Carbon–fluorine activation by iron(I): organoiron ring transformation promoted by addition of tertiary phosphanes to a perfluorosulfanylvinyldiiron(I) complex

Abstract

The perfluorosulfanylvinyldiiron(I) complex [{Fe(CO)₃}₂{µ-C(SMe)(CF₃ )C(CF₂)}] 1 reacted with tertiary phosphanes [L = PPh₃ or P(OMe)₃] in dichloromethane or chloroform at 60 °C to give high yields of cycloferrathiapentadiene iron clusters. When the nucleophile was PPh₃, the salt 2 was obtained: formally, a fluoride-ion transfer between two molecules of 1 generates the anion [{Fe(CO)₃}₂{µ-C(CF₃ )C(CF₃)SMe}]^- and addition of PPh₃ at two separate sites produces the counter cation [(Ph₃P)(OC)₂Fe{µ-CFC(PPh₃ )C(CF₃)SMe}Fe(CO)₃]⁺. In contrast, with P(OMe)₃ the neutral derivative [{Fe(CO)₃}₂{µ-CFC[PO(OMe) ₂]C(CF₃)SMe}] 4 was formed. Thermally induced C–F bond activation is a feature of these reactions. All the reaction products have been characterized by elemental analysis and IR, ¹H, ¹⁹F, ³¹P and ¹³C NMR spectroscopy. The solid-state structure of [(Ph₃P)(OC)₂Fe{µ-CFC(PPh₃ )C(CF₃)SMe}Fe(CO)₃][{Fe(CO)₃ }₂{µ-C(CF₃)C(CF₃)SMe }] 2 has been established by single-crystal X-ray analysis. The Fe–Fe bond in the cation [2.716(2) Å] is appreciably longer than the corresponding bond in the anion [2.570(2) Å]. Possible routes to the formation of 2 and 4 have been investigated. The conversion of 1 into 4 has been shown to involve an intermediate 3 which has been fully characterized by ¹⁹F, ³¹P and ¹³C NMR spectroscopy.

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