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Thorsten Grb Gertraud Geiseler Klaus Harms Andreas Greiner Kurt Dehnicke 《无机化学与普通化学杂志》2002,628(1):217-221
Phosphoraneiminato Complexes of Zirconium: Crystal Structures of [ZrCl3(NPPh3)(HNPPh3)2] and [ZrCl2(NPPh3)2(HNPPh3)2] The phosphoraneiminato complexes [ZrCl3(NPPh3)(HNPPh3)2] ( 1 ) and [ZrCl2(NPPh3)2(HNPPh3)2] ( 2 ) have been obtained by reaction of [ZrCl4(THF)2] with [CsNPPh3]4 in THF solution to give colourless moisture sensitive crystals which are characterized by X‐ray structure determinations. [ZrCl3(NPPh3)(HNPPh3)2] ( 1 ): Space group P 1, Z = 2, lattice dimensions at 193 K: a = 1209.4(2); b = 1480.8(2); c = 1814.2(2) pm; α = 71.203(13)°, β = 71.216(13)°, γ = 74.401(13)°; R = 0.0476. The zirconium atom of 1 is oktahedrally coordinated by the three chlorine atoms in meridional arrangement and by the three nitrogen atoms of the (NPPh3–) ligand and of the two phosphane imine molecules HNPPh3. The ZrN bond distance of the (NPPh3–) group (193.5 pm) corresponds with a double bond. [ZrCl2(NPPh3)2(HNPPh3)2] ( 2 ): Space group P 1, Z = 4, lattice dimensions at 193 K: a = 1447.6(2); b = 1925.7(2), c = 2457.0(2) pm; α = 67.317(12)°, β = 87.376(12)°, γ = 87.103(13)°; R = 0.0408. The zirconium atom in 2 is octahedrally coordinated by the two chlorine atoms in trans position, and by the nitrogen atoms of the two (NPPh3–) groups as well as by the two HNPPh3 molecules. The ZrN distance of the (NPPh3–) ligands (198.9 and 202.0 pm) suggest some π‐interaction between the zirconium and the nitrogen atoms. 相似文献
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Gertraud Malsiner-Walli Sylvia Frühwirth-Schnatter Bettina Grün 《Journal of computational and graphical statistics》2017,26(2):285-295
The use of a finite mixture of normal distributions in model-based clustering allows us to capture non-Gaussian data clusters. However, identifying the clusters from the normal components is challenging and in general either achieved by imposing constraints on the model or by using post-processing procedures. Within the Bayesian framework, we propose a different approach based on sparse finite mixtures to achieve identifiability. We specify a hierarchical prior, where the hyperparameters are carefully selected such that they are reflective of the cluster structure aimed at. In addition, this prior allows us to estimate the model using standard MCMC sampling methods. In combination with a post-processing approach which resolves the label switching issue and results in an identified model, our approach allows us to simultaneously (1) determine the number of clusters, (2) flexibly approximate the cluster distributions in a semiparametric way using finite mixtures of normals and (3) identify cluster-specific parameters and classify observations. The proposed approach is illustrated in two simulation studies and on benchmark datasets. Supplementary materials for this article are available online. 相似文献
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Reference spectra of important adsorbed organic and inorganic phosphate binding forms for soil P speciation using synchrotron‐based K‐edge XANES spectroscopy 下载免费PDF全文
Jörg Prietzel Gertraud Harrington Werner Häusler Katja Heister Florian Werner Wantana Klysubun 《Journal of synchrotron radiation》2016,23(2):532-544
