Molybdenum and Tungsten Alkylidene Complexes That Contain a 2-Pyridyl-Substituted Phenoxide Ligand

Article abstract of DOI:10.1021/acs.organomet.6b00644

In the interest of preparing molybdenum and tungsten alkylidene complexes for olefin metathesis that are longer-lived at high temperatures (～150 °C or above), we synthesized complexes that contain a phenoxide ligand with a 2-pyridyl in one ortho position and a mesityl (Mes) or 2,4,6-i-Pr₃C₆H₂ (Trip) in the other ortho position ([MesON]^- or [TripON]^-, respectively). The alkylidene (neophylidene) complexes that were prepared include W(O)(CHCMe₂Ph)(Me₂Pyr)(RON) (R = Mes or Trip), Mo(NC₆F₅)(CHCMe₂Ph)(RON)Cl, Mo(N-2,6-Me₂C₆H₃)(CHCMe₂Ph)(RON)Cl, Mo(N-t-Bu)(CHCMe₂Ph)(RON)Cl, and M(N-2,6-i-Pr₂C₆H₃)(CHCMe₂Ph)(TripON)(OTf) (M = Mo or W). The reaction between Mo(NAr)(CHCMe₂Ph)(TripON)(OTf) and ethylene yielded an ethylene complex, Mo(NAr)(C₂H₄)(TripON)(OTf)(ether). All neophylidene complexes were essentially unreactive toward terminal olefins at 22 °C and showed modest homocoupling activity (at 80 or 100 °C) and alkane metathesis activity (at 150 and 200 °C). W(O)(CHCMe₂Ph)(Me₂Pyr)(MesON) also stereoselectively polymerized several substituted norbornadienes at 100 °C.

Full text of DOI:10.1021/acs.organomet.6b00644

Article
pubs.acs.org/Organometallics
Molybdenum and Tungsten Alkylidene Complexes That Contain a
2‑Pyridyl-Substituted Phenoxide Ligand
Peter E. Sues, Jeremy M. John, Konstantin V. Bukhryakov, Richard R. Schrock,* and Peter Mu
̈
ller
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
S Supporting Information
*
ABSTRACT: In the interest of preparing molybdenum and tungsten alkylidene
complexes for olefin metathesis that are longer-lived at high temperatures (∼150 °C
or above), we synthesized complexes that contain a phenoxide ligand with a 2-pyridyl
in one ortho position and a mesityl (Mes) or 2,4,6-i-Pr C H (Trip) in the other
3
6
2
−
−
ortho position ([MesON] or [TripON] , respectively). The alkylidene (neophylidene)
complexes that were prepared include W(O)(CHCMe Ph)(Me Pyr)(RON) (R = Mes
2
2
or Trip), Mo(NC F )(CHCMe Ph)(RON)Cl, Mo(N-2,6-Me C H )(CHCMe Ph)-
6
5
2
2
6
3
2
(
RON)Cl, Mo(N-t-Bu)(CHCMe Ph)(RON)Cl, and M(N-2,6-i-Pr C H )(CHC-
2 2 6 3
Me Ph)(TripON)(OTf) (M = Mo or W). The reaction between Mo(NAr)(CHC-
2
Me Ph)(TripON)(OTf) and ethylene yielded an ethylene complex, Mo(NAr)
2
(
C H )(TripON)(OTf)(ether). All neophylidene complexes were essentially unreactive
2 4
toward terminal olefins at 22 °C and showed modest homocoupling activity (at 80 or
1
00 °C) and alkane metathesis activity (at 150 and 200 °C). W(O)(CHCMe Ph)-
2
(
Me Pyr)(MesON) also stereoselectively polymerized several substituted norborna-
2
dienes at 100 °C.
INTRODUCTION
We decided to test whether 16e alkylidene complexes
that contain a bidentate ligand in which a pyridine donor is
in one ortho position in a sterically demanding terphe-
noxide ligand would allow metathesis to proceed and also
would extend catalyst life at 150 °C or greater. To this
end, we prepared two such bidentate ligands which we
call [MesON]1 (2′,4′,5,6′-tetramethyl-3-(pyridin-2-yl)-
■
The synthesis of olefin metathesis catalysts that are relatively
stable and active above 150 °C would be potentially beneficial
for alkane metathesis, a catalytic reaction that employs an
iridium dehydrogenation/hydrogenation catalyst and an olefin
1
metathesis catalyst in tandem. The reason is that catalytic
−
activity is limited by decomposition of the metathesis cata-
lyst, not the iridium catalyst. In order to test whether 16e
molybdenum-based imido alkylidene complexes could be
active for metathesis at elevated temperatures, we synthesized
complexes that contain a dianionic pincer-type ligand (made first
1
−
[
1,1′-biphenyl]-2-olate) and [TripON]
(2′,4′,6′-triiso-
propyl-5-methyl-3-(pyridin-2-yl)-[1,1′-biphenyl]-2-olate;
Figure 1). These bidentate ligands could allow the required
2
by Bercaw; Figure 2); we proposed that the pyridine donor
might block one or more decomposition pathways (e.g., meta-
llacycle rearrangement to an olefin), even though dissociation
of the pyridine donor is likely to be necessary for reaction with
3
an olefin. We found that a six-coordinate metallacyclobutane
complex, Mo(NC F )(CH CH CH )(ONO), which is formed
6
5
2
2
2
from Mo(NC F )(CHCMe Ph)(ONO) upon reaction with
−
−
6
5
2
Figure 1. [MesON] and [TripON] ligands.
ethylene, is 5 or more orders of magnitude more stable toward
loss of ethylene than typical 14e trigonal bipyramidal meta-
4
TBP metallacycle structure to form through dissociation
llacycles. A tungsten-based oxo metallacyclobutane complex,
2
−
of the pyridyl donor, unlike the tridentate [ONO] ligand
shown in Figure 2. Here, we report syntheses of the MesON
or TripON ligands and several tungsten and molybde-
num alkylidene complexes that contain them, along with a
brief exploration of representative olefin metathesis reac-
tions.
W(O)(CH CH CH )(ONO), was similarly stable toward loss
2
2
2
of ethylene. We concluded that an olefin can be lost readily
only from a 14e TBP metallacycle, not a 16e pseudo-octahedral
metallacycle. The reason why this is the case, we propose, is
that an alkylidene/olefin intermediate with an electron count
two higher than that for the metallacyclobutane complex
(
and arguably a higher coordination number by one) must be
an intermediate or transition state on the path toward loss of
Received: August 12, 2016
olefin.
