Dimerization of ethylene by palladium complexes containing bidentate trifluoroborate-functionalized phosphine ligands

Article abstract of DOI:10.1021/om2004095

As an alternative to the widely reported phosphine-sulfonate ligand system, a series of potassium aryltrifluoroborate-functionalized phosphine ligands and zwitterionic phosphonium salts were prepared and structurally characterized. The phosphine ligands formed complexes of the general formula [κ²- (P,F)^RPdClMe] (where R = Ph, 2-OMe-Ph) when reacted with PdClMe(COD); however, cleavage of the chloride ligand proved problematic. Reaction of the phosphonium salts with PdMe₂(tmeda) yield complexes of the general type [κ-(P)^RPdMe(tmeda)], which react with pyridine derivatives to displace tmeda. Manipulation of the steric bulk of the pyridine ligands affords some control over the coordination mode of the fluoroborate phosphine, yielding facile access to complexes of the general type [κ²-(P, F)^RPdMe(lutidine)]. Investigations into the insertion chemistry of the palladium methyl moiety with simple small molecules revealed that the release of the lutidine ligand is slow and that insertion of ethylene occurs in a very slow manner; this is attributed to the relative electron deficiency of the aryltrifluoroborate moiety as compared to sulfonate. The palladium lutidine complexes slowly dimerize ethylene to a mixture of propene and butenes.

Full text of DOI:10.1021/om2004095

ARTICLE
pubs.acs.org/Organometallics
Dimerization of Ethylene by Palladium Complexes Containing
Bidentate Trifluoroborate-Functionalized Phosphine Ligands
Andrew L. Gott,† Warren E. Piers,*,† Jason L. Dutton,† Robert McDonald,‡ and Masood Parvez†
†Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, Alberta, T2N 1N4, Canada
‡Department of Chemistry, University of Alberta, 11227 Saskatchewan Drive, Edmonton, Alberta, T6G 2G2, Canada
S Supporting Information
b
ABSTRACT: As an alternative to the widely reported phosphineꢀ
sulfonate ligand system, a series of potassium aryltrifluoroborate-function-
alized phosphine ligands and zwitterionic phosphonium salts were prepared
and structurally characterized. The phosphine ligands formed complexes of
the general formula [k2-(P,F)RPdClMe] (where R = Ph, 2-OMe-Ph) when
reacted with PdClMe(COD); however, cleavage of the chloride ligand proved problematic. Reaction of the phosphonium salts
with PdMe2(tmeda) yield complexes of the general type [k-(P)RPdMe(tmeda)], which react with pyridine derivatives to displace
tmeda. Manipulation of the steric bulk of the pyridine ligands affords some control over the coordination mode of the fluoroborate
phosphine, yielding facile access to complexes of the general type [k2-(P,F)RPdMe(lutidine)]. Investigations into the inser-
tion chemistry of the palladium methyl moiety with simple small molecules revealed that the release of the lutidine ligand is
slow and that insertion of ethylene occurs in a very slow manner; this is attributed to the relative electron deficiency of the
aryltrifluoroborate moiety as compared to sulfonate. The palladium lutidine complexes slowly dimerize ethylene to a mixture of
propene and butenes.
’ INTRODUCTION
To this end, we recently reported a series of palladium-
(II)salicylaldiminato complexes II, related to a Ni-mediated
ethylene/acrylate copolymerization system reported by Grubbs
et al.5 The salicylaldimine framework was functionalized with a
trifluoroborate moiety in the para position of the aromatic ring;6
while kinetic studies showed that the rate of insertion of
acrylonitrile was indeed faster in the anionic complexes than in
their neutral counterparts, the effect was limited due to the
distant location of the BF3K moiety from the site of insertion.
The number of acrylonitrile insertions was also limited, due to
the coordination of the nitrile functionality to the Pd center, thus
forming catalytically inactive oligomeric structures consistent
with the independent observations of Jordan and co-workers.7 It
proved to be synthetically difficult to move the trifluoroborate
moiety into the ortho position of the aryl ring, and so we turned
our attention to other ligand systems for which the synthesis
could be readily altered to incorporate such groups. One such
system was the phosphineꢀsulfonate ligand system III, first
reported by Drent and co-workers8 A wealth of information is
available from studies on metal systems supported by such
ligands, and their reactivities with olefins,9 as well as numerous
polar monomers such as acrylonitrile,10 carbon monoxide,11
mixed N/O donors,12 acrylates,13 vinyl acetate,14 carboxylic
acids,15 sulfones,16 vinyl halides,17 polar allylic monomers18
and ethers,19 are well documented. The syntheses of such ligands
The development of organometallic compounds capable of
the copolymerization of ethylene and polar monomers is an area
of great current interest.1 Using the lessons learned from the
application of well-defined single-site olefin polymerization
catalysts, the synthesis of copolymers with novel properties that
could be rationally predicted and manipulated by appropriate
electronic and steric tuning of a well-defined catalyst would be a
significant breakthrough in the development of functionalized
polymeric materials. This is especially true in the case of
monomers such as acrylonitrile, where polymerization takes
place via either radical2 or anionic3 processes.
To reach this goal, numerous challenges to the improvement
of catalysts capable of mediating such a process exist. Chief
among them is the unwanted binding of the polar monomer to
the transition element center via the polar group, at the expense
of the ethylene comonomer. While this can be mitigated to
some extent by the choice of a later transition element over an
earlier one, the fact remains that electrophilic complexes
employed in such processes strongly bind comonomers with
“hard” donor groups as ligands, forming species inert to further
insertion. To circumvent such an issue requires promotion of
the π-bound isomer Ia at the expense of the σ-bound complex
Ib (Chart 1). One such line of investigation is the incorporation
of bulky, anionic functionalities into ligand frameworks—thus
making overall monoanionic complexes—which would result
in the repulsion of the lone pairs of the polar monomer, thus
promoting the binding of the polar monomer in the π-coordi-
nation mode.4
Received: May 17, 2011
Published: July 19, 2011
r
2011 American Chemical Society
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Chart 1
Scheme 1
are relatively simple and amenable to alteration, and complexa-
tion is facile.
This contribution details our findings in the replacement of
the sulfonate moiety in phosphineꢀsulfonate ligand systems
with a trifluoroborate group, and the effect such a group has on
coordination chemistry and reactivity.
the enhanced solubility of 2a allowed structural characterization by
X-ray crystallography, and the structure can be seen in Figure S2,
along with selected metrical data. Ligand 2b can be accessed
similarly.
Palladium Complexes of Aryltrifluoroborates. NMR-scale
reactions between ligands 2 and PdClMe(COD) saw complete
displacement of the 1,5-cyclooctadiene ligand, yielding new
species 3, as shown in Scheme 1. Ligation of phosphorus was
demonstrated by a shift to lower field in the 31P{1H} NMR
spectrum (from δ ꢀ6.4 ppm to +31.1 ppm for 3a) and confirmed
by the 1H NMR spectrum, in which the Pdꢀmethyl resonance at
δ 0.75 ppm was split into a doublet due to coupling to
phosphorus, with a coupling constant of 2 Hz. Coordination of
the fluoroborate caused an upfield shift of the 19F NMR
resonance, from δ ꢀ134.3 ppm to ꢀ152.9 ppm in 3a. The
coordination mode of the ligand was confirmed by X-ray crystal-
lography; the structure of 3a can be seen in Figure 1, with
selected bond lengths and angles. The structure of the compound
is the expected square-planar geometry, in which the coordina-
tion sphere of the palladium center is completed by methyl,
chloride, and chelating trifluoroborate-functionalized triphenyl-
phosphine ligands; the compound is therefore formally mono-
anionic. The presence of the chloride ligand demonstrated no
salt metathesis with potassium had occurred, as compared to
other similarly functionalized trifluoroborate ligands.23 The
potassium cation is sequestered by 18-crown-6, though it shows
interactions with both the trifluoroborate moiety (K(1)ꢀF(2) =
2.617(2) Å) and an acetone ligand (K(1)ꢀO(7) = 2.783(3) Å).
The former distance is comparable to the few crystallographically
characterized examples, which lie in the range 2.60ꢀ2.94 Å.6,24
The palladiumꢀfluorine bond length was determined to be
2.181(2) Å, which is shorter than the two known values for
PdꢀFꢀBF3 connectivities (2.241(2)25 and 2.354(5) Å26). The
trifluoroborate moiety lies trans to the methyl group, raising the
potential of hemilabile behavior given the high trans influence of
the methide anion.
’ RESULTS AND DISCUSSION
Borate Salt Synthesis. According to established methodology,6
n
treatment of Ph2P(2-Br-Ph) with BuLi, followed by quenching
with an excess of trimethylborate and subsequent hydrolysis
furnishedthecorrespondingboronicacidinessentiallyquantitative
yield. Immediate dissolution in methanol and treatment with three
equivalents of KHF220 yielded the trifluoroborate salt 1a in good
yield, as shown in Scheme 1. 1a was characterized by its relatively
poor solubility in most common solvents. In contrast, the same
synthetic procedure incorporating Ar2P(2-Br-Ph) (where Ar =
2-methoxyphenyl) yielded the slightly more soluble 1b.
The diagnostic spectroscopic feature for 1a/b was observed in
their 31P NMR spectra: a single resonance split into a quartet due
to coupling to the fluorine atoms of the trifluoroborate moiety.
The shift from δ ꢀ7.7 ppm (1a) to ꢀ31.0 ppm (1b) demon-
strated the increased electron density at phosphorus in the latter
due to delocalization of the methoxy lone pair onto phosphorus.
The PꢀF coupling constant was determined to be 34 Hz in 1a and
39 Hz in 1b, somewhat smaller than the related Ph2P(2-CF3-Ph)
(53 Hz).21 Both show a characteristic, broad resonance in the 19
F
NMR spectrum: at δ ꢀ133.3 ppm (1a) and ꢀ138.6 ppm (1b),
typical of aryltrifluoroborates.20 The 11B NMR resonances were
located at ca. +2.5 ppm and were consistent with four-coordinate
boron.22 Compound 1b is significantly hygroscopic; such behavior
has also been noted in related phosphineꢀsulfonate systems.10b
The slightly increased solubility of 1b allowed crystallographic
characterization; the structure can be seen in Figure S1 of the
Supporting Information, along with relevant bond lengths and
data-processing parameters. To increase the solubility of 1a, it was
reacted with one equivalent of 18-crown-6, yielding, after recrys-
tallization, the highly crystalline 18-crown-6 adduct 2a. The
spectroscopic properties of 2a are largely the same as for 1a, but
The ligand 2b also reacted with PdClMe(COD), as monitored
1
by H NMR spectroscopy, but there was no shift in the ꢀBF3
resonance in the 19F NMR spectrum, which remained atꢀ136 ppm,
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Figure 1. Molecular structure of 3a. Displacement ellipsoids are at the 50% probability level. Acetone molecule of crystallization is omitted for clarity.
Selected bond lengths (Å) and angles (deg): Pd(1)ꢀC(1) = 2.030(4), Pd(1)ꢀCl(1) = 2.3747(10), Pd(1)ꢀP(1) = 2.2281(9), Pd(1)ꢀF(1) = 2.181(2),
B(1)ꢀF(1) = 1.406(2), B(1)ꢀF(2) = 1.421(2), B(1)ꢀF(3) = 1.393(2), K(1)ꢀF(2) = 2.617(2), K(1)ꢀO(7) = 2.828(4), C(1)ꢀPd(1)ꢀCl(1) =
90.51(11), Cl(1)ꢀPd(1)ꢀF(1) = 88.25(6) Pd(1)ꢀF(1)ꢀB(1) = 117.0(2), F(1)ꢀB(1)ꢀC(3) = 109.5(3), F(1)ꢀPd(1)ꢀP(1) = 93.10(6),
C(2)ꢀP(1)ꢀPd(1) = 112.16(11), P(1)ꢀPd(1)ꢀC(1) = 88.20(11).
indicating noncoordination. Such data implied that the com-
pound existed as a chloride-bridged dimer; this was supported by
ESI-mass spectrometry, which yielded a spectrum that included a
base peak of m/z 546 (molecular weight of 1092/2ꢀ charge),
plus a smaller peak at m/z 1046, corresponding to the mono-
anionic [M2ꢀ] ꢀCl. Presumably in this instance, the donor
properties of the more electron-rich phosphine ligand are such
that coordination of the weakly donating trifluoroborate moiety
to Pd is unnecessary to satisfy the electronic requirements of the
Pd center. Further confirmation of the dimeric nature of 3b came
Scheme 2
1
from both H and 13C{1H} NMR spectra, where two sets of
resonances were observed(inan84:16 ratio), forexampleatδ 0.30
and 1.09 ppm in the 1H NMR spectrum, corresponding to cis and
trans arrangements of the terminal methyl groups.
