Showing papers on "Norbornadiene published in 1988"
TL;DR: Catalyse par les complexes Rh(PPh 3 ) 3 Cl et [Rh(nbd)(diphos-4)]BF 4 (nbd=norbornadiene, diphos4=bis-diphenylphosphino-1,4 butane)
Abstract: Catalyse par les complexes Rh(PPh 3 ) 3 Cl et [Rh(nbd)(diphos-4)]BF 4 (nbd=norbornadiene, diphos-4=bis-diphenylphosphino-1,4 butane)
164 citations
TL;DR: In this paper, a certain nombre de coordinats monodentes et bidentes formant cis−L 2 Mo(CO) 4, influence des facteurs steriques et electroniques dans la determination de la force de la liaison Mo−L
Abstract: Enthalpie de la reaction de (NBD)Mo(CO) 4 avec un certain nombre de coordinats monodentes et bidentes formant cis−L 2 Mo(CO) 4 . Influences des facteurs steriques et electroniques dans la determination de la force de la liaison Mo−L
45 citations
38 citations
TL;DR: In this paper, the triplet-triplet energy transfer mechanism was used for the photoisomerization of cis-and trans-piperylene with high quantum efficiency by Cu(diphos)BH/sub 4/ and Cu(prophos), BH/ sub 4/ (1,2-bis(diphenylphosphino)ethane).
Abstract: Photoisomerization of cis- and trans-piperylene can be sensitized with high quantum efficiency by Cu(diphos)BH/sub 4/ (diphos is 1,2-bis(diphenylphosphino)ethane) and Cu(prophos)BH/sub 4/ (prophos is 1,3-bis(diphenylphosphino)propane). Sensitization is accompanied by quenching of the emissive /sup 3/(/sigma/-a/sub /pi//) excited state in each copper(I) complex, and the two processes occur with identical Stern-Volmer kinetics. Measurements of the trans/cis diene ratio at the photostationary state can be used to estimate the triplet-state energy as 60-61 kcal for Cu(diphos)BH/sub 4/ and > 61 kcal for Cu(prophos)BH/sub 4/; additional evidence suggests that 66-67 kcal is a reasonable value for the latter complex. Collectively, the results support the assignment of triplet-triplet energy transfer as the primary mechanism for sensitization and quenching in these systems. This mechanism also can accommodate earlier reports that Cu(diphos)BH/sub 4/ and Cu(prophos)BH/sub 4/ sensitize the valence isomerization of norbornadiene to quadricyclene with markedly different quantum efficiencies. 17 refs., 6 figs., 2 tabs.
37 citations
27 citations
TL;DR: In this article, the bromofluorination of norbornadiene using NBS in the presence of the new fluorinating agent Et3N/3HF leads to a 3:2 mixture of 3-exo-bromo-5 exo-fluoronortricyclane 1 and 3exo bromo -5-endomaine-endomorphine-fluoronitriou-cyclane 2.
25 citations
TL;DR: In this paper, an immobilized complex of trimethyldicyanoquadricyclane (TMDC-Q) supported on polyaminesulfone modified alumina beads has been prepared.
Abstract: N,N′-Disalicylidene-4-carboxy-1,2-phenylenediiminatocobalt(II) supported on polyaminesulfone modified alumina beads has been prepared. The immobilized complex revealed efficient catalysis for the conversion of trimethyldicyanoquadricyclane (TMDC-Q) to the corresponding norbornadiene (TMDC-NBD). Using a bench-scale fixed bed reactor, TMDC-Q in chlorobenzene (1 mol dm−3) isomerized to TMDC-NBD quantitatively during the flow through catalyst bed of only 20 cm with the temperature increase from 24.5 °C to 75 °C.
22 citations
TL;DR: In this paper, 18-electron rhodacarboranes with a 2-methylenenenorbornadienyl ligand, η 2, η 3 -coordinated to a rhodium atom of closo-3,3-(η 2,η 3)-C 7 H 7 CH 2 )-1,2-R 1 R 2 -3,1, 2-RhC 2 B 9 H 9 (IIIa-IIId, R 1 R 2 ǫ Me (a), R
21 citations
TL;DR: In this article, the rotational dependence of the dilution factor has been investigated by exciting different positions, or average J values, within a single vibrational band, and the relative energy contents of various vibrational modes, whose fluorescence was observed, have also been determined.
