The reactivity of potassium polyfluoroaryl-, polyfluoroalkenyl-, and perfluoroalkyltrifluoroborates and their hydrocarbon analogues towards acids of different strength: A systematic study of the hydrodeboration

Article abstract of DOI:10.1002/1521-3749(200205)628:4<883::AID-ZAAC883>3.0.CO;2-A

The hydrodeboration of the (fluoroorgano)trifluoroborates K [R_FBF₃] [R_F = C₆F₅, XCF=CF (X - F, cis- and trans-Cl, -C₃F₇O, cis-C₂F₅, trans-C₄F₉, -C₄H₉) and C₆F₁₃]and of the organotrifluoroborates K [RBF₃] (R = C₆H₅, cis- and trans-C₄H₉CH=CH, C₄H₉ and C₈H₁₇) with CH₃CO₂H (100%), CF₃CO₂H (100 %), aqueous HF and anhydrous HF was investigated. In the alkenyltrifluoroborates K [R′=CFCFBF₃] the formal replacement of BF₃ by a proton occurred stereospecifically under retention of the configuration. The ¹⁹F NMR spectra of K [R_FBF₃] in acids indicate strong interactions of the BF₃ group with protons or acid molecules.

Full text of DOI:10.1002/1521-3749(200205)628:4<883::AID-ZAAC883>3.0.CO;2-A

(
Fluoroorgano)fluoroboranes and -borates. 6 [1]
The Reactivity of Potassium Polyfluoroaryl-, Polyfluoroalkenyl-, and
Perfluoroalkyltrifluoroborates and their Hydrocarbon Analogues towards Acids
of Different Strength: A Systematic Study of the Hydrodeboration
a
a
b*
V. V. Bardin , S. G. Idemskaya , and H.-J. Frohn
a
Novosibirsk/Russia, N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS
Duisburg, Fachgebiet Anorganische Chemie, Gerhard-Mercator-Universität
b
Received November 26th, 2001.
Professor Hans Bürger dedicated on Occasion of his 65th Birthday
Abstract. The hydrodeboration of the (fluoroorgano)trifluorobo-
rates K [R BF ] [R ϭ C , XCFϭCF (X ϭ F, cis- and trans-
Cl, -C O, cis-C , trans-C , -C ) and C 13] and of the
organotrifluoroborates K [RBF ] (R ϭ C , cis- and trans-
CHϭCH, and with CH CO (100 %),
CO H (100 %), aqueous HF and anhydrous HF was investi-
gated. In the alkenyltrifluoroborates K [RЈCFϭCFBF ] the formal
replacement of BF
retention of the configuration. The F NMR spectra of K [R
in acids indicate strong interactions of the BF
or acid molecules.
3
by a proton occurred stereospecifically under
1
9
F
3
F
F
6 5
F
BF
3
]
3
F
7
2
F
5
4
F
9
4
H
9
6
F
3
group with protons
3
6 5
H
C
CF
4
H
9
C
4
H
9
C
8
H
17
)
3
2
H
3
2
Keywords: Borates; Fluoroborates; Hydrodeboration; NMR spec-
troscopy
3
(
Fluororgano)fluorborane und -fluoroborate. 6 [1]
Die Reaktivität von Kaliumpolyfluoraryl-, polyfluoralkenyl- und
perfluoralkyltrifluoroboraten und deren Kohlenwasserstoff Analoga gegenüber Säuren
unterschiedlicher Stärke: Eine systematische Studie zur Hydrodeborierung
Inhaltsübersicht. Die Hydrodeborierung der (Fluororgano)trifluo-
roborate K [R BF ] [R ϭ C , XCFϭCF (X ϭ F, cis- and trans-
Cl, -C O, cis-C , trans-C , -C ) und C 13] und der Orga-
notrifluoroborate K [RBF ] (R ϭ C , cis- und trans-C CHϭ
CH, C und C 17) mit CH CO H (100 %), CF CO H (100 %),
nyltrifluoroboratsalzen K [RЈCFϭCFBF
reospezifische Substitution von BF durch ein Proton. Die F-
NMR Spektren der Lösungen von K [R BF ] Salzen in Säuren
-Gruppe mit Protonen
3
] erfolgte formal die ste-
1
9
F
3
F
6
F
5
3
3
F
7
2
F
5
4
F
9
4
H
9
6
F
F
3
3
6
H
5
4
H
9
weisen auf starke Wechselwirkungen der BF
oder Säuremolekülen hin.
3
4
H
9
8
H
3
2
3
2
wässeriger HF und wasserfreier HF wurde untersucht. In den Alke-
Introduction
ment of the hydrocarbon group R in organotrifluoroborates
M [RBF ] or in organodifluoroboranes RBF by the highly
3
2
Recently we have elaborated simple and convenient prep-
arative approaches to the new classes of organoboron
compounds: the potassium salts of polyfluoroaryl-, poly-
fluoroalk-1-enyl- and perfluoroalkyltrifluoroborates [2Ϫ4]
and the polyfluorinated aryl-, alk-1-enyl and alkyldifluoro-
boranes [2, 3, 5]. The latter were obtained from the corre-
sponding salts K [R BF ] by fluoride abstraction using
Lewis acids (BF , AsF ) as fluoride acceptors. The synthesis
and some reactivities of their non-fluorinated analogues are
well known [6Ϫ9]. It should be expected that the replace-
electron-withdrawing poly- or perfluoroorgano group RF
will result in significant changes of the reactivity of the bo-
rates M [R BF ] and boranes R BF . These changes are
F
3
F
2
caused by the highly increased Lewis acidity of the three-
coordinated boron atom in R BF and the better leaving
F
2
Ϫ
Ϫ
ability of the perfluorocarbanion [RF] in [R BF ] com-
F
3
F
3
pared with the hydrocarbon analogues. This unique prop-
erty of fluorinated aryl- and alkenyldifluoroboranes can be
used for synthetic applications, e.g. the introduction of
3
5
fluoroorgano groups into XeF should be mentioned which
2
is based on the interaction of the electrophilic boron centre
with the highly nucleophilic fluorine atom in XeF [10].
2
*
Prof. Dr. H.-J. Frohn
Fachgebiet Anorganische Chemie der Universität
Lotharstr. 1
D-47048 Duisburg
Fax: (ϩ49)2 03-3 79 22 31
e-mail: frohn@uni-duisburg.de
The σ-electron-withdrawing effect of the RF groups re-
quires an appropriate Brønsted acidic medium for the prep-
Ϫ
aration of [R BF ] salts from the corresponding (fluoro-
F
3
organo)trialkoxyborates or boronic acids [2Ϫ4].
Z. Anorg. Allg. Chem. 2002, 628, 883Ϫ890
 WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002 0044Ϫ2313/02/628/883Ϫ890 $ 20.00ϩ.50/0 883

V. V. Bardin, S. G. Idemskaya, H.-J. Frohn
Hϩ
q R
Ϫ
1 was completely consumed whereas borate 3 underwent
only a partial conversion into trifluoroethene.
[
R
F
BX
3
]
F
BX
2
ϩ HX
Hϩ
q R
Ϫ
Ϫ
R
F
BX
2
ϩ F q [R
F
BFX
2
]
F
BFX ϩ HX
BF ϩ HX
3 2 4
ϩCF CO H, ϪK[BF ]
Hϩ
q R
1 ϩ 3 (1:1) ᎏᎏᎏᎏᎏᎏᎏǞ 2 (100 %) ϩ 3 ϩ 4
Ϫ
Ϫ
20°C, 40 minutes
R
F
BFX ϩ F q [R
F
BF
2
X]
F
2
Ϫ
Ϫ
F
R BF
2
ϩ F
q [R
F
BF
3
]
Both of the cis- and trans-isomers of potassium 2-chloro-
difluoroethenyltrifluoroborate 5 are less reactive than salt
X ϭ OAlk, OH
3
. The solution of salt 5 in aHF (Ϫ20 °C) displayed after
19
Ϫ
3 h still the F resonances of the starting compound while
salt 3 had already reacted under these conditions. Warming
to room temperature resulted in the fast conversion of bo-
rate 5 into 2-chlorodifluoroethene 6.
