cp′ complexes thus permit them to be
used as models for the Cp* systems in order to investigate
more fully the mechanistic details of the thermal C−H bond-
Figure 4. Solid-state molecular structure of 4* with 30% probability
thermal ellipsoids shown. Selected interatomic distances (Å) and
angles (deg): W(1)−C(11) = 2.279(3), W(1)−C(12) = 2.279(3),
W(1)−C(13) = 2.461(3), W(1)−H(1) = 1.68(4), W(1)−N(1) =
1.774(2), N(1)−O(1) = 1.222(3), C(15)−C(13) = 1.499(4), C(13)−
C(12) = 1.400(4), C(12)−C(11) = 1.417(4), C(15)−C(13)−C(12)
= 119.4(2), C(13)−C(12)−C(11) = 124.2(3), W(1)−N(1)−O(1) =
175.4(2).
been consumed. In contrast, hydride resonances attributable to
3′ and 4′ only begin to appear after 24 h at 26 °C when 96% of
1′ has reacted. In other words, for the first 24 h the Cp′ reaction
mixture contains only three organometallic complexes (cf.
Figure 1), whereas the Cp* reaction mixture after 4 h under
identical conditions contains at least six such compounds: i.e.,
“a complex mixture”.5 Clearly, the isolation of the desired
products resulting from the C−H activation of benzene is
easiest for the Cp′ system.
In general, the C−H activation chemistry exhibited by the
monomethylallyl compound Cp′W(NO)(CH2CMe3)(η3-
CH2CHCHMe) (1′) closely resembles that of its Cp*
congener. Specifically, it also initiates sp3 C−H activations of
the hydrocarbons exclusively at their terminal carbons and
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Scheme 4
Scheme 5
activation chemistry of various Cp*W(NO)(alkyl)(η3-allyl)
complexes.
formation of two different organometallic complexes (Scheme
7).
The major organometallic product, Cp*W(NO)(η3-
C7H11)(H) (11*), arises from two additional C−H activations
of the methylcyclohexyl ligand, a process accompanied by the
loss of the phenylallyl group from the metal’s coordination
sphere. Complex 11* has been previously prepared in our
laboratories via two routes. It was first made as an isomeric
mixture by thermolysis of Cp*W(NO)(CH2CMe3)2 in
methylcyclohexane.12 A similar experiment using Cp*W(NO)-
(CH2CMe3)(η3-CH2CHCMe2) afforded the same products,
Reaction of Cp*W(NO)(CH2CMe3)(η3-CH2CHCHPh)
with Methylcyclohexane. During our investigations we
have discovered that the reactions of Cp*W(NO)(CH2CMe3)-
(η3-CH2CHCHPh) (7*) with methyl- and ethylcyclohexane
provide some insights as to the conversions that occur when
multiple products are formed during the C−H activations of
alkanes initiated by these systems. We have previously reported
that thermolysis of 7* in methylcyclohexane at 55 °C for 2 days
affords a single organometallic complex, namely dark orange
Cp*W(NO)(CH2C6H11)(η3-CH2CHCHPh) (10*), as well as
some unreacted starting material.6 We have now discovered
that continuing the thermolysis for 4 days in total leads to the
4
1
albeit in a slightly different ratio. The H NMR spectrum of
the final reaction mixture following the prolonged thermolysis
of 7* clearly exhibits signals diagnostic of 11* (i.e., δ −0.72 (s,
1JWH = 123 Hz, 1H, WH), 1.77 (s, 15H, C5Me5)).
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The minor product, Cp*W(NO)(H)(η3-CH(CH2C6H11)-
CHCHPh) (12*), has been fully characterized and is an isomer
of 10* that results from the formal exchange of the
methylcyclohexyl group at the metal center with a terminal
hydrogen atom of the phenylallyl ligand. It thus resembles the
isomerizations of the allyl phenyl complexes described in the
1
preceding sections. Consistently, in the H NMR spectrum of
12* in C6D6 the C5Me5 singlet at 1.69 ppm integrates as 15:1:1
to the tungsten hydride resonance at −1.10 ppm and the
doublet of doublets due to the allyl meso hydrogen at 5.19
ppm. Consistently, the coupling constants for this doublet of
doublets are the same as two of those for the doublet of
doublets of doublets attributable to the meso hydrogen of the
allyl ligand in complex 7* (Figure 7), thereby confirming that
the methylcyclohexyl group is indeed a terminal substituent on
the phenylallyl ligand in 12*.
A plausible mechanism for the rearrangement of 10* to 12*
is shown in Scheme 8. It begins with 10* being in its least
sterically congested configuration: i.e., the phenyl substituent
on the allyl ligand is proximal to the nitrosyl ligand and distal to
the methylcyclohexyl ligand. The alkyl ligand can then effect an
intramolecular nucleophilic attack on the phenylallyl CH2
terminus. A hydrogen from the same allyl carbon atom is
then abstracted by the tungsten to form the 16-electron
intermediate Cp*W(NO)(η1-H)(η1-CH(CH2C6H11)C(H)
CHPh), which rapidly isomerizes to the 18-electron complex
12* (Scheme 8).
Figure 5. Solid-state molecular structure of one of the independent
molecules of Cp*W(NO)(H)(η3-PhHCCHCHPh) (9*) with 30%
probability thermal ellipsoids shown. Selected interatomic distances
(Å) and angles (deg): W(1)−C(1) = 2.406(10), W(1)−C(2) =
2.302(9), W(1)−C(3) = 2.264(9), W(1)−N(1) = 1.758(7), N(1)−
O(1) = 1.226(10), C(1)−C(2) = 1.409(15), C(2)−C(3) = 1.368(14),
C(3)−C(4) = 1.471(14), C(1)−C(10) = 1.454(14), C(1)−C(2)−
C(3) = 120.0(10), C(2)−C(3)−C(4) = 122.3(10), C(2)−C(1)−
C(10) = 126.0(10), W(1)−N(1)−O(1) = 169.7(7).
The reaction of Cp*W(NO)(CH2CMe3)(η3-CH2CHCHPh)
(7*) with methylcyclohexane thus first forms the product
resulting from the single activation of a terminal methyl sp3 C−
H bond, namely Cp*W(NO)(CH2C6H11)(η3-CH2CHCHPh)
(10*). However, longer reaction times result in the conversion
of 10* to a mixture of the allyl hydrido complexes 11* and 12*,
the former resulting from two additional C−H activations of
the methylcyclohexyl group and the latter being formed by the
formal exchange of the methylcyclohexyl group at the metal
center with a terminal hydrogen atom of the phenylallyl ligand
(Scheme 7).
Reaction of Cp*W(NO)(CH2CMe3)(η3-CH2CHCHPh)
with Ethylcyclohexane. The thermolysis of 7* in ethyl-
cyclohexane initially proceeds in a manner similar to its reaction
with methylcyclohexane: namely, a methyl C−H bond of the
solvent is selectively activated to produce Cp*W(NO)-
(CH2CH2C6H11)(η3-CH2CHCHPh) (13*).6 Extended ther-
molysis leads only to the formation of the two isomers of
Cp*W(NO)(H)(η3-C8H13) (14a* and 14b*) resulting from
multiple C−H bond activations of ethylcyclohexane (Scheme
9). The isomeric complexes 14a* and 14b* have been
previously prepared by the thermolysis of Cp*W(NO)-
(CH2CMe3)2 in ethylcyclohexane.12 Consequently, the com-
pounds synthesized during this work were identified by
comparing their 1H NMR spectra to those previously reported.
Interestingly, the cyclohexylethyl ligand in complex 13* does
Figure 6. Solid-state molecular structure of 7′ with 30% probability
thermal ellipsoids shown. Selected interatomic distances (Å) and
angles (deg): W(1)−C(21) = 2.305(5), W(1)−C(22) = 2.322(5),
W(1)−C(23) = 2.375(5), W(1)−C(10) = 2.249(6), W(1)−N(1) =
1.775(5), N(1)−O(1) = 1.218(6), C(20)−C(21) = 1.474(8), C(21)−
C(22) = 1.422(7), C(22)−C(23) = 1.378(8), C(21)−C(22)−C(23)
= 118.6(5), C(20)−C(21)−C(22) = 125.8(5), W(1)−C(10)−C(11)
= 123.6(4), W(1)−N(1)−O(1) = 170.7(4).
Scheme 6
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Scheme 7
Scheme 9
distance between the cyclohexyl group and the tungsten center.