Abstract: Infrared laser induced fluorescence has been used to probe the extent of state mixing, as well as its rotational dependence, in the C–H stretch fundamental region of norbornadiene in the electronic ground state. Both total and dispersed IR fluorescence were collected from molecules, cooled, and isolated in a molecular beam, after excitation with an infrared optical parametric oscillator. The dilution factor, which is inversely related to the number of coupled states, has been measured for four C–H stretch bands, and in addition, the rotational dependence of the dilution factor has been investigated by exciting different positions, or average J values, within a single vibrational band. The relative energy contents of various vibrational modes, whose fluorescence was observed, have also been determined. An approximate average coupling width of 0.05 cm−1 can be derived from the dilution factors and the calculated state density of the rovibrational bath states {‖li〉} that are permitted by symmetry and angular...
20 citations
TL;DR: The variable-temperature IR spectra of (η 4 -norbornadiene)Fe(CO) 3 and related complexes reveal a coalescence phenomenon involving the CO stretching vibrational bands as discussed by the authors.
20 citations
TL;DR: The tetrasulfido complexes [MoS4]2-, [WS4] 2-, [VS4]3-, and [ReS4]- photolyze in solution in the presence of air according to the stoichiometry [MS4]n- + 02 -> [M02S2]n + S2] as discussed by the authors.
Abstract: The tetrasulfido complexes [MoS4]2-, [WS4]2-, [VS4]3-, and [ReS4]- photolyze in solution in the presence of air according to the stoichiometry [MS4]n- + 02 -> [M02S2]n- + S2. The diatomic sulfur can be scavenged by norbornadiene or tetramerizes to yield stable S8. Quantum yields are strongly wavelength-dependent. For all complexes the reactive excited states are of the ligand to metal charge transfer type.
TL;DR: In this paper, the deuterium atoms add predominantly to the same (endo) face of the olefins as that coordinated to the dimethylplatinum moiety.
Abstract: Reduction of (diolefin)dialkylplatinum(II) complexes with dihydrogen over a platinum black catalyst is accompanied by interchange of hydrogen among the organic groups and gaseous dihydrogen. Exchange of hydrogens between an alkane solvent and these organic groups also occurs during the reaction, but only relatively slowly. An examination of the stereochemistry of reduction of (norbornadiene)dimethylplatinum(II) with D/sub 2/ indicates that the deuterium atoms add predominantly to the same (endo) face of the olefins as that coordinated to the dimethylplatinum moiety. Reduction of uncomplicated norbornadiene under the same conditions yields norbornane having primarily exo C-D bonds. These experiments are compatible with a mechanism for the reduction involving adsorption of the (diolefin)dialkylplatinum(II) complex on the surface of the platinum catalyst via its platinum atom, conversion of the organic moieties of the soluble (diolefin)dialkylplatinum complex to platinum-surface alkyls, and interchange of hydrogen atoms between these surface alkyls via a mobile pool of platinum-surface hydrogen atoms. Combination of the surface alkyls with surface hydrogen yields alkanes in a final irreversible step. Comparison of the evidence from deuterium-interchange experiments conducted under mass transport limited and reaction rate limited conditions is consistent with the hypothesis that the concentrations of hydrogen on the platinum surface is lower under massmore » transport limited conditions.« less
TL;DR: In this paper, the reaction of [Rh(diene)(acac)] (diene=cyclooctadiene or norbornadiene; acac=acetylacetonate) with bidentate ligands of the type Ph2P(CH2)nSR (n=1, 2 or 3; R=Me, Et, Ph, not all combinations) or cis-Ph2PCHCHPPh2 leads to [Rh[diene]-+ or [RH[LL]2]+, depending on the stoichiometry
TL;DR: In this article, a 1.4-addition of the two fragments formed from homolytic cleavage of the cabon-sulfur bond was proposed to obtain the (4+2)-cycloadducts.
TL;DR: Ceric ammonium nitrate is an excellent reagent for preparing carboxylic esters from α-alkoxymalonic acids by oxidative biscarboxylation as discussed by the authors.
TL;DR: In this article, new palladium complexes of cyclopropenylidenes of the type of trans-Cl2Pd(CP)(Py-X) have been synthesized.
TL;DR: In this article, the photochemistry of quadricyclane (Q) was explored by single-photon excitation to high vibrational levels, where the v = 4-7 carbon-hydrogen overtones were recorded by using intracavity absorption and photoacoustic detection.
Abstract: The photochemistry of quadricyclane (Q) was explored by single-photon excitation to high vibrational levels. Spectra of the v = 4-7 carbon-hydrogen overtones were recorded by using intracavity absorption and photoacoustic detection. These spectra were compared to the infrared fundamental spectrum and assigned. Excitation of the v = 5 and v = 6 bands of cyclopropanoid and methylenic hydrogens leads to reaction. At least one intermediate, probably a vibrationally excited form of norbornadiene (N), must be involved because partitioning among various reactions channels is pressure dependent. Apparent rate constants were measured and correlated with variations in pressure according to the Stern-Volmer relationship. Experimental values were compared with rate constants calculated by RRKM theory. Although there is a modest amount of excess reaction observed for the lowest excitation energies above threshold, overall evaluation provides no significant evidence for concentration of energy in localized modes for times that are long compared with reaction times.