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.6b00644
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Article
Figure 2. [ONO]2− ligand.
RESULTS AND DISCUSSION
■
The two ligands were prepared by different routes. The
synthesis of H[TripON] starts with para-cresol, as shown
in Scheme 1. Modest selectivity for the desired mono-Trip
Addition of H[MesON] or H[TripON] to W(O)(CHC-
Me Ph)(Me Pyr) (PPhMe ) (where Me Pyr is 2,5-dimethyl-
2
2
2
2
2
5
pyrrolide), yielded two new tungsten oxo MAP (monoaryl-
oxide pyrrolide) complexes as a consequence of protonation of
one of the pyrrolide ligands, as shown in eq 1. The reaction
employing H[MesON] proceeded several times faster than the
reaction employing H[TripON] (∼16 h), as one might expect
on the basis of the larger size of H[TripON]. W(O)(CHC-
Me Ph)(Me Pyr)(MesON) (1(MesON)) and W(O)(CHC-
Scheme 1. Synthesis of H[TripON]
2
2
Me Ph)(Me Pyr)(TripON) (1(TripON)) were isolated in
2
2
moderate yields (∼50%) as bright yellow powders. NMR
spectra suggest that the alkylidene is in the syn orientation
in both 1(MesON) and 1(TripON) and the pyridyl is bound
strongly to the metal on the NMR time scale; both compounds
have C symmetry.
1
On the basis of the fact that H [ONO] (Figure 2) will
2
protonate imido groups in bisimido dialkyl precursors to
give alkylidene complexes, we proposed that protonated forms
of H[MesON] and H[TripON] might lead directly from
dineophyl to neophylidene complexes. Alkylidene formation
is the result of an irreversible α abstraction reaction after
double protonation of an imido ligand and loss of the aniline.
Treatment of H[MesON] and H[TripON] with an excess of
product was found upon coupling the diiodide with the
Grignard, but a significant amount of the disubstituted side
product and the diiodide starting material were present in the
crude reaction mixture. The pyridyl group was then installed
employing a Stille coupling with 2-(tributylstannyl)pyridine.
The Stille reaction did not proceed in good yield with an
analogous bromide.
A different approach had to be used to prepare H[MesON]
because the Kumada coupling between a mesityl Grignard and
the diiodo starting material shown in Scheme 1 gave largely the
undesired disubstituted product. The dibromide was prepared
from para-cresol, and the hydroxyl was converted to a methoxy,
as shown in Scheme 2. In this way, the mono mesityl product
could be prepared in modest yield (45%). The pyridyl group
was added in a high yielding Negishi coupling, followed by
deprotection with pyridinium chloride.
3
HCl in ether gave the HCl adducts, H [MesON]Cl and
2
H [TripON]Cl, respectively, as white powders in >90% yields.
2
Reactions between H [MesON]Cl or H [TripON]Cl and
2
2
Mo(NC F ) (CH CMe Ph) proceeded smoothly to give
6
5
2
2
2
2
Mo(NC F )(CHCMe Ph)(MesON)Cl (2(MesON)) and
6
5
2
Mo(NC F )(CHCMe Ph)(TripON)Cl (2(TripON)) in mod-
6
5
2
erate yields (62−75%) as yellow/brown powders (eq 2). As
found for 1(MesON) and 1(TripON) (vide supra), the NMR
spectra of 2(MesON) and 2(TripON) reveal that these
complexes have no symmetry. In contrast to 1(MesON) and
1
(TripON), 2(MesON) and 2(TripON) were present as
Scheme 2. Synthesis of H[MesON]
mixtures of syn and anti isomers (predominantly syn) in solution
with alkylidene resonances at 14.48 (JCH = 148 Hz, anti) and
1
3.31 (s, 1H, MoCH, J = 127 Hz, syn) ppm for 2(MesON),
CH
and 14.52 (J = 147 Hz, anti) and 13.39 (J = 127 Hz, syn)
CH
CH
ppm for 2(TripON).
An X-ray study of 2(MesON) shows that its structure is close
6
to a distorted square pyramid structure (τ = 0.12 ) with the
B
DOI: 10.1021/acs.organomet.6b00644
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Article
Figure 4. Thermal ellipsoid drawing (50% probability) of 3(TripON).
The solvent and most of the hydrogen atoms were removed for clarity.
Figure 3. Thermal ellipsoid drawing (50% probability) of 2(MesON).
The solvent and most of the hydrogen atoms were removed for clarity.
the pyridyl donor with a Cl(1)−Mo(1)−N(2) bond angle of
alkylidene ligand in the apical position (Figure 3). The complex
crystallizes as the syn isomer, in which Mo(1)−C(1)−C(2) =
1
66.3(1)°.
Treatment of H[TripON] with n-BuLi in ether/hexanes
yielded Li(ether)[TripON] in 80% yield. Reactions between
1
42.8(6)°. The imido and phenoxide ligands are trans to one
another with N(2)−Mo(1)−O(1) = 150.4(2)°, while Cl(1)−
Li(ether)[TripON] and W(NAr)(CHCMe Ph)(DME)(OTf)
2
2
Mo(1)−N(1) = 157.6(2)°.
(
(
(
(
Ar is 2,6-diisopropylphenylimido) or Mo(NAr)(CHCMe Ph)-
DME)(OTf)2 gave the monotriflate complexes, W(NAr)-
2
Attempts to extend the reactions shown in eq 2 to aryl- and
alkylimido precursors Mo(NAr ) (CH CMe Ph) and Mo(N-
Me 2
2
2
2
CHCMe Ph)(TripON)(OTf) (5(TripON)) and Mo(NAr)-
2
t-Bu) (CH CMe Ph) (where NAr = 2,6-dimethylphenyl-
2
2
2
2
Me
CHCMe Ph)(TripON)(OTf) (6(TripON)), in poor to mod-
2
imido) led to only ∼50% conversion of the starting material
and formation of a colorless precipitate in each case. The
erate yields (32−75%; eq 4). NMR spectra showed that both
5
(TripON) and 6(TripON) are unsymmetric and mixtures of
problem was traced to a deprotonation of H [MesON]Cl or
2
syn and anti isomers. In 5(TripON), the alkylidene is
H [TripON]Cl by the Ar NH or t-butylamine product as
2
Me
2
predominantly in the anti orientation with H resonances at
α
they are formed along with the metal-containing product in
each circumstance, thereby limiting conversion to 50%. The
problem was solved by employing 1 equiv of diphenylammoni-
um chloride along with H [MesON]Cl or H [TripON]Cl.
