C-F...M+ interaction in anionic α-fluorovinyl rhenium oxycarbene complexes and their β-fluoroenolate analogs

Article abstract of DOI:10.1016/j.jfluchem.2011.06.008

The C-F...M⁺ interaction in anionic σ-(α- fluorovinyl)rhenium oxycarbene complexes, [RCFCFReC(O)R′(CO)₄]M (1-6), M = Na, Li, K is studied by ¹⁹F NMR in THF and Et ₂O. The coordination of α-F to M⁺ results in an upfield shift of the corresponding ¹⁹F NMR signal and a decrease of ¹J_CF. The maximum shift is found for the Li salt of complex 4 in Et₂O (Δδ_Fα = 36.4 ppm), in which case a ⁷Li-¹⁹F spin-spin coupling is also observed (J_LiF = 40 Hz). The ΔE of C-F...M⁺ interaction and its effect on ¹⁹F shielding was further studied by DFT calculations using β-fluoroenolates as models, which confirmed a strong impact of CF-bond environment on the coordination ability of fluorine in these F,O-chelates. A compound with a β-fluoroenolate backbone but without rhenium, o-(α-fluorovinyl)phenolate 12, was prepared and studied by ¹⁹F NMR, and similarly showed indications of C-F...M⁺ interaction in THF solution. It is concluded that the donor ability of fluorine in the studied system is enhanced because of the conjugation of α-fluorovinyl group with the enolate π-system and back donation from the transition metal.

Full text of DOI:10.1016/j.jfluchem.2011.06.008

Journal of Fluorine Chemistry 132 (2011) 587–595
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
C–Fꢀ ꢀ ꢀM+ interaction in anionic
a-fluorovinyl rhenium oxycarbene complexes and
their
b
-fluoroenolate analogs
a
b
a,
Petr K. Sazonov a, , Yuri F. Oprunenko , Victor N. Khrustalev , Irina P. Beletskaya
*
*
a Chemistry Department of the M.V. Lomonosov Moscow State University, 119992 Moscow, Russia
b A.N. Nesmeyanov Institute of Organoelement Compounds (INEOS), Russian Academy of Sciences, Vavilov Street 28, 119991 Moscow, Russia
A R T I C L E I N F O
A B S T R A C T
The C–Fꢀ ꢀ ꢀM+ interaction in anionic
s-(a-fluorovinyl)rhenium oxycarbene complexes,
Article history:
[RCF55CFRe55C(O)R0(CO)4]M (1–6), M = Na, Li, K is studied by 19F NMR in THF and Et2O. The coordination
Received 11 April 2011
Received in revised form 6 June 2011
Accepted 8 June 2011
of
a
-F to M+ results in an upfield shift of the corresponding 19F NMR signal and a decrease of 1JCF. The
maximum shift is found for the Li salt of complex 4 in Et2O (DdF = 36.4 ppm), in which case a 7Li–19
F
a
Available online 15 June 2011
spin–spin coupling is also observed (JLiF = 40 Hz). The
D
E of C–Fꢀ ꢀ ꢀM+ interaction and its effect on 19F
shielding was further studied by DFT calculations using
b
-fluoroenolates as models, which confirmed a
Keywords:
strong impact of CF-bond environment on the coordination ability of fluorine in these F,O-chelates. A
C–F sigma donor
19F NMR
compound with a
b-fluoroenolate backbone but without rhenium, o-(a-fluorovinyl)phenolate 12, was
prepared and studied by 19F NMR, and similarly showed indications of C–Fꢀ ꢀ ꢀM+ interaction in THF
DFT calculations
solution. It is concluded that the donor ability of fluorine in the studied system is enhanced because of
a-Fluorovinyl enolates
the conjugation of
metal.
a
-fluorovinyl group with the enolate
p-system and back donation from the transition
Anionic acyl complexes
ß 2011 Elsevier B.V. All rights reserved.
1. Introduction
different chemical environments has not been evaluated or
discussed.
The ability of C–F units in organofluorine compounds to act as a
hard donor center for metal cations, although obvious, was
recognized only in the early 1980s, when Glusker and Murray-Rust
et al. pointed to a wide occurrence of short CFꢀ ꢀ ꢀMn+ contacts in
crystal structures [1]. Hundreds of close CFꢀ ꢀ ꢀMn+ contacts have
been reported in crystal state, for which the steric crowding and
crystal packing effects are largely responsible, however, there are
but a few cases, when such contacts persist in solution. Among the
notable exceptions are fluorine-containing cage compounds
developed by Plenio [2–8] and Takemura [9–13] groups and
zirconocenium cations with fluorophenylborate counteranions
[3,14–18]. The CFꢀ ꢀ ꢀMn+ coordination in cage compounds is
achieved through a high degree of donor center preorganization,
the encapsulated cation being unable to avoid the interaction with
fluorine, which resembles the situation in the crystal state. Apart
form these special cases, the CFꢀ ꢀ ꢀMn+ interaction in donor
solvents, competing with CF units, remains a sort of chemical
curiosity, and the requirements for such an interaction are not very
well understood. The effect of C–F bond inherent characteristics in
In the reaction of [Re(CO)5]Na with chlorotrifluoroethylene we
observed and isolated an anionic oxycarbene complex 1 [19],
whose 19F NMR spectrum in THF solution possessed some
unexpected dynamic features. In the spectrum of its Na+ salt the
resonance of vinylic
a-fluorine is broad and appears at an
unusually high field, but shifts ꢁ9 ppm downfield to the expected
region on the addition of 18-crown-6 to the sample. Such behavior
was suggestive of CFꢀ ꢀ ꢀNa+ interaction, which is being confirmed in
the present communication by studying the 19F NMR spectra of
various
a-fluorovinyl oxycarbene rhenium complexes with
different singly charged cations (Na, Li, K, Tl). To better understand
what makes the CFꢀ ꢀ ꢀM+ interaction feasible in these complexes,
additional model systems were studied computationally, and some
of them, such as b-fluoroenolates, were synthesized and studied in
solution by 19F NMR.
2. Results and discussion
Complex
1 results from the nucleophilic addition of
[(CO)5ReCF2CFCl]ꢂ carbanion to the CO ligand of CF255CFRe(CO)5.
The carbanion is in turn formed as an intermediate in the reaction
of [Re(CO)5]Na with CF255CFCl [19]. Nucleophilic attack at the
coordinated CO is quite typical for XRe(CO)5 complexes [20–24]
and various oxycarbene rhenium anions (2–6) can be generated
* Corresponding authors. Fax: +7 495 939 3618.
E-mail addresses: pksspk@yandex.ru, petr@elorg.chem.msu.ru (P.K. Sazonov),
beletska@org.chem.msu.ru (I.P. Beletskaya).
0022-1139/$ – see front matter ß 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2011.06.008

588
P.K. Sazonov et al. / Journal of Fluorine Chemistry 132 (2011) 587–595
Table 1
Cation effects on 19F chemical shifts in rhenium oxycarbene complexes in THF, 22 8C.
