Carbon Nitride as a Ligand: Selective Hydrogenation of Terminal Alkenes Using [(η5-C5Me5)IrCl(g-C3N4-κ2N,N’)]Cl

Anchoring a homogeneous catalyst onto a heterogeneous support facilitates separation of the product from the catalyst, and catalyst-substrate interactions can also modify reactivity. Herein we describe the synthesis of composite materials comprising carbon nitride (g-C₃N₄) as the heterogeneous support and the well-established homogeneous catalyst moiety [Cp*IrCl]⁺ (where Cp*=η⁵-C₅Me₅), commonly used for catalytic hydrogenation. Coordination of [Cp*IrCl]⁺ to g-C₃N₄ occurs directly at exposed edge sites with a κ²N,N’ binding motif, leading to a primary inner coordination sphere analogous to known homogeneous complexes of the general class [Cp*IrCl(NN-κ²N,N’)]⁺ (where N,N’=a bidentate nitrogen ligand). Hydrogenation of unsaturated substrates using the composite catalyst is selective for terminal alkenes, which is attributed to the restricted steric environment of the outer coordination sphere at the edge-sites of g-C₃N₄.     

The Na⋅⋅⋅B Bond in NaBH3−: A Different Type of Bond

A newly introduced Na−B bond in NaBH₃⁻ has been a challenge for the chemical bonding community. Here, a series of MBH₃⁻ (M=Li, Na, K) species and NaB(CN)₃⁻ are studied within the context of quantum chemical topology approaches. The analyses suggest that M–B interaction cannot be classified as an ordinary covalent, dative, or even simple ionic interaction. The interactions are controlled by coulombic forces between the metals and the substituents on boron, for example, H or CN, more than the direct M–B interaction. On the other hand, while the characteristics of the (3, −1) critical points of the bonds are comparable to weak hydrogen bonds, not covalent bonds, the metal and boron share a substantial sum of electrons. To the best of the author's knowledge, the characteristics of these bonds are unprecedented among known molecules. Considering all paradoxical properties of these bonds, they are herein described as ionic-enforced covalent bonds.     

Synthesis and Crystal Structure of a One-dimensional Infinite Chain Organotin Complex [(n-Bu)_3Sn(OCOC_5H_4NO)]_n

1 INTRODUCTION Organotin esters of carboxylic acid are widely used as biocides and fungicides and as homogeneous cata- lysts in industry[1~3]. In recent years, the pharmaceu- tical properties of carboxylic acid have been investi- gated for the antitumour activity[4~6]. In general, bio- cidcal activities of organotin complexes are greatly influenced by the molecular structures and coordina- tion numbers of the tin atom[7, 8]. It is revealed that organotin complexes containing carboxylate l…     

The stereochemistry of glycolipids. A key for understanding membrane functions?

A Commentary on the paper ”Studies on liquid‐crystalline glycosides" by Volkmar Vill, Thomas Böcker, Joachim Thiem and Fred Fischer. First published in Liquid Crystals, 6, 349‐356 (1989).     

High-Pressure Synthesis of Metal–Inorganic Frameworks Hf4N20⋅N2, WN8⋅N2, and Os5N28⋅3 N2 with Polymeric Nitrogen Linkers

Polynitrides are intrinsically thermodynamically unstable at ambient conditions and require peculiar synthetic approaches. Now, a one-step synthesis of metal–inorganic frameworks Hf₄N₂₀⋅N₂, WN₈⋅N₂, and Os₅N₂₈⋅3 N₂ via direct reactions between elements in a diamond anvil cell at pressures exceeding 100 GPa is reported. The porous frameworks (Hf₄N₂₀, WN₈, and Os₅N₂₈) are built from transition-metal atoms linked either by polymeric polydiazenediyl (polyacetylene-like) nitrogen chains or through dinitrogen units. Triply bound dinitrogen molecules occupy channels of these frameworks. Owing to conjugated polydiazenediyl chains, these compounds exhibit metallic properties. The high-pressure reaction between Hf and N₂ also leads to a non-centrosymmetric polynitride Hf₂N₁₁ that features double-helix catena-poly[tetraz-1-ene-1,4-diyl] nitrogen chains [−N−N−N=N−]_∞.     

The thermal transformation of Na LiA zeolites. A new polymorph in the system Li2OAl2O3SiO2

High-temperature phase transformations of A zeolite with various degrees of exchange of Na⁺ with Li⁺ ions were investigated. An increase in the number of Li⁺ ions per unit cell accelerates the thermal transformation of the zeolite framework to the amorphous state. Above 730°C, four phases (carnegieite, nepheline, β-eucryptite, and a new phase—γ-eucryptite) were identified. Only γ- and β-eucryptite phases were obtained from pure LiA zeolite. γ-eucryptite is a new metastable polymorph in the system Li₂OAl₂O₃SiO₂. γ-eucryptite a₀ = 7.231(3)Å, b₀ = 10.270(6) Å, c₀ = 12.054(7) Å) is transformed to β-eucryptite (a₀ = 10.533(5) Å, c₀ = 11.148(5) Å) above 840°C.     