1
2.75 ppm (JCH = 144 Hz, anti) and 10.52 ppm (JCH = 114 Hz,
syn), while, in 6(TripON), the alkylidene is predominantly
syn with H resonances at 14.94 (J = 147 Hz, anti) and 13.29
α
CH
2
2
(
JCH = 119 Hz, syn) ppm.
In this manner, Mo(NArMe)(CHCMe Ph)(MesON)Cl
2
(
3(MesON)), Mo(NAr )(CHCMe Ph)(TripON)Cl (3(Trip-
Me 2
ON)), Mo(N-t-Bu)(CHCMe Ph)(MesON)Cl (4(MesON)),
2
and Mo(N-t-Bu)(CHCMe Ph)(TripON)Cl (4(TripON)) could
2
be prepared, although in relatively poor yields (25−30%; eq 3).
NMR spectra of all four again are characteristic of compounds that
have no symmetry. Compounds 3(MesON) and 3(TripON)
were found to be anti isomers in solution with alkylidene
resonances at 14.33 ppm (JCH = 146 Hz) and 14.35 ppm (JCH
46 Hz), respectively, whereas 4(MesON) and 4(TripON) were
found to be syn isomers with alkylidene resonances at 13.30 ppm
JCH = 125 Hz) and 13.31 ppm (JCH = 125 Hz).
=
1
(
A reaction between 6(TripON) and ethylene in diethyl ether
yielded the ethylene complex, Mo(NAr)(C H )(TripON)-
2
4
(
OTf)(ether) (7(TripON); eq 5), which could be isolated in
An X-ray structure of 3(TripON) (Figure 4) shows that the
metal center adopts a highly distorted structure approximately
halfway between a square pyramid and a trigonal bipyramid
57% yield. An X-ray structure of 7(TripON) (Figure 5) revealed
that the molybdenum center adopts a pseudo-octahedral
coordination geometry with the imido and phenoxide ligands
trans to one another. The Mo(1)−C(1) and Mo(1)−C(2) bond
lengths (2.200(6) and 2.193(6) Å, respectively) and C(1)−
C(2) bond length (1.40(1) Å) are similar to those in other
(
τ = 0.43). The complex crystallizes as the anti isomer
with Mo(1)−C(1)−C(2) = 127.6(3)°. The imido ligand is
found trans to the phenoxide with a N(1)−Mo(1)−O(1)
bond angle of 141.4(2)°, while the chloride ligand is trans to
4
molybdenum imido ethylene complexes of this general type.
C
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Article
Reactions between 7(TripON) and 40 equiv of 1-octene at
00 °C showed that 1-octene was isomerized to 2-, 3-, and
-octenes (according to GC). We also examined the reaction
1
4
of 7(TripON) with neat 1-octene after 4 days at 150 °C; the
reaction mixture was hydrogenated with 5% palladium on
carbon and shown by GC to contain a distribution of alkanes
between C and C , consistent with olefin metathesis in
7
14
addition to olefin isomerization. (Details can be found in the
Supporting Information.)
Complexes 1−6 were also tested for alkane metathesis
1
(
AM) with Ir(t-BuPOCOP)(C H ) (where t-BuPOCOP is
2
4
(
Me C) POC H OP(CMe ) ) as the dehydrogenation/hydro-
3
2
6
3
3 2
genation catalyst in a sealed J-Young tube in n-octane at 150 or
2
00 °C for 4 days. Only 1(MesON), 1(TripON), 4(TripON),
5
(TripON), and 6(TripON) showed any (all modest) AM
activity compared to reported activities with 14e initiators.
See the SI for details.) A distribution of alkane products was
seen (from C to C chains) with essentially no selectivity for
(
7
14
any given chain length.
Finally, we explored the polymerization of monomers A, B,
8
and C (Figure 6; 50 equiv in toluene-d ) with 1(MesON).
8
Figure 5. Thermal ellipsoid drawing (50% probability) of 7(TripON).
The solvent and most of the hydrogen atoms were removed for
clarity.
The formation of 7(TripON) establishes that no metal-
lacyclobutane complex that is relatively stable toward loss of
ethylene is formed in this system, unlike the system that
2
−
contains the [ONO] ligand (Figure 2) described earlier. The
metal is reduced either through bimolecular coupling of an
intermediate methylidene complex to give ethylene or through
rearrangement of the unsubstituted metallacyclobutane to pro-
pylene, which is then displaced by ethylene.
Figure 6. Monomers polymerized by 1(MesON).
Crystalline samples of 7(TripON) all had essentially
the same relatively complex NMR spectra consistent with
The polymerizations were extremely slow at 22 °C, but proceeded
smoothly at 100 °C (see the SI) over a period of 1 h to give
highly regular polymers in high yield according to their proton
and carbon NMR spectra. IR spectra suggested that the
polymers are not trans, and therefore, they must be cis,isotactic,
or cis,syndiotactic. It is not possible to assign the tacticity with
the data in hand. (See the SI.) We propose that dissociation of
the pyridyl donor at 100 °C exposes the 14e core to attack by
the monomer. Monomers A, B, and C were also polymerized
7
(TripON) having no symmetry. However, the spectra were
complicated further by the presence of another unsymmetric
complex (∼60% 7(TripON′) formed through dissociation of
ether from the metal in 7(TripON)). This proposal was
confirmed through HSQC NMR spectroscopy (see the SI),
where two sets of four ethylene proton resonances were
identified for the two different species. One equivalent of
free ether relative to 7(TripON′) was also present in the
NMR spectra.
by W(O)(CHCMe
Ph)(OHMT)(Me
Pyr)(PMe Ph) at 22 °C, but only polyA
Pyr) or W(O)(CHC-
2
2
Attempts to homocouple 1-hexene or 1-octene with com-
plexes 1−6 revealed that they are all essentially inactive at room
temperature. Homocoupling did proceed slowly at 80−120 °C
to give roughly 1:1 mixtures of cis and trans homocoupled
products (see the SI). However, some isomerization of the
terminal olefins to internal olefins was also observed. Olefin
isomerization is virtually unknown in metathesis reactions with
Mo and W catalysts at room temperature. However, at temper-
atures above 100 °C, it has been shown that olefin complexes,
which are plausible decomposition products of metathesis
catalysts, can slowly catalytically isomerize olefins, presumably7
through allylic CH activation and allyl/hydride intermediates.
They also can convert olefins of a given chain length into a
mixture of chain lengths through metathesis processes as a
consequence of formation of traces of one or more alkylidene
complexes from the olefin complexes in an as yet unknown
manner. One possibility is that metallacyclobutanes can also
form via an allyl hydride intermediate and then lose olefin to
yield an alkylidene.
