Table 1. Reactions of K2 1 with selected fluoro(hetero)arenes.
| Entry | Substrate | LiCl a | K2 1 b | Conditions | [BH(CN)3]– c | Major tricyanoborate anion(s) formed |
Isolated yield | |
| 1 | C6FH5 | Yes | <1 | 80 °C, 2 d | 25% | [1-{(NC)3B}-C6H5]– (B1) | Sole isomer | 45% |
| 2 | 1,2-C6F2H4 | Yes | <1 | r.t., 16 h | 9% | [1-{(NC)3B}-2-F-C6H4]– (B2a) | Sole isomer | 58% |
| 3 | 1,3-C6F2H4 | Yes | <1 | r.t., 3 d | <5% | [1-{(NC)3B}-3-F-C6H4]– (B2b) | Sole isomer | 70% |
| 4 | 1,4-C6F2H4 | Yes | <1 | 75 °C, 30 h | 28% | [1-{(NC)3B}-4-F-C6H4]– (B2c) + B2b (6 : 4 d ) e | 45% e | |
| 5 | 1,2,3-C6F3H3 | Yes | <1 | r.t., 3 d | <5% | [1-{(NC)3B}-2,3-F2-C6H3]– (B3a) + [1-{(NC)3B}-2,6-F2-C6H3]– (B3b) (4 : 1) | 66% | |
| 6 | 1,2,4-C6F3H3 | Yes | <1 | r.t., 2 h | <5% | [1-{(NC)3B}-2,5-F2-C6H3]– (B3c) | Sole isomer | 76% |
| 7 | 1,3,5-C6F3H3 | Yes | <1 | r.t., 16 h | <5% | [1-{(NC)3B}-3,5-F2-C6H3]– (B3d) | Sole isomer | 63% |
| 8 | 1,2,3,4-C6F4H2 | Yes | <1 | r.t., <1 h | <5% | [1-{(NC)3B}-2,3,6-F3-C6H2]– (B4a) | Sole isomer | 77% |
| 9 | 1,2,3,5-C6F4H2 | Yes | <1 | r.t., 2 h | <5% | [1-{(NC)3B}-2,3,5-F3-C6H2]– (B4b) | Sole isomer | 63% |
| 10 | 1,2,3,5-C6F4H2 | No | <1 | 75 °C, 30 h | 10% | B4b | 8% of other isomers | 51% |
| 11 | 1,2,4,5-C6F4H2 | Yes | <1 | r.t., 30 min | 30% | [1-{(NC)3B}-2,4,5-F3-C6H2]– (B4c) | Sole isomer | 50% |
| 12 | 1,2,4,5-C6F4H2 | Yes | 2 | r.t., 16 h | n.d. | [1,4-{(NC)3B}2-2,5-F2-C6H2]2– (B4d) | Sole isomer | 42% f |
| 13 | C6F5H | Yes | <1 | r.t., 10 min | 10% | [1-{(NC)3B}-2,3,5,6-F4-C6H]– (B5) | 6% of one other isomer | 62% |
| 14 | C6F5H | No | <1 | r.t., 2 d | 48% | B5 | 20% of other anions | 39% |
| 15 | C6F6 | No | <1 | 0 °C | — | [1-{(NC)3B}-C6F5]– (B6a)29 | Sole isomer | 67% (ref. 30) |
| 16 | C6F6 | No | 2.2 | Reflux, 20 h | — | [1,4-{(NC)3B}2-C6F4]2– (B6b) | Sole isomer | 74% |
| 17 | C5F5N | No | 0.33 | r.t., 12 h | — | [4-{(NC)3B}-C5F4N]– (Py1) g | Other isomer(s), Py2, Py3 | 81% h |
| 18 | C5F5N | No | 2 | r.t., 4 d | — | [2,4-{(NC)3B}2-C5F3N]2– (Py2) i | Other isomer(s), Py3 | 59% j |
| 19 | C5F5N | No | 3 | r.t., 4 d | — | [2,4,6-{(NC)3B}3-C5F2N]3– (Py3) | <10% Py1 and Py2 | 31% |
| 20 | C12F10 | No | 0.8 | r.t., 2 h | — | [4-{(NC)3B}-C12F9]– (BP1) | <20% of BP2 | 49% |