An Unprecedented 1D Zigzag Chain Alkaline Earth Metal Derivative {[Ba（DMF）3（H20）2][Ba（DMF）4]2（PzWl8O662）}n Containing Dawson Heteropolyanion

An unprecedented 1D zigzag chain alkaline earth metal derivative, {[Ba（DMF）3 （H20）2][Ba（DMF）412（P2W18O62）}n, （DMF=N, N-dimethyl formamide） containing Dawson hetero- polyanion has been successfully synthesized and characterized by X-ray crystallography. Two barium cations bridged by three DMF ligands in parallel combination with the Dawson-type heteropolyanion [P2W18O62]^6- and then the resulting subunits {[Ba（DMF）4]2（P2WlsO62）}^2＋ are alternately linked together via another [Ba（DMF）3（H2O）2]^2＋ ions, constructing a 1D zigzag chain architecture.     

Why are [P(C6H5)4](+)N3- and [As(C6H5)4](+)N3- ionic salts and Sb(C6H5)4N3 and Bi(C6H5)4N3 covalent solids? A theoretical study provides an unexpected answer

A recent crystallographic study has shown that, in the solid state, P(C(6)H(5))(4)N(3) and As(C(6)H(5))(4)N(3) have ionic [M(C(6)H(5))(4)](+)N(3)(-)-type structures, whereas Sb(C(6)H(5))(4)N(3) exists as a pentacoordinated covalent solid. Using the results from density functional theory, lattice energy (VBT) calculations, sublimation energy estimates, and Born-Fajans-Haber cycles, it is shown that the maximum coordination numbers of the central atom M, the lattice energies of the ionic solids, and the sublimation energies of the covalent solids have no or little influence on the nature of the solids. Unexpectedly, the main factor determining whether the covalent or ionic structures are energetically favored is the first ionization potential of [M(C(6)H(5))(4)]. The calculations show that at ambient temperature the ionic structure is favored for P(C(6)H(5))(4)N(3) and the covalent structures are favored for Sb(C(6)H(5))(4)N(3) and Bi(C(6)H(5))(4)N(3), while As(C(6)H(5))(4)N(3) presents a borderline case.     

钙钛矿结构荧光材料MZrO3:Eu3+,A (M=Ca2+, Ba2+; A=Li+, Na+, K+)的制备及其发光性质

Calcium and barium zirconate powders based upon CaZrO₃:Eu³⁺,A and BaZrO₃:Eu³⁺,A (A=Li⁺, Na⁺, K⁺) were prepared by combustion synthesis method and heating to ~1000℃ to improve crystallinity.The structure and morphology of materials were examined by X-ray diffraction (XRD) and scanningelectron microscopy (SEM). XRD results showed that CaZrO₃:Eu³⁺,A and BaZrO₃:Eu³⁺,A (A=Li⁺, Na⁺, K⁺) perovskites possessed orthorhombic and cubic structures, respectively. The morphologies of all powderswere very similar consisting of small, coagulated, cubical particles with narrow size distributions andsmooth and regular surfaces. The characteristic luminescences of Eu³⁺ ions in CaZrO₃:Eu³⁺,A (A=Li⁺, Na⁺, K⁺) lattices were present with strong emissions at 614 and 625 nm for ⁵D₀→⁷F₂ transitions with other weakeremissions observed at 575, 592, 655, and 701 nm corresponding to ⁵D₀→⁷F_n transitions (where n=0, 1, 3, 4 respectively). In BaZrO₃:Eu³⁺ both the ⁵D₀→⁷F₁ and ⁵D₀→⁷F₂ transitions at 595 and 613 nm were strong.Photoluminescence intensities of CaZrO₃:Eu³⁺ samples were higher than those of BaZrO₃:Eu³⁺ lattices. Thisremarkable increase of photoluminescence intensity (corresponding to ⁵D₀→⁷F_n transitions) was observedin CaZrO₃:Eu³⁺ and BaZrO₃:Eu³⁺ if co-doped with Li⁺ ions. An additional broad band composed of manypeaks between 440 to 575 nm was observed in BaZrO₃:Eu³⁺,,A samples. The intensity of this band wasgreatest in Li⁺ co-doped samples and lowest for K⁺ doped samples.     

Metal dimers as catalysts: IX. The catalysed reaction between [η5-C5H5)Fe(CO)2I] and group 15 donor ligands

The reaction between [η⁵-C₅H₅)Fe(CO)₂I] (I) and 1 equivalent of L (group 15 donor ligand) in the presence of catalysts (e.g. Pd/CaCO₃, PdO, [η⁵-C₅H₅)Fe(CO)₂]₂ (II)) yields [η⁵-C₅H₅)Fe(CO)(L)I] (phosphines, diphosphines, phosphite), [η⁵-C₅H₅)Fe(CO)₂L]I (phosphines) and [η⁵-C₅H₅)Fe(CO)(LL)]I (diphosphines). [η⁵-C₅H₅)Fe(CO)₂L]I can be converted into [η⁵-C₅H₅)Fe(CO)(L)I] in the presence of II. The reaction between [η⁵-C₅H₅)Fe(CO)(PMePh₂)I] or [η⁵-C₅H₅)Fe(CO)₂(PMePh₂)]I and PMePh₂ is also catalysed by II and yields in both instances [η⁵-C₅H₅)Fe(CO)(PMePh₂)₂]I. In the series of catalysed reactions the displacement sequence was found to be PMePh₂ > I⁻ > CO.     