Me Ph)(OHMT)(Me
2
2
2
had a regularity comparable to that found when 1(MesON)
was employed at 100 °C. The selectivity of these reactions
eroded with increasing steric bulk of the ring in the 7-position
of the three monomers (A−C).
CONCLUSION
■
1−
Complexes that contain an [RON] ligand (R = Mes or Trip)
have been prepared and isolated. In several cases, the alkylidene
can be prepared in a reaction between the dialkyl bisimido pre-
1
−
cursor and H [RON]Cl. Complexes that contain the [RON]
2
ligand reported here are more active in metathesis than com-
pounds previously published with the same electron count that
contain the [ONO]2 ligand. However, activity is still relatively
low compared to catalysts with 14 electron counts. We conclude
that coordination of the pyridyl group slows reactions to a
significant degree and that metathesis appears to be limited by
olefin isomerization at the high temperatures necessary for
significant rates. The polymerizations of A, B, and C confirm
−
3
D
DOI: 10.1021/acs.organomet.6b00644
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Organometallics
that ROMP can be stereoselective with [RON] complexes at
Article
−
layer, and washing the organic layer with 50 mL of saturated NaHCO ,
3
followed by 50 mL of brine. The organic layer was dried over
anhydrous MgSO . After 30 min, the mixture was filtered and the
100 °C.
4
solvent was removed from the filtrate using a rotary evaporator. The
yellow residue was stirred in MeOH for several hours to afford an off-
EXPERIMENTAL SECTION
■
General Considerations. All procedures and manipulations were
performed under an argon or nitrogen atmosphere using standard
Schlenk line and glovebox techniques unless stated otherwise. All
glassware was oven-dried or flame-dried prior to use unless stated
otherwise. Ether, pentane, toluene, dichloromethane, toluene, and ben-
zene were degassed with dinitrogen and passed through activated
alumina columns under nitrogen unless stated otherwise. All dried and
deoxygenated solvents were stored over molecular sieves in a nitrogen-
filled glovebox. Reagents were purchased from commercial sources and
used without further purification unless stated otherwise. Deuterated
solvents were purchased from Cambridge Isotope Laboratories. They
were degassed and dried over activated molecular sieves prior to use.
white solid; yield 0.7 g (56%). Anal. Calcd for [C21H21NO]: C, 83.13;
H, 6.98; N, 4.62. Found: C, 82.77; H, 7.05; N, 4.51.
Synthesis of 3-Iodo-2′,4′,6′-triisopropyl-5-methyl-[1,1′-bi-
phenyl]-2-ol. The product was synthesized via a modified procedure
1
5
reported by Wu et al. A suspension of 3.43 g of Mg (1.27 equiv,
0.141 mol) in 300 mL of THF was heated to reflux, and 40.00 g of
2-bromo-1,3,5-triisopropylbenzene (1.27 equiv, 0.141 mol) was added
dropwise. The resulting mixture was refluxed for 1 h, and then cooled
to room temperature. In another flask, a suspension of 2.81 g of 95%
wt NaH (1 equiv, 0.111 mol) in 150 mL of THF was cooled to 0 °C.
A solution of 40.00 g of 2,6-diiodo-4-methylphenol (1 equiv,
0.111 mmol) in 100 mL of THF was added slowly. The reaction
was stirred at room temperature for 20 min, and the clear yellow
2
-(Tributylstannyl)pyridine, W(O)(CHCMe Ph)(Me Pyr) (PPh-
2 2 2
Me ), W(O)(CHCMe Ph)(Me Pyr)(HMTO), W(O)(CHCMe Ph)-
solution was cooled to 0 °C. Pd(acac) (3.38 g, 0.1 equiv, 0.012 mol)
2
2
2
2
2
(
Me Pyr)(HMTO)(MeCN), W(O)(CHCMe Ph)(Me Pyr)-
was added as a powder. The mixture was stirred for 5 min, and a
solution of (2,4,6-triisopropylphenyl)magnesium bromide was added
via cannula while maintaining the temperature at 0 °C. The resulting
orange suspension was warmed to room temperature and stirred for
24 h. The solvent was removed, and 200 mL of water was added to the
residue, followed by 12 mL of 35% wt aq. HCl (1.3 equiv, 0.144 mol).
The aqueous solution was extracted with ethyl acetate (3 × 100 mL),
and the combined organic layers were dried over Na SO . The
2
2
2
(
HMTO)(PMe Ph), Mo(NAr)(CHCMe Ph)(DME)(OTf) ,
2
2
2
W(NAr)(CHCMe Ph)(DME)(OTf) , Mo(N-t-Bu) (DME)Cl , Mo-
2
2
2
2
(
NArMe)2(CH CMe Ph) , and Mo(NC F ) (CH CMe Ph) were
2 2 2 6 5 2 2 2 2
3
,5−9
synthesized according to literature procedures,
of the reported procedures for 2,6-dibromo-4-methylphenol,
2
methyl-1,1′-biphenyl, and 2,6-diiodo-4-methylphenol (see the
SI). NMR spectra were recorded on a Bruker 400 MHz spectrometer
or a Varian 500 or 300 MHz spectrometer at ambient temperature.
as were variations
10
1
1
,6-dibromo-4-methylanisole, 3-bromo-2-methoxy-2′,4′,5,6′-tetra-
12
2
4
13
solution was filtered, and the solvent was removed from the filtrate
using a rotary evaporator. The product was recrystallized from MeOH
at −20 °C to give a light gray powder; yield 21.8 g (45%). Anal. Calcd
for C H IO: C, 60.55; H, 6.70. Found: C, 59.47; H, 6.67.
1
13
The H and C NMR spectra were measured relative to proton
chemical shifts in partially deuterated NMR solvents, but are reported
relative to tetramethylsilane. All 19F chemical shifts were measured
relative to fluorobenzene (−113.15 ppm) as an external reference.
Elemental analyses were performed at the CENTC Elemental Analysis
Facility at the University of Rochester with a PerkinElmer 2400 Series
II CHN Analyzer.
