Multicomponent Electrosynthesis of Enaminyl Sulfonates Starting from Alkylamines, SO, and Alcohols.

An electrochemical one-pot synthesis of enaminyl sulfonate esters was established, featuring a quasidivided cell under constant current conditions. The multicomponent reaction utilizes simple and readily available alkylamines and an easy-to-use stock solution of SO and alcohols. Omission of additional supporting electrolyte through in-situ-generated monoalkylsulfite facilitates the downstream processing.

Experimentally Assessing the Electronic Structure and Spin-State Energetics in MnFe Dimers Using 1s3p Resonant Inelastic X-ray Scattering.

The synergistic interaction between Mn and Fe centers is investigated via a comprehensive analysis of full 1s3p resonant inelastic X-ray scattering (RIXS) planes at both the Fe and Mn K-edges in a series of homo- and heterometallic molecular systems. Deconvolution of the experimental two-dimensional 1s3p RIXS maps provides insights into the modulation of metal-ligand covalency and variations in the metal multiplet structure induced by subtle electronic structural differences imposed by the presence of the second metal. These modulations in the electronic structure are key toward understanding the reactivity of biological systems with active sites that require heterometallic centers, including MnFe purple acid phosphatases and MnFe ribonucleotide reductases.

The spin-forbidden transition in iron(IV)-oxo catalysts relevant to two-state reactivity.

Quintet oxoiron(IV) intermediates are often invoked in nonheme iron enzymes capable of performing selective oxidation, while most well-characterized synthetic model oxoiron(IV) complexes have a triplet ground state. These differing spin states lead to the proposal of a two-state reactivity model, where the complexes cross from the triplet to an excited quintet state. However, the energy of this quintet state has never been measured experimentally.

Understanding Ligand Effects on Bielectronic Transitions: Chemo- and Electroreduction of Rhodium Bis(Diphosphine) Complexes to Low Oxidation States.

Rhodium complexes in the -I and 0 oxidation states are of great potential interest in catalytic applications. In contrast to their rhodium +I congeners, however, the structural and electronic parameters governing their access and stability are far less understood. Herein, we investigate the two-electron reduction of a parameterized series of bis(diphosphine) Rh complexes [Rh(dxpy)]NTf (x=P-substituent, y=alkanediyl bridging P atoms).

A Cooperative Cobalt-Driven System for One-Carbon Extension in the Synthesis of ()-Silyl Enol Ethers from Aldehydes: Unlocking Regio- and Stereoselectivity.

The research presented herein explores a cobalt-based catalytic system, distinctively featuring a cooperative boron-centric element within its intricate ligand architecture. This system is strategically engineered to enable the integration of a singular carbon atom into aldehydes, a process culminating in the production of ()-silyl enol ethers. Beyond offering an efficient one-pot synthesis route, this method adeptly overcomes challenges inherent to conventional techniques, such as the need for large amounts of additives, restrictive functional group tolerance, and extreme reaction temperatures.

Activated Mn-MACHO Complexes Form Stable CO Adducts.

Manganese(I) carbonyl complexes bearing a MACHO-type ligand (HN(CH CH PR ) ) readily react in their amido form with CO to generate 4-membered {Mn-N-C-O} metallacycles. The stability of the adducts decreases with the steric demand of the R groups at phosphorous (R=isopropyl>adamantyl). The CO -adducts display generally a lower reactivity as compared to the parent amido complexes.

Hydride-Free Hydrogenation: Unraveling the Mechanism of Electrocatalytic Alkyne Semihydrogenation by Nickel-Bipyridine Complexes.

Hydrogenation reactions of carbon-carbon unsaturated bonds are central in synthetic chemistry. Efficient catalysis of these reactions classically recourses to heterogeneous or homogeneous transition-metal species. Whether thermal or electrochemical, C-C multiple bond catalytic hydrogenations commonly involve metal hydrides as key intermediates.

A Cooperative Rhodium/Secondary Phosphine Oxide [Rh/P(O)nBu ] Template for Catalytic Hydrodefluorination of Perfluoroarenes.

The selective activation of C-F bonds under mild reaction conditions remains an ongoing challenge of bond activation. Here, we present a cooperative [Rh/P(O)nBu ] template for catalytic hydrodefluorination (HDF) of perfluoroarenes. In addition to substrates presenting electron-withdrawing functional groups, the system showed an exceedingly rare tolerance for electron-donating functionalities and heterocycles.

Selective oxidation of silanes into silanols with water using [MnBr(CO)] as a precatalyst.

