One-Electron (2c/1e) Tin···Tin Bond Stabilized by -Phenylenediamido Ligands.

Odd-electron bonds, i.e., the two-center, three-electron (2c/3e), or one-electron (2c/1e) bonds, have attracted tremendous interest owing to their novel bonding nature and radical properties.

Boryl radical catalysis enables asymmetric radical cycloisomerization reactions.

The development of functionally distinct catalysts for enantioselective synthesis is a prominent yet challenging goal of synthetic chemistry. In this work, we report a family of chiral -heterocyclic carbene (NHC)-ligated boryl radicals as catalysts that enable catalytic asymmetric radical cycloisomerization reactions. The radical catalysts can be generated from easily prepared NHC-borane complexes, and the broad availability of the chiral NHC component provides substantial benefits for stereochemical control.

Switchable Direct Oxygenative Arylation of C(sp)-H Bonds via Electrophotocatalysis.

A metal-free electrophotochemical C(sp)-H arylation was developed under mild conditions. This method enables a switchable synthesis of diaryl alcohols and diaryl alkanes from inactive benzylic carbons. More importantly, a cheap and safe mediator -chlorosuccinimide (NCS) was developed, which was employed for the hydrogen atom transfer (HAT) process of the benzylic C-H bond.

Vanadium-Catalyzed Dinitrogen Reduction to Ammonia via a [V]═NNH Intermediate.

The catalytic transformation of N to NH by transition metal complexes is of great interest and importance but has remained a challenge to date. Despite the essential role of vanadium in biological N fixation, well-defined vanadium complexes that can catalyze the conversion of N to NH are scarce. In particular, a V(NH) intermediate derived from proton/electron transfer reactions of coordinated N remains unknown.

Biomimetic catalytic aerobic oxidation of C-sp(3)-H bonds under mild conditions using galactose oxidase model compound CuL.

Developing highly efficient catalytic protocols for C-sp(3)-H bond aerobic oxidation under mild conditions is a long-desired goal of chemists. Inspired by nature, a biomimetic approach for the aerobic oxidation of C-sp(3)-H by galactose oxidase model compound CuL and NHPI (-hydroxyphthalimide) was developed. The CuL-NHPI system exhibited excellent performance in the oxidation of C-sp(3)-H bonds to ketones, especially for light alkanes.

1,2,4-Triazolato paddlewheel dibismuth complexes with very short Bi(II)-Bi(II) bonds: bismuth(III) oxidation of 1,2,4-triazolato anions into neutral -1,2,4-triazolyl radicals.

Bismuth(iii) oxidation of 3,5-di-substituted-1,2,4-triazolato anions afforded a paddlewheel 1,2,4-triazolato dibismuth complex [L2(Bi-Bi)L2] (L = η1,η1-3,5-R2tz, R = Ph (3), iPr (4)) with very short Bi(ii)-Bi(ii) bonds (2.8650(4)-2.8721(3) Å).

Reductive linear- and cyclo-trimerization of isocyanides using an Al-Al-bonded compound.

Dialumane 1 reacts with tBuNC to produce a reductive dimerization adduct [LAl(tBuN[double bond, length as m-dash]C-C[double bond, length as m-dash]NtBu)AlL] (2). In the presence of Na, 1 can promote linear- and cyclo-trimerization of isocyanides, affording products [Na][LAl{(tBuNC)3}AlL] (3 and 4) and [Na][LAl{(tBuNC)3}Al(C[triple bond, length as m-dash]N)L] (5), the latter of which features a unique aromatic tri(tert-butylimino)deltate dianion [C3N3(tBu)3]2-.

One-pot selective synthesis of azoxy compounds and imines via the photoredox reaction of nitroaromatic compounds and amines in water.

A facile one-pot two-stage photochemical synthesis of aromatic azoxy compounds and imines has been developed by coupling the selective reduction of nitroaromatic compounds with the selective oxidation of amines in an aqueous solution. In the first stage (light illumination, Ar atmosphere), the light excited nitroaromatic molecule abstract H from amine to form ArNOH and amine radical, which then form nitrosoaromatic, hydroxylamine and imine compounds. Water acts as a green solvent for the dispersion of the reactants and facilitates the formation of nitrosoaromatic and hydroxylamine intermediate compounds.

Iron-catalyzed carboazidation of alkenes and alkynes.

Carboazidation of alkenes and alkynes holds the promise to construct valuable molecules directly from chemical feedstock therefore is significantly important. Although a few examples have been developed, there are still some unsolved problems and lack of universal methods for carboazidation of both alkenes and alkynes. Here we describe an iron-catalyzed rapid carboazidation of alkenes and alkynes, enabled by the oxidative radical relay precursor t-butyl perbenzoate.