22
29
Synthesis of 2′,4′,6′-Triisopropyl-5-methyl-3-(pyridin-2-yl)-
[
2
1,1′-biphenyl]-2-ol (H[TripON]). To a solution of 9.1 g of 3-iodo-
′,4′,6′-triisopropyl-5-methyl-[1,1′-biphenyl]-2-ol (1 equiv, 20.8 mmol)
and 9.2 g of 2-(tributylstannyl)pyridine (1 equiv, 20.8 mmol) in 100 mL
of toluene was added 1.2 g of Pd(PPh ) (0.05 equiv, 1.04 mmol). The
3
4
Synthesis of 2-(2-Methoxy-2′,4′,5,6′-tetramethyl-[1,1′-bi-
reaction mixture was refluxed for 36 h. The reaction was then cooled to
room temperature, and the solvent was removed in vacuo. The residue
was stirred in 50 mL of MeOH for 30 min, and the powder was filtered
off and washed with cold MeOH. The filtrate was cooled to −20 °C and
stood for several days. The product was filtered off and washed with
cold MeOH. The yellow precipitates were combined and dried under
high vacuum; yield 5.036 g (64%). Anal. Calcd for C H NO: C, 83.68;
phenyl]-3-yl)pyridinium Chloride. The product was synthesized
14
via a modified procedure reported by Yang et al. A solution of 1.49 g
of 2-bromopyridine (1.5 equiv, 9.40 mmol) in 10 mL of THF was
cooled to −78 °C, and 4 mL of 2.5 M n-BuLi in hexanes (1.58 equiv,
1
1
2
0.0 mmol) was slowly added. The reaction was stirred at −78 °C for
h, and then anhydrous 1.37 g of ZnCl (1.58 equiv, 10.0 mmol) in
2
27
33
0 mL of THF was added. The reaction was warmed to room
H, 8.58; N, 3.61. Found: C, 83.29; H, 8.87; N, 3.41.
temperature, and solutions of 2.00 g of 3-bromo-2-methoxy-2′,4′,5,6′-
tetramethyl-1,1′-biphenyl (1 equiv, 6.30 mmol) in 20.0 mL of THF
and a 1:1 premixed solution of 0.149 g of XPhos (0.05 equiv,
Synthesis of H [MesON]Cl. A round-bottom flask was charged
2
with 0.425 g of H[MesON] (1 equiv, 1.40 mmol) and suspended in
5
2
mL of ether with stirring. 2.5 mL of 1 M HCl in ether (1.8 equiv,
.50 mmol) was added, and the resulting slurry was stirred for 45 min.
0
.31 mmol, CAS 564483-18-7) in 5 mL of THF and 0.265 g of XPhos
Pd G3 (0.05 equiv, 0.31 mmol, CAS 1445085-55-1) in 5 mL of THF
were added. An equivalent volume of anhydrous NMP was then added
in one portion, and the reaction was heated at 110 °C for 24 h. The
reaction was cooled to room temperature, and the organic solvent was
removed under high vacuum. The crude residue was taken up in
The white precipitate was isolated by filtration, washed with cold ether,
and dried under high vacuum to yield a white solid; yield 0.432 g
(
90.7%). Anal. Calcd for C H ClNO: C, 74.22; H, 6.52; N, 4.12.
21 22
Found: C, 74.63; H, 6.69; N, 4.12.
Synthesis of H [TripON]Cl. A round-bottom flask was charged
2
1
00 mL of CH Cl and washed with 50 mL of saturated NH Cl and
2
2
4
with 0.477 g of H[TripON] (1 equiv, 1.23 mmol) and suspended in
50 mL of brine. The organic layer was dried over anhydrous MgSO4.
5
2
mL of ether with stirring. 2.5 mL of 1 M HCl in ether (2 equiv,
.50 mmol) was added, and the resulting slurry was stirred for 45 min.
The mixture was then filtered, and the solvent was removed from the
filtrate using a rotary evaporator. The crude product was passed
through a plug of silica. Residual impurities were removed through
precipitation of the acidified product from an acetone−hexane mixture
with excess 1.0 M HCl in ether; yield 2.0 g (90%). HRMS for
C H ClNO: Theoretical [M − Cl]: 318.1852. Found [M − Cl]:
The white precipitate was isolated by filtration, washed with cold ether,
and dried under high vacuum to yield a white solid; yield 0.495 g
(
94.9%). Anal. Calcd for C H ClNO: C, 76.48; H, 8.08; N, 3.30.
27 34
Found: C, 76.78; H, 8.25; N, 3.28.
22
24
Synthesis of Li[TripON]. A vial was charged with a solution of
.300 g of H[TripON] (1 equiv, 0.77 mmol) in 3 mL of ether. The
3
18.1850.
0
Synthesis of 2′,4′,5,6′-Tetramethyl-3-(pyridin-2-yl)-[1,1′-bi-
phenyl]-2-ol H[MesON]. A flask was charged with 2.0 g of
resulting yellow solution was cooled to −30 °C. A cold solution of
0.31 mL of 2.5 M n-BuLi in n-hexane was added, and the resulting
mixture was stirred at room temperature for 10 min. White precipitate
formed. The precipitate was filtered off, washed with cold pentane, and
dried under high vacuum to give the product as a white precipitate and
2
-(2-methoxy-2′,4′,5,6′-tetramethyl-[1,1′-biphenyl]-3-yl)pyridinium
chloride (1 equiv, 5.65 mmol) and excess pyridinium hydrochloride
(
∼15 g). The mixture was then heated to reflux for 30 min. The reac-
tion was allowed to cool to room temperature before dissolving
the resulting residue in 200 mL of a 1:1 mixture of CH Cl :H O. An
an etherate salt; yield 0.247 g (80%). Anal. Calcd for C H ClNO·
2
2
2
27 34
additional 50 mL of CH Cl was added before separating the aqueous
C H O: C, 79.62; H, 9.05; N, 3.00. Found: C, 79.19; H, 9.05; N, 2.88.
2
2
4
10
E
DOI: 10.1021/acs.organomet.6b00644
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Synthesis of 1[MesON]. A vial was charged with 0.1085 g of
(27.7%). Anal. Calcd for C H ClMoN O: C, 68.37; H, 6.03; N, 4.09.
Found: C, 68.74; H, 5.72; N, 4.59.