However, in highly Brønsted acidic solutions the [R BF ]
F
3
anion can undergo hydrodeboration. Therefore, we decided
to start a systematic study on (polyfluoroorgano)fluoro-
boron derivatives and investigated the reactions of (poly-
fluoroaryl)-, (polyfluoroalk-1-enyl)- and (perfluoroalkyl)tri-
fluoroborates with some selected protic acids. In addition,
the hydrodeboration of potassium phenyl-, hex-1-enyl, bu-
K [cis- and trans-ClCFϭCFBF
3
] ϩ aHF ᎏ20Ǟ°C
5
cis- and trans-ClCFϭCFH ϩ K [BF
4
]
tyl- and octyltrifluoroborates was studied and the results
6
Ϫ
in the series of [RBF ] were compared with those of the
3
Ϫ
[
R BF ] salts.
F 3
A slow hydrodeboration occurred in the solution of pot-
assium 1,2-difluoro-2-(heptafluoropropoxy)ethenyltrifluo-
roborate 7 (cis/trans ϭ 1 : 3) in 48 % HFaq.. After 3 days
at 20 °C ca. 50 % of the initial amount of borate 7 was
decomposed with an equal rate of reaction for both cis- and
trans-isomers. Under the action of aHF (20 °C) the borate
7 rapidly formed 1H-2-(heptafluoropropoxy)-1,2-difluoro-
ethene 8 (cis/trans ϭ 1 : 3).
Results and Discussion
Potassium trans-1,2-difluorohex-1-enyltrifluoroborate 1 is
slightly soluble in 100 % acetic acid (ϪH ca. 0 [11]) and
does not react at 20 °C within 24 h. Stronger acids like
0
aq
HF . (25 % HF : ϪH ϭ 0.88; 40 % HF : ϪH ϭ 2.08;
aq
0
aq
0
5
0 % HF : ϪH ϭ 3.84 [11]), 100 % CF CO H (ϪH 3.0
Potassium perfluoro-trans-hex-1-enyltrifluoroborate
9
aq
0
3
2
0
[
11]), or anhydrous HF (aHF) (ϪH 15 [12]) caused a fast
and potassium perfluoro-cis-but-1-enyltrifluoroborate 11
are well soluble in aHF at Ϫ50 to 20 °C. No hydrodebo-
ration of 9 was detected at 20 °C within 3 days. However,
after 30 days the partial hydrodeboration of borate 9 led to
1H-trans-undecafluorohexene-1 10 (9 : 10 ϭ 2.5 : 1). The
hydrodeboration of borate 11 proceeded relatively faster
and after 3 days traces of 1H-cis-heptafluorobutene-1 12
were observed in the solution.
0
carbon-boron bond cleavage to form trans-1,2-difluorohex-
1
-ene 2 in a quantitative yield.
ϩHX
K [trans-C
4
H
9
1
CFϭCFBF
3
] ᎏᎏᎏǞ trans-C
4
H
9
2
CFϭCFH
ϪK[BF4]
HX ϭ 27 % HFaq. (20 °C, 1 h), 100 % CF
aHF (Ϫ20 °C, Յ1 h)
3
CO
2
H (20 °C, 1Ϫ3 h),
K [R
F
CFϭCFBF
9, 11
3
] ϩ aHF ᎏǞ R
F
CFϭCFH ϩ K [BF
10, 12
4
]
2
0°C
The replacement of the alkyl group at C(2) in borate 1 by
the higher electron-withdrawing fluorine or chlorine atom
results in a decreased rate of hydrodeboration. Potassium
trifluoroethenyltrifluoroborate 3 did not react with 100 %
HOAc (20 °C, 24 h), but evolved trifluoroethene 4 with the
R
F
ϭ trans-C
4
F
9
(9, 10) 3 days, no reaction; 30 days, 28 % conver-
sion;
cis-C F (11, 12) 3 days, Յ 10 % conversion.
2 5
1
9
stronger acids. Monitoring by F NMR spectroscopy
showed, that the degree of conversion of salt 3 was ca. 20 %
in 27 % HFaq. (20 °C, 26 h) and total in 100 % CF CO H
It should be emphasized that the hydrodeboration of the
salts 1, 5, 7, 9 and 11 proceeds stereospecifically: the borates
K [trans-C H CFϭCFBF ], K [trans-C F CFϭCFBF ]
and K [cis-C F CFϭCFBF ] gave exclusively the alkenes
trans-C H CFϭCFH, trans-C F CFϭCFH and cis-
3
2
(20 °C, 18 h). In aHF the complete cleavage of the C-B
4
9
3
4
9
3
bond occurred at Ϫ30 °C within Յ 3 h.
2
5
3
4
9
4 9
C F CFϭCFH, respectively. The cis/trans ratio of the al-
ϩHX
2 5
K [CF
2
ϭCFBF
3
] ᎏᎏᎏǞ CF
2
ϭCFH
kenes RCFϭCFH was the same as in the corresponding
borates K [cis- and trans-RCFϭCFBF ] (R ϭ Cl, C F O).
ϪK[BF4]
3
4
3
3 7
HX ϭ 27 % HFaq. (20 °C, 26 h, 20 % conversion), 100 % CF
20 °C, 18 h), aHF (Ϫ30 °C, Յ 3 h)
3
CO
2
H
Potassium pentafluorophenyltrifluoroborate 13 is practi-
(
cally insoluble in 100 % CF CO H and showed no reaction
3
2
at 60Ϫ70 °C (5 h). Salt 13 did not react with 40 % HFaq.
at 20 °C within 4 days but in hot solution (85Ϫ95 °C) it
underwent a slow hydrodeboration with a half of life of
ca. 1 h. The total decomposition of borate 13 under those
The lower reactivity of borate 3 with respect to borate 1
towards hydrodeboration was confirmed by a competitive
reaction with trifluoroacetic acid. After 40 minutes borate
884
Z. Anorg. Allg. Chem. 2002, 628, 883Ϫ890

(Fluoroorgano)fluoroboranes and -borates. 6
conditions was completed within 6 h to yield pentafluoro-
27 % HFaq. at 70 °C. After 40 minutes salt K [C H BF ]
6 5 3
benzene 14 and K [BF ]. The solution of borate 13 in aHF
was consumed while borate K [C H BF ] was still present.
4
4 9 3
at Ϫ40 °C displayed a graduate broadening of the 19F res-
These results allow to build the following sequences of
reactivity of organotrifluoroborate salts towards hydrode-
boration: K [trans-C H CFϭCFBF ] Ͼ K [cis- and trans-
onance of the fluorine atoms bonded to boron and after
1
5Ϫ30 minutes the signal disappeared finally [3]. At 20 °C
4
9
3
the conversion of borate 13 into C F H and K [BF ] was
completed within Յ 18 h. It is interesting that the addition
C F OCFϭCFBF ] ഠ K [CF ϭCFBF ] Ն K [cis- and
6
5
4
3
7
3
2
3
trans-ClCFϭCFBF ] ഠ K [C F BF ] Ͼ K [cis-C F CFϭ
3
6
5
3
2 5
of K [HF ] to the aHF solution („basic HF“) of 13 has no
CFBF ] Ն K [trans-C F CFϭCFBF ] Ͼ K [C F BF ] and
2
3 4 9 3 6 13 3
effect on the 19F NMR spectrum of 13, but it accelerated
K [cis- and trans-C H CHϭCHBF ] Ͼ K [C H BF ] Ͼ K
4
9
3
6
5
3
strongly the hydrodeboration.
[C H BF ] ഠ K [C H BF ].
