Synthesis and reactivity of the fluoro complex trans -[Pd(F)(4-C 5NF4)(iPr2PCH2CH 2OCH3)2]: C-F bond formation and catalytic C-F bond activation reactions

Article abstract of DOI:10.1021/om200998d

The reaction of [Pd(Me)₂(tmeda)] (tmeda = N,N,N′,N′- tetramethylethylendiamine) with the phosphine ⁱPr₂PCH ₂CH₂OCH₃ resulted in the formation of the palladium(0) complex [Pd(ⁱPr₂PCH₂CH ₂OCH₃)₂] (1). Treatment of 1 with pentafluoropyridine at room temperature yielded the C-F activation product trans-[Pd(F)(4-C₅NF₄)(ⁱPr₂PCH ₂CH₂OCH₃)₂] (2). The triflato and bromo complexes trans-[Pd(OTf)(4-C₅NF₄)( ⁱPr₂PCH₂CH₂OCH₃) ₂] (4) and trans-[Pd(Br)(4-C₅NF₄)( ⁱPr₂PCH₂CH₂OCH₃) ₂] (5) could be prepared on reaction of complex 2 with EtOTf or 3-bromopropene, respectively. Treatment of 2 with Me₃SiCl or HBpin (HBpin = 4,4,5,5-tetramethyl-1,3,2-dioxaborolane, pinacolborane) effects the formation of trans-[Pd(Cl)(4-C₅NF₄)(ⁱPr ₂PCH₂CH₂OCH₃)₂] (6) and trans-[Pd(H)(4-C₅NF₄)(ⁱPr₂PCH ₂CH₂OCH₃)₂] (7). In catalytic experiments pentafluoropyridine could be converted into the 4-aryl- tetrafluoropyridines (8, aryl = Ph; 9, aryl = Tol) and into 2,3,5,6- tetrafluoropyridine in the presence of the boronic acids PhB(OH)₂, TolB(OH)₂, or HBpin when 5 mol % of 2 is employed as catalyst.

Full text of DOI:10.1021/om200998d

Article
pubs.acs.org/Organometallics
Synthesis and Reactivity of the Fluoro Complex trans-[Pd(F)(4-
C5NF4)(iPr2PCH2CH2OCH3)2]: C−F Bond Formation and Catalytic C−F
Bond Activation Reactions
David Breyer, Thomas Braun,* and Paul Klaring
̈
Department of Chemistry, Humboldt-Universitat zu Berlin, Brook-Taylor-Straße 2, 12489 Berlin, Germany
̈
S
* Supporting Information
ABSTRACT: The reaction of [Pd(Me)2(tmeda)] (tmeda =
N,N,N′,N′-tetramethylethylendiamine) with the phosphine
iPr2PCH2CH2OCH3 resulted in the formation of the
palladium(0) complex [Pd(iPr2PCH2CH2OCH3)2] (1). Treat-
ment of 1 with pentafluoropyridine at room temperature
yielded the C−F activation product trans-[Pd(F)(4-C5NF4)-
(iPr2PCH2CH2OCH3)2] (2). The triflato and bromo com-
plexes trans-[Pd(OTf)(4-C5NF4)(iPr2PCH2CH2OCH3)2] (4)
and trans-[Pd(Br)(4-C5NF4)(iPr2PCH2CH2OCH3)2] (5)
could be prepared on reaction of complex 2 with EtOTf or
3-bromopropene, respectively. Treatment of 2 with Me3SiCl or HBpin (HBpin = 4,4,5,5-tetramethyl-1,3,2-dioxaborolane,
pinacolborane) effects the formation of trans-[Pd(Cl)(4-C5NF4)(iPr2PCH2CH2OCH3)2] (6) and trans-[Pd(H)(4-C5NF4)-
(iPr2PCH2CH2OCH3)2] (7). In catalytic experiments pentafluoropyridine could be converted into the 4-aryl-tetrafluoropyridines
(8, aryl = Ph; 9, aryl = Tol) and into 2,3,5,6-tetrafluoropyridine in the presence of the boronic acids PhB(OH)2, TolB(OH)2, or
HBpin when 5 mol % of 2 is employed as catalyst.
zene in the presence of alkylsilanes.19 We demonstrated that
INTRODUCTION
Fluoroorganic compounds display an increasing field of
■
trans-[Pd(H)(4-C5NF4)(PiPr3)2] catalyzes the hydrodefluori-
applications.1 For instance, fluorinated entities are found in
nation of pentafluoropyridine to give 2,3,5,6-tetrafluoropyridine
on using HBpin as hydrogen source.24 Catalytic C−C coupling
reactions based on C−F activation reactions of highly
fluorinated aromatics are also still rare.3,4,7,12,13,20,21 In a very
recent example, Love et al. described cross-coupling reactions at
fluoroarenes in the presence of Ni(COD)2/PPh3 and organo-
boron reagents.21 Radius et al. reported Suzuki-type cross-
coupling reactions of perfluorotoluene and perfluorinated
biphenyl on using phenyl boronic acids in the presence of a
nickel(II)carbene complex as catalyst.13
pharmaceuticals, agrochemicals, or advanced materials.2 One
particular way to access fluorinated organic building blocks
comprises transition metal mediated carbon−fluorine bond
activation reactions on using easily available highly fluorinated
precursors.3−11 A hydrodefluorination or functionalization of a
fluorinated moiety in the coordination sphere of a transition
metal, e.g., at palladium, nickel, or rhodium, may yield
fluorinated compounds that are difficult to access or even not
accessible otherwise.3−5,7−17 For example, the oxidative
addition of a fluorinated precursor at nickel or palladium
results in the generation of fluoro complexes.4 After
replacement of the fluoro ligand by a hydrido or an organyl
ligand a new fluorinated molecule can be formed by reductive
elimination. Such model reactions led to the development of
unique hydrodefluorination and cross-coupling reac-
tions.3,4,7,10−13,18−22 Note that the replacement of a fluoro
ligand usually involves the formation of strong E−F bonds (E =
H, Si, Al, B), which is often the thermodynamic driving force
for the catalytic reactions.3,23
It has been proposed that complexes that bear hemilabile
coordinating phosphines can be more efficient in cross-
coupling reactions when compared with their analogues that
do not possess any hemilabile coordinating moiety.25 Thus, it
was demonstrated that palladium/ligand systems such as
Pd(dba)2 in combination with 2-(2′-dicyclohexylphosphino-
phenyl)-2-methyl-1,3-dioxolane represent a very efficient
catalyst for Suzuki−Miyaura cross-coupling reactions.26 Mil-
stein et al. studied the influence of the hemilabile coordinating
ligand di-tert-butyl(2,6-dimethoxybenzyl)phosphine (dmobp)
bearing a methoxy group as additional coordinating moiety on
catalytic Suzuki−Miyaura cross-coupling reactions.27 They
The transition metal mediated C−F bond cleavage of
perfluorinated arenes and a subsequent or concomitant
hydrodefluorination reaction have been intensively stud-
ied.18,19,22 For example, Whittlesey et al. reported recently
that ruthenium hydrido fluoro complexes are suitable for the
catalytic conversion of hexafluorobenzene into pentafluoroben-
Special Issue: Fluorine in Organometallic Chemistry
Received: October 17, 2011
Published: January 4, 2012
© 2012 American Chemical Society
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showed that the employment of the catalyst [Pd(dmobp)2]
resulted in much higher yields than the reaction with an
analogous catalyst, [Pd(tmbp)2] (tmbp = di-tert-butyl(2,4,6-
trimethylbenzyl)phosphine), which lacks the methoxy moiety.
In this work we present studies on the C−F activation of
pentafluoropyridine at [Pd(iPr2PCH2CH2OCH3)2] (1). Stoi-
chiometric reactions yielded the fluoro complex trans-[Pd(F)-
(4-C5NF4)(iPr2PCH2CH2OCH3)2] (2) by oxidative addition.