Reaction of 2a with [(η3-allyl)PdCl]2 yielded the new com-
plex 4a, in which the 19F NMR spectrum was again consistent
with the binding of the phosphine borate via the phosphorus
atom only; a resonance at δ ꢀ132.4 ppm in the 19F NMR
spectrum implied noncoordination of the trifluoroborate, and
the allyl co-ligand was bound in η3 fashion. This formulation was
supported by 1H NMR spectroscopy; resonances at δ 3.05, 3.17,
3.48, 4.35, and 5.62 ppm were consistent with reported data from
[(Ph3P)PdCl(η3-allyl)],27 as opposed to data from η1 allyls such
as [(dppe)PdCl(η1-allyl)],28 which display olefinic resonances at
lower field due to the absence of back-bonding.
the BF3 group of the ligand. Other reagents were similarly
unsuccessful; reaction of 3 with trimethylsilyl triflate29 also
removed fluoride, as demonstrated by the formation of Me3SiF
in NMR-scale reactions. Attempts to methylate the chloride
ligand (to form a complex of the type [k2-(P,F)RPdMe2][K(18-
crown-6)], before treatment with protic reagents to eliminate
methane) under a variety of reaction conditions were unsuccess-
ful; either decomposition to Pd(0) was observed, or attack at
fluorine in the ligand occurred, as judged by the disappearance of
the fluoride signals in the 19F NMR spectrum. Even mild
alkylating reagents such as organocopper reagents and tetra-
methyltin were unsuccessful in this regard. Given the lack of
success, an alternative strategy was needed to access [k2-(P,F)R-
PdMe(L)].
Attempts to cleave the chloride ligand from compounds 3 to
yield complexes of the general formula [k2-(P,F)RPdMe(L)]
with a vacant coordination site (where L = coordinating solvents
such as acetonitrile, and R = Ph or 2-methoxyphenyl) were
unsuccessful. Treatment with silver reagents (in an attempt to
form silver chloride by salt metathesis) abstracted fluoride from
Phosphonium Salt Synthesis. It was thought that the treat-
ment of a palladium(II) dimethyl precursor with a source of “HL”
would yield the desired palladium monomethyl complexes, with
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elimination of methane, in a similar fashion to that observed by
the groups of Jordan19b and Nozaki.10b Such an approach
necessitated the synthesis of phosphonium salts from the potas-
sium aryltrifluoroborate salts 1. Dissolution of 1a and 1b in THF,
followed by treatment with one equivalent of tetrafluoroboric
acid (as a 48% w/v solution in water), resulted in the precipita-
tion of KBF4 and production of the new compound 5, which was
separated by extraction into chlorinated solvents, as shown in
Scheme 2. The principal spectroscopic feature of phosphonium
salts 5 was a low-field doublet integrating to 1H in the 1H NMR
spectrum (centered at δ 8.85 ppm for 5a and 8.96 ppm for 5b),
with a large, one-bond coupling to the 31P nucleus of the
quaternized phosphorus center (540 and 572 Hz for 5a and 5b,
respectively). Similarly, the 31P NMR spectrum displayed a single
doublet resonance with identical coupling constant at δ +5.5
and ꢀ11.8 ppm, respectively. The increased electron richness of
the phosphorus atom in 5b, via incorporation of methoxyaryl
groups and subsequent mesomeric effects, is demonstrated by a
high-field shift of 17.3 ppm compared to its nonfunctionalized
analogue. Both compounds display single broad resonances in
the 19F NMR spectra at ca. ꢀ137 ppm, and 11B{1H} NMR
resonance at ca. +3 ppm. Confirmation of the formulation of 5
was achieved from diffraction-quality crystals of 5a grown by the
slow evaporation of an acetonitrile solution. The structure of 5a
can be seen in Figure S3, along with selected bond lengths and
angles.
Scheme 3
An alkyl phosphine derivative was also synthesized to further
examine electronic effects of the substituent on phosphorus. In
comparison to the synthesis of 5a and 5b, a slightly different
strategy was required for the synthesis of 5c: isolation, purification,
and characterization of the analogous trifluoroborate salt “1c” was
not possible due to apparent insolubility. As an alternative
approach, the corresponding boronic acid was synthesized—
according to an established procedure—as shown in Scheme 2.
Subsequent in situ quaternization of the phosphorus center,
serving to act as a protecting group, yielded the intermediate
phosphonium salt, and the following fluorination reaction cleanly
furnished the desired phosphonium salt 5c in moderate yield (5c
has been reported previously,30 though only on a small scale).
The alkyl phosphonium proton of 5c was shifted to higher field in
the 1H NMR spectrum, relative to the aryl derivatives 5a and 5b,
and was observed as a broad doublet centered at δ 6.42 ppm with
a coupling constant of 472 Hz, consistent with reported literature
values; [HPiPr3][BF4] displays a resonance at δ 5.71 ppm, with a
coupling constant of 468 Hz.31
Complexation of Phosphonium Salts. A number of strate-
gies for the complexation of bidentate phosphines to palladium
have been reported. Most involve the treatment of the easily
accessible PdMe2(tmeda) with one equivalent of the phosphine
ligand, in the presence of a donor ligand such as pyridine or
lutidine. Such reaction conditions effect the facile displacement
of the tmeda ligand, yielding complexes of the general composi-
tion [k2-(P,L)PdMe(pyridine)]. Accordingly, treatment of
PdMe2(tmeda) with one equivalent of 5a was foreseen as a route
to analogous trifluoroborate complexes, and NMR-scale reac-
tions exhibited instant gas evolution and color change from
colorless to yellow (Scheme 3). However, it became clear upon
following the reaction progress by NMR spectroscopy that the
reactivity was different from that previously reported; no dis-
placed tmeda was observed by NMR spectroscopy in the new
species 6. In the case of 6a, the NMR spectra showed a single
palladium methyl resonance at δ 0.33 ppm, showing weak
Figure 2. Molecular structure of 6a. Displacement ellipsoids are shown
at the 50% probability level. Selected bond lengths (Å) and angles
(deg): Pd(1)ꢀC(1) = 2.049(3), Pd(1)ꢀP(1) = 2.2407(7), Pd(1)ꢀN-
(1) = 2.180(2), Pd(1)ꢀN(2) = 2.231(2), Pd(1)ꢀF(1) = 3.595 Pd-
(1)ꢀF(3) = 3.061, N(1)ꢀPd(1)ꢀN(2) = 82.10(8), N(2)ꢀPd(1)ꢀ
P(1) = 104.60(6) N(1)ꢀPd(1)ꢀC(1) = 90.56(10), C(1)ꢀPd(1)ꢀ
P(1) 82.77(9).
coupling to the ligated phosphorus center. Resonances at δ 2.36
and 2.58 ppm—integration of 12H and 4H, respectively—
confirmed the presence of tmeda, thus giving an early indication
of the low donor strength of the phosphino-trifluoroborates as
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structure of 6b is essentially the same as 6a, in that the complex
is a four-coordinate Pd(II) methyl cation, displaying a weak
interaction with the aryltrifluoroborate moiety. The bond lengths
and angles are very similar to those of 6a, indicating apparently
little electronic perturbation of the Pd center by the incorpora-
tion of methoxy groups on the aryl rings of the phosphine.
Inspection of the structure revealed that one of the methoxy
groups (O21) was proximate to the nitrogen atom of the tmeda
ligand trans to the methyl group. To assess whether there was an
exchange process underway involving displacement of tmeda and
coordination of the potentially hemilabile aryloxy ligand, vari-
able-temperature NMR studies were carried out. Cooling a
1
CDCl3 sample of 6b resulted in a H NMR spectrum that
decoalesced at ca. 280 K and gave a sharp spectrum for a single
species at 230 K, as demonstrated chiefly by a single palladium
methyl signal at δ 0.06 ppm. Twelve separate resonances
integrating to 1H were observed in the aromatic region, in
addition to two separate resonances at δ 3.04 and 3.09 ppm,
corresponding to two diastereotopic methoxy groups; the methyl
groups of the tmeda ligand were also observed as four separate
resonances. Correspondingly, warming the sample from 298 K
resulted in sharpening of the broad spectrum into a single species
displaying a 1H NMR spectrum broadly similar to those obtained
for 6a/c. The observations inferred that the rotation of the
phosphine methoxyaryl rings of 6b was hindered relative to those
of 6a/c, which is unsurprising, given the potential steric clashes
with the methoxy substituents.
Figure 3. Molecular structure of 6b. Displacement ellipsoids are shown
at the 50% probability level. Selected bond lengths (Å) and angles
(deg): Pd(1)ꢀC(1) = 2.041(5), Pd(1)ꢀP(1) = 2.2718(15), Pd(1)ꢀN-
(1) = 2.224(5), Pd(1)ꢀN(2) = 2.182(2), Pd(1)ꢀF(2) = 3.697, Pd-
(1)ꢀF(3) = 2.939 N(1)ꢀPd(1)ꢀP(1) = 104.08(12), N(1)ꢀPd(1)ꢀ
N(2) = 82.07(16), N(2)ꢀPd(1)ꢀC(1) = 89.98(19), C(1)ꢀPd(1)ꢀ
P(1) = 84.11(16).
Coordination of the Trifluoroborate Ligand. In order to
access complexes of the general formula [k2-(P,F)RPdMe(L)], it
was hoped that reaction with pyridine and derivatives would
result in the displacement of the tmeda ligand, binding of the
trifluoroborate moiety, and coordination of one equivalent of
N-donor. Dissolution of complexes 6 in acetonitrile-d3 saw no
reaction; as monitored by NMR spectroscopy, no free tmeda was
observed, even after prolonged periods. Heating caused the slow
deposition of Pd(0). Conversely, dissolution of 6a in pyridine-d5
saw complete displacement of the tmeda ligand and the forma-
tion of a single new complex, 7a. The inclusion of two equivalents
of pyridine was subsequently confirmed by a preparative-scale
experiment; the structure can be seen in Figure 4. While a
detailed discussion of metric parameters is not appropriate in
view of the poor quality of the crystal, the data establish the
connectivity in the compound and show that the coordination
geometry about the Pd center is the expected square-planar
arrangement. The trifluoroborate phosphine was determined to
be bound via phosphorus only, with the coordination sphere
completed by two pyridine ligands and a methyl ligand. Once
more—as in the case of 6a and 6b—there is potentially a weak
contact between the trifluoroborate moiety and the cationic Pd
center. The PdꢀN bond lengths of 2.117(9) and 2.148(9) Å are
consistent with other known palladium monomethyl complexes
ligated by pyridine and phosphine-sulfonates, which range
between 2.051(4) and 2.108(3) Å.9g,11b,32 Over the course of
several days, slow dissociation of one equivalent of pyridine
occurred, as demonstrated by a resonance slowly appearing in the
19F NMR spectrum at δ ꢀ154.6 ppm (in comparison to the
chemical shift of ꢀ137.2 ppm for 7a), consistent with the binding
of the trifluoroborate moiety to yield a bidentate ligand. The
pyridine complex 7a could also be readily converted to the
corresponding 2,20-bipyridine complex 8a, although its very
much poorer solubility precluded it from further study. Compound
compared to the more widely known phosphino-sulfonate
ligands. The spectrum was completed by multiple aryl signals
at low field. The presence of nonligated aryltrifluoroborate was
confirmed by 19F NMR spectroscopy, in which the only observed
resonance was seen at δ ꢀ133.1 ppm, inconsistent with binding
to a metal center. The main feature of the 13C{1H} NMR
spectrum was a doublet resonance at high field (δ 5.6 ppm)
corresponding to the palladium methyl. The NMR spectra of 6c
were largely similar, appropriate resonances for differing substit-
uents notwithstanding. Crystallographic confirmation of the
structure of 6a was obtained by X-ray diffraction on a sample
grown from cooling a hot, saturated toluene solution. The
structure can be seen in Figure 2, along with relevant structural
data. The structure revealed the expected square-planar geome-
try about four-coordinate Pd(II), in which the coordination
sphere was defined by a phosphine donor, a tmeda ligand, and
the methyl group. The complex is formally zwitterionic in nature,
with possibly a weak interaction in the solid state, as the PdꢀF
distance of 3.06 Å was found to be marginally less than the sum of
the van der Waals radii (3.10 Å), although it did not appear to
persist in solution since the 19F NMR resonance did not shift
significantly to high field. The Pd(1)ꢀN(1) bond length of
2.231(2) Å is slightly longer than the analogous distance Pd-
(1)ꢀN(2), as is to be expected when residing trans to a methyl
ligand with high trans influence.