Multifunctionalization of Unactivated Cyclic Ketones via an Electrochemical Process: Access to Cyclic α-Enaminones.

The multifunctionalization of unactivated cyclic ketones was developed via an electrochemically intermolecular α-amination under metal-free conditions. The reaction can be carried out smoothly with a broad scope of the aromatic amines substrates under mild conditions, affording a variety of α-enaminones with good to excellent yields in one step.

Direct evidence of charge separation in a metal-organic framework: efficient and selective photocatalytic oxidative coupling of amines charge and energy transfer.

The selective aerobic oxidative coupling of amines under mild conditions is an important laboratory and commercial procedure yet a great challenge. In this work, a porphyrinic metal-organic framework, PCN-222, was employed to catalyze the reaction. Upon visible light irradiation, the semiconductor-like behavior of PCN-222 initiates charge separation, evidently generating oxygen-centered active sites in Zr-oxo clusters indicated by enhanced porphyrin π-cation radical signals.

Radical-Facilitated Green Synthesis of Highly Ordered Mesoporous Silica Materials.

In the hydrothermal synthesis of highly ordered mesoporous silica material SBA-15, strong acid is typically required to catalyze the hydrolysis and condensation of silica species. Meanwhile, under strongly acidic conditions, the transition metal ions, e.g.

A Chiral Ligand Assembly That Confers One-Electron O Reduction Activity for a Cu -Selective Metallohydrogel.

The design of functional metallohydrogels is attractive but challenging. A rational approach is introduced for designing functional metallohydrogels using chiral ligands, a phenylalanine derivative with a pyridyl group (l/d-PF). Intriguingly, the as-prepared metallohydrogel exhibits excellent O binding and activating properties.

Direct Evidence for Neutral N-Pyrazolyl Radicals: Paddlewheel Dibismuthanes Bearing Pyrazolato Ligands with Very Short Bi-Bi Single Bonds.

Neutral N-pyrazolyl radicals [3,5-Rpz] as reactive intermediates were generated by one-electron oxidization of the corresponding 3,5-disubstituted pyrazolato anions [3,5-Rpz] (R = tBu, Ph) with BiCl and trapped by the use of 5,5-dimethyl-1-pyrroline-N-oxide as a spin trap, which was confirmed by electron paramagnetic resonance spectral analysis. With dimerization of the postulated pyrazolato low-valent Bi radical species, two novel paddlewheel pyrazolatodibismuthanes [L(Bi-Bi)L] [L = η,η-3,5-Rpz; R = tBu (5α, 5β, and 5γ), Ph (6)] were isolated and structurally characterized.

Noninnocent ligands: heteroleptic nickel complexes with α-diimine and 1,2-diketone derivatives.

Reaction of the Ni-Ni-bonded compound [(NiL˙)] (1, L = [(2,6-iPrCH)NC(Me)]) with various 1,2-diketones afforded a series of heteroleptic complexes: [LNi(PhC(O)-C(O)Ph)] (2), [LNi(PhC(O)-C(O)Me)] (3), [LNi(3,5-tBuCHO)] (4), and [(LNi){μ-η,η-(MeC(O)-C(O)Me)}(NiL)] (5). Furthermore, the complex [Na(EtO)][LNi{PhC(O)-C(O)Ph}] (6) was obtained by the reduction of 2 with 1.0 equiv.

Electrocatalytic C-H/N-H Coupling of 2'-Aminoacetophenones for the Synthesis of Isatins.

2'-Aminoacetophenones undergo a C(sp)-H oxidation followed by intramolecular C-N bond formation by virtue of a simple electrochemical oxidation in the presence of n-BuNI, providing various isatins with moderate to good yields. The reaction intermediates were detected, and a radical-based pathway was proposed.

Rational Design of Dual Active Sites in a Single Protein Scaffold: A Case Study of Heme Protein in Myoglobin.

Rational protein design has been proven to be a powerful tool for creating functional artificial proteins. Although many artificial metalloproteins with a single active site have been successfully created, those with dual active sites in a single protein scaffold are still relatively rare. In this study, we rationally designed dual active sites in a single heme protein scaffold, myoglobin (Mb), by retaining the native heme site and creating a copper-binding site remotely through a single mutation of Arg118 to His or Met.

Accelerated crystallization of zeolites via hydroxyl free radicals.

