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  • 11
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 57 (2001), S. 347-348 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Single crystals of the title compound have been grown by annealing microcrystalline zinc cyanamide at 843 K in silver crucibles. Zn(CN2) crystallizes as colourless prisms. The crystal structure is composed of corner-linked ZnN4/2 tetrahedra. Carbon and nitrogen form (CN2)2− dumb-bells with the C atom on a twofold axis. Nitrogen is approximately trigonally planar, coordinated by two Zn atoms and one C atom.
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  • 12
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Crystal structure determination reveals that the unknown cycloaddition product between maleic anhydride, cyclopentadiene, and 1,2-bis(dibromomethyl)benzene has a nona-cyclic centrosymmetric structure. The compound was studied as DMF solvate (1∶2). There is no significant intermolecular interaction between the title molecule and the DMF. Packing is in layers for both molecular species. A possible mechanism of formation of the title compound is discussed.
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 116 (1985), S. 203-210 
    ISSN: 1434-4475
    Keywords: Potassium-cyclo-tetraphosphate(V)-dihydrate ; Crystal structure ; Dehydration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The crystal structure of (KPO3)4 · 2H2O was solved by direct methods andFourier-syntheses (triclinic; P $$\bar 1$$ ;a=1 114.9 (2),b=821.9 (2),c=815.7 (3) pm; α=88,88 (2), β=84.51 (2), γ=82.70 (2)°;Z=2; 5910 unique reflections;R=0.052). The cyclic anions exhibit point symmetry S4 with four terminal oxygens in axial and four in equatorial position. Thermal investigations (DTA, TGA, X-Ray-methods) show that the dehydration occurs in two steps. The anhydrous form of (KPO3)4 is stable above 230 °C and undergoes a second order phase transition which is complete at 515±5 °C.
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 111 (1980), S. 377-384 
    ISSN: 1434-4475
    Keywords: Crystal structure of Cr2H2(As2O7)(As4O12) ; Cyclo-tetraarsenate(V)-ion ; Diarsenate(V)-ion ; Magnetic susceptibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The crystal structure of Cr2H2(As2O7)(As4O12) has been determined by X-ray methods using single crystal diffractometer data (1,152 reflections,R=0.054, orthorhombic,Pmmn,a=1317.7 (7),b=1124.9 (6),c=494.3 (4) pm,Z=2). The crystal structure contains both diarsenate(V) and the hitherto unknown cyclo-tetraarsenate(V)-anions. The magnetic susceptibility follows theCurie-Weiss law (μ=3.86±0.01 μB/Cr3+, Θ=−31 K).
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 114 (1983), S. 699-709 
    ISSN: 1434-4475
    Keywords: Anhydrous sodium-cyclo-tetraphosphate(V) ; Crystal-structure ; Sodium-cyclo-tetraphosphate(V)-monohydrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A reinvestigation of the system (NaPo3)4/H2O has been carried out. Besides the already known tetra-hydrate and anhydrous form, a mono-hydrate in the temperature range 100–120°C exists. Single crystals were obtained by crystallization from aqueous solutions containing higher alcohols (e.g. ethyleneglycol) at ∼115°C. The crystal structure was solved by X-ray methods (orthorhombic;P212121;a=1365.4(2),b=1 347.5(3),c=629.1(3)pm;Z=4; 2774 diffractometer data;R=0.053). The cyclic anions exhibit point symmetryD 2d with all terminal oxygens in eclipsed conformation. With respect to the (NaPO3)4-part of structure, mono-hydrate and anhydrous forms are isostructural; lattice parameters of the latter area=1 380.8(2),b=1 363.3(2),c=602.7(2) pm. The transition mono-hydrate to anhydrous form occurs topochemically and is reversible.
