Efficient Simmons–Smith cyclopropanation with Zn/Cu and CH2I2

An appropriate solvent to perform the original Simmons–Smith reaction was reinvestigated. Among available solvents, cyclopentyl methyl ether (CPME), a recently commercialized ethereal solvent, was found to be the best so far. Compared with Et₂O under reflux – the commonest conditions – reaction completion in CPME at 50 °C was about 10 times faster. The product yields and selectivities were mostly identical to those with Et₂O, but were better in some cases; e.g. 13–56% with 2‐cyclohexenol. The good performance of CPME should be mainly due to its moderate polarity and high boiling point. Copyright © 2012 John Wiley & Sons, Ltd.     

Phases in the Al–Yb–Zn system between 25 and 50 at% ytterbium

Phases YbZn_1−xAl_x, YbZn_2−xAl_x and YbZn_3−xAl_x were studied by electron microprobe analysis and X-ray single crystal and powder methods. The compound YbZn_0.8Al_0.2 crystallizes with the CsCl-type, a=3.635(2) Å. Four phases were investigated by single crystal X-ray diffraction: YbZn_0.996(6)Al_1.004(6), MgNi₂-type, P6₃/mmc, a=5.573(1), c=18.051(3) Å, Z=8, wR2=0.040 and YbZn_0.88(3)Al_1.12(3), MgCu₂-type, , a=7.860(2) Å, Z=8, wR2=0.060, both showing mixed Zn/Al occupancy; YbZn_2.50(1)Al_0.50(1), CeNi₃-type, P6₃/mmc, a=5.496(1), c=17.336(2) Å, Z=6, wR2=0.036 and YbZn_1.92(2)Al_1.08(2), PuNi₃- or NbBe₃-type, , a=5.499(1), c=26.134(5) Å, Z=9, wR2=0.053, where the zinc atoms are ordered in the CaCu₅ segment, while share the sites with aluminium in the Laves phase segment. In the pseudobinary section YbZn_2−xAl_x four structures occur in sequence with increasing the electron concentration: CeCu₂ or KHg₂ (x=0–0.3), MgZn₂ (x=0.33–0.54), MgNi₂ (x=0.68–1.01) and MgCu₂ (x=1.12–2). This sequence agrees with the results of first-principles calculations, already reported in the literature for other similar series. In the YbZn_3−xAl_x section CeNi₃-type compounds occur with x=0.40–0.88 followed by PuNi₃-type compounds with x=0.92–1.10. The stability ranges of these phases are related to the valence electron concentration.     

A heterotrimetallic Cu–Co–Zn complex with the 2,2′‐iminodiethanol ligand

The crystal structure of the title compound, triacetato‐1κO;3κ⁴O,O′‐(2,2′‐imino­diethanol)‐1κ³O,N,O′‐bis­(μ‐2,2′‐iminodi­ethanol­ato)‐1κ²O:2κ⁶O,N,O′:3κ²O′‐cobalt(III)copper(II)zinc(II), [CoCuZn(C₄H₉NO₂)₂(C₂H₃O₂)₃(C₄H₁₁NO₂)], shows a mol­ecule with a triangular three‐metal core. The metal sites were refined with full occupancies, but the possibility that the Zn and Cu positions are actually mixed Cu/Zn sites cannot be excluded. The inter­metallic Cu⋯Co and Co⋯Zn distances are 2.924 (3) and 2.906 (3) Å, respectively. The neutral mol­ecules are held together by N—H⋯O hydrogen bonds involving amine groups from the 2,2′‐iminodiethanol ligands and acetate groups to build two‐dimensional layers.     

Electrochemical Properties of Yolk–Shell‐Structured Zn–Fe–S Multicomponent Sulfide Materials with a 1:2 Zn/Fe Molar Ratio

Yolk–shell‐structured Zn–Fe–S multicomponent sulfide materials with a 1:2 Zn/Fe molar ratio were prepared applying a sulfidation process to ZnFe₂O₄ yolk–shell powders. The Zn–Fe–S powders had mixed sphalerite (Zn,Fe)S and hexagonal FeS crystal structures. The discharge capacities of the Zn–Fe–S powders sulfidated at 350 °C at a constant current density of 500 mA g^?1 for the first, second, and fiftieth cycles were 1098, 912, and 913 mA h g^?1, respectively. The powders exhibited a high discharge capacity of 602 mA h g^?1 even at the high current density of 10 A g^?1. The synergistic effect of yolk–shell structure and multicomponent composition improved the electrochemical properties of Zn–Fe–S powders.     