Thus, the cyclohexylmethyl group is more sterically crowded at
the metal center in 10*, and that may well account for its
proclivity to effect the alkyl−hydrogen exchange which forms
complex 12*. Consistent with this conclusion is the fact that we
have never observed the intramolecular migration of a linear
alkyl ligand to the allyl group in any of our systems.
The extrapolation of these results to the C−H activation of
linear alkanes by η2-allene intermediate complexes (such as
Cp*W(NO)(η2-H2CCCMe2) generated from the dime-
thylallyl complex) is straightforward and accounts for why the
final reaction mixtures contain a number of hydrido allyl
complexes. Specifically, the thermolysis of Cp*W(NO)-
(CH2CMe3)(η3-CH2CHCMe2) in n-pentane leads to the
formation of isomers of Cp*W(NO)(H)(η3-C5H9)
(15a*,b*), which result from multiple C−H activations of
the solvent molecules (Scheme 10).
1
Figure 7. Expansion of the H NMR spectrum (5.83 to 5.03 ppm) of
7* and 12* in C6D6 displaying the resonances due to the meso CH
protons of 7* (δ 5.56, 3JHH = 13.2, 9.7, 7.6 Hz) and 12* (δ 5.19, 3JHH
= 13.2, 9.7 Hz) and the schematic for meso hydrogen coupling in 7*
(left) and 12* (right).
Scheme 8
Role of Electron Densities at the Tungsten Centers. As
summarized in Table 1, a correlation exists between the
observed thermal chemistry of the various CpW(NO)(R)(η3-
allyl) (R = alkyl, aryl) complexes and the electron densities at
the tungsten centers of these compounds, as indicated by their
infrared nitrosyl stretching frequencies.
For instance, Cp*W(NO)(CH2CMe3)(η3-CH2CHCHMe)
(1) (entry 3) and Cp*W(NO)(CH2CMe3)(η3-CH2CHCHPh)
(7*) (entry 7) have higher nitrosyl stretching frequencies and
thus less electron rich tungsten centers. These two complexes
initiate the activation of only a single primary sp3 C−H bond of
alkane substrates. In contrast, Cp*W(NO)(CH2CMe3)(η3-
CH2CHCMe2) (entry 1) has a lower nitrosyl stretch and a
more electron rich tungsten center, and this complex facilitates
multiple C−H bond activations of alkane substrates. This
correlation can also be applied to the complexes resulting from
the initial C−H activations. Thus, as demonstrated during this
work, subsequent C−H bond activations occur with complexes
10* and 13* (entries 11 and 12), which again have more
electron rich tungsten centers. Such multiple C−H activations
of a substrate occur via intramolecular hydrogen transfer
processes mediated by the tungsten centers, and these
processes are evidently more facile for the more electron-rich
metal centers.
not undergo migration to the phenylallyl ligand as does the
cyclohexylmethyl group during the conversion of 10* into 12*
(Scheme 8). Since complexes 10* and 13* exhibit similar IR
nitrosyl stretching frequencies, the presence or absence of an
alkyl migration event is likely due primarily to steric rather than
electronic influences. In complex 10* the cyclohexyl group is
separated from the tungsten center by a single carbon atom,
while for the cyclohexylethyl ligand there is a two-carbon
The other transformation that can occur with a Cp*W-
(NO)(R)(η3-allyl) complex resulting from initial activation of
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Scheme 10
Table 1. Correlation of Nitrosyl Stretching Frequencies of Some CpW(NO)(R)(η3-allyl) (R = Alkyl, Aryl) Complexes with
Their Reactivities
−1
entry
complex
νNO (Nujol, cm ) multiple alkane C−H activations? R−allyl H exchange?
ref
1
Cp*W(NO)(CH2CMe3)(η3-CH2CHCMe2)
Cp*W(NO)(Ph)(η3-CH2CHCMe2)
1546
1562
1594
1595
yes
no
no
no
no
no
no
no
no
no
yes
yes
no
no
no
no
yes
yes
no
no
yes
yes
yes
no
4
4
2
3
Cp*W(NO)(CH2CMe3)(η3-CH2CHCHMe) (1*)
Cp′W(NO)(CH2CMe3)(η3-CH2CHCHMe) (1′)
Cp*W(NO)(C6D5)(η3-CH2CDCHMe) (2*)
Cp′W(NO)(C6D5)(η3-CH2CDCHMe) (2′)
Cp*W(NO)(CH2CMe3)(η3-CH2CHCHPh) (7*)
Cp′W(NO)(CH2CMe3)(η3-CH2CHCHPh) (7′)
Cp*W(NO)(Ph)(η3-CH2CHCHPh) (8*)
Cp′W(NO)(Ph)(η3-CH2CHCHPh) (8′)
5 and this work
this work
4
5
this work
6
this work
7
1588
1591
this work
8
this work
9
this work
10
11
12
1591
1562
1562
this work
Cp*W(NO)(CH2C6H11)(η3-CH2CHCHPh) (10*)
Cp*W(NO)(CH2CH2C6H11)(η3-CH2CHCHPh) (13*)
6 and this work
6 and this work
Scheme 11
an R−H bond is most commonly encountered when R−H is
benzene, and it involves exchange of the phenyl ligand with a
terminal hydrogen atom of the allyl ligand, a typical example
being shown in Scheme 3 (vide supra). A plausible mechanism
for this isomerization involves intramolecular nucleophilic
attack by the phenyl ligand on the CH2 terminus of the η3-
allyl group. Such an attack would be favored for a complex
having a relatively electrophilic allyl ligand attached to a less
electron rich tungsten center. Consistent with this view is the
fact that such isomerizations do indeed occur for Cp*W(NO)-
(R)(η3-allyl) complexes having relatively higher nitrosyl
stretching frequencies: e.g. entries 5, 6, and 9. Interestingly,
the electronic conditions in complexes 10* and 13* (entries 11
and 12) are such that subsequent multiple C−H activations
occur in both complexes, yet only complex 10* also undergoes
an alkyl hydrogen isomerization process. This observation
suggests that while an electronic influence is important for
multiple C−H activation processes, sterics still play a significant
role in the alkyl/aryl isomerizations. Apparently the decreased
steric congestion at the tungsten center of 13* as compared to
10* means that the isomerization pathway is sufficiently slowed
with respect to the multiple C−H activation route such that no
cyclohexylethyl analogue of 12* is formed.
Epilogue. In order to be of use in a practical sense, the C−
H activations initiated by these CpW(NO)(CH2CMe3)(η3-
allyl) complexes (Cp = Cp*, Cp′) must be selective and afford
single organometallic products in good yields. The results of
the investigations reported in this article have established that
single activations of arenes such as benzene are best effected
with the dimethylallyl complex Cp*W(NO)(CH2CMe3)(η3-
CH2CHCMe2) at 50 °C, whereas the specific activation of
terminal sp3 C−H bonds of alkanes are best effected with the
monomethylallyl complex Cp*W(NO)(CH2CMe3)(η3-
CH2CHCHMe) (1*) at ambient temperatures or with the
phenylallyl complex Cp*W(NO)(CH2 CMe3 )(η3 -
CH2CHCHPh) (7*) at 55 °C. The Cp′ analogues of the
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1H−13C HSQC, 1H−13C HMBC, and 13C APT experiments were
Cp* allyl complexes display similar C−H activation chemistry,
but at a slower rate, and the resulting Cp′W(NO)(η1-
hydrocarbyl)(η3-allyl) complexes exhibit greater thermal
stability at a particular temperature than do their Cp*
counterparts. These desirable C−H activating characteristics
correlate with the tungsten centers in the product compounds
being somewhat electron poor and exhibiting relatively higher
nitrosyl-stretching frequencies in their infrared spectra.
Reactions of the three Cp*W(NO)(CH2CMe3)(η3-allyl)
complexes at temperatures higher than those specified above
or with other hydrocarbon substrates begin to afford other
products, as summarized in Scheme 11. These other
compounds are (a) Cp*W(NO)(H)[η3-(hydrocarbyl)allyl]
complexes that are isomers of the CpW(NO)(η1-hydrocarbyl)-
(η3-allyl) compounds resulting from an intramolecular hydro-
carbyl/allylH exchange and (b) Cp*W(NO)(H)[η3-hydro-
carbyl] species that result from three successive C−H
activations of the hydrocarbon substrate and loss of the original
allyl ligand. Our current investigations are centered on releasing
the η1-hydrocarbyl ligands formed by the desired single C−H
activation processes from the tungsten’s coordination sphere in
an appropriately functionalized manner, and the results of these
studies will be reported in due course.