β
(CO)4
Re
F
(CO)4
Re
β
Nu
F
F
R
F
Nu M'
THF
Nu
18-crown-6
R
R
α
O
F
α
(OC)5Re
O
F
M'
1 - 6
M'·18-crown-6
.
a
Complex
R
NuM0
dF
DdF
DdF
b
a
a
c
Starting RRe(CO)5
Complex 1–6
Complex 1–6 +18-crown-6
b
1
F
F
F
F
ꢂ144.5
ꢂ144.5
ꢂ144.5
ꢂ144.5
ꢂ87.0
ꢂ156.9
ꢂ162.7
ꢂ153.7
ꢂ160.9
ꢂ99.0
ꢂ147.2
ꢂ146.1
ꢂ147.8
ꢂ147.2f
ꢂ91.5
9.7
16.6
5.9
ꢂ0.3
ꢂ1.9
ꢂ0.4
ꢂ1.2
ꢂ1.8
2.2
2
t-BuONa
t-BuOK
2
2
t-BuOLi
13.7
7.5
3
(CF3)3C
Ph
t-BuONa
t-BuONa
t-BuONa
t-BuOLi
4
ꢂ99.4
ꢂ111.7
ꢂ120.2
ꢂ132.1
ꢂ155.0
ꢂ103.3
ꢂ92.5
19.2
27.7
36.4
7.2
4d
4d
5
Ph
ꢂ99.0
ꢂ92.5e
ꢂ95.7e,f
ꢂ147.8
ꢂ98.3
ꢂ0.6
ꢂ6.4
ꢂ0.5
ꢂ0.9
Ph
ꢂ99.0
F
[PhCBB C]Na
[PhCBB C]Na
ꢂ144.5
ꢂ99.4
6
Ph
5.0
a
DdF
=
dF (complex + 18-crown-6) ꢂ dF (complex).
b
c
d
e
f
NuM0 = [(CO)5ReCF2CFCl]Na.
NMR data from Refs. [19,25,26].
In Et2O solvent.
In THF.
With [2.2.1]-cryptand.
from (
a
-fluorovinyl)Re(CO)5 complexes (Table 1). A coordinating
Much higher upfield shifts of a-fluorine signal than in more
solvent (THF or Et2O) is required for this nucleophilic addition
reaction, e.g. t-BuONa does not react with PhCF55CFRe(CO)5 in
toluene, but when 18-crown-6 is added, an instantaneous reaction
follows. The formation of anionic oxycarbene complexes is
confirmed by characteristic changes in IR and 1H, 19F and 13C
NMR spectra.
Crystals of apparently good quality were obtained for the
complex of Na salt of 1 with 18-crown-6 and dioxane which,
however, turned out to be mimetic twins unsuitable for X-ray
structure determination.
basic solvent, THF, are observed in Et2O, reaching 36.4 ppm for the
Li salt of complex 4. Moreover, in this case a spin–spin coupling of
a
-fluorine to lithium (J = 40 Hz) is observed, providing a direct
proof of lithium–fluorine interaction. The -fluorine signal appears
a
as a doublet (3JF–F) of 1:1:1:1 quartets, the quartet splitting
corresponding to spin–spin coupling with 7Li, I = 3/2 (Fig. 1). Both
the J(7Li, 19F) and the cation induced shift are the highest values
reported for the lithium–fluorine interaction [3,6,7]. The effect of Li
cation is weaker in THF and spin–spin coupling 7Li–19F is not
observed, possibly because of stronger solvation, which results in
the observed order of cation-induced shifts Na > Li > K.
The addition of 18-crown-6 to the solutions of the complexes in
THF causes a significant change in their ion pair state, as evidenced
by changes in the IR frequencies of Re-coordinated CO groups. All
n
(CO) bands are shifted to lower frequencies, which corresponds to
a decrease of CBB O bond order resulting from additional charge
transfer to the antibonding * orbitals. In Et2O solvent the (CO)
bands are shifted to higher frequencies compared to THF. The
lowest frequency (CO) band (B2 mode) is most sensitive to ion-
p
n
n
pairing, shifting (in case of complex 4) from 1944 cmꢂ1 (Li, Et2O)
and 1940 cmꢂ1 (Na, Et2O) to 1930 cmꢂ1 (Na, THF) and finally to
1908 cmꢂ1 (Na + 18-crown-6, THF). Thus, the ion pair separation in
the rhenium oxycarbene anions increases on going from Et2O to
THF and then to THF + 18-crown-6, though the contact of alkaline
metal cation with the acyl oxygen may remain even in the presence
of 18-crown-6.
Formation of oxycarbene anions (2–6) from neutral
fluorovinyl)Re(CO)5 compounds always results in an upfield shift
of
-fluorine resonance in 19F NMR spectrum. The addition of
crown ether or cryptand shifts the -fluorine signal downfield, so
(a-
a
a
that it returns to the values observed for the neutral Re(CO)5
complexes (ꢃ3 ppm). The shift of b-fluorine changes only slightly,
usually in the opposite direction (Table 1). The upfield shift of the 19
F
NMR resonance can be qualitatively explained in terms of increased
electron density around fluorine which in turn results from cation-
induced CF-bond polarization.
-131.0
-131.5
-132.0
-132.5
-133.0
PPM
Fig. 1. The multiplet of a
-fluorine in the 19F NMR spectrum of the Li salt of complex 4.

P.K. Sazonov et al. / Journal of Fluorine Chemistry 132 (2011) 587–595
589
(CO)4
Re
Ph
F
(CO)4
Re
(Me3Si)2NNa
PhC CH
THF
F
F
F
F
F
F
F
F
Y(OTf)3
(Me3Si)2NH
H
O
F
O
HN
F
(OC)5Re
(OC)5Re
Na
Ph
5
7
Scheme 1.
F
F
O
C
J = 5 Hz
F
-
F
F
Re(CO)4
F
Cl
O-
Re(CO)4
C
18-crown-6
THF, r.t.
C
F
F
Re
C
F
C
F
F
(CO)4
C
C
O
(CO)4Re
F
O
Cl
1
8
Scheme 2.
A significant decrease of carbon
a
-fluorine spin–spin coupling
fluorine (b) signal is shifted only slightly and to higher field upon
the addition of crown ether.
constant JCF is observed for sodium (1JCF = 282 Hz) and lithium
(1JCF = 276 Hz) salts of complex 4 in Et2O, compared to the Li-
cryptate salt of the same complex in THF (1JCF = 300 Hz) or the
1
Thus the electronic environment of C–F bond seems to play an
important role in determining its coordination ability. To gain a
further insight into the C–F interaction in such chelate systems we
performed a computational model study. The sign of the cation-
induced 19F chemical shift (DdF) was the first question considered.
For different ligands/cations both negative (high filed) [5–7] and
positive values [5,27] are reported in the literature, allowing one to
question the reliability of DdF as an indicator of CFꢀ ꢀ ꢀMn+
interaction.
neutral Re(CO)5 complex (1JCF = 291 Hz). Decrease of JCF is
1
considered as reliable criteria of CFꢀ ꢀ ꢀMn+ interaction, being
directly related to CF-bond order, which is lowered upon metal
coordination to fluorine [3,4,6,9,11,12].
The reaction of sodium salts of complexes 4, 5 and 6 with LaCl3
or Y(OTf)3 instead of the expected cation exchange resulted in the
protonolysis [13], regenerating the neutral (vinyl)Re(CO)5 com-
plex. In the reaction of complex
5
with Y(OTf)3 besides
Fluorovinylenolates were chosen as models of rhenium
oxycarbene complexes to simplify the calculation. In sodium
3,4,4-trifluoro-1,3-dien-1-olat, taken as a first model compound,
the CFꢀ ꢀ ꢀNa+ coordination is possible only in Z-isomer. Both at MP2
CF255CFRe(CO)5 a product of formal CF-activation–CO-insertion
(7) was isolated (Scheme 1). The amino-group in compound 7 can
result from the (Me3Si)2NH produced in the metallation reaction of
PhCBB CH with (Me3Si)2NNa.