New Phosphides La5Zn2−xP6 and Ce5Zn2−xP6 – the n = 4 Members of the REZn2P2·n(REP) Series

The new phosphides La₅Zn_2?xP₆ and Ce₅Zn_2?xP₆ were synthesized from the rare earth metals, LaZn and CeZn precursor compounds, Zn, and red phosphorous in NaCl/KCl salt fluxes. They crystallize with a new rhombohedral structure type: , Z = 3, a = 422.11(6), c = 6220(1) pm, wR2 = 0.0369, 356 F² values, 23 variables for La₅Zn_1.69P₆ and a = 417.05(6), c = 6162(1), wR2 = 0.0343, 286 F² values, 23 variables for Ce₅Zn_1.75P₆. The P^3? phosphide anions show an h²c⁴ stacking sequence in which the RE³⁺ and Zn²⁺ cations fill 5/6 and 1/6 of the octahedral and tetrahedral voids in an ordered manner, respectively, leading to a layer of condensed ZnP₄ tetrahedra and quintupled layers of condensed REP₆ octahedra. The structures of La₅Zn_2?xP₆ and Ce₅Zn_2?xP₆ belong to a larger family of phosphides which are intergrowth variants of CaAl₂Si₂ and NaCl related slabs according to REZn₂P₂·n(REP) with n = 4 for the present phosphides.     

(Zn1-xMnx)C2O4·2H2O在空气中的热分解动力学研究

用热分析（TG-DTG/DTA）、X射线衍射（XRD）技术和透射电镜（TEM）研究了固态物质Zn_1-xMn_xC₂O₄•2H₂O在空气中热分解的过程。热分析结果表明，Zn_1-xMn_xC₂O₄•2H₂O在空气中分两步分解，其失重率与理论计算失重率相吻合。 XRD和TEM结果表明，Zn_1-xMn_xC₂O₄•2H₂O分解的最终产物为Zn_1-xMn_xO,其颗粒大小约为10-13 nm。在非等温条件下对Zn_1-xMn_xC₂O₄•2H₂O的热分解动力学进行了分析。用Friedman法和Flynn-Wall-Ozawa(FWO)法求取了分解过程的活化能E，并用多元线性回归给出了可能的机理函数。Zn_1-xMn_xC₂O₄•2H₂O两步热分解的活化能分别为155.7513 kJ/mol 和215.9397 kJ/mol。     

Structural Effects of Cu/Zn Substitution in the Malachite–Rosasite System

Synthetic zincian malachite samples (Cu_1–xZn_x)₂(OH)₂CO₃ with x = 0, 0.1, 0.2 and 0.3 were characterized by powder X‐ray diffraction and optical spectroscopy. The XRD patterns of the samples up to x = 0.2 indicate single phase materials with an approximately linear dependence of the refined lattice parameters on the zinc content. In contrast, the sample with a nominal zinc content x = 0.3 shows the formation of a small amount of aurichalcite (Zn,Cu)₅(OH)₆(CO₃)₂ as an additional phase. Based on the lattice parameter variations, the zinc content of the zincian malachite component in this sample is estimated to be x ≈? 0.27, which seems to represent the maximum possible substitution in zincian malachite under the synthesis conditions applied. The results are discussed in relation to preparation of Cu/ZnO catalysts and the crystal structures of the minerals malachite and rosasite. One striking difference between these two structurally closely related phases is the orientation of the Jahn–Teller elongated axes of the CuO₆ octahedra in the unit cell, which seems to be correlated with the placement of the monoclinic β angle. The structural and chemical relationship between these crystallographically distinct phases is discussed using a hypothetical intermediate Zn₂(OH)₂CO₃ phase of higher orthorhombic symmetry. In addition to the crystallographic analysis, optical spectroscopy proves to be a useful tool for estimation of the Cu:Zn ratio in (Cu_1–xZn_x)₂(OH)₂CO₃ samples.     

