Natural metalloenzymatic machinery makes use of bioavailable metal ions (Fe, Cu, Mn, Zn, etc.) to carry out important chemical transformations.1 The active site of these enzymes usually combines metal ions with natural ligands (N, O and S-donors) with or without the ability to provide e— (e.g. porphyrin -cation radical in Cmpd-I in Cyt. P450). In most cases, the primary and secondary coordination sphere of surrounding the metal center are highly structured due to the presence of H-bonding interactions that provide unique reactive properties to these metal complexes such as fast e— transfer rates (e.g. entatic state of blue copper proteins) and control of the reductive reactivity of M-O2 species (e.g. heterolytic O-O cleavage in Cyt. P450).2 In this research article, we describe the structure, spectroscopy and reactivity of 1st row metal complexes bearing bidentate redox-active ligands that contain H-bonding donor groups. These unsaturated tetracoordinate complexes are stabilized by intramolecular H-bonding interactions between the two ligand scaffolds and between the ligand H-donor and the metal center.3 Interestingly, the copper complexes were found to be able to undergo multiple oxidation-reduction processes associated with the metal ion (CuI to CuIII) and the o-phenyldiamido ligand (diamido, diiminato radical and diimine).4 Some of the copper(II) complexes could carry out the oxidation of alcohols to aldehydes or ketone using only O2 and at room temperature. Like in galactose oxidase, the copper(II) complexes are proposed to deprotonate and coordinate the alcohol substrate and be oxidized to form reactive copper ligand-radical species that oxidize the substrate.5(Fig. 1)

Catalytic aerobic oxidation of alcohols by copper complexes bearing redox-active ligands with tunable H-bonding groups

255th National Meeting (2018)

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