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81.
Muhammad Nawaz Tahir Lela Gorgishvili Jixue Li Tatiana Gorelik Ute Kolb Lutz Nasdala Wolfgang Tremel 《Solid State Sciences》2007,9(12):1105-1109
Crystalline ZrO2 nanoparticles were prepared from zirconium isopropoxide by slow hydrolysis and subsequent hydrothermal treatment of solutions containing various amounts of sodium hydroxide at 180 °C. Whereas moderately basic solutions lead to the formation of nanoparticles of monoclinic ZrO2 with plate-like morphology, and nanoparticles of the cubic ZrO2 high-temperature polymorph with diameters of approx. 5 nm were obtained from strongly basic solutions. The morphology, structure and properties of as-synthesized nanoparticles were characterized using HRTEM, XRD, Raman spectroscopy, UV–vis, PL spectroscopy and BET measurements. The formation of both, the monoclinic and the cubic polymorph, was confirmed by electron microscopy and Raman spectroscopy. The crystallinity and morphology of the resulting ZrO2 nanoparticles can be adjusted by the choice of the reaction conditions. The cubic ZrO2 nanoparticles have a high surface area (300 m2/g) and exhibit a strong photoluminescence in the UV region. 相似文献
82.
Robert E. Pratt William J. Welstead Robert E. Lutz 《Journal of heterocyclic chemistry》1970,7(5):1051-1055
Hydrazoic-sulfuric acid mixture converted cis-α-phenyl-β-benzoylchalcone (trans-dibenzoylstilbene, 4 ) into 2,3-diphenyl-4-benzoylquinoline ( 5 ) the structure of which was proved by debenzoylation to 2,3-diphenylquinoline. α,β-Diphenyl and cis-α,β-dibromochalcones similarly were converted respectively into 2,3,4-triphenylquinoline ( 19 ) and 2-phenyl-3,4-dibromoquinoline ( 20 ). The structure of 19 was shown by difference from the corresponding isoquinoline 21 (synthesized). Smith's mechanism for the analogous conversion of o-phenylbenzophenone into 9-phenylphenanthridine through the 9-fluorenol and the 9-hydroazide with loss of nitrogen and ring expansion, was supported by methyl label experiments using 2-(p-tolyl)benzophenone which gave a 53:47 mixture of 3- and 8-methyl-6-phenylphenanthridines. Applicability of the mechanism to the reactions with disubstituted cis-chalcones was shown by sulfuric acid conversions of two of these into indenol 22 and 2-bromo-3-phenylindenone ( 24 ), respectively. trans-Dibenzoylstilbene underwent resinification in sulfuric acid, giving the quinoline ( 5 ) only when hydrazoic acid was present. 相似文献
83.
Zusammenfassung Von den in der vorigen Mitteilung beschriebenen 3,4-Bis-(p-methoxyphenylhexandionen-(2,5) [meso undracem.] wurde diemeso-Verbindung durch Reduktion in zwei (der drei möglichen) entsprechende sekundäre Diole übergeführt und das höherschmelzende Diol durch Entmethylierung in ein 3,4-Bis-(p-hydroxyphenyl)-hexandiol-(2,5) (Dihydroxyhexoestrol) umgewandelt. Versuche, durch Reduktion eine Überführung in ein Hexoestrol zu erreichen und die sterische Anordnung festzulegen, schlugen sämtlich fehl.Eingehender wurde die Gewinnung homologer tertiärer Diole durch Umsetzung der beiden Hexandionderivate (meso undracem.) mit CH3MgX bearbeitet, wobei unter Ätherspaltung die beiden Bis-homologen-dihydroxy-hexoestrole resultierten. Ammesoiden Hexandionderivat wurde auch die Grignardreaktion allein (ohne Entmethylierung) durchgeführt.
6. Mitt.:H. Bretschneider undR. Lutz, Mh. Chem.95, 1702 (1964). 相似文献
Of the two (meso andracemic) 3,4-di(p-methoxyphenyl)-hexanediones-(2,5) described in the previous communication, themeso compound has been converted by reduction into two (of the three possible) corresponding secondary diols. Demethylation of the higher melting isomer yielded 3,4-di(p-hydroxyphenyl)-hexanediol-(2,5) (dihydroxyhexestrol). Attempts to obtain the corresponding hexestrol by reduction and hence to determine its configuration remained unsuccessful.The preparation of homologous tertiary diols by reaction of the two hexanedione derivatives (meso andracemic) with CH3MgX has been investigated more closely; on ether cleavage the two di-homologous dihydroxyhexestrols were formed. The Grignard reaction was also carried out on themeso hexanedione without subsequent demethylation.
