J.A.P. Sprenger et al.
JournalofFluorineChemistry206(2018)54–60
Scheme 8. One-pot synthesis of perfluoroalkyltrifluoroborates starting
from perfluoroalkyl iodides.
passed trough the reaction mixture for one additional min. The
suspension was warmed up to room temperature and all volatiles
were removed in vacuum. The residue was suspended in acetone
(100 mL) and treated with potassium carbonate (∼12 g). The
precipitate that had formed was filtered off and the filtrate was
evaporated in vacuum. The solid obtained was washed with CH2Cl2
and the colorless K[C2F5BF3] was dried in vacuum. Yield: 26% (1.6 g,
7.1 mmol; calculated based on C2F5I).
3.2.3. Preparation of potassium heptafluoropropyltrifluoroborate
K
[C3F7BF3]
Magnesium turnings (260 mg, 10.7 mmol) and trimethoxyborane B
(OCH3)3 (1.5 mL, 13.5 mmol) were placed into a glass flask and sus-
pended in dry THF (20 mL). Heptafluoropropyl iodide C3F7I (1.0 mL,
2.0 g, 6.8 mmol) was added to this mixture at −78 °C in an Ar atmo-
sphere. The reaction mixture was slowly warmed up to room tem-
perature and was stirred overnight. The resulting suspension was eva-
porated in vacuum and the residue was treated with KHF2 (4.0 g,
51 mmol) in aqueous HCl (25 mL, 37%). After 2 h, additional KHF2
(0.85 g, 10.9 mmol) was added and the reaction mixture was stirred
overnight. After neutralization with potassium carbonate the reaction
mixture was extracted with acetonitrile (100 mL). Insoluble material
was filtered off and the volume of the filtrate was reduced to a few
milliliters by evaporation in vacuum. K[C3F7BF3] was precipitated by
addition of dichloromethane (100 mL), filtered off and dried in vacuum.
Yield: 46% (850 mg, 3.08 mmol; calculated based on heptafluoropropyl
iodide). 11B NMR (64 MHz, acetone-d6): δ −0.53 (m). 19F NMR
Fig. 1. A formula unit of [Cu(bpy)3][C2F5BF3]2 in the crystal (displacement ellipsoids are
depicted at the 50% probability level and H atoms are omitted for clarity). Selected in-
teratomic distances [pm] and angles [°] of the [C2F5BF3]− anion: B1-C1 163.0(4), C1-C2
152.2(3), B1-F1 138.6(3), B1-F2 140.3(3), B1-F3 139.0(3), C1-F4 137.9(2), C1–F5
137.9(3), C2-F6 133.0(3), C2-F7 134.1(3), C2-F8 132.5(3), B1-C1-C2 118.6(2) and the
[Cu(bpy)3]2+ cation: Cu1⋯N1 202.6(2), Cu1⋯N2 229.3(2), Cu1⋯N3 204.7(2),
N1⋯Cu1⋯N3′ 165.56(7), N2⋯Cu1⋯N2′ 179.56(6), N1⋯Cu1⋯N1′ 80.13(7),
N2⋯Cu1⋯N3 76.02(6).
dimethoxyethane (20 mL). Gaseous HCl was passed through the
reaction mixture at room temperature within 15 min. All volatiles
were removed in vacuum and the residue was extracted with
acetonitrile (25 mL) and filtered. After evaporation of the acetonitrile
in vacuum, the K[C2F5BF3] was dried in fine vacuum. Yield: 87%
(150 mg, 0.66 mmol).
5
4
(188 MHz, acetone-d6): δ −81.62 (tq, JF,F = 2.6 Hz, JF,F = 9.3 Hz,
4
CF3, 3F), −128.75 (q, JF,F = 5.2 Hz, CF2, 2F), −135.02 (m, CF2, 2F),
1
−154.00 (q, JB,F = 40.2 Hz, BF3, 3F).
