Polyfluoroorganoboron-Oxygen Compounds
1691
Syn th esis of Potassium Difluorobis(2,3,5,6-tetrafluoroph en yl)borate 4b-K
(2,3,5,6-Tetrafluorophenyl)lithium was prepared from 1,2,4,5-tetrafluorobenzene (9.0 g, 60 m m ol)
an d 2.5 M BuLi in h exan es (20 m l, 50 m m ol) in eth er (100 m l) at –78 °C. After an addition
of B(OMe)3 (5.7 g, 54.9 m m ol) an d stirrin g at –70 °C for 1 h , DME (25 m l) was added
dropwise. Th e solution was kept at –70 °C for 1 h an d left stan din g at 20 °C over a period of
10 h . Th e reaction m ixture was worked up with a solution of KHF2 (16 g, 0.2 m ol) in water
(100 m l) acidified with 48% HF (10 m l), an d an im purity of K[(2,3,5,6-C6HF4)BF3] was re-
m oved with aqueous HF at 60 °C as described above. Evaporation of th e aceton itrile extract
un der reduced pressure an d dryin g th e residue in a vacuum desiccator over P4O10 overn igh t
gave pure salt 4b-K (6.0 g, 62%).
1H NMR (300.13 MHz, CD3CN): 6.97 tt, 1 H, 3J(H-4,F-3;H-4,F-5) = 10, 4J(H-4,F-2;H-4,F-6) =
7 (H-4). 11B NMR (96.29 MHz, CD3CN): 4.33 1 B, 1J(BF) = 63. 13C{19F} NMR (75.47 MHz,
CD3CN): 104.0 m , 1 C, J(C-4,H-4) = 168.0 (C-4); 130.0, 1 C (C-1); 146.6, 2 C (C-2, C-6);
148.9, 2 C (C-3,5). For C12H2BF10K (386.04) calculated: 37.34% C, 0.52% H, 49.21% F;
foun d: 38.09% C, 0.83% H, 49.40% F.
Syn th esis of Potassium Difluorobis(2,3,4,6-tetrafluoroph en yl)borate 4c-K
(2,3,4,6-Tetrafluorophenyl)lithium was prepared from 1,2,3,5-tetrafluorobenzene (9.0 g, 60 m m ol)
an d 2.5 M BuLi in h exan es (20 m l, 50 m m ol) in eth er (100 m l) at –78 °C. After addition of
B(OMe)3 (5.7 g, 54.9 m m ol) an d stirrin g at –70 °C for 1 h , DME (25 m l) was added dropwise.
Th e solution was kept at –70 °C for 1 h an d left stan din g at 20 °C overn igh t. Th e reaction
m ixture was worked up with a solution of KHF2 (16 g, 0.2 m ol) in water (100 m l) acidified
with 48% HF (10 m l) an d an im purity of K[2,3,4,6-C6HF4BF3] was rem oved with aqueous HF
at 60 °C as described above. Pure salt 4c-K (7.18 g, 74%) was obtain ed after evaporation of
aceton itrile extract un der reduced pressure an d dryin g in vacuum over P4O10 overn igh t.
1H NMR (300.13 MHz, CD3CN): 6.64 dddd, 3J(H-5,F-4) = 11, 3J(H-5,F-6) = 9, 4J(H-5,F-3) =
6, 5J(H-5,F-2) = 3 (H-5). 11B NMR (96.29 MHz, CD3CN): 4.45 t, 1 B, 1J(BF) = 66. 13C{19F} NMR
(75.47 MHz, CD3CN): 100.8, 1 C, 1J(C-5,H-5) = 167 (C-5); 122.7, 1 C (C-1); 137.7, 1 C (C-6);
150.0, 1 C (C-2); 154.3, 1 C (C-3); 160.6, 1 C (C-4). For C12H2BF10K (386.04) calculated:
37.34% C, 0.52% H, 49.21% F; foun d: 38.41% C, 0.90% H, 49.29% F.
We gratefully acknowledge financial support by the Deutsche Forschungsgemeinschaft and the
Fonds der Chemischen Industrie.
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Collect. Czech. Chem. Commun. 2008, Vol. 73, No. 12, pp. 1681–1692