Reactions of a Copper(II) Superoxo Complex Lead to CH and OH Substrate Oxygenation: Modeling Copper‐Monooxygenase CH Hydroxylation

Abstract

Der Donor macht den Unterschied: Der Disauerstoff‐Ligand des einkernigen η1‐Superoxo‐Kupfer(II)‐Komplexes 1 wird durch Wasserstoffatomdonoren aktiviert. Der resultierende Einschub eines O‐Atoms aus der O2‐Gruppe in die N‐gebundene Methylgruppe des Chelatliganden führt zu dem Kupfer(II)‐alkoxid 2. Ohne Zusatz des Donors ist die Superoxospezies 1 nicht in der Lage, die beobachtete Hydroxylierung einzugehen.

Reversible Coordination of Dioxygen by Tripodal Tetraamine Copper Complexes Incorporated in a Porous Silica Framework

“…[20,21,24] However, such stability and reversibility of the dioxygen adduct at room temperature were only described recently in the solid state for an end-on m-peroxodicopper complex with Me 6 TREN [25] and in organic solution for an end-on superoxocopper complex with TREN functionalized by three tetramethylguanidine groups. [22,23,105] This confirms the original biomimetic properties of our material that incorporates tripodal complexes. In addition to the high reactivity of the materials thanks to the adaptability of the tripodal complexes to the different geometries, the stability of the dioxygen adduct can also be explained by the confinement of the active species encapsulated in the silica framework that protects them from degradation, by, for example, hydrolysis of the peroxide or ligand oxidation.…”

“…Therefore, these data confirm the formation of a species in which a bridging chloride occurs in the dinuclear m-h 1 :h 1 -peroxide copper complex (Scheme 2). Notably, the electronic [12,24,105,128] The exceptional reactivity of the described materials is a consequence of the short-range order of the copper complexes in the silica framework occurring during the hydrolytic polycondensation of the alkoxysilylated TREN precursor. Hence, the reactivity is in agreement with an anisotropic distribution of the ligand in a lamellar structure, and the active complexes display a packing of the tripodal complexes in close proximity allowing formation of dimeric O 2 adducts.…”

Dioxygenase‐Like Reactivity of an Isolable Superoxo–Nickel(II) Complex

“…In particular and analogously to 1, reaction of Cu-superoxo [33,34] and Co-superoxo [28,35,36] compounds with DTBP leads to the formation of DTQ. Instead, for the single reported Fe-superoxo species, [37] the same reaction does not result in oxygen incorporation into the substrate, but only in the formation of the coupling product derived from direct intermolecular reaction of two generated phenoxyl radicals.…”

CH Bond Activation by Metal–Superoxo Species: What Drives High Reactivity?

“…[7c, 10b] As these species are key intermediates in iron and copper catalysis, it suggests that the M-O 2 C À species perhaps play a larger role as an oxidant in enzyme catalysis. [6,11] In the M-O 2 C À species the unpaired electrons on the metal and the radical center are strongly coupled and the electronic configuration of the metal ions dictates the nature of the magnetic coupling (J) and this may in turn correlate to the CÀH bond activation. Here we have undertaken a detailed theoretical study to specifically address the following questions 1) probing the mechanism of C À H bond activation by Cr-O 2 C À and its comparative oxidative ability to high-valent metal-oxo species, 2) establishing the comparative oxidative abilities of Fe , and Cr III superoxo-species towards CÀH bond activation reactions, and 3) elucidating the role of magnetic exchange coupling on the activation barrier.…”