The latter can act as a fluorinating agent and converts EtOTf or
3-bromopropene into the corresponding fluorides. We also
show that 2 catalyzes hydrodefluorination and cross-coupling
reactions of pentafluoropyridine.
RESULTS AND DISCUSSION
■
1. C−F Activation of Pentafluoropyridine at Palla-
dium. The reaction of [Pd(Me)2(tmeda)] with
iPr2PCH2CH2OCH3 led to the formation of [Pd-
(iPr2PCH2CH2OCH3)2] (1) (Scheme 1). The 31P{1H} NMR
Figure 1. DFT-optimized structure for trans-[Pd-
(iPr2PCH2CH2OCH3)2] (1).
Scheme 1. Synthesis of the Fluoro Complex 2
presence of the tetrafluoropyridyl ligand with the palladium at
the 4-position. A broad signal at −316.5 ppm is characteristic
for the fluoro ligand at the metal center.9 The H NMR
1
spectrum shows the expected signals for the metal-bonded
i
phosphine Pr2PCH2CH2OCH3. The molecular structure of 2
was confirmed by X-ray crystal structure analysis (Figure 2).
spectrum of the reaction solution shows a singlet at 30.1 ppm
for the phosphines in the mutually trans position. The 1H NMR
spectrum reveals the presence of one equivalent of free tmeda,
two coordinated phosphines, and the formation of ethane.
Complex 1 is highly reactive and could not be isolated. Because
complex 1 does not reveal any dynamic behavior on the NMR
time scale and complex [Pd(PiPr3)2] is also stable in solution,
we assume that the methoxy entities in 1 do not coordinate at
the metal center. In addition, geometry optimizations on using
DFT calculations also indicate that the methoxy groups do not
coordinate at the metal center in the gas phase (Figure 1), even
when the starting geometry involves coordinated methoxy
groups. Note that the above-mentioned catalyst [Pd(dmobp)2]
also does not exhibit any methoxy group coordination.27
Treatment of [Pd(iPr2PCH2CH2OCH3)2] (1) with penta-
fluoropyridine at room temperature gave the palladium fluoro
complex trans-[Pd(F)(4-C5NF4)(iPr2PCH2CH2OCH3)2] (2)
within 4 h (Scheme 1). The structure that is proposed for 2
Figure 2. ORTEP diagram of 2; ellipsoids are drawn at the 50%
probability level; hydrogen atoms are omitted for clarity; only one of
two crystallographically independent molecules is shown.
Complex 2 can be crystallized from n-hexane at 0 C. Selected
bond lengths and angles are summarized in Table 1. The unit
cell contains two crystallographically independent molecules
that exhibit only minor structural differences, except for a
disorder of a methoxy group in one of the phosphines.
Therefore, only one molecule will be discussed. The structure
shows the expected trans disposition of the phosphine ligands
with an approximately square-planar coordination geometry at
the metal center. The palladium−fluorine distance in 2 is
2.028(2) Å. For comparison, the Pd−F length in trans-
[Pd(F)(4-C5NF4)(PiPr3)2] (3) is 2.0158(16) Å, and the one in
trans-[Pd(F)(Ph)(PPh3)2] is 2.085(3) Å.9,28
1
is supported by the 31P{1H}, 19F, and H NMR data. The
31P{1H} NMR spectrum exhibits a doublet of triplets at 30.1
2
ppm with a coupling constant of JPF = 17.4 Hz for the
phosphorus atoms to the metal-bound fluorine and of 4JPF = 4.5
Hz to the fluorine atoms in the ortho position at the
tetrafluoropyridyl ligand. The 19F NMR spectrum shows two
multiplets at −98.0 and −118.8 ppm, which indicates the
It is worth mentioning that the C−F activation reaction of
pentafluoropyridine at palladium to yield trans-[Pd(F)(4-
C5NF4)(iPr2PCH2CH2OCH3)2] (2) occurs at relatively mild
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presence of three signals in the 19F NMR spectrum results from
the tetrafluoropyridyl ligand (−95.6 ppm, −117.9 ppm) and
the triflato ligand (−77.5 ppm). The formation of EtF was
monitored by 19F NMR spectroscopy (−211.9 ppm).34 The
31P{1H} NMR spectrum of complex 4 shows a signal at 34.8
ppm for the phosphines in a mutually trans position.
A solution of 2 also reacted with 3-bromopropene to
produce the bromo complex trans-[Pd(Br)(4-C5NF4)-
(iPr2PCH2CH2OCH3)2] (5) and 3-fluoropropene within 4.5
h at 80 °C (Scheme 2). In addition the 19F NMR spectrum
reveals the formation of 3-fluoropropene (−217.8 ppm).35 The
reaction of 2 with Me3SiCl yielded the chloro complex trans-
[Pd(Cl)(4-C5NF4)(iPr2PCH2CH2OCH3)2] (6) and Me3SiF
(Scheme 2).36 Compounds 5 and 6 are characterized by their
1H, 19F, and 31P{1H} NMR spectra. Their assignment as 4-
tetrafluoropyridyl derivatives is again based on the presence of
two signals in the 19F NMR spectra. The trans arrangement of
the phosphines in 5 and 6 is indicated by one signal in the
31P{1H} NMR spectra.
Table 1. Selected Bond Lengths (Å) and Angles (deg) in 2
with the Estimated Standard Deviations in Parentheses
bond
length
bond
length
Pd(1)−C(19)
Pd(1)−F(1)
Pd(1)−P(1)
Pd(1)−P(2)
N(1)−C(21)
N(1)−C(22)
C(19)−C(20)
bond
1.982(3)
2.028(2)
2.332(2)
2.329(2)
1.288(6)
1.320(6)
1.402(5)
angle
C(19)−C(23)
C(20)−C(21)
C(22)−C(23)
C(20)−F(2)
C(21)−F(3)
C(22)−F(4)
C(23)−F(5)
bond
1.377(4)
1.372(5)
1.390(5)
1.342(5)
1.343(5)
1.336(5)
1.363(4)
angle
C(19)−Pd(1)−P(1)
F(1)−Pd(1)−P(1)
C(19)−Pd(1)−F(1)
P(1)−Pd(1)−P(2)
C(20)−C(19)−Pd(1)
C(23)−C(19)−Pd(1)
92.09(8)
88.77(5)
177.54(10)
175.23(3)
124.6(2)
121.8(2)
C(23)−C(19)−C(20)
C(21)−C(20)−C(19)
N(1)−C(21)−C(20)
C(21)−N(1)−C(22)
N(1)−C(22)−C(23)
C(19)−C(23)−C(22)
113.6(3)
120.8(4)
124.5(4)
116.9(3)
122.9(4)
121.3(4)
conditions (4 h, room temperature).7,29 For the activation of
The molecular structure of 6 was confirmed by X-ray crystal
structure analysis. Complex 6 was crystallized from n-hexane at
0 °C (Figure 3). The molecule crystallizes in the space group
C2/c and is located on a C2 axis. Selected bond lengths and
i
pentafluoropyridine at [Pd(PR3)2] (R = Cy, Pr) to give trans-
[Pd(F)(4-C5NF4)(PCy3)2] or trans-[Pd(F)(4-C5NF4)(PiPr3)2]
(3) more drastic reaction conditions are reported (4−6 h, 90−
100 °C).9 We also found that after 4 days at room temperature
the formation of trans-[Pd(F)(4-C5NF4)(PiPr3)2] (3) was
completed to 70%. Apparently, the presence of the methoxy
group at the phosphine has an accelerating influence on the
C−F activation step. Note also that in contrast to the observed
activation of pentafluoropyridine at the 4-position, an activation
at the 2-position was observed at nickel, e.g., to give trans-
[Ni(F)(2-C5NF4)(PEt3)2].3,4 For the latter case a phosphine-
assisted mechanism for the C−F activation step was
proposed.4a,5,18f,30,31 However, a concerted oxidative addition
or a nucleophilic attack of 1 at the fluorinated pyridine is also
conceivable.4a−c,g,5,9,32 Although there are some other ex-
ceptions at rhodium, titanium, or zirconium, pentafluoropyr-
dine is generally activated at the 4-position.8,15,33
2 . R e a c t i v i t y o f t r a n s - [ P d ( F ) ( 4 - C 5 N F 4 ) -
(iPr2PCH2CH2OCH3)2] (2). Treatment of 2 with EtOTf gave
the triflato complex trans-[Pd(OTf)(4-C5 NF4 )-
(iPr2PCH2CH2OCH3)2] (4) within 4 h (Scheme 2). Complex
4 was characterized by its NMR spectroscopic data. The
Scheme 2. Reactivity of 2 toward Electrophilic Compounds
Figure 3. ORTEP diagram of 6; ellipsoids are drawn at the 50%
probability level; hydrogen atoms are omitted for clarity.
