An iron(ii)-benzoylformate complex of a monoanionic facial tridentate ligand catalyzes the aerobic oxidation of sulfides to sulfoxides, alkenes to epoxides, and alcohols to the corresponding carbonyl compounds.

An iron(III)-catecholate complex of a facial tridentate ligand reacts with dioxygen in the presence of ammonium acetate-acetic acid buffer to cleave the aromatic C-C bond of 3,5-di-tert-butylcatechol regiospecifically resulting in the formation of an extradiol product with multiple turnovers.

Immobilization of transition-metal complexes by surface functionalization of gold nanoparticles (AuNPs) has recently attracted the attention for several applications.[1] Thiolprotected AuNPs [2] are stable and soluble in organic solvents. Therefore, immobilization of metal complexes on AuNPs permits reactions in common organic solvents and also induces properties of the metal complex to the NP.[3] AuNPs functionalized by thiol-appended transition metal complexes are expected to find applications as immobilized catalysts to bridge between homogeneous and heterogeneous catalysis. The high surface area of a nanocatalyst increases the contact between the reactant and catalyst dramatically. These catalysts are easy to synthesize through desired surface modification and can be characterized by different analytical and spectroscopic techniques. Moreover, the catalyst can easily be separated from the reaction mixture. Several reports are now available where immobilization of metal catalysts on AuNPs has been shown to increase the catalytic reactivity.

Two mononuclear iron(ii)-phenylpyruvate complexes of monoanionic facial N3 ligands are reported to react with dioxygen to undergo two consecutive oxidative decarboxylation steps via an iron-mandelate complex mimicking the function of HMS and CloR.

Immobilized biomimetic iron complex: An iron(II) benzoylformate complex of a thiol‐appended N4 ligand immobilized on gold nanoparticles activates dioxygen to carry out oxidative decarboxylation of benzoylformic acid to benzoic acid catalytically.

An iron­(II)-benzilate complex [(TPASH)­FeII­(benzilate)]­ClO4@­C8Au (2) (TPASH = 11-((6-((bis­(pyridin-2-yl­methyl)­amino)­methyl)­pyridin-2-yl)­meth­oxy)­undecane-1-thiol) immobilized on octanethiol stabilized gold nanoparticles (C8Au) of core diameter less than 5 nm has been prepared to evaluate its reactivity toward O2-dependent oxidations compared to a nonimmobilized complex [(TPA-O-Allyl)­FeII­(benzilate)]­ClO4 (1a) (TPA-O-Allyl = N-((6-(allyl­oxy­methyl)­pyridin-2-yl)­methyl)­(pyridin-2-yl)-N-(pyridin-2-ylmeth­yl)­methan­amine). X-ray crystal structure of the nonimmobilized complex 1a reveals a six-coordinate iron­(II) center in which the TPA-O-Allyl acts as a pentadentate ligand and the benzilate anion binds in monodentate fashion. Both the complexes (1a and 2) react with dioxygen under ambient conditions to form benzophenone as the sole product through decarboxylation of the coordinated benzilate. Interception studies reveal that a nucleophilic iron-oxygen intermediate is formed in the decarboxylation reaction. The oxidants from both the complexes are able to carry out oxo atom transfer reactions. The immobilized complex 2 not only performs faster decarboxylation but also exhibits enhanced reactivity in oxo atom transfer to sulfides. Importantly, the immobilized complex 2, unlike 1a, displays catalytic turnovers in sulfide oxidation. However, the complexes are not efficient to carry out cis-dihydroxylation of alkenes. Although the immobilized complex yields a slightly higher amount of cis-diol from 1-octene, restricted access of dioxygen and substrates at the coordinatively saturated metal centers of the complexes likely makes the resulting iron-oxygen species less active in oxygen atom transfer to alkenes. The results implicate that surface immobilized nonheme iron complexes containing accessible coordination sites would exhibit better reactivity in O2-dependent oxygenation reactions.

α-Ketoglutarate-dependent nonheme halogenases catalyze the halogenation of aliphatic C-H bonds in the biosynthesis pathway of many natural products. An iron(IV)-oxo-halo species has been established as the active oxidant in the halogenation reactions. With an objective to emulate the function of the nonheme halogenases, two iron(II)-α-keto acid complexes, [(phdpa)Fe(BF)Cl] (1) and [(1,4-tpbd)Fe(BF)Cl] (2) (where phdpa = N,N-bis(2-pyridylmethyl)aniline, 1,4-tpbd = N,N, N',N'-tetrakis(2-pyridylmethyl)benzene-1,4-diamine, and BF = benzoylformate), have been prepared. The iron complexes are capable of carrying out the oxidative halogenation of aliphatic C-H bonds using O as the terminal oxidant. Although the complexes are not selective toward C-H bond halogenation, they are the only examples of nonheme iron(II)-α-keto acid complexes mimicking the activity of nonheme halogenases. The dinuclear complex (2) exhibits enhanced reactivity toward C-H bond halogenation/hydroxylation.

The chemical functionalization of carbon nanotubes is often a prerequisite prior to their use in various applications. The covalent grafting of 4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolane (BPin) functional groups directly on the surface of multi‐ and single‐walled carbon nanotubes, activated by nucleophilic addition of nBuLi, was carried out. Thermogravimetric analysis (TGA) coupled with mass spectrometry, Raman spectroscopy, X‐ray photoelectron spectroscopy (XPS) and time‐of‐flight secondary ions mass spectrometry (ToF‐SIMS) confirmed the efficiency of this methodology and proved the integrity and covalent grafting of the BPin functional groups. These groups were further reacted with various nucleophiles in the presence of a copper(II) source in the conditions of the aerobic Chan–Lam–Evans coupling. The resulting materials were characterized by TGA, XPS and ToF‐SIMS. This route is efficient, reliable and among the scarce reactions that enable the direct grafting of heteroatoms at carbonaceous material surfaces.