Lewis Acid Chemistry at the Edge of Ferrocene Frieder Jäkle, Department of Chemistry Rutgers University, Newark, NJ 07102 Ferrocene-based bidentate Lewis acids have been investigated as threedimensional, redox-active analogs of more well-established bidentate Lewis acids that utilize phenylene and naphthalene scaffolds. Diboradiferrocene
Dication 2+ MeCN Ph B FeIII
III Ph Fe
Oxidation in MeCN
Ph
NCMe
Fe
+
Oxidation In CH2Cl2
Fe
B
B
Mixed-Valent Cation Ph
B Ph
1
These observations suggest applications in anion recognition and Lewis acid catalysis - studies that are currently under way.
Ph
X = I5 X = PF6 X = SbF6 X = B(C6F5)4
NIR Spectrum of [1+]SbF6 0.8 0.6 0.4 0.2 0 800
1200
1600
2000
Wavelength / nm
X–
[1+]I5 [1+]PF6 [1+]SbF6 [1+][B(C6F5)4]
Mössbauer Data of [1+]B(C6F5)4
1 Absorbance / a.u.
Left: In the presence of donor solvents dioxidation is observed. The dication is highly Lewis acidic as evident from the formation of stable complexes with acetonitrile - in sharp contrast to the neutral diboradiferrocene !
B
Fe
Right: Mono-oxidation of the diboradiferrocene (1) in noncoordinating solvents leads to an intriguing mixed-valent cation (1+), which shows distinct NIR bands in solution and, with B(C6F5)4 as the counterion, Mössbauer data that are consistent with rapid electron transfer (one set of averaged signals).
Fe
B
2400
Li[B(C6F5)4
