Showing papers on "Norbornadiene published in 1979"
TL;DR: In this paper, carboxamide and sulfonamide-linked polystyrene-anchored cobalt (II) tetraarylporphyrins containing 0.28 to 0.44% cobalt are described for the conversion of quadricyclane to norbornadiene.
Abstract: Methods are described for the preparation of carboxamide- and sulfonamide-linked polystyrene-anchored cobalt (II) tetraarylporphyrins containing 0.28 to 0.44% cobalt, which are highly active catalysts for the conversion of quadricyclane to norbornadiene. These cobalt catalysts gradually lose some of their activity upon repeated recycling. This loss in catalytic activity apparently arises from partial oxidation, since the loss of catalytic activity can be partially restored by treatment with a strong reducing agent such as titanium(III). The apparent activities of these catalysts are increased if the catalyst is finely powdered, thereby suggesting diffusion limitation of the catalytic activity. Applications are discussed of these catalysts in a proposed solar energy storage system based on the reversible valence isomerization of norbornadiene to quadricyclane. 1 figure, 5 tables.
76 citations
TL;DR: In this paper, the radical cation couple quadricyclane+ (Q+)/norbornadiene+ (NBD+) is considered and the barrier of interconversion is estimated to be significantly lower than that for the corresponding neutrals.
Abstract: The previously discussed principles involved in electrocyclic reactions of openshell ions are exemplified for a type C system, the radical cation couple quadricyclane+ (Q+)/norbornadiene+ (NBD+). Exhaustive calculations (MINDO/3) for the various states of the ions support the general predictions for such types of systems. The barrier of interconversion Q+ NBD+ is estimated to be significantly lower than that for the corresponding neutrals. Experimental support to this prediction is obtained by γ-irradiation of Q or NBD in an electron scavenging matrix. In both cases only NBD+ is observed, indicating that Q+ is not stable at 77 K. Previous observations and propositions referring to the system Q+/NBD+ are discussed in view of the present findings.
52 citations
TL;DR: In this paper, the authors showed that the photoexcited Cu(I)-phosphine compound with a ground-state norbornadiene molecule is better able to accommodate the available data.
Abstract: The valence isomerization of norbornadiene to quadricyclene can be photosensitized with high quantum efficiency by certain copper(I)-phosphine compounds. Sensitization yields in the presence of Cu(PPh/sub 3/)/sub 2/BH/sub 4/ and Cu(PPh/sub 2/Me)/sub 3/BH/sub 4/ attain limiting values of 0.76 and 0.54, respectively, at high norbornadiene concentrations. In contrast, Cu(diphos)BH/sub 4/ (diphos is 1,2-bis(diphenylphosphino)ethane), which contains a bidentate phosphine ligand, is decidely less effective. The mechanism of sensitization by these copper(I)-phosphine compounds is fundamentally different from that exhibited by simple cuprous salts in that no ground-state coordination to the metal center occurs. A pathway involving the bimolecular interaction of the photoexcited Cu(I) compound with a ground-state norbornadiene molecule is better able to accommodate the available data. Electronic absorption and emission studies reveal some interesting differences between the spectral properties of effective vs. noneffective sensitizers.
49 citations
TL;DR: In this paper, the X-ray-crystal structures of both (η5-C5H5)Cr(CO)2(NO) (I) and ( η5C13H9)Cr (CO) 2 (NO)2 (II) are described, where the carbonyl and nitrosyl groups are disordered in I, but the nitro-syl ligand in II occupies a position in the electron-rich C(9) of the fluorenyl system.
40 citations
TL;DR: In this paper, the electronic and steric effects of the ligand were used to determine the activity of catalysts for acetone hydrogenation formed in situ from [Rh(norbornadiene)Cl]2 and phosphines or phosphinic acid esters.
36 citations
TL;DR: In this article, the singlet --> singlet excited state spectra of cyclohexene, 1,4-cyclohexadiene, norbornene, and bicyclo[2.1]-2,5-heptadiene were studied by electron impact at scattering angles from 5° to 80°, and impact energies of 30 and 50 eV.