3.2.2.5. Method 5. Magnesium turnings (600 mg, 24.7 mmol) and
trimethoxyborane B(OCH3)3 (2.7 mL, 24.4 mmol) were placed into a
glass flask and dry THF (40 mL) was added. Pentafluoroethyl iodide
C2F5I (4.00 g, 16.3 mmol) was added to this mixture at −78 °C. The
reaction mixture was warmed up to room temperature in an Ar
atmosphere and was stirred for 12 h. The resulting suspension was
evaporated in vacuum and the residue was treated with a solution of
KHF2 (27.0 g, 346 mmol) in aqueous HCl (37%, 100 mL) at 0 °C. The
reaction mixture was warmed up to room temperature and all volatiles
were removed in vacuum. The solid remainder was extracted with
acetonitrile (150 mL), neutralized with potassium carbonate (16 g) and
filtered. The filtrate was evaporated in vacuum and the solid residue
was washed with dichloromethane. The colorless K[C2F5BF3] was dried
in vacuum. Yield: 71% (2.60 g, 11.5 mmol; calculated based on C2F5I).
Additional K[C2F5BF3] precipitated from the CH2Cl2 solution upon
standing. Yield of the second crop: 15% (0.55 g, 2.43 mmol).
3.2.4. Preparation of potassium nonafluorobutyltrifluoroborate
[C4F9BF3]
K
Magnesium turnings (0.53 g, 21.7 mmol) and B(OCH3)3 (2.4 mL,
21.7 mmol) were placed into a glass flask and suspended in dry THF
(50 mL). Nonafluorobutyl iodide C4F9I (2.5 mL, 5.0 g, 14.5 mmol) was
added to this mixture at −78 °C under an inert atmosphere (Ar). The
reaction mixture was slowly warmed up to room temperature and was
stirred overnight. The resulting suspension was evaporated in vacuum
and the residue was treated with KHF2 (14.5 g, 186 mmol) in aqueous
HCl (75 mL, 37%). The reaction mixture was stirred for 5 h and eva-
porated in vacuum. The residue was treated with K2CO3 (20 g) in
acetone (100 mL) and stirred for 1–2 h. The suspension was filtered and
the filtrate was evaporated at a rotary evaporator. The solid K[C4F9BF3]
was washed with CH2Cl2 and dried in vacuum. Yield: 43% (2.03 g,
6.23 mmol; calculated based on nonafluorobutyl iodide). 11B NMR
(64 MHz, acetone-d6): δ −0.68 (m). 19F NMR (188 MHz, acetone-d6): δ
−82.02 (tt, 5JF,F = 3.85 Hz, 4JF,F = 9.8 Hz, CF3, 3F), −125.01 (m, CF2,
2F), −126.97 (m, CF2, 2F), −134.39 (m, CF2, 2F), −153.77 (q,
1JB,F = 40.6 Hz, BF3, 3F).
3.2.2.6. Method 6. Magnesium turnings (1.0 g, 42 mmol) and
trimethoxyborane B(OCH3)3 (4.6 mL, 40.9 mmol) were placed into a
glass flask and suspended in dry THF (35 mL). Pentafluoroethyl iodide
C2F5I (6.69 g, 27.3 mmol) was added to this mixture at −78 °C. The
reaction mixture was slowly warmed up to room temperature overnight
in an Ar atmosphere. The resulting suspension was evaporated in
vacuum and the residue was treated with KHF2 (14.5 g, 186 mmol) in
1,2-dimetoxyethane (100 mL) and cooled to 0 °C. Gaseous HCl was
passed through the reaction mixture for 10 min. Then an additional
quantity of KHF2 (2.0 g, 26 mmol) was added and gaseous HCl was
3.2.5. One-pot synthesis of 1-ethyl-3-methylimidazolium
pentafluoroethyltrifluoroborate EMIM[C2F5BF3]
3.2.5.1. Method 1. K[C2F5B(OCH3)3] (0.50 g, 1.90 mmol) and KHF2
(0.75 g, 9.60 mmol) were placed into a glass flask and suspended in
1-ethyl-3-methylimidazolium hydrogensulfate EMIM[HSO4] (3 mL).
Concentrated H2SO4 (1 mL) was added to this suspension and the
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