39
41
2
W(O)(CHCMe Ph)(Me Pyr) (PPhMe ) (1 equiv, 0.165 mmol), and
2
2
2
2
a solution of 0.050 g of H[MesON] (1 equiv, 0.165 mmol) in 5 mL
of benzene was added. The solution was stirred overnight, and the
solvent was removed in vacuo. The resulting residue was stirred in
Synthesis of 3(TripON). A vial was charged with 0.1417 g of
Mo(NArMe)2(CH Me Ph) (1 equiv, 0.236 mmol), and a suspension
2
2
2
of 0.100 g of H [MesON]Cl (1 equiv, 0.236 mmol) in 5 mL of
2
∼
6 mL of pentane for several hours, and the yellow powder was
filtered off, washed with pentane, and dried under high vacuum; yield
.0586 g (48.8%). Anal. Calcd for C H N O W: C, 61.00; H, 5.53;
benzene was slowly added. The solution was stirred for 4 h, and a
suspension of 0.0485 g of Ph NH Cl (1 equiv, 0.236 mmol) in 5 mL
2
2
0
of benzene was added slowly. The solution was stirred for an
additional 3 h and filtered. The solvent was removed under reduced
pressure, and the dark residue was triturated in ∼6 mL of pentane for
several hours. The orange precipitate was isolated by filtration, washed
with pentane, and dried under high vacuum. The product was
dissolved in ∼5 mL of ether, and the solution was filtered. The filtrate
was layered with 15 mL of pentane, cooled to −30 °C, and left at
−30 °C for several days. The crystalline yellow product was isolated by
filtration, washed with cold pentane, and dried in vacuo; yield 0.0487 g
(26.8%). Anal. Calcd for C H ClMoN O: C, 70.25; H, 6.94; N, 3.64.
43
52
2
2
N, 3.85. Found: C, 60.78; H, 5.44; N, 3.72.
Synthesis of 1[TripON]. A vial was charged with 0.0849 g of
W(O)(CHCMe Ph)(Me Pyr) (PPhMe ) (1 equiv, 0.129 mmol), and
2
2
2
2
a solution of 0.050 g of H[TripON] (1 equiv, 0.129 mmol) in 5 mL of
benzene was added. The solution was stirred overnight, and the
solvent was removed in vacuo. The resulting residue was stirred in
∼
4 mL of pentane for several hours, and the yellow powder was
filtered off, washed with pentane, and dried under high vacuum; yield
.0507 g (48.4%). Anal. Calcd for [C H N O W]: C, 63.55; H, 6.45;
0
43
52
2
2
45 53
2
N, 3.45. Found: C, 63.52; H, 6.41; N, 3.30.
Synthesis of Mo(N-t-Bu) (CH CMe Ph) . A suspension of 0.500 g
Found: C, 70.10; H, 6.98; N, 3.63.
Synthesis of 4(MesON). A vial was charged with 0.1246 g of
2
2
2
2
of Mo(N-t-Bu) (DME)Cl (1 equiv, 1.25 mmol) in 12 mL of ether
Mo(N-t-Bu) (CH CMe Ph) (1 equiv, 0.247 mmol), and a suspension
2
2
2
2
2
2
was cooled to −30 °C. To the chilled solution was added 5 mL of
of 0.100 g of H [MesON]Cl (1 equiv, 0.247 mmol) in 5 mL of
2
0
2
.5 M 2-methyl-2-phenylpropylmagnesium chloride in ether (2 equiv,
.5 mmol) slowly. The reaction was allowed to warm to room tem-
benzene was slowly added. The solution was stirred for 4 h, and a
suspension of 0.0605 g of Ph NH Cl (1 equiv, 0.247 mmol) in 5 mL
2
2
perature and left overnight. The reaction was filtered, and the solvent
was removed under reduced pressure. The oily residue was dissolved
in ∼10 mL of pentane, and the solution was chilled to −30 °C
overnight. The solution was filtered, and the solvent was removed in
vacuo. The crude product was used without further purification; yield
of benzene was added slowly. The solution was stirred for an
additional 3 h and filtered. The solvent was removed under reduced
pressure, and the dark residue was dissolved in ∼40 mL of pentane.
The solution was filtered and cooled to −30 °C for 2 days. The light
brown precipitate was isolated by filtration, washed with cold pentane,
and dried in vacuo. Half the solvent was removed from the filtrate,
and the solution was cooled to −30 °C for 2 days. The light brown
precipitate was isolated by filtration, washed with cold pentane, dried
under high vacuum, and combined with the previous crop to give a
total yield of 0.0386 g (24.5%). Anal. Calcd for C H ClMoN O:
0
.5873 g (92.9%).
Synthesis of 2(MesON). A vial was charged with 0.100 g of
2[MesON]Cl (1 equiv, 0.294 mmol), and a solution of 0.2132 g of
Mo(NC F ) (CH Me Ph) (1 equiv, 0.294 mmol) in 7 mL of benzene
6
5
2
2
2
2
was added. The solution was stirred for 4 h, and the solvent was
removed in vacuo. The resulting residue was stirred in ∼5 mL of
pentane for several hours, and the yellow solid was filtered off, washed
with pentane, and dried under high vacuum; yield 0.1648 g (75.0%).
According to NMR data (see the SI), syn and anti isomers were
present in a ratio of 94:6. Anal. Calcd for C H ClF MoN O: C,
35
41
2
C, 65.98; H, 6.49; N, 4.40. Found: C, 66.30; H, 6.18; N, 4.41.
Synthesis of 4(TripON). A vial was charged with 0.1417 g of
Mo(NArMe)2(CH CMe Ph) (1 equiv, 0.236 mmol), and a suspension
2
2
2
of 0.100 g of H [TripON]Cl (1 equiv, 0.236 mmol) in 5 mL of
2
benzene was slowly added. The solution was stirred for 4 h, and a
suspension of 0.0485 g of Ph NH Cl (1 equiv, 0.236 mmol) in 5 mL
37
32
5
2
59.49; H, 4.32; N, 3.75. Found: C, 59.33; H, 4.15; N, 3.64.
2
2
Synthesis of 2(TripON). A vial was charged with 0.100 g of
of benzene was added slowly. The solution was stirred for an addi-
tional 3 h and filtered. The solvent was removed under reduced
pressure, and the dark residue was stirred in approximately 6 mL of
pentane for several hours. The orange precipitate was isolated by
filtration, washed with pentane, and dried under high vacuum. The
product was dissolved in ∼5 mL of ether and filtered. The filtrate was
layered with 15 mL of pentane, cooled to −30 °C, and left for several
days. The crystalline yellow product was isolated by filtration, washed
with cold pentane, and dried under high vacuum; yield 0.0474 g
(27.8%). Anal. Calcd for C H ClMoN O·2CH CN: C, 67.28;
H [TripON]Cl (1 equiv, 0.236 mmol), and a solution of 0.1709 g of
2
Mo(NC F ) (CH Me Ph) (1 equiv, 0.236 mmol) in 7 mL of benzene
6
5
2
2
2
2
was added. The solution was stirred for 4 h, and the solvent was
removed in vacuo. The resulting residue was stirred in ∼5 mL of
pentane for several hours, filtered, washed with pentane, and dried
under high vacuum to yield a yellow solid; yield 0.1223 g (62.4%).
