Influence of the nacnac Ligand in Iron(I)-Mediated P4 Transformations

A study of P-4 transformations at low-valent iron is presented using -diketiminato (L) Fe-I complexes [LFe(tol)] (tol=toluene; L=L-1 (1a), L-2 (1b), L-3 (1c)) with different combinations of aromatic and backbone substituents at the ligand. The products [(LFe)(4)((4)-(2):(2):(2):(2)-P-8)] (L=L-1 (2a), L-2 (2b)) containing a P-8 core were obtained by the reaction of 1a,b with P-4 in toluene at room temperature. Using a slightly more sterically encumbered ligand in 1c results in the formation of [((LFe)-Fe-3)(2)(-(4):(4)-P-4)] (2c), possessing a cyclo-P-4 moiety. Compounds 2a-c were comprehensively characterized and their electronic structures investigated by SQUID magnetization and Fe-57 Mossbauer spectroscopy as well as by DFT methods

An Intermediate Cobalt(IV) Nitrido Complex and its N-Migratory Insertion Product

International audienceLow-temperature photolysis experiments (T = 10 K) on the tripodal azido complex [(BIMPNMes,Ad,Me)CoII(N3)] (1) were monitored by EPR spectroscopy and support the formation of an exceedingly reactive, high-valent Co nitrido species [(BIMPNMes,Ad,Me)CoIV(N)] (2). Density functional theory calculations suggest a low-spin d5, S = 1/2, electronic configuration of the central cobalt ion in 2 and, thus, are in line with the formulation of complex 2 as a genuine, low-spin Co(IV) nitride species. Although the reactivity of this species precludes handling above 50 K or isolation in the solid state, the N-migratory insertion product [(NH-BIMPNMes,Ad,Me)CoII](BPh4) (3) is isolable and was reproducibly synthesized as well as fully characterized, including CHN elemental analysis, paramagnetic 1H NMR, IR, UV–vis, and EPR spectroscopy as well as SQUID magnetization and single-crystal X-ray crystallography studies. A computational analysis of the reaction pathway 2 → 3 indicates that the reaction readily occurs via N-migratory insertion into the Co–C bond (activation barrier of 2.2 kcal mol–1). In addition to the unusual reactivity of the nitride 2, the resulting divalent cobalt complex 3 is a rare example of a trigonal pyramidal complex with four different donor ligands of a tetradentate chelate—an N-heterocyclic carbene, a phenolate, an imine, and an amine—binding to a high-spin Co(II) ion. This renders complex 3 chiral-at-metal

An Intermediate Cobalt(IV) Nitrido Complex and its N-Migratory Insertion Product

International audienceLow-temperature photolysis experiments (T = 10 K) on the tripodal azido complex [(BIMPNMes,Ad,Me)CoII(N3)] (1) were monitored by EPR spectroscopy and support the formation of an exceedingly reactive, high-valent Co nitrido species [(BIMPNMes,Ad,Me)CoIV(N)] (2). Density functional theory calculations suggest a low-spin d5, S = 1/2, electronic configuration of the central cobalt ion in 2 and, thus, are in line with the formulation of complex 2 as a genuine, low-spin Co(IV) nitride species. Although the reactivity of this species precludes handling above 50 K or isolation in the solid state, the N-migratory insertion product [(NH-BIMPNMes,Ad,Me)CoII](BPh4) (3) is isolable and was reproducibly synthesized as well as fully characterized, including CHN elemental analysis, paramagnetic 1H NMR, IR, UV–vis, and EPR spectroscopy as well as SQUID magnetization and single-crystal X-ray crystallography studies. A computational analysis of the reaction pathway 2 → 3 indicates that the reaction readily occurs via N-migratory insertion into the Co–C bond (activation barrier of 2.2 kcal mol–1). In addition to the unusual reactivity of the nitride 2, the resulting divalent cobalt complex 3 is a rare example of a trigonal pyramidal complex with four different donor ligands of a tetradentate chelate—an N-heterocyclic carbene, a phenolate, an imine, and an amine—binding to a high-spin Co(II) ion. This renders complex 3 chiral-at-metal

TiO2 nanotubes: Nitrogen-ion implantation at low dose provides noble-metal-free photocatalytic H2-evolution activity

