Geometric and electronic structure of a crystallographically characterized thiolate-ligated binuclear peroxo-bridged cobalt(III) complex.

In order to shed light on metal-dependent mechanisms for O-O bond cleavage, and its microscopic reverse, we compare herein the electronic and geometric structures of O-derived binuclear Co(III)- and Mn(III)-peroxo compounds. Binuclear metal peroxo complexes are proposed to form as intermediates during Mn-promoted photosynthetic HO oxidation, and a Co-containing artificial leaf inspired by nature's photosynthetic HO oxidation catalyst. Crystallographic characterization of an extremely activated peroxo is made possible by working with substitution-inert, low-spin Co(III).

Formation of a Reactive, Alkyl Thiolate-Ligated Fe-Superoxo Intermediate Derived from Dioxygen.

Herein, we describe an alkyl thiolate-ligated iron complex that reacts with dioxygen to form an unprecedented example of an iron superoxo (O) intermediate, [Fe(SN(Pr,Pr))(O)] (4), which is capable of cleaving strong C-H bonds. A cysteinate-ligated iron superoxo intermediate is proposed to play a key role in the biosynthesis of β-lactam antibiotics by isopenicillin N-synthase (IPNS). Superoxo 4 converts to a metastable putative Fe(III)-OOH intermediate, at rates that are dependent on the C-H bond strength of the H atom donor, with a kinetic isotope effect ( k/ k = 4.

Metal-Assisted Oxo Atom Addition to an Fe(III) Thiolate.

Cysteinate oxygenation is intimately tied to the function of both cysteine dioxygenases (CDOs) and nitrile hydratases (NHases), and yet the mechanisms by which sulfurs are oxidized by these enzymes are unknown, in part because intermediates have yet to be observed. Herein, we report a five-coordinate bis-thiolate ligated Fe(III) complex, [Fe(SN(Pr,Pr))] (2), that reacts with oxo atom donors (PhIO, IBX-ester, and HO) to afford a rare example of a singly oxygenated sulfenate, [Fe(η-SO)(S)N(Pr,Pr)] (5), resembling both a proposed intermediate in the CDO catalytic cycle and the essential NHase Fe-S(O) proposed to be intimately involved in nitrile hydrolysis. Comparison of the reactivity of 2 with that of a more electron-rich, crystallographically characterized derivative, [FeSNN(Pr,Pr)] (8), shows that oxo atom donor reactivity correlates with the metal ion's ability to bind exogenous ligands.

Stepwise ligand exchange for the preparation of a family of mesoporous MOFs.

A stepwise ligand exchange strategy is utilized to prepare a series of isoreticular bio-MOF-100 analogues. Specifically, in situ ligand exchange with progressively longer dicarboxylate linkers is performed on single crystalline starting materials to synthesize products with progressively larger mesoporous cavities. The new members of this series of materials, bio-MOFs 101-103, each exhibit permanent mesoporosity and pore sizes ranging from ~2.