Search results for "C [PolyI]"
showing 10 items of 30703 documents
A New LA ‐ ICP ‐ MS Method for Ti in Quartz: Implications and Application to High Pressure Rutile‐Quartz Veins from the Czech Erzgebirge
2016
Experimental determination of the pressure and temperature controls on Ti solubility in quartz provides a calibration of the Ti-in-quartz (TitaniQ) geothermometer applicable to geological conditions up to ~ 20 kbar. We present a new method for determining 48Ti mass fractions in quartz by LA-ICP-MS at the 1 μg g−1 level, relevant to quartz in HP-LT terranes. We suggest that natural quartz such as the low-CL rims of the Bishop Tuff quartz (determined by EPMA; 41 ± 2 μg g−1 Ti, 2s) is more suitable than NIST reference glasses as a reference material for low Ti mass fractions because matrix effects are limited, Ca isobaric interferences are avoided, and polyatomic interferences at mass 48 are i…
Phosphasalen group IV metal complexes: synthesis, characterization and ring opening polymerization of lactide.
2020
International audience; We report the synthesis of a series of Zr and Ti complexes bearing phosphasalen which differs from salen by the incorporation of two P atoms in the ligand backbone. The reaction of phosphasalen proligands (1a-1c)H2 with Zr(CH2Ph)4 led to different products depending on the nature of the N,N-linker in the ligand. In case of ethylene-linked phosphasalen, octahedral Zr complex 2a formed as a single stereoisomer in trans geometry. With the phenylene linker, it was shown by dynamic NMR spectroscopy that complex 2b exists as a mixture of trans and cis-β isomers in solution, both enantiomers (Δ and Λ) of the cis-β isomer being in fast equilibrium with respect to the NMR tim…
Electrochemical Fluorocyclization of N-Allylcarboxamides to 2-Oxazolines by Hypervalent Iodine Mediator
2018
A resource saving protocol for the synthesis of 5-fluoromethyl-2-oxazolines by using electrochemistry has been realized. Thereby, a hypervalent iodine species I(III) is generated by anodic oxidation in the presence of Et3N·5HF and mediates the cyclization of N-allylcarboxamide to 5-fluoromethyl-2-oxazoline. This method allows application to various substrates furnishing the 2-oxazolines with yields up to 68%. The protocol is easy to conduct under constant current conditions offering a sustainable alternative over conventional reagent-based pathways.
Cooperative N–H bond activation by amido-Ge(ii) cations
2020
N-heterocyclic carbene (NHC) and tertiary phosphine-stabilized germylium-ylidene cations, [R(L)Ge:]+, featuring tethered amido substituents at R have been synthesized via halide abstraction. Characterization in the solid state by X-ray crystallography shows these systems to be monomeric, featuring a two-coordinate C,N- or P,N-ligated germanium atom. The presence of the strongly Lewis acidic cationic germanium centre and proximal amide function allows for facile cleavage of N-H bonds in 1,2-fashion: the products resulting from reactions with carbazole feature a tethered secondary amine donor bound to a three-coordinate carbazolyl-GeII centre. In each case, addition of the components of the N…
Syntheses, Properties and Structures of [{(C 5 Me 5 ) 2 Nb} 2 NiTe 4 ] and [( t BuC 5 H 4 Nb) 2 Ni 5 Te 7 (Ph 2 PCH 2 PPh 2 ) 2 ]: The Quest for Tetr…
2007
The reaction of [Ni(COD) 2 ] with [Cp* 2 NbTe 2 H] (1; Cp * = η-C 5 Me 5 ) in the presence of Ph 2 PCH 2 PPh 2 (dppm) in boiling toluene gives black-violet [(Cp * 2 Nb) 2 NiTe 4 ] (3). If [Cp' 2 NbTe 2 H] (2; Cp' = tBuC 5 H 4 ) is used under similar conditions dark-brown [(Cp'Nb)2Ni5Te7(dppm)2] (4) is formed. The structures of 3 and 4 have been determined crystallographically. Complex 3 contains a severely distorted NiTe 4 tetrahedron to which two niobocene groups are coordinated. Density functional analysis of the electronic structure of the NiTe 4 building block shows that it is best described as an [Ni(η 2 -Te 2 ) 2 ] 2- fragment. The structure of 4 reveals the presence of two Ni 5 and T…
