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

Reaction of [Co(eta(5)-C5H5)(CO)(2)] with perfluoro-n-propyl iodide proceeds by selective fluoroalkylation at the metal center to give [Co(eta(5)-C5H5)(CO)(R-F)I] (3; R-F = CF2CF2CF3). Treatment of 3 with excess PMe3 affords cationic fluoroalkyl complex [Co(eta(5)-C5H5)(PMe3)(2)(R-F)(+) I- (4; R-F = 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 P (1) over bar, Z = 2, a = 7.9001(5)A, b=10.348(1)Angstrom, c=14.758 Angstrom, (alpha=85.48(1)degrees, beta=83.630(10)degrees, gamma=77.02(7)degrees at T=298K. In contrast, reaction of [Co(eta(5)-C5H5)(PMe3)(2)] with perfluoro-n-propyl iodide proceeds with completely different selectivity to afford the ring-exo-fluoroalkylated complex [Co(eta(4)-C5H5RF)(PMe3)(2)I] (5; R-F = CF2CF2CF3). Possible mechanisms for these reactions are discussed. (C) 1997 Elsevier Science S.A.