Abstract: The excited electronic states of cyclohexene, 1,4-cyclohexadiene, norbornene (bicyclo[2.2.1]-2-heptene), and norbornadiene (bicyclo-[2.2.1]-2,5-heptadiene) have been studied by electron impact at scattering angles from 5° to 80°, and impact energies of 30 and 50 eV. Low-lying features with intensity maxima at 4.24 eV in cyclohexene and 4.10 eV in norbornene are identified as singlet --> triplet transitions. Similar features in the spectra of 1,4-cyclohexadiene and norbornadiene extending from 3.4 to 5.4 eV and 2.9 to 4.5 eV, respectively, are believed to result from superposition of two low-lying singlet --> triplet transitions in each molecule. In norbornadiene these features have estimated intensity maxima at 3.4 and 3.9 eV, while in 1,4-cyclohexadiene they appear to be more highly overlapped, yielding a single intensity maximum at 4.29 eV. The singlet --> singlet excited state spectra of these molecules are discussed from the point of view of a model in which ethylene units interact via through-bond and through-space effects. In each of these four molecules, transitions to several superexcited states are observed.
33 citations
TL;DR: In this paper, the synthesis of [Rh(NBD)L2 ]ClO4 complexes (L=nitrogen donor ligand), obtained from [RBD)2] ClO4, and their reactions with triphenylphosphine and carbon monoxide are described.
Abstract: The syntheses of [Rh(NBD)L2 ]ClO4 complexes (L=nitrogen donor ligand), obtained from [Rh(NBD)2]ClO4, and their reactions with triphenylphosphine and carbon monoxide are described.
29 citations
TL;DR: Polycyclic 1,2,3-trithiolans have been made by reacting the olefins exo-and endo-cyclopentadiene dimer, cyclopentadienes trimer, and norbornene with elemental sulphur as discussed by the authors.
Abstract: Polycyclic 1,2,3-trithiolans have been made by reacting the olefins exo- and endo-cyclopentadiene dimer, cyclopentadiene trimer, and norbornene with elemental sulphur. The reaction with norbornadiene produced an episulphide. The vibrational (i.r. and Raman) and magnetic (1H and 13C n.m.r.) spectra of the trithiolans are consistent with a five-membered ring structure with three adjacent sulphur atoms in an exo-configuration. The trithiolans are chemically fairly stable but polymerise rapidly on heating above 180°C.
26 citations
26 citations
TL;DR: In this paper, the ionization potentials of norbornadiene were calculated by an ab initio many-body Green's function method using the photoelectron spectrum as recorded by Heilbronner and co-workers.
22 citations
TL;DR: In this paper, the preparation and spectroscopic properties of some platinum(II) complexes having a hydride ligand cis or trans to an sp 3 carbon are described.
TL;DR: Bis(..mu..-acetato)-bis(norbornadiene) dirhodium(I) has been structurally characterized as mentioned in this paper, which has an R/sub F/ of 0.028.
Abstract: Bis(..mu..-acetato)-bis(norbornadiene)dirhodium(I) has been structurally characterized. The compound has been shown to be an active catalyst for the isomerization of quadricyclane to norbornadiene. This material crystallizes in the centrosymmetric monoclinic space group P2/sub 1//c with unit cell constants (T = 20/sup 0/C) a = 9.7733 (10) A, b = 15.2859 (15) A, c = 12.1815 (14) A, and ..beta.. = 103.563 (8)/sup 0/. All 3151 unique reflections were used in the x-ray structure analysis which refined to an R/sub F/ of 0.028. The Rh(1)--Rh(2) distance is 3.1050 (7) A. Each Rh atom is bonded to two oletin moieties of a norbornadiene ligand and to two oxygen atoms of the bridging acetate ligands. Each Rh coordination sphere has two approximate square-planar configuration with average Rh--oletin and Rh--O distances of 1.975 (4) and 2.106 (7) A, respectively. The Rh atoms lie 0.098 and 0.157 A out of their respective coordination planes. The dihedral angle formed between these planes is 50.1/sup 0/, while the angle between the planes defined only by the Rh and acetate oxygens is 40.2/sup 0/. Hydrogen atoms on the norbornadiene groups are within van der Waals contact distances, indicative of strong steric interactions between the ligands of the dimer. 4more » figures, 8 tables.« less
TL;DR: Several dinuclear arsenic bridged carbonyl complexes with Fe, Mn, and mainly Co bonds catalyse the dimerization of norbornadiene as discussed by the authors, which can be directed exclusively to the exo-trans-exo or the Binor-S dimer.
TL;DR: The catalytic cyclodimerization of norbornadiene by reaction with nickel atoms has been re-investigated in this paper, and a cyclotrimer of exotrans-exo-trans-end-3-nickela-pentacyclo is subsequently formed.