angles are summarized in Table 2. Complex 6 reveals a square-
planar structure with a trans configuration of the phosphines as
well as of the tetrafluoropyridyl and the chloro ligand. The
Pd−Cl distance Pd(1)−Cl(1) of 2.3599(5) Å and the distance
to the tetrafluoropyridyl ligand Pd(1)−C(1) of 2.0017(18) Å
are in a similar range as the corresponding separations in the
palladium chloro complex trans-[Pd(Cl)(4-C5NF4)(PiPr3)2]
(Pd(1)−Cl(1) = 2.3625(4) Å, Pd(1)−C(1) = 2.012(2) Å).10
The production of EtF and 3-fluoropropene involves the
formation of Csp3−F bonds mediated by a metal-fluoro
complex. Note that EtF and 3-fluoropropene can also be
generated by reaction of EtOTf and 3-bromopropene with CsF
at room temperature within 24 h (EtF) or at 110 °C within 50
min (3-fluoropropene).35,37 Transition metal mediated for-
mation of Csp3−F bonds is also reported in the literature.38,39
Gouverneur et al. demonstrated the palladium-catalyzed allylic
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Next we turned our attention to catalytic C−C coupling
reactions. Representative results are summarized in Scheme 4
and Table 3. Treatment of pentafluoropyridine with boronic
acids in the presence of 5 mol % trans-[Pd(F)(4-C5NF4)-
Table 2. Selected Bond Lengths (Å) and Angles (deg) in 6
with the Estimated Standard Deviations in Parentheses
a
bond
length
bond
length
Pd(1)−C(1)
Pd(1)−Cl(1)
N(1)−C(3)
C(1)−C(2)
bond
2.0017(18)
2.3599(5)
1.310(2)
1.3838(17)
angle
C(2)−C(3)
Pd(1)−P(1)
C(2)−F(1)
C(3)−F(2)
bond
1.383(2)
2.3455(3)
1.3506(18)
1.3399(19)
angle
Scheme 4. Catalytic Cross-Coupling Reactions of
Pentafluoropyridine
C(1)−Pd(1)−P(1)
Cl(1)−Pd(1)−P(1)
P(1)−Pd(1)−P(1#)
C(2)−C(1)−Pd(1)
94.003(8)
85.997(8)
171.995(17)
123.50(9)
C(2)−C(1)−C(2#)
C(3)−C(2)−C(1)
N(1)−C(3)−C(2)
C(3)−N(1)−C(3#)
113.01(18)
121.65(15)
124.00(16)
115.69(19)
a
Symmetry transformation used to generate equivalent atoms: −x, y,
−z+1/2 .
fluorination of 2- and 3-substituted propenyl esters with
TBAF·(tBuOH)4 (TBAF = tetra-n-butylammonium fluoride)
as nucleophilc fluorination agent.40 Doyle et al. used AgF for
the enantioselective fluorination of allylic chlorides at Pd.41
Both conversions presumably proceed via an external fluoride
attack at an allyl ligand. However, C−F bond formations via
transition metal fluoro complexes are rare, and most of them
comprise the generation of Csp2−F bonds.42,43 Buchwald et al.
described the catalytic generation of aryl fluorides from aryl
triflates via palladium(II) fluoro complexes.44 The research
groups of Ritter and Sanford reported the formation of Csp2−F
bonds from palladium(IV) fluoro complexes.39,45
3. Catalytic Hydrodefluorination and Cross-Coupling
Reactions of Pentafluoropyridine. Treatment of penta-
fluoropyridine with HBpin in the presence of 5 mol % of trans-
[Pd(F)(4-C5NF4)(iPr2PCH2CH2OCH3)2] (2) and NEt3 gave
the hydrodefluorination product 2,3,5,6-tetrafluoropyridine
with a yield of 80% after 48 h (Scheme 3). For comparison,
with trans-[Pd(F)(4-C5NF4)(PiPr3)2] (3) as a catalyst 2,3,5,6-
Table 3. Cross-Coupling Reactions of Pentafluoropyridine
with Boronic Acids on Using 2 As Catalyst
entry
boronic acid
product
base
yield (%)
TON
a
1
2
3
4
5
PhB(OH)2
PhB(OH)2
PhB(OH)2
PhB(OH)2
TolB(OH)2
8
8
8
8
9
Cs2CO3
CsF
37
4
4
a
38
a
NEt3
NEt3
NEt3
44
4
b
59
12
9
b
48
a
b
10 mol % of 2, THF, 60 °C, 24 h. 5 mol % of 2, THF, 60 °C, 3 d;
yields have been determined by 19F NMR spectroscopy on using a
capillary that contained fluorobenzene as external standard; TON =
turnover number.
(iPr2PCH2CH2OCH3)2] (2) as catalyst and NEt3 as a base
afforded with regioselectively 4-phenyltetrafluoropyridine (8)
and 4-tolyltetrafluoropyridine (9) in 59% and 48% yield,
respectively. A reaction of 2 with stoichiometric amounts of
PhB(OH)2 led to the generation of 1 and 8. No intermediate
could be detected by NMR spectroscopy. The compounds 8
and 9 were identified by comparison of their mass spectra and
19F NMR spectroscopic data with the literature.48,49 For the
formation of 8, we also tested the influence of several bases and
observed that NEt3 led to the highest yield (Table 3). Note that
no generation of palladium black or fluorinated phosphoranes
was observed.5,9,12,29−31,46,47 The catalytic formation of 8 in the
presence of 5 mol % 2, NEt3, and Hg gives 8 in 32% yield,
which is an indication that the catalysis is homogeneous and
not heterogeneous in nature.50
Scheme 3. Catalytic Hydrodefluorination of
Pentafluoropyridine
tetrafluoropyridine was furnished in 60% yield under the same
conditions. In both cases no formation of fluorinated
phosphoranes were observed. Note that free phosphine also
reacts with pentafluoropyridine to give 2,3,5,6-tetrafluoropyr-
idine and fluorinated phosphoranes.5,9,12,29−31,46,47
Importantly, there are only a few known catalytic routes for
the synthesis of 4-aryl-tetrafluoropyridines, and all of them are
based on C−H activation reactions of 2,3,5,6-tetrafluoropyr-
idine.48,49,51 Some rare examples for cross-coupling reactions
that involve the cleavage of a C−F bond at highly fluorinated
aromatics have been reported.3,7,12,13,20,21
In an NMR experiment a solution of 2 was reacted with
HBpin to produce the palladium hydrido complex trans-
[Pd(H)(4-C5NF4)(iPr2PCH2CH2OCH3)2] (7) and FBpin. The
latter is most probably an intermediate in the hydro-
defluorination reactions that are describe above.24 The
CONCLUSIONS
■
1
structure that is proposed for 7 is supported by the H, 19F,
In conclusion, we presented studies on the synthesis and
reactivity of the palladium fluoro complex trans-[Pd(F)(4-
C5NF4)(iPr2PCH2CH2OCH3)2] (2). Complex 2 can be
synthesized by carbon−fluorine-bond activation of pentafluoro-
pyridine. It catalyzes cross-coupling as well as hydrodefluori-
nation reactions of pentafluoropyridine to yield 4-phenyl-
tetrafluoropyridine (7), 4-tolyltetrafluoropyridine (8), or
2,3,5,6-tetrafluoropyridine by C−F activation. It should be
mentioned that the bromo complex 5 or chloro complex 6
and 31P{1H} NMR data. The hydrido ligand gives a triplet at
−8.88 ppm (2JPH = 10.5 Hz) in the 1H NMR spectrum. The 19F
NMR spectrum reveals two signals, at −100.0 and −117.0 ppm.