In comparison to 6a and 6c, the NMR spectra for 6b were
found to be very broad at room temperature. Integration of 1H
NMR spectra appeared to show a molecule consistent with the
formulation of 6a and 6c, but experiencing an unknown dynamic
exchange process. To ascertain the origin of this behavior, 6b was
also subjected to a crystallographic examination, the result of
which can be seen in Figure 3, along with relevant bond lengths
and angles. The investigation revealed that the solid-state
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Figure 4. Molecular structure of 7a. Displacement ellipsoids are shown at the 50% probability level.
8a could also be generated from 6a directly by the addition of one
equivalent of 2,20-bipyridine.
spectrum: the methyl resonances of 9b and 9c (δ ꢀ3.1 and ꢀ8.9
ppm, respectively) are at lower chemical shift than 9a (δ ꢀ2.9
ppm). Further corroboration for the coordination of the trifluor-
oborate group was obtained from the 13C{1H} NMR spectrum,
in which the palladium methyl resonances were split into an
apparent quartet due to coupling (2JCF = 9 Hz for 9a, 14 Hz for
9b, and 12 Hz for 9c) to the three fluorine atoms of trifluor-
oborate. This is in contrast to 3a, which displays no F-coupling to
the methyl carbon; the coupling constant of 9 Hz (for 9a) is far
larger than that observed in a the recently reported [(5,50-tBu-
bipy)PdFMe]33 (2JCF = 1.3 Hz). Other such palladium methyl
fluoride complexes are known,34,35 but no 13C NMR data have
been reported from which to draw comparisons. The methyl
carbon coupling to the phosphorus nucleus was not observed.
Crystallographic confirmation of the structure was sought;
despite multiple attempts, crystals of 9a suitable for diffraction
could not be isolated. The more soluble isopropyl derivative 9c
readily yielded suitable crystals, and the structure can be seen in
Figure 5, in addition to pertinent data. The structure confirmed the
bidentate coordination mode of the trifluoroborate ligand; the
Pd(1)ꢀF(1) bond distance of 2.1634(17) Å was in good agree-
ment with the 2.181(2) Å found in 3a. The coordination of the
trifluoroborate group caused a lengthening of the B(1)ꢀF(1)
bond, to 1.467(4) Å, as opposed to an average of 1.37 Å in
B(1)ꢀF(2)/B(1)ꢀF(3). The palladiumꢀnitrogen distance was
determined to be 2.135(2) Å, corresponding very well to other
crystallographically characterized Pd-lutidine complexes,10b,14a,36
inwhich the averagePdꢀN distance wasdetermined to be 2.133 Å.
Reactivity with Olefins. Nozaki and co-workers have recently
demonstrated that analogous sulfonated phosphines of the
general formula [k2-(P,O)PdMe(lutidine)] (where (P,O) =
arylphosphinosulfonate) homopolymerize ethylene and have
isolated products and model complexes consonant with multiple
(i.e., >10) insertions into the Pdꢀmethyl bond.9e The catalytic
process is thought to be catalyzed by the presence of a small
Palladium Lutidine Complexes. Inspection of the structure
of 7a revealed that the two pyridine ligands experience significant
steric abutment. It was postulated that replacement of pyridine
with the more sterically demanding 2,6-lutidine would only allow
the coordination of one equivalent of donor ligand, thus encoura-
ging coordination of trifluoroborate. Reaction of tmeda complex
6a with lutidineresultedina yellow solution, which overthe course
of several hours saw a white precipitate develop. Filtration of the
solid and characterization by 1H NMR spectroscopy showed the
material to be complex 6a. Drying of the supernatant in vacuo
yielded another species, 9a, with spectral properties consistent
with the desired formulation of [k2-(P,F)PhPdMe(lutidine)]
(vide infra); however the reaction was far from clean, and some
30ꢀ35% by mass of the starting material 6a was present.
This suggests that 6a and 9a are in equilibrium and the free tmeda
present precludes complete formation of the desired product.
Thus, the synthesis was repeated in a series of iterations:
dissolution, removal of all volatiles (including tmeda), and
further dissolution in lutidine. After five such cycles, followed
by washing with diethyl ether, an essentially quantitative yield of
9a was obtained in high purity. The corresponding derivatives 9b
and 9c were thus obtained similarly, though in slightly lower
yields due to increased solubility.
1
The H NMR spectrum of 9a showed a single Pd methyl
resonance at δ 0.49 ppm, and a singlet resonance at δ 3.17
ppm integrating to 6H, consistent with the methyl groups of
ligated lutidine, in good agreement with the closely related
complex [k2-(P,O)ArPdMe(lutidine)] at δ 3.14 ppm.10b Binding
of the fluoroborate group was confirmed by 19F NMR; reso-
nances were observed at δ ꢀ158.1 (9a), ꢀ157.6 (9b), and
ꢀ161.1 ppm (9c), respectively. The improved electronic donor
properties of the methoxyaryl phosphine versus the diphenyl
derivative were shown in a slight high-field shift in the palladium
methyl resonance (δ 0.34 ppm in 9b vs δ 0.49 ppm in 9a). The
increased electron density on the Pd center—as conferred by the
more electron rich ligands 9b and 9c—is also shown by a high-
field shift of the Pd methyl resonances in the 13C{1H} NMR
1
amount (ca. 10 mol % by H NMR) of [k2-(P,O)ArPdMe-
(C2H4)], where the displaced lutidine could be observed by
NMR spectroscopy. Accordingly, chloroform-d3 solutions of
palladium complexes 9 were degassed via freezeꢀpumpꢀthaw
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Figure 5. Molecular structure of 9c. Displacement ellipsoids are shown at the 50% probability level. Selected bond lengths (Å) and angles (deg):
Pd(1)ꢀC(1) = 2.010(3), Pd(1)ꢀF(1) = 2.1634(17), Pd(1)ꢀP(1) = 2.2510(8), Pd(1)ꢀN(1) = 2.135(2), B(1)ꢀF(1) = 1.467(4), B(1)ꢀF(2) =
1.392(4), B(1)ꢀF(3) = 1.397(4), C(1)ꢀPd(1)ꢀP(1) = 91.97(10), P(1)ꢀPd(1)ꢀF(1) = 91.92(5), F(1)ꢀPd(1)ꢀN(1) = 90.14(8), N(1)ꢀPd-
(1)ꢀC(1) = 85.97(11), Pd(1)ꢀF(1)ꢀB(1) = 117.48(7), F(1)ꢀB(1)ꢀC(10) = 111.5(3), B(1)ꢀC(10)ꢀC(9) = 127.1(3), C(10)ꢀC(9)ꢀP(1) =
123.9(2), C(9)ꢀP(1)ꢀPd(1) = 114.48(10).
Figure 6. 1H NMR spectra after treatment of 9a with ethylene. Asterisk denotes residual protio-solvent.
cycles and exposed to one atmosphere of ethylene. No immedi-
ate color changes were observed, nor any precipitation of
polymeric materials. The reaction with 9a was immediately
assayed by NMR spectroscopy, showing essentially no reaction
at ambient temperature. Monitoring over the course of several
hours showed the very slow formation of products exhibiting
consistent with formation of oligomers. After approximately 18 h
it became clear that the ethylene was being consumed, at the
expense of the formation of a mixture of propene (48% by
integration of methyl group protons), 1-butene (35%), 2-butene
(23%), and a small amount of dihydrogen (4%), along with
concomitant disappearance of the palladium methyl resonance.
1H NMR spectra at various time intervals during the reaction can
1
resonances in the olefinic region of the H NMR spectrum
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Scheme 4
still intact, best demonstrated by a 19F NMR signal resonating at
ꢀ152.4 ppm. Preparative-scale reactions were similarly facile. No
ligated lutidine resonances were observed. The inference from
this observation is that it is indeed the lutidine ligand that is
displaced during the ethylene insertion and not the potentially
hemilabile phosphine-borate ligand. Exposure of 10a to ethylene
under identical conditions to those described above and mon-
itoring by 1H NMR spectroscopy revealed essentially no reaction
after 24 h, in comparison to the significant amount of dimeriza-
tion afforded by complexes 9. Similarly, exposure of the less
sterically demanding (versus lutidine complexes 9) 7a to one
atmosphere of ethylene also led to no reaction, doubtless due to
the stronger binding of the pyridine co-ligands to the overall
cationic complex.
’ CONCLUSIONS
Lithiation of arylphosphines, followed by quenching with a
boron-containing electrophile and subsequent fluorination,
yields trifluoroborate-functionalized phosphines, which form
palladium chloromethyl complexes in a facile manner when
reacted with PdClMe(COD). Cleavage of the PdꢀCl bond in
attempts to access catalytically feasible compounds was found to
be problematic under a variety of reaction conditions. To
circumvent this problem, a series of zwitterionic phosphonium
salts containing aryltrifluoroborate moieties have been reported
and, in one instance, structurally characterized. Reaction with
PdMe2(tmeda) yielded zwitterionic palladium monomethyl
complexes of the general formula [k-(P)RPdMe(tmeda)], which
can be cleanly converted to the corresponding chelated species
[k2-(P,F)RPdMe(lutidine)] by reaction with 2,6-lutidine at
ambient temperature. Such complexes have been crystallogra-
phically characterized and react slowly with ethylene at ambient
temperature and pressure, yielding a mixture of butenes, pro-
pene, and hydrogen consistent with ethylene dimerization
probably via a mechanism proposed by Jordan et al. for a related
system.37 In comparison to analogous sulfonated phosphine
ligands and complexes, the rate of insertion is much slower and
more limited in number. This is attributed to the relative electron
deficiency of the trifluoroborate moiety as compared to sulfo-
nate, resulting in an electron-deficient palladium center and more
tightly bound lutidine.
be seen in Figure 6. The resonances associated with the Pd
complex 9a were identical to that of the free complex; no other
significant species were observed in solution, and furthermore,
no free lutidine was observed. Jordan and co-workers have
reported similar observations in a related Pd system37 where
the Pd center was supported by a chelating dipyridyl ligand, and
their suggested mechanism can be seen in Scheme 4, which is
consistent with the observations above. Over the course of three
days, the ethylene was completely consumed, with the concomi-
tant appearance of black particulate matter and apparent degra-
dation of the metal complex in solution.