The rhenium oxycarbene complexes, even in the form of
alkaline metal salts, are not very stable in solution. An interesting
transformation is observed for complex 1 in the presence of 18-
crown-6 in THF, which after several days at room temperature
rearranges into a red-colored complex, apparently of a metallo-
cyclic structure 8 (Scheme 2). The IR and 13C NMR spectra of 8
display the patterns of two different X2Re(CO)4 fragments, and its
19F NMR spectrum the same pattern of signals as that of 1 with
slightly different chemical shifts. The observation of a through-
X
X=Re, C
O
O
F
O
Na
Na
β−diketonate
β−fluoroenolate
b
Fig. 2. Analogy between
b
-diketonates and rhenium oxycarbene anions (b-
space spin–spin coupling between fluorine nuclei F belonging to
fluoroenolates).
CF255CF group and one of the fluorine nuclei of CF2-group is an
additional point in favor of a cyclic structure 8. Complex 8 results
from an intramolecular nucleophilic addition of the acyl oxygen to
the CO ligand of the Re(CO)5 group (Scheme 2).
F
The rhenium oxycarbene anions can be regarded as
b-
R
Re(CO)4Hal
diketonate analogs where one oxygen atom is replaced with
fluorine (Fig. 2). The persistence of CFꢀ ꢀ ꢀM+ interaction in donor
solvents (THF) can thus be attributed to chelate effect. The electron
density on fluorine is increased due to conjugation of the fluorine
lone pair with negatively charged enolate system, which enhances
its donor properties.
However, the oxycarbene rhenium complexes 9 and 10 [23],
though they have a similar conjugated F,O-chelate system, display
no signs of cation–fluorine interaction (Fig. 3). The corresponding
The effect of 18-crown-6:
F
O
β
Δ
Δ
δF ∼1 ppm
α
Na
δF ∼ −(3−5) ppm
β
9 R = F, Hal=Br
10 R= (CF3)3C, Hal=Cl
Fig. 3. Oxycarbene rhenium complexes without CFꢀ ꢀ ꢀNa+ interaction.

590
P.K. Sazonov et al. / Journal of Fluorine Chemistry 132 (2011) 587–595
F
H
F
H
H
F
O
α
Na
F
O
Na
Z-
A
F
H
α
E-
A
Method
δFα
δFβ
δFγ
δFα
δFβ
δFγ
MP2/6-311+G(d)
-155.5 -108.1 -121.0
-142.0 -106.3 -124.6
B3LYP/6-31+G(d) -150.0 -103.9 -113.0
-135.0 -98.5 -117.35
Fig. 4. Computed 19F NMR chemical shifts (
d
F) in Z- and E-isomers of sodium 3,4,4-trifluoro-1, 3-dien-1-olate.
and DFT theory levels, the sodium coordinated fluorine in the Z-
isomer is more shielded (by ꢁ15 ppm) than the non-coordinated
one in the E-isomer (Fig. 4).
H
H
The second model structure, 2,6-bis(a-fluorovinyl)phenolate
H
H
(Fig. 5), allows to compare 19F chemical shifts of otherwise
identical fluorovinyl groups one of which is coordinated to sodium.
In this model the interaction with sodium also shields the
corresponding 19F nuclei (DdF = 23.4 ppm).
δF=-106.5
F
O
F
δF=-83.1
Na
In fact the increased 19F shielding upon sodium cation
coordination is observed in all model systems examined (Table
2), and hence it can be considered a reliable experimental criteria
of CFꢀ ꢀ ꢀNa+ coordination.
B3LYP/6-31+G(d)
B
Fig. 5. Computed values of dF in 2,6-bis(a-fluorovinyl)phenolate.
The distance CFꢀ ꢀ ꢀNa+ is an important characteristic of CF-metal
interaction. As can be seen from the data in Table 2, the shortest
CFꢀ ꢀ ꢀNa+ distances are calculated for the interaction of internal
Table 2
Some properties of model F,O-chelates calculated by B3LYP/6-31+G(d) method.
H
H
H
H
F
H
H
H
H
H
H
H
F
H
H
H
F
O
F
O
F
O
F
O
C
D
Na
Na
F
F
E
Na
Na
CO
OC
OC
CO
H
Re
H
F
H
O
H
F
F
O
F
O
Na
G
Na
H
I
Na
.
a
+
+
c
C–Fꢀ ꢀ ꢀNa+ angle, 8
D
E(CFꢀ ꢀ ꢀNa+), kcal/molb
DdF
˚
˚
˚
Model
Chelate cycle
d(C–F) non-coord., A
d(CFꢀ ꢀ ꢀNa ), A
d(COꢀ ꢀ ꢀNa ), A
Z–A
C
Twisted
Flat
1.382
1.388
1.373
1.339
1.376
1.400
1.386
1.368
2.192
2.160
2.214
2.313
2.249
2.199
2.158
2.298
2.098
2.079
2.042
2.028
2.071
2.157
2.074
2.049
110.4
130.5
123.6
125.4
110.1
90.3
ꢂ9.9
ꢂ10.9
ꢂ6.4
15.0
21.8
28.5
23.0
21.5
16.3
20.0
16.5
D
Flat
E
Flat
ꢂ2.6
F
Twisted
Twisted
Flat
ꢂ5.7
Gd
H
I
ꢂ18.4
ꢂ10.8
ꢂ3.9
128.1
113.2
Twisted
a
In a structure with a linearly constrained C–Oꢀ ꢀ ꢀNa angle, which breaks the CFꢀ ꢀ ꢀNa+ contact.
b
D
E(CFꢀ ꢀ ꢀNa+) is calculated as a difference in energy between the fully optimized structure and the structure with a linearly constrained C–Oꢀ ꢀ ꢀNa angle.
F
F
c
Calculated similarly to
D
E,
=
(
F
) - (
F
).
F
Na
Na
O
O
d
SDD basis set with effective core potentials used for rhenium [28].

P.K. Sazonov et al. / Journal of Fluorine Chemistry 132 (2011) 587–595
591
a
-fluorine with cation in six-membered F,O-chelates (structures
b-fluoride elimination is a serious obstacle for the generation and
Z–A, C and H). The interaction with terminal -fluorine (D, E) or in
b
NMR study of
sodium salt of
b
-fluoroenolates [30]. An attempt to prepare the
a five-membered chelate cycle (F) is characterized by longer
CFꢀ ꢀ ꢀNa+ distances. There is also a tendency towards shorter
CFꢀ ꢀ ꢀNa+ distances in flat F,O-chelates (compare Z–A and C). The
planarity of the chelate cycle also governs the angle C–Fꢀ ꢀ ꢀNa+,
which is smaller for twisted F,O-chelates (90.3–113.28) than for flat
ones (123.6–130.58). The distances COꢀ ꢀ ꢀNa+ are expectedly
shorter than CFꢀ ꢀ ꢀNa+, the difference being small for Re-oxycar-
a-fluorovinyl enolate from the (E)-3,4-difluoro-1,4-
diphenylbut-3-en-1-one gave only the corresponding allene as the
only identifiable product. As a bypass solution we decided to use in
place of b-fluoroenolate an o-(a-fluorovinyl)phenolate, which has
the structural motif needed for the formation of 6-memberd F,O-
chelate, but is a stable compound.
