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  • General Chemistry  (1,597)
  • ASTROPHYSICS  (1,139)
  • Inorganic Chemistry  (688)
  • 1990-1994  (3,424)
  • 1950-1954
  • 1994  (3,424)
Collection
Publisher
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  • 1990-1994  (3,424)
  • 1950-1954
Year
  • 11
    ISSN: 0009-2940
    Keywords: Fullerenes ; Azirines ; Photochemistry ; [3 + 2] Cycloadditions ; Electron transfer reactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photoreactions with C60-Fullerene. [3 + 2] Photocycloaddition of 2,3-Diphenyl-2H-azirineUpon irradiation 2,3-Diphenyl-2H-azirine (2) is added to C60 1 with formation of mono and oligo adducts. 1,9-(3,4-Dihydro-2,5-diphenyl-2H-pyrrolo)fulleren-60 (3) has been isolated and identified by standard spectroscopic methods. Mechanistic studies revealed two reaction paths leading to 3, i.e. the classic 1,3-dipolar cycloaddition via the nitrile ylide 4 (direct irradiation) or a route via 2-azaallenyl radical cations 5 (sensitization by photoinduced electron transfer).
    Additional Material: 1 Tab.
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  • 12
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 805-811 
    ISSN: 0009-2940
    Keywords: Bent metallocene complexes ; Heterodimetallic zirconium-aluminium compounds ; Hydrocarbyl-bridging ligands ; “π-Agostic” interaction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The (s-trans/s-cis-η4-butadiene)zirconocene reagent adds dimethylaluminium chloride to yield the heterodimetallacyclic main group/transition-metal system 2b, containing a seven-membered metallacyclic framework that exhibits a “π-agostic” s̰-allyl zirconium interaction. Similar compounds (2c-f, 5a, 6) are obtained upon reaction of (butadiene)zirconocene with Et2All and (butadiene)hafnocene with Me2AlCl or Et2AlI. Addition of Me2AlCl or Et2AlI to (isoprene)zirconocene proceeds regioselectively to yield the corresponding heterodimetallacycles bearing the methyl substituent at C-3 (i.e. near to the attached aluminium center). The iodide-bridged heterodimetallacycles exhibit dynamic NMR spectra that indicate a rapid enantiomerization process on the NMR time scale (ΔG±ent ≈ 11-12 kcal mol-1). It is assumed that this automerization reaction proceeds by rate-limiting aluminium-halogen bond cleavage leading to an acyclic mixed metal heterodimetallic intermediate. This process is markedly inhibited by the presence of excess diethylaluminium iodide.
    Additional Material: 1 Ill.
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  • 13
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 829-833 
    ISSN: 0009-2940
    Keywords: N-Isocyandialkylamine complexes ; Cyanamide complexes ; Guanidine complexes ; Reactions at the coordinated ligand ; N—N bond breakage ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Metal Complexes of Functional Isocyanides, XXIV.  -  Reactions of N-Isocyanodialkylamine Complexes with Secondary AminesReactions of pentacarbonyl(N-isocyanodialkylamine) group 6-metal complexes [M(CO)5CNNR2] [M = Cr, W; R = Et, iPr; 2R = -{MeCH(CH2)3CHMe}-] with secondary amines proceed with cleavage of the N—N bond and C→N migration of the metal to give the corresponding N-cyanamide complexes [M(CO)5NCNR′2] (1a-2g) [R′ = Me, Et, nPr, nBu; 2R′ = —(CH2)4—, —(CH2)5—, —(CH2)2O(CH2)2—]. However, when diiodobis(N-isocyanodialkylamine)platinum(II) was allowed to react with an excess of the amine amine(guanidine)platinum(II) complexes [PtI2(HNR′2){HN=C(NR′2)2}] (3a-c) [R′ = Et; 2R′ = —(CH2)5—, —(CH2)2O(CH2)2—] were obtained. Structural assignments are made on the basis of IR, NMR (1H, 13C), and mass spectroscopy as well as of an X-ray structure analysis of trans-[PtI2(HNEt2){HN=C(NEt2)2}] (3a).
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  • 14
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 849-851 
    ISSN: 0009-2940
    Keywords: Selenium iodides ; Imidazoles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Imidazole Derivatives, IX.  -  Stabilisation of Selenium Diiodide by ComplexationHerrn Professor Helmut Werner zum 60. Geburtstag gewidmet.Stable selenium diiodide complexes 2 are obtained by the reaction of the 2-selenoxoimidazolines 1 with iodine. An X-ray structure analysis of 2c reveals its monomeric nature. In the trigonal bipyramid, the iodo substituents are situated in axial positions forming elongated iodine bonds [Se-I(1) 2.854(1), Se—I(2) 2.768(1) Å; I(1)—Se—I(2) 175.4(0)°].
    Additional Material: 1 Ill.
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  • 15
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 881-885 
    ISSN: 0009-2940
    Keywords: Fiscellanes, doubly-bridged ; Semibullvalenes, doubly-bridged ; Cyclopropanes ; SEM-protective groups ; Annulenes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Reactions of the First Doubly-Bridged FiscellanesThe synthesis of the novel hexacycle 2 containing a fiscellane framework is described. Starting from Weiss' tetraester 6, the fiscellane 2 is build up in six steps by successive chemical transformation of the methoxycarbonyl functions using SEM protecting groups. The behaviour of the novel diol 2 towards introduction of several leaving groups is examined. Upon treatment with methanesulfonyl chloride the highly strained hexacycle 2 undergoes a skeletal rearrangement with formation of the triene 4. Instead of reacting to a doubly-bridged semibullvalene 3, the diol 2 gives rise to a new heterocyclic π perimeter 5 when the trifluoroacetyl derivative 12 is treated with sodium iodide in acetone.