1
carried out to correlate and assign H and 13C NMR signals. Low-
resolution mass spectra (EI, 70 eV) were recorded by the staff of the
UBC mass spectrometry facility using a Kratos MS-50 spectrometer.
Elemental analyses were performed by Mr. David Wong of the UBC
microanalytical facility.
Synthesis of Cp′W(NO)(CO)2. In a glovebox, a three-neck round-
bottom flask was charged with NaCp′ (4.00 g, 27.7 mmol) and was
attached to a Schlenk line. To the flask was added THF (160 mL) by
cannulation under a flow of argon. W(CO)6 (9.90 g, 28.1 mmol) was
then added to the orange-yellow solution. The reaction mixture was
refluxed at 60 °C for a period of 3 days, during which time the solution
became dark brown-black. A 250 mL Schlenk tube was then charged
with Diazald (5.57 g, 26.0 mmol) and THF (75 mL), and the resulting
solution was added dropwise by cannula into the three-neck round-
bottom flask. The final mixture was stirred at ambient temperature for
1 h, whereupon it was transferred into a sublimation flask, and the
solvent was removed in vacuo. Sublimation of the residue at 80 °C
under dynamic vacuum resulted in the deposition of orange-red
crystals of Cp′W(NO)(CO)2 onto the cold finger (9.61 g, 89% yield).
Characterization Data for Cp′W(NO)(CO)2. IR (cm−1): 1660 (s,
1
νNO), 1917 (s, νCO), 1996 (s, νCO). H NMR (300 MHz, C6D6): δ
1.60 (s, 6H, Cp′Me), 1.67 (s, 6H, Cp′Me), 4.59 (s, 1H, Cp′H). 13C
APT NMR (100 MHz, C6D6): δ 10.5, 12.4 (C5Me4H), 88.6 (Cp′CH),
106.8 (Cp′CMe), 191.5, 222.8 (CO). Anal. Calcd for C11H13NO3W:
C, 33.78; H, 3.35; N, 3.58. Found: C, 33.58; H, 3.27; N, 3.42.
Synthesis of Cp′W(NO)Cl2. In a glovebox a Schlenk tube was
charged with PCl5 (2.348 g, 11.28 mmol) and a magnetic stir bar.
Under a flow of N2, Cp′W(NO)(CO)2 (4.439 g, 11.29 mmol) was
added to the Schlenk tube. The mixture was cooled to −196 °C with a
liquid N2 bath, and Et2O (ca. 100 mL) was slowly cannulated on top
of the solids. The initially orange contents were warmed to room
temperature while being stirred, and after 30 min at 20 °C a dark blue-
green solution had formed. The solvent was removed from the final
mixture in vacuo to obtain a dark blue-green crystalline solid. The solid
was washed twice with pentane (ca. 20 mL) to obtain Cp′W(NO)Cl2
(3.40 g, 74% yield).
EXPERIMENTAL SECTION
■
General Methods. All reactions and subsequent manipulations
involving organometallic reagents were performed under anhydrous
and anaerobic conditions under either high vacuum or an inert
atmosphere of prepurified dinitrogen or argon. Purification of inert
gases was achieved by passing them first through a column containing
MnO and then a column of activated 4 Å molecular sieves.
Conventional glovebox and Schlenk techniques were utilized
throughout. The gloveboxes utilized were Innovative Technologies
LabMaster 100 and MS-130 BG dual-station models equipped with
freezers maintained at −30 °C. All glassware was heated in an oven to
275 °C to remove any moisture and then cooled to room temperature
under vacuum. Most reactions were performed in thick-walled glass
vessels possessing Kontes greaseless stopcocks and side arm inlets for
vacuum-line attachment. Small-scale reactions and NMR spectroscopic
analyses were conducted in J. Young NMR tubes equipped with
Kontes greaseless stopcocks. All solvents were dried with appropriate
drying agents under a dinitrogen atmosphere and were distilled prior
to use, or they were transferred directly under vacuum from the
appropriate drying agent. Hydrocarbon solvents, pentane, diethyl ether
(Et2O), benzene, and benzene-d6 were dried over sodium/
benzophenone ketyl and freshly distilled prior to use. The syntheses
of (CH2CHCHPh)MgCl and (Me3CCH2)MgCl from cinnamyl
chloride and neopentyl chloride, respectively, and magnesium
(Strem) were performed in a manner similar to that described
previously for the preparation of other allyl- and alkylmagnesium
reagents, and they were transformed into the corresponding bis(allyl)-
and bis(alkyl)magnesium reagents in the usual manner.13 Cp*W-
(NO)(CH2CMe3)(η3-CH2CHCHMe) (1*) was prepared according
to the published procedure,5 and tetramethylcyclopentadiene was
obtained from the Boulder Scientific Co. All other chemicals were
ordered from commercial suppliers and were used as received. The
progress of most reactions was monitored by NMR spectroscopy, but
the isolated yields of all new complexes have not been optimized.
Unless otherwise specified, all IR samples were prepared as Nujol
mulls sandwiched between NaCl plates, and their spectra were
recorded on a Thermo Nicolet Model 4700 FT-IR spectrometer.
NMR spectra were recorded at room temperature on Bruker AV-300
or AV-400 instruments, and all chemical shifts and coupling constants
Characterization Data for Cp′W(NO)Cl2. IR (cm−1): 1615 (s, νNO).
1H NMR (300 MHz, C6D6): δ 1.42 (s, 6H, Cp′Me), 1.69 (s, 6H,
Cp′Me), 4.59 (s, 1H, Cp′H). 13C APT NMR (100 MHz, C6D6): δ 10.3,
12.1 (C5Me4H), 102.1 (Cp′CH), 119.5, 121.7 (Cp′CMe). MS (LREI,
m/z, probe temperature 150 °C): 407 [M+, 184W]. HRMS-EI (m/z):
[M+] calcd for 182WC9H13NO35Cl2 402.98564, found 402.98587.
Synthesis of Cp′W(NO)(CH2CMe3)(η3-CH2CHCHMe) (1′). A
Schlenk tube (ca. 250 mL) was charged with a magnetic stir bar,
Cp′W(NO)Cl2 (3.59 g, 8.84 mmol), and Mg(CH2CMe3)2·x(dioxane)
(titer 126 g/mol of R, 1.10 g, 8.70 mmol of R). The Schlenk tube and
its contents were then cooled to −196 °C with a liquid N2 bath, and
THF (90 mL) was cannulated dropwise into the Schlenk tube. The
reaction mixture was warmed to room temperature and was stirred for
1 h to obtain a purple solution of Cp′W(NO)(CH2CMe3)Cl. The
THF was then removed in vacuo, and the purple residue was extracted
with Et2O until the extracts were colorless (3 × 25 mL). The
combined extracts were cooled to −60 °C with a dry ice/acetone bath.
In the glovebox a separate Schlenk tube was charged with a magnetic
stir bar and Mg(CH2CHCHMe)2·x(dioxane) (titer 121 g/mol of R,
1.05 g, 8.70 mmol of R). The Schlenk tube and its contents were then
cooled in a liquid N2 bath. The purple Cp′W(NO)(CH2CMe3)Cl
solution was added dropwise via a cannula to the magnesium reagent
at a rate slow enough to allow the added solution to freeze upon
contact. The frozen mixture was transferred to a dry ice/acetone bath
and was stirred for 45 min after it had melted. The reaction mixture
gradually turned brown with the concomitant formation of a brown
suspension. The dry ice/acetone bath was removed, and the Et2O was
evaporated under reduced pressure. The remaining residue was
extracted with pentane (4 × 25 mL), and the extracts were transferred
to the top of an alumina (I) column (2 × 8 cm) made up in pentane
and supported on a medium-porosity frit. The column was eluted with
4/1 pentane/Et2O, and the yellow band that developed was eluted and
collected. The eluate was taken to dryness in vacuo, and the residue
1
are reported in ppm and in Hz, respectively. H NMR spectra were
referenced to the residual protio isotopomer present in C6D6 (7.16
ppm), and 13C NMR spectra were referenced to the natural-abundance
carbon signal of C6D6 (128.39 ppm). When necessary, 1H−1H COSY,
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was recrystallized from 4/1 pentane/Et2O at −30 °C to obtain 1′ as
[M+, 184W]. Anal. Calcd for C20H27NOW: C, 49.91; H, 5.65; N, 2.91.