The 31P{1H} NMR spectrum shows a singlet at 43.4 ppm.
Heating of a solution containing 7 to 60 °C led to the reductive
elimination of 2,3,5,6-tetrafluoropyridine and the formation of
[Pd(iPr2PCH2CH2OCH3)2] (1), as confirmed by NMR
spectroscopy.
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1
with n-hexane to give a colorless solid. Yield: 62 mg (92%). H NMR
(300.1 MHz, C6D6) δ 3.25 (m, t in the 1H{31P} NMR spectrum, 3JHH
= 6.5 Hz, 4 H, CH2OCH3), 3.07 (s, 6 H, OCH3), 2.17 (m, sept in the
1H{31P} NMR spectrum, 3JHH = 7.1 Hz, 4 H, PCH), 1.70 (m, t in the
cannot be applied as catalysts in any of the described catalytic
conversions. This observation reflects the fact that fluoro
complexes often exhibit a higher reactivity than their chloro or
bromo counterparts.8,10−15,17,52 In addition, it was shown that
1H{31P} NMR spectrum, 3JHH = 6.5 Hz, 4 H, PCH2), 1.06 (dd, 3JPH
=
i
the phosphine ligands Pr2PCH2CH2OCH3 in 1 and 2 have a
3
3
15.8 Hz, JHH = 8.2 Hz, 12 H, PCHCH3), 0.84 (dd, JPH = 14.9 Hz,
superior influence on the C−F bond cleavage and catalytic
C−F activation reactions of pentafluoropyridine when
compared to the corresponding PiPr3 complexes. However,
the role of the methoxy function in these conversions is, so far,
unclear.
3JHH = 7.5 Hz, 12 H, PCHCH3); the JHH coupling constants were
3
confirmed from 1H{31P} NMR spectra; 19F NMR (282.4 MHz, C6D6)
δ −77.5 (s, 3 F), −95.6 (m, 2 F), −117.9 (m, 2 F); 31P{1H} (121.5
MHz, C6D6) δ 34.8 (s, br). Anal. Calcd for C23H42NF7O5P2PdS: C,
38.03; H, 5.58; N, 1.85. Found: C, 38.47; H, 5.61; N, 1.75.
Preparation of trans-[Pd(Br)(4-C5NF4)(iPr2PCH2CH2OCH3)2]
(5). Complex trans-[Pd(F)(4-C5NF4)(iPr2PCH2CH2OCH3)2] (2)
(53 mg, 0.085 mmol) was dissolved in C6H6 (3 mL) to give a yellow
solution. After addition of CH2CHCH2Br (37 μL, 0.43 mmol), the
reaction mixture was stirred for 4.5 h at 80 °C. After cooling to room
temperature, the reaction mixture was filtered. The formation of
CH2CH2CH2F was observed by 19F NMR spectroscopy.35 The
volatiles were then removed from the filtrate under vacuum to give an
orange solid. Yield: 56 mg (96%). 1H NMR (300.1 MHz, C6D6) δ 3.26
(m, t in the 1H{31P} NMR spectrum, 3JHH = 7.1 Hz, 4 H, CH2OCH3),
EXPERIMENTAL METHODS
■
General Methods. The synthetic work was carried out on a
Schlenk line under Ar. All solvents were purified and dried by
conventional methods and distilled under argon before use. Benzene-
d6 and THF-d8 were dried over Na/K prior to use. [Pd(Me)2(tmeda)]
and iPr2PCH2CH2OCH3 were prepared according to the litera-
ture.53,54
The NMR spectra were recorded at 26 °C on a Bruker DPX 300
spectrometer. The 1H NMR chemical shifts were referenced to
1
3.02 (s, 6 H, OCH3), 2.36 (m, sept in the H{31P} NMR spectrum,
residual C6D5H at 7.15 ppm and THF-d7 at 1.72 or 3.58 ppm. The 19
F
3JHH = 7.1 Hz, 4 H, PCH), 1.79 (m, t in the 1H{31P} NMR spectrum,
3JHH = 7.1 Hz, 4 H, PCH2), 1.19 (dd, 3JPH = 15.8 Hz, 3JHH = 7.1 Hz, 12
NMR spectra were referenced to external C6F6 at −162.9 ppm. The
31P{1H} NMR spectra were referenced externally to H3PO4 at 0.0
ppm. Microanalyses were carried out using a HEKAtech EURO EA
3000 elemental analyzer.
3
3
H, PCHCH3), 0.92 (dd, JPH = 14.9 Hz, JHH = 7.1 Hz, 12 H,
PCHCH3); the 3JHH coupling constants were confirmed from 1H{31P}
NMR spectra; 19F NMR (282.4 MHz, C6D6) δ −97.0 (m, 2 F),
Formation of [Pd(iPr2PCH2CH2OCH3)2] (1). A solution of
[Pd(Me)2(tmeda)] (89 mg, 0.353 mmol) in C6H6 (3 mL) was
treated with iPr2PCH2CH2OCH3 (139 μL, 0.741 mmol). The reaction
4
−117.7 (m, 2 F); 31P{1H} (121.5 MHz, C6D6) δ 28.3 (t, JPF = 3.8
Hz). Anal. Calcd for C23H42NBrF4O2P2Pd: C, 40.10; H, 6.15; N, 2.03.
Found: C, 40.01; H, 6.38; N, 1.56.
mixture was stirred for 1 h. Spectroscopic data for 1: H{31P} NMR
1
Preparation of trans-[Pd(Cl)(4-C5NF4)(iPr2PCH2CH2OCH3)2]
(6). Me3SiCl (39 μL, 0.305 mmol) was added to a solution of trans-
[Pd(F)(4-C5NF4)(iPr2PCH2CH2OCH3)2] (2) (38 mg, 0.061 mmol)
in THF (3 mL). After stirring for 5 h the reaction mixture was filtered.
The volatiles were then removed from the filtrate under vacuum. A
(300.1 MHz, C6D6) δ 3.90 (t, 3JHH = 8.2 Hz, 4 H, CH2OCH3), 3.23 (s,
6 H, OCH3), 1.79 (t, 3JHH = 8.2 Hz, 4 H, PCH2), 1.65 (sept, 3JHH = 7.0
Hz, 4 H, PCH), 1.21 (d, 3JHH = 7.0 Hz, 12 H, PCHCH3), 1.07 (d, 3JHH
= 7.0 Hz, 12 H, PCHCH3); 31P{1H} (121.5 MHz, C6D6) δ 30.1 (s).
Preparation of trans-[Pd(F)(4-C5NF4)(iPr2PCH2CH2OCH3)2] (2).
A solution of [Pd(Me)2(tmeda)] (926 mg, 3.67 mmol) in THF (10
1
colorless solid was obtained. Yield: 39 mg (98%). H NMR (300.1
1
3
MHz, C6D6) δ 3.28 (m, t in the H{31P} NMR spectrum, JHH = 7.1
Hz, 4 H, CH2OCH3), 3.03 (s, 6 H, OCH3), 2.27 (m, sept in the
1H{31P} NMR spectrum, 3JHH = 7.2 Hz, 4 H, PCH), 1.74 (m, t in the
i
mL) was treated with Pr2PCH2CH2OCH3 (1.45 mL, 7.71 mmol).