4
9
3
8
17
3
The comparison of the 19F NMR spectra of K [RBF3]
4
ϩ aHF, Ϫ K[BF ]
and K [R BF ] in acids and in basic solvents like MeCN,
K [C
6
1
F
5
0
BF
3
3
] ᎏᎏᎏᎏᎏǞ C
6
11
F
5
H
F
3
20°C, Յ 18 h
MeOH or acetone displays remarkable differences caused
by the interaction of the organotrifluoroborate anion with
the acid. Generally, the dissolution of K [RBF ] and K
2 4
ϩ aHF ϩ K [HF ], Ϫ K [BF ]
K [C
F
6 5
BF
] ᎏᎏᎏᎏᎏᎏᎏᎏǞ C F H
6 5
11
3
20°C, 0.5 h
10
[R BF ] salts in acids leads to a deshielding of the BF
F
3
3
resonances in the 19F NMR spectra. The broadening of the
Potassium perfluoroalkyltrifluoroborates are the most
stable borates towards the hydrodeboration. No changes
were found in the solution of potassium perfluorohexyltri-
fluoroborate 15 in aHF after 10 days at 20 °C as well as in
BF signal can be moderate (for example, 1 in 100 % HOAc,
3
τ1/2 100 Hz; 9 in aHF (Ϫ30 °C), τ1/2 153 Hz or 17 in 27 %
HFaq., τ1/2 302 Hz) or extreme (K [C H BF ] 18 and K
4
9
3
[C H BF ] 19 both in 27 % HFaq.: in both cases no BF3
8
17
3
K [HF ]-aHF solutions (20 °C, 7 days).
signals were observed).
2
The 19F NMR spectral data of the K [RBF ] and K
3
6 3 2
K [C F13BF ] ϩ aHF or K [HF ]-aHF ᎐ᎏᎏᎏᎏǞ no reaction
20°C, 10 or 7 days
[
R BF ] salts in 100 % HOAc are presented in Table 1. The
F 3
15
fluorine atoms bonded to boron are deshielded in the series
of alkenyl- and alkyltrifluoroborates when the perfluorocar-
To complete the picture of reactivities of potassium or-
ganotrifluoroborates with protic acids, we studied the reac-
tivity of some hydrocarbon analogues with the same pro-
tic acids.
It was found that the potassium salts of hex-1-enyltrifluo-
roborate 16, phenyltrifluoroborate 17, butyltrifluoroborate
bon group R was replaced by the hydrocarbon group R.
F
In the series of alkenyl borates [RЈCFϭCFBF ], the fluo-
rine atoms in cis-position to the BF group, (borates 1, 3
3
3
and 9) are deshielded when going from MeCN to HOAc
solutions and the ∆δ(F) values are diminished from RЈ ϭ
C F to RЈ ϭ F and RЈ ϭ C H (borate 7 is only very
4
9
4
9
1
8 and octyltrifluoroborate 19 did not react with 100 %
19
purely soluble in 100 % HOAc, therefore its F NMR spec-
HOAc at 20 °C. The C-B bond of 16 was cleaved completely
by 27 % HFaq. within 1 h (20 °C) to form hex-1-ene. The
hydrodeboration of K [C H BF ] 17 with 27 % HF pro-
trum was not analysed). In contrast, the resonances of the
1
fluorine atoms F at C-1 are shifted to low frequencies and
6
5
3
aq.
the ∆δ value becomes a minimum in the case of the per-
fluorohexyltrifluoroborate anion. The solution of
ceeded slowly at 20 °C, whereas 17 was converted into ben-
zene at 50 °C within 2 h. The alkylborate 19 formed octane
K
[
C F BF ] in HOAc (100 %) displayed slightly deshielded
6 5 3
and K [BF ] (27 % HFaq., 65Ϫ70 °C) in a slow reaction
4
∆
δ(F) values of the para-fluorine atom and of the BF3
(43 % conversion of 19 after 2.5 h). In aHF 19 was cleaved
group, whereas the ortho- and meta-positions were not
changed.
quantitatively within a few minutes.
Solutions of potassium (polyfluoroorgano)trifluorobo-
rates in anhydrous HF, the strongest acid which we investi-
gated, are characterized by significantly higher differences
in chemical shifts with respect to those in basic solvents or
in aqueous HF (Table 2). For instance, the ∆δ(F) values of
2
0°C
K [RBF
3
] ϩ 100 % HOAc ᎏᎏǞ no reaction
R ϭ cis- and trans-C
4
H
9
CHϭCH 16 (1 h), C H 17 (60 h), C H
6 5 4 9
18 (3 h), C 17 19 (3 h)
8
H
ϩ 27% HFaq., Ϫ K [BF
4
]
both vinylic fluorine atoms of the anions [RЈCFϭCFBF
3
]
K [RBF
3
] ᎏᎏᎏᎏᎏᎏᎏǞ RH
(
RЈ ϭ Cl, C F , C F ) changed up to ±9 ppm. In the penta-
2
5
4 9
R ϭ cis- and trans-C
4
H
9
CHϭCH (20 °C, 1 h), C
6
H
5
(20 °C, 48 h
fluorophenyltrifluoroborate anion a large deshielding is ob-
served for the meta- and especially for the para-fluorine
or 50 °C, 2 h), C 17 (65 Ϫ 70 °C, 2.5 h; 43 % conversion of 19)
8
H
atoms [3].
ϩ aHF, Ϫ K [BF
4
]
We explain the observed changes of 19F NMR shift val-
K [C H17BF ] ᎏᎏᎏᎏᎏᎏǞ C H
8 3 8 18
20°C, few minutes
19
ues in acids of different protonation ability by the pro-
tonation of the fluorine atoms bonded to boron, which bear
the majority of the negative charge or as a strong donor-
acceptor interaction of these fluorine atoms with an acid
molecule (Scheme 1).
The higher stability of alkyltrifluoroborates with respect
to aryltrifluoroborates was confirmed by a competitive re-
action of an equimolar mixture of borates 17 and 18 with
Z. Anorg. Allg. Chem. 2002, 628, 883Ϫ890
885

V. V. Bardin, S. G. Idemskaya, H.-J. Frohn
Path 1
In media of high acidity:
Path 1 includes the dipolar conjugated addition of HX
to the carbon-boron bond. The transition state C favours
the stereospecific cleavage of the alkenyl-boron bond. In the
alternativ path 2 the negative charge of a boron-bonded
fluorine atom orientates the (3cϪ2e) addition product of
the proton to the CϭC double bond and leads to the stereo-
specific hydrodeboration product. The primary protonation
of carbon C-1 (path 3) can be neglected, because it leads to
Ϫ
ϩ
3 2 2
[RBF ] ϩ H v [RBF (F-H)] v RBF ϩ HF
A
Path 2
In media of low acidity:
Ϫ
Ϫ
3 2
[RBF ] ϩ HX v [RBF (F···H-X)]
B
ϩ
Ϫ
the betaine RЈC F-CHF-BF3 with a planar carbocationic
centre, which gives rise to a non-stereospecific cleavage of
the carbon-boron bond.
Scheme 1
In order to simplify the interaction of fluoroborates with
acids we distinguish only two borderline cases of high and
low acidity. In a highly protonating medium (path 1) the
organotrifluoroborate anion is in equilibrium with the cor-
responding Ϫ not significantly solvated Ϫ organodifluoro-
borane via the intermediately formed neutral species A. In
a medium of low acidity (path 2) the formation of the ad-
duct B is predominant without a significant conversion into
the corresponding organodifluoroborane. The formation of
A as well as of B have principally in common the increase
of the positive charge on the boron atom which causes a
charge redistribution as well in the residual non-protonated
In the case of the hydrodeboration of K [C F BF ] in
6
5
3
aHF all three paths are reasonable. At first glance the
hydrodeboration of K [C F BF ] in aHF presents a para-
6
5
3
dox, because in “basic” HF (in the presence of K [HF ]) the
2
C-B cleavage is significantly accelerated under less acidic
conditions. Path 1 (Scheme 1) helps to understand this
Ϫ
paradox: in “basic” HF the [C F BF ] /C F BF equilib-
6
5
3
6
5
2
rium is shifted towards the borate species. Additionally, it
should be mentioned that the borane C F BF does not
6
5
2
undergo hydrodeboration in aHF [3].