Zn/Mn–MOFs with `S‐shaped' packing modes

Two novel polymers exhibiting metal–organic frameworks (MOFs) have been synthesized by the combination of a metal ion with a benzene‐1,3,5‐tricarboxylate ligand (BTC) and 1,10‐phenanthroline (phen) under hydrothermal conditions. The first compound, poly[[(μ₄‐benzene‐1,3,5‐tricarboxylato‐κ⁴O:O′:O′′:O′′′)(μ‐hydroxido‐κ²O:O)bis(1,10‐phenanthroline‐κ²N,N′)dizinc(II)] 0.32‐hydrate], {[Zn₂(C₉H₃O₆)(OH)(C₁₂H₈N₂)₂]·0.32H₂O}_n, denoted Zn–MOF, forms a two‐dimensional network in which a binuclear Zn₂ cluster serves as a 3‐connecting node; the BTC trianion also acts as a 3‐connecting centre. The overall topology is that of a 6³ net. The phen ligands serve as appendages to the network and interdigitate with phen ligands belonging to adjacent parallel sheets. The second compound, poly[[(μ₆‐benzene‐1,3,5‐tricarboxylato‐κ⁷O¹,O^1′:O¹:O³:O^3′:O⁵:O^5′)(μ₃‐hydroxido‐κ²O:O:O)(1,10‐phenanthroline‐κ²N,N′)dimanganese(II)] 1.26‐hydrate], {[Mn₂(C₉H₃O₆)(OH)(C₁₂H₈N₂)]·1.26H₂O}_n, denoted Mn–MOF, exists as a three‐dimensional network in which an Mn₄ cluster serves as a 6‐connecting unit, while the BTC trianion again plays the role of a 3‐connecting centre. The overall topology is that of the rutile net. Phen ligands act as appendages to the network and form the `S‐shaped' packing mode.     

Zn‐rich Zincides of the Ternary System Ca–Mg–Zn: Synthesis,Crystal structure,Chemical Bonding

In the course of a study on the role of magnesium in polar zincides of the heavier alkaline‐earth elements, three intermetallic phases of the ternary system Ca–Mg–Zn were synthesized from melts of the elements and their structures were determined by means of single‐crystal X‐ray data. Starting from the binary zincide CaZn₁₁, the phase width of the BaCd₁₁‐type structure reaches up to the fully ordered stoichiometric compound CaMgZn₁₀ [tI48, space group I4₁/amd, a = 1082.66(6), c = 688.95(5) pm, Z = 4, R₁ = 0.0239]. The new compound CaMgZn₅ (oP28, space group Pnma, a = 867.48(3), b = 530.37(5), c = 1104.45(9) pm, Z = 4, R₁ = 0.0385) crystallizes in the CeCu₆‐type structure, exhibits no Mg/Zn phase width and has no binary border equivalent in the system Ca–Mg–Zn. Similar to the situation in CaMgZn₁₀, one M position of the aristotype has a slightly larger coordination sphere (CN = 14) and is accordingly occupied by the larger Mg atoms. The third phase, Ca_2+xMg_6–x–yZn_15+y (hP92, space group P6₃/mmc, a = 1476.00(5), c = 881.01(4) pm, Z = 4, R₁ = 0.0399 for Ca_2.67Mg_5.18Zn_15.15) forms the hexagonal Sm₃Mg₁₃Zn₃₀‐type structure also known as μ‐MgZnRE or S phase. A small phase width (x = 0–0.67; y = 0–0.58) is due to the slightly variable Ca or Zn content of the two Mg positions. The structure is described as an intergrowth of the hexagonal MgZn₂ Laves phase and the CaZn₂ structure (KHg₂‐type). All compounds exhibit strong Zn–Zn and polar Mg–Zn covalent bonds, which are visible in the calculated electron density maps. Their structures are thus herein described using the full space tilings of [Zn₄] and [MgZn₃] tetrahedra, which are fused to polyanions consisting of tetrahedra stars, icosahedra segments etc. and the large (CN = 18–22) Ca cation coordination polyhedra. Pseudo bandgaps apparent in the tDOS are compatible with the narrow v.e./M ranges observed for other isotypic members of the three structure types.     