In comparison to 9a, initial 1H NMR spectra from the
reactions of 9b/c with ethylene showed slightly different beha-
vior in that a number of minor, unidentified species (although
less than 5% by integration) were observed. Larger amounts of
the olefinic products were present at given times (versus 9a) for
9b and 9c, as judged by NMR integration of product versus
“catalyst”; as might be expected, the stronger donor ligands
afford a more electron-rich metal center, and thus a more labile
lutidine ligand. Also noteworthy in the case of 9b and 9c is that
the amount of 2-butene observed in either sample was signifi-
cantly suppressed early in the course of the reaction. Over the
course of time, the 2-butene resonance grew in, consistent with
the mechanism shown in Scheme 4;38 however the experiments
still required more than two days for the ethylene to be
completely consumed. The implication of such an observation
is that the Pd center was, overall, too electron deficient to allow
the tightly bound lutidine ligand to labilize to the degree
necessary to allow faster initiation, coordination, and insertion.
To assess whether the ligand displaced—in the absence of
evidence of free lutidine—to coordinate the ethylene was
actually the trifluoroborate moiety, one equivalent of 4-dimethy-
laminopyridine (DMAP) was added. The reaction to form the
new complex 10a was instantaneous, as monitored by various
NMR spectroscopies, and showed that the bidentate ligand was
’ EXPERIMENTAL DETAILS
General Considerations. Unless otherwise indicated, all manip-
ulations were carried out in either an MBraun inert atmosphere glovebox
or on a greaseless dual-manifold vacuum line using Teflon (Kontes)
needle valves and swivel-frit-type glassware. Toluene, THF, and hexanes
were dried using a Grubbs/Dow solvent purification system and stored
in evacuated bombs prior to use. Dichloromethane was predried over
CaH2 before vacuum transfer into a separate evacuated bomb over
CaH2. CDCl3 was purchased from Cambridge Isotopes and used as
received for characterization of complexes; for ethylene experiments it
was dried over CaH2. Acetone-d6, dimethylsulfoxide-d6, and methanol-
d4 were purchased from Cambridge Isotopes and used as received.
Potassium hydrogen fluoride, trimethylborate, tetrafluoroboric acid (as a
48% solution in water), nBuLi, pyridine, 2,20-bipyridine, chlorobenzene,
2,6-lutidine, and DMAP were purchased from Aldrich and used as
received. 18-Crown-6 was purchased from Acros Organics and used as
received. Ethylene was purchased from Praxair and passed through an
OxiClear gas purifier prior to use. PPh2(2-Br-Ph),39 PdClMe(COD),40
and PdMe2(tmeda)41 were prepared according to literature procedures.
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P(2-OMe-Ph)2(2-Br-Ph)42 and PiPr2(2-Br-Ph)43 were prepared via
literature procedures from PCl2(2-Br-Ph),44 which was obtained via a
modified literature procedure, for which details are given. [PdCl(η3-
allyl)]2 was purchased from Strem, transferred to a glovebox freezer, and
used as received. NMR spectra were obtained on Bruker AMX-300,
AMX-400, and DRX-400 spectrometers. 1H and 13C{1H} NMR spectra
oil. Yield: typically 50ꢀ55%. 1H NMR spectroscopy showed the material
to be essentially pure. 31P NMR spectroscopy showed the title compound
present in ca. 95% purity. 1H NMR (400 MHz, CDCl3, 298 K): δ 7.41
(t of d, 1H, aryl C-H, 3JHH = 8 Hz, 4JHH = 2 Hz), 7.56 (t of d, 1H, aryl
C-H, 3JHH = 8 Hz, 4JHH = 2 Hz), 7.62 (d of t, aryl C-H, 3JHH = 8 Hz,
4JHH = 2 Hz), 8.11 (d of d, 1H, aryl C-H, 3JHH = 8 Hz, 4JHH = 2 Hz).
31P{1H} NMR (162.0 MHz, CDCl3, 298 K): δ +154.0 ppm (s, PCl2(2-
Br-Ph)).
were referenced to tetramethylsilane, 11B{1H} NMR spectra to BF3
3
OEt2, 19F NMR spectra to CFCl3, and 31P NMR spectra to 85%
aqueous phosphoric acid. Full structural assignment was confirmed by
2-D NMR spectra where necessary. Elemental analyses and mass spectra
were obtained by the Instrumentation Facility of the Department of
Chemistry, University of Calgary. Quoted elemental analysis results are
the average of two separate determinations.
P(2-OMe-Ph)2(2-BF3K-Ph), 1b. As for 1a, using P(2-OMe-Ph)2-
n
(2-Br-Ph) (1.30 g, 3.2 mmol), BuLi (1.3 mL of a 2.5 M solution in
hexanes, 1 equiv), and trimethylborate (1 mL) in THF (50 mL), and then
KHF2 (0.75 g, 9.6 mmol) in water (5 mL), yielded the title compound as
an off-white, crystalline solid. Yield: 1.05 g (2.3 mmol, 71%). Single
crystals suitable for X-ray diffraction were grown from a saturated
PPh2(2-BF3K-Ph), 1a. A 250 mL round-bottomed flask was
charged with Ph2P(2-Br-Ph) (5.00 g, 14.7 mmol, ground and dried
under high vacuum for 2 h prior to use to remove ethanol of
recrystallization). THF (75 mL) was condensed in at ꢀ78 °C, and
nBuLi (2.5 M in hexanes, 6.0 mL, 15.0 mmol) was added dropwise via
syringe, resulting in a color change to orange. The reaction was stirred at
low temperature for 2 h. Trimethylborate (8.3 mL, 73.5 mmol, 5 equiv)
was added via syringe, resulting in an immediate reaction and dissipation
of the reaction coloration to pale yellow. The reaction was allowed to
warm to ambient temperature over the course of 30 min, before being
allowed to stir overnight. Water (30 mL) was then added via syringe,
resulting in the precipitation of a white solid from a pale yellow solution,
which slowly redissolved with stirring. Diethyl ether (50 mL) was added,
and the layers were separated. The aqueous layer was extracted with
diethyl ether (2 ꢁ 50 mL). The organic phase was dried over MgSO4
and the solvent removed to yield a viscous, white gum, which was dried
under high vacuum to yield a white foam. [1H NMR (300 MHz, CDCl3,
298 K): δ 6.24 ppm (br s, 2H, B(OH)2), 7.15ꢀ7.37 (m, 12H, aryl C-H),
7.75 (m, 1H, aryl C-H), 8.06 (m, 1H, aryl C-H). 31P{1H} NMR (162.00
MHz, CDCl3, 298 K): δ ꢀ13.2 ppm (s, PPh2(2-B(OH)2-Ph)).] The
foam was dissolved in methanol (75 mL) in a 250 mL round-bottomed
flask. A solution of KHF2 (3.4 g, 44.1 mmol, 3 equiv) in water (15 mL)
was added slowly, with stirring. After 1 min the solution became turbid;
after ca. 5 min a white solid precipitated. The reaction was left to stir for 2
h at room temperature, before filtration under reduced pressure and
washing with cold methanol and diethyl ether. The resulting white solid
was dried under high vacuum before use. Yield: 2.96 g (8.0 mmol, 55%).
1H NMR (400 MHz, (CD3)2SO, 298 K): δ 6.72 ppm (app. d of d, 1H,
aryl C-H, 3JHH = 7 Hz, 4JHH = 4 Hz), 6.96 (t of d, 1H, aryl C-H, 3JHH = 7
Hz, 4JHH = 1 Hz), 7.10 (m, 5H, aryl C-H), 7.25 (m, aryl C-H, 5H, aryl
C-H), 7.44 (d of d, 1H, aryl C-H, 3JHH = 7 Hz, 4JHH = 1 Hz), 7.53 (d of d,
1H, aryl C-H, 3JHH = 7 Hz, 4JHH = 1 Hz). 13C{1H} NMR (75.5 MHz,
(CD3)2SO, 298 K): δ 125.8 ppm (d, aryl Cq, 1JCP = 41 Hz), 127.1 (aryl
C-H), 128.4 (d, aryl C-H, 3JCP = 5 Hz), 132.0 (d, aryl C-H, 3JCP = 5 Hz),
132.7 (aryl C-H), 133.5 (d, aryl C-H, 2JCP = 19 Hz), 139.0 (d, aryl C-H,
2JCP = 19 Hz), 141.4 (d, aryl C-H, 3JCP = 16 Hz). Carbon adjacent to
boron not observed. 11B{1H} NMR (128.4 MHz, (CD3)2SO, 298 K):
δ +2.9 ppm (br s, C6H4BF3K). 19F NMR (376.6 MHz, (CD3)2SO,
298 K): δ ꢀ133.3 ppm (br s, C6H4BF3K). 31P{1H} NMR (162.0 MHz,
(CD3)2SO, 298 K): δ ꢀ7.7 ppm (q, PPh2(2-BF3K-Ph), 4JPF = 34 Hz).
HRMS (ESI ꢀve): calcd for [Mꢀ] m/z 329.09201; found 329.08897.
Improved Synthesis of PCl2(2-Br-Ph). The reaction between
PCl3 and 2-bromophenyldiazonium tetrafluoroborate was carried out
according to the reported methods of Talay and Rehder,44a and Wills
et al.,44b as far as the overnight reaction with Al powder in acetonitrile.
After the overnight reaction, all volatiles were removed in vacuo to yield a
viscous, brown residue. Dry toluene (50 mL) was condensed in
at ꢀ78 °C, and the resulting suspension left to stir vigorously for one
hour. The reaction mixture was then allowed to settle and filtered to
1
acetone solution. H NMR (400 MHz, (CD3)2CO, 298 K): δ 3.61
ppm (s, 6H, 2 ꢁ OCH3), 6.63 (m, 2H, aryl C-H), 6.79 (m, 3H, aryl
C-H), 6.94 (m, 3H, aryl C-H), 7.11 (m, 1H, aryl C-H), 7.26 (m, 2H, aryl
C-H), 7.71 (m, 1H, aryl C-H). 13C{1H} NMR (100.6 MHz, (CD3)2SO,
298 K): δ 55.9 ppm (OCH3), 110.8, 120.8, 125.9, 126.8 (all aryl C-H),
128.8 (d, 1JCP = 20 Hz, aryl Cq), 129.4 (aryl C-H), 132.7 (d, aryl C-H,
2JCP = 10 Hz), 134.0 (aryl C-H), 138.8 (d, aryl Cq, 2JCP = 17 Hz), 161.1
2
(d, aryl Cq, JCP = 16 Hz). Carbon adjacent to boron not observed.
11B{1H} NMR (128.4 MHz, (CD3)2SO, 298 K): δ +3.6 ppm (br s,
C6H4BF3K). 19F NMR (376.6 MHz, (CD3)2CO, 298 K): δ ꢀ137.0
ppm (br s, C6H4BF3K). 31P{1H} NMR (162.0 MHz, (CD3)2CO, 298
K): δ ꢀ31.4 ppm (q, P(2-OMe-Ph)2(2-BF3K-Ph), 4JPF = 39 Hz). Anal.
Calcd for C20H18BF3KO2P (H2O)1.5: C, 52.77; H, 4.65. Found: C,
3
52.74; H, 4.27. MS (ESI ꢀve): m/z 389 [M+ ꢀ K].
