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1.
Chiral salicylidenphenethylamines (R)‐HA or (S)‐HA , 2‐salicylidenfurfuryl‐imines HB , and 2‐salicylidenaminoethanol HC react with sodium hydride or sodium hexamethyldisilylamide to form the sodium complexes [Na(R)‐A] 4 · 0,5 Et 2 , [Na(S)‐A] 4 · 0,5 Et 2 O (1) , [NaB] 4 · 0,5 Ph‐Me (2) and [(dme)NaC] 4 (3) . In the presence of 18‐crown‐6 the complex [Na(18‐crown‐6)(thf) 2 ] 2 [Na 2 (C)] 4 · THF (4) can also be isolated. The crystal structure analyses of both 1 and 2 show that heterocubane structures with a Na4O4 frame work are formed. Additionally, the imine nitrogen atom is bonded at the Na atom which has the coordination number 4 in 1 . Additional coordination of the furfuryl oxygen atom results in the coordination number five for the sodium atom in 2 . In 3 which is also a tetramer, two Na2O2 units are connected via two imino‐ethanol bridges Na(1)‐N(=CH‐phenolat)‐CH2CH2‐OH‐Na(2A). The crystal structure analysis displays that 4 is an ionic compound consisting of two [(thf)2Na(18‐crown‐6)]+ cations and the dinuclear dianion [Na 2 (C) 4 ] 2? . Both 1 and 2 are carboxylation reagents which transfer CO2 to 2‐fluoropropiophenone. 1 is more active than 2 , but 3 and 4 are inactive. 相似文献
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Jens Langer Sven Krieck Reinald Fischer Helmar Görls Matthias Westerhausen Prof. Dr. 《无机化学与普通化学杂志》2010,636(7):1190-1198
Iodide is a very soft and large anion and as such its extreme ability to be polarized leads to a flat energy surface with respect to the variation of the Ca–I distances in [(L)nCaI2] and [(L)nCa(R)I]. The influence of the donor strength and the bulkiness of the neutral coligands L on the Ca–I distances is studied. The base adducts of calcium diiodide can be isolated after the addition of L to CaI2 or from the Schlenk equilibrium after the direct synthesis of calcium powder with aryl iodides. As L the ethers diethyl ether (Et2O), tetrahydrofuran (thf), tetrahydropyran (thp), 1,2‐dimethoxyethane (dme), 18‐crown‐6 (18C6), bis(methoxyethyl)ether (diglyme), and amines tetramethylethylenediamine (tmeda), and hexamethyltriethylenetetramine (hmteta) are studied yielding the adducts [(thp)4Ca(Ph)I] ( 1a ), [(thf)4Ca(Ph)I] ( 1b ), [(dme)2(thf)Ca(Ph)I] ( 1c ), [(18C6)Ca(Ph)I] ( 1d ), and [(tmeda)2Ca(Ph)I] ( 1e ), as well as [(thp)4CaI2] ( 2a ), [(thf)4CaI2] ( 2b ), [(Et2O)4CaI2] ( 2c ), [(diglyme)(thf)2CaI2] ( 2d ), [(diglyme)(dme)CaI2] ( 2e ), [(dme)2(thf)CaI2] ( 2f ), [(18C6)CaI2] ( 2g ), [(tmeda)2CaI2] ( 2h ), and [(hmteta)CaI2] ( 2i ). For comparison reasons, [(thf)4Ca(Ph)Br] ( 3a ), [(thp)4CaBr2] ( 4a ), [(thf)4CaBr2] ( 4b ), and [(dme)2(AcOH)CaBr2] ( 4c ) with AcOH being acetic acid are included as well. The comparison shows that the coordination number of calcium itself only plays an insignificant role whereas bulkiness and donor strength of L represent the key influences. 相似文献
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Dr. Reinald Fischer Dr. Helmar Görls Philippe R. Meisinger Regina Suxdorf Prof. Dr. Matthias Westerhausen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(55):12830-12841
Systematic variation of the 1,4-dioxane (dx) concentration during the precipitation of sparingly soluble [MgBr2(dx)2] from ethereal Grignard solutions of RMgBr has allowed the structural investigation of crystallized [R2Mg(dx)n] (n=1, 1.5, 2, and 3), which form during this dioxane method, depending on the bulkiness of R. The numbering of the complexes explored in this study is based on the number n of dioxane molecules per magnesium atom, followed by the substituent R; an apostrophe denotes coordination polymers. The following derivatives were studied by X-ray crystal-structure determination and NMR spectroscopy: n=1: [Me2Mg(μ-dx)]∞ ( 1′-Me ) and [nPr2Mg(μ-dx)]∞ ( 1′-nPr ); n=1.5: [{iPr2Mg(dx)}2(μ-dx)] ( 1.5-iPr ), [{oTol2Mg(dx)}2(μ-dx)] ( 1.5-oTol ), and [(Me3Si-C≡C)2Mg(dx)1.5]∞ ( 1.5′-C2SiMe3 ); n=2: [tBu2Mg(dx)2] ( 2-tBu ) and [oTol2Mg(dx)2] ( 2-oTol ); n=3: [Ph2Mg(dx)3] ( 3-Ph ). In the structure types 1′ , 1.5 , and 2 , the magnesium atom exhibits the coordination number 4, whereas pentacoordinate metal atoms are observed in types 3 and 1.5′ . The structure type 2′ is realized for [(Ph-C≡C)2Mg(dx)2]∞ ( 2′-C2Ph ), [MgCl2(dx)2]∞ ( 2′-Cl ), and [MgBr2(dx)2]∞ ( 2′-Br ) with hexacoordinate metal atoms. The solubility of the dioxane adducts in common organic solvents strongly depends on the degree of aggregation with the solubility decreasing from molecular to strand to layer structures. 相似文献