Low-dose nitrogen implantation induces an ion and damage profile in TiO2 nanotubes that leads to “co-catalytic” activity for photocatalytic H2-evolution (without the use of any noble metal). Ion implantation with adequate parameters creates this active zone limited to the top part of the tubes. The coupling of this top layer and the underlying non-implanted part of the nanotubes additionally contributes to an efficient carrier separation and thus to a significantly enhanced H2 generation

Configurationally Stable Chiral Dithia-Bridged Hetero[4]helicene Radical Cation: Electronic Structure and Absolute Configuration

A stable chiral hetero[4]helicene radical cation was synthesized and characterized by UV-Vis absorption and EPR spectroscopy as well as X-ray crystallography. For the first time a combination of chiroptical methods involving ECD, ORD, and VCD, supported by quantum mechanical predictions, enabled the elucidation of the absolute configuration of such open-shell helical species

Unique anisotropic optical properties of a highly stable metal–organic framework based on trinuclear iron(III) secondary building units linked by tetracarboxylic linkers with an anthracene core

A highly stable metal–organic framework, [{Fe3(ACTBA)2}X·6DEF]n (1; X = monoanion), based on trinuclear iron(III) secondary building units connected by tetracarboxylates with an anthracene core, 2,6,9,10-tetrakis(p-carboxylatophenyl)anthracene (ACTBA), is reported. Depending on the direction of light polarisation, crystals of 1 exhibit anisotropic optical properties with birefringence Δn = 0.3 (λ = 590 nm)

An Intermediate Cobalt(IV) Nitrido Complex and its N‑Migratory Insertion Product

Low-temperature photolysis experiments (<i>T</i> = 10 K) on the tripodal azido complex [(BIMPN^Mes,Ad,Me)­Co^II(N₃)] (<b>1</b>) were monitored by EPR spectroscopy and support the formation of an exceedingly reactive, high-valent Co nitrido species [(BIMPN^Mes,Ad,Me)­Co^IV(N)] (<b>2</b>). Density functional theory calculations suggest a low-spin d⁵, <i>S</i> = 1/2, electronic configuration of the central cobalt ion in <b>2</b> and, thus, are in line with the formulation of complex <b>2</b> as a genuine, low-spin Co­(IV) nitride species. Although the reactivity of this species precludes handling above 50 K or isolation in the solid state, the N-migratory insertion product [(NH-BIMPN^Mes,Ad,Me)­Co^II]­(BPh₄) (<b>3</b>) is isolable and was reproducibly synthesized as well as fully characterized, including CHN elemental analysis, paramagnetic ¹H NMR, IR, UV–vis, and EPR spectroscopy as well as SQUID magnetization and single-crystal X-ray crystallography studies. A computational analysis of the reaction pathway <b>2</b> → <b>3</b> indicates that the reaction readily occurs via N-migratory insertion into the Co–C bond (activation barrier of 2.2 kcal mol^–1). In addition to the unusual reactivity of the nitride <b>2</b>, the resulting divalent cobalt complex <b>3</b> is a rare example of a trigonal pyramidal complex with four different donor ligands of a tetradentate chelatean N-heterocyclic carbene, a phenolate, an imine, and an aminebinding to a high-spin Co­(II) ion. This renders complex <b>3</b> chiral-at-metal

From an Fe2P3 complex to FeP nanoparticles as efficient electrocatalysts for water-splitting

In large-scale, hydrogen production from water-splitting represents the most promising solution for a clean, recyclable, and low-cost energy source. The realization of viable technological solutions requires suitable efficient electrochemical catalysts with low overpotentials and long-term stability for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) based on cheap and nontoxic materials. Herein, we present a unique molecular approach to monodispersed, ultra-small, and superiorly active iron phosphide (FeP) electrocatalysts for bifunctional OER, HER, and overall water-splitting. They result from transformation of a molecular iron phosphide precursor, containing a [Fe2P3] core with mixed-valence FeIIFeIII sites bridged by an asymmetric cyclo-P(2+1)3− ligand. The as-synthesized FeP nanoparticles act as long-lasting electrocatalysts for OER and HER with low overpotential and high current densities that render them one of the best-performing electrocatalysts hitherto known. The fabricated alkaline electrolyzer delivered low cell voltage with durability over weeks, representing an attractive catalyst for large-scale water-splitting technologies