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  • 16
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 905-909 
    ISSN: 0009-2940
    Keywords: Allyltributylstannane ; Trimethylsilyl cyanide ; α,β-Epoxy aldehydes ; Chelation-controlled addition ; Diastereoselectivity ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chelate-Controlled Diastereoselective Addition to α,β-Epoxy AldehydesLiClO4-mediated reaction of trans-substituted α,β-epoxy aldehydes 1 with allyltributyltin (2) or trimethylsilyl cyanide provides a general method for the synthesis of the corresponding syn-alcohols 3 with high selectivity. In the case of cis-substituted α,β-epoxy aldehydes the selectivity depends on the size of the substituents.
    Additional Material: 2 Tab.
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  • 17
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 947-953 
    ISSN: 0009-2940
    Keywords: 1-Aza-2-azoniaallene cations ; Isocyanates ; 4,5-Dihydro-5-oxo-1,2,4-triazolium salts ; Cinnolinium salts ; Cycloadditions ; Calculations, AM1 ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1-Aza-2-azoniaallene salts 3, prepared in situ from geminal chloroalkylazo compounds 2 with Lewis acids, react with isocyanates 4 to give 4,5-dihydro-5-oxo-3H-1,2,4-triazolium salts 6 and 4,5-dihydro-5-oxo-1H-1,2,4-triazolium salts 7, respectively. The intramolecular cyclization of 3u opens a new route to cinnolinium salts 11. Allenes 3 react with isobutene to give pyrazolium salts 8. According to AM1 calculations the cycloadditions of 3 to isocyanates proceed in two steps via acylium salts 5 as intermediates. Mechanistically, the rearrangements 6 → 7 resemble Wagner-Meerwein rearrangements rather than pericyclic [1,5]-sigmatropic shifts.
    Additional Material: 1 Ill.
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  • 18
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 965-966 
    ISSN: 0009-2940
    Keywords: Cyclophanes ; Photochemistry ; Triplet states ; Enolization ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: When ethanolic solutions of 4-(1-naphthoyl)[2.2]paracyclophane (3) and 4-(2-naphthoyl)[2.2]paracyclophane (4) are subjected to UV irradiation at low temperature, 1,5-hydrogen migration of the 2-H bridge proton to the carbonyl group takes place, leading to the enol of type 2. In the context of mechanistic considerations the triplet spectroscopic properties of 3 and 4 are discussed.
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  • 19
    ISSN: 0009-2940
    Keywords: Cyclophosphahydrazides ; Dinitrogen-bridged ; Conformation ; Chair and Boat forms ; Dinuclear Mo(0) complexes ; 1,2,4,5,3,6-Tetrazadiphosphorinanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions of methylhydrazine with RPC12 (R = Et, tBu, and Ph) produced the cyclic phosphorus (III) hydrazides (1,2,4,5,3,6-tetrazadiphosphorinanes) [RPN(Me)N(H)2 (R = Et, 1; (Ph, 2; tBu, 3) in good yields. The 1H-and 31P-NMR spectroscopic analysis indicated that 1 exists in chair and boat conformations. However, it crystallizes in the chair conformation exclusively. The X-ray crystallographic investigation of all the three cyclo-phosphorus hydrazides 1-3 confirms the existence of these compounds in the chair conformations in the solid state. The reaction of Mo(CO)4-(NHC5H10)2 with 1 and 2 gives the dinuclear Mo(0) complexes [{Mo(CO)4(NHC5H10)}2(μ-[RPN(Me)N(H)]2}] (R = Et, 5; Ph, 6). Based on 1H- and 31P-NMR spectroscopic data, a bridging dinuclear dimetallic formulation is proposed for 5 and 6. The IR spectra indicate that the carbonyls are disposed in cis-geometry around the Mo(0) center.
    Additional Material: 6 Ill.
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  • 20
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 2373-2379 
    ISSN: 0009-2940
    Keywords: Chelating ligands ; Molybdenum complexes ; Peroxo complexes ; Catalysis ; Olefine epoxidation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Substituted N,N-Chelate Ligands - Applications in Molybdenum-Catalyzed Epoxidation of Olefins*Oxodiperoxomolybdenum complexes 4 of substituted 2-[3(5)-pyrazolyl]pyridines (2a-g) were synthesized in order to control the solubility of these complexes in organic solvents. Alkyl side chains (butyl, octyl, octadecyl) increase the solubility of the complexes and enable spectroscopic investigations in solution. Due to the symmetry of the ligands the peroxo complexes 4 appear in two isomeric forms, with the terminal oxo ligand in the trans position either to pyridine or to pyrazole. The latter isomer of (C5H4NC3H2N2CH2COOEt)MoO(O2)2 (4f) was characterized by an X-ray structure analysis. The alkyl-substituted peroxo complexes are active catalysts for the epoxidation of olefins with tert-butyl hydroperoxide.
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