Direct speciation of soil phosphorus (P) by linear combination fitting (LCF) of P K‐edge XANES spectra requires a standard set of spectra representing all major P species supposed to be present in the investigated soil. Here, available spectra of free‐ and cation‐bound inositol hexakisphosphate (IHP), representing organic P, and of Fe, Al and Ca phosphate minerals are supplemented with spectra of adsorbed P binding forms. First, various soil constituents assumed to be potentially relevant for P sorption were compared with respect to their retention efficiency for orthophosphate and IHP at P levels typical for soils. Then, P K‐edge XANES spectra for orthophosphate and IHP retained by the most relevant constituents were acquired. The spectra were compared with each other as well as with spectra of Ca, Al or Fe orthophosphate and IHP precipitates. Orthophosphate and IHP were retained particularly efficiently by ferrihydrite, boehmite, Al‐saturated montmorillonite and Al‐saturated soil organic matter (SOM), but far less efficiently by hematite, Ca‐saturated montmorillonite and Ca‐saturated SOM. P retention by dolomite was negligible. Calcite retained a large portion of the applied IHP, but no orthophosphate. The respective P K‐edge XANES spectra of orthophosphate and IHP adsorbed to ferrihydrite, boehmite, Al‐saturated montmorillonite and Al‐saturated SOM differ from each other. They also are different from the spectra of amorphous FePO4, amorphous or crystalline AlPO4, Ca phosphates and free IHP. Inclusion of reference spectra of orthophosphate as well as IHP adsorbed to P‐retaining soil minerals in addition to spectra of free or cation‐bound IHP, AlPO4, FePO4 and Ca phosphate minerals in linear combination fitting exercises results in improved fit quality and a more realistic soil P speciation. A standard set of P K‐edge XANES spectra of the most relevant adsorbed P binding forms in soils is presented. 相似文献
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Werner Uhl Lars Cuypers Gertraud Geiseler Klaus Harms Werner Massa 《无机化学与普通化学杂志》2002,628(5):1001-1006
Syntheses and Crystal Structures of Dialkylgallium Hydrides — Dimeric versus Trimeric Formula Units Dialkylgallium hydrides (R = Me, Et, iPr, iBu, neopentyl) were obtained on two different synthetic routes. The dimethyl and diethyl compounds were formed by the reaction of LiH with the corresponding dialkylgallium chlorides via lithium dialkyldihydridogallate intermediates, which so far have not been isolated in a pure form. On the second route, trialkylgallium compounds were treated with [GaH3·NMe2Et] to yield the dialkylgallium hydrides by a substituent exchange reaction. The dimethyl, diethyl and diisopropyl compounds are trimeric in solution. That trimeric structure was verified for the diisopropyl derivative by a crystal structure determination. Di(neopentyl)gallium hydride has a dimeric structure in solution and in the solid state. 相似文献
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Sabine Schlecht Dirk V. Deubel Gernot Frenking Gertraud Geiseler Klaus Harms Jrg Magull Kurt Dehnicke 《无机化学与普通化学杂志》1999,625(6):887-891
Phosphoraneiminato Complexes of Rhenium(VII). Syntheses and Crystal Structures of [ReO3(NPR3)] (R = Ph, Et) and of [ReO(OSiMe3)3(Me3SiNPEt3)] The phosphoraneiminato complexes [ReO3(NPR3)] with R = Ph ( 1 ) and R = Et ( 2 ) are made from dirhenium heptaoxide and the silylated phosphoraneimines Me3SiNPR3. The complexes 1 and 2 as well as the red silanolate [ReO(OSiMe3)3(Me3SiNPEt3)] ( 3 ), which is formed as a by‐product in the synthesis of 2 , are characterized crystallographically. 1 and 2 are monomeric molecules, in which the phosphoraneiminato ligands NPR3– realize short ReN bonds of 179.3 pm ( 1 ) and 178.6 pm ( 2 ), respectively, with large ReNP bond angles of 162.0° ( 1 ) and 160.6° ( 2 ), respectively. In the rhenium(V) complex 3 the oxoligand occupies the apical position of the tetragonal pyramidal coordination of the rhenium atom, while the oxygen atoms of the Me3SiO– groups take the basic positions along with the nitrogen atom of the phosphaneimine molecule. 相似文献