Found: C, 49.16; H, 5.60, N, 2.90.
orange-yellow crystalline blocks (1.9 g, 47% yield).
1
Characterization Data for 1′. IR (cm−1): 1595 (s, νNO). H NMR
NMR Data for 2b*. 1H NMR (400 MHz, C6D6): δ 0.53 (d, 3JHH
=
3
(400 MHz, C6D6): selected signals δ 1.02 (m, 1H, allyl CHCH3), 1.06
(d, 2JHH = 13.8, 1H, CH2Me3), 1.32 (obscured, 1H, allyl CH2), 1.34 (s,
9H, CH2Me3), 1.39 (s, 3H, Cp′Me), 1.40 (s, 3H, Cp′Me), 1.55 (s, 3H,
Cp′Me), 1.67 (obscured, 1H, CH2Me3), 1.69 (s, 3H, Cp′Me), 1.90 (d,
3JHH = 5.5, 3H, allyl CH3), 3.61 (d, 3JHH = 6.3, 1H, allyl CH2), 4.47 (s,
9.4, 1H, allyl CH2), 1.12 (d, JHH = 6.3, 3H, allyl Me), 1.66 (m, 1H,
3
allyl CHMe), 1.43 (s, 15H, C5Me5), 2.38 (d, JHH = 6.7, 1H, allyl
CH2), 5.17 (ddd, 3JHH = 13.3, 9.4, 6.7, 1H, allyl CH), 7.09 (m, 2H, aryl
H), 7.23 (m, 2H, aryl H), 7.73 (m, 1H, aryl H). 13C APT NMR (100
MHz, C6D6): δ 10.6 (C5Me5), 18.0 (allyl Me), 44.2 (allyl CH2), 93.9
(allyl CHMe), 107.8 (C5Me5), 113.2 (allyl CH), 126.1 (aryl C), 129.6
(aryl C), 143.6 (aryl C), 164.8 (ipso C).
3
1H, Cp′H), 4.97 (ddd, JHH =14.1, 9.0, 6.3, 1H, allyl CH). 13C APT
NMR (100 MHz, C6D6) δ 9.6, 10.0, 11.3, 11.4 (Cp′ Me), 17.4 (allyl
CH3), 26.9 (CH2Me3), 35.0 (CH2Me3), 51.9 (allyl CH), 73.2 (allyl
CH2), 101.0 (Cp′ CH), 104.8, 106.0, 107.0, 111.1 (Cp′ CMe), 114.5
(allyl CH). (MS (LREI, m/z, probe temperature 100 °C) 461 [M+];
HRMS-EI (m/z): [M+] calcd for 186WC18H31NO 463.19535, found
463.19494. Anal. Calcd for C18H31NOW: C, 46.87; H, 6.77; N, 3.04.
Found: C, 45.47; H, 6.54; N, 2.84. Elemental analysis for carbon
content was consistently lower than the calculated value. This may be
due to incomplete combustion of the solid.
Spectroscopic Detection of Cp′W(NO)(H)(η3-CH(Me)-
CHCHPh) (3′) and Cp′W(NO)(H)(η3-CH2CHC(Me)Ph) (4′). Com-
plexes 3′ and 4′ were generated in situ by the thermolysis of 1′ (46 mg,
0.099 mmol) in C6D6 at 35 °C for 36 h in a J. Young NMR tube. The
1H NMR spectrum of the final mixture exhibited signals due to
hydride ligands at δ −0.56 (1JWH = 124 Hz) and 0.02 (1JWH = 127 Hz)
that can be assigned to 3′ and 4′, respectively, by analogy to 3* and 4*
(vide infra).
Preparation of Cp′W(NO)(Ph)(η3-MeCHCHCH2) (2a′,b′). A 4
dram vial was charged with a sample of 1′ (46 mg, 0.099 mmol) and
freshly distilled benzene (5 mL). The reaction mixture was allowed to
sit undisturbed at room temperature for a period of 48 h, during which
time the initially orange solution turned dark brown. The solvent was
then removed from the final reaction mixture in vacuo, the resulting
oily brown residue was redissolved in a minimum of 3/1 pentane/
Et2O, and the solution was chromatographed on an alumina column
(1 × 4 cm) using a 2/1 pentane/Et2O mixture as the eluent. The
yellow band that developed was eluted and collected, and the solvent
was removed from the eluate in vacuo to obtain a yellow oil. Crystals
containing both 2a′ and 2b′ (24 mg, 51% yield) were grown by
dissolving the yellow oil in a minimal amount of pentane and storing
the solution at −30 °C.
Preparation of Cp*W(NO)(H)(η3-CH(Me)CHCHPh) (3*) and
Cp*W(NO)(H)(η3-CH2CHC(Me)Ph) (4*). Complexes 3* and 4* were
prepared by the thermolysis of 1* (121 mg, 0.255 mmol) in C6H6 (4
mL) at 45 °C for 24 h. The solvent was removed from the final
reaction mixture in vacuo to obtain an oily residue that was transferred
to the top of an alumina column (0.5 × 6 cm) made up in pentane. A
dark yellow band was eluted from the column with a 5/1 pentane/
Et2O mixture to obtain a yellow eluate. The solvents were removed
from the eluate under vacuum, the resulting residue was dissolved in a
minimal amount of pentane, and the solution was maintained at −30
°C for 2 h to induce the deposition of a yellow solid that contained 3*
and 4* in a 1/3 ratio (80 mg, 65% yield). Yellow hedgehog-like
crystals of 4* were obtained by recrystallization of this solid from
pentane at −30 °C over 3 days.
IR (C6D6, cm−1): 1590 (s, νNO). MS (LREI, probe temp 100 °C, m/
z): 467 [M+]. Anal. Calcd for C19H25NOW: C, 48.84; H, 5.39; N, 3.00.
Found: C, 48.53; H, 5.36; N, 2.98.
Characterization Data for 4*. IR (cm−1): 1588 (s, νNO). 1H NMR
1
(400 MHz, C6D6): δ −0.05 (s, JWH = 127, 1H, WH), 1.59 (s, 15H,
C5Me5), 2.17 (s, 3H, allyl Me), 2.50 (d, 3JHH = 7.8, 1H, allyl CH2), 2.82
NMR Data for 2a′. 1H NMR (300 MHz, C6D6): selected signals δ
3
3
(d, JHH = 13.3, 1H, allyl CH2), 3.50 (dd, JHH = 13.3, 7.8, 1H, allyl
CH), 7.01 (m, 2H, aryl H), 7.12 (m, 2H, aryl H), 7.49 (m, 1H, aryl H).
13C APT NMR (100 MHz, C6D6): δ 10.7 (C5Me5), 24.4 (allyl Me),
3
1.88 (d, JHH = 5.5, 3H, allyl Me), 3.50 (d, 3JHH = 7.0, 1H, allyl CH2),
4.85 (s, 1H, Cp′H), 5.06 (m, 1H, allyl CH). 13C APT NMR (75 MHz,
C6D6): δ 10.6, 9.7, 9.4, 9.2 (C5Me4H), 16.9 (allyl Me), 56.1 (allyl
CHMe), 73.5 (allyl CH2), 114.1 (allyl CH), 123.6 (aryl C), 127.3 (aryl
C), 143.7 (aryl C), 155.2 (ipso C).
42.7 (allyl CH2), 94.7 (allyl CH), 98.2 (allyl C), 104.6 (C5Me5), 126.7
(aryl C), 128.7 (aryl C), 129.0 (aryl C), 146.9 (ipso C). MS (LREI, m/
z, probe temperature 150 °C): 481 [M+, 184W]. Anal. Calcd for
C20H27NOW: C, 49.91; H, 5.65; N, 2.91. Found: C, 49.05; H, 5.54; N,
2.94.
NMR Data for 2b′. 1H NMR (400 MHz, C6D6): δ 0.53 (d, 1H, allyl
3
CH2), 1.02 (d, JHH = 5.5, 3H, allyl Me), 1.66 (m, 1H, allyl CHMe),
3
3.26 (d, JHH = 7.0, 1H, allyl CH2), 4.65 (s, 1H, Cp′H), 5.06 (m, 1H,
Selected Signals Attributable to 3*. 1H NMR (400 MHz, C6D6): δ
−0.63 (s, 1JWH = 124, 1H, WH), 1.69 (s, 15H, C5Me5), 5.22 (dd, 3JHH
= 12.9, 9.4, 1H, allyl CH). 13C APT NMR (100 MHz, C6D6): δ 10.9
(C5Me5), 105.1 (C5Me5), 106.1 (allyl CH).
allyl CH). 13C APT NMR (75 MHz, C6D6): δ 11.7, 11.2, 11.1, 10.9
(C5Me4H), 17.3 (allyl Me), 42.1 (allyl CH2), 93.4 (allyl CHMe), 111.6
(allyl CH), 123.2 (aryl C), 128.4 (aryl C), 142.7 (aryl C), 161.8 (ipso
C).
