Iron-Catalyzed Selective Hydroboration of CO₂ by Cooperative B–H Bond Activation

We report a novel iron(II) complex supported by an anionic phosphanyl-iminopyridinate ligand, Cp*Fe(Cy2PNC5H4N) (1), which shows remarkable catalytic activity in the selective hydroboration of CO2 with HBpin, producing boryl formate with a turnover frequency (TOF) of ∼1176 h–1 at room temperature. This catalysis involves cooperative metal–ligand reactivity for H–B bond activation, affording a key Fe(II)–H intermediate, Cp*FeH(Cy2PN(Bpin)C5H4N) (2), that binds the Bpin moiety at the non-coordinated amino site. The very fast and selective formoxy production can be conveniently coupled to the N-formylation of amines, which delivers a variety of formamides. In addition, the reduction of boryl formate to the CH3OBpin stage was also achieved by 1 with HBpin under N2

Fragments of 'Systema morborum'

Benzo­[1,4]­thiazin-3­(4<i>H</i>)-one derivatives are conveniently prepared in one pot via a Smiles rearrangement (SR) tandem reaction. In order to understand the reaction, we present here a theoretical study on the S–N type SR mechanism

Transition-Metal-Free Synthesis of Fluorinated Arenes from Perfluorinated Arenes Coupled with Grignard Reagents

A simple method to obtain organofluorine compounds from perfluorinated arenes coupled with Grignard reagents in the absence of a transition-metal catalyst was reported. In particular, the perfluorinated arenes could react not only with aryl Grignard reagents but also with alkyl Grignard reagents in moderate to good yields

Hydride Transfer from Iron(II) Hydride Compounds to NAD(P)⁺ Analogues

Iron­(II) hydride complexes of the “piano-stool” type, Cp*­(P-P)­FeH (P-P = dppe (<b>1H</b>), dppbz (<b>2H</b>), dppm (<b>3H</b>), dcpe (<b>4H</b>)) were examined as hydride donors in the reduction of <i>N</i>-benzylpyridinium and acridinium salts. Two pathways of hydride transfer, “single-step H^–” transfer to pyridinium and a “two-step (e^–/H^•)” transfer for acridinium reduction, were observed. When 1-benzylnicotinamide cation (BNA⁺) was used as an H^– acceptor, kinetic studies suggested that <b>BNA</b>^<b>+</b> was reduced at the C6 position, affording 1,6-BNAH, which can be converted to the more thermally stable 1,4-product. The rate constant <i>k</i> of H^– transfer was very sensitive to the bite angle of P–Fe–P in Cp*­(P-P)­FeH and ranged from 3.23 × 10^–3 M^–1 s^–1 for dppe to 1.74 × 10^–1 M^–1 s^–1 for dppm. The results obtained from reduction of a range of <i>N</i>-benzylpyridinium derivatives suggest that H^– transfer is more likely to be charge controlled. In the reduction of 10-methylacridinium ion (<b>Acr</b>^<b>+</b>), the reaction was initiated by an e^– transfer (ET) process and then followed by rapid disproportionation reactions to produce <b>Acr</b>_<b>2</b> dimer and release of H₂. To achieve H^• transfer after ET from [Cp*­(P-P)­FeH]⁺ to acridine radicals, the bulkier acridinium salt 9-phenyl-10-methylacridinium (<b>PhAcr</b>^<b>+</b>) was selected as an acceptor. More evidence for this “two-step (e^–/H^•)” process was derived from the characterization of <b>PhAcr^•</b> and [<b>4H</b>]^<b>+</b> radicals by EPR spectra and by the crystallographic structure confirmation of [<b>4H</b>]^<b>+</b>. Our mechanistic understanding of fundamental H^– transfer from iron­(II) hydrides to NAD⁺ analogues provides insight into establishing attractive bio-organometallic transformation cycles driven by iron catalysis