Metal in organic synthesis. VI. The solvent effect on the hydrocarbonalkoxylation of propene promoted by a [PdCl2(PPh3)2]−PPh3 catalyst precursor

The hydrocarboalkoxylation of propene promoted by a [PdCl₂(PPh₃)₂]−PPh₃ catalyst precursor occurs (at 100 – 110 °C, P_CO 10 – 100 atm) with high selectivity towards the branched isomer when a solvent is added to the alkanol.The selectivity increases on increasing the solvent/alkanol ratio, or on increasing P_CO, or in the presence of LiCl, and decreases upon increasing the concentration of PPh₃. The results are discussed in terms of steric effects.The yield decreases on increasing the solvent/alkanol ratio, or on increasing the concentration of PPh₃, or upon decreasing P_CO. Primary or secondary alkanols show comparable reactivity; tertiary alkanols give poor yields. The yield can be improved in the presence of molecular hydrogen without affecting the regioselectivity.     

A New Class of Nucleoside Analogues. Synthesis of N. -Pyrimidinyl-and N9-Purinyl-4′-hydrqxy-3-(Hydsoxymethyl)butanes1 # 2

Interest in non-glycosidic derivatives of the nucleo-bases uracil, theymine, cytosine, adenine and guanine stems from their status as nucleoside analogues. It is noteworty in this connection that the anti-biotics aristeromycin³ and eritadenine⁴ consist of an adenine moiety linked, via N₉ -, to a cyclopentyl or a butiric acid derivative, respectively, in place of the conventional nucleoside sugars. A non-glycoaidic 5-fluorouracil derivative⁵ has been recently reported to be clinically effective in the treatment of Gastrointestinal cancer. In this communication the ficile synthesis of 4-hydroxy-3-(hydroxymethyl)butyl derivatives of the nucleobases (1) is described. These nucleoside analogues are characterized by the special feature that they incorporate two hydroxyl functions in a relationship corresponding to the 3′-and 5′-hydroxy groups of the 2-deodyribose Doiety. Phosphorylationj of the hydroxyl groups or their linkage via phosphodiester of the hydroxyl groups or their linkage via phosphodiester bridges should give nucleotide analogues or novel nucleic acid models. The latter molecular systems constitute a new class of potential anti-mitotic or anti-viral agents. One principle synthetic approach to compounds of general structure 1 was visualized via the intermediacy of 2-(hydroxymethyl) - 4-aminobutanol (2, ReH) which, acting as a common precursor, could be elaborated to the desired pyrimidine or purine derivative, via its amine function. The synthesis of amine 2 was achieved according to the reaction sequence described in Scheme I. Diethyl malonate was coupled with 2,2-dimethoxybromoethane, in presence of sodium ethoxide (EthoH, 170°, autoclave). The resulting diester (3) was reduced with LialH₄ to the corresponding diol (4), which was benzylated (NaH, C₆H₅CH₂Cl) to 5. When 5 was refluxed with NH₂OH.HCl in methanol for 30 min., a mixture of oximes 6a,b (syn- and anti-) and nitrile 7 was isolated. The latter mixture could be directly reduced with LiAlH₄ to amine 2,⁶ in high yield.     

A Highly Regioselective Iodoenoletherification of α-Allyl-β-ketoesters. A Convenient Route to 2-Alkyl-5-iodomethyl-3-methoxycarbonyl-4, 5-Dihydrofurans

A variety of α-allyl-β-ketoesters (1) containing two different double bonds, undergo highly regioselective iodoenoletherification to give the titled compound (2) in excellent yields.     

The transformation of 1,2,4-trimethylbenzene A probe reaction to monitor external surface modifications of HZSM-5?

The transformation of 1,2,4-trimethylbenzene is proposed as a new probe reaction to monitor the catalytic effects of inertisation of the external surface of HZSM-5. The external surface has been modified by coating ZSM-5 crystallites with an inert silicalite shell. At 723 K and a WHSV of 0.6 h⁻¹ it has been shown that the isomerisation products 1,2,3-trimethylbenzene and 1,3,5-trimethylbenzene reflect changes in external activity. The disproportionation products, 1,2,4,5-tetramethylbenzene and 1,2,3,5-tetramethylbenzene together are shown to indicate changes in overall activity and shape selective properties of the catalyst sample. The results correlate with those observed for the reaction of 1,3,5-triisopropylbenzene and n-hexane cracking.