After stirring the reaction mixture for 1 h, pentafluoropyridine (0.43
mL, 4.40 mmol) was added. The reaction mixture was stirred for
another 4.5 h, and the volatiles were removed under vacuum. The
remaining dark red oil was washed with n-hexane (5 mL) at −90, −60,
−30, and 0 °C. The residue was then extracted with n-hexane at room
temperature. Evaporation of the solvent from the extract under
1H{31P} NMR spectrum, 3JHH = 7.1 Hz, 4 H, PCH2), 1.20 (dd, 3JPH
=
3
3
15.9 Hz, JHH = 7.2 Hz, 12 H, PCHCH3), 0.92 (dd, JPH = 14.9 Hz,
3JHH = 7.2 Hz, 12 H, PCHCH3); the JHH coupling constants were
3
confirmed from 1H{31P} NMR spectra; 19F NMR (282.4 MHz, C6D6)
1
δ −97.2 (m, 2 F), −117.8 (m, 2 F); 31P{1H} (121.5 MHz, C6D6) δ
vacuum yielded a colorless powder. Yield: 784 mg (34%). H NMR
(300.1 MHz, C6D6) δ 3.36 (m, t in the 1H{31P} NMR spectrum, 3JHH
= 7.0 Hz, 4 H, CH2OCH3), 3.03 (s, 6 H, OCH3), 2.06 (m, sept in the
1H{31P} NMR spectrum, 3JHH = 7.0 Hz, 4 H, PCH), 1.70 (m, t in the
4
29.4 (t, JPF = 4.3 Hz). Anal. Calcd. for C23H42NClF4O2P2Pd: C,
42.87; H, 6.57; N, 2.17. Found: C, 43.17; H, 6.61; N, 2.01.
Formation of trans-[Pd(H)(4-C5NF4)(iPr2PCH2CH2OCH3)2] (7).
A solution of trans-[Pd(F)(4-C5NF4)(iPr2PCH2CH2OCH3)2] (2) (36
mg, 0.057 mmol) in C6D6 (0.6 mL) was treated with HBpin (10 μL,
0.068 mmol). After 3 h the formation of 7 was observed. The
generation of FBpin was observed by 19F NMR spectroscopy.37 The
yield of 7 was determined by using a capillary that contained
1H{31P} NMR spectrum, 3JHH = 7.0 Hz, 4 H, PCH2), 1.21 (dd, 3JPH
=
3
3
15.8 Hz, JHH = 7.1 Hz, 12 H, PCHCH3), 0.94 (dd, JPH = 14.8 Hz,
3JHH = 7.1 Hz, 12 H, PCHCH3); the JHH coupling constants were
3
confirmed from 1H{31P} NMR spectra; 19F NMR (282.4 MHz, C6D6)
δ −98.0 (m, 2 F), −118.8 (m, 2 F), −316.5 (s, br, 1 F); 31P{1H}
2
4
1
(121.5 MHz, C6D6) δ 30.1 (dt, JPF = 17.4 Hz, JPF = 4.5 Hz). Anal.
Calcd for C23H42NF5O2P2Pd: C, 43.99; H, 6.74; N, 2.23. Found: C,
44.45; H, 6.78; N, 2.06.
fluorobenzene as an external standard. Yield: 82%. H NMR (300.1
1
3
MHz, C6D6) δ 3.30 (m, t in the H{31P} NMR spectrum, JHH = 7.2
Hz, 4 H, CH2OCH3), 3.03 (s, 6 H, OCH3), 1.75 (m, sept in the
1H{31P} NMR spectrum, 3JHH = 7.2 Hz, 4 H, PCH2), 1.65 (br, t in the
Formation of trans-[Pd(F)(4-C5NF4)(PiPr3)2] (3). A solution of
[Pd(Me)2(tmeda)] (39 mg, 0.155 mmol) in THF-d8 (0.6 mL) was
treated with PiPr3 (63 μL, 0.326 mmol). After stirring the reaction
mixture for 1 h, pentafluoropyridine (18 μL, 0.186 mmol) was added.
The reaction mixture was stirred for another 4 d. The yield of 3 was
determined by using a capillary that contained fluorobenzene as an
external standard. Yield: 70%. Complex 3 was identified by its NMR
data.9
1H{31P} NMR spectrum, JHH = 7.0 Hz, 4 H, PCH), 0.98 (dd, JPH
=
3
3
3
2
16.3 Hz, JHH = 7.2 Hz, 12 H, PCHCH3), 0.89 (dd, JPH = 14.7 Hz,
3JHH = 6.8 Hz, 12 H, PCHCH3), −8.88 (t, JPH = 10.5 Hz, PdH); 19F
3
NMR (282.4 MHz, C6D6) δ −100.0 (m, 2 F), −117.0 (m, 2 F);
31P{1H} (121.5 MHz, C6D6) δ 43.4 (s).
Catalytic Formation of 2,3,5,6-Tetrafluoropyridine. (a) In an
NMR tube HBpin (95 μL, 0.60 mmol) was added to a solution of
trans-[Pd(F)(4-C5NF4)(iPr2PCH2CH2OCH3)2] (2) (19 mg, 0.030
mmol), pentafluoropyridine (66 μL, 0.60 mmol), and NEt3 (0.24 mL,
1.80 mmol) in THF-d8 (0.5 mL). The reaction mixture was heated for
48 h to 60 °C. The yield of 2,3,5,6-tetrafluoropyridine was determined
on using an external standard of fluorobenzene and is 80% (TON =
Preparation of trans-[Pd(OTf)(4-C5NF4)(iPr2PCH2CH2OCH3)2]
(4). A solution of trans-[Pd(F)(4-C5NF4)(iPr2PCH2CH2OCH3)2] (2)
(56 mg, 0.089 mmol) in n-hexane (3 mL) was treated with EtOTf (57
μL, 0.445 mmol). A colorless solid precipitated within 60 min. The
formation of EtF was observed by 19F NMR spectroscopy.34 After 4 h
the supernatant solution was removed. The precipitate was washed
1421
dx.doi.org/10.1021/om200998d | Organometallics 2012, 31, 1417−1424

Organometallics
Article
16). 2,3,5,6-Tetrafluoropyridine was identified by comparison of the
19F NMR data with an authentic sample.
Fluorine Chem. 2007, 128, 353. (h) Krahl, T.; Kemnitz, E. J. Fluorine
Chem. 2006, 127, 663. (i) Kemnitz, E.; Menz, D.-H. Prog. Solid State
Chem. 1998, 26, 97. (j) Ametamey, S. M.; Honer, M.; Schubiger, P. A.
Chem. Rev. 2008, 108, 1501.
(3) (a) Braun, T.; Wehmeier, F. Eur. J. Inorg. Chem. 2011, 2011, 613.
(b) Hughes, R. P. Eur. J. Inorg. Chem. 2009, 4591.
(b) In an NMR tube HBpin (70 μL, 0.44 mmol) was added to a
solution of trans-[Pd(F)(4-C5NF4)(PiPr3)2] (2) (13 mg, 0.022 mmol),
pentafluoropyridine (49 μL, 0.44 mmol), and NEt3 (0.18 mL, 1.32
mmol) in THF-d8 (0.5 mL). The reaction mixture was heated for 48 h
to 60 °C. The yield of 2,3,5,6-tetrafluoropyridine was determined on
using an external standard of fluorobenzene and is 60% (TON = 12).
