Search results for "LEM"

High-Pressure Behavior of Nickel Sulfate Monohydrate: Isothermal Compressibility, Structural Polymorphism, and Transition Pathway

2020

Single crystals of synthetic nickel sulfate monohydrate, α-NiSO4·H2O (space-group symmetry C2/c at ambient conditions), were subject to high-pressure behavior investigations in a diamond-anvil cell up to 10.8 GPa. By means of subtle spectral changes in Raman spectra recorded at 298 K on isothermal compression, two discontinuities were identified at 2.47(1) and 6.5(5) GPa. Both transitions turn out to be apparently second order in character, as deduced from the continuous evolution of unit-cell volumes determined from single-crystal X-ray diffraction. The first structural transition from α- to β-NiSO4·H2O is an obvious ferroelastic C2/c–P1̅ transition. It is purely displacive from a structur…

Sequential Nucleophilic−Electrophilic Reactions Selectively Produce Isomerically Pure Nona‐ B ‐Substituted o ‐Carborane Derivatives

2003

Nine equal substituents on the intensively studied o-carborane have been obtained for the first time by a combined nucleophilic-electrophilic reaction sequence. Iodine and methyl groups have been introduced to prove the generality of the method. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Chemical shift reagents in the study of polycyclic alcohols IX—1H NMR spectra of myrtenol and some other primary alcohols

1974

Structure proof of (—)-myrtenol, 3-cyclopentenyl-1-methanol and 5-norbornene-2-endo-methanol has been obtained from their proton magnetic resonance spectra in carbon tetrachloride containing different added amounts of tris(dipivaloylmethanato)europium. For each alcohol, a 1:1 complex structure with Eu(dpm)3 could be computed, in which the calculated pseudocontact shift effects on all skeleton protons of the ring system were consistent with the observed shift effect values. A considerable contact contribution of opposite sign to that of the pseudocontact part of the effect could be estimated for the methylene protons of the CH2OH group.

Oxotris(oxalate)niobate(V): An oxalate delivery agent in the design of building blocks

2018

This work concerns the oxalate delivery process that occurs when using (NH4)3[NbO(C2O4)3]·6H2O as a suitable oxalate source in the synthesis of two compounds, [Cu(dmphen)(C2O4)(H2O)] (1) and [{Cu(dmphen)(CH3OH)}2(μ-C2O4)](ClO4)2 (2) (dmphen = 2,9-dimethyl-1,10-phenanthroline). {[Fe{HB(pz)3}(CN)2(μ-CN)]2[{Cu(dmphen)}2(μ-C2O4)]}∙xCH3OH (3) (2.0 ≤ x ≤ 2.4) was obtained by reacting 2 and PPh4[Fe{HB(pz)3}(CN)3]∙H2O [ = tetraphenylphosphonium and = tris(pyrazolyl)borate]. Crystal structures of 1–3 have been determined by single-crystal X-ray diffraction experiments: 1 is a mononuclear trigonal bipyramidal copper(II) species, 2 is a centrosymmetric oxalato-bridged dicopper(II) complex, and 3 consi…

Mixed phenoxo and azido bridged dinuclear nickel(II) and copper(II) compounds with N,N,O-donor schiff bases: Synthesis, structure, DNA binding, DFT a…

2019

Abstract Two dinuclear complexes, µ-phenoxo, µ1,1-azido bridged [Ni2(L)2(µ1,1-N3)(N3)(CH3OH)] (1) and µ-phenoxo, µ1,1-azido bridged [Cu2(L)2(µ1,1-N3)(N3)] (2) bearing HL as a blocking co-ligand produced by the 1:1 condensation of N-methyl 1,3 propanediamine with o-vanillin have been synthesized and successfully characterized by elemental analyses, IR and electronic spectroscopy, single-crystal X-ray diffraction for 1 and DFT optimization for 2. X-ray crystal structure discloses that the asymmetric unit of 1 consists of two nickel(II) ions exhibiting a six-coordinate octahedral coordination with µ-phenoxo, µ1,1-azido bridging dimeric structure. The DFT optimization of 2 reveals the five-coor…