A Cationic Oligomer as an Organic Template for Direct Synthesis of Aluminosilicate ITH Zeolite
2020
There are a large number of zeolites, such as ITH, that cannot be prepared in the aluminosilicate form. Now, the successful synthesis of aluminosilicate ITH zeolite using a simple cationic oligomer as an organic template is presented. Key to the success is that the cationic oligomer has a strong complexation ability with aluminum species combined with a structural directing ability for the ITH structure similar to that of the conventional organic template. The aluminosilicate ITH zeolite has very high crystallinity, nanosheet-like crystal morphology, large surface area, fully four-coordinated Al species, and abundant acidic sites. Methanol-to-propylene (MTP) tests reveal that the Al-ITH zeo…
A study on stabilization of HHeF molecule upon complexation with Xe atoms
2004
In the present work, we computationally study energetic stabilization of HHeF by its complexation with Xe atoms. For the studied HHeF ��� Xen systems ðn ¼ 1–4; 6Þ, we found a large complexation-induced decrease of energy of HHeF with respect to its dissociation into atoms. As a working hypothesis, we assume that this stabilization effect continues for the larger systems (n > 6) as well. This suggests that dissociation of HHeF via the H–He stretching coordinate might be suppressed and its lifetime might be increased by inserting it into large Xe clusters or matrices. 2004 Elsevier B.V. All rights reserved.
Structural Tuning and Conformational Stability of Aromatic Oligoamide Foldamers
2017
A series of aromatic oligoamide foldamers with two or three pyridine-2,6-dicarboxamide units as their main folding motifs and varying aromatic building blocks as linkers have been synthetized to study the effects of the structural variation on the folding properties and conformational stability. Crystallographic studies showed that in the solid state the central linker unit either elongates the helices and more open S-shaped conformations, compresses the helices to more compact conformations or acts as a rigid spacer separating the pyridine-2,6-dicarboxamide units, which for their part add the predictability of the conformational properties. Multidimensional NMR studies showed that, even in…
An investigation of photo- and pressure-induced effects in a pair of isostructural two-dimensional spin-crossover framework materials
2014
International audience; Two new isostructural iron(II) spin-crossover (SCO) framework (SCOF) materials of the type [Fe(dpms)2 (NCX)2 ] (dpms=4,4'-dipyridylmethyl sulfide; X=S (SCOF-6(S)), X=Se (SCOF-6(Se))) have been synthesized. The 2D framework materials consist of undulating and interpenetrated rhomboid (4,4) nets. SCOF-6(S) displays an incomplete SCO transition with only approximately 30 % conversion of high-spin (HS) to low-spin iron(II) sites over the temperature range 300-4 K (T1/2 =75 K). In contrast, the NCSe(-) analogue, SCOF-6(Se), displays a complete SCO transition (T1/2 =135 K). Photomagnetic characterizations reveal quantitative light- induced excited spin-state trapping (LIES…
Synthesis of copper(II) and gold(III) bis(NHC)-pincer complexes
2016
Abstract CuII and AuIII chlorido complexes bearing the bis(NHC) carbazolide pincer ligand (bimca) were synthesized by transmetallation from the respective lithium complex [Li(bimca)] (NHC=N-heterocyclic carbene). In the case of copper, two different molecular structures were obtained depending on the copper source. With Cu(II) chloride the paramagnetic mononuclear [Cu(bimca)Cl] complex is formed and has been characterized by EPR spectroscopy and X-ray structure analysis, while copper(I) chloride leads under oxidation to a dinuclear structure in which two cationic [CuII(bimca)] moieties are bridged by one chlorido ligand. The positive charge is compensated by the [CuCl2]− counter ion, as pro…