6. Mitt.:H. Bretschneider undR. Lutz, Mh. Chem.95, 1702 (1964). 相似文献
84.
Using an adiabatic calorimeter, the heat of transition Sα ? Sβ, the heat of fusion of Sβ and the specific heat of the liquid had been determined on sulfur samples refined by zone melting and samples doped with chlorine, bromine and iodine. The data obtained from pure sulfur (heat of fusion: 1608 ± 8 J/Tom, specific heat of the liquid at 120°C: 29,4 J/Tom.°C) are about 10% lower than comparable values of other authors. Apparently they represent heat of fusion and specific heat of the pure cyclooctasulfur. The measurements on doped samples (δHS = 1736 ± 10 J/Tom) are in agreement with the data reported in literature and include a portion of enthalpy from the transition reaction of cycloocta-sulfur (Sλ) to catenaocta-sulfur (Sπ), requiring extremly long equilibrium times in pure sulfur. The influence of impurity on the caloric properties of the liquid sulfur is also indicated by the increasing width and decreasing highness of the Cp-maximum at 159°C with increasing amount of halogens. For the heat of transition Sα → Sβ, independent of the amount of impurity, the literature data could be confirmed. At the samples doped with iodine there was observed a previously unreported transition near 65,9°C. 相似文献
85.
Lutz Behle Markus Neuburger Margaretha Zehnder Thomas A. Kaden 《Helvetica chimica acta》1995,78(3):693-702
The new bis-macrocycle 1, 1′-[(1H-pyrazol-3], 5-diyl)bis(methylene)bis[1, 4, 7-triazacyclononane] ( 1 ) was synthesized and its complexation with Cu2+ studied. Potentiometric and spectrophotometric titrations indicate that, in addition to the mononuclear species [Cu(LH2)]4+, [Cu(LH)]3+, [CuL]2+, and [Cu(LH?1)]+, binuclear complexes such as [Cu2L]4+, [Cu2(LH?1)]3+, and [Cu2(LH-2)]2+ are also formed in solution. The stability constants and spectral properties of these are reported. The binuclear species [Cu2(LH?1)]3+ specifically reacts with an azide ion to give a ternary complex [Cu2(LH?1)(N3)]2+, the stability and structure of which were determined spectrophotometrically and by X-ray diffraction, respectively. The two Cu2+ ions are in a square-pyramidal coordination geometry. The axial ligand is one of the N-atoms of the 1, 4, 7-triazacyclononane ring, whereas at the base of the square pyramid, one finds the other two N-atoms of the macrocycle, one N-atom of the pyrazolide and one of the azide, both of which are bridging the two metal centres. In [Cu2(LH?1)(N3)]2+, a strong antiferromagnetic coupling is present, thus resulting in a species with a low magnetic moment of 1.36 B.M. at room temperature. 相似文献
86.
Foltz C Stecker B Marconi G Bellemin-Laponnaz S Wadepohl H Gade LH 《Chemical communications (Cambridge, England)》2005,(40):5115-5117
Chiral C3-symmetric trisoxazolines are highly efficient stereodirecting ligands in enantioselective Cu(II) Lewis acid catalysis which is based on the concept of a stereoelectronic hemilability of the divalent copper; in direct comparison with the analogous bisoxazoline systems they are more efficient in the enantioselective alpha-amination as well as the enantioselective Mannich reaction of prochiral beta-ketoesters. 相似文献
87.
The metal ion distribution on the two metal sites of monoclinic Mn1?xCux(HCOO)2 · 2(H,D)2O mixed crystals are studied by infrared and Raman spectroscopic methods. The spectral regions 3 200–3 400 cm?1 (vOH), 2 875–2 990 cm?1 (vCH), 2 330–2 500 cm?1 (vOD of matrix isolated HDO molecules), 1 350–1 400 cm?1 (symmetric CO2 stretching modes), 570–950 cm?1 (H2O librations), and 490 cm?1 (M? O lattice modes) are mostly sensitive to the metal ions present. The frequency shifts of these bands with increasing content of copper show that Cu2+ prefers the M(1) site, coordinated by HCOO? only. The strengths of the hydrogen bonds increase on going from manganese to copper formate, due to the increased synergetic effect of Cu2+. Solubility and X-ray data of the mixed crystals are included. Irrespective of the same crystal structure, two series of mixed crystals are formed: eutonic area at 0.65 ≥ x ≥ 0.5. 相似文献
88.