Preparation of Cp*W(NO)(Ph)(η3-CH2CHCHMe) (2a*,b*). A
sample of 1* (88 mg, 0.185 mmol) was transferred into a 4 dram vial
and dissolved in C6H6 (ca. 2 mL) to obtain an orange solution. The
reaction mixture was left at room temperature for 24 h, during which
time it turned brown. The solvent was removed in vacuo, the resulting
oil was dissolved in pentane, and the solution was transferred to the
top of an alumina column (0.5 × 5 cm). A yellow band was eluted
from the column with a 3/1 pentane/Et2O mixture to obtain a dark
yellow eluate. Removal of solvent from the eluate under reduced
pressure afforded a yellow solid (69 mg, 77% yield). A 1H NMR
spectrum of the solid revealed the presence of compounds 2a*,b*, 3*,
and 4*. Slow recrystallization of the solid from pentane at −30 °C
afforded large orange crystals consisting of only compound 2a*.
Characterization Data for 2a*. IR (cm−1): 1604 (s, νNO). 1H
NMR (400 MHz, C6D6): δ 1.24 (m, 1H, allyl CHMe), 1.45 (s, 15H,
C5Me5), 1.88 (d, JHH = 5.9, 3H, allyl Me), 2.01 (d, JHH = 13.7, 1H,
allyl CH2), 3.58 (d, 3JHH = 7.4, 1H, allyl CH2), 5.08 (ddd, 3JHH = 13.7,
9.8, 7.4, 1H, allyl CH), 7.11 (m, 2H, aryl H), 7.21 (m, 2H, aryl H),
7.74 (m, 1H, aryl H). 13C APT NMR (100 MHz, C6D6): δ 10.3
(C5Me5), 17.3 (allyl Me), 57.7 (allyl CHMe), 75.6 (allyl CH2), 107.9
(C5Me5), 115.3 (allyl CH), 124.3 (aryl C), 127.6 (aryl C), 144.2 (aryl
C), 158.1 (ipso C). MS (LREI, m/z, probe temperature 150 °C): 481
Monitoring the Conversions of 1 to 2a,b. Complex 1 (either 1′
(40 mg, 0.087 mmol) or 1* (50 mg, 0.105 mmol)) was dissolved in
C6D6 (0.8 mL) to obtain a yellow-orange solution that was then
transferred into a J. Young NMR tube. The 1H NMR spectrum of the
solution was recorded periodically, and the area under the doublet at δ
3.61 (d, 1H, allyl CH2) for 1′ and the meso peak at δ 4.97 (ddd, 1H,
allyl CH) of 1* was integrated against the signal at 7.16 ppm
corresponding to the residual protio isotopomer present in C6D6,
which was referenced to 10. These NMR monitoring experiments
were performed at approximately 10 °C intervals ranging from 25 to
55 °C for each complex and were continued over a period of 24 h at
each temperature in order to determine the rate constant, k, at that
temperature.
Preparation of Cp′W(NO)(CH2(CH2)3CH3)(η3-CH2CHCHMe)
(5′). In a glovebox, a sample of 1′ (73 mg, 0.158 mmol) was dissolved
in n-pentane (6 mL) in a 4 dram vial. The mixture was allowed to sit
undisturbed for 24 h at room temperature, after which time the solvent
was removed in vacuo. The resulting orange-brown residue was
redissolved in pentane (10 mL) and chromatographed on an alumina
(I) column (1 × 4 cm) using pentane as the eluent. The yellow band
that developed was collected, and the solvent was removed from the
eluate in vacuo. The yellow residue was recrystallized from pentane/
3
3
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Et2O (2/1) to obtain yellow hedgehog-like crystals of 5′ (55 mg, 75%
The THF was removed under reduced pressure to obtain a dark red
yield).
oily residue. A second Schlenk flask was charged with
1
Characterization Data for 5′. IR (cm−1): 1600 (s, νNO). H NMR
(CH2CHCHPh)2Mg·x(dioxane) (titer 2340 mL/mol of R, 11.6 mL,
4.96 mmol of R). The red oil in the first Schlenk flask was dissolved in
Et2O, and the solution was cannulated over to the second Schlenk flask
at −78 °C. The reaction mixture was stirred for 1 h, whereupon a dark
red solution was obtained. The solvent was removed in vacuo to
obtain a dark red residue. The residue was dissolved in 1/1 pentane/
Et2O, and the solution was chromatographed on an alumina column
(2 × 6 cm). A pale red band was eluted from the column, and the
eluate was concentrated in vacuo to a red oil which was recrystallized
from pentane at −30 °C overnight to obtain X-ray-quality crystals of 7′
(250 mg, 9.7% yield).
(300 MHz, C6D6): δ 1.05 (m, 1H, allyl CHCH3), 1.33 (s, 3H, Pentyl
CH3) 1.43, 1.50, 1.60, 1.61 (s, 3H, Cp′Me4) 1.95 (d, JHH = 5.6, 3H,
3
3
allyl CH3), 3.14 (d, JHH = 7.0, 1H, allyl CH2), 4.51 (s, 1H, Cp′CH),
4.89 (ddd, JHH =13.7, 9.4, 7.0, 1H, allyl CH). 13C APT NMR (75
3
MHz, C6D6): δ 10.08, 11.73 (C5Me4H), 15.5 (pentyl CH3), 18.6 (allyl
CH3) 14.8, 23.8, 35.1, 40.8 (pentyl CH2), 53.8 (allyl CHCH3), 73.7
(allyl CH2), 99.6 (C5Me4H), 105.6, 106.6, 107.1, 108.2 (Cp′Me4),
110.7 (allyl CH). MS (LREI, probe temp 100 °C, m/z): 461 [M+].
Anal. Calcd for C18H31NOW: C, 46.87; H, 6.77; N, 3.04. Found: C,
46.90; H, 6.56; N, 3.12.
Synthesis of Cp′W(NO)(CH2(CH2)2CH2Cl)(η3-MeCHCHCH2)
(6′). In a glovebox, complex 1′ (74 mg, 0.160 mmol) was dissolved
in 1-chlorobutane (3 mL) in a 4 dram vial. The mixture was allowed to
sit undisturbed for 24 h at room temperature, after which time the
solvent was removed in vacuo. The resulting orange-brown residue
was redissolved in pentane (9 mL), and the solution was chromato-
graphed on an alumina (I) column (1 × 4 cm) using 4/1 pentane/
Et2O (20 mL) as the eluent. The yellow band that eluted was
collected, and the solvent was removed from the eluate in vacuo.
Yellow rod-shaped crystals of 6′ (20 mg, 26% yield) were obtained by
recrystallizing the yellow residue from a minimal amount of pentane (2
mL) at −30 °C.
1
Characterization Data for 7′. IR (cm−1): 1600 (s, νNO). H NMR
(400 MHz, C6D6): δ 1.28 (s, 9H, CH2CMe3), 1.33 (s, 6H, C5Me4H),
1.40 (s, 3H, C5Me4H), 1.49 (s, 3H, C5Me4H), 2.50 (br s, 1H, allyl
CHPh), 3.63 (br s, 1H, allyl CH2), 4.63 (s, 1H, C5Me4H), 5.61 (br s,
1H, allyl CH), 7.05−7.25 (m, 5H, aryl H). 13C APT NMR (100 MHz,
C6D6): δ 10.0 (C5Me4H), 11.1 (C5Me4H), 20.1 (CH2CMe3), 35.1
(CH2CMe3), 39.4 (CH2CMe3), 126.4 (aryl C), 127.2 (aryl C), 128.5
(aryl C), 140.1 (ipso C). MS (LREI, m/z, probe temperature 150 °C):
523 [M+, 184W]. Anal. Calcd for C23H33NOW: C, 52.78; H, 6.36; N,
2.68. Found: C, 53.59; H, 6.18; N, 2.70.
Thermolysis of Cp′W(NO)(CH2CMe3)(η3-CH2CHCHPh) (7′) in
Benzene: Preparation of Cp′W(NO)(C6H5)(η3-CH2CHCHPh) (8′).