B-F fragment as in the organo group R or R . The lower
Experimental
F
symmetry of the borate anion in the protonated species A
or in the adduct B increases the electric quadrupole of the
boron atom. The observed broadening of the B-F reson-
ances may be caused by the electric quadrupole and/or by
intermolecular exchange processes.
The NMR spectra were measured on Bruker spectrometers WP
1
19
13
2
1
3
00 ( H at 200.13 MHz, F at 188.28 MHz), AM 400 ( C{H} at
1
9
1
00.61 MHz,
F at 376.50 MHz), AVANCE 300 ( H at
11
19
1
00.13 MHz, B at 96.29 MHz, F at 282.40 MHz), DRX 500 ( H
11
13
at 500.13 MHz, B at 160.46 MHz, C{H} at 125.76 MHz). The
H, 13C), BF · OEt /CDCl
3
Based on our results we propose in Scheme 2 two paths
chemical shifts are referred to TMS (
1
3
2
1
1
19
for the hydrodeboration reaction of K [RЈCFϭCFBF ] salts
3 6 6 3 2
15 % v/v ( B) and CFCl ( F) [with C F or CF CO H as second-
3
with acids. For simplification we neglect in both paths the
solvation of the alkenyltrifluoroborate anion.
ary references (Ϫ162.9 ppm or (Ϫ76.53 ppm, respectively)]. The com-
position of the reaction mixtures and the yields of products were
1
19
determined by H or F NMR spectroscopy. The fluorine atoms
2
F
at C-2 in alkenyltrifluoroborates are specified by cis or trans
relative to the position of the BF group. The IR spectra were re-
3
corded on a Bruker Vector 22 FT-spectrometer using KBr pellets.
The elemental analysis was performed in the N. N. Vorozhtsov No-
vosibirsk Institute of Organic Chemistry (Novosibirsk).
All manipulations with aqueous and anhydrous HF were per-
formed in FEP (block copolymer of tetrafluoroethylene and hexa-
fluoropropylene) equipment.
Potassium (polyfluoroorgano)trifluoroborates 1, 3, 5, 9, 11, 13 and
1
5 were prepared as described recently [2, 3, 4]. The synthesis of K
[
cis- and trans-C OCFϭCFBF ] will be presented elsewhere.
3
F
7
3
Potassium phenyltrifluoroborate K [C H BF ] 17
6
5
3
Phenylmagnesium bromide prepared from PhBr (31 g, 0.2 mol),
Mg (5 g, 0.2 mol) in ether (200 ml) was added drop by drop to the
solution of B(OMe) (22 g, 0.2 mol) in ether (100 ml) at Ϫ65 to
3
Ϫ70 °C within 2 h. The resulting suspension was stirred for 1 h and
then warmed to 20 °C. The reaction mixture was hydrolysed with
5
% aqueous HCl, the organic phase was separated, the aqueous
one was extracted with ether and the combined ether phases were
dried with MgSO . Ether was removed at reduced pressure, the
residue was dissolved in MeOH (40 ml) and poured into the stirred
solution of K [HF ] (60 g, 0.77 mol) in water (150 ml). After 5 min-
4
2
Scheme 2
utes the precipitate was filtered off, dried and extracted with hot
886
Z. Anorg. Allg. Chem. 2002, 628, 883Ϫ890

(Fluoroorgano)fluoroboranes and -borates. 6
Table 1 The 19F NMR spectra of K [RBF
F 3
] and K [R BF
] in HOAc (100 %)a
3
R
trans-
BuCHϭCH
trans-16
cis-
BuCHϭCH
cis-16
C
4
H
9
C
6
H
5
trans-
CF
2
ϭCF
trans-
CFϭCF
9
C
6
F
13
6 5
C F
BuCFϭCF
4 9
C F
f
d
3e
15g
13h
18
17
1
δ(F) (BF
3
)
Ϫ135.70
4.38
Ϫ130.66
4.12
Ϫ135.33
Ϫ137.32
Ϫ139.89
Ϫ141.86
Ϫ142.54
Ϫ150.46
Ϫ132.24
b
c
∆
∆
∆
∆
δ (BF
3
)
)
δ (BF
3
c
3.76
3.44
2.11
Ϫ2.40
0.53
1.51
Ϫ1.83
0.71
1.49
Ϫ1.66
0.89
1.36
Ϫ0.79
1.19
1
i
δ (F )
0.78
2
c
δ (F -cis)
a
3
The fluorine atoms F-2 are specified by cis or trans relative to the position of the BF group.
b
c
d
e
f
∆
δ ϭ δ(in 100 % HOAc) Ϫ δ(in CD
3
OD).
3
CN).
∆
δ ϭ δ(in 100 % HOAc) Ϫ δ(in CD
3
2
1
3
2
3
4
2
2
1
δ(F): Ϫ156.29 (dtq, J(F ,F ) 120 Hz, J(F ,H ) 24 Hz, J(F ,BF) 9 Hz, 1F, F ), Ϫ173.14 (d, 1F, F ).
δ(F): Ϫ99.90 (d, 1F, F -trans), Ϫ123.29 (ddq, J(F -cis,F ) 111 Hz, J(F -cis,F -trans) 88 Hz, J(F -cis,BF) 10 Hz, 1F, F -cis), Ϫ197.48 (d, 1F, F ); J(F,B) 45 Hz.
δ(F): Ϫ80.85 (3F, F ), Ϫ116.60 (2F, F ), Ϫ124.54 (2F, F ), Ϫ126.03 (2F, F ), Ϫ154.72 (1F, F ), Ϫ176.27 (d, J(F ,F ) 131 Hz 1F, F ).
δ(F): Ϫ80.67 (3F, F ), Ϫ121.78, Ϫ122.45, Ϫ123.09 (6F, F ,F ,F ), Ϫ125.73 (2F, F ), Ϫ133.37 (2F, F ).
2
3
2
1
2
2
2
4
2
2
1
1
6
3
4
5
1
3
2
1
2
g
h
i
6
2
3
4
5
1
2
6
4
3
5
δ(F): Ϫ135.42 (2F, F ,F ), Ϫ159.96 (1F, F ), Ϫ165.26 (2F, F ,F ).
4
∆
δ(F ).
Table 2 The 19F NMR spectra of K [R
] in aHF (Ϫ20 °C)a.
F
BF
3
R
C
6
F
13
trans-
CFϭCF
9
cis-
trans-
ClCFϭCF
trans-5
cis-
ClCFϭCF
cis-5
6 5
C F
C
4
F
9
C
2
F
5
CFϭCF
5c
d
11
e
f, g
g, h
13 [4]
1
δ(F) (BF
3
)
Ϫ148.67
3.15
0.38
Ϫ141.18
2.85
Ϫ5.95
6.93
Ϫ139.70
2.77
Ϫ7.94
9.23
Ϫ131.88
b
∆
∆
∆
δ (BF
3
)
1.55
1
b
b
2
6
δ (F )
Ϫ7.64
5.28
Ϫ7.14
7.34
∆δ (F ,F ) Ϫ1.03,
∆δ (F ,F ) 2.04,
2
3
5
δ (F )
4
∆
δ (F ) 5.45
a
The fluorine atoms F-2 are specified by cis or trans relative to the position of the BF
3
group.
b
c
d
e
f
∆
δ ϭ δ(in aHF) Ϫ δ(in CH
3
CN).
6
1
δ(F): Ϫ79.37 (3F, F ), Ϫ120.04, Ϫ120.45, Ϫ121.23, Ϫ124.17 (4 CF
δ(F): Ϫ79.49 (t, J(F ,F ) 9 Hz, 3F, F ), Ϫ115.89 (2F, F ), Ϫ122.84, Ϫ124.44 (2F, F and 2F, F ), Ϫ170.23 (d, J(F ,F ) 133 Hz, 1F, F ), Ϫ159.01 (d, 1F, F ).