Separation of tryptic peptides of native and glycated BSA using open‐tubular CEC with salophene–lanthanide–Zn2+ complex as stationary phase

Open‐tubular CEC (OT‐CEC) with a new stationary phase, salophene–lanthanide–Zn²⁺ complex, has been applied to the separation of tryptic peptides of native BSA and BSA glycated by glucose and ribose. Glycation of proteins (non‐enzymatic modification by sugars) significantly affects their properties and it is of great importance from a physiological point of view. Separation of tryptic peptides of glycated BSA by CZE was poor because of their strong adsorption to the bare fused silica capillary. An improved separation of tryptic peptides of both native and glycated BSA was achieved by OT‐CEC in the fused silica capillary non‐covalently coated with salophene–lanthanide–Zn²⁺ complex, which suppressed the adsorption of peptides to the capillary and via specific interactions with some (glyco)peptides enhanced selectivity of the separation. Significant differences have been found in OT‐CEC analyses of tryptic hydrolysates of native and glycated BSA. In OT‐CEC‐UV profile of tryptic peptides of native BSA, 44 peaks could be resolved, whereas a reduced number of 38 peaks were observed in the profile of tryptic peptides of glucose‐glycated BSA and only 30 peaks were found in the case of ribose‐glycated BSA. The developed OT‐CEC can be potentially used for monitoring of protein glycation.     

Kinetic studies of polymerization of propylene with active TiCl3–Zn(C2H5)2

In order to elucidate the structure of the Ziegler-Natta polymerization center, we have carried out some kinetic studies on the polymerization of propylene with active TiCl₃—Zn(C₂H₅)₂ in the temperature range of 25–56°C. and the Zn(C₂H₅)₂ concentration range of 4 × 10^?3–8 × 10^?2 mole/1., and compared the results with those obtained with active TiCl₃—Al(C₂H₅)₃. The following differences were found: (1) the activation energy of the stationary rate of polymerization is 6.5 kcal/mole with Zn(C₂H₅)₂ and 13.8 kcal./mole with Al(C₂H₅)₃; (2) the growth rate of the polymer chains with Zn(C₂H₅)₂ is about times slower at 43.5°C.; and (3) the polymerization centers formed with Zn(C₂H₅)₂ are more unstable. It can be concluded that the structure of the polymerization center with Zn(C₂H₅)₂ is different from that with Al(C₂H₅)₃.     

Neue Alkalimetall‐Koordinationen durch chelatisierende Siloxazaneinheiten in Verbindungen der Formel [X–N–SiMe2–O–SiMe2–N–X]2M4

New Alkali Metal Coordinations by Chelating Siloxazane Units within Molecules of the General Formula [X–N–SiMe₂–O–SiMe₂–N–X]₂M₄ New solvent free alkali metal amides with Si–O–Si bridges of the general formula [X–N–SiMe₂–O–SiMe₂–N–X]₂M₄ (X = ^tBu ( 1 ), SiMe₃ ( 2 ), SiMe₂^tBu ( 3 ) with M = Li; X = ^tBu ( 4 ), SiMe₃ ( 5 ) with M = Na; X = ^tBu mit M = K, Li ( 6 )) have been synthesised and characterised by spectroscopic means. X‐ray structure analyses of the six metal derivatives reveal a common structural principle: the four metal atoms within the molecules are incorporated between two molecular halfs and form the bonding links between the two parts. The central molecular skeleton of the molecular halfs consists of a zig‐zag chain N–Si–O–Si–N. This chain is connected to the second one either ideally or approximately by S₄ (4) symmetry. The point symmetries within the crystal are either S₄ (4) (compounds 2 and 4 ), C₂ (2) (compound 6 ), and C₁ (1) (compounds 3 and 5 ). Compound 1 is special in different aspects: the molecule has the high crystallographic point symmetry D_2d (4m2) and the lithium atoms occupy split atom positions (in a similar way as in compound 2 ). The high symmetry of 1 as well as the split atom positions of the lithium atoms are a consequence of dynamics within the crystal.     