The synthesis of a number of nickel(II) complexes containing the didentate phosphane ligand 1,2-bis(di(o-methoxyphenyl)phosphino)ethane (o-MeO-dppe) is reported. Two types of complexes have been synthesized, i.e., the mono(chelate) complex (1) of the general formula [Ni(o-MeO-dppe)X2] (where X = Cl, Br or I) and the bis(chelate) complex (2) of the general formula [Ni(o-MeO-dppe)2]Y2 (where Y = PF6 or trifluoroacetate (TFA)). These complexes have been characterized using electronic absorption and NMR spectroscopy. The structures of the mono(chelate) complex [Ni(o-MeO-dppe)I2] (1c) and of the bis(chelate) complex [Ni(o-MeO-dppe)2](PF6)2 (2e) have been determined by X-ray crystallography. [Ni(o-MeO-dppe)I2] crystallizes in the monoclinic space group P2(1)/c with Z = 4, a = 12.1309(1) A, b = 16.5759(3) A, c = 17.6474(2) A, beta = 119.3250(10) degrees. [Ni(o-MeO-dppe)2](PF6)2 crystallizes in the monoclinic space group C2/c with Z = 4, a = 22.5326(3) A, b = 13.6794(2) A, c = 21.7134(3) A, beta = 107.1745(7) degrees. In both structures the nickel ion is in a square-planar geometry with a NiP2I2 and NiP4 chromophore, respectively. Using 1H and 31P[1H] NMR spectroscopy the behavior of the complexes in various solvents has been studied. It appears that in solution these nickel complexes are involved in an autoionization equilibrium: 2[Ni(o-MeO-dppe)X2] <==>[Ni(o-MeO-dppe)2](2+) + ["NiX(4)"](2-). The ionized complex (3) consists of a cationic unit in which a nickel atom is surrounded by two didentate phosphane ligands, and an anionic unit that stoichiometrically consists of a nickel atom and four anions. The position of the autoionization equilibrium is highly dependent on the anion and the solvent used. In a polar solvent in combination with weakly coordinating anions only the ionized complex is observed, whereas in an apolar solvent in combination with coordinating anions only the mono(chelate) complex occurs. A comparison of the behavior of o-MeO-dppe with its unsubstituted analogue dppe in combination with nickel(II) acetate using 31P[1H] NMR spectroscopy shows that the latter is more readily oxidized. 相似文献
89.
Most p-block metal amides irreversibly react with metal alkoxides when subjected to alcohols, making reversible transformations with OH-substrates a challenging task. Herein, we describe how the combination of a Lewis acidic square-planar-coordinated aluminum(iii) center with metal–ligand cooperativity leverages unconventional reactivity toward protic substrates. Calix[4]pyrrolato aluminate performs OH-bond activation of primary, secondary, and tertiary aliphatic and aromatic alcohols, which can be fully reversed under reduced pressure. The products exhibit a new form of metal–ligand cooperative amphoterism and undergo counterintuitive substitution reactions of a polar covalent Al–O bond by a dative Al–N bond. A comprehensive mechanistic picture of all processes is buttressed by isolation of intermediates, spectroscopy, and computation. This study delineates how structural constraints can invert thermodynamics for seemingly simple addition reactions and invert common trends in bond energies.The combination of structural constraint and metal–ligand cooperativity in calix[4]pyrrolato aluminate inverts common trends of bond energies and enables reversible OH-bond activation. 相似文献
90.
Vlaar MJ Lor MH Ehlers AW Schakel M Lutz M Spek AL Lammertsma K 《The Journal of organic chemistry》2002,67(8):2485-2493
Six novel dispirophosphirane complexes have been synthesized from the reaction of bicycloalkylidenes with the electrophilic phosphinidene complex PhPW(CO)(5). They contain a central phosphirane ring, which is spirofused on one side to a cyclopropane or cyclobutane ring and on the other side with a three-, four-, five-, or six-membered ring. Their crystal structures and MP2/6-31G-computed geometries for simplified parent systems suggest that spirofusion with small rings results in a tightening of the central three-membered phosphaheterocycle, while spirofusion with larger rings results in a relaxation of the phosphirane geometry. Similar theoretical predictions are made for the corresponding annulated hydrocarbons. Strain energies for both the hydrocarbon and phosphorus series of structures have been calculated at G3(MP2). Whereas the [3]triangulane hydrocarbon and phospha[3]triangulane have a significant excess strain of 8.1 and 5.2 kcal/mol per spiroatom, respectively, the excess strain for systems spirofused with larger rings are negligible for the hydrocarbons and even negative for the phosphorus-containing species because of hyperconjugative stabilization. 相似文献