The structure of the parent (E)-2-(1,2-difluoro-2-phenylvinyl)-
phenol (11) was established by the single-crystal X-ray diffraction
analysis of its 2:1 adduct with diaza-18-crown-6 (Fig. 6). The
molecule of 11 is non-planar. The phenolic and phenyl moieties are
twisted relative to the central difluoroethylenic fragment by 48.1
and 23.28, respectively, due to steric reasons (the intramolecular
repulsive interactions between the hydrogen and fluorine atoms –
H14ꢀ ꢀ ꢀF1 and H8ꢀ ꢀ ꢀF2). The larger value of the dihedral angle
observed in the case of the phenolic moiety is apparently explained
by the intermolecular O1–H1Oꢀ ꢀ ꢀN1 hydrogen bond with the
bene structure G and considerable for all its
b-fluoroenolate
analogs.
To compare the energetics of CFꢀ ꢀ ꢀNa+ interaction each of the
model structures was reoptimized with a C–Oꢀ ꢀ ꢀNa angle fixed to
1808, which breaks the CFꢀ ꢀ ꢀNa+ contact. As can be seen from the
data in Table 2, the highest energy gain upon CFꢀ ꢀ ꢀNa+ coordination
is calculated for internal a-fluorine (Z–A and C), exactly the type of
fluorine that is coordinated in the rhenium complexes 1–6.
Terminal -fluorine (D), especially in a CF2-group (E), is predicted
to be a much weaker donor center, as is the -fluorine in a 5-
b
˚
˚
a
diaza-18-crown-6 molecule (Oꢀ ꢀ ꢀN 2.711(3) A, Hꢀ ꢀ ꢀN 1.81 A, nO–
Hꢀ ꢀ ꢀN 1718, Fig. 6).
member chelate cycle (F). It should be pointed out that only these
latter less favorable fluorine coordination modes are available in
rhenium complexes 9 and 10, and it is not surprising that CFꢀ ꢀ ꢀNa
coordination is actually not observed.
The computed energy of CFꢀ ꢀ ꢀNa interaction correlates with the
length of the corresponding CF-bond in the non-coordinated state.
In other words, the longer and consequently weaker CF-bonds are
There is evidence of an intramolecular hydrogen bond to
fluorine in phenol 11. The 1H NMR signal of the phenolic hydrogen
shows a triplet splitting (JHF = 5 Hz) in CDCl3 solution, but the
splitting is removed and the signal shifted by 3 ppm to lower field
in THF, as a result of stronger hydrogen bonding to THF oxygen
[31].
better
Data Base [29] that the longest fluorine to sp2-carbon bonds
(0.138–0.140 nm) occur in -fluorovinyl transition metal com-
pounds. The -CF group in oxycarbene rhenium complexes is
therefore a better -donor than the corresponding group in
s
-donors. It was illuminating to find in Cambridge Crystal
The a
-fluorine 19F NMR signal of sodium (E)-2-(1,2-difluoro-2-
phenylvinyl)phenolate (12) is broad. Upon the addition of 18-
crown-6 the signal is narrowed and shifts downfield (Table 3, en.
1), a behavior characteristic of CFꢀ ꢀ ꢀNa+ interaction. As expected for
cation-induced shift the effect of crown ether is more pronounced
in toluene, a less polar solvent, (Table 3, en. 2). Other singly charged
a
a
s
fluorovinylenolates. This conclusion is confirmed by the calcula-
tion performed for a rhenium oxycarbene complex (G), for which
an unusually long C–F bond is predicted. The stabilization energy
associated with its interaction with sodium is significantly higher
than in all fluovinylenolate models. This effect of rhenium can be
interpreted in terms of high back-donating ability of 18-e
transition metal center.
cations also produce an upfield shift of a-fluorine signal, since the
addition of 18-crown-6 or cryptand shifts the signal downfield. The
effect is smaller than observed for Na, which can be explained
either by decreased charge density (K, Tl) or by stronger solvation
(Li). Unfortunately, despite considerable effort involving low
temperature measurements, no 203,205Tl–19F spin–spin coupling
constant [10,13] was observed in 19F NMR spectrum.
The success of using fluoroenolates for computational modeling
of CFꢀ ꢀ ꢀNa interaction suggests that such interactions in
b
-
Thus, the presence of rhenium is not obligatory for CFꢀ ꢀ ꢀM+
fluoroenolates could be observed experimentally. However, facile
interaction in a conjugated system such as
b-fluoroenolate,
Fig. 6. Molecular structure of adduct of 11 with diaza-18-crown-6 (40% ellipsoids). The dashed line indicates the intermolecular O–Hꢀ ꢀ ꢀN hydrogen bond.

592
P.K. Sazonov et al. / Journal of Fluorine Chemistry 132 (2011) 587–595
Table 3
Cation effects on 19F chemical shifts in (E)-2-(1,2-difluoro-2-phenylvinyl)phenolates.
δF=-152.3
δF=-153.8
δF=-156.0
β
β
F
F
F
18-crown-6
t-BuONa
Ph
Ph
F
δF=-137.9
Ph
α
α
THF
F
O
OH
F
O
δF=-141.0
δF=-131.1
Na
12
Na·18-crown-6
.
a
a
a
Entry
Solvent
Cation
Complexing agent
dF
a
DdF
DdF
b
Phenolate
Phenolate + 18-crown-6
1
2
3
4
5
THF
Na
Na
Li
18-crown-6
18-crown-6
[2.2.1]-cryptand
18-crown-6
–
ꢂ141.0
ꢂ143.6
ꢂ139.1b
ꢂ136.3
ꢂ134.9b
ꢂ131.1
ꢂ131.4b
ꢂ133.1
ꢂ131.6
9.9
12.2
6
ꢂ2.2
ꢂ2.8
ꢂ0.4
ꢂ1.9
Toluene
THF
THF
K
4.7
ꢁ4.5c
THF
Tl
a
DdF
Broad signal.
=
dF (anion + 18-crown-6) ꢂ dF (anion).
b
c
The dF of potassium phenolate + 18-crown-6 is taken as a reference.
though the effects observed in 19F NMR spectra of rhenium
oxycarbene complexes are more pronounced. But does the
conjugation (Fig. 2) really facilitate the CFꢀ ꢀ ꢀ M+ interaction in
these systems?
