In 2007 Casey and Guan showed that Knolker’s (hydroxycyclopentadienyl)iron dicarbonyl hydride (1) catalyzed ketone and aldehyde hydrogenations. Since then the iron hydride and its air-stable (cyclopentadienone)iron tricarbonyl derivatives (2) have been used as catalysts in a wide variety of oxidative and reductive transformations, including dual catalysis and borrowing hydrogen reactions. Interestingly, there have been a limited number of mechanistic studies of the fundamental iron-catalyzed transformations (alcohol oxidation; aldehyde, ketone, and imine reductions), and even fewer have looked at how cyclopentadienone substitution impacts catalyst reactivity even though it has been established that structural modifications to the cyclopentadienone ligand impact it. A majority of the iron compounds studied in the past contained substituted cyclopentadienones bearing fused rings and sterically hindered groups in the 2- and 5-positions of the cyclopentadienone (3). We synthesized a small collection of iron compounds containing 2,5-disubstituted-3,4-diphenylcyclopentadienones (2 where R2 = phenyl) and explored their catalytic reactivities in alcohol oxidations and carbonyl and imine reductions. Reaction kinetics of these transformations will be discussed and compared to those of the parent iron catalyst.

Reaction kinetics of (3,4-diphenylcyclopentadienone)iron carbonyl-catalyzed alcohol oxidations and carbonyl reductions

253rd National Meeting (2017)

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