| 40% |
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This reaction was performed according to the general procedure. To Iodopentafluorobenzene (153.2 mg, 0.521 mmol) in diethylether (5.0 mL), ft-BuLi (0.33 mL, 0.541 mmol, 1.6 M soln. in hexanes) was added. The lithiated product was transferred to a flask containing A (100.0 mg, 0.237 mmol) in diethy- lether. The crude product thus obtained after work-up was purified by flash column chromatography using silica gel (eluent: Hexane/EtOAc = 5/1) to obtain off-white solid. The solid was further recrystallized from a mixture of ether and pentane to obtain 3 as white solid. Yield = 66 mg, 40%. IR (KBr): vmax 3414, 2923, 2853, 1738, 1637, 1610, 1509, 1462, 1477, 1365, 1309, 1263, 1073, 967, 906, 885, 812, 785, 757, 732, 629, 466 cm"1; 1H NMR (500 MHz, CDC13, 298 K): delta = 6.83 (d, J= 7.5 Hz, 1H), 7.29 (td, J= 6.5, 1.5 Hz, 1H), 7.37 (t, J = 7.0 Hz, 2H), 7.78 (d, J= 7.5 Hz, 1H), 8.04 (d, J= 8.0 Hz, 1H), 8.12 (td, J= 8.0, 1.5 Hz, 1H), 8.25 (d, J = 8.0 Hz, 1H); 13C{1H} NMR (125 MHz, CDC13, 298 K): delta = 120.8, 124.3, 125.2, 127.8, 132.3, 133.8, 137.5 (dm, ^ = 251.0 Hz), 138.1 (dm, ^ = 251.0 Hz), 139.5 (dm, ^ = 251.0 Hz), 141.8, 144.1 (dm, C-F = 232.0 Hz), 145.1, 146.5 (dm, 1JC-F = 232.0 Hz), 149.3, 158.0, 165.8, 166.7, (note : resonances for 2C submerged in baseline); 19F NMR ( 470 MHz, CDCI3, 298 K): delta = -122.2 (m, 2F, o-C6F5), -122.3 (m, 2F, o-C6F5), -157.8 (t, J = 20.2 Hz, 1F, ^-C6F5), -158.7 (t, J = 20.2 Hz, IF, ^-C6F5), -161.5 (t, J = 19.2 Hz, 2F, m-C6F5), - 162.5 (t, J= 19.7 Hz, 2F, w-C6F5); elemental analysis (%) calc. for: C24HnAuFi0N: C, 41.16; H, 1.58; N, 2.00; Found: C, 41.86; H, 2.00; N, 1.97. General procedure for the synthesis of cyclometalated Au (III) complexes (2-8): n-BuLi (0.52 mmol, 1.6 M in hexanes) was added via syringe to a cooled (-78 C) solution of the aryl halide (0.50 mmol) in dry diethylether under nitrogen atmosphere and stirred for 20 minutes at that temperature. It was then transferred via cannula into a flask containing an diethylether suspension of cycloaurated Au(III)dichloride (0.22 mmol) precooled at -78 C. This temperature was maintained for 20 min and then the mixture was allowed to warm to RT and stirred further for 1 h. (Note: At this stage the reaction mixture turns dark (violet col- ouration), more in the case of non-fluorinated analogues indicating partial decomposition of the product to metallic gold). TLC examination (EtOAc/Hexane = 1/5) of the reaction mixture at this stage usually showed two major spots, the first (Rf ~ 0.7) corresponding to the homocoupled diaryl and the second being the desired organometallic product (Rf ~ 0.4) which also gets faintly illuminated in UV lamp longwave (365 nm). The reaction was quenched by addition of water (5 mL) followed by extraction with ethyl acetate/dichloromethane. After separation, the organic layer was dried over MgS04 and concentrated in vacuo to obtain the crude product. Purification on a short silica gel column (eluent: EtOAc and hexane mixture) was adopted to obtain analytically pure products. Some derivatives were prepared with modifications in the general procedure and are described individually. |
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