TL;DR: In this article, the results of the treatment of norbornene, norbornadiene, benzonorbornadienes, and chloro-and methoxy-benzonor-bornadienes with thallium(III) acetate in methanol have been reported.
TL;DR: The photo-catalysed hydrogenation of norbornadiene in the presence of chromium hexacarbonyl has been studied at pressures of up to 80 Bar as discussed by the authors.
TL;DR: In this article, the hydrogen transfer from isopropanol to various ketones such as cyclohexanone, 4-t-butylcyclohexenone and acetophenone is catalyzed by cationic rhodium(I) complexes of the type [Rh(Diene)L 2 ] + (Diene = 1,5-cyclooctadiene (COD) or norbornadiene(NBD); L 2 or L = mono- or bi-dentate phosphine ligands).
TL;DR: In this article, the rate law -d(Q)/dt = (0.64 s/sup -1/)(Cat)/sub 0/ adequately describes the results of kinetic studies carried out in the presence of large excesses of Q and NBD.
Abstract: Quadricyclane isomerization is catalyzed by red-orange (Rh(NBD)(AcO))/sub 2/ to give norbornadiene (75%) and two endo bis(norbornadienes), 1 (23%) and 2 (2%), at 25/sup 0/C. The reaction is characterized by the formation and disappearance of yellow Rh(III) intermediates. In CH/sub 2/Cl/sub 2/ at 25/sup 0/C the rate law -d(Q)/dt = (0.64 s/sup -1/)(Cat)/sub 0/ adequately describes the results of kinetic studies carried out in the presence of large excesses of Q and NBD and with (Cat)/sub 0/ > 10/sup -4/ M. At -50/sup 0/C rhodocyclohexane intermediates in the formation of dimers were detected and characterized by /sup 1/H and /sup 13/C)/sup 1/H) NMR spectra. The results are consistent with a stepwise mechanism involving insertion of Rh(I) into a cyclopropyl ring to form a rhodocyclobutane intermediate. 4 figures, 3 tables.
TL;DR: The mechanism of isomerisation of 2-(alkenyl)pyridines with group 6A hexacarbonyls is discussed in this article. But, the mechanism of the isomerization is not discussed in this paper.
Abstract: Reactions of 2-(alkenyl)pyridines with Group 6A hexacarbonyls and [M(CO)4(nbd)](M = Cr, Mo, or W; nbd = norbornadiene) are described Isomerisation of the alkenyl side chain occurs with 2-(CR1MeCR2)-, 2-(CH2CR1CH2CH2)- and 2-(CH2CHCH2CH2CH2)-C5H4N (R1, R2= H or Me) to give complexes of the type [M(CO)4L][L = 2-(prop-2′-enyl)- or 2-(substituted prop-2′-enyl)-pyridine] which have, in some cases, also been prepared directly from L; L is always bidentate The mechanism of isomerisation is discussed Spectroscopic studies provide no evidence for conformational isomerism involving the plane of the co-ordinated olefin Related reactions with Ph2P[CH2]2CHCH2 and Ph2P[CH2]3CHCH2 give [Mo(CO)4(Ph2PCH2CH2CHCH2)] and [Mo(CO)4(Ph2PCH2CH2CH2CHCH2)2] respectively
TL;DR: In this paper, the authors show that the product ratios obtained from the dimerisation of (7-MeC7H7) using a [(C 7H8)2Co2(CO)4]/[BF3·OEt2] catalyst system in dichloromethane, or the use of catalyst prepared from [C 7 H8]2Co 2 (CO) 4] and I2 without [BF3 ·OEt 2] are only consistent with a reaction scheme based on a mononuclear CoI catalyst, and suggest that a
TL;DR: In this article, it was shown that the interactions of the symmetry adapted orbitals of the subsystems are governed not only by their symmetry behaviour with respect to D2d in 1 and 2, or C2ν in 3 and 4, but also by the local symmetry at the points of attachment of subsystems.
Abstract: The photoelectron spectra of the hydrocarbons 1 to 4 have been recorded and interpreted by qualitative correlation with the spectra of their subsystems norbornadiene, quadricyclane, allene and cyclopropane.
It has been shown that the interactions of the symmetry adapted orbitals of the subsystems are governed not only by their symmetry behaviour with respect to D2d in 1 and 2, or C2ν in 3 and 4, but also by the local symmetry at the points of attachment of the subsystems.