TL;DR: Mecanisme de la synthese des N-morpholine-, -piperidine- and -pyrrolidinecarboxylates de vinyle a partir d'acetylene, de dioxyde de carbone and des dialkylamines correspondantes.
TL;DR: In this article, the preparation of cobalt(II) deuteroporphyrin and cobalt (II) tetrakis(p-sulfonatophenyl)porphine anchored on alumina beads coated with polyaminesulfone-A was described.
Abstract: Methods are described for the preparation of cobalt(II) deuteroporphyrin and cobalt(II) tetrakis(p-sulfonatophenyl)porphine anchored on alumina beads coated with polyaminesulfone-A. Wavelength dispersive X-ray microanalysis showed that the cobalt(II) porphine distributes within the catalyst outer surface layer of ca. 100 μm depth. The catalysts are highly active for the cycloreversion of quadricyclane to norbornadiene. A detailed kinetics of the isomerization using an isothermal recycle reactor gave a rate expression of Langmuir–Hinshelwood type. The catalysts gradually lose their activity, which can be regenerated completely by heating the catalysts at 200 °C in vacuo.
TL;DR: In this article, the eight-membered heterocycle t BuAs(NSN) 2 As t Bu (4), which possesses a boat-like structure, can be incorporated into carbonyl metal complexes either as a monodentate or as a bidentate chelating ligand.
TL;DR: In this article, the tetrameric complexes [CuX(PFcPh 2 )] 4 (1, X= Cl; 2, X = Br) and their bipyridyl (bpy) derivatives were prepared.
TL;DR: Dimethyldioxirane, 3 catalyzes the isomerization of quadricyclane to norbornadiene as discussed by the authors, and the unusual orbital occupancy in 3 may be responsible for these observations.
TL;DR: In this paper, the structure of (η-C5H5)2Rh2{C(CF3C2CF3)H]2 (C6H4) was derived from the reaction with benzene, which was confirmed by single crystal X-ray diffraction studies.
TL;DR: In this article, it was shown that olefin bond migration takes place in a η3-allylmetal hydride intermediate produced from a [(η2-adpp)W(CO)4] precursor in which adpp is coordinated cis to a vacant coordination site through the Olefinic linkage.
Patent•
26 Feb 1988TL;DR: In this paper, two polyoxoanion supported metal complexes are shown to be useful in olefin hydrogenation in organic solvents, which are called Ax[LnIr(1).X2M15M'3o62]x-and Ay[Llir(1), X2M9M' 3o40]y-, where A is a countercation; L is an ole fin-oxygen ligand or dioxygen; n = 1 or 2; X is a hetero atom selected from the group consisting of
Abstract: The present invention discloses two polyoxoanion supported metal complexes found to be useful in olefin hydrogenation. The complexes are novel compositions of matter which are soluble in organic solvents. In particular, the compositions of matter comprise Ax[LnIr(1).X2M15M'3o62]x- and Ay[LnIr(1).X2M9M'3o40]y-, where A is a countercation; L is an olefinic ligand or dioxygen; n = 1 or 2; X is a hetero atom selected from the group consisting of B, Si, Ge, P, As, Se, Te, I, Co, Mn and Cu; M = W or Mo; M' = Nb, V, Ti, Zr, Ta and Hf; x < 15; and y < 15.
TL;DR: In this article, the reaction of norbornadiene(tricarbonyl)iron with aryl-lithium reagents at low temperature, followed by alkylation of the intermediate acylmetallates with Et3OBF4 in aqueous solution at 0 °C gives novel ring-opened diallyl complexes, C7H8(CO)2FeC(OC2H5)Ar.
Abstract: Reaction of norbornadiene(tricarbonyl)iron with aryl-lithium reagents at low temperature, followed by alkylation of the intermediate acylmetallates with Et3OBF4 in aqueous solution at 0 °C gives novel ring-opened diallyl complexes, C7H8(CO)2FeC(OC2H5)Ar.
TL;DR: In this paper, the cycloaddition of 3-t-butyl-1,1,2,2-tetrafluoro, 2-disilacyclobutane (1) to various cyclic dienes have been studied under photochemical conditions.
TL;DR: Norbornadiene ayant des groupes carboxylate et/ou amide substitue en positions 2 and 3 and ayant un groupe vinyl a l'extremite du substituant en 2 as mentioned in this paper.
Abstract: Norbornadiene ayant des groupes carboxylate et/ou amide substitue en positions 2 et 3 et ayant un groupe vinyl a l'extremite du substituant en 2