In the hydrothermal crystallization of zeolites from basic media, hydroxide ions (OH(-)) catalyze the depolymerization of the aluminosilicate gel by breaking the Si,Al-O-Si,Al bonds and catalyze the polymerization of the aluminosilicate anions around the hydrated cation species by remaking the Si,Al-O-Si,Al bonds. We report that hydroxyl free radicals (•OH) are involved in the zeolite crystallization under hydrothermal conditions. The crystallization processes of zeolites-such as Na-A, Na-X, NaZ-21, and silicalite-1-can be accelerated with hydroxyl free radicals generated by ultraviolet irradiation or Fenton's reagent.

Synthesis and structures of mononuclear and dinuclear gallium complexes with α-diimine ligands: reduction of the metal or ligand?

Reduction of the dichloro gallium(III) α-diimine complex [(L(ipr))˙(-)GaCl2] (1, L(ipr) = [(2,6-iPr2C6H3)NC(Me)]2) by different equivalents of sodium metal afforded the gallium complexes [(L(ipr))(2-)Ga(III)(μ2-Cl)2Na(THF)4] (2) and [(Na(THF)6)(+)·((L(ipr))(2-)Ga-Ga(L(ipr))(2-))˙(-)] (3). Interestingly, in complex 2 a Na(+)Cl(-) ion pair is incorporated, while compound 3 is an anionic digallium complex. Moreover, a cationic gallium complex with a tetrachlorogallium(III) counter anion, [(LGaCl2)(+)·(GaCl4)(-)] (4), was accessed from the reaction of GaCl3 with 0.

Mono- and Dinuclear Heteroleptic Cobalt Complexes with α-Diimine and Polyarene Ligands.

Reactions of the dimeric cobalt complex [(L(-) Co)2 ] (1, L=[(2,6-iPr2 C6 H3 )NC(Me)]2 ) with polyarenes afforded a series of mononuclear and dinuclear complexes: [LCo(η(4) -anthracene)] (2), [LCo(μ-η(4) :η(4) -naphthalene)CoL] (3), and [LCo(μ-η(4) :η(4) -phenanthrene)CoL] (4). The pyrene complexes [{Na2 (Et2 O)2 }{LCo(μ-η(3) :η(3) -pyrene)CoL}] (5) and [{Na2 (Et2 O)3 }{LCo(η(3) -pyrene)}] (6) were obtained by treating precursor 1 with pyrene followed by reduction with Na metal. These complexes contain three potential redox active centers: the cobalt metal and both α-diimine and polyarene ligands.

The ligand redox behavior and role in 1,2-bis[(2,6-diisopropylphenyl)imino]-acenaphthene nickel-TMA(MAO) systems for ethylene polymerization.

The BIAN ligands in Brookhart catalysts were proved to be redox-active during the catalyst activation with alkylaluminum or MAO, and the neutral catalytically active species with a radical anionic BIAN rather than the cationic ones with a neutral BIAN ligand were confirmed to be formed in the catalytic system.

Gallium complexes with α-diimine and phenazine in various reduced states.

Reaction of α-diimine-stabilized "digallane" [Ga2L2] with phenazine (Phz) leads to gallium complexes in which Phz and α-diimine show different reduced forms, demonstrating their noninnocence and diverse coordination modes.

Experimental and theoretical approaches for the surface interaction between copper and activated sludge microorganisms at molecular scale.

Interactions between metals and activated sludge microorganisms substantially affect the speciation, immobilization, transport, and bioavailability of trace heavy metals in biological wastewater treatment plants. In this study, the interaction of Cu(II), a typical heavy metal, onto activated sludge microorganisms was studied in-depth using a multi-technique approach. The complexing structure of Cu(II) on microbial surface was revealed by X-ray absorption fine structure (XAFS) and electron paramagnetic resonance (EPR) analysis.

Distinct stepwise reduction of a nickel-nickel-bonded compound containing an α-diimine ligand: from perpendicular to coaxial structures.

A nickel-nickel-bonded complex, [{Ni(μ-L(.-))}2] (1; L=[(2,6-iPr2C6H3)NC(Me)]2), was synthesized from reduction of the LNiBr2 precursor by sodium metal. Further controllable reduction of 1 with 1.

Cobalt-catalyzed oxidative [3 + 2] cycloaddition reactions: an efficient synthesis of pyrrolo- and imidazo-[2,1-a]isoquinolines.

A cobalt-catalyzed oxidative [3 + 2] cycloaddition cascades of dihydroisoquinoline esters with nitroolefins or N-sulfuryl aldimines were developed at room temperature. A multi-component reaction for the synthesis of 5,6-dihydroimidazo[2,1-a]isoquinolines were also realized under almost identical conditions. This method is particularly suitable for the synthesis of tricyclic nitrogen heterocycles due to its simple manipulation, wide scope of the reaction substrates and excellent regioselectivity.