Hydride Transfer from Iron(II) Hydride Compounds to NAD(P)⁺ Analogues

Iron­(II) hydride complexes of the “piano-stool” type, Cp*­(P-P)­FeH (P-P = dppe (<b>1H</b>), dppbz (<b>2H</b>), dppm (<b>3H</b>), dcpe (<b>4H</b>)) were examined as hydride donors in the reduction of <i>N</i>-benzylpyridinium and acridinium salts. Two pathways of hydride transfer, “single-step H^–” transfer to pyridinium and a “two-step (e^–/H^•)” transfer for acridinium reduction, were observed. When 1-benzylnicotinamide cation (BNA⁺) was used as an H^– acceptor, kinetic studies suggested that <b>BNA</b>^<b>+</b> was reduced at the C6 position, affording 1,6-BNAH, which can be converted to the more thermally stable 1,4-product. The rate constant <i>k</i> of H^– transfer was very sensitive to the bite angle of P–Fe–P in Cp*­(P-P)­FeH and ranged from 3.23 × 10^–3 M^–1 s^–1 for dppe to 1.74 × 10^–1 M^–1 s^–1 for dppm. The results obtained from reduction of a range of <i>N</i>-benzylpyridinium derivatives suggest that H^– transfer is more likely to be charge controlled. In the reduction of 10-methylacridinium ion (<b>Acr</b>^<b>+</b>), the reaction was initiated by an e^– transfer (ET) process and then followed by rapid disproportionation reactions to produce <b>Acr</b>_<b>2</b> dimer and release of H₂. To achieve H^• transfer after ET from [Cp*­(P-P)­FeH]⁺ to acridine radicals, the bulkier acridinium salt 9-phenyl-10-methylacridinium (<b>PhAcr</b>^<b>+</b>) was selected as an acceptor. More evidence for this “two-step (e^–/H^•)” process was derived from the characterization of <b>PhAcr^•</b> and [<b>4H</b>]^<b>+</b> radicals by EPR spectra and by the crystallographic structure confirmation of [<b>4H</b>]^<b>+</b>. Our mechanistic understanding of fundamental H^– transfer from iron­(II) hydrides to NAD⁺ analogues provides insight into establishing attractive bio-organometallic transformation cycles driven by iron catalysis

Ni–O Cooperation versus Nickel(II) Hydride in Catalytic Hydroboration of <i>N</i>‑Heteroarenes

An air-stable half-sandwich nickel­(II) complex bearing a phosphinophenolato ligand, Cp*Ni­(1,2-Ph2PC6H4O) (1), has been designed and synthesized for activation of HBpin and catalytic hydroboration of N-heteroarenes such as pyridine. Through addition of the H–B bond across the Ni–O bond, 1 reacts with HBpin to afford an 18-electron Ni­(II)–H intermediate [H1(Bpin)] featuring an oxygen-stabilized boron moiety, which readily reduces pyridine analogues to give the 1,2-hydroborated product, thus accomplishing the catalytic cycle under mild conditions. The necessity of the phosphinophenolato ligand to deliver the boryl group was manifested by the clear difference in the activity of 1 and Cp*NiH­(PPh3) (3H) in catalytic hydroborations. The latter lacks a functional oxygen atom and is inert to process the catalysis

Gold/Lewis Acid Catalyzed Cycloisomerization/Diastereoselective [3 + 2] Cycloaddition Cascade: Synthesis of Diverse Nitrogen-Containing Spiro Heterocycles

A novel early and late transition-metal relay catalysis has been developed by combining a gold-catalyzed cycloisomerization and a Yb­(OTf)₃-catalyzed diastereoselective [3 + 2] cycloaddition with aziridines in a selective C–C bond cleavage mode. Various biologically significant complex nitrogen-containing spiro heterocycles were rapidly constructed from readily available starting materials under mild conditions

Hierarchical Assembly of a {Mn^II₁₅Mn^III₄} Brucite Disc: Step-by-Step Formation and Ferrimagnetism