Catalytic Formation of 4-Phenyl-2,3,5,6-tetrafluoropyridine
(8). In an NMR tube phenyl boronic acid (64 mg, 0.52 mmol) was
added to a solution of trans-[Pd(F)(4-C5NF4)(iPr2PCH2CH2OCH3)2]
(2) (16 mg, 0.026 mmol), pentafluoropyridine (58 μL, 0.52 mmol),
and NEt3 (0.21 mL, 1.56 mmol) in THF-d8 (0.5 mL). The reaction
mixture was heated for 3 d to 60 °C. The yield of 4-phenyl-2,3,5,6-
tetrafluoropyridine was determined on using an external standard of
fluorobenzene and is 59% (TON = 12). 19F NMR (282.4 MHz, THF-
d8) δ −92.9 (m, 2 F), −146.4 (m, 2 F).48
Catalytic Formation of 4-Tolyl-2,3,5,6-tetrafluoropyridine
(9). In an NMR tube tolylboronic acid (95 μL, 0.60 mmol) was added
to a solution of trans-[Pd(F)(4-C5NF4)(iPr2PCH2CH2OCH3)2] (2)
(19 mg, 0.030 mmol), pentafluoropyridine (66 μL, 0.60 mmol), and
NEt3 (0.24 mL, 1.80 mmol) in THF-d8 (0.5 mL). The reaction
mixture was heated for 3 d to 60 °C. The yield of 4-tolyl-2,3,5,6-
tetrafluoropyridine was determined on using an external standard of
fluorobenzene and is 48% (TON = 10). 19F NMR (282.4 MHz, THF-
d8) δ −93.1 (m, 2 F), −146.6 (m, 2 F).49
(4) (a) Clot, E.; Eisenstein, O.; Jasim, N.; Macgregor, S. A.;
McGrady, J. E.; Perutz, R. N. Acc. Chem. Res. 2011, 44, 333. (b) Amii,
H.; Uneyama, K. Chem. Rev. 2009, 109, 2119. (c) Braun, T.; Perutz, R.
N. Chem. Commun. 2002, 2749. (d) Burdeniuc, J.; Jedlicka, B.;
Crabtree, R. H. Chem. Ber 1997, 130, 145. (e) Jones, W. D. Dalton
Trans. 2003, 3991. (f) Kiplinger, J. L.; Richmond, T. G.; Osterberg, C.
E. Chem. Rev. 1994, 94, 373. (g) Mazurek, U.; Schwarz, H. Chem.
Commun. 2003, 1321. (h) Torrens, H. Coord. Chem. Rev. 2005, 249,
1957. (i) Braun, T; Perutz, R. N. Transition Metal-Mediated C−F
Bond Activation. In Comprehensive Organometallic Chemistry III;
Crabtree, R. H.; Mingos, D. M. P., Eds.; Elsevier: New York, 2007;
p 725. (j) Meier, G.; Braun, T. Angew. Chem., Int. Ed. 2009, 48, 1546;
Angew. Chem. 2009, 121, 1575. (k) Driver, T. G. Angew. Chem., Int. Ed.
2009, 48, 7974; Angew. Chem. 2009, 121, 8116. (l) Sun, A. D.; Love, J.
A. Dalton Trans. 2010, 39, 10362.
(5) Nova, A.; Reinhold, M.; Perutz, R. N.; Macgregor, S. A.;
McGrady, J. E. Organometallics 2010, 29, 1824.
(6) Andino, J. G.; Fan, H.; Fout, A. R.; Bailey, B. C.; Baik, M.-H.;
Mindiola, D. J. J. Organomet. Chem. 2011, 696, 4138−4146.
(7) Cargill, M. R.; Sandford, G.; Tadeusiak, A. J.; Yufit, D. S.;
Howard, J. A. K.; Kilickiran, P.; Nelles, G. J. Org. Chem. 2010, 75,
5860.
(8) (a) Teltewskoi, M.; Panetier, J. A.; Macgregor, S. A.; Braun, T.
Angew. Chem., Int. Ed. 2010, 49, 3947; Angew. Chem. 2010, 122, 4039.
(b) Lindup, R. J.; Marder, T. B.; Perutz, R. N.; Whitwood, A. C. Chem.
Commun. 2007, 3664.
Structure Determination for the Complexes 2 and 6.
Colorless crystals of 2 or 6 were obtained from n-hexane at 0 °C.
The diffraction data were collected on a STOE IPDS 2θ diffractometer
at −173 °C. Crystallographic data are depicted in the Supporting
Information. The structures were solved by direct methods and refined
with the full matrix least-squares method on F2 (SHELX-97).55
(9) Jasim, N. A.; Perutz, R. N.; Whitwood, A. C.; Braun, T.; Izundu,
J.; Neumann, B.; Rothfeld, S.; Stammler, H.-G. Organometallics 2004,
23, 6140.
(10) Braun, T.; Izundu, J.; Steffen, A.; Neumann, B.; Stammler, H.-G.
Dalton Trans. 2006, 5118.
ASSOCIATED CONTENT
* Supporting Information
Crystallographic data and computational details. This material
is available free of charge via the Internet at http://pubs.acs.org.
■
S
(11) Braun, T.; Parsons, S.; Perutz, R. N.; Voith, M. Organometallics
1999, 18, 1710.
AUTHOR INFORMATION
Corresponding Author
*E-mail: thomas.braun@chemie.hu-berlin.de.
■
(12) (a) Steffen, A.; Sladek, M. I.; Braun, T.; Neumann, B.;
Stammler, H.-G. Organometallics 2005, 24, 4057. (b) Braun, T.;
Perutz, R. N.; Sladek, M. I. Chem. Commun. 2001, 2254.
(13) Schaub, T.; Backes, M.; Radius, U. J. Am. Chem. Soc. 2006, 128,
15964.
(14) (a) Burling, S.; Elliott, P. I. P.; Jasim, N. A.; Lindup, R. J.;
McKenna, J.; Perutz, R. N.; Archibald, S. J.; Whitwood, A. C. Dalton
Trans. 2005, 3686. (b) Sladek, M. I.; Braun, T.; Neumann, B.;
ACKNOWLEDGMENTS
■
We acknowledge the research training group GRK “Fluorine as
a Key Element” funded by the Deutsche Forschungsgemein-
schaft for financial support. We thank Dr. B. Braun and Dr. S.
Mebs for help with the X-ray crystallography.
Stammler, H.-G. Dalton Trans 2002, 297. (c) Braun, T.; Blocker, B.;
̈
Schorlemer, V.; Neumann, B.; Stammler, A.; Stammler, H.-G. J. Chem.
Soc., Dalton Trans. 2002, 2213. (d) Braun, T.; Rothfeld, S.;
Schorlemer, V.; Stammler, A.; Stammler, H.-G. Inorg. Chem. Commun.
2003, 6, 752. (e) Braun, T.; Steffen, A.; Schorlemer, V.; Neumann, B.;
Stammler, H.-G. Dalton Trans. 2005, 3331.
REFERENCES
■
(1) (a) Banks, R. E., Ed. Fluorine Chemistry at the Millenium.
Fascinated by Fluorine; Elsevier: Amsterdam, 2000. (b) Beg
́
ue,
́
J.-P.;
(15) Schaub, T.; Fischer, P.; Steffen, A.; Braun, T.; Radius, U.; Mix,
A. J. Am. Chem. Soc. 2008, 130, 9304.
(16) (a) Aizenberg, M.; Milstein, D. J. Am. Chem. Soc. 1995, 117,
8674. (b) Aizenberg, M.; Milstein, D. Science 1994, 265, 359.
Bonnet-Delpon, D. Bioorganic and Medicinal Chemistry of Fluorine;
John Wiley & Sons: Hoboken, NJ, 2008. (c) Kirsch, P. Modern
Fluoroorganic Chemistry. Synthesis, Reactivity, Applications; Wiley-VCH
Verlag GmbH & Co. KGaA: Weinheim, 2004. (d) Gladysz, J. A.
Handbook of Fluorous Chemistry; Wiley-VCH: Weinheim, 2004.
(e) Hiyama, T. Organofluorine Compounds. Chemistry and Applications;
Springer: Berlin, 2000. (f) O’Hagan, D. J. Fluorine Chem. 2010, 131,
1071.
(17) (a) Braun, T.; Wehmeier, F.; Altenhoner, K. Angew. Chem., Int.
̈
Ed. 2007, 46, 5321; Angew. Chem. 2007, 119, 5415. (b) Braun, T.;
Ahijado-Salomon, M.; Altenhoner, K.; Teltewskoi, M.; Hinze, S.
̈
Angew. Chem., Int. Ed. 2009, 48, 1818; Angew. Chem. 2009, 121, 1850.
(c) Noveski, D; Braun, T.; Schulte, M; Neumann, B.; Stammler, H.-G.