The development of earth-abundant catalysts for the selective conversion of silanes to silanols with water as an oxidant generating valuable hydrogen as the only by-product continues to be a challenge. Here, we demonstrate that [MnBr(CO)] is a highly active precatalyst for this reaction, operating under neutral conditions and avoiding the undesired formation of siloxanes. As a result, a broad substrate scope, including primary and secondary silanes, could be converted to the desired products.

Metal complexes of a pro-vitamin K3 analog phthiocol (2-hydroxy-3-methylnaphthalene-1,4-dione): synthesis, characterization, and anticancer activity.

The hydroxy analog of vitamin K3 (2-methylnaphthalene-1,4-dione) is known as phthiocol (2-hydroxy-3-methylnaphthalene-1,4-dione; pht). Both vitamin K3 and phthiocol possess anticancer and antihemorrhagic properties. Phthiocol is a noninnocent ligand and provides monodentate, bidentate, or tridentate coordination sites to metal ions.

An Adaptive Rhodium Catalyst to Control the Hydrogenation Network of Nitroarenes.

An adaptive catalytic system that provides control over the nitroarene hydrogenation network to prepare a wide range of aniline and hydroxylamine derivatives is presented. This system takes advantage of a delicate interplay between a rhodium(III) center and a Lewis acidic borane introduced in the secondary coordination sphere of the metal. The high chemoselectivity of the catalyst in the presence of various potentially vulnerable functional groups and its readiness to be deployed at a preparative scale illustrate its practicality.

Rhodium(i) complexes derived from tris(isopropyl)-azaphosphatrane-controlling the metal-ligand interplay.

Proazaphosphatranes are intriguing ligand architectures comprising a bicyclic cage of flexible nature. They can undergo structural deformations due to transannulation while displaying modular electronic and steric properties. Herein, we report the synthesis and coordination chemistry of rhodium(i) complexes bearing a tris(isopropyl)-azaphosphatrane (TPrAP) ligand.

Stabilization of intermediate spin states in mixed-valent diiron dichalcogenide complexes.

The electronic structure and ground spin states, S, observed for mixed-valent iron-sulfur dimers (Fe-Fe) are typically determined by the Heisenberg exchange interaction, J, that couples the magnetic interaction of the two metal centres either ferromagnetically (J > 0, S = 9/2) or antiferromagnetically (J < 0, S = 1/2). In the case of antiferromagnetically coupled iron centres, stabilization of the high-spin S = 9/2 ground state is also feasible through a Heisenberg double-exchange interaction, B, which lifts the degeneracy of the Heisenberg spin states. This theorem also predicts intermediate spin states for mixed-valent dimers, but those have so far remained elusive.

Systematic Variation of 3d Metal Centers in a Redox-Innocent Ligand Environment: Structures, Electrochemical Properties, and Carbon Dioxide Activation.

Coordination compounds of earth-abundant 3d transition metals are among the most effective catalysts for the electrochemical reduction of carbon dioxide (CO). While the properties of the metal center are crucial for the ability of the complexes to electrochemically activate CO, systematic variations of the metal within an identical, redox-innocent ligand backbone remain insufficiently investigated. Here, we report on the synthesis, structural and spectroscopic characterization, and electrochemical investigation of a series of 3d transition-metal complexes [M = Mn(I), Fe(II), Co(II), Ni(II), Cu(I), and Zn(II)] coordinated by a new redox-innocent PNP pincer ligand system.

Coordination polymers of Ag(i) and Hg(i) ions with 2,2'-azobispyridine: synthesis, characterization and enhancement of conductivity in the presence of Cu(ii) ions.

The cationic coordination polymers (CPs) of the types [Hg(abpy)][PF] (1) and [Ag(abpy)][PF] (2) (abpy = 2,2'-azobispyridine) were synthesized and characterized. Experimentation using the crystals confirmed that 1 and 2 are conductors of electricity. The relative conductivity of 1 is 62 times greater than that of 2.

Ruthenium 4d-to-2p X-ray Emission Spectroscopy: A Simultaneous Probe of the Metal and the Bound Ligands.

Ruthenium 4d-to-2p X-ray emission spectroscopy (XES) was systematically explored for a series of Ru and Ru species. Complementary density functional theory calculations were utilized to allow for a detailed assignment of the experimental spectra. The studied complexes have a range of different coordination spheres, which allows the influence of the ligand donor/acceptor properties on the spectra to be assessed.

Controlling the Product Platform of Carbon Dioxide Reduction: Adaptive Catalytic Hydrosilylation of CO Using a Molecular Cobalt(II) Triazine Complex.