4. Experimental details
All NMR spectra were recorded on a Varian VXR-400 or a Bruker
Avance spectrometer at ambient temperature, 19F NMR at
376.3 MHz using C6F6
(
dF ꢂ162.9 ppm) as external or internal
To answer this question two additional model compounds
were studied computationally (Table 2), and the stabilization
energy of CFꢀ ꢀ ꢀNa+ interaction was compared for conjugated (H)
and non-conjugated (I) F,O-chelate. The structures were chosen
so as to minimize the difference in non-valent interactions in
conjugated and non-conjugated systems, while maintaining a
standard. 1H NMR (400.13 MHz) and 13C NMR (100.61 MHz) were
referenced to the signals of the solvent. IR spectra were recorded
using UR-20 or Thermo-Nicolet IR-200 FT-IR spectrophotometer in
a 0.02 cm CaF2 cell. Trifluorostyrene,
s-(a-fluorovinyl)Re(CO)5
complexes and the anionic rhenium oxycarbene complexes 1, 9
and 10 were available from the previous studies [19,25,26]. 1-(2-
Fluorophenyl)ethanol was obtained by the NaBH4 reduction of o-
fluoroacetophenone (Aldrich).
similar environment around the
a-fluorovinyl group, which in
both cases is attached to sp2-carbon. Interaction energy CFꢀ ꢀ ꢀNa+
for conjugated F,O-chelate (H) falls in the range previously
found for similar models Z–A and C (ꢁ10 kcal/mol), while for
the non-conjugated chelate (I) it is less than half of the above
value.
4.1. Formation of rhenium oxycarbene complexes 2–6
Reactions were carried out in a small (ꢁ5–10 ml) glass vessel
with two fused thin-walled NMR tubes (ꢁ3.5 mm diameter) under
vacuum or argon. The vessel was charged with RCF55CFRe(CO)5
(0.1 mmol), t-BuONa (0.12 mmol) or other appropriate base (Table
1). PhCBB CNa was generated from [(Me3Si)2N]Na and PhCBB CH. THF
or Et2O solvent (0.6–0.8 ml) was vacuum-transferred to the vessel.
After warming to r.t. and dissolving the reagents, a part (ꢁ0.3 ml)
of the reaction solution was decanted to the first NMR tube, which
was sealed off with flame. 18-Crown-6 (0.1 mmol, 26 mg) or
[2.2.1]-cryptand (0.06 mmol, 20 mg) was added to the rest of the
solution, which was transferred to second NMR tube. The sealed
tubes we placed inside standard 5 mm NMR tubes containing
acetone-d6 for the lock signal and C6F6 for 19F chemical shift
reference. Oxycarbene anionic complexes were formed almost
quantitatively according to IR, 1H and 19F NMR spectra, except for
the Li salt of complex 4 in Et2O, which was present in solution
together with the unreacted PhCF55CFRe(CO)5 in ꢁ1:1 ratio, even
despite using 3 equivalents of t-BuOLi.
Additionally, the role of conjugation in F,O-chelates was proved
experimentally, by measuring the 19F NMR spectrum of sodium 1-
(2-fluorophenyl)ethoxide. No change of d
F or of 1JCF was observed
upon the addition of 18-crown-6, demonstrating that in a non-
conjugated ligand the fluorine does not interact with Na+ in THF
solution.
In flat F,O-chelates, such as models C, D and H (Table 2),
the conjugation can be regarded as an antibonding interaction
between fluorine lone pair and the
p-system of the enolate.
However, if the chelate cycle is twisted (as in A, B and G) the
negative hyperconjugation of fluorine can also be important.
3. Conclusions
A strong CFꢀ ꢀ ꢀM+ interaction, which is not broken in THF donor
solvent, is found in rhenium
s-fluorovinyl oxycarbene complexes
as well as in the analogous o-(a-fluorovinyl)phenolate. The
s
-[3-(Pentacarbonylrhenio)-2,3,3-trifluoro-2-chloropropanoyl]-
present study reveals the factors, which make it feasible, and
hence are important for CFꢀ ꢀ ꢀM+ interaction in general. The
negative charge of the ligand (i) and the chelate effect (ii), though
s
-(trifluorovinyl)tetracarbonylrhenate (1) sodium salt, [CF255CFRe
(CO)4C(O)CFClCF2Re(CO)5]Na. 19F NMR (THF):
d
ꢂ55.6 (d, br., 1F,
2JFF = 295 Hz); ꢂ63.7 (d, br., 1F, JFF = 295 Hz); ꢂ91 (m, br., 1F);
2
important, are not sufficient conditions. The conjugation of the
a-
2
3
ꢂ95.7 (dd, 1F, JFF = 98 Hz, JFF = 30 Hz); ꢂ126.4 (dd, 1F,
fluorovinyl group with the enolate -system (iii) and its direct
p
2JFF = 98 Hz, JFF = 108 Hz); ꢂ156.9 (dd, br., 1F, JFF = 30 Hz,
3
3
connection to transition metal (iv) are the two additional factors,
which weaken the CF-bond and increase the donor ability of
fluorine.
3JFF = 108 Hz). 19F NMR (THF + 18-crown-6):
d
ꢂ57.3 (d, br., 1F,
2
2JFF = 290 Hz); ꢂ62.0 (m, br., 1F); ꢂ97.1 (dd, 1F, JFF = 98 Hz,

P.K. Sazonov et al. / Journal of Fluorine Chemistry 132 (2011) 587–595
593
2
3JFF = 30 Hz); ꢂ113 (m, br., 1F); ꢂ126.7 (dd, 1F, JFF = 99 Hz,
2JFF = 97 Hz, 3JFF = 109 Hz); ꢂ155.0 (dd, 1F, 3JFF = 30 Hz,
3JFF = 111 Hz); ꢂ147.2 (dd, 1F, 3JFF = 30 Hz, 3JFF = 111 Hz). 13C NMR
3JFF = 109 Hz). IR (THF):
n 1692 (m) C55C; 1928 (s), 1972 (vs),
(THF + 18-crown-6):
d
252.2 (dm, 1C, Jd ꢁ45 Hz); 193.9 (t, 1C, JCF
2081 (m) CBB O; 2160 (w) CBB C. 19F NMR (THF + 18-crown-6):
d
2
3
ꢁ6 Hz); 192.4 (t, 1C, JCF ꢁ3 Hz); 191.7 (d, 1C, JCF ꢁ8 Hz); 191.1 (m,
1C); 183.2 (t, 5C, JCF ꢁ6 Hz); the weaker signals of fluorinated
ꢂ96.4 (dd, 1F, JFF = 98 Hz, JFF = 30 Hz); ꢂ126.9 (dd, 1F,
2JFF = 98 Hz, 3JFF = 110 Hz); ꢂ147.8 (dd, 1F, 3JFF = 30 Hz,
3JFF = 110 Hz).
backbone were not observed. IR (THF + 18-crown-6):
n 1605 (m,
br.) C55O; 1695 (m) C55C; 1920 (vs), 1963 (sh), 1977 (vs), 2028 (vs),
2080 (s), 2142 (m) CBB O.
s
-(3-Phenylpropyn-2-oyl)-
s-(1,2-difluoro-2-phenylethenyl)te-
tracarbonylrhenate sodium salt (6), [PhCBB C(CO)Re(CO)4CF55CFPh]Na.