In search of functional molecular materials and the study of their formation mechanism, we report the elucidation of a hierarchical step-by-step formation from monomer (Mn) to heptamer (Mn₇) to nonadecamer (Mn₁₉) satisfying the relation 1 + Σ_<i>n</i>6<i>n</i>, where <i>n</i> is the ring number of the Brucite structure using high-resolution electrospray ionization mass spectrometry (HRESI-MS). Three intermediate clusters, Mn₁₀, Mn₁₂, and Mn₁₄, were identified. Furthermore, the Mn₁₉ disc remains intact when dissolved in acetonitrile with a well-resolved general formula of [Mn₁₉­(<i>L</i>)_<i>x</i>­(OH)_<i>y</i>­(N₃)_{36–<i>x</i>−<i>y</i>}]²⁺ (<i>x</i> = 18, 17, 16; <i>y</i> = 8, 7, 6; H<i>L</i> = 1-(hydroxy­methyl)-3,5-dimethylpyrazole) indicating progressive exchange of N₃^– for OH^–. The high symmetry (<i>R</i>-3) Mn₁₉ crystal structure consists of a well-ordered discotic motif where the peripheral organic ligands form a double calix housing the anions and solvent molecules. From the formula and valence bond sums, the charge state is mixed-valent, [Mn^II₁₅Mn^III₄]. Its magnetic properties and electrochemistry have been studied. It behaves as a ferrimagnet below 40 K and has a coercive field of 2.7 kOe at 1.8 K, which can be possible by either weak exchange between clusters through the anions and solvents or through dipolar interaction through space as confirmed by the lack of ordering in frozen CH₃CN. The moment of nearly 50 Nμ_B suggests Mn^II–Mn^II and Mn^III–Mn^III are ferromagnetically coupled while Mn^II–Mn^III is antiferromagnetic which is likely if the Mn^III are centrally placed in the cluster. This compound displays the rare occurrence of magnetic ordering from nonconnected high-spin molecules

Naphthalene Diimide Ammonium Directed Single-Crystalline Perovskites with “Atypical” Ambipolar Charge Transport Signatures in Two-Dimensional Limit

A single crystal of a lead–iodine-based 2D perovskite having naphthalene diimide ammonium (NDIA) molecules as organic layers was developed, and the charge transport property was studied using field-effect transistors (FETs) measurements. Structure determination reveals the layered alternative stacking of lead iodide sheets and NDIA bilayers. The presence of NDIA promoted the lead iodide octahedron to form the unique three-point co-planar [Pb3I10]4– unit, which then connected into the 2D network in a corner-sharing manner. The NDIA cations closely stacked into 1D chains within the bilayers that were being sandwiched between the inorganic layers. FET characteristics of the single crystal obtained at room temperature demonstrate VDS-dependent electron and hole transport behavior with mobilities reaching up to more than 5 × 10–3 cm2 V–1 s–1. The 1D stack of NDIAs contributes greatly to the performance improvement for both the charge transport and the stability

Hierarchical Assembly of a {Mn^II₁₅Mn^III₄} Brucite Disc: Step-by-Step Formation and Ferrimagnetism

In search of functional molecular materials and the study of their formation mechanism, we report the elucidation of a hierarchical step-by-step formation from monomer (Mn) to heptamer (Mn₇) to nonadecamer (Mn₁₉) satisfying the relation 1 + Σ_<i>n</i>6<i>n</i>, where <i>n</i> is the ring number of the Brucite structure using high-resolution electrospray ionization mass spectrometry (HRESI-MS). Three intermediate clusters, Mn₁₀, Mn₁₂, and Mn₁₄, were identified. Furthermore, the Mn₁₉ disc remains intact when dissolved in acetonitrile with a well-resolved general formula of [Mn₁₉­(<i>L</i>)_<i>x</i>­(OH)_<i>y</i>­(N₃)_{36–<i>x</i>−<i>y</i>}]²⁺ (<i>x</i> = 18, 17, 16; <i>y</i> = 8, 7, 6; H<i>L</i> = 1-(hydroxy­methyl)-3,5-dimethylpyrazole) indicating progressive exchange of N₃^– for OH^–. The high symmetry (<i>R</i>-3) Mn₁₉ crystal structure consists of a well-ordered discotic motif where the peripheral organic ligands form a double calix housing the anions and solvent molecules. From the formula and valence bond sums, the charge state is mixed-valent, [Mn^II₁₅Mn^III₄]. Its magnetic properties and electrochemistry have been studied. It behaves as a ferrimagnet below 40 K and has a coercive field of 2.7 kOe at 1.8 K, which can be possible by either weak exchange between clusters through the anions and solvents or through dipolar interaction through space as confirmed by the lack of ordering in frozen CH₃CN. The moment of nearly 50 Nμ_B suggests Mn^II–Mn^II and Mn^III–Mn^III are ferromagnetically coupled while Mn^II–Mn^III is antiferromagnetic which is likely if the Mn^III are centrally placed in the cluster. This compound displays the rare occurrence of magnetic ordering from nonconnected high-spin molecules