[PPh2(2-BF3-Ph)][K(18-crown-6)], 2a. A 100 mL round-bot-
tomed flask was charged with 1a (1.75 g, 4.8 mmol) and a magnetic stir
bar. Acetone (25 mL) was added. To the resulting white slurry was
added dropwise a solution of 18-crown-6 (1.25 g, 4.8 mmol) in acetone
(10 mL). The suspended white solid slowly dissolved on addition of the
crown ether solution; the colorless solution was left to stir at ambient
temperature. After a period of ca. 30 min a white solid was seen to
precipitate. The solution was heated to dissolve the white solid, before
being allowed to cool to ambient temperature; the title compound
precipitated as a highly crystalline, colorless solid, which was isolated by
filtration and dried in vacuo. Concentration of the supernatant and
storage at low temperature yielded further crops of material. Yield: 1.73 g
(2.7 mmol, 58%). Single crystals suitable for X-ray diffraction were
1
grown by the slow cooling of a saturated acetone solution. H NMR
(300 MHz, CDCl3, 298 K): δ 3.59 ppm (s, 24H, OCH2 of 18-crown-6),
6.95 (t, 1H, aryl C-H, 3JHH = 7 Hz), 7.07 (t, 1H, aryl C-H, 3JHH = 7 Hz),
7.23 (m, 7H, aryl C-H), 7.32ꢀ7.35 (m, 4H, aryl C-H), 7.87 (m, 1H, aryl
C-H). 13C{1H} NMR (75.5 MHz, CDCl3, 298 K): δ 70.0 ppm (OCH2
of 18-crown-6), 126.7 (d, aryl Cq, 1JCP = 75 Hz), 127.1 (aryl C-H), 127.7
(d, aryl C-H, 3JCP = 8 Hz), 127.8 (d, aryl C-H, 3JCP = 8 Hz), 132.7 (d, aryl
C-H, 2JCP = 19 Hz), 133.7 (d, aryl C-H, 2JCP = 18 Hz) 138.6, 141.0 (both
3
d, aryl C-H, JCP = 15 Hz). Carbon adjacent to boron not observed.
11B{1H} NMR (128.4 MHz, CDCl3, 298 K):δ+2.9 ppm (br s, C6H4BF3).
19F NMR (376.6 MHz, CDCl3, 298 K): δ ꢀ134.3 ppm (br s, C6H4BF3).
31P{1H} NMR (162.0 MHz, CDCl3, 298 K): δ ꢀ6.4 ppm (q, PPh2
(2-BF3-Ph)), 4JPF = 35 Hz). Anal. Calcd for C30H38BF3KO6P.C3H6O:
C, 55.82; H, 6.25. Found: C, 55.90; H, 5.97. MS (ESI ꢀve): m/z 329
[M ꢀ K(18-crown-6)].
[P(2-OMe-Ph)2(2-BF3-Ph)][K(18-crown-6)], 2b. As for 2a,
using 1b (0.300 g, 0.65 mmol) and 18-crown-6 (0.175 g, 0.65 mmol)
in acetone (2 mL) yielded a highly crystalline, colorless solid. Yield:
0.427 g (0.59 mmol, 91%). 1H NMR (400 MHz, CD2Cl2, 298 K): δ 2.19
ppm (s, 6H, CH3 of acetone), 3.54 (s, 24H, OCH2 of 18-crown-6), 3.62
(s, 6H, 2 ꢁ OCH3), 6.77ꢀ6.84 (m, 6H, aryl C-H), 7.00 (t, 1H, aryl C-H,
3JHH = 7 Hz), 7.18ꢀ7.22 (m, 3H, aryl C-H), 7.86 (m, 1H, aryl C-H).
13C{1H} NMR (100.6 MHz, CDCl3, 298 K): δ 55.8 ppm (OCH3), 69.9
remove insoluble Al and BF3 NCMe, yielding an orange solution, which
3
was concentrated in vacuo to yield the title compound as a yellow-orange
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(OCH2 of 18-crown-6), 110.7, 120.7, 125.6, 126.5, 129.2 (all aryl C-H),
129.4 (d, 1JCP = 22 Hz, aryl Cq), 132.5 (aryl C-H), 132.8 (d, 3JCP = 8 Hz,
aryl C-H), 134.0 (aryl C-H), 139.9 (d, 1JCP = 20 Hz, aryl Cq), 162.1 (d,
2JCP = 17 Hz, aryl Cq). Carbon adjacent to boron not observed. 11B{1H}
NMR (128.4 MHz, (CD3)2SO, 298 K): δ +2.8 ppm (br s, C6H4BF3).
19F NMR (376.6 MHz, CDCl3, 298 K): δ ꢀ136.5 ppm (br s, C6H4BF3).
31P{1H} NMR (162.0 MHz, CDCl3, 298 K): δ ꢀ 25.5 ppm (q, P(2-
OMe-Ph)2(2-BF3-Ph), 4JPF = 35 Hz). Anal. Calcd for C32H42BF3KO8P:
C, 55.50; H, 6.11. Found: C, 55.26; H, 6.12. MS (ESI ꢀve): m/z 389
[M ꢀ K(18-crown-6)].
the title compound as an off-white solid, which was crystallized from
acetone. Yield: 0.845 g (1.04 mmol, 94%). 1H NMR (400 MHz, CDCl3,
298 K): δ 3.08 ppm (d, 1H, allylic CH2, 3JHH = 12 Hz), 3.09 (d, 1H,
allylic CH2, 3JHH = 7 Hz), 3.39 (d of d, 1H, dCH2, 2JHH = 14 Hz, 3JHH
=
10 Hz), 3.47 (s, 24H, OCH2 of 18-crown-6), 4.23 (m, 1H, dCH2), 5.56
(m, 1H, dC-H), 6.48 (t, 1H, aryl C-H, JHH = 7 Hz), 6.95 (t, 1H, aryl
3
C-H, JHH = 7 Hz), 7.25 (m, 7H, aryl C-H), 7.68 (m, 5H, aryl C-H).
13C{1H} NMR (75.5 MHz, CDCl3, 298 K): δ 53.5, 62.7 ppm (both allyl
1
C-H), 70.0 (OCH2 of 18-crown-6), 74.5 (d, allyl C-H, JCP = 32 Hz),
117.0 (d, allyl C-H, 4JCP = 5 Hz), 125.9 (d, aryl C-H, 3JCP = 8 Hz), 127.7
(br), 128.4, 129.0 (all aryl C-H), 130.4 (d, aryl C-H, 3JCP = 8 Hz), 134.4
(d, aryl C-H, 2JCP = 13 Hz), 135.2 (d, aryl C-H, 2JCP = 13 Hz), 135.9
[j2-(P,F)PhPdClMe][K(18-crown-6)], 3a. A 50 mL round-bot-
tomed flask was charged with PdClMe(COD) (0.20 g, 0.74 mmol) and
2a (0.576 g, 0.74 mmol). Dichloromethane was syringed in at room
temperature, and the resulting pale yellow-green solution stirred at room
temperature overnight (a small amount of Pd(0) was deposited during
the reaction). The reaction mixture was filtered through Celite to yield a
clear, yellow solution; removal of volatiles in vacuo yielded the title
compound as a crystalline, pale yellow solid, which was crystallized by
the slow evaporation of a dichloromethane solution. Yield: 0.241 g (0.27
mmol, 36%). Single crystals suitable for X-ray diffraction were grown by
the slow evaporation of an acetone solution. 1H NMR (400 MHz,
CDCl3, 298 K): δ 0.75 ppm (d, 3H, Pd-CH3, 3JPH = 2 Hz), 3.56 (s, 24H,
OCH2 of 18-crown-6), 6.87 (t, 1H, aryl C-H, 3JHH = 7 Hz), 7.12 (t, 1H,
aryl C-H, 3JHH = 7 Hz), 7.36ꢀ7.54 (m, 11H, aryl C-H), 7.73 (m, 1H, aryl
C-H). 13C{1H} NMR (100.6 MHz, CDCl3, 298 K): δ ꢀ2.7 ppm (Pd-
1
(d, aryl Cq, JCP = 37 Hz). Carbon adjacent to boron not observed.
11B{1H} NMR (128.4 MHz, CDCl3, 298 K): δ +3.6 ppm (br s,
C6H4BF3). 19F NMR (376.6 MHz, CDCl3, 298 K): δ ꢀ132.3 ppm (br
s, C6H4BF3). 31P{1H} NMR (162.0 MHz, CDCl3, 298 K): δ +22.5
ppm (s, PPh2(2-BF3-Ph)) Anal. Calcd for C33H43BF3KO6PPdCl: C,
48.62; H, 5.32. Found: C, 48.66; H, 5.37. MS (ESI ꢀve): m/z 511
[M ꢀ K(18-crown-6)].
PHPh2(2-BF3-Ph), 5a. Potassium salt 1a (3.25 g, 8.8 mmol) was
slurried in THF (50 mL). HBF4 (1.6 mL of a 48 wt % solution in water,
8.8 mmol) was added, and the white suspension left to stir at room
temperature for 2 h. All volatiles were removed under reduced pressure,
and the white solid was extracted with chloroform (3 ꢁ 50 mL). The
solvent was removed under reduced pressure to yield the title compound
as a white solid. Yield: 2.87 g (8.7 mmol, 95%). While generally pure
enough for subsequent use, the compound could be recrystallized from
hot acetonitrile, if necessary. Single crystals suitable for X-ray diffraction
were grown by the slow evaporation of a saturated acetonitrile solution.
1H NMR (400 MHz, CDCl3, 298 K): δ 7.21 ppm (t, 1H, aryl C-H, 3JHH
= 7 Hz), 7.35 (m, 1H, aryl C-H), 7.57ꢀ7.67 (m, 9H, aryl C-H), 7.76 (m,
2H, aryl C-H), 8.13 (m, 1H, aryl C-H), 8.85 (d, 1H, H-PPh2(2-
3
CH3), 70.0 (OCH2 of 18-crown-6), 126.0 (d, aryl C-H, JCP = 8 Hz),
128.0 (d, aryl C-H, 2JCP = 12 Hz), 128.3 (d, aryl C-H, 2JCP = 12 Hz),
129.2, 129.7 (both aryl C-H), 132.2 (d, aryl Cq, 1JCP = 43 Hz), 132.4 (aryl
C-H), 132.8 (d, aryl C-H, 2JCP = 12 Hz), 134.2 (d, aryl C-H, 2JCP = 12
Hz). Carbon adjacent to boron not observed. 11B{1H} NMR (128.4
MHz, CDCl3, 298 K): δ +2.9 ppm (br s, C6H4BF3). 19F{1H} NMR
(376.6 MHz, CDCl3, 298 K): δꢀ152.9 ppm (brs, C6H4BF3Pd). 31P{1H}
NMR (162.0 MHz, CDCl3, 298 K): δ +31.1 ppm (s, PPh2(2-BF3K(18-
1
BF3ꢀPh), JPH = 540 Hz). 13C{1H} NMR (100.6 MHz, (CD3)2SO,
298 K): δ 125.0 ppm (d, aryl Cq, 1JCP = 50 Hz), 126.8 (d, aryl Cq, 1JCP
=
crown-6)-Ph). Anal. Calcd for C31H41O6BF3KPPdCl (CH2Cl2)0.2: C,
3
51 Hz), 127.2 (d, aryl C-H, 3JCP = 9 Hz), 127.9 (d, aryl C-H, 2JCP = 19
Hz), 128.4 (aryl C-H), 128.7 (d, aryl C-H, 4JCP = 6 Hz), 129.7 (d, aryl C-
H, 3JCP = 11 Hz), 131.6, 132.3, 133.3 (all aryl C-H), 133.5 (d, aryl C-H,
46.47; H, 5.17. Found: C, 46.74; H, 5.33. MS (ESI ꢀve): m/z 484
[M ꢀ K(18-crown-6)].
