Pentafluorocyclopentadienyl

In view of the ubiquity of the 5-cyclopentadienyl ligand in organometallic chemistry, and the reports in the literature of perchlorocyclopentadienyl analogues (56), it is both curious and unfortunate that attempts (85) to prepare complexes of the /5-pentafluorocyclopentadienyl ligand from the known C5F j anion (87,88) have failed. 

Cyclopentadienyl radicals are likely to experience Jahn-Teller-type distortion from planarity. The pentafluorocyclopentadienyl radical C5F 5214 was obtained by photolytic dissociation of the chlorine atom of C5F5C1. The fluorine hyperfine structure (A1S0 = 16 G)... 

Stavber and Zupan reacted this reagent with activated aromatics such as 1,2,4,5-tetram-ethylbenzene, eventually isolating a monofluoro derivative from quite a complex mixture (equation 183)312. Seppelt and coworkers used it in combination with F2 for the first preparation of another aromatic system, the pentafluorocyclopentadienyl anion (equation 184)313. 

Iron, Ruthenium, and Osmium - In this section of work Fp = Fe(CO)2Cp - and Rp = Ru(CO)2Cp is used throughout. The inclusion compounds of aromatic ruthenium complexes, e.g. (Bn)Ru(Cp) PF in a-cyclodextrin has been investigated and die mentioned example has been crystallographically characterised. Two transition m boryl complexes, FpB(OCeH40) and FpBPh2 have been reported the reaction of the former complex with Et2NH results in the formation of FpH and die aminoborane. Gas phase and solution studies have been carried out on the first pentafluorocyclopentadienyl complex ICp Rufn-CsFs)]. The redox chemistry of this complex is not unusual in any way. ... 

This successful synthesis of the pentafluorocyclopentadienyl ligand, albeit by an unorthodox route, demonstrates clearly that complexes of this ligand can be prepared, and that they are likely to be thermally stable, thus re-opening the synthetic challenge to develop suitable general syntheses of complexes of this ligand. 

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