TL;DR: In this paper, the addition of thiophenole to norbornadiene affords the 1:1 adducts 1, 2, 3 and 4 in a mixture that depends on the concentration of the starting material and on reaction temperature.
Abstract: Radikalische Addition von Thiophenol an Norbornadien liefert die 1:1-Addukte 1, 2, 3 und 4 in Gemischen, die von der Konzentration der Reaktionspartner und der Reaktionstemperatur abhangen (s. Tab. 1). Beim Arbeiten zwischen −40 und −20°C last sich aus den Gln. (d)–(f) ermitteln, das die H-Ubertragung von Thiophenol auf7 bzw.8 mit 4.3 bzw. 1.6 kcal/mol niedrigeren Aktivierungsenthalpien ablauft als die Norbornenyl-Nortricyclyl-Radikalumlagerung 7 ⇄ 8 (s. Tab. 2). Das Nortricyclyl-Radikal 8 ist um etwa 2.7 kcal/moi instabiler als das Norbornenyl-Radikal 7.
Radical Addition of Thiophenole to Norbornadiene
Radical addition of thiophenole to norbornadiene affords the 1:1 adducts 1, 2, 3 and 4 in a mixture that depends on the concentration of the starting material and on reaction temperature (table 1). Performing experiments between −40 and −20°C and using equations (d)–(f), it can be shown that the H-donation from thiophenole to 7 and 8 is lower in activation enthalpy by 4.3 and 1.6 kcal/mol, respectively than the norbornenyl-nortricyclyl radical rearrangement 7 ⇄ 8 (table 2). The nortricyclyl radical 8 is about 2.7 kcal/mol less stable than the norbornenyl radical 7.
TL;DR: The photoelectron spectra of 12-thia[4.4.3] have been investigated and the first bands have been interpreted as discussed by the authors, and the electronic structure of 3 and 4 allows us to rationalize and to predict the direction of the addition of cations and carbenes.
TL;DR: In this article, the energy dependence of the anisotropy parameters of the π and selected σ-bands of ethylene, 1,3-butadiene, benzene, cyclohexene and norbornadiene has been determined in the low energy region.
TL;DR: In this article, through-space orbital interaction between the ethylenic π and the Walsh orbitals of the oxirane ring was suggested by a lowfield shift in norbornadiene exo -oxide.
05 May 1979
Patent•
29 Jan 1979
TL;DR: The removal of color bodies from an olefinic or saturated endo-endo hexacyclic homodimer of norbornadiene or mixtures thereof is accomplished by the use of a serpentine clay as discussed by the authors.
Abstract: The removal of color bodies from an olefinic or saturated endo-endo hexacyclic homodimer of norbornadiene or mixtures thereof is accomplished by the use of a serpentine clay. Also acid bentonite clay or a montmorillonite clay can be used to remove the color bodies from the saturated dimer. The saturated dimer has a high density and a high heat of combustion making it useful as a missile fuel. Removal of the color bodies avoids possible catalyst poisoning in the hydrogenation of the olefinic to the saturated dimer. Also removal of the color bodies from the saturated dimer eliminates the possible problem of a material precipitating out on engine turbine blades and causing maintenance or operational problems.
Patent•
13 Dec 1979
TL;DR: In this paper, a saturated endo-endo dihydronorbornadiene hexacyclic dimer was used as a diluent for depressing the freezing point of the saturated hexacycic isomer which is a component of a high density missile fuel.
Abstract: Hydrogenolysis of a saturated endo-endo dihydronorbornadiene hexacyclic dimer involves the use of a catalytic amount of a Group VIII metal and the presence of hydrogen. The resulting pentacyclic isomers can be used as a diluent for depressing the freezing point of the saturated hexacyclic dimer which is a component of a high density missile fuel.
TL;DR: The photocycloaddition of a steroidal 4-en-3-one and a 4,6-dien-3 -one to bicyclo[2.2.1]heptene and bicyclo [2.3.2] heptadiene has been studied in this article.
Patent•
29 Jan 1979
TL;DR: Isomerization of a liquid, saturated endo-ende norbornadiene hexacyclic dimer involves the use of a catalytic amount of acidic alumina or a montmorillonite.
Abstract: Isomerization of a liquid, saturated endo-endo norbornadiene hexacyclic dimer involves the use of a catalytic amount of acidic alumina or a montmorillonite. The resulting isomeric product is solid, at ambient temperature, and can be used as a missile fuel.