[j-(P)ArPdClMe]2[K(18-crown-6)]2, 3b. As for 3a, using 2b
(0.3.00 g, 0.38 mmol) and PdClMe(COD) (0.102 g, 0.38 mmol)
yielded the title compound, after crystallization from toluene, as a highly
4JCP = 5 Hz), 133.7 (d, aryl C-H, 4JCP = 6 Hz), 134.0 (d, aryl C-H, 3JCP
=
13 Hz). Carbon adjacent to boron not observed. 11B{1H} NMR (128.4
CDCl3, 298 K): δ +2.4 ppm (br s, C6H4BF3). 19F NMR (376.6 MHz,
CDCl3, 298 K): δ ꢀ136.2 ppm (br s, C6H4BF3). 31P{1H} NMR (162.00
MHz, CDCl3, 298 K): +5.5 ppm (s, HPPh2(2-BF3-Ph)). 31P NMR
(162.00 MHz, CDCl3, 298 K): +5.5 ppm (d, 1JPH = 540 Hz, HPPh2(2-
BF3-Ph). Anal. Calcd for C18H15BF3P: C, 65.50; H, 4.58. Found: C,
1
crystalline yellow solid. Yield: 0.155 g (0.082 mmol, 43%). H NMR
(400 MHz, CDCl3, 298 K) (major isomer only): δ 1.07 ppm (d, 3H, Pd-
3
CH3, JPH = 2 Hz), 3.60 (s, 24H, OCH2 of 18-crown-6), 3.80 (s, 6H,
OCH3), 6.87ꢀ6.93 (m, 4H, aryl C-H), 7.03 (m, 2H, aryl C-H), 7.31
(t, 1H, aryl C-H, 3JHH = 7 Hz), 7.36ꢀ7.42 (m, 4H, aryl C-H), 7.87 (m,
1H, aryl C-H). 13C{1H} NMR (100.6 MHz, CDCl3, 298 K) (major
isomer only): δ ꢀ3.3 ppm (Pd-CH3), 56.2 (OCH3), 70.0 (OCH2 of 18-
65.26; H, 4.62. MS (EI +ve): m/z 310 [M+ ꢀ HF], 180 [M+
ꢀ
C6H4BF3].
1
crown-6), 110.8 (aryl C-H), 119.4 (d, JCP = 51 Hz, aryl C-H), 119.8
PH(2-OMe-Ph)2(2-BF3-Ph), 5b. As for 5a, using 1b (1.05 g, 2.30
mmol) and HBF4 (48 wt % aq) (0.37 mL, 4.2 mmol) yielded the title
compound as an off-white, hygroscopic solid. Yield: 0.830 g, 2.12 mmol,
(d, 3JCP = 11 Hz, aryl C-H), 120.9 (d, 3JCP = 10 Hz, aryl C-H), 120.9
(d, 1JCP = 51 Hz, aryl Cq), 125.3 (d, 3JCP = 10 Hz, aryl C-H), 128.9, 131.8
(both aryl C-H), 132.7 (d, 3JCP = 10 Hz, aryl C-H), 134.1 (d, 2JCP = 16
Hz, aryl C-H), 136.2 (d, 3JCP = 10 Hz, aryl C-H), 160.7 (aryl Cq). Carbon
adjacent to boron not observed. 11B{1H} NMR (128.4 MHz, CDCl3,
298 K): δ +3.2 ppm (br s, C6H4BF3). 19F NMR (376.6 MHz, CDCl3,
298 K): δ ꢀ136.9 ppm (br s, C6H4BF3). 31P{1H} NMR (162.0 MHz,
CDCl3, 298 K): δ +29.4 ppm (s, P(2-OMe-Ph)2(2-BF3-Ph)). Anal.
1
92%. H NMR (400 MHz, CDCl3, 298 K): δ 3.81 ppm (s, 6H, 2 ꢁ
OCH3), 7.04ꢀ7.09 (m, 7H, aryl C-H), 7.62 (t, 1H, aryl C-H, 3JHH = 7
Hz), 7.68 (m, 2H, aryl C-H), 8.08 (t, 1H, aryl C-H, 3JHH = 7 Hz), 8.96 (d,
1
1H, H-P(2-OMe-Ph)2(2-BF3-Ph), JPH = 572 Hz). 13C{1H} NMR
(100.6 MHz, CDCl3, 298 K): δ 56.3 ppm (OCH3), 106.8 (d, aryl Cq,
1JCP = 94 Hz), 111.7 (aryl C-H), 116.2 (d, aryl Cq, 1JCP = 93 Hz), 121.8
(d, aryl C-H, 2JCP = 13 Hz), 126.8 (d, aryl C-H, 2JCP = 14 Hz), 131.9 (d,
Calcd for C66H90B2F6K2O16P2Pd2Cl2 (C7H8)0.5: C, 47.84; H, 5.43.
3
Found: C, 47.99; H, 5.36. MS (ESI ꢀve): m/z 1055 [M2ꢀ ꢀ 2 K
(18-crown-6) ꢀ Cl], 546 [M2ꢀ ꢀ 2 K(18-crown-6)].
aryl C-H, 2JCP = 15 Hz), 133.0 (d, aryl C-H), 134.5 (d, aryl C-H, 2JCP
=
15 Hz), 136.4 (d, aryl C-H, 3JCP = 8 Hz), 161.0 (aryl Cq of C6H4OCH3).
Carbon adjacent to boron not observed. 11B{1H} NMR (128.4 MHz,
CDCl3, 298 K): δ +2.6 ppm (br s, C6H4BF3). 19F NMR (376.6 MHz,
CDCl3, 298 K): δ ꢀ138.0 ppm (br s, C6H4BF3). 31P NMR (162.0 MHz,
[j-(P)PhPdCl(η3-allyl)], 4a. A 50 mL round-bottomed flask was
charged in the glovebox with [PdCl(η3-allyl)]2 (0.20 g, 0.55 mmol) and
2a (0.691 g, 1.10 mmol). Dichloromethane was condensed in at ꢀ78 °C,
and the reaction was slowly allowed to warm to room temperature,
yielding a yellow solution. The reaction was left to stir at room
temperature overnight, and all volatiles were removed in vacuo to yield
CDCl3, 298 K): δ ꢀ11.8 ppm (d, H-P(2-OMe-Ph)2(2-BF3-Ph), 1JPH
=
572 Hz). 31P{1H} NMR (162.0 MHz, CDCl3, 298 K): δ ꢀ11.8 ppm
(s, H-P(2-OMe-Ph)2(2-BF3-Ph)), Anal. Calcd for C20H19BF3O2P
3
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Organometallics
ARTICLE
(H2O)0.5: C, 60.18; H, 5.05. Found: C, 60.54; H, 5.29. MS (EI ꢀve):
m/z 370 [M+ ꢀ HF], 336 [M+ ꢀ HF ꢀ OMe].
to boron not observed. 11B{1H} NMR (128.4 MHz, CDCl3, 298 K):
δ +3.4 ppm (br s, C6H4BF3). 19F NMR (376.6 MHz, CDCl3, 298 K):
δ ꢀ133.1 ppm (br s, C6H4BF3). 31P{1H} NMR (162.0 MHz, CDCl3, 298
K): δ +41.2 ppm (s, PPh2(2-BF3-Ph). Anal. Calcd for C25H33N2BF3PPd:
C, 52.98; H, 5.87; N, 4.94. Found: C, 52.53; H, 5.80; N, 4.77. MS
(ESI +ve): m/z 567 [M+ + H], 547 [M+ ꢀ F], 499 [M+ ꢀ BF3].
[j-(P)ArPdMe(tmeda)], 6b. As for 6a, using PdMe2(tmeda)
(0.47 g, 1.9 mmol) and 5b (0.700 g, 1.9 mmol) yielded a hygroscopic,
white solid. Yield: 0.351 g (0.60 mmol, 32%). Single crystals suitable for
X-ray diffraction were grown via the slow evaporation of a chloroben-
zene solution. 1H NMR (400 MHz, CDCl3, 298 K): δ 0.20 ppm (br s,
3H, Pd-CH3), 2.10 (br s, 4H, 2 ꢁ NCH2 tmeda), 2.63 (br s, 12H, 4 ꢁ
NCH3 of tmeda), 3.49 (br s, 6H, OCH3 of aryl), 6.77 (br m, 2H, aryl
C-H), 6.99 (br m, 5H, aryl C-H), 7.32 (m, 3H, aryl C-H), 7.79 (br s, 1H,
aryl C-H), 8.05 (br s, 1H, aryl C-H). 1H NMR (400 MHz, CDCl3, 230
K): δ 0.08 ppm (d, 3H, Pd-CH3, 3JPH = 2 Hz), 2.01 (s, 4H, 2 ꢁ NCH2 of
tmeda), 2.55 (s, 6H, 2 ꢁ NCH3 of tmeda), 2.67 (s, 3H, NCH3 of tmeda),
3.02 (s, 3H, NCH3 of tmeda), 3.05 (s, 3H, OCH3), 3.09 (s, OCH3), 6.60
(m, 1H, aryl C-H), 6.78 (d of d, 1H, aryl C-H, 3JHH = 7 Hz, 4JHH = 2 Hz),
6.92 (t, 1H, aryl C-H, 3JHH = 7 Hz), 7.02 (m, 2H, overlapping, aryl C-H),
7.09 (t, 1H, aryl C-H, 3JHH = 7 Hz), 7.21 (1H, aryl C-H, 3JHH = 7 Hz),
7.36 (1H, aryl C-H, 3JHH = 7 Hz), 7.47 (1H, aryl C-H, 3JHH = 7 Hz), 7.71
(1H, aryl C-H, 3JHH = 7 Hz), 8.07 (m, 1H, aryl C-H), 8.59 (m, 1H, aryl
C-H). 13C{1H} NMR (75.5 MHz, CDCl3, 298 K, all resonances broad):
δ 6.0 ppm (Pd-CH3), 49.9 (CH3 of tmeda), 54.7 (OCH3), 60.4 (NCH2
of tmeda), 111.2, 120.1, 120.3, 124.8, 126.5, 128.4, 128.6, 129.8, 131.3,
134.6 (all aryl C-H), 138.5, 142.6, 160.9 (all aryl Cq). Carbon adjacent to
boron not observed. 11B{1H} NMR (128.4 MHz, CDCl3, 298 K):
δ +3.0 ppm (br s, C6H4BF3). 19F NMR (376.6 MHz, CDCl3, 298 K):
δ ꢀ133.1 ppm (br s, C6H4BF3). 31P{1H} NMR (162.0 MHz, CDCl3,
298 K): δ +36.0 ppm (s, P(2-OMe-Ph)2(2-BF3-Ph)). Anal. Calcd for
PHiPr2(2-BF3-Ph), 5c. In a manner similar to the synthesis of 1a/b,
a 100 mL round-bottomed flask was charged with a solution of iPr2P(2-
Br-Ph) (2.49 g, 9.2 mmol) in THF (40 mL) and cooled to ꢀ78 °C.
nBuLi (3.7 mL of a 2.5 M solution in hexanes, 9.2 mmol) was added
dropwise, with a concomitant color change to orange. The reaction was
left to stir at low temperature for two hours, before addition of
trimethylborate (4.7 mL, 46.0 mmol, 5 equiv). The reaction was allowed
to warm to room temperature, yielding a yellow solution, which was left
to stir at ambient temperature overnight. The reaction was quenched by
the addition of water (0.5 mL, 28.0 mmol), left to stir for 30 min, and all
volatiles were then removed by prolonged drying in vacuo to yield an off-
white solid. THF (40 mL) was condensed in, and the resultant slurry
treated with HBF4 (1.9 mL of a 48% solution in water, 9.2 mmol, 1
equiv), resulting in a clear, yellow solution. All volatiles were removed
after 1 h to yield a viscous, white paste. [1H NMR (400 MHz, CD3OD,
298 K): δ 1.22 ppm (d of d, 6H, CH3 of iPr, 3JPH = 19 Hz, 3JHH = 7 Hz),
1.42 ppm (d of d, 6H, CH3 of iPr, 3JPH = 19 Hz, 3JHH = 7 Hz), 3.03 (m,
1H, CH of iPr, 3JHH = 7 Hz), 7.45 (m, 1H, aryl C-H), 7.62 (m, 2H, aryl
C-H), 7.85 (m, 1H, aryl C-H). Boronic acid and phosphonium protons
not observed due to H/D exchange.] The compound thus obtained was
dissolved in methanol, and a solution of KHF2 (2.10 g, 27.0 mmol) in
water (15 mL) was added. The resulting white suspension was left to stir
for one hour, whereupon all volatiles were removed, and the product was
extracted in chloroform (3 ꢁ 50 mL). Removal of the solvent under
reduced pressure yielded the title compound as an off-white, waxy solid.