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Kaçeli Xhixha M. Hasani F. Sahiti F. Xhixha G. Krasniqi B. Shyti M. Dhoqina P. Gavazaj F. Bytyçi R. Mehmeti S. 《Journal of Radioanalytical and Nuclear Chemistry》2018,316(1):389-395
Journal of Radioanalytical and Nuclear Chemistry - The environmental radioactivity (40K, 238U, 232Th and 137Cs) in soils around Kosova-A and Kosova-B power plants is determined by high-resolution... 相似文献
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Bruschi L Fois G Mistura G Sklarek K Hillebrand R Steinhart M Gösele U 《Langmuir : the ACS journal of surfaces and colloids》2008,24(19):10936-10941
We performed systematic adsorption studies using self-ordered nanoporous anodic aluminum oxide (AAO) in an extended range of mean pore diameters and with different pore topologies. These matrices were characterized by straight cylindrical pores having a narrow pore size distribution and no interconnections. Pronounced hysteresis loops between adsorption and desorption cycles were observed even in the case of pores closed at one end. These results are in contrast with macroscopic theoretical models and detailed numerical simulations of the adsorption in a single pore. Extensive measurements involving adsorption isotherms, reversal curves, and subloops carried out in closed-bottom pores suggest that the pores do not desorb independently from one another. 相似文献
6.
Westerhausen M Gärtner M Fischer R Langer J 《Angewandte Chemie (International ed. in English)》2007,46(12):1950-1956
Organocalcium chemistry is still in its infancy. The direct synthesis of activated calcium and (substituted) iodobenzenes allows for the large-scale and high-yield synthesis of aryl calcium iodides. The influence of the substitution patterns of the phenyl group, halogen atom, and solvent is discussed. Aryl calcium iodides show a Schlenk equilibrium that enables the isolation of diaryl calcium derivatives. Owing to the high reactivity of aryl calcium halides, low temperatures have to be maintained throughout the preparative procedures in order to avoid side reactions. A decrease of reactivity and, hence, an enhanced stability at higher temperatures can be achieved by shielding of the calcium atom by increasing the coordination number of the metal center or by substitution of the iodide anion by bulky groups. 相似文献
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Westerhausen M Gärtner M Fischer R Langer J Yu L Reiher M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(22):6292-6306
Compounds of the type aryl--M--X, with M=Ca, Sr, Ba and X as any kind of ligand (such as halide, phosphanide, amide, aryl), are presented. The low reactivity of the heavy alkaline earth metals calcium, strontium, and barium enforces an activation prior to use for the direct synthesis. The insertion of these metals into C--I bonds of aryl iodides (direct synthesis) yields aryl metal iodides and has to be performed at low temperatures and in THF. Aryl alkaline-earth-metal compounds show some characteristics: 1) the ease of ether cleavage enforces low reaction temperatures, 2) for Sr and Ba the Schlenk equilibrium is shifted towards homoleptic MI2 and MPh2, 3) high solubility of diaryl alkaline-earth-metal derivatives in THF even at low temperatures initiated quantum chemical investigations on the aggregation behavior, and 4) a strong low field shift of the 13C resonances of the ipso carbon atoms in NMR spectra was observed. First results from quantum chemical calculations on diaryl dicalcium(I) suggest a long Ca--Ca bond with a considerable Ca--Ca bond dissociation energy. Initial results on a selection of applications such as metallation, metathesis, and addition reactions of aryl calcium compounds are presented as well. 相似文献
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Gärtner M Fischer R Langer J Görls H Walther D Westerhausen M 《Inorganic chemistry》2007,46(12):5118-5124
Various preparative procedures are employed in order to synthesize alkaline earth metal bis(diphenylamides) such as (i) metalation of HNPh2 with the alkaline earth metal M, (ii) metalation of HNPh2 with MPh2, (iii) metathesis reaction of MI2 with KNPh2, (iv) metalation of HNPh2 with PhMI in THF, and (v) metathesis reaction of PhMI with KNPh2 followed by a dismutation reaction yielding MPh2 and M(NPh2)2. The magnesium compounds [(diox)MgPh2]infinity (1) and (thf)2Mg(NPh2)2 (2) show tetracoordinate metal atoms, whereas in (dme)2Ca(NPh2)2 (3), (thf)4Sr(NPh2)2 (4), and (thf)4Ba(NPh2)2 (5) the metals are 6-fold coordinated. Additional agostic interactions between an ipso-carbon of one of the phenyl groups of the amide ligand and the alkaline earth metal atom lead to unsymmetric coordination of the NPh2 anions with two strongly different M-N-C angles in 3-5. 相似文献