δ(F): Ϫ82.76 (3F, F ), Ϫ119.03 (2F, F ), Ϫ148.24 (1F, F ), Ϫ139.70 (1F, F ).
δ(F): Ϫ121.23 (d, J(F ,F ) 129 Hz, 1F, F ), Ϫ164.78 (d, 1F, F ).
2
), Ϫ132.20 (2F, F ).
4
6
4
6
3
4
5
3
2
1
2
1
4
3
2
1
3
1
2
2
1
g
h
The shift value of the BF group cannot be determined because of the strong broadening of the signal.
3
2
1
δ(F): Ϫ95.77 (s,1F, F ), Ϫ154.07 (br,1F, F ).
acetone (270 ml). Acetone was removed under reduced pressure
C H BF K (164,02): calculated C 29.29, H 5.53, F 34.75; found C
4 9 3
4
and the product was dried over P O10 to yield 21 g (57 %) of salt 17.
29.7, H 5.66, F 34.7 %.
19F NMR (CD
7 Hz) [13]}.
IR (KBr) ν¯ (cmϪ1): 3072 w, 3052 w, 3013 w, 1597 w, 1434 s, 1265 w, 1244 s,
1
6
CN): δ ϭ Ϫ140.76 (q, J(F,B) 51 Hz) {lit. δ ϭ Ϫ142 ( J(F,B)
1
1
1
2
3
3
4
3
3
6
H NMR (acetone-d ): δ ϭ 1.23 (4H, H , H ), 0.84 (t, J(H ,H ) 6.5 Hz,
4 1 19
5
3H, H ), 0.16 (2H, H ). F NMR (acetone-d ): δ ϭ Ϫ139.09 (apparent
doublet). B NMR (acetone-d ): δ ϭ 5.61 (q, J(B,F) 52 Hz).
IR (KBr) ν¯ (cm ): 2961 s, 2920 s, 2874 m, 2855 s, 1466 w, 1377 w, 1345 w,
1321 m, 1300 w, 1283 w, 1243 s, 1210 w, 1126 s, 1103 vs, 1088 vs, 1069 s,
6
11
1
6
Ϫ1
226 s, 1181 w, 1080 m, 1030 s, 991 vs, 975 vs, 937 vs, 906 vs, 752 vs, 700 s,
07 m, 540 w.
957 vs, 933 vs, 920 s, 866 s, 844 s, 754 w, 721 w, 571 w.
Potassium butyltrifluoroborate K [C H BF ] 18
4
9
3
Potassium octyltrifluoroborate K [C H BF ] 19
Butylmagnesium bromide prepared from BuBr (13.7 g, 0.1 mol),
Mg (2.4 g, 0.1 mol) in ether (100 ml) was added drop by drop to
the solution of B(OMe) (10 g, 0.1 mol) in ether (100 ml) at Ϫ65
3
to Ϫ70 °C within 90 minutes The resulting suspension was warmed
to 20 °C within 3 h. The reaction mixture was hydrolysed with 5 %
4
HClaq., the organic phase was separated and dried with MgSO .
8
17
3
Borate 19 was prepared similar to 18 by reacting C
8
H
17MgBr [from
C
8
H
17Br (19 g, 0.09 mol), Mg (2.4 g, 0.1 mol) and ether (100 ml)]
with B(OMe) (22 g, 0.2 mol) in ether (100 ml) at Ϫ55 °C followed
by hydrolysis and treatment of the crude octylboronic acid with K
HF ] (42 g, 0.92 mol) in water (100 ml) and MeOH (30 ml). Crys-
3
[
2
The solvent was removed at reduced pressure. The residue was dis-
solved in MeOH (60 ml) and poured into the stirred solution of K
tallization from MeOH gave 7.5 g (30 % based on C
8
H
17Br) of
salt 19.
2
[HF ] (31 g, 0.4 mol) in water (100 ml). After 30 minutes the pre-
1
8
H NMR (acetone-d
6
): δ ϭ 1.28 Ϫ 1.24 (12H, 6CH
2
), 0.86 (3H, H ), 0.10
cipitate was filtered off, dried and continuously (5 h) extracted with
hot acetone (700 ml). The solvent was removed under reduced
1
19
11
(2H, H ). F NMR (acetone-d
6
): δ ϭ Ϫ139.26 (apparent doublet).
): δ ϭ 5.31 (q, J(B,F) 62 Hz) {lit. δ( H, DMSO-d
B
1
1
NMR (acetone-d
1
d
6
6
) ϭ
pressure and the product was dried over P
4
O
10 to yield 5.7 g (35 %)
8
1
19
.30 Ϫ 1.05 (12H, 6CH
2
), 0.81 (3H, H ), Ϫ0.08 (2H, H ); δ( F, DMSO-
1
of salt 18.
6
) ϭ Ϫ137.5 ( J(F,B) not reported) [6]}.
Z. Anorg. Allg. Chem. 2002, 628, 883Ϫ890
887

V. V. Bardin, S. G. Idemskaya, H.-J. Frohn
IR (KBr) ν¯ (cmϪ1): 2954 m, 2917 s, 2873 m, 2850 s, 1632 w, 1468 w, 1352 vw,
C H CFϭCFBF ] (80 mg, 0.35 mmol) and 27 % HF (0.5 ml) un-
4
9
3
aq.
1
9
329 m, 1293 m, 1250 m, 1205 m, 1100 s, 1071 s, 1040 m, 1010 m, 988 w,
41 s, 920 s, 888 s, 826 m, 771 w, 723 w, 708 w, 573 w.
der stirring. After 70 minutes the quantitative formation of trans-
1
9
C
4
H
9
CFϭCFH was detected ( F NMR).
The suspension of borate K [trans-C
0.57 mmol) in 100 % CF CO H (0.5 ml) was stirred at 20 °C for
4
9 3
H CFϭCFBF ] (129 mg,
Potassium hex-1-enyltrifluoroborate K [C H CHϭ
4
9
3
2
CHBF ] 16
3 h and formed a turbid solution. Hexane (1 ml) and water (1 ml)
were added. The upper organic phase was separated. The F NMR
3
1
9
This borate was prepared similar to the alkylborates by the reaction
of cis- and trans-C CHϭCHMgBr [from cis- and trans-
CHϭCHBr (16.3 g, 0.1 mol), Mg (2.4 g, 0.1 mol) and THF
60 ml)] with B(OMe) (11 g, 0.1 mol) in ether (40 ml) at Ϫ70 °C
and following treatment of the reaction mixture with K [HF ] (32 g,
.41 mol) in water (100 ml) and MeOH (25 ml). The organic phase
was separated, the aqueous one was extracted with acetone
100 ml), the combined acetone extracts were dried with Na SO
and the solvent was removed under reduced pressure to yield 8.8 g
46 % based on C 11Br) of the white product 16.
CHϭCHBF ].
4 9
spectrum showed the formation of trans-C H CFϭCFH in 95 %
yield.
4
H
9
4 9
C H
(
A mixture of K [trans-C
and K [CF ϭCFBF ] 3 (82 mg, 0.43 mmol) was stirred in 100 %
CF CO H (1.5 ml) at 20 °C. The F NMR spectrum showed the
4 9 3
H CFϭCFBF ] 1 (100 mg, 0.44 mmol)
3
2
2
3
1
9
0
3
2
4 9
complete conversion of borate 1 into trans-C H CFϭCFH within
(
2
4
40 minutes.