Yield: 1.22 g (4.7 mmol, 51%). 1H NMR (400 MHz, CDCl3, 298 K): δ
i
3
3
1.28 ppm (d of d, 6H, CH3 of Pr, JPH = 18 Hz, JHH = 7 Hz), 1.47
ppm (d of d, 6H, CH3 of iPr, 3JPH = 18 Hz, 3JHH = 7 Hz), 2.99 (m, 2H,
CH of iPr), 6.44 (d, v br, 1H, H-PiPr2(2-BF3-Ph), 1JPH = 464 Hz), 7.38
(m, 1H, aryl C-H), 7.47 (m, 1H, aryl C-H), 7.62 (m, 1H, aryl C-H), 8.01
(m, 1H, aryl C-H). 13C{1H} NMR (100.6 MHz, CDCl3, 298 K): δ 18.0
ppm (d, CH3 of iPr, 2JCP = 16 Hz), 22.2 (d, CH of iPr, 1JCP = 44 Hz),
115.1 (d, aryl Cq, 1JCP = 78 Hz), 125.8 (d, aryl C-H, 3JCP = 13 Hz), 127.1
C27H37N2BF3O2PPd (H2O)1.5: C, 49.60; H, 6.17; N, 4.66. Found: C,
3
49.39; H, 5.92; N, 4.28. MS (ESI ꢀve): m/z 543 [M+ ꢀ CH3 ꢀ BF3],
495 [M+ ꢀ tmeda ꢀ CH3].
[j-(P)i-PrPdMe(tmeda)], 6c. As for 6a, using PdMe2(tmeda)
(0.500 g, 2.0 mmol) and 5c (0.520 g, 2.0 mmol) yielded a white,
crystalline solid from a dichloromethane/diethyl ether solution. Yield:
0.279 g (0.60 mmol, 30%). 1H NMR (400 MHz, CDCl3, 298 K): δ 0.54
ppm (d, 3H, Pd-CH3, 3JPH = 2 Hz), 1.26 (d, 6H, 2 ꢁ CH3 of iPr, 3JHH = 7
Hz), 1.33 (d, 6H, 2 ꢁ CH3 of iPr, 3JHH = 7 Hz), 2.43 (s, 12H, 4 ꢁ NCH3
of tmeda), 2.59 (s, 4H, 2 ꢁ NCH2 of tmeda), 2.70 (m, 2H, 2 ꢁ CH of
iPr), 7.17 (t, 1H, aryl C-H, 3JHH = 7 Hz), 7.27ꢀ7.36 (m, 2H, aryl C-H),
8.02 (d of d, 1H, aryl C-H). 13C{1H} NMR (75.5 MHz, CDCl3, 298 K):
δ 0.39 ppm (app. s, Pd-CH3), 19.9, 20.4 (CH3 of iPr), 24.8 (d, CH of iPr,
1JCP = 25 Hz), 49.4 (CH3 of tmeda), 60.4 (CH2 of tmeda), 124.9 (d, aryl
C-H, 1JCP = 8 Hz), 128.6 (d, aryl Cq, 1JCP = 43 Hz), 128.8 (d, aryl C-H,
(d, aryl C-H, 3JCP = 13 Hz), 133.4 (aryl C-H), 134.6 (d, aryl C-H, 2JCP
=
16 Hz). Carbon adjacent to boron not observed. 11B{1H} NMR (128.4
MHz, CDCl3, 298 K): δ +2.6 ppm (br s, C6H4BF3). 19F NMR (376.6
MHz, CDCl3, 298 K): δ ꢀ136.4 ppm (br s, C6H4BF3). 31P NMR (162.0
MHz, CDCl3, 298 K): δ +30.2 ppm (br d, H-PiPr2(2-BF3-Ph), 1JPH
=
550 Hz). 31P{1H} NMR (162.0 MHz, CDCl3, 298 K): δ +30.2 ppm
(br s, H-PiPr2(2-BF3-Ph)). Anal. Calcd for C12H19BF3P: C, 55.00; H,
7.31. Found: C, 55.10; H, 7.21. MS (ESI ꢀve): m/z 261 [Mꢀ ꢀ H].
[j-(P)PhPdMe(tmeda)], 6a. A 100 mL round-bottomed flask was
charged with PdMe2(tmeda) (0.288 g, 1.14 mmol), 5a (0.379 g, 1.14
mmol), and stir bar. Dichloromethane (25 mL) was condensed in at
ꢀ78 °C. The flask was refilled with argon and allowed to warm to room
temperature, yielding effervescence and a color change from colorless to
yellow. The reaction was stirred one hour at room temperature before all
volatiles were removed in vacuo to yield a yellow, foamy residue.
Dissolution in chlorobenzene (in air) and leaving to stand yielded the
title compound as a crystalline, off-white solid. Yield: 0.457 g (0.81
mmol, 71%). Further material was obtained by concentration of the
supernatant. Single crystals suitable for X-ray diffraction were grown
from the slow cooling of a hot toluene solution. 1H NMR (400 MHz,
CDCl3, 298 K): δ 0.32 ppm (d, 3H, Pd-CH3, 3JPH = 4 Hz), 2.34 (s, 12H,
4 ꢁ NCH3 of tmeda), 2.58 (s, 4H, 2 ꢁ NCH2 of tmeda), 7.02 (m, 1H,
aryl C-H), 7.12 (m, 1H, aryl C-H), 7.26ꢀ7.37 (m, 7H, aryl C-H), 7.66
(m, 4H, aryl C-H), 8.10 (m, 1H, aryl C-H). 13C{1H} NMR (100.6 MHz,
CDCl3, 298 K): δ 5.6 ppm (d, Pd-CH3, 2JCP = 9 Hz), 49.0 (NCH3 of
tmeda) 60.5 (NCH2 of tmeda), 125.4 (d, aryl C-H, 2JCP = 9 Hz), 127.7
(d, aryl C-H, 2JCP = 9 Hz), 129.2, 129.8, 130.1, 130.2 (all aryl C-H), 130.7
(d, aryl Cq, 1JCP = 52 Hz), 132.1 (d, aryl Cq, 1JCP = 46 Hz), 135.4 (d, aryl
C-H, 2JCP = 11 Hz), 136.7 (d, aryl C-H, 2JCP = 11 Hz). Carbon adjacent
1JCP = 4 Hz), 129.5 (d, aryl C-H, 1JCP = 5 Hz), 136.2 (d, aryl C-H, 1JCP
=
17 Hz). Carbon adjacent to boron not observed. 11B{1H} NMR (128.4
MHz, CDCl3, 298 K): δ +3.1 ppm (br s, C6H4BF3). 19F NMR (376.6
MHz, CDCl3, 298 K): δ ꢀ132.4 ppm (br s, C6H4BF3). 31P{1H} NMR
(162.0 MHz, CDCl3, 298 K): δ +41.6 ppm (s, PiPr2(2-BF3-Ph). Anal.
Calcd for C19H37N2BF3PPd (CH2Cl2)0.25: C, 44.47; H, 7.27; N, 5.39.
3
Found: C, 44.49; H, 7.58; N, 5.55. MS (ESI +ve): m/z 431 [M+ ꢀ BF3],
415 [M+ ꢀ BF3 ꢀ Me].
[j-(P)PhPdMe(py)2], 7a. A 25 mL round-bottomed flask was
charged with 6a (0.52 g, 0.91 mmol) and dissolved in pyridine. The
reaction was stirred for two hours at ambient temperature before all
volatiles were removed in vacuo. The residue was washed with diethyl
ether and dried to yield the title compound as a yellow foam, which was
crystallized from dichloromethane. Yield: 0.360 g (0.59 mmol, 65%).
Single crystals suitable for X-ray diffraction were grown by the diffusion
1
of diethyl ether vapor into a chlorobenzene solution. H NMR (400
MHz, CDCl3, 298 K): δ 0.71 ppm (d, 3H, Pd-CH3, 3JPH = 2 Hz), 6.91
3
3
(t, 1H, aryl C-H, JHH = 7 Hz), 7.15 (t, H, aryl C-H, JHH = 7 Hz),
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7.33ꢀ7.46 (m, 11H, aryl C-H), 7.54 (m, 4H, aryl C-H), 7.74 (br s, 2H,
aryl C-H), 7.99 (m, 1H, aryl C-H), 8.64 (br s, 4H, aryl C-H). 13C{1H}
NMR (100.6 MHz, CDCl3, 298 K): δ 1.5 ppm (Pd-CH3), 124.9 (aryl
C-H), 126.0 (d, aryl C-H, 3JCP = 8 Hz), 127.8 (d, aryl C-H, 3JCP = 10 Hz),
129.5, 129.8 (both aryl C-H), 130.2 (d, aryl Cq, 1JCP = 51 Hz), 131.6 (d,
aryl C-H, 3JCP = 8 Hz), 132.7 (d, aryl Cq, 1JCP = 49 Hz), 134.6 (d, aryl
C-H, 2JCP = 17 Hz), 135.0 (d, aryl C-H, 2JCP = 11 Hz), 137.3, 150.4 (both
aryl C-H). Carbon adjacent to boron not observed. 11B{1H} NMR
(128.4 MHz, CDCl3, 298 K): δ +3.1 ppm (br s, C6H4BF3). 19F NMR
(376.6 MHz, CDCl3, 298 K): δ ꢀ137.2 ppm (br s, C6H4BF3). 31P{1H}
NMR (162.0 MHz, CDCl3, 298 K): δ +21.0 ppm (s, PPh2(2-BF3-Ph).
(d, aryl Cq, 1JCP = 52 Hz), 132.0 (d, aryl C-H, 4JCP = 3 Hz), 132.3 (d, aryl
C-H, 2JCP = 19 Hz), 132.5 (aryl C-H), 132.9 (d, aryl C-H, 2JCP = 17 Hz),
136.7 (d, aryl C-H, 3JCP = 11 Hz), 138.3 (aryl C-H), 159.1, 160.5 (both
aryl Cq). Carbon adjacent to boron not observed. 11B{1H} NMR (128.4
MHz, CDCl3, 298 K): δ +4.0 ppm (br s, C6H4BF3). 19F NMR (376.6
MHz, CDCl3, 298 K): δ ꢀ157.6 ppm (br s, C6H4BF3Pd). 31P{1H}
NMR (162.0 MHz, CDCl3, 298 K): δ +20.9 ppm (s, P(2-OMe-Ph)2(2-
BF3-Ph). Anal. Calcd for C28H30NBF3O2PPd (CH2Cl2)0.25: C, 53.10;
3
H, 4.83; N, 2.19. Found: C, 52.99; H, 4.86; N 2.25. MS (ESI +ve): m/z
598 [M+ ꢀ F], 491 [M+ ꢀ CH3 ꢀ lutidine].
[j2-(P,F)i-PrPdMe(lutidine)], 9c. As for 9a, using 6c (0.200 g, 0.40
mmol) and 2,6-lutidine (5 ꢁ 10 mL) yielded the title compound as an
off-white solid. Yield: 0.154 g (0.31 mmol, 76%). Single crystals suitable
for X-ray diffraction were grown by the diffusion of diethyl ether vapor
Anal. Calcd for C29H27N2BF3PPd (CH2Cl2)0.5: C, 56.05; H, 4.41;
3
N, 4.48. Found: C, 56.37; H, 4.51; N, 4.51. MS (ESI +ve): m/z 499
[M+ ꢀ py].