A sample of 7′ (302 mg, 0.577 mmol) was dissolved in benzene (ca. 5
mL) to obtain a deep orange solution that was transferred into a
Kontes flask. The solution was heated to 55 °C in a water/ethylene
glycol bath for 22 h. The solvent was then removed in vacuo to obtain
an orange oil that was washed with pentane and transferred to the top
of an alumina column (0.5 × 5 cm). An orange band was developed
with pentane and eluted from the column with Et2O. The solvents
were removed from the combined eluates in vacuo to obtain 8′ as an
orange solid (32 mg, 11% yield).
Characterization Data for 6′. IR (cm−1): 1601 (s, νNO). H NMR
1
(300 MHz, C6D6): δ 1.05 (m, 1H, allyl CHCH3) 1.39, 1.46, 1.56, 1.58
(s, 3H, Cp′Me4) 1.91 (d, 3JHH = 5.9, 3H, allyl CH3) 3.10 (d, 3JHH = 7.0,
1H, allyl CH2), 3.41 (m, 2H, CH2Cl), 4.47 (s, 1H, Cp′−H) 4.84 (ddd,
3JHH =13.7, 9.4, 7.0, 1H, allyl CH). 13C APT NMR (300 MHz, C6D6):
δ 9.1, 10.9 (C5Me4H), 12.0 (WCH2), 17.7 (allyl CH3), 31.4, 39.8,
(chlorobutyl CH2), 44.9 (CH2Cl), 53,2 (allyl CHCH3), 72.9 (allyl
CH2), 98.7 (C5Me4H), 105.7, 106.8, 107.2, 108.3 (Cp′Me4), 110.1
(allyl CH). MS (LREI, probe temp 100 °C, m/z): 481 [M+]. Anal.
Calcd for C18H30ClNOW: C, 42.39; H, 5.86; N, 2.91. Found: C, 40.86;
H, 5.69; N, 2.89. Elemental analysis for carbon content was
consistently lower than the calculated value. This may be due to
incomplete combustion of the solid.
1
Characterization Data for 8′. IR (cm−1): 1578 (s, νNO). H NMR
(600 MHz, C6D6): δ 1.18 (C5Me4H), 1.38 (C5Me4H), 1.41 (C5Me4H),
3
3
1.43 (C5Me4H), 2.21 (d, JHH = 12.9, 1H, allyl CH2), 2.67 (d, JHH
=
10.6, 1H, allyl CHPh), 3.48, (d, 3JHH = 7.4, 1H, allyl CH2), 4.68 (s, 1H,
C4Me4CH), 5.72 (ddd, JHH = 12.9, 10.6, 7.4, 1H, meso H), 7.14 (m,
2H, aryl H), 7.24 (t, JHH = 7.3, 2H, aryl H), 7.27 (t, JHH = 7.3, 2H,
aryl H), 7.32 (m, 1H, aryl H), 7.33 (m, 1H, aryl H), 7.74 (d, JHH
Thermolysis of Cp*W(NO)(CH2CMe3)(η3-CH2CHCHPh) (7*) in
Benzene: Preparation of Cp*W(NO)(H)(η3-PhHCCHCHPh) (9*).
A Kontes flask was charged with 7* (53.7 mg, 0.100 mmol) and
benzene (2 mL). The mixture was degassed at a vacuum line with
three freeze−pump−thaw cycles, and the flask was placed in a 75 °C
water−ethylene glycol bath for 1 day. The volatiles were removed in
vacuo from the final reaction mixture, and the yellow-brown residue
was redissolved in pentane. The pentane solution was transferred to
the top of an alumina column (6 × 0.5 cm) supported on glass wool in
a Pasteur pipet. A light yellow band was eluted from the column with
1/1 Et2O/pentane as eluent and was collected. Concentration of the
eluate followed by storage at −30 °C for 1 day induced the deposition
of Cp*W(NO)(H)(η3-PhHCCHCHPh) (9*) as yellow needles (42
mg, 75% yield).
3
3
3
3
=
7.3, 2H, aryl H). 13C APT NMR (150 MHz, C6D6): δ 9.7 (C4Me4CH),
10.2 (C4Me4CH), 10.8 (C4Me4CH), 11.4 (C4Me4CH), 64.6 (allyl
CHPh), 72.1 (allyl CH2), 104.4 (C4Me4CH), 105.9 (C4Me4CH), 106.4
(C4Me4CH), 107.9 (C4Me4CH), 111.1 (meso C), 114.2 (C4Me4CH),
124.3 (aryl CH), 128.1 (aryl CH), 129.01 (aryl CH), 129.07 (aryl
CH), 129.10 (aryl CH), 141.7 (allyl ipso C), 143.4 (aryl CH), 156.8
(phenyl ipso C). MS (LREI, m/z, probe temperature 120 °C): 529
[M+, 184W]. HRMS-EI (m/z): [M+] calcd for 184WC24H27NO 529.160
22, found 529.160 53; calcd for 182WC24H27NO 527.157 49, found
527.156 87.
Thermolysis of Cp′W(NO)(CH2CMe3)(η3-CH2CHCHPh) (7′) in
Benzene: Preparation of Cp′W(NO)(H)(η3-PhHCCHCHPh) (9′). A
sample of 7′ (204 mg, 0.390 mmol) was dissolved in benzene (ca. 5
mL) and transferred into a Kontes flask to give an orange solution.
The solution was heated to 55 °C in a water/ethylene glycol bath for 6
days, after which time the solvent was removed under reduced
pressure to obtain 9′ as an orange solid (82 mg, 40% yield).
Characterization Data for 9*. IR (cm−1): 1564 (s, νNO). 1H NMR
1
(400 MHz, C6D6): δ −0.15 (s, JWH = 124, 1H, WH), 1.61 (s, 15H,
3
3
C5Me5), 2.02 (d, JHH = 10.0, 1H, allyl PhCH), 2.74 (m, JHH = 12.6,
3
1H, allyl PhCH), 5.90 (dd, JHH = 12.6, 10.0, 1H, allyl CH), 7.00 (t,
3JHH = 7.6, 1H, para CH), 7.09 (t, JHH = 7.6, 1H, para CH), 7.16
3
(obscured, m, 2H meta CH), 7.33 (overlapping m, 4H, ortho and meta
CH), 7.55 (d, 3JHH = 7.6, 2H, ortho CH). 13C APT (100 MHz, C6D6):
δ 10.2 (C5Me5), 62.7 (allyl PhCH), 75.6 (allyl PhCH), 103.9 (allyl
CH), 105.0 (C5Me5), 125.3, 126.4, 127.1, 128.6, 128.7 (aryl C), 143.0,
145.1 (ipso C). MS (LREI, probe temperature 100 °C, m/z): 543
[M+]. Anal. Calcd for C25H29NOW: C, 55.26; H, 5.38; N, 2.58. Found:
C, 55.16; H, 5.28; N, 2.54.
1
Characterization Data for 9′. IR (cm−1): 1587 (s, νNO). H NMR
1
(400 MHz, C6D6): δ −0.08 (s, JWH = 10.2, 1H, W−H), 1.56 (s, 3H,
C5Me4H), 1.58 (s, 3H, C5Me4H), 1.59 (s, 3H, C5Me4H), 1.66 (s, 3H,
3
3
C5Me4H), 2.24 (d, JHH = 10.2, 1H, allyl CH), 2.90 (d, JHH = 12.5,
1H, allyl CH), 4.68 (s, 1H, C5Me4H), 5.90 (dd, 3JHH = 10.2,12.5, meso
H), 7.01 (t, JHH = 7.4, 1H, aryl H), 7.08 (t, JHH = 7.4, 2H, aryl H),
3
3
3
3
Preparation of Cp′W(NO)(CH2CMe3)(η3-CH2CHCHPh) (7′). A
Schlenk flask was charged with Cp′W(NO)Cl2 (2.700 g, 6.65 mmol)
and (CH2CMe3)2Mg·x(dioxane) (titer 126 g/mol of R, 0.63 g, 4.94
mmol of R). THF (ca. 50 mL) was cannulated into the Schlenk flask at
−196 °C, and the mixture was warmed in a dry ice/acetone bath at
−78 °C. A red solution first formed and then darkened to a black-red.