Zn8[P12N24]O2 – ein Nitridophosphat‐oxid mit Sodalith‐Struktur

Zn₈P₁₂N₂₄O₂ – a Nitridophosphate Oxide with Sodalite Structure The reaction between zinc metal and phosphorus nitride imide PN(NH) was investigated. Surprisingly, no Zn₆P₁₂N₂₄ was formed as assumed in former investigations but phase pure Zn₈[P₁₂N₂₄]O₂ ( (Nr. 217), a = 8.2422(2) Å; Z = 1) was obtained due to contamination by a small amount of oxygen. The existence of Zn₈[P₁₂N₂₄]O₂ was formerly supposed, but neither its crystal structure nor its exact composition have been unequivocally reported so far. The stoichiometric formula was deducted from elemental analyses, XANES spectroscopy at the phosphorus K‐threshold and IR‐spectroscopy using the crystallographic results of electron diffraction, X‐ray powder diffraction and solid‐state NMR spectroscopy. Zn₈[P₁₂N₂₄]O₂ adopts the sodalite structure type and is thus isotypic with Zn₈[P₁₂N₂₄]X₂ with X = S, Se, Te and Zn₈[B₁₂O₂₄]O₂.     

Disupersilylsilane R*2, Disupersilyldisilane R*2XSi–SiX3 und Tetrasupersilyltetrasilane R*2XSi–SiX2–SiX2–SiXR*2

Compounds of Silicon. 140. Sterical Overloaded Compounds of Silicon. 24. Disupersilylsilanes R*₂SiX₂, Disupersilyldisilanes R*₂XSi–SiX₃, and Tetrasupersilyltetrasilanes R*₂XSi–SiX₂–SiX₂–SiXR*₂ Supersilylsilanes R*₂SiX₂, disupersilyldisilanes R*₂XSi–SiX₃ and tetrasupersilyltetrasilanes R*₂XSi–SiX₂–SiX₂–SiXR*₂ (R* = supersilyl = SitBu₃; X = H, Me, Ph, Hal, OH, OTf) are prepared in organic solvents (i) by reactions of supersilylhalosilanes R*X₂SiHal with supersilyl sodium NaR* (Hal/R* exchange), (ii) by reactions of halosilanes X₃SiHal with silanides NaSiXR*₂ (Hal/SiXR*₂ exchange), (iii) by dehalogenations of disupersilylhalodisilanes R*₂XSi–SiX₂Hal with Na, (iv) by insertions of supersilylsilylenes R*XSi into the NaSi‐bond of supersilylsodium NaR*, (v) by reactions of disupersilylated halosilanes and ‐disilanes R*₂XSiHal and R*₂XSi–SiX₂Hal with H^– (Hal/H exchange), (vi) by reactions of the title silanes (X = H) with halogens Hal₂ (H/Hal exchange), (vii) by reactions of the title silanes (X = Hal) first with Na (Hal/Na exchange), then with agents for protonation (Na/H exchange) or halogenation (Na/Hal exchange), (viii) by reactions of the title silanes (X = Hal) with nucleophiles like F^–, H₂O (Hal/F or Hal/OH exchange) or (ix) by reactions of the title silanes (X = H) with strong acids like HOTf (H/OTf exchange). The colorless compounds are characterized by IR, NMR and X‐ray structure analyses (structures of R*₂SiX₂ with X = H, F, Cl and R*₂HSi–SiHX–SiHX–SiHR*₂ with X = H, Br). They may thermolize under formation of silylenes (e. g. R*₂SiX₂ → R*X + R*SiX) and are normally stable for hydrolysis. For other reactions confer preparation of the title silanes (i–ix).     

