Fluoroalkylation of cobalt complexes: selective reactions at the metal or the cyclopentadienyl ring

Reactions of [Co(η5-C5H5)(CO)2] with perfluoro-n-propyl iodide proceeds by selective fluoroalkylation at the metal center to give [Co(η5-C5H5)(CO)(RF)] (3; RF = CF2CF2CF3). Treatment of 3 with excess PMe3 affords cationic fluoroalkyl complex [Co(η5-C5H5)(PMe3)2(RF)]+ I− (4; RF = CF2CF2CF3), which does not react further. The molecular structure of 4 has been determined by single-crystal X-ray diffraction studies. Complex 4 co-crystallizes with two water molecules in the space group P1, Z = 2, a = 7.9001(5)Å, b = 10.38(1)åc = 14.758Å, α = 85.48(1)°, β = 83.630(10)°, γ = 77.02(7)° at T = 298 K. In contrast, reaction of [Co(η5-C5H5)(PMe3)2] with perfluoro-n-propyl iodide proceeds with completely different selectivity to afford the ring-exo-fluoroalkylated complex [Co(η4-C5H5RF)(PMe3)2I] (5; RF = CF2CF2CF3). Possible mechanisms for these reactions are discussed.