Preparation and Characterization of the Triflate Complex [Cp*(dppe)FeOSO2CF3]: A Convenient Access to Labile Five- and Six-Coordinate Iron(I) and Iron(II) Complexes

Treatment of the iron hydride [Cp*(dppe)FeH] (1) with methyl triflate (CH3OSO2CF3) yielded the iron triflate adduct [Cp*(dppe)FeOSO2CF3] (4, 85 %). In the solid state, the triflate is coordinated at the iron center as shown by XRD (d(Fe-O) = 2.118(4) angstrom) and IR spectroscopy (nu(SO) = 1305 cm(-1)). In solution, 4 is in equilibrium with the 16-electron species [Cp*(dppe)Fe]OSO2CF3 (5(OSO2CF3)), 4/5(OSO2CF3) = 2:1). The CV of 4 displays two waves (E-1 = -0.74 V, E-2 = 0.24 V vs. SCE) assigned to the [Cp*(dppe)Fe(I)]/[Cp*(dppe)Fe(II)](+) and [Cp*(dppe)Fe(II)](+)/[Cp*(dppe)Fe(III)](2+) redox couples. Reduction of 4 with Cp2Co provided the complex [Cp*(dppe)Fe(I)] (6, 95 %) and oxidation of 6 with [Cp2Fe]PF6 gave [Cp*(dppe)Fe]PF6 (5(PF6), 98 %). XRD established the pseudo-trigonal bipyramidal geometry for the five-coordinated cation 5(+). The reactivity of 5(PF6) and 6 toward small molecules (CH2Cl2, H2O, CO, H-2, N-2) is reported.