Dalton Trans. 2003, 4075. (d) Braun, T.; Noveski, D.; Neumann, B.;
Stammler, H.-G. Angew. Chem. 2002, 114, 2870; Angew. Chem., Int. Ed.
2002, 41, 2745.
(2) (a) Muller, K.; Faeh, C.; Diederich, F. Science 2007, 317, 1881.
̈
(b) Purser, S.; Moore, P. R.; Swallow, S.; Gouverneur, V. Chem. Soc.
Rev. 2008, 37, 320. (c) Thayer, A. M. Chem. Eng. News 2006, 84, 15.
(d) Nicoletti, M.; Bremer, M.; Kirsch, P.; O’Hagan, D. Chem. Commun.
(18) (a) Hughes, R. P.; Laritchev, R. B.; Williamson, A.; Incarvito, C.
D.; Zakharov, L. N.; Rheingold, A. L. Organometallics 2003, 22, 2134.
(b) Edelbach, B. L.; Fazlur Rahman, A. K.; Lachicotte, R. J.; Jones, W.
D. Organometallics 1999, 18, 3170. (c) Maron, L.; Werkema, E. L.;
́
2007, 5075. (e) Ameduri, B.; Boutevin, B. Well-Architectured
Fluoropolymers. Synthesis, Properties and Applications; Elsevier:
Amsterdam, 2004. (f) Krafft, M. P.; Riess, J. G. J. Polym. Sci. A:
Polym. Chem. 2007, 45, 1185. (g) Rudiger, S.; Groß, U.; Kemnitz, E. J.
̈
1422
dx.doi.org/10.1021/om200998d | Organometallics 2012, 31, 1417−1424

Organometallics
Article
Perrin, L.; Eisenstein, O.; Andersen, R. A. J. Am. Chem. Soc. 2005, 127,
279. (d) Adonin, N. Y.; Starichenko, V. F. Mendeleev Commun. 2000,
10, 60. (e) Kraft, B. M.; Lachicotte, R. J.; Jones, W. D. Organometallics
2002, 21, 727. (f) Johnson, S. A.; Taylor, E. T.; Cruise, S. J.
Organometallics 2009, 28, 3842. (g) Prikhod’ko, S. A.; Adonin, N. Y.;
Babushkin, D. E.; Parmon, V. N. Mendeleev Commun. 2008, 18, 211.
1247. (e) Reade, S. P.; Acton, A. L.; Mahon, M. F.; Martin, T. A.;
Whittlesey, M. K. Eur. J. Inorg. Chem. 2009, 1774. (f) Vinogradov, A.
S.; Krasnov, V. I.; Platonov, V. E. Russ. J. Org. Chem. 2008, 44, 95.
(g) Jager-Fiedler, U.; Arndt, P.; Baumann, W.; Spannenberg, A.;
̈
Burlakov, V. V.; Rosenthal, U. Eur. J. Inorg. Chem. 2005, 2005, 2842.
(34) Hudlicky, M. J. Fluorine Chem. 1985, 29, 349.
́
(h) Beltran, T. F.; Feliz, M.; Llusar, R.; Mata, J. A.; Safont, V. S.
(35) Bhadury, P. S.; Pandey, M.; Jaiswal, D. K. J. Fluorine Chem.
1995, 73, 185.
Organometallics 2011, 30, 290. (i) Jana, A.; Roesky, H. W.; Schulzke,
C.; Samuel, P. P. Organometallics 2010, 29, 4837. (j) Reade, S. P.;
Mahon, M. F.; Whittlesey, M. K. J. Am. Chem. Soc. 2009, 131, 1847.
(k) Braun, T.; Noveski, D.; Ahijado, M.; Wehmeier, F. Dalton Trans.
(36) (a) Duttwyler, S.; Douvris, C.; Fackler, N. L. P.; Tham, F. S.;
Reed, C. A.; Baldridge, K. K.; Siegel, J. S. Angew. Chem., Int. Ed. 2010,
49, 7519; Angew. Chem. 2010, 122, 7681. (b) Rappoport, Z.; Apeloig,
Y. The Chemistry of Organic Silicon Compounds; John Wiley & Sons:
Chichester, 1998. (c) Walsh, R. Acc. Chem. Res. 1981, 14, 246.
(37) (a) Murata, J. J. Fluorine Chem. 2002, 113, 97. (b) Durig, J. R.;
Zhen, M.; Heusel, H. L.; Joseph, P. J.; Groner, P.; Little, T. S. J. Phys.
Chem. 1985, 89, 2877.
(38) (a) Lectard, S.; Hamashima, Y.; Sodeoka, M. Adv. Synth. Catal.
2010, 352, 2708. (b) Kalow, J. A.; Doyle, A. G. J. Am. Chem. Soc. 2011,
133, 16001. (c) Ahlsten, N.; Martín-Matute, B. Chem. Commun. 2011,
47, 8331. (d) Kalow, J. A.; Doyle, A. G. J. Am. Chem. Soc. 2010, 132,
3268. (e) Hintermann, L.; Togni, A. Angew. Chem., Int. Ed. 2000, 39,
4359; Angew. Chem. 2000, 122, 4530.
2007, 3820. (l) Jager-Fiedler, U.; Klahn, M.; Arndt, P.; Baumann, W.;
̈
Spannenberg, A.; Burlakov, V. V.; Rosenthal, U. J. Mol. Cat. A: Chem.
2007, 261, 184. (m) Klahn, M.; Fischer, C.; Spannenberg, A.;
Rosenthal, U.; Krossing, I. Tetrahedron Lett. 2007, 48, 8900. (n) Vela,
J.; Smith, J. M.; Yu, Y.; Ketterer, N. A.; Flaschenriem, C. J.; Lachicotte,
R. J.; Holland, P. L. J. Am. Chem. Soc. 2005, 127, 7857.
(19) Guard, L. M.; Ledger, A. E.; Reade, S. P.; Ellul, C. E.; Mahon, M.
F.; Whittlesey, M. K. J. Organomet. Chem. 2011, 696, 780.
(20) (a) Keyes, L.; Sun, A. D.; Love, J. A. Eur. J. Org. Chem. 2011,
3985. (b) Noveski, D.; Braun, T.; Neumann, B.; Stammler, A.;
́
Stammler, H.-G. Dalton Trans. 2004, 4106. (c) Hassan, J.; Sevignon,
M.; Gozzi, C.; Schulz, E.; Lemaire, M. Chem. Rev. 2002, 102, 1359.
(d) Edelbach, B. L.; Kraft, B. M.; Jones, W. D. J. Am. Chem. Soc. 1999,
121, 10327. (e) Guo, H.; Kong, F.; Kanno, K.-I.; He, J.; Nakajima, K.;
Takahashi, T. Organometallics 2006, 25, 2045. (f) Yoshikai, N.;
Mashima, H.; Nakamura, E. J. Am. Chem. Soc. 2005, 127, 17978.
(g) Yoshikai, N.; Matsuda, H.; Nakamura, E. J. Am. Chem. Soc. 2009,
131, 9590. (h) Ackermann, L.; Wechsler, C.; Kapdi, A.; Althammer, A.
Synlett 2010, 2010, 294. (i) Buckley, H. L.; Sun, A. D.; Love, J. A.
Organometallics 2009, 28, 6622. (j) Arisawa, M.; Suzuki, T.; Ishikawa,
T.; Yamaguchi, M. J. Am. Chem. Soc. 2008, 130, 12214. (k) Manabe,
K.; Ishikawa, S. Synthesis 2008, 2008, 2645. (l) Saeki, T.; Takashima,
Y.; Tamao, K. Synlett 2005, 1771. (m) Korn, T. J.; Schade, M. A.;
Wirth, S.; Knochel, P. Org. Lett. 2006, 8, 725. (n) Ishikawa, S.;
Manabe, K. Synthesis 2008, 2008, 3180.
(39) Hull, K. L.; Anani, W. Q.; Sanford, M. S. J. Am. Chem. Soc. 2006,
128, 7134.