Ϫ
2
2
2
The resonances of the [CF
2
ϭCFBF
3
]
anion [Ϫ94.75 (dd, J(F -cis,F -trans)
3
2
1
2
3
2
1
8
1
0 Hz, J(F -trans,F ) 20 Hz, 1F, F -trans), Ϫ118.61 (dd, J(F -cis,F )
(
6
H
2
1
15 Hz, 1F, F -cis), Ϫ200.60 (dd, 1F, F ) and Ϫ145.97 (br, BF
3
) ppm] and,
K [cis-C
4
H
9
3
probably,
CFBF (F···HO
of
CCF
[CF ϭCFBF (O CCF )
]
Ϫ
or
[CF ϭ
2
n
2
3 3Ϫn
2
2
-
2
2
1
3
n
2
3
)
3Ϫn] - [Ϫ95.63 (d, J(F -cis,F -trans) 78 Hz, 1F, F-
3
H NMR (CD OD): δ ϭ 5.77 Ϫ 5.32 (CHϭCH), 2.18 (2H, H ), 1.32 (4H,
6 19 1
3
2
1
4
5
2trans), Ϫ120.35 (dd, J(F -cis,F ) 109 Hz, 1F, F-2cis), Ϫ199.21 (d, 1F, F-
1)] (the resonance of the BF group was not detected) were observed still
2
after 3 h besides the resonances of CF ϭCFH [Ϫ101.30 (1F, F -trans),
1
3
H ,H ), 0.89 (3H, H ). F NMR (CD OD): δ ϭ (134.78 (q, J(F,B) 50 Hz).
13
11
1
n
B NMR (CD
3
OD): δ ϭ 3.10; (q, J(B,F) 56 Hz). C{H} NMR (CD
3
OD):
δ ϭ 140.51 (q, J(C-2,F) 4.5 Hz, C-2), (C-1) not observed, 33.87 and 32.18
C-4,5), 23.54 (C-3), 14.49 (C-6).
2
3
2
Ϫ127.96 (1F, F -cis) and Ϫ206.77 (1F, F ) ppm].
(
1
3
H NMR (DMF): δ ϭ 5.58 Ϫ 5.34 (CHϭCH), 2.20 (2H, H ), 1.27 (4H,
4 9 3
The borate K [trans-C H CFϭCFBF ] (37 mg, 0.16 mmol) was
placed in a FEP trap and pre-cooled aHF (Ϫ20 °C) (0.3 ml) was
added. After shaking the white suspension for 1 h at Ϫ20 °C the
4
5
6
19
1
H ,H ), 0.86 (3H, H ). F NMR (DMF): δ ϭ Ϫ133.24 (q, J(F,B) 50 Hz).
1
3
2
3
1
2
6
H NMR (DMSO-d ): δ ϭ 5.77 (br, 1H, H ), 5.30 (dqt, J(H ,H ) 13.3 Hz,
1 3 1 3 4 5
1
4
J(H ,BF) 6 Hz, J(H ,H ) 1.3 Hz, 1H, H ), 2.23 (2H, H ), 1.35 (4H, H ,H ),
3
6
5
6
13
0
.93 (t, J(H ,H ) 7 Hz, 3H, H ). C{H} NMR (DMSO-d
6
): δ ϭ 136.27 (C-
4 9
quantitative conversion of borate 1 into trans-C H CFϭCFH and
2
), 54.54 (C-1), 32.39 and 30.54 (C-4,5), 22.09 (C-3), 14.11 (C-6).
19
K [BF
The salt K [CF
100 % CH CO H (1 ml) at 20 °C for 24 h without any reaction
4
] had proceeded ( F NMR).
4 9 3
K [trans-C H CHϭCHBF ].
1
3
2
ϭCFBF ] (93 mg, 0.49 mmol) was stirred with
3
3
H NMR (CD OD): δ ϭ 5.77 Ϫ 5.32 (CHϭCH), 2.00 (2H, H ), 1.32 (4H,
6 19 11
4
5
H
and H ), 0.89 (3H, H ). F NMR (CD
3
OD): δ ϭ Ϫ140.08. B NMR
3
2
1
13
19
(
(
(
CD
3
OD): δ ϭ 3.10 (q, J(B,F) 56 Hz). C{H} NMR (CD OD): δ ϭ 138.32
3
( F NMR).
3
q, J(C-2,F) 4.7 Hz, C-2), (C-1) not observed, 36.56 and 32.94 (C-4,5), 23.38
C-3), 14.38 (C-6).
The salt K [CF ϭCFBF ] (83 mg, 0.44 mmol) was stirred with
2 3
1
3
4
19
H NMR (DMF): δ ϭ 5.58 Ϫ 5.34 (CHϭCH), 1.99 (2H, H ), 1.27 (4H, H
and H ), 0.86 (3H, H ). F NMR(DMF): δ ϭ Ϫ138.53.
2
7 % HFaq. (0.8 ml) at 20 °C. The F NMR spectra showed the
5
6
19
Ϫ
Ϫ
molar ratio of anions [CF
1 (26 h).
2
ϭCFBF
3
]
to [BF
4
]
9 : 1 (6 h) and 4 :
1
3
3
2
3
2
6
H NMR (DMSO-d ): δ ϭ 5.83 (dt, J(H ,H ) 7 Hz, 1H, H ), 5.39 (dqt,
3 1 4 1 3 1
1
2
J(H ,H ) 17.5 Hz, J(H ,BF) 4 Hz, J(H ,H ) 1.5 Hz, 1H, H ), 2.02 (2H,
19
2
2
2
2
3
4
5
3
6
5
6
13
F NMR (27 % HFa 3q .): δ ϭ Ϫ98.97 (d, J(F -cis,F -trans) 92 Hz, 1F, F -
H ), 1.35 (4H, H and H ), 0.93 (t, J(H ,H ) 7 Hz, 3H, H ). C{H} NMR
2
1
2
1
trans), Ϫ123.29 (dd, J(F -cis,F ) 111 Hz, 1F, F -cis), Ϫ200.08 (d, 1F, F ),
(
(
DMSO-d
C-3), 14.00 (C-6).
6
): δ ϭ 134.24 (C-2), 53.53 (C-1), 35.09 and 31.52 (C-4,5), 21.92
2
3
Ϫ142.66 (q, J(F,B) 38 Hz, 3F, BF ).
The ratio cis-16/trans-16 was 2.4 : 1. The reported 19F NMR (ace-
tone-d ) data for K [trans-C CHϭCHBF ]:
2 3
The borate K [CF ϭCFBF ] (106 mg, 0.56 mmol) was stirred with
1
3 2
00 % CF CO H (1 ml) in a sealed ampoule at 20 °C for 18 h. The
6
4
H
9
3
1
δ ϭ 11.0 (relative to BF
3
· OEt
2
) with J(F,B) of ϳ52 Hz [7].
probe was a fine suspension and showed the presence of CF ϭ
2
Ϫ1
IR (KBr) ν¯ (cm ): 2959 s, 2928 s, 2873 m, 2860 m, 1645 m, 1632 m, 1466 m,
CFH while borate 3 was absent.
1
5
404 m, 1379 m, 1109 vs, 1085 s, 995 vs, 944 vs, 919 vs, 744 w, 708 w, 623 vw,
94 vw, 484 w.
Anhydrous HF (0.25 ml) was added to the borate K [CF ϭCFBF ]
2
3
(
27 mg, 0.14 mmol) at Ϫ50 °C and the suspension was kept at
Product 16 contained additionally an admixture (ca. 10 mol %) of
K [(cis- and trans-C CHϭCH) BF ] (cis/trans ϭ 2.4 : 1) which
was identified by its 1 F and B NMR spectra.
1
9
Ϫ30 °C for 3 h. The F NMR spectrum showed the quantitative
conversion of borate 3 into CF
4
H
9
2
2
9
11
2
ϭCFH and K [BF
4
].
1
9
K [(cis-C
4
H
9
CHϭCH)
2
BF
3
2
]. F NMR (CD
3
OD):
The borate K [ClCFϭCFBF
0
way as above. The F NMR spectrum (Ϫ20 °C) showed the pres-
ence of the residual anions [ClCFϭCFBF
3
] (cis/trans ϭ 49 : 51) (37 mg,
1
1
OD): δ ϭ 27.87 (s, τ1/2 53 Hz). 19F NMR
δ ϭ Ϫ133.45. B NMR (CD
DMF): δ ϭ Ϫ131.76.