7.26 (t, JHH = 7.4, 1H, aryl H), 7.31 (t, JHH = 7.8, 2H, aryl H), 7.34
(d, 3JHH = 7.8, 2H, aryl H), 7.51 (d, 3JHH = 7.8, 2H, aryl H). 13C APT
NMR (100 MHz, C6D6): δ 10.5 (C5Me4H), 11.5 (C5Me4H), 11.9
(C5Me4H), 12.3 (C5Me4H), 61.5 (allyl CH), 74.7 (allyl CH), 93.8
(C5Me4H), 104.0 (meso C), 105.3 (C5Me4H), 106.3 (C5Me4H), 106.6
(C5Me4H), 108.1 (C5Me4H), 126.75 (aryl CH), 126.80 (aryl CH),
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Table 2. X-ray Crystallographic Data for Complexes 2′, 2a*, 4*, 9*, and 7′
2′
2a*
Crystal Data
4*
9*
7′
empirical formula
cryst habit, color
cryst size (mm)
cryst syst
C19H25NOW
needle, yellow
0.05 × 0.20 × 0.70
orthorhombic
Pbca
C20H27NOW
plate, orange
0.10 × 0.20 × 0.30
triclinic
C20H27NOW
plate, yellow
0.15 × 0.20 × 0.52
orthorhombic
Pbca
C27.5H35NOW
rectangular, yellow
0.40 × 0.20 × 0.12
orthorhombic
P212121
C23H33NOW
block, orange
0.25 × 0.15 × 0.15
monoclinic
P21/c
space group
V (Å3)
P1
̅
6961.9(6)
14.2940(8)
13.8238(7)
35.2329(17)
90
909.55(17)
8.4341(9)
8.4965(9)
14.4435(15)
85.138(5)
88.498(5)
61.891(4)
2
3663.9(4)
9.3285(6)
15.5488(9)
25.2601(16)
90
4812.5(10)
9.3219(9)
22.502(3)
22.943(3)
90
2084.45(15)
15.8750(7)
10.3935(4)
13.9479(6)
90
a (Å)
b (Å)
c (Å)
α (deg)
β (deg)
90
90
90
115.076(2)
90
γ (deg)
90
90
90
Z
16
8
8
4
calcd density (Mg/m3)
1.783
1.757
1.745
1.599
1.668
−1
abs coeff (mm )
6.639
6.335
6.310
4.819
5.553
F000
3648
472
1888
2312
1040
Data Collection and Refinement
no. of measd rflns
total
39 364
9277
21 333
5994
27 804
6792
38299
11491
4955
4955
unique
a
final R indices
R1
0.0253
0.0377
0.0270
0.0528
0.0326
wR2
0.0499
0.0872
0.0589
0.1140
0.0841
b
goodness of fit on F2
1.287
1.226
1.010
1.075
1.026
largest diff peak, hole (e Å−3)
1.575, −1.609
9.664, −5.073
2.985, −1.893
3.745, −2.270
1.580, −1.814
a
b
2 −1
R1 on F = ∑|(|Fo| − |Fc|)|/∑|Fo|; wR2 = = [(∑(Fo2 − Fc2)2)/∑w(Fo )2]1/2; w = [σ2Fo ] . GOF = [∑(w(|Fo| − |Fc|)2)/(degrees of freedom)]1/2
.
2
127.0 (aryl CH), 127.3 (aryl CH), 129.06 (aryl CH), 129.08 (aryl
CH), 143.27 (ipso C), 143.33 (ipso C). MS (LREI, m/z, probe
temperature 150 °C): 529 [M+]. HRMS-EI (m/z): [M+] calcd for
184WC24H27NO 529.160 22, found 529.159 33.
transferred to a Kontes flask. The mixture was heated at 55 °C in a
water/ethylene glycol bath for 4 days. The solvent was removed from
the final mixture in vacuo, and the resulting residue was dissolved in
1
C6D6. Complexes 14a*,b* were identified by comparison of their H
NMR spectra with those previously reported.12
Extended Thermolysis of 7* in Methylcyclohexane: Prep-
aration of Cp*W(NO)(η3-C7H11)(H) (11*) and Cp*W(NO)(H)(η3-
CH(CH2C6H11)CHCHPh) (12*). A Kontes flask was charged with 7*
(66 mg, 0.12 mmol) and methylcyclohexane (ca. 5 mL) to give an
orange suspension. The mixture was placed in a 55 °C water/ethylene
glycol bath for 4 days, whereupon it darkened in color. The volatiles
were removed in vacuo from the reaction mixture, and the resulting
residue was redissolved in a minimum of pentane and transferred to
the top of an alumina column (0.5 × 5 cm). An orange band was
developed with pentane and eluted with Et2O. The solvents were
removed from the dark orange eluate under reduced pressure to obtain
a mixture of complexes 11* and 12* (31 mg, 53% yield). Complex
11* was identified in the crude reaction mixture by comparison of its
1H NMR spectrum to that previously reported.12
1H NMR: 14a*, δ −0.92 (s, 1JWH = 125 Hz, 1H, WH), 1.71 (s, 15H,
C5Me5), 2.66 (dd, 3JHH = 7.83, 13.30, 1H, allyl CH); 14b*, δ −0.71 (s,
1H, WH), 1.76 (s, 15H, C5Me5), 2.69 (dd, 3JHH = 7.43, 11.74, 1H, allyl
CH).
Thermolysis of Cp*W(NO)(CH2CMe3)(η3-CH2CHCMe2) in n-
Pentane: Preparation of Cp*W(NO)(H)(η3-C5H9) Isomers
15a*,b*. A sample of Cp*W(NO)(CH2CMe3)(η3-CH2CHCMe2)
(85 mg, 0.17 mmol) was dissolved in pentane (ca. 5 mL) to produce a
bright orange solution. The contents were transferred to a glass
reaction flask equipped with a Kontes greaseless stopcock. The
reaction mixture was placed in an ethylene/glycol heating bath and
heated at 55 °C for 6 h to obtain a brown solution. Solvents were
removed in vacuo, and the remaining brown residue was dissolved in
pentane and transferred to the top of an alumina column (0.5 × 5 cm)
made up in pentane. A yellow band was eluted with 1/1 pentane/Et2O
to give a yellow eluate that was taken to dryness under reduced
pressure to obtain Cp*W(NO)(H)(η3-C5H9) as a yellow solid (42
Characterization Data for 12*. IR (cm−1): 1576 (s, νNO). 1H
1
NMR (600 MHz, C6D6): δ −1.10 (s, JWH = 119.2, 1H, W−H), 1.35
(obscured m, 1H, cyclic CH), 1.50 (m, 6H, cyclic CH), 1.58 (m, 2H,
cyclic CH), 1.69 (s, 15H, C5Me5), 1.77 (obscured m, 2H, cyclic CH),
1.81 (d, 3JHH = 9.7, 1H, allyl CH), 2.03 (d, 3JHH = 13.2, 1H, allyl CH),
1
mg, 58% yield). A H NMR spectrum of the final mixture in C6D6
3
3
revealed diagnostic signals attributable to two prominent isomers,
15a*,b*.
5.20 (dd, JHH = 9.7, 13.2, 1H, meso H), 7.08 (t, JHH = 7.4, 1H, aryl
H), 7.31 (t, 3JHH = 7.7, 2H, aryl H), 7.51 (d, 3JHH = 7.5, 2H, aryl H) .
13C APT NMR (150 MHz, C6D6): δ 10.7 (C5Me5), 23.3 (cyclic CH2),
23.7 (cyclic CH2), 27.0 (cyclic CH2), 33.4 (cyclic CH2), 35.7 (cyclic
CH2), 41.8 (cyclic CH2), 42.1 (cyclic CH2), 61.5 (allyl CH), 96.6 (allyl
CH), 100.5 (meso C), 104.8 (C5Me5), 125.5 (aryl CH), 127.5 (aryl
CH), 129.0 (aryl CH), 144.1 (ipso). MS (LREI, m/z, probe
temperature 150 °C): 563 [M+]. HRMS-EI (m/z): [M+] calcd for
182WC26H37NOl 561.235 74, found 561.235 22.
1H NMR: 15a*, δ −1.39 (s, 1JWH = 121.2, 1H, W−H), 1.75 (s, 15H,
C5Me5), 4.59 (ddd, 3JHH = 7.4, 10.6, 12.5, 1H, meso H); 15b*, δ −0.83
(s, 1JWH = 122.0, 1H, W−H), 1.73 (s, 15H, C5Me5), δ 4.44 (dd, 3JHH
=
9.8, 12.5, 1H, meso H). MS (LREI, m/z, probe temperature 150 °C):
419 [M+].