(40) Hollingworth, C.; Hazari, A.; Hopkinson, M. N.; Tredwell, M.;
Benedetto, E.; Huiban, M.; Gee, A. D.; Brown, J. M.; Gouverneur, V.
Angew. Chem., Int. Ed. 2011, 50, 2613; Angew. Chem. 2011, 123, 2661.
(41) (a) Katcher, M. H.; Sha, A.; Doyle, A. G. J. Am. Chem. Soc. 2011,
133, 15902. (b) Katcher, M. H.; Doyle, A. G. J. Am. Chem. Soc. 2010,
132, 17402.
(42) (a) Barthazy, P.; Hintermann, L.; Stoop, R. M.; Worle, M.;
̈
Mezzetti, A.; Togni, A. Helv. Chim. Acta 1999, 82, 2448. (b) Veltheer,
J. E.; Burger, P.; Bergman, R. G. J. Am. Chem. Soc. 1995, 117, 12478.
(43) (a) Furuya, T.; Klein, J.; Ritter, T. Synthesis 2010, 2010, 1804.
(b) Brown, J. M.; Gouverneur, V. Angew. Chem., Int. Ed. 2009, 48,
8610; Angew. Chem. 2009, 121, 8762.
(21) Sun, A. D.; Love, J. A. Org. Lett. 2011, 13, 2750.
(44) Watson, D. A.; Su, M.; Teverovskiy, G.; Zhang, Y.; Garcia-
Fortanet, J.; Kinzel, T.; Buchwald, S. L. Science 2009, 325, 1661.
(45) (a) Furuya, T.; Benitez, D.; Tkatchouk, E.; Strom, A. E.; Tang,
P.; Goddard, W. A.; Ritter, T. J. Am. Chem. Soc. 2010, 132, 3793.
(b) Furuya, T.; Kaiser, H. M.; Ritter, T. Angew. Chem., Int. Ed. 2008,
47, 5993; Angew. Chem. 2008, 120, 6082. (c) Furuya, T.; Ritter, T. J.
Am. Chem. Soc. 2008, 130, 10060. (d) Ball, N. D.; Sanford, M. S. J. Am.
Chem. Soc. 2009, 131, 3796.
(46) Grushin, V. V.; Marshall, W. J. J. Am. Chem. Soc. 2004, 126,
3068.
(47) Macgregor, S. A.; Wondimagegn, T. Organometallics 2007, 26,
1143.
(48) Wei, Y.; Kan, J.; Wang, M.; Su, W.; Hong, M. Org. Lett. 2009,
(22) Kuhnel, M. F.; Lentz, D. Angew. Chem., Int. Ed. 2010, 49, 2933;
̈
Angew. Chem. 2010, 122, 2995.
(23) Huheey, J. E.; Keiter, E. A.; Keiter, R. L. Inorganic Chemistry.
Principles of Structure and Reactivity; HarperCollins College Publishers:
New York, 1993.
(24) Breyer, D.; Braun, T.; Penner, A. Dalton Trans. 2010, 39, 7513−
7520.
(25) (a) Kwong, F.; Chan, A. Synlett 2008, 1440. (b) Atkinson, R. C.
J.; Gibson, V. C.; Long, N. J.; White, A. J. P.; Williams, D. J.
Organometallics 2004, 23, 2744. (c) Old, D. W.; Wolfe, J. P.;
Buchwald, S. L. J. Am. Chem. Soc. 1998, 120, 9722.
(26) (a) Bei, X.; Crevier, T.; Guram, A. S.; Jandeleit, B.; Powers, T.
S.; Turner, H. W.; Uno, T.; Weinberg, W. H. Tetrahedron Lett. 1999,
40, 3855. (b) Bei, X.; Turner, H. W.; Weinberg, W. H.; Guram, A. S.;
Petersen, J. L. J. Org. Chem. 1999, 64, 6797.
(27) Weissman, H.; Shimon, L. J. W.; Milstein, D. Organometallics
2004, 23, 3931.
(28) Fraser, S. L.; Antipin, M. Y.; Khroustalyov, V. N.; Grushin, V. V.
J. Am. Chem. Soc. 1997, 119, 4769.
(29) Macgregor, S. A.; Roe, D. C.; Marshall, W. J.; Bloch, K. M.;
Bakhmutov, V. I.; Grushin, V. V. J. Am. Chem. Soc. 2005, 127, 15304.
(30) Erhardt, S.; Macgregor, S. A. J. Am. Chem. Soc. 2008, 130, 15490.
(31) Nova, A.; Erhardt, S.; Jasim, N. A.; Perutz, R. N.; Macgregor, S.
A.; McGrady, J. E.; Whitwood, A. C. J. Am. Chem. Soc. 2008, 130,
15499.
11, 3346.
(49) Lafrance, M.; Rowley, C. N.; Woo, T. K.; Fagnou, K. J. Am.
Chem. Soc. 2006, 128, 8754.
(50) Shimada, S.; Batsanov, A. S.; Howard, J. A. K.; Marder, T. B.
Angew. Chem., Int. Ed. 2001, 40, 2168; Angew. Chem. 2001, 113, 2226.
(51) (a) Li, H.; Liu, J.; Sun, C.-L.; Li, B.-J.; Shi, Z.-J. Org. Lett. 2011,
13, 276. (b) Wei, Y.; Su, W. J. Am. Chem. Soc. 2010, 132, 16377.
(c) Rene,
́
O.; Fagnou, K. Org. Lett. 2010, 12, 2116. (d) Do, H.-Q.;
Daugulis, O. J. Am. Chem. Soc. 2008, 130, 1128.
(52) (a) Noveski, D.; Braun, T.; Kruckemeier, S. J. Fluorine Chem.
̈
2003, 125, 959. (b) Mezzetti, A.; Becker, C. Helv. Chim. Acta 2002, 85,
2686. (c) Grushin, V. V. Chem.Eur. J. 2002, 8, 1006. (d) Grushin, V.
V. Acc. Chem. Res. 2010, 43, 160. (e) Murphy, E. F.; Murugavel, R.;
Roesky, H. W. Chem. Rev. 1997, 97, 3425. (f) Pagenkopf, B. L.;
Carreira, E. M. Chem.Eur. J. 1999, 5, 3437. (g) Doherty, N. M.;
Hoffman, N. W. Chem. Rev. 1991, 91, 553. (h) Steffen, A.; Braun, T.;
Stammler, H.-G. Angew. Chem., Int. Ed. 2007, 46, 8674; Angew. Chem.
(32) Reinhold, M.; McGrady, J. E.; Perutz, R. N. J. Am. Chem. Soc.
2004, 126, 5268.
(33) (a) Cronin, L.; Higgitt, C. L.; Karch, R.; Perutz, R. N.
Organometallics 1997, 16, 4920. (b) Hoyt, H. M.; Michael, F. E.;
Bergman, R. G. J. Am. Chem. Soc. 2004, 126, 1018. (c) Piglosiewicz, I.
M.; Kraft, S.; Beckhaus, R.; Haase, D.; Saak, W. Eur. J. Inorg. Chem.
2005, 938. (d) Ke Chan, P.; Kee Leong, W. Organometallics 2008, 27,
2007, 119, 8828. Klaring, P.; Jungton, A.-K.; Braun, T.; Muller, C. Eur.
̈
̈
J. Inorg. Chem. 2011, DOI: 10.1002/ejic.201100917.
1423
dx.doi.org/10.1021/om200998d | Organometallics 2012, 31, 1417−1424

Organometallics
Article
(53) De Graaf, W.; Boersma, J.; Smeets, W. J. J.; Spek, A. L.; Van
Koten, G. Organometallics 1989, 8, 2907.
(54) Werner, H.; Hampp, A.; Peters, K.; Peters, E. M.; Walz, L.; von
Schnering, H. G. Z. Naturforsch. 1990, 45b, 1548.
(55) Sheldrick, G. M. SHELX-97, Program for Crystal Structure
Refinement; University of Gottingen, 1997.
̈
1424
dx.doi.org/10.1021/om200998d | Organometallics 2012, 31, 1417−1424