Transition metal cyclopentadienyl complexes bearing perfluoro-4-tolyl substituents

Depending on the ratio of starting materials and the reaction conditions, perfluorotoluene (C6F5CF3) reacts with sodium cyclopentadienide (NaCp; Cp = C5H5) and excess sodium hydride to afford, after acidic aqueous workup, moderate to high yields of mono-, bis-, tris-, and tetrakis(perfluoro-4-tolyl)cyclopentadiene (1, 2, 3, and 4, respectively). Treatment of 1 with excess NaH in THF afforded sodium (perfluoro-4-tolyl)cyclopentadienide (5) in 90% yield. Reaction of FeBr2 with 2 equiv. of 5 afforded a 68% yield of (η5-C5H4C7F7)2Fe (6). Reaction of ZrCl4(THF)2 with 2 equiv. of 5 afforded a 58% yield of (η5-C7F7C5H4)2ZrCl2 (7). Reaction of Mn(CO)5Br with 5 afforded a 74% yield of (η5-C7F7C5H4)Mn(CO)3 (8). Treatment of 3b with NaH and then with Mn(CO)5Br in DME afforded a 26% yield of [η5-1,2,4-(C7F7)3C5H2]Mn(CO)3 (9). Treatment of 3b with NaH and then with FeBr2 in DME afforded a trace yield of [η5-1,2,4-(C7F7)3C5H2]2Fe (10), which was not fully characterized. Dienes 2a, 3a, and 3b and metal complexes 7, 8, and 9 were structurally characterized by single-crystal X-ray diffraction. Infrared spectroscopic analysis of the substituted CpMn(CO)3 complexes showed a linear increase of 5 cm−1 in the A-symmteric stretching frequency for each C7F7 substituent, compared to the analogous value of 4 cm−1 reported earlier for each pentafluorophenyl (C6F5) substituent. Solution voltammetric analysis of the substituted ferrocene 6 revealed a shift in the E1/2 of 465 mV relative to ferrocene, compared to the analogous value of about 340 mV for 1,1′-bis(pentafluorophenyl)ferrocene.