X-ray Crystallography. Data collection was carried out at −100
°C on a Rigaku AFC7/ADSC CCD diffractometer or at −170 2 °C
on a Bruker X8 or DUO APEX diffractometer, using graphite-
monochromated Mo Kα radiation.
Data for 2′ (mixture of 2a′ and 2b′) were collected to a maximum
2θ value of 58.4° in 0.5° oscillations. The structure was solved by
Extended Thermolysis of Cp*W(NO)(CH2CMe3)(η3-
CH2CHCHPh) (7*) in Ethylcyclohexane: Preparation of Cp*W-
(NO)(H)(η3-C7H13) Isomers 14a*,b*. In a glovebox a sample of 7*
was suspended in ethylcyclohexane, and the suspension was
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Organometallics
Article
direct methods14 and expanded using Fourier techniques. All non-
hydrogen atoms were refined anisotropically, and all hydrogen atoms
were included in fixed positions. The final cycle of full-matrix least-
squares analysis was based on 9277 observed reflections and 407
variable parameters.
Data for 2a* were collected to a maximum 2θ value of 63.3° in 0.5°
oscillations. The structure was solved by direct methods14 and
expanded using Fourier techniques. All non-hydrogen atoms were
refined anisotropically, and all hydrogen atoms were included in fixed
positions. The final cycle of full-matrix least-squares analysis was based
on 5994 observed reflections and 214 variable parameters.
Data for 4* were collected to a maximum 2θ value of 66.4° in 0.5°
oscillations. The structure was solved by direct methods14 and
expanded using Fourier techniques. All non-hydrogen atoms were
refined anisotropically; hydrogen atom H1 was refined isotropically,
and all other hydrogen atoms were included in fixed positions. The
final cycle of full-matrix least-squares analysis was based on 6792
observed reflections and 218 variable parameters.
Data for 9* were collected to a maximum 2θ value of 56.3° in 0.5°
oscillations. The structure was solved by direct methods14 and
expanded using Fourier techniques. The structure was a two-
component twin. The asymmetric unit contained two independent
molecules of 7* and a disordered pentane. Atom O2 was disordered
over two sites in a 52/48 ratio. The pentane was refined
anisotropically, but its disorder was not modeled. All non-hydrogen
atoms were refined anisotropically. Hydrogens H01 and H02 were
refined isotropically and their respective W−H distances and isotropic
displacement parameters constrained to be the same. All other
hydrogen atoms were included in fixed positions. The final cycle of
full-matrix least-squares analysis was based on 11 491 observed
reflections and 580 variable parameters.
Dr. Miriam Buschhaus for her assistance with the X-ray
crystallography.
REFERENCES
■
(1) See, for example: (a) Crabtree, R. H. J. Chem. Soc., Dalton Trans.
2001, 17, 2437. (b) Labinger, J. A.; Bercaw, J. E. Nature 2002, 417,
507. (c) Goldman, A., Goldberg, K. I., Eds. Activation and
Functionalization of C−H Bonds; American Chemical Society:
Washington, DC. 2004. (d) Fekl, U.; Goldberg, K. I. Adv. Inorg.
Chem. 2003, 54, 259. (e) Hartwig, J. F. Organotransition Metal
Chemistry: From Bonding to Catalysis; University Science Books:
Sausalito, CA, 2010; Chapter 18
(2) Tsang, J. Y. K.; Buschhaus, M. S. A.; Fujita-Takayama, C.; Patrick,
B. O.; Legzdins, P. Organometallics 2008, 27, 1634.
(3) For recent examplesof the selective functionalization of C−H
bonds, see: Crabtree, R. H. Chem. Rev. 2010, 110, 575and the reviews
in this specialissue..
(4) Ng, S. H. K.; Adams, C. S.; Hayton, T. W.; Legzdins, P.; Patrick,
B. O. J. Am. Chem. Soc. 2003, 125, 15210.
(5) Tsang, J. Y. K.; Buschhaus, M. S. A.; Graham, P. M.; Semiao, C.
J.; Semproni, S. P.; Kim, S. J.; Legzdins, P. J. Am. Chem. Soc. 2008, 130,
3652.
(6) Baillie, R. A.; Man, R. W. Y.; Shree, M. V.; Chow, C.; Thibault,
M. E.; McNeil, W. S.; Legzdins, P. Organometallics 2011, 30, 6201.
(7) Baillie, R. A.; Tran, T.; Thibault, M. E.; Legzdins, P. J. Am. Chem.
Soc. 2010, 132, 15160.
(8) Throughout this report the compounds being studied are
designated by bold numbers or letters. The symbols * and ′ after the
numbers or letters indicate the Cp*- and Cp′-containing complexes,
respectively. If no symbol is shown, then the designation encompasses
both the Cp* and the Cp′ compounds.
(9) As described in the Experimental Section, Cp′W(NO)
(CH2CMe3)(η3-CH2CHCHMe) can be synthesized in moderate
yields by utilizing the procedure reported for its Cp* analogue.5
(10) Semproni, S. P.; McNeil, W. S.; Baillie, R. A.; Patrick, B. O.;
Campana, C. F.; Legzdins, P. Organometallics 2010, 29, 867.
(11) Related η3-H2CCHCMe2 complexes also exhibit exo orienta-
tions of their allyl ligands.4
Data for 7′ were collected to a maximum 2θ value of 55.8° in 0.5°
oscillations. The structure was solved by direct methods14 and
expanded using Fourier techniques. The structure was a two-
component twin that was separated into its components using
Cell_Now,15 SAINTPLUS,16 and TWINABS.17 All non-hydrogen
atoms were refined anisotropically, and all hydrogen atoms were
included in fixed positions. The final cycle of full-matrix least-squares
analysis was based on 4955 observed reflections and 242 variable
parameters.
(12) Adams, C. S.; Legzdins, P.; Tran, E. J. Am. Chem. Soc. 2001, 123,
612.
For each structure neutral-atom scattering factors were taken from
Cromer and Waber.18 Anomalous dispersion effects were included in
Fc;19 the values for Δf ′ and Δf ′′were those of Creagh and McAuley.20
The values for mass attenuation coefficients are those of Creagh and
Hubbell.21 All calculations were performed using SHELXL-9722 via the
WinGX interface.23 X-ray crystallographic data for all five structures
are presented in Table 2, and full details of all crystallographic analyses
are provided in the Supporting Information.
(13) Pamplin, C. B.; Legzdins, P. Acc. Chem. Res. 2003, 36, 223.
(14) SIR-92: Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi,
A. J. Appl. Crystallogr. 1993, 26, 343.
(15) Cell_Now 2008/2; Bruker AXS Inc., Madison, WI.
(16) SAINTPLUS, Version 7.60A; Bruker AXS Inc., Madison, WI,
1997−2008.
(17) TWINABS, V2008/2; Bruker AXS Inc., Madison, WI, 2007.
(18) Cromer, D. T.; Waber, J. T. International Tables for X-ray
Crystallography; Kynoch Press: Birmingham, U.K., 1974; Vol. IV,
Table 2.2A.
(19) Ibers, J. A.; Hamilton, W. C. Acta Crystallogr. 1964, 17, 781.
(20) Creagh, D. C.; McAuley, W. J. International Tables for X-ray
Crystallography; Kluwer Academic: Boston, 1992; Vol. C, Table 4.2.6.8.
(21) Creagh, D. C.; Hubbell, J. H. International Tables for X-ray
Crystallography; Kluwer Academic: Boston, 1992; Vol. C, Table 4.2.4.3.
(22) SHELXL-97: Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112.
(23) WinGX-V1.70: Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837.
ASSOCIATED CONTENT
■
S
* Supporting Information
CIF files providing full details of the crystallographic analyses of
complexes 2′, 2a*, 4*, 9*, and 7′. This material is available free
of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: legzdins@chem.ubc.ca.
ACKNOWLEDGMENTS
■
We are grateful to The Dow Chemical Co. for continuing
support of this work, and we thank Drs. Pete Nickias and
Brandon Rodriguez for assistance and helpful discussions. We
also acknowledge the staff of the UBC High-Resolution NMR
facility, specifically Maria Ezhova and Zorana Danilovic, for
their assistance in obtaining the 600 MHz NMR spectra and
1067
dx.doi.org/10.1021/om201133r | Organometallics 2012, 31, 1055−1067