[j-(P)PhPdMe(bipy)], 8a. A solution of 2,20-bipyridine (0.055 g,
0.32 mmol) in dichloromethane (2 mL) was added, with stirring, to a
solution of 6a (0.200 g, 0.32 mmol) in dichloromethane (10 mL). The
reaction was left to stir overnight; the resultant white precipitate was
isolated by filtration. Yield: 0.131 g (0.22 mmol, 62%). 1H NMR (300
MHz, (CD3)2SO, 298 K): δ 0.73 ppm (s, 3H, Pd-CH3), 7.00 (t, 1H, aryl
1
into a chlorobenzene solution. H NMR (400 MHz, CDCl3, 298 K):
δ 0.62 ppm (d, 3H, Pd-CH3, 3JPH = 2 Hz), 1.27 (d of d, 6H, 2 ꢁ CH3 of
iPr, 3JPH = 16 Hz, 3JHH = 7 Hz), 1.32 (d of d, 6H, 2 ꢁ CH3 of iPr, 3JPH
=
16 Hz, 3JHH = 7 Hz), 2.52 (m, 2H, 2 ꢁ CH of iPr, overlapping), 3.19
(s, 6H, 2 ꢁ CH3 of lutidine), 7.16 (d, 2H, aryl C-H, 3JHH = 7 Hz), 7.24
(d, 1H, aryl C-H, 3JHH = 7 Hz), 7.41 (t, 1H, aryl C-H, 3JHH = 7 Hz), 7.49
(t, 1H, aryl C-H, 3JHH = 7 Hz), 7.61 (t, 1H, aryl C-H, 3JHH = 7 Hz), 7.92
(d, 1H, aryl C-H, 3JHH = 7 Hz). 13C{1H} NMR (100.6 MHz, CDCl3,
298 K): δ ꢀ8.9 ppm (q, Pd-CH3, 2JCF = 12 Hz), 18.4, 19.2 (both CH3 of
iPr), 25.5 (d, CH of iPr, 1JCP = 27 Hz), 26.0 (CH3 of lutidine), 122.8 (aryl
C-H), (d, aryl C-H, 3JCP = 6 Hz), 127.1, (d, aryl Cq, 1JCP = 40 Hz), 129.7,
130.7 (both aryl C-H), 133.5 (d, aryl C-H, 2JCP = 17 Hz), 138.6 (aryl C-
H), 159.0 (Cq of lutidine). Carbon adjacent to boron not observed.
11B{1H} NMR (128.4 MHz, CDCl3, 298 K): δ +3.1 ppm (br s,
C6H4BF3). 19F NMR (376.6 MHz, CDCl3, 298 K): δ ꢀ161.2 ppm (br
s, C6H4BF3Pd). 31P{1H} NMR (162.0 MHz, CDCl3, 298 K): δ +37.2
ppm (s, PiPr2(2-BF3-Ph)). Anal. Calcd for C20H30NBF3PPd: C, 49.06;
H, 6.18; N, 2.86. Found: C, 48.90; H, 6.26; N, 2.84. MS (ESI +ve): m/z
502 [M+ + Na], 489 [M+], 405 [M+ ꢀ lutidine + Na].
3
3
C-H, JHH = 7 Hz), 7.13 (t, 1H, aryl C-H, JHH = 7 Hz), 7.25ꢀ7.49
(m, 13H, aryl C-H), 7.69 (br s, 1H, aryl C-H), 8.05 (v br s, 2H, aryl C-H),
8.19 (t, 2H, aryl C-H, 3JHH = 7 Hz), 8.60 (d, 2H, aryl C-H, 3JHH = 7 Hz).
The compound is too poorly soluble to obtain satisfactory 13C NMR
spectra. 11B{1H} NMR (128.4 MHz, (CD3)2SO, 298 K): δ +3.4 ppm
(br s, C6H4BF3). 19F NMR (376.6 MHz, (CD3)2SO, 298 K): δ ꢀ130.3
ppm (br s, C6H4BF3). 31P{1H} NMR (162.0 MHz, (CD3)2SO, 298 K):
δ +40.3 ppm (s, PPh2(2-BF3-Ph)). HRMS (ESI +ve): calcd for
[M+] m/z 629.07430; found 629.07404.
[j2-(P,F)PhPdMe(lutidine)], 9a. A 50 mL round-bottomed flask
was charged with 6a (0.300 g, 0.51 mmol) and a stir bar. 2,6-Lutidine
(10 mL) was added via syringe, and the off-white slurry left to stir for
20ꢀ30 min. All volatiles were removed in vacuo, and the process was
repeated four times. The crude compound was washed with diethyl ether
(2 ꢁ 50 mL) and dried in vacuo to yield the title compound as an off-
white solid in essentially quantitative yield. Yield: 0.271 g (0.48 mmol,
[j2-(P,F)PhPdMe(DMAP)], 10a. A 10 mL round-bottomed flask
was charged with a solution of 9a (0.100 g, 0.18 mmol) in dichlor-
omethane (2 mL). A solution of DMAP (0.022 g, 0.18 mmol) in
dichloromethane (0.5 mL) was added. The reaction was left to stir for 30
min before all volatiles were removed in vacuo. The title compound was
obtained as a crystalline, white solid via the diffusion of diethyl ether
vapor into a chlorobenzene solution. Yield: 0.045 g (0.08 mmol, 44%).
1H NMR (400 MHz, CDCl3, 298 K): δ 0.71 ppm (d, 3H, Pd-CH3,
3JPH = 3 Hz), 3.07 (s, 6H, N(CH3)2 of DMAP), 6.46 (d, 2H, aryl C-H of
DMAP, 3JHH = 7 Hz), 6.91 (t, 1H, aryl C-H, 3JHH = 7 Hz), 7.18 (t, 1H,
aryl C-H, 3JHH = 7 Hz), 7.38 (m, 7H, aryl C-H), 7.56 (m, 4H, aryl C-H),
7.91 (m, 1H, aryl C-H), 8.23 (d, 2H, aryl C-H of DMAP, 3JHH = 7 Hz).
13C{1H} NMR (100.6 MHz, CDCl3, 298 K): δ 0.52 ppm (Pd-CH3),
39.1 (N(CH3)2 of DMAP), 107.0, 126.4 (both aryl C-H), 126.7 (d, aryl
1
94%). H NMR (400 MHz, CDCl3, 298 K): δ 0.52 ppm (d, 3H, Pd-
CH3, 3JPH = 3 Hz), 3.17 (s, 6H, 2 ꢁ CH3 of lutidine), 6.95 (m, 1H, aryl
C-H), 7.16ꢀ7.21 (m, 3H, aryl C-H), 7.42ꢀ7.48 (m, 7H, aryl C-H),
7.57ꢀ7.63 (m, 5H, aryl C-H), 7.91 (m, 1H, aryl C-H). 13C{1H} NMR
(100.6 MHz, CDCl3, 298 K): δ ꢀ2.9 ppm (q, Pd-CH3, 2JCF = 9 Hz),
26.4 (CH3 of lutidine), 122.6 (d, aryl C-H, 2JCP = 3 Hz), 126.9 (d, aryl C-
H, 2JCP = 8 Hz), 128.5 (d, aryl C-H, 2JCP = 11 Hz), 130.0 (aryl C-H),
130.4 (d, aryl C-H, 2JCP = 3 Hz), 130.8, 131.3 (both aryl C-H), 132.6 (d,
aryl C-H, 2JCP = 5 Hz), 133.4 (d, aryl Cq, 2JCP = 14 Hz), 134.0 (d, aryl C-
2
H, JCP = 12 Hz), 138.8 (aryl C-H), 158.9 (Cq of lutidine). Carbon
adjacent to boron not observed. 11B{1H} NMR (128.4 MHz, CDCl3,
298 K): δ +3.1 ppm (br s, C6H4BF3). 19F NMR (376.6 MHz, CDCl3,
298 K): δ ꢀ158.0 ppm (br s, C6H4BF3Pd). 31P{1H} NMR (162.0 MHz,
CDCl3, 298 K): δ +29.0 ppm (s, PPh2(2-BF3-Ph)). Anal. Calcd for
C26H26NBF3PPd: C, 56.00; H, 4.70; N, 2.51. Found: C, 55.90; H, 4.68;
N, 2.48. MS (ESI +ve): m/z 499 [M+ ꢀ 3F].
2
2
C-H, JCP = 11 Hz), 128.3 (d, aryl C-H, JCP = 11 Hz, and aryl C-H,
overlapping), 129.7, 130.2 (both aryl C-H), 131.9 (d, aryl C-H, 3JCP = 9
Hz), 132.5 (aryl C-H), 134.1 (d, aryl C-H, 2JCP = 11 Hz), 134.4, 148.9
(both aryl Cq). Carbon adjacent to boron not observed. 11B{1H} NMR
(128.4 MHz, CDCl3, 298 K): δ +3.4 ppm (br s, C6H4BF3). 19F NMR
(376.6 MHz, CDCl3, 298 K): δ ꢀ152.4 ppm (br s, C6H4BF3Pd).
31P{1H} NMR (162.0 MHz, CDCl3, 298 K): δ +36.7 ppm (s, PPh2
(2-BF3-Ph)). Anal. Calcd for C26H27N2BF3PPd: C, 54.53; H, 4.75; N,
4.89. Found: C, 54.75; H, 4.82; N, 4.83. MS (ESI +ve): m/z 576 [M+],
457 [M+ ꢀ DMAP].
[j2-(P,F)ArPdMe(lutidine)], 9b. As for 9a, using 6b (0.25 g, 0.40
mmol) and 2,6-lutidine (5 ꢁ 10 mL) yielded the title compound from
dichloromethane as an off-white solid. Yield: 0.194 g (0.32 mmol, 79%).
1H NMR (400 MHz, CDCl3, 298 K): δ 0.34 ppm (d, 3H, Pd-CH3,
3JPH = 3 Hz), 3.16 (s, 6H, 2 ꢁ CH3 of lutidine), 3.67 (s, 6H, 2 ꢁ OCH3),
6.92ꢀ7.13 (m, 8H, aryl C-H, overlapping), 7.33 (t, 1H, aryl C-H, 3JHH
=
Ethylene Reactions. A J. Young NMR tube was charged with 7a,
9a/b/c, or 10a (2.5 mg), and CDCl3 (0.4 mL) was added by vacuum
7 Hz), 7.40ꢀ7.52 (m, 4H, aryl C-H, overlapping), 7.59 (t, 1H, aryl C-H,
3JHH = 7 Hz), 7.82 (m, 1H, aryl C-H). 13C{1H} NMR (100.6 MHz,
1
transfer. A blank H NMR spectrum was recorded to assess complex
CDCl3, 298 K): δ ꢀ3.1 ppm (q, Pd-CH3, 2JCF = 14 Hz), 26.2 (CH3 of
purity. The sample was then degassed via repeated freezeꢀpumpꢀthaw
cycles at ꢀ78 °C. Ethylene was introduced from a vacuum line at one
atmosphere pressure, and the NMR tube sealed. The reaction was
monitored at regular (ca. 2 h) intervals to assess the course of the
1
lutidine), 55.1 (OCH3), 110.7 (aryl C-H), 117.6 (d, aryl Cq, JCP
=
3
53 Hz), 120.6 (d, aryl C-H, JCP = 11 Hz), 122.4 (aryl C-H), 125.6
3
4
(d, aryl C-H, JCP = 11 Hz), 129.0 (d, aryl C-H, JCP = 3 Hz), 130.2
4247
dx.doi.org/10.1021/om2004095 |Organometallics 2011, 30, 4236–4249

Organometallics
ARTICLE
reaction. Product distribution was determined by 1H NMR integration
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X-ray Crystallography. Single crystals of 1b, 2a, 3a, 5a, 6a, 6b, 7a,
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Diffraction data for 1b, 2a, 3a, 5a, 6b, 7a, and 9c were collected on a
Bruker P4/RA/SMART 1000 CCD diffractometer using Mo KR
radiation at ꢀ100 °C. Data for 6a were collected on a Bruker PLAT-
FORM/SMART 1000 CCD diffractometer using graphite-monochro-
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absorption using SADABS,45 and the structures solved in SHELXS9746
and refined using full-matrix least-squares on F2 using SHELXL97.46
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bond lengths and angles, and crystallographic data/processing
parameters for all structures. Crystallographic information files
for 1b, 2a, 3a, 5a, 6a, 6b, 7a, and 9c. This material is available free
of charge via the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION
Corresponding Author
*E-mail: wpiers@ucalgary.ca. Tel: (+1) 403 220 5746.
’ ACKNOWLEDGMENT
We thank LANXESS GmbH for their generous support of
this work.
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