The Zn2+ salt of pamidronate: a role for water in the metal–cation binding properties of bis­phospho­nates

Pamidronate (3‐ammonium‐1‐hydroxy­propyl­idene‐1,1‐bis­phos­pho­nate) is used clinically in the treatment of diseases affecting bone tissue. In the salt zinc pamidronate dihydrate, Zn²⁺·2C₃H₁₀NO₇P₂⁻·2H₂O, pamidronate is a zwitterion with an overall charge of −1. The carbon chain adopts a trans conformation, separating maximally the positively charged N atom from the negative phospho­nate groups. The Zn²⁺ ion lies on an inversion center and is surrounded by a sixfold coordination sphere provided by two bidentate chelating zwitterions and two water mol­ecules. The bidentate O⋯Zn⋯O bond angle is 92.70 (7)°, while the O⋯O bite distance is 3.018 (3) Å.     

Mono- and poly-ligated complexes of Zn2+: An ab initio analysis of the metal–ligand interaction energy

Detailed investigation of the binding energetics of Zn²⁺ to biologically relevant model ligands has been performed by large basis set restricted Hartree-Fock computations. This list includes neutral and anionic ligands that model the sidechains of the amino acid residues of proteins as well as those involved in binding to the metal during enzymatic activation: water, formaldehyde, formamide, imadazole, methylthiol, and the formate, hydroxyl, methoxy, methylthiolate anions. The decomposition of the intermolecular interaction energy into its components (Coulomb, exchange, polarization, and charge transfer) has been done within the frozen fragment reduced variational space procedure (RVS) developed by Stevens and Fink [W. J. Stevens and W. H. Fink, Chem. Phys. Lett., 139 , 15 (1987)]. The use of the RVS procedure was dictated by the very large magnitudes of the second-order interaction energy terms in the divalent cation complexes and the need to obtain polarization and charge-transfer contributions in a variational sense. The behavior of the interaction energy with radial and angular variation of the approach of the metal to the ligand is explored. In addition, the nonadditive behavior of polyligated complexes is studied for water and formate. This will also provide the data for a subsequent fit to a molecular mechanics procedure that considers the second-order interactions. © 1995 by John Wiley & Sons, Inc.     

DFT study on the hydrogen bonds of phenol–cyclohexanone and phenol–H2O2 in the Baeyer–Villiger oxidation

Hydrogen bonds of phenol–cyclohexanone and phenol–H₂O₂ in the studied Baeyer–Villiger (B–V) oxidation have been investigated by HF, B3LYP, and MP2 methods with various basis sets. The accurate single‐point energies were performed using CCSD(T)/6‐31+G(d,p) and CCSD(T)/aug‐cc‐pVDZ on the optimized geometries of MP2/6‐31+G(d,p). It has been confirmed that B3LYP/6‐31+G(d,p) could be used to study such hydrogen bonds. Energetic analysis of complexes was carried out using the Xantheas method with BSSE corrected by CP method. Orbital energy order (ε) illuminated that phenol with good hydrogen donor‐acceptor property can interact with cyclohexanone or H₂O₂ to form hydrogen bound complexes, and the binding energies (BE) range from ?4.38 to ?14.06 kcal mol^?1. NBO analysis indicated that the redistribution of atomic charges in the complexes facilitated nucleophilic attack of H₂O₂ on cyclohexanone. The calculated results match remarkably well with the experimental phenomena. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

N–H(N)…S Bonding in Tetrahedral [Zn(NCS)2L]0 Complexes (L = MexH2–xN(CH2)2NH2–yMey,x, y = 0 – 2)

The crystal structures of uncharged tetrahedral dithiocyanato zinc complexes with N-methylated ethylenediamines have been determined with a view to a study of intermolecular hydrogen-bonding interactions in these compounds. It is found that the H(N) hydrogen atoms are exhaustively engaged in N–H(N) … S bonds. The majority of these bonds are branched (bifurcated or trifurcated), and the hydrogen-bond systems they form all contain one of the two characteristic primitive core motifs: either a discrete centrosymmetric […S…H…]₂ dimer or an infinite […S…H…]_∞ helix about a 2₁ or pseudo-2₁ axis. The hydrogen bonding is analyzed in detail, with particular attention to the existence of correlations between the N–H(N)–S angles and the H(N) … S distances as well as between the corresponding N–H(N)–S/H(N)…S pairs in the bifurcated N–H(N)…2 S bonds.