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  • 16
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1, 4, 5, 6-Tetrahydro-ν-tetrazin-DerivateThe title compounds 2 and 13 are readily available from α-lithiated N-alkyl-nitrosoamines 1 (see Tables 1 and 2) which decompose at - 73° to yield the N-oxides 2. The ESR. spectra of two derivatives 1 are recorded (Fig. 1), and tentative mechanisms are proposed for the head to head dimerizations (la- 3- 4- 5- 2a and Scheme 1). Coupling of lithionitrosoamines with iodine (-6) and alternative decomposition routes of representatives of this class of organometallics with special substitution [equations (2)-(5)] are reported.The structures of the tetrazines are established by spectroscopic data [ESCA] (Fig. 2), IR., UV., 1H- (cf. Fig. 9) and 13C-NMR., PE. (Scheme 2), by an X-ray analysis of 2a (Fig. 4-8 and Table 3), and by the chemical reactions. The crystal structure of 2a is a twisted boat with non planar terminal nitrogen atoms which reflects the electron repulsion in the 4-atom-6-electron N—N=N≡N-system. Comparisons are made with 2-tetrazenes, the open chain analogues of 13, wherever possible. Raney-Ni reductions of 2 or 13 gives diamines 14 to which is assigned the d, l-configuration through the 1H-NMR. spectra of the aminals 7 and 15. Neither the oxides 2 nor the tetrazines 13 undergo cycloaddition reactions [equation (6) and Section 4].Compound 2a is dimerized to the bis (nitrosoamino)-2-tetrazene 18 by treatment with acid, ZnII, CuI or iodomethane. 2a is oxidized at nitrogen to the ethylene diamine derivative 6a (through 20, with H2O2), or at the CH2-groups of the ring to give oxo-N-oxide 21 (with MnO2 or the ring contracted oxo-tetrazoline-N-oxide 22 (with KMnO4).Pyrolysis or photolysis of the dimethyl tetrahydrotetrazine 13a furnishes the trimer 26 of N-methylimine, but no diazetidine 27. Silver and mercury complexes 29 are obtained from 13a, while Cr(CO)5. THF does not furnish a complex as with azocompounds, but rather replaces N2 in 13a by CO (→ 28). Oxidation with permanganate converts 13a into the oxalic acid derivative 30 with unchanged tetrazine structure.
    Additional Material: 10 Ill.
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  • 17
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Hochalkylierte Cyclohexane. - Röntgenstrukturanalyse, Kraftfeld-Berechnungen und Konformationen von cis/trans-1,4-disubstituierten Cyclohexan-IsomerenDie Struktur von mesyliertem cis- und trans-Tetramethylshisool cis-2 und trans-2 wurde durch Einkristall-Röntgenmethoden aufgeklärt. In cis-2 nimmt die Isopropenylgruppe im Kristall eine axiale Stellung ein, und die erhaltenen Strukturdaten stehen in gutem Einklang mit Kraftfeldberechungen. In trans-2 wurden zwei Rotamere, die durch Rotation der Isopropenylgruppe entstehen, durch NOE-Messungen zugeordnet. Der Vergleich der spektroskopischen Daten mit denen anderer Tetramethyllimonenderivate zeigt, daß diese in Verbindungen mit bevorzugt äquatorialer und bevorzugt axialer Lage der Isopropenylgruppe eingeordnet werden können.
    Notes: The structures of mesylated cis- and trans-tetramethylshisool cis- 2 and trans-2 have been elucidated by single-crystal X-ray techniques. In cis-2 the isopropenyl group adopts an axial position in the crystal, and the structural data obtained are in good agreement with those from force-field calculations. In trans-2 the two rotamers arising from rotation of the isopropenyl group were assigned by NOE measurements. Comparison of the spectroscopic data with those of other tetramethyllimonene derivatives showed that these can be classified into compounds with preferred equatorial and preferred axial position of the isopropenyl group.
    Additional Material: 2 Ill.