Synthesis, molecular structures and EPR spectra of the paramagnetic cuboidal clusters with Mo3S4Ga cores

2017

Electron precise [Mo3(l3-S)(l-S)3(diphos)3Br3]Br (diphos = dppe, dmpe) incomplete cuboidal clusters with six cluster skeletal electrons (CSE) were converted into paramagnetic cuboidal [Mo3(GaBr)(l3-S)4- (diphos)3Br3] clusters by treatment with elemental Ga. The new heterobimetallic complexes with nine CSE possess a doublet ground state with the unpaired electron density delocalized over the three molybdenum atoms.

Structurally characterized dipalladium(ii)-oxamate metallacyclophanes as efficient catalysts for sustainable Heck and Suzuki reactions in ionic liqui…

2018

A new generation of dipalladium-oxamate metallacyclophanes of formulas (n-NBu4)4 [Pd2(ppba)2] (1), (n-NBu4)4[Pd2(dpvba)2] (2), (n-NBu4)4[Pd2(dpazba)2] (3), (n-NBu4)4[Pd2(dpeba)2] (4) and (n-NBu4)4[Pd2(tpeba)2] (5) [n-NBu4+ = tetra-n-butylammonium cation, H4ppba = N,N′-1,4-phenylenebis(oxamic acid), H4dpvba = N,N′-4,4′-diphenylethenebis(oxamic acid), H4dpazba = N,N′-4,4′-diphenylazobis(oxamic acid), H4dpeba = N,N′-4,4′-diphenylethynebis(oxamic acid) and H4tpeba = N,N′-1,4-di(4-phenylethynyl)phenylenebis(oxamic acid)] was prepared. The crystal structure of the solvated species of 2–4, namely (n-NBu4)4[Pd2(dpvba)2]·6MeOH·2Et2O (2a), (n-NBu4)4[Pd2(dpazba)2]·8MeOH (3a), and (n-NBu4)2[Pd2(dpeba)2…

Versatile behavior of conjugated diynes with zirconocene reactive species

2008

Thermal decomposition of Cp2ZrPh2 in the presence of the buta-1,3-diynes RC≡CC≡CR (R = Ph, SiMe3) can lead to seven- or five-membered metallacycles. In both cases a stable benzo-fused seven-membered zirconacyclocumulene arising from a 2-fold insertion of the triple bonds of the dialkyne in the in situ generated zirconocene benzyne is formed. In the case of Me3SiC≡CC≡CSiMe3 a second minor complex is isolated: a 3-alkynyl-substituted zirconaindene arising from a β monoinsertion of one acetylenic function of the conjugated diyne in the zirconocene benzyne. No stable 2-alkynyl-substituted zirconacycle was isolated. This α monoinsertion complex is an intermediate in the exchange of the metalated…

Automated Diffraction Tomography for the Structure Elucidation of Twinned, Sub-micrometer Crystals of a Highly Porous, Catalytically Active Bismuth M…

2012

Stepwise Construction of Heterobimetallic Cages by an Extended Molecular Library Approach.

2017

Two novel heterobimetallic complexes, a trigonal-bipyramidal and a cubic one, have been synthesized and characterized using the same C3-symmetric metalloligand, prepared by a simple subcomponent self-assembly strategy. Adopting the molecular library approach, we chose a mononuclear, preorganized iron(II) complex as the metalloligand capable of self-assembly into a trigonal-bipyramidal or a cubic aggregate upon coordination to cis-protected C2-symmetric palladium(II) or unprotected tetravalent palladium(II) ions, respectively. The trigonal-bipyramidal complex was characterized by NMR and UV–vis spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and single-crystal X-ray diffrac…