Syn and anti isomers were present in a ratio of 85:15. Anal. Calcd for
C H ClF MoN O: C, 62.13; H, 5.34; N, 3.37. Found: C, 62.00;
4
3
44
5
2
H, 5.26; N, 3.20.
Synthesis of 3(MesON). A vial was charged with 0.1485 g of
4
5
53
2
3
H, 7.40; N, 6.97. Found: C, 67.49; H, 7.53; N, 6.97.
Mo(NArMe)2(CH Me Ph) (1 equiv, 0.247 mmol) and a suspension
Synthesis of 5(TripON). A Schlenk flask was charged with 0.1567 g
2
2
2
of 0.100 g of H [MesON]Cl (1 equiv, 0.247 mmol) in 5 mL of
of W(NAr)(CHCMe Ph)(DME)(OTf) (1 equiv, 0.178 mmol), and a
2
2
2
benzene was slowly added. The solution was stirred for 4 h, and a
suspension of 0.0605 g of Ph NH Cl (1 equiv, 0.247 mmol) in 5 mL
solution of 0.100 g of Li[TripON] (1.2 equiv, 0.214 mmol) in 10 mL
of benzene was added. The flask was sealed, and the solution was
heated to 60 °C for 16 h. The solution was cooled to room temper-
ature and filtered through Celite, and the solvent was removed
under reduced pressure. The orange solid was dissolved in approxi-
mately 4 mL of pentane and decanted from the insoluble oily residue.
The solution was stirred for 1 h; the precipitate was isolated by
filtration, washed with cold pentane, and dried under high vacuum to
give the product as a pale orange powder; yield 0.0573 g (31.3%).
Syn and anti isomers were present in a 74:26 ratio. Anal. Calcd for
C H F N O SW: C, 58.48; H, 5.99; N, 2.73. Found: C, 58.21;
2
2
of benzene was added slowly. The solution was stirred for an
additional 3 h and filtered. The solvent was removed under reduced
pressure, and the dark residue was dissolved in ∼1 mL of dichlo-
romethane. The dichloromethane solution was layered with 15 mL of
pentane and cooled to −30 °C for 2 days. The dark orange solution
was decanted from the black oily residue and cooled to −30 °C. The
dark residue was dissolved in ∼3 mL of ether, and the mixture was
stirred for 1 h. The yellow precipitate was isolated by filtration, washed
with cold ether, and dried under high vacuum. The dark orange
solution yielded a mixture of yellow precipitate and black crystalline
solid after cooling for several days. The dark orange solution was
decanted, and the mixture of solids was dried under reduced pressure.
The solids were stirred in ∼2 mL of ether for 1 h. The yellow
precipitate was isolated by filtration, washed with cold ether, and dried
under high vacuum. The two crops of precipitate were combined to
give the desired product as a pale yellow powder; yield 0.0468 g
50
61
3
2
4
H, 5.94; N, 2.62.
Synthesis of 6(TripON). A vial was charged with 0.1693 g of
Mo(NAr)(CHCMe Ph)(DME)(OTf) (1 equiv, 0.214 mmol), and a
2
2
solution of 0.120 g of Li[TripON] (1.2 equiv, 0.257 mmol) in 10 mL
of benzene was added. The solution was stirred for 3 h and filtered
through Celite, and the solvent was removed under reduced pressure.
The dark residue was stirred in approximately 8 mL of pentane for
F
DOI: 10.1021/acs.organomet.6b00644
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
several hours; the precipitate was isolated by filtration, washed with
pentane, and dried under vacuum. The yellow precipitate was dis-
solved in 5 mL of benzene and filtered through Celite, and the solvent
was removed under reduced pressure. The residue was stirred in
Organometallics 2009, 28, 355−360. (c) Ahuja, R.; Kundu, K.;
Goldman, A. S.; Brookhart, M.; Vicente, B. C.; Scott, S. L. Chem.
Commun. 2008, 253−255. (d) Huang, Z.; Rolfe, E.; Carson, E. C.;
Brookhart, M.; Goldman, A. S.; El-Khalafy, S. H.; MacArthur, A. H. R.
Adv. Synth. Catal. 2010, 352, 125−135. (e) Haibach, M. C.; Kundu, S.;
Brookhart, M.; Goldman, A. S. Acc. Chem. Res. 2012, 45, 947−958.
(f) Dobereiner, G. E.; Yuan, J.; Schrock, R. R.; Goldman, A. S.;
Hackenberg, J. D. J. Am. Chem. Soc. 2013, 135, 12572−12575.
(g) Nawara-Hultzsch, A. J.; Hackenberg, J. D.; Punji, B.; Supplee, C.;
Emge, T. J.; Bailey, B. C.; Schrock, R. R.; Brookhart, M.; Goldman, A.
S. ACS Catal. 2013, 3, 2505−2514.
(2) (a) Agapie, T.; Henling, L. M.; DiPasquale, A. G.; Rheingold, A.
L.; Bercaw, J. E. Organometallics 2008, 27, 6245−6256. (b) Tonks, I.
A.; Meier, J. C.; Bercaw, J. E. Organometallics 2013, 32, 3451−3457.
(c) Agapie, T.; Bercaw, J. E. Organometallics 2007, 26, 2957−2959.
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∼
5 mL of pentane for 1 h; the precipitate was isolated by filtration,
washed with pentane, and dried under high vacuum to give the
product as a yellow powder; yield 0.144 g (71.7%). Syn and anti
isomers were present in a 24:76 ratio. Anal. Calcd for C H F Mo-
50
61 3
N O S: C, 63.95; H, 6.55; N, 2.98. Found: C, 63.77; H, 6.49; N, 2.92.
2
4
Synthesis of 7(TripON). A Schlenk flask was charged with a
suspension of 0.100 g of 6[TripON] (1 equiv, 0.106 mmol) in 5 mL of
ether and put under an atmosphere of ethylene. The solution was
stirred for 16 h, and the orange precipitate was washed with cold
pentane and dried under high vacuum. The filtrate was layered with
10 mL of pentane and cooled to −30 °C for several days. The resulting
orange crystals were isolated by filtration, washed with cold pentane,
and dried under high vacuum. The orange precipitate and crystals were
combined. In solution, the product is a mixture of the ether adduct and
the ether-free complex in a 40:60 ratio; yield 0.0549 g (57.0%).