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  • 18
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 321-327 
    ISSN: 0009-2940
    Keywords: Trifluororthocarbonates of potassium, rubidium, cesium ; Phase transitions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Crystal Structures of Potassium, Rubidium, and Cesium Trifluororthocarbonate and a Remark Concerning the Barium Sulfate Type1)Crystals of potassium, rubidium, and cesium trifluororthocarbonate (9a, 9b, and 9c) have been grown by Ostwald ripening in CH3CN applying a COF2 pressure of 3 bar. According to X-ray single-crystal structure analysis, 9a, 9b, and 9c belong to the baryte-structure family with an pseudotetrahedral anion being dynamically disordered at room temperature. All of the title compounds undergo a phase transition into a monoclinic, completely ordered low-temperature form, which has been refined for 9c. The C - O bond seems to be shortened by polar interactions. The results obtained with 9a, 9b, and 9c at room temperature indicate that the type of disorder found in 9 might be generally present in baryte-type compounds.
    Additional Material: 2 Ill.
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  • 19
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 2007-2013 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cyclopentenone Derivative, XII1). - Studies on the Stereoselectivity of Intramolecular CycloadditionsChemical as well as stereochemical results of intramolecular cycloadditions in the cyclopentenone series are shown to depend very strongly on the nature of the connecting unit. With linking carbon chains as in 6 and 7, cycloaddition products 8 and 9 are formed with high but differing stereoselectivity, while the sulfur analogue 11 gives rise to a 1:1.4 mixture of steroisomers 12 and 13. Some stereoselective transformations of the cycloadducts are reported.
    Notes: Das chemische wie auch stereochemische Resultat intramolekularer Cycloadditionen in der Cyclopentenon-Reihe zeigt eine starke Abhängigkeit von der Natur des Verknüpfungsgliedes. Bei Überbrückung mit einer Kohlenstoffkette werden aus den Vorstufen 6 und 7 die Cycloadditionsprodukte 8 und 9 mit ausgezeichneter, wenn auch entgegengesetzter Stereoselektivität hervorgebracht. Einbau eines Schwefelatoms in die Kohlenstoffkette indessen führt vom Thioether-Analogon 11 zu einem 1:1.4-Gemisch der stereoisomeren Cycloaddukte 12 und 13. Einige stereoselektive Transformationen der Cycloaddukte werden mitgeteilt.
    Additional Material: 4 Tab.
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  • 20
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1383-1388 
    ISSN: 0009-2940
    Keywords: Phase-transfer catalysis ; Ozonides, ionic ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthetic Routes to New Ionic OzonidesNew synthetic routes to tetraorganylammonium ozonides involving exchange reactions with alkali metal ozonides were investigated. The previously reported reaction between tetraalkylammonium hyperoxides R4N+O2- (R = Me, Et) and alkali metal ozonides in liquid ammonia is severely hampered by the difficult synthesis of these hyperoxides; they are unknown for other quaternary ammonium cations. A similar reaction between the easily accessible chlorides of trialkylbenzylammonium ions and KO3 yields mixed ozonides/chlorides due to some solubility of KCl in liquid ammonia. The new compounds BzlMe3N+ (O3-)0.6Cl-0.4 (3), BzlEt3N+ (O3-)0.8Cl0.2- (4) and Bzl(nBu)3N+(O3-)0.5Cl0.5- (5) were prepared by this route. - The by far superior route to new ozonides utilizes macroreticular cation exchange resins in liquid ammonia. Batch equilibration between an excess of the appropriate ionic form of the resin and CsO3 produced Me3PhN+O3- (6), BzlMe3N+O3- (7), Bzl(nBu)3N+O3- (8), and (nPr)4N+ O3- (9) in almost quantitative yield. Compounds 4, 6, and 7 were studied by single-crystal X-ray analysis; the shortening of the ozonide bond length and the widening of the bond angle in comparison to the alkali metal ozonides as well as the possibility of C-H…O hydrogen bonding are discussed. Thermal stabilities were determined by DTA/TG methods, rapid decomposition starts at 59-79°C for 3, 6, and 7 and at 28-56°C for the remaining new ozonides which contain detachable β-H atoms.
    Additional Material: 3 Ill.
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