3
s
-(Tert-butoxycarbonyl)-
s
-(trifluorovinyl)tetracarbonylrhenate
19F NMR (THF):
3JFF = 112 Hz). IR (THF):
d
ꢂ102.9 (d, 1F, JFF = 112 Hz); ꢂ145.0 (d, 1F,
(2) [t-BuO(CO)Re(CO)4CF55CF2]M. Sodium salt, M = Na. 19F NMR
n
1594 (m, br.) C55O; 1925 (vs), 1968 (sh),
2
3
(THF):
d
ꢂ94.6 (dd, 1F, JFF = 97 Hz, JFF = 30 Hz); ꢂ126.0 (dd, 1F,
1973 (vs), 2078 (s) CBB O; 2160 (w, br.) CBB C. 19F NMR (THF + 18-
2JFF = 97 Hz, 3JFF = 106 Hz); ꢂ162.7 (dd, 1F, 3JFF = 29 Hz,
crown-6):
3JFF = 112 Hz).
d
ꢂ97.9 (d, 1F, JFF = 112 Hz); ꢂ145.9 (d, 1F,
3
3JFF = 106 Hz). IR (THF):
n
1600 (m, br.) C55O; 1690 (m) C55C;
1931 (vs), 1965 (sh), 1975 (vs), 2082 (m) CBB O. 19F NMR (THF + 18-
2
3
crown-6):
d
ꢂ95.5 (dd, 1F, JFF = 99 Hz, JFF = 29 Hz); ꢂ125.7 (dd,
4.2. Isolation of m-(5-phenyl-5-amino-3-oxopentadien-1,4-yl-
2
3
3
1F, JFF = 99 Hz, JFF = 110 Hz); ꢂ146.1 (dd, 1F, JFF = 29 Hz,
1k kO)teracarbonylrhenium (7),
C1:1
3JFF = 110 Hz). Potassium salt, M = K. 19F NMR (THF):
d
ꢂ96.1 (dd,
2
3
2
Ph(NH2)C=CHC(O)CF=CFRe(CO)4
1F, JFF = 99 Hz, JFF = 29 Hz); ꢂ126.5 (dd, 1F, JFF = 99 Hz,
3JFF = 108 Hz); ꢂ153.7 (dd, 1F, JFF = 29 Hz, JFF = 108 Hz). IR
3
3
A solution of CF255CFRe(CO)5 (100 mg, 0.245 mmol) in 0.5 ml
THF was added to a suspension of PhCBB CNa in 1 ml THF, prepared
in a Schlenk flask from [(Me3Si)2N]Na (46 mg, 0.25 mmol) and
PhCBB CH (27 mg, 0.26 mmol). Samples of the reaction solution
were taken for the NMR and IR analysis and to the rest of it solid
Y(OTf)3 (64 mg, 0.122 mmol) was added under stirring in two
portions, a sample for IR and NMR being taken in between and after
the addition of the second portion. IR spectrum indicated the
presence of CF255CFRe(CO)5 band (2147 cmꢂ1), and two new bands
(2107 and 2099 cmꢂ1), the latter subsequently identified as
belonging to 7. Reaction mixture was diluted with CH2Cl2 (3 ml)
and filtered through an alumina pad. Part of the reaction mixture
was separated on a Silufol UV-254 TLC plate, using a CH2Cl2–
petroleum ether, 1:5 as an eluent. The second yellow band
(Rf = 0.3) after solvent removal afforded 4 mg of complex 7 as a
yellow solid. 1H NMR (acetone-d6):
1H, NH); 7.78 (d, 2h); 7.62 (t, 1H); 7.55 (t, 2H); 5.63 (t, 1H,
JHF = 2.7 Hz); 1.48 (s, 9H). 19F NMR (Et2O):
ꢂ70.4 (m, 1F); ꢂ141.6
(m, 1F). IR (THF): 1544 (s) C55O; 1941 (vs), 1985 (sh), 1996 (vs),
2099 (s) CBB O. EIMS (direct inlet) 70 eV, m/z (rel. int.): 507 [M]+
(10), 479 [MꢂCO]+ (10), 451 [Mꢂ2CO]+ (20), 423 [Mꢂ3CO]+ (10),
395 [Mꢂ4CO]+ (30), 103 [PhC2H2]+ (100).
(THF):
n 1600 (m, br.) C55O; 1690 (m) C55C; 1925 (vs), 1965
(sh), 1975 (vs), 2080 (m) CBB O. 19F NMR (THF + 18-crown-6):
d
2
3
ꢂ96.5 (dd, 1F, JFF = 99 Hz, JFF = 29 Hz); ꢂ126.9 (dd, 1F,
2JFF = 99 Hz, 3JFF = 110 Hz); ꢂ147.8 (dd, 1F, 3JFF = 29 Hz,
3JFF = 110 Hz). Lithium salt, M = Li. 19F NMR (THF):
d
ꢂ94.4 (dd,
2
2
3
1F, JFF = 96 Hz, JFF = 28 Hz); ꢂ125.6 (dd, 1F, JFF = 96 Hz,
3JFF = 105 Hz); ꢂ160.9 (br, 1F). 19F NMR (THF + 2.2.1-cryptand):
2
3
d
ꢂ95.7 (dd, 1F, JFF = 98 Hz, JFF = 30 Hz); ꢂ126.4 (dd, 1F,
2JFF = 98 Hz, 3JFF = 111 Hz); ꢂ147.2 (dd, 1F, 3JFF = 30 Hz,
3JFF = 111 Hz).
s
-(Tert-butoxycarbonyl)-
fluoromethyl)pentenyl)-tetracarbonylrhenate sodium salt (3), [t-
BuO(CO)Re(CO)4CF55CFC(CF3)3]Na. 19F NMR (THF):
ꢂ62.7 (dd,
9F, JFF = 18 Hz, JFF = 14 Hz); ꢂ99.0 (br., 1F); ꢂ147.7 (d, br., 1F,
s-(1,2,4,4,4-pentafluoro-3,3-bis(tri-
d
3JFF = 130 Hz). 19F NMR (THF + 18-crown-6):
d
ꢂ62.7 (dd, 9F,
d 9.67 (s, br, 1H, NH); 8.26 (s, br,
JFF = 18 Hz, JFF = 13 Hz); ꢂ91.5 (dm, 1F, 3JFF = 127 Hz, 6JFF = 18 Hz);
3
5
ꢂ149.5 (dm, 1F, JFF = 127 Hz, JFF = 13 Hz).
d
s-(Tert-butoxycarbonyl)-s-(1,2-difluoro-2-phenylethenyl)-tetra-
n
carbonylrhenate (4), [t-BuO(CO)Re(CO)4CF55CFPh]M. Sodium salt,
M = Na. 19F NMR (THF):
d
ꢂ111.7 (d, 1F, 3JFF = 109 Hz); ꢂ143.9 (d,
1F, 3JFF = 109 Hz). IR (THF):
n
1590 (m, br.) C55O; 1930 (s), 1958 (s),
1977 (vs), 2081 (m) CBB O. 19F NMR (THF + 18-crown-6):
d
ꢂ92.5 (d,
1F, JFF = 112 Hz); ꢂ141.7 (d, 1F, JFF = 112 Hz). IR (THF + 18-
crown-6): 1615 (m, br.) C55O; 1908 (s), 1951 (s), 1971 (vs), 2077
(m) CBB O. 1H NMR (Et2O):
1.46 (s, 9H). 19F NMR (Et2O):
(d, 1F, 3JFF = 110 Hz). IR (Et2O):
3
3
4.3. Spectral data for complexes 8–10
n
d
7.61 (d, 2h); 7.33 (t, 2H); 7.18 (t, 1H);
d
m
-(1,1,2-Trifluoro-2-chloro-4-oxa-5-oxopentyliden-2
k
C3-diyl-
ꢂ120.2 (d, 1F, 3JFF = 110 Hz); ꢂ141.1
1k
C1:1 C5)trifluorovinyl-2 C-octacarbonyl-1k4C,2k4C-dirhenate
k
k
n
1575 (m, br.) C55O; 1940 (vs), 1968
(s), 1984 (vs), 2081 (m) CBB O. 13C NMR (Et2O):
(d, 1C, JCF = 8 Hz); 191.6 (t, 2C, JCF = 7 Hz); 190.8 (d, 1C, JCF = 5 Hz);
d 207.5 (s, 1C); 192.0
(-1) sodium (8),
.