Crystalline samples for elemental analysis consistently failed to give
acceptable values, perhaps as a consequence of loss of ether in the solid
state during shipping. Anal. Calcd for C H F MoN O S: C, 60.78;
6
123−6142. (e) Tonks, I. A.; Henling, L. M.; Day, M. W.; Bercaw, J. E.
Inorg. Chem. 2009, 48, 5096−5105.
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H.; Muller, P.; Schrock, R. R. J. Am. Chem. Soc. 2009, 131, 7770−7780.
d) Schrock, R. R.; Jiang, A. J.; Marinescu, S. C.; Simpson, J. H.;
Muller, P. Organometallics 2010, 29, 5241−5251.
(5) Townsend, E. M.; Hyvl, J.; Forrest, W. P.; Schrock, R. R.; Mu
P.; Hoveyda, A. H. Organometallics 2014, 33, 5334−5341.
6) Addison, A. W.; Rao, T. N.; Reedijk, J.; van Rijn, J.; Verschoor, G.
C. J. Chem. Soc., Dalton Trans. 1984, 1349−1356.
7) Marinescu, S. C.; King, A. J.; Schrock, R. R.; Singh, R.; Mu
Takase, M. K. Organometallics 2010, 29, 6816−6828.
8) (a) Peryshkov, D. V.; Schrock, R. R.; Takase, M. K.; Mu
Hoveyda, A. H. J. Am. Chem. Soc. 2011, 133, 20754−20757.
b) Peryshkov, D. V.; Schrock, R. R. Organometallics 2012, 31,
(
2
(
̈
ller, P. Organometallics
46
63
3
2
5
H, 6.99; N, 3.08. Found: C, 59.49; H, 6.78; N, 2.97.
̈
Polymerization of Monomers A, B, and C. In a J-Young tube,
0 equiv of the monomer (52.1 mg of A, 54.9 mg of B, and 57.7 mg
(
5
̈
of C) was added to 0.5 mL of toluene-d . A 0.5 mL solution of the
8
̈
ller,
initiator (2.8 mg, 4.0 μmol) in toluene-d was then added. The tube
8
was sealed and immersed into a preheated oil bath at 100 °C outside
(
the glovebox, and the progress of the reaction was monitored by
1
H NMR spectroscopy. After the monomer was consumed (1 h), the
(
̈
ller, P.;
viscous solution was exposed to air and the solution was added drop-
wise to 35 mL of methanol. The polymer was isolated by centri-
fugation and dried in vacuo. IR and NMR spectra can be found in the
SI. The rate of consumption of monomer was not zero, first, or second
order in monomer.
(
̈
ller, P.;
(
7
278−7286. (c) Forrest, W. P.; Axtell, J. C.; Schrock, R. R.
Organometallics 2014, 33, 2313−2325. (d) Forrest, W. P.; Weis, J.
G.; John, J. M.; Axtell, J. C.; Simpson, J. H.; Swager, T. M.; Schrock, R.
R. J. Am. Chem. Soc. 2014, 136, 10910−10913.
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the ACS
Publications website at DOI: 10.1021/acs.organomet.6b00644.
■
*
S
(
́ ́
9) (a) Hoang, T. N. Y.; Humbert-Droz, M.; Duronc, T.; Guenee, L.;
Besnard, C.; Piguet, C. Inorg. Chem. 2013, 52, 5570−5580.
(b) Schrock, R. R.; Murdzek, J. S.; Bazan, G. C.; Robbins, J.;
Crystallographic data for all X-ray structures (CIF)
Complete NMR data and spectra for all compounds, a
description of the structural studies of 2(MesON),
DiMare, M.; O’Regan, M. J. Am. Chem. Soc. 1990, 112, 3875−3886.
(c) Schrock, R. R.; DePue, R. T.; Feldman, J.; Yap, K. B.; Yang, D. C.;
Davis, W. M.; Park, L.; DiMare, M.; Schofield, M. Organometallics
1
990, 9, 2262−2275. (d) Fox, H. H.; Yap, K. B.; Robbins, J.; Cai, S.;
3(TripON), and 7(TripON), and a description of the
Schrock, R. R. Inorg. Chem. 1992, 31, 2287−2289. (e) Oskam, J. H.;
Fox, H. H.; Yap, K. B.; McConville, D. H.; O’Dell, R.; Lichtenstein, B.
J.; Schrock, R. R. J. Organomet. Chem. 1993, 459, 185−198.
polymerization of A, B, and C (PDF)
AUTHOR INFORMATION
Corresponding Author
E-mail: rrs@mit.edu.
̈
(10) Garcia, C. A. M.; Koch, E. K.; Lofstedt, A. J.; Cheng, A.;
■
Gordon, S.; Hansson, T. F. Novel pharmaceutical compositions. PCT
Int. Appl., 2007128492 A1, Nov 15, 2007.
*
(
11) Wang, X.; Snieckus, V. Tetrahedron Lett. 1991, 32, 4879−4882.
Notes
(12) Koch, F.; Schubert, H.; Sirsch, P.; Berkefeld, A. Dalton Trans.
The authors declare no competing financial interest.
2015, 44, 13315−13324.
13) (a) Omura, K. J. Org. Chem. 1984, 49, 3046−3050.
(b) Kometani, T.; Watt, D. S.; Ji, T.; Fitz, T. J. Org. Chem. 1985,
0, 5384−5387.
14) Yang, Y.; Oldenhuis, N. J.; Buchwald, S. L. Angew. Chem., Int. Ed.
013, 52, 615−619.
15) Wu, X.; Fors, B. P.; Buchwald, S. L. Angew. Chem., Int. Ed. 2011,
0, 9943−9947.
(
ACKNOWLEDGMENTS
■
5
(
2
(
R.R.S. is grateful for financial support from the National
Science Foundation under the CCI Center for Enabling New
Technologies through Catalysis (CENTC; CHE-1205189) and
the Department of Energy ((DE-FG02-86ER13564). We also
thank the NSF for support of X-ray diffraction instrumentation
5
(
CHE-0946721) and Yavin Jiang in the group of Prof. J.
Johnson (MIT chemistry) for GPC analyses.
REFERENCES
■
(
1) (a) Goldman, A. S.; Roy, A. H.; Huang, Z.; Ahuja, R.; Schinski,
W.; Brookhart, M. Science 2006, 312, 257−261. (b) Bailey, B. C.;
Schrock, R. R.; Kundu, S.; Goldman, A. S.; Huang, Z.; Brookhart, M.
G
DOI: 10.1021/acs.organomet.6b00644
Organometallics XXXX, XXX, XXX−XXX