The reactivity of metal centers in metalloproteins is dictated by ligands bound to the metal as well as the hydrogen-bonding network within the greater protein scaffold. Model systems of these enzymes can provide crucial insights into enzyme reactivity by having a precisely defined molecular structure capable of mimicking small molecule processes observed or postulated in biological systems. To this end, we report the use of a tetrapodal ligand scaffold Py2Py(piCy)2 which, when complexed with late first-row transition metals, contains a secondary coordination sphere. Two arms of the ligand scaffold contain a pyrrole-imine functionality that is capable of tautomerization to an azafulvene-amine. This allows for both dative and anionic coordination of the metal center while also providing hydrogen bond donors or acceptors for an axial ligand bound to the metal. Complexation of Py2Py(piCy)2 with iron has led to the isolation of iron(II)-hydroxo and aquo species which can be oxidized to iron(III)-hydroxo complexes with differentiated hydrogen bonding interactions.. Additionally, complexation of Py2Py(piCy)2 with cobalt salts has led to the isolation of the corresponding cobalt complexes which exhibit rare reactivity properties and interesting electronic structures.

Reactivity of late first-row transition metals in a tetrapodal ligand containing a secondary coordination sphere

256th National Meeting (2018)

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