19F
[CF2=CF(CO)4Re=C(O)CFClCF2Re(CO)(CO)4]Na
1
2
1
180.6 (dd, JCF = 282 Hz, JCF = 106 Hz); 160.9 (dd, JCF = 204 Hz,
2JCF = 42 Hz); 133.1 (d, 2JCF = 30 Hz); 128.6 (s); 126.8 (s); 125.4 (dd,
JCF = 10 Hz, JCF = 7 Hz); 77.4 (s); 29.6 (s). Lithium salt, M = Li. 1H
2
NMR (THF-d8 + 18-crown-6):
d
ꢂ68.4 (dt, 1F, JFF = 281 Hz,
2
3
Jt = 5 Hz); ꢂ85.1 (dd, 1F, JFF = 281 Hz, JFF = 6 Hz); ꢂ94.9 (dd, 1F,
2JFF = 96 Hz, 3JFF = 31 Hz); ꢂ124.6 (t, 1F, Jt = 6 Hz); ꢂ125.5 (ddd, 1F,
2JFF = 96 Hz, 3JFF = 111 Hz, 8JFF = 5 Hz); ꢂ146.6 (dd, 1F, 3JFF = 31 Hz,
NMR (Et2O): d F
7.57 (d, 2h); 7.33 (t, 2H); 7.19 (t, 1H); 1.48 (s, 9H). 19
NMR (Et2O):
d
ꢂ132.1 (m, 1F, 3JFF = 106 Hz, JLiF = 40 Hz); ꢂ138.5 (d,
3JFF = 111 Hz). 13C NMR (THF-d8 + 18-crown-6):
d 290.2 (dm,
3
1F, JFF = 106 Hz). 13C NMR (Et2O):
d 210.9 (s, 1C); 192.2 (d, 1C,
Jd = 50 Hz); 199.2 (br, 1C); 192.8 (d, 1C); 192.0 (m, 1C); 191.6
(m, 1C); 191.3 (m, 1C); 190.9 (t, 1C, JCF = 3.5 Hz); 188.9 (m, 1C,
JCF = 10 Hz); 188.3 (m, 1C); 188.0 (d, 1C, JCF = 21 Hz); the weaker
signals of fluorinated backbone were not observed. IR (THF + 18-
JCF = 8 Hz); 191.8 (t, 2C, JCF = 6 Hz); 190.9 (d, 1C, JCF = 8 Hz); 180.5
(dd, 1JCF = 276 Hz, 2JCF = 105 Hz); 162.9 (dd, 1JCF = 207 Hz,
2
2JCF = 45 Hz); 133.9 (d, JCF = 30 Hz); 129.2 (s); 128.0 (s); 127.0
(t, JCF = 7 Hz); 79.2 (s); 30.4 (s). IR (Et2O): n 1560 (m, br.) C55O; 1944
(s), 1967 (s), 1986 (vs), 2082 (s) CBB O. 1H NMR (THF + 2.2.1-
crown-6):
n 1697 (m) C55C; 1933 (vs), 1943 (sh), 1988 (vs), 1998
cryptand):
NMR (THF + 2.2.1-cryptand):
d
7.58 (d, 2h); 7.20 (t, 2H); 7.00 (t, 1H); 1.35 (s, 9H). 19
F
(vs), 2088 (s), 2100 (m) CBB O.
3
d
ꢂ95.7 (d, 1F, JFF = 112 Hz,
Bromo-s-(3,3,2-trifluoropropen-2-oyl)tetracarbonylrhenate sodi-
1JCF = 300 Hz); ꢂ144.9 (d, 1F, JFF = 112 Hz); JCF measured in 13C
um salt (9), [CF255CF(CO)Re(CO)4Br]Na. 19F NMR (THF + 18-crown-
3
1
2
satellite.
6):
d
ꢂ105.5 (t, 1F, JFF = 35 Hz); ꢂ111.1 (dd, 1F, JFF = 36 Hz,
3
3
s
-(3-Phenylpropyn-2-oyl)-
s
-(trifluorovinyl)tetracarbonylrhenate
3JFF = 110 Hz); ꢂ160.4 (dd, 1F, JFF = 34 Hz, JFF = 110 Hz).
sodium salt (5), [PhCBB C(CO)Re(CO)4CF55CF2]Na. 19F NMR (THF):
d
Chloro-s-[2,3,5,5,5-pentafluoro-4,4-bis(trifluoromethyl)penten-
2
3
ꢂ95.4 (dd, 1F, JFF = 97 Hz, JFF = 30 Hz); ꢂ126.4 (dd, 1F,
2-oyl]tetracarbonylrhenate sodium salt (10), [(CF3)3CCF55CF(CO)R-

594
P.K. Sazonov et al. / Journal of Fluorine Chemistry 132 (2011) 587–595
CF(CO)Re(CO)4Cl]Na. 19F NMR (THF + 2.2.2-cryptand):
d
ꢂ61.9 (dd,
CH); 30.1 (s, CH3). 1H NMR (THF + 18-crown-6):
d 7.90 (m, 1h); 6.96
3
9F, JFF = 17 Hz, JFF = 13 Hz); ꢂ128.2 (dm, 1F, JFF = 133 Hz,
(m, 2H); 6.76 (m, 1H); 5.30 (q, 1H); 1.29 (d, 3H). 19F NMR
3
5
6JFF = 17 Hz); ꢂ169.9 (dm, 1F, JFF = 133 Hz, JFF = 12 Hz). Spectral
data for complexes 9 and 10 without 18-crown-6 or cryptand is
given in Ref. [23].
(THF + 18-crown-6):
d
ꢂ120.3 (m). 13C NMR (THF + 18-crown-6):
d
160.6 (d, 1JCF = 241 Hz); 143.0 (d, JCF = 16 Hz); 129.7 (s, CH); 126.3
(d, JCF = 8 Hz, CH); 124.1 (s, CH); 114.1 (d, JCF = 23 Hz, CH); 64.6 (s,
CH); 29.6 (s, CH3).
4.4. Synthesis of (E)-2-(1,2-difluoro-2-phenylvinyl)phenol (11), (o-
OHC6H4)CF55CFPh, and of the corresponding phenolates
4.6. X-ray crystal structure determination of 2(11)ꢀ(diaza-18-crown-
6)
A solution of BuLi (5 mmol) in 2 ml of petroleum ether was
added dropwise to a stirred solution of o-BrC6H4OH (430 mg,
2.5 mmol) in THF (5 ml) at ꢂ60 8C under argon atmosphere. The
reaction mixture was allowed to warm to r.t. and stirred for 3 hr.
