High valent metal-oxidos are ubiquitous in biology as reactive intermediates for a wide variety of oxidative transformations. For example, the formally iron(V)-oxido species formed within the cytochrome P450 class of monooxygenase enzymes (denoted compound I) is capable of hydroxylating strong C–H bonds upwards of 100 kcal/mol, a process integral to phase I drug metabolism and complex steroid biosynthesis. Studies on the electronic structure of compound I, however, indicate an Fe(IV) center that is magnetically coupled to a ligand radical that is delocalized across the bound porphyrin and cysteine thiolate ligands. Studies have also shown that nearby residues within the secondary coordination sphere of the metal ion are capable of forming hydrogen bonds to the axial oxido ligand. Drawing inspiration from nature we report the synthesis of transition metal coordination compounds of a redox active [NNN]-pincer ligand, N,N′-(azanediylbis(2,1-phenylene))bis(2,4,6-triisopropylbenzenesulfon-amide) (H3ibaps), with appended sulfonamide arms to promote intramolecular hydrogen bonds. Coordination of both the doubly and triply deprotonated forms of the ligand to transition metal ions such as FeII/III or MnII/III leads to discrete 1:1 metal-Hibaps or metal-ibaps complexes, respectively, with open coordination sites for additional ligands, such as 2,2’-bipyridine (bpy) and 2-picolylthiolate (pyCH2S–). These complexes exhibit rich redox chemistry and reactions with oxidants such as [FeCp2]BF4 and isopropyl 2-iodoxybenzoate have been performed.

Bioinspired monooxygenase mimics: Towards the design of functional high valent metal-oxo intermediates

255th National Meeting (2018)

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