.18 mmol) was treated with aHF (0.25 ml) at Ϫ20 °C in a similar
(
1
9
1
9
K [(trans-C
4
H
9
CHϭCH)
2
BF
3
2
.
F NMR (CD
3
OD):
Ϫ
3
] (Table 2) (cis/trans ϭ
1
1
OD): δ ϭ 27.87 (s, τ1/2 53 Hz). 19F NMR
δ ϭ Ϫ137.37. B NMR (CD
DMF): δ Ϫ136.36.
2
2
4
: 6), and of the olefins cis-ClCFϭCFH [Ϫ104.35 (dd, J(F -
(
3
2
1
2
trans,H) 11 Hz, J(F -trans,F ) 10 Hz, 1F, F -trans), Ϫ156.31 (dd,
2
1
1
J(F ,H) 73 Hz, 1F, F ) ppm] and trans-ClCFϭCFH [Ϫ129.46 (d,
2
3
1
2
2
1
1
F, F -cis), Ϫ173.13 (dd, J(F ,F -cis) 130 Hz, J(F ,H) 74 Hz, 1F,
Reactions of potassium polyfluoroalk-1-
enyltrifluoroborates with acids
1
Ϫ
4
F ) ppm]; besides [BF ] (Ϫ148.43 ppm). Warming to 20 °C led to
the quantitative conversion of the borate isomers into cis- and
trans-ClCFϭCFH (cis/trans ϭ 4 : 6).
The salt K [trans-C
pended and stirred in 100 % CH
no reaction could be detected ( F NMR).
4
H
9
CFϭCFBF
3
] (51 mg, 0.22 mmol) was sus-
H (1 ml) at 20 °C. After 24 h
3
9
CO
2
2 5 3
Similarly, K [cis-C F CFϭCFBF ] (44 mg, 0.15 mmol) was dis-
1
solved in aHF (0.25 ml) at Ϫ50 °C and the solution was kept at
Ϫ30 °C for 4 h but showed no reaction. After 3 days at 20 °C the
A FEP trap was charged in sequence with hexane (0.5 ml), PhCF
3
1
9
(26 mg, 0.17 mmol, as quantitative reference), borate K [trans-
F NMR spectrum contained the resonances of the starting borate
888
Z. Anorg. Allg. Chem. 2002, 628, 883Ϫ890

(Fluoroorgano)fluoroboranes and -borates. 6
1
1 (Table 2), cis-C
2
F
5
CFϭCFH (content was less than 10 %) and
warming to 20 °C led to the fast and quantitative formation of
Ϫ
19
[BF
4
]
(Ϫ148.24 ppm, only traces).
C
6 5 4
F H and K [BF ] (1 : 1) within 30 minutes ( F NMR).
4
F
9
3
Similarly, K [trans-C CFϭCFBF ] (45 mg, 0.11 mmol) was dis-
solved in aHF (0.25 ml) at Ϫ30 °C. The solution was maintained
The reaction of potassium
perfluorohexyltrifluoroborate with aHF
at 20 °C for 3 days to show only 19F resonances of starting borate
9
4 9
(Table 2). After 30 days at 20 °C the formation of trans-C F CFϭ
19
CFH was detected (9 : 10 ϭ 2.5 : 1, F NMR).
6 3
The borate K [C F13BF ] (72 mg, 0.17 mmol) was suspended in
aHF (0.6 ml) at Ϫ50 °C. Warming to 20 °C resulted in a solution.
It was kept for 10 days at 20 °C but displayed no reaction (Table 2).
Similarly, K [cis- and trans-C OCFϭCFBF ] 7 (cis/trans ϭ 1 : 3;
3
F
7
3
3
3
3 mg, 0.09 mmol) was dissolved in aHF (0.3 ml) at Ϫ20 °C. After
d at 20 °C the 19F NMR spectrum showed the resonances of cis-
The solution of K [C
6
F
13BF
3
] (64 mg, 0.15 mmol) in aHF (0.3 ml),
Ϫ
3 7 4
and trans-C F OCFϭCFH (ca. 1 : 2.5) and the [BF ] anion.
which contained K [HF
at 20 °C and displayed no reaction ( F NMR).
2
] (30 mg, 0.38 mmol), was kept for 7 days
The solution of borate 7 (44 mg, 0.12 mmol) in 48 % HFaq. (0.5 ml)
was kept at 20 °C. After 3 d the concentration of salt 7 was reduced
to ca. 50 %. Parallel a precipitation occurred and the resonance of
19
Ϫ
19
the [BF
of C
solubility of that polyfluoroalkene in HFaq.
4
]
anion appeared in the F NMR spectrum. The signals
The reaction of potassium cis- and trans-hex-1-
enyltrifluoroborate with 27 % HFaq.
3 7
F OCFϭCFH were not observed, probably caused by the low
.
The borate
4 9 3
K [cis- and trans-C H CHϭCHBF ] (300 mg,
1
9
K [cis-C
3
F
7
OCFϭCFBF
3
]. F NMR (48 % HFaq.):
CF ,OCF CF CF ) 7 Hz, 3F, OCF
CF
), Ϫ99.45 (s, 1F, F ), Ϫ128.431 (s, 2F,
), Ϫ141.22 (q, J(F,B) 36 Hz, BF ), Ϫ170.37 (s, 1F, F ).
4
1.58 mmol) was suspended in 27 % HFaq. (2.5 ml) and benzene
δ ϭ Ϫ80.35 (t, J(OCF
Ϫ84.76 (m, 2F, OCF CF
OCF CF CF
2
CF
2
3
2
2
3
2 2 3
CF CF ),
2
(1 ml) and stirred at 20 °C for 1 h. The organic extract contained
2
2
3
1
1
1
1,2
2
2
3
3
hex-1-ene [ H NMR: δ ϭ 5.84 (1H, H ), 5.09 and 5.03 (2H, H ),
2
3
4
5
6
.04 (2H, H ), 1.35 (4H, H and H ) and 0.92 (3H, H )] (quantita-
K [trans-C
3
F
7
OCFϭCFBF
3
]. 19F NMR (48 % HFaq.):
,OCF CF CF ) 7.5 Hz, 3F, OCF
CF CF ,OCF
), Ϫ124.07 (dtq, J(F ,F ) 118 Hz, J(F ,BF
4
tive yield).
δ ϭ Ϫ80.40 (t, J(OCF
2
CF
CF
CF
F, F ), Ϫ128.43 (s, 2F, OCF
2
CF
3
2
2
3
2
CF
CF
) 9 Hz,
), Ϫ141.22 (q, J(F,B) 36 Hz, BF ),
2
CF
3
),
3
)
4
2
3
Ϫ83.77 (dqt, J(OCF
2
2
CF
3
,F ) 14.3 Hz, J(OCF
2
2
3
3
2
2
CF
3
2
1
2
2
1
.5 Hz, 2F, OCF
2
CF
2
3
3
2
1
2
CF
2
CF
3
3
The reactions of potassium phenyltrifluoroborate with
acids
1
Ϫ177.68 (d, 1F, F ).
The solution of borate K [C
6 5 3
H BF ] 17 (321 mg, 1.74 mmol) in
The reactions of potassium
pentafluorophenyltrifluoroborate with acids
27 % HFaq. (3 ml) was stirred at 20 °C. The observed molar ratio
1
9
19
6 5 3 4
of K [C H BF ] [ F NMR: δ ϭ Ϫ138.69, br] and K [BF ] [ F
NMR: δ ϭ Ϫ150.67] changed from 7.7 : 1 (0.5 h) to 1.6 : 1 (6 h)
and after 48 h the resonance of borate 17 disappeared ( F NMR,
in 27 % HFaq.).
The suspension of K [C
CF CO H (1 ml) was stirred at 20 °C for 26 h. No F resonances
of borate 13 and C H 14 were detected in the solution phase.