PhCF55CF2 (440 mg, 2.78 mmol) was added dropwise to the
resulting clear solution and the reaction mixture was left stirring
overnight. After aqueous HCl workup, extraction with CH2Cl2
(2 ꢄ 5 ml) and solvent removal the residue was separated by
column chromatography on silica gel (Merk, 35–70 mkm). The first
fraction gave after solvent removal (o-OHC6H4)CF55CFPh product
The crystal of 2(11)ꢀ(diaza-18-crown-6) (C40H46F4N2O6,
M = 726.79) is triclinic, space group Pꢂ1, at T = 173 K:
˚
˚
˚
a
a = 7.7054(15) A, b = 9.3670(19) A, c = 13.286(3) A,
= 99.41(3)8,
3
˚
b
= 90.25(3)8,
cm3, F(0 0 0) = 384,
unique reflections, Rint = 0.032) were measured on an automated
four-circle diffractometer Syntex P21 ( (MoK )-radiation, graphite
monochromator, /2 scan mode, 2 max = 528). The structure was
g
= 98.77(3)8, V = 934.6(4) A , Z = 1, dcalc = 1.291 g/
m
= 0.099 mmꢂ1. 3930 total reflections (3641
l
a
v
u
u
determined by direct methods and refined by full-matrix least
squares technique on F2 with anisotropic displacement parameters
for non-hydrogen atoms. The hydrogen atoms of the hydroxy and
amino groups were localized in the difference-Fourier map and
included in the refinement with fixed positional and thermal
parameters. The other hydrogen atoms were placed in calculated
positions and refined within riding model with fixed isotropic
displacement parameters [Uiso(H) = 1.2Ueq(C)]. The final diver-
gence factors were R1 = 0.059 for 2132 independent reflections
(200 mg, 0.86 mmol) as a colorless solid. 1H NMR (CDCl3):
2h); 7.35–7.53 (m, 5H); 7.05 (m, 2H); 5.60 (t, 1H, JHF = 5 Hz, OH). 1H
d 7.80 (d,
NMR (THF):
d 8.66 (s, 1H, OH); 7.73 (d, 2h); 7.42 (t, 2H); 7.35 (m,
2H); 7.25 (t, 1H); 6.87 (m, 2H). 19F NMR (THF):
d
ꢂ137.9 (d, 1F,
3JFF = 131 Hz); ꢂ152.3 (d, 1F, JFF = 131 Hz). 13C NMR (CDCl3):
d
3
1
2
153.6 (s); 148.2 (dd, JCF = 231 Hz, JCF = 48 Hz); 146.9 (dd,
1JCF = 240 Hz, JCF = 56 Hz); 131.9 (t, JCF = 1.5 Hz, CH); 129.7 (t,
2
JCF = 4 Hz, CH); 129.5 (d, JCF = 2 Hz, CH); 129.4 (dd, JCF = 25 Hz,
JCF = 6.5 Hz); 128.7 (d, JCF = 2 Hz, CH); 125.9 (dd, JCF = 9 Hz,
JCF = 8 Hz, CH); 120.8 (s, CH); 117.3 (s, CH); 116.6 (dd, JCF = 22 Hz,
JCF = 4 Hz). Crystals of the complex of phenol 11 with diaza-18-
crown-6 suitable for X-ray diffraction were obtained by mixing the
ꢁ0.1 M solutions of diaza-18-crown-6 and 11 in dichloromethane.
The corresponding phenolates were generated from phenol 11 by
the action of t-BuOM (M = Li, Na, K) in THF, NaH in toluene and
TlOH in THF.
with I > 2s(I) and wR2 = 0.126 for all independent reflections,
S = 1.000. All calculations were carried out using the SHELXTL
program. [32] Crystallographic data for 2(11)ꢀ(diaza-18-crown-6)
have been deposited with the Cambridge Crystallographic Data
Center as supplementary publication no. CCDC 827829. Copies of
the data can be obtained, free of charge, on application to CCDC, 12
Union Road, Cambridge CB2 1EZ, UK (fax: +44 1223 336033 or e
mail: deposit@ccdc.cam.ac.uk or www.ccdc.cam.ac.uk.
(E)-2-(1,2-difluoro-2-phenylvinyl)phenolate,
(12)
(o-
OMC6H4)CF55CFPh. Sodium salt, M = Na. 19F NMR (THF):
d
ꢂ141.0
4.7. Computational details
3
3
(d, br., 1F, JFF = 129 Hz); ꢂ153.8 (d, 1F, JFF = 129 Hz). 19F NMR
(THF + 18-crown-6):
d
ꢂ131.1 (d, 1F, 3JFF = 132 Hz); ꢂ156.0 (d, 1F,
Geometries were optimized with the methods indicated in the
corresponding figures and Table 2. Chemical shifts were calculated
by GIAO method [33,34] for the structures optimized at the same
theory level. All calculations were performed with Gaussian 03
program [35].
3JFF = 132 Hz). 1H NMR (THF + 18-crown-6):
d 7.69 (d, 2h); 7.35 (t,
2H); 7.22 (t, 1H); 7.00 (d, 1H); 6.86 (t, 1H); 6.58 (d, 1H); 6.06 (t, 1H).
19F NMR (toluene):
d
ꢂ143.6 (br., 1F); ꢂ153.2 (br., 1F). 19F NMR
(toluene + 18-crown-6):
d
ꢂ131.4 (br., 1F); ꢂ156.1 (d, 1F,
3JFF = 129 Hz). Lithium salt, M = Li. 1H NMR (THF):
7.30 (t, 2H); 7.23 (t, 1H); 7.14 (d, 1H); 6.91 (t, 1H); 6.57 (d, 1H); 6.31
(t, 1H). 19F NMR (THF):
ꢂ139.1 (br., 1F); ꢂ155.0 (d, br., 1F,
3JFF = 130 Hz). 1H NMR (THF + 2.2.1-cryptand):
7.71 (d, 2h); 7.36
d 7.62 (d, 2h);
Acknowledgements
d
d
The authors gratefully acknowledge financial support of this
work from the Program of the President of the Russian Federation
for the State Support of Leading Research Schools (Grant No. HIII-
4365.2010.3). The authors thank Dr. P.A. Khavrel for the help in
obtaining the 19F NMR spectra of the Li salt of complex 4, P&M
Company (Moscow) for the gift of chlorotrifluoroethylene and Prof.
I.F. Gunkin (Saratov State Technical University) for the gift of
metallic thallium.
(t, 2H); 7.24 (t, 1H); 7.03 (d, 1H); 6.88 (t, 1H); 6.67 (d, 1H); 6.13 (t,
1H). 19F NMR (THF + 2.2.1-cryptand):
d
ꢂ133.1 (d, br., 1F,
3
3JFF = 130 Hz); ꢂ155.4 (d, 1F, JFF = 130 Hz). Potassium salt, M = K.
1H NMR (THF):
d 7.65 (d, 2h); 7.30 (t, 2H); 7.23 (t, 1H); 7.10 (d, 1H);
6.88 (t, 1H); 6.37 (d, 1H); 6.14 (t, 1H). 19F NMR (THF):
d
ꢂ136.3 (d,
1F, 3JFF = 130 Hz); ꢂ154.8 (d, 1F, 3JFF = 130 Hz). 1H NMR (THF + 18-
crown-6): d 7.69 (d, 2h); 7.33 (t, 2H); 7.19 (t, 1H); 6.96 (d, 1H); 6.81
(t, 1H); 6.30 (d, 1H); 5.90 (t, 1H). 19F NMR (THF + 18-crown-6):
d
ꢂ131.6 (d, 1F, 3JFF = 130 Hz); ꢂ156.7 (d, 1F, 3JFF = 130 Hz). Thallium
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