| 21 | C12F10 | No | 2.2 | 50 °C, 1 h | — | [4,4′-{(NC)3B}2-C12F8]2– (BP2) | Sole isomer | 90% |
| 22 | C10F8 | No | 0.5 | r.t., 3 d | — | [2-{(NC)3B}-C10F7]– (N1) | 8% of other isomers k | 55% |
| 23 | C10F8 | No | 2 | 60 °C, 16 h | — | [2,6-{(NC)3B}2-C10F6]2– (N2) | Mixture of N1, N2 and N3 l | 24% |
| 24 | F3C–C6F5 | No | <1 | r.t., 3 h | — | [1-F3C-4-{(NC)3B}-C6F4]– (B7) | Sole isomer | 68% |
| 25 | Me–C6F5 | No | <1 | 90 °C, 3 d | — | [1-Me-4-{(NC)3B}-C6F4]– (B8a) + [1-Me-3-{(NC)3B}-C6F4]– (B8b) (9 : 1) | n.d. | |
| 26 | 1-F3C-4-H-C6F4 | No | <1 | r.t., 2 h | 75% | Unidentified borate anions | n.d. | |
| 27 | 1-F3C-6-H-C6F4 | No | <1 | r.t., 4 d | 2% | [1-F3C-4-{(NC)3B}-2,3,5-F3-C6H]– (B9) | 7% of other isomers | 78% |
| 28 | MeO–C6F5 | No | <1 | 60 °C, 16 h | — | [1-MeO-4-{(NC)3B}-C6F4]– (B10a) + [1-MeO-3-{(NC)3B}-C6F4]– (B10b) (1 : 1) | 82% | |
| 29 | NC-C6F5 | No | <1 | r.t., <1 h | — | [1-NC-4-{(NC)3B}-C6F4]– (B11a) + [1-NC-2-{(NC)3B}-C6F4]– (B11b) + [B(CN)4]– (2.5 : 1.5 : 1) m | n.d. | |
| 30 | Cl–C6F5 | No | <1 | r.t., <1 h | — | [BCl(CN)3]–, [B2(CN)6]2–, … | n.d. | |
| 31 | O2N–C6F5 | No | <1 | r.t., 16 h | — | [B2(CN)6]2–, … | n.d. | |
aWhether LiCl was added to the reaction mixture.
bEquivalents of K2 1.
cThe percentage that was formed as a side product; [BH(CN)3]– was removed during the work-up.
dThe ratio B2c : B2b was 6 : 4 in the reaction mixture and 7 : 3 in the isolated material.
e11% of K[BH(CN)3].
f[Et3NH]+ salt.
gThe internal yield was 75% Py1, 16% Py2, 8% another isomer (probably [2-{(NC)3B}-C5F4N]–), and 1% Py3 and unknown tricyano(fluoropyridinyl)borate anions.
hPurity ca. 85% (11B/19F NMR); it contained 15% other tricyano(fluoropyridinyl)borates.
iThe internal yield (11B/19F NMR) was 60% Py2, 30% Py3, and 10% another tricyano(fluoropyridinyl)borate anion.
jPurity ca. 75% (11B/19F NMR); it contained 15% K3 Py3 and 10% another tricyano(fluoropyridinyl)borate.
k N2 : N3 = 1.0 : 0.8 (N3 = [2,7-{(NC)3B}2-C10F6]2–).
lThe ratio of the reaction mixture: N1 : N2 : N3 = 0.4 : 1.0 : 0.7; N2 is hardly soluble and was obtained as a pure K+ salt.
mK[B(CN)4] was mostly removed via fractional precipitation.