Our group has developed homoleptic late 3d transition metal complexes with fluorinated alkoxide ligands for oxidation reactions. Fluorinated, O-donor ligands engender a medium field environment that can result in high-spin configurations and/or unusual electronic structures. Perfluorinated t-butyl groups provide significant steric bulk and favor low-coordination numbers, and are inherently invulnerable to ligand C-H oxidation because they have no such bonds. Since 2013, we have been studying Cu-O2 chemistry with these ligands using the [Cu(OC4F9)2]- and [(Ph3P)Cu(pinF)]- mononuclear species as precursors to {Cu3O2} moieties that effect catalytic oxidase and stoichiometric hydroxylase chemistry. In that work, the K+ counter-cation and its degree of encapsulation were shown to have an important role in the [Cu(OC4F9)2]- system. We have now broadened our investigation to include other alkali metal cations. In particular, we have now used NaOC4F9 and CsOC4F9 to prepare {Na(DME)}[Cu(OC4F9)2], {Na(15C5)}[Cu(OC4F9)2], [CsCu(OC4F9)2], {Cs(18C6)}[Cu(OC4F9)2], and {Cs(18C6)2}[Cu(OC4F9)2]. Both the Na and Cs systems react with O2, sometimes forming similar intermediates to those observed with K, and sometimes not. In some cases similar reactivity to the K system was observed, but both greater and lesser reactivity were also observed, depending on which alkali metal cation was used and its degree of encapsulation. Details of these studies will be presented including temperature-dependent UV-vis spectroscopic characterization of intermediates as well as 1H-NMR spectroscopic and mass spectrometric observations of substrate oxidations.

Alkali metal cation effects on intermediates and products of C-H bond oxidation chemistry effected by {Cun-O2} moieties

ACS Spring Meeting 2021

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