The catalytic reduction of carbon dioxide (CO ) is considered a major pillar of future sustainable energy systems and chemical industries based on renewable energy and raw materials. Typically, catalysts and catalytic systems are transforming CO preferentially or even exclusively to one of the possible reduction levels and are then optimized for this specific product. Here, we report a cobalt-based catalytic system that enables the adaptive and highly selective transformation of carbon dioxide individually to either the formic acid, the formaldehyde, or the methanol level, demonstrating the possibility of molecular control over the desired product platform.

Hydroamination of Aromatic Alkynes to Imines Catalyzed by Pd(II)-Anthraphos Complexes.

Herein, we report the synthesis, characterization, and catalytic performance of cationic Pd(II)-Anthraphos complexes in the intermolecular hydroamination of aromatic alkynes with aromatic amines. The reaction proceeds with 0.18 mol % of catalyst loading, at 90 °C for 4 h under neat conditions.

Metal promoted conversion of aromatic amines to ortho-phenylenediimine derivatives by a radical coupling path.

A radical path for the conversion of o-substituted arylamines to o-phenylenediimine derivatives is reported. In the presence of [RuII(PPh3)3Cl2] (RuP), 2-(phenylthio)aniline (LSNH2) acts as an o-amination agent. Reaction of LSNH2 with RuP in toluene promotes (4e + 4H+) oxidative dimerization affording an o-phenylenediimine complex of ruthenium(ii).

From Ylides to Doubly Yldiide-Bridged Iron(II) High Spin Dimers via Self-Protolysis.

A synthetic strategy for the preparation of novel doubly yldiide bridged iron(II) high spin dimers ([(μ-C)FeL], L = N(SiMe), Mesityl) has been developed. This includes the synthesis of ylide-iron(II) monomers [(Ylide)FeL] via adduct formation. Subsequent self-protolysis at elevated temperatures by deprotonation of the ylide ligands results in a dimerization reaction forming the desired bridging μ-C yldiide ligands in [(μ-C)FeL].

Spectroscopic and Quantum Chemical Investigation of Benzene-1,2-dithiolate-Coordinated Diiron Complexes with Relevance to Dinitrogen Activation.

In this work, a benzene-1,2-dithiolate (bdt) pentamethylcyclopentadienyl di-iron complex [Cp*Fe(μ-η:η-bdt)FeCp*] and its [Cp*Fe(bdt)(X)FeCp*] analogues (where X = NH, NH, H, NH, NHCH, or NO) were investigated through spectroscopic and computational studies. These complexes are of relevance as model systems for dinitrogen activation in nitrogenase and share with its active site the presence of iron, sulfur ligands, and a very flexible electronic structure. On the basis of a combination of X-ray emission spectroscopy (XES), X-ray crystallography, Mössbauer, NMR, and EPR spectroscopy, the geometric and electronic structure of the series has been experimentally elucidated.

Coordination Modes, Oxidation, and Protonation Levels of 2,6-Pyridinediimine and 2,2':6',2'́-Terpyridine Ligands in New Complexes of Cobalt, Zirconium, and Ruthenium. An Experimental and Density Functional Theory Computational Study.

The syntheses and molecular and electronic structures of the following complexes have been established by single crystal X-ray crystallography and UV-vis-NIR spectroscopy, and verified by density functional theory calculations (DFT B3LYP): [(η-Cp)Zr(tpy)] ( S = 0) 1, [(η-Cp)Zr(pdi)] ( S = 0) 2, [Co(pdi)(η-BH)] ( S = 0) 4, [Ru(pdi-H)Cl(PPh)] ( S = 0) 5, cis-[Ru(pdi)Cl(PPh)] ( S = 0) 6, and [Ru(η-pdi)(η-pdi-H)] ( S = 0) 7, with (tpy) being neutral 2,2':6',2'́-terpyridine, (tpy) its π radical anion, (tpy) its dianion; (pdi) neutral 2,6-bis(4-methoxyphenylmethylimine)pyridine, (pdi) its radical anion and (pdi) its dianion; (pdi-H) represents the deprotonated form of the (pdi) ligand where deprotonation takes place at the meta-position of the pyridine ring. Density functional theory calculations using the B3LYP functional were performed, establishing geometry optimized molecular and electronic structures. The structural parameter Δ = [(average distance C-C) - (av.

Manganese-catalyzed hydroboration of carbon dioxide and other challenging carbonyl groups.

Reductive functionalization of the C=O unit in carboxylic acids, carbonic acid derivatives, and ultimately in carbon dioxide itself is a challenging task of key importance for the synthesis of value-added chemicals. In particular, it can open novel pathways for the valorization of non-fossil feedstocks. Catalysts based on earth-abundant, cheap, and benign metals would greatly contribute to the development of sustainable synthetic processes derived from this concept.