The same result was obtained after stirring a suspension of borate
3 in 100 % CF CO H at 60 Ϫ 70 °C for 5 h.
6
F
5
BF
3
] (70 mg, 0.25 mmol) in 100 %
19
1
9
3
2
6 5
F
The borate K [C
6
H
5
BF
3
] (300 mg, 1.63 mmol) was stirred with
(1 ml) at 50 °C for 2 h. After cooling
to 20 °C the F NMR spectrum of the acidic phase showed the
resonances of K [BF ] (Ϫ150 ppm), aqueous HF (Ϫ166 ppm) and
no signal of borate 17. After washing with aq. Na [CO ] and dry-
ing, the CCl extract displayed the presence of benzene (ca. 45 %
2
7 % HFaq. (2.5 ml) and CCl
4
1
3
2
1
9
6 5
A solution of K [C F BF
3
] (56 mg, 0.20 mmol) in 40 % HFaq.
4
(
(
0.4 ml) was kept at 20 °C. After 4 days it showed no reaction
F NMR).
2
3
19
4
1
yield, H NMR).
A solution of K [C
6
F
5
BF
3
] (38 mg, 0.13 mmol) in 40 % HFaq.
19
(0.3 ml) was kept at 80 °C for 0.5 h. The F NMR spectrum
The borate K [C
6
5 3
H BF ] (353 mg, 1.91 mmol) was suspended in
Ϫ
showed the signals of the starting borate 13, [BF
4
]
and HFaq.
1
00 % HOAc (3 ml) and stirred at 20 °C for 60 h. The solid was
(
Ϫ166.40 ppm) in a molar ratio of 90 : 10. When this solution was
filtered off, washed with ether and dried to yield 280 mg of borate
Ϫ
Ϫ
maintained at 90Ϫ95 °C, the ratio [C
6 5
F BF
3
] /[BF
4
]
increased to
19
1
1
7 [ F NMR (DMF): δ ϭ Ϫ140.30 (q, J(F,B) 50 Hz], with traces
5
7 : 43 (50 minutes) and 16 : 84 (3 h). After 6 h the resonances of
(
1
Ͻ 2 %) of K [BF ] [δ ϭ Ϫ149.42]. The filtrate contained borate
7 (47 mg) ( F NMR). The total recovery of borate 17 was
4
Ϫ
the anion [C
C F H ( F NMR).
6
F
5
BF
3
]
disappeared parallel to the formation of
19
19
6 5
3
27 mg (93 %).
The borate K [C BF ] (40 mg, 0.14 mmol) was suspended in pre-
6
F
5
3
cooled aHF (0.2 ml) at Ϫ78 °C. The suspension was warmed to
°C for 1 minute and a solution was formed. After cooling to
Ϫ40 °C the F NMR spectrum showed resonances at Ϫ136.20
The reactions of potassium alkyltrifluoroborate with
acids
0
19
2
6
4
3
5
(
F ,F ), Ϫ155.28 (F ), Ϫ163.22 (F ,F ), Ϫ131.88 (br, BF) with rela-
tive intensities of 2 : 1 : 2 : 2. At Ϫ10 °C the B-F signal became
too broad for observation while the resonances of the C group
were not changed. After 18 h at 20 °C the quantitative formation
8 3
The borate K [C H17BF ] (378 mg, 1.71 mmol) was stirred with
2
7 % HFaq. (2 ml) at 65 Ϫ 70 °C for 2.5 h. The clear solution was
6 5
F
cooled to 20 °C and the precipitate was filtered off, washed in se-
quence with water and ether and dried to give a white solid
19
of C
The borate K [C
cold (Ϫ30 °C) solution of K [HF
0.3 ml). The 19F NMR spectrum (Ϫ30 °C) showed no difference
to the spectrum of K [C BF ] in aHF (see above). However,
6
F
5
H and K [BF
4
] (1 : 1) was found ( F NMR).
] (105 mg, 0.38 mmol) was dissolved in the
] (38 mg, 0.48 mmol) in aHF
(
205 mg), which consisted of K [C
8
H
17BF
3
] (0.53 mmol) and K
1
9
6
F
5
BF
3
[BF
4
] (0.70 mmol) ( F NMR). The filtrate was neutralized with
1
9
2
3
solid K [HCO ] and extracted with DMF. The F NMR spectrum
(
8 3 4
showed the presence of K [C H17BF ] (0.44 mmol) and K [BF ]
6
F
5
3
(0.04 mmol).
Z. Anorg. Allg. Chem. 2002, 628, 883Ϫ890
889

V. V. Bardin, S. G. Idemskaya, H.-J. Frohn
The similar reaction of K [C
8
H
17BF
3
] (317 mg, 1.44 mmol) with
References
27 % HFaq. (2 ml) at 65 Ϫ 70 °C for 2 h resulted in K [C
8
H
17BF
3
]
[1] H.-J. Frohn, V. V. Bardin, Z. Anorg. Allg. Chem. submitted
for publication.
4
(0.90 mmol) and K [BF ] (0.54 mmol).
[2] H.-J. Frohn, V. V. Bardin, Z. Anorg. Allg. Chem. 2001, 627, 15.
The borates K [C
6
H
5
BF
3
] (199 mg, 1.08 mmol) and K [C
4
H
9
BF
3
]
[3] H.-J. Frohn, H. Franke, P. Fritzen, V. V. Bardin, J. Organomet.
Chem. 2000, 598, 127.
[4] H.-J. Frohn, V. V. Bardin, Z. Anorg. Allg. Chem. 2001, 627,
2499.
[5] H.-J. Frohn, V. V. Bardin, J. Organomet. Chem. 2001, 631, 54.
[6] G. A. Molander, T. Ito, Org. Lett. 2001, 3, 393.
[7] S. Darses, G. Michaud, J.-P. Genet, Eur. J. Org. Chem. 1999,
(
184 mg, 1.12 mmol) were stirred with 27 % HFaq. (1.5 ml) at 70 °C
for 40 minutes. After cooling to 20 °C the reaction mixture was
neutralized with solid K [HCO ] and extracted with DMF (2 ml).
The 19F NMR spectrum of the extract showed the resonances of
K [C BF ] (Ϫ137.52 ppm), K [BF ] (Ϫ149.69 ppm), aq. KF
Ϫ122.88 ppm) but no signal of K [C BF ].
3
4
H
9
3
4
(
6
H
5
3
1
875.
[
[
8] N. A. Petasis, A. K. Yudin, I. A. Zavialov, G. K. S. Prakash,
G. A. Olah, Synlett 1997, 606.
9] Methoden der organischen Chemie (Houben-Weyl). Bd 13/3b.
Organobor-Verbindungen II. Thieme, Stuttgart, 1983.
Cold (Ϫ20 °C) aHF (1 ml) was added to the pre-cooled (Ϫ25 °C)
borate 19 (145 mg, 0.66 mmol) under stirring. Immediately an up-
per hydrocarbon phase was formed. The reaction mixture was
stirred at 20 °C for 20 minutes and extracted with benzene. The
extract was treated with NaF. The H NMR spectrum showed the
quantitative formation of octane.
[
[
10] H.-J. Frohn, V. V. Bardin, Organometallics 2001, 20, 4750.
11] C. H. Rochester, Acidity Functions, Academic Press, New
York, 1970.
1
[12] T. A. O’Donnell, Superacids and Acidic Melts as Inorganic
We gratefully acknowledge financial support by the Deutsche For-
schungsgemeinschaft, the Russian Foundation for Basic Research,
and the Fonds der Chemischen Industrie.
Chemical Reaction Media. VCH Publ., New York, 1993, p.14.
[13] E. Vedejs, R. W. Chapman, S. C. Fields, S. Lin, M. R.
Schrimpf, J. Org. Chem. 1995, 60, 3020.
890
Z. Anorg. Allg. Chem. 2002, 628, 883Ϫ890