Compound 2

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InChIKey UNAIRZJJIVMAKZ-UHFFFAOYSA-N

Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.

Compound 3 (240 mg, 0.56 mmol) was dried at 100^oC over P₂O₅ for 48 h in a 100-mL Schlenk tube connected to the house vacuum line. It was then suspended in 30 mL of dry THF and cooled down to −78^oC under argon. 2.7 eq. tBuOK (1.5 mmol, 1.5 mL, 1 M in THF) was then added and the mixture was stirred for 30 min at this temperature. The cooling bath was removed and when the mixture was warmed to 0–5^oC it became yellow. Then anhydrous FeBr₂ (43 mg, 0.2 mmol) dissolved in 15 mL of THF was added drop-wise with a syringe. The reaction mixture was then further stirred in the dark overnight and the solid was collected using a glass sinter (porosity #4), and washed twice with dry THF (20 mL). The solid was re-dissolved in a small amount of aqueous HBr solution (3 mmol, 10 mL, 0.3 M) and was re-precipitated by the addition of an excess of solid KPF₆. The formed precipitate was collected by filtration using a glass sinter (porosity #4), washed generously with diethyl ether (ca. 50 mL), and re-extracted in 10 mL of CH₃CN. The mixture was filtered using a glass sinter (porosity #4) and the filtrate was subsequently evaporated in vacuo. The crude product was dispersed in dry dichloromethane (10 mL) and was then treated with solid 18-crown-6 (180 mg, 0.68 mmol). The residual solid material was collected on a glass sinter (porosity #4) and then washed generously with dichloromethane (ca. 50 mL). The solid material was dissolved in a minimum amount of CH₃CN (60)/toluene (40). The filtered solution was applied on a BioBeads S-X1 size exclusion chromatography column and the product was eluted using CH₃CN (60)/toluene (40) as the eluent. This chromatography was repeated twice. The fraction containing the product was evaporated to dryness in vacuo and the solid was dissolved in a minimum amount of CH₃CN, the resulted solution of which was added dropwise to a vigorously stirred bulk of diethyl ether (ca. 25 mL) for precipitation. The precipitates were then collected using a glass sinter (porosity #4) and dried in vacuo to give the product as a pink red solid (18 mg, yield 10% based on FeBr₂), ¹H NMR (400 MHz, CD₃CN) δ (ppm) 8.29 (s, 4H), 8.14 (d, J=2 Hz, 4H), 7.01 (d, J=2 Hz, 4H), 2.50 (s, 12H). ¹³C NMR (100.3 MHz, CD₃CN) δ (ppm) 198.71, 164.24, 154.24, 139.56, 126.82, 116.80, 104.80, 34.63. IR (neat) cm⁻¹ 3143, 1720 (C=O), 1624, 1578, 1546, 1482, 1442, 1405, 1346, 1270, 1237, 1113, 1084, 1060, 1021, 978, 841, 792, 771, 740, 688, 558, 500. ESI–HRMS: calc. for [2–(PF₆)]⁺ 767.1130, found 767.1129. Elemental analysis: calc. for 2 (C₂₈H₂₆F₁₂FeN₁₀O₄P₂) C, 36.86; H, 2.87; N, 15.35; found C, 36.61; H, 2.91; N, 15.27.