ELECTROCHEMICAL STUDIES OF ORGANOMETALLIC COMPLEXES WITH TETRA-N-BUTYLAMMONIUM TETRAKIS[3,5-BIS(TRIFLUOROMETHYL)PHENYL]BORATE AS THE ELECTROLYTE - X-RAY CRYSTAL-STRUCTURE OF [C-5(CF3)(CH3)(4)]FE(C5H5)

The tetra-n-butylammonium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (TBA(+)TFPB(-)) electrolyte/methylene chloride solvent system improves the electrochemical reversibility of pentamethylcyclopentadienyl (Cp*) ruthenocenes, Cp*RuCp' (Cp' = fluorenyl, indenyl, cyclopentadienyl (Cp), acetylcyclopentadienyl, pentachlorocyclbpentadienyl), as indicated by i(p,c)/i(p,a) ratios of 0.79-1.0 as determined by cyclic voltammetry. The quasi-reversible potentials (E degrees') of the Cp*RuCp' complexes and the complete series of group 9 Cp(2)M and Cp*(2)M complexes (M = Fe, Ru, Os) are also reported in TBA(+)TFPB(-)/CH2Cl2. In addition, a study of the E degrees' values of group 9 complexes containing the (trifluoromethyl)tetramethylcyclopentadienyl (Cp') ligand indicate that the Cp' complexes are slightly (0.06-0.08 V per Cp(double dagger)) more difficult to oxidize than the cyclopentadienyl (Cp) derivatives. The structure of [C-5(CF3)(CH3)(4)]Fe(C5H5) was determined at -101 degrees C by a single-crystal X-ray diffraction study. The structure shows eclipsed Cp(double dagger) and Cp rings, and the iron to Cp' centroid distance (1.643 Angstrom) is slightly shorter than the iron to Cp centroid distance (1.651 Angstrom); otherwise, no extreme differences in the coordination of the Cp' and Cp rings are noted. An infrared spectroelectrochemistry study of trans-[Cp(double dagger)Fe(CO)(2)](2) shows that it is electrochemically oxidized to trans-[Cp(double dagger)Fe(CO)(2)](+)(2) in TBA(+)TFPB(-)/CH2Cl2.