12155-45-2Relevant academic research and scientific papers
Heterogeneous and homogeneous hydrogenation of styrene and stilbene chromium tricarbonyl complexes
Artemov,Sazonova,Lomakin
, p. 45 - 48 (2008/02/11)
Heterogeneous hydrogenation of the styrene and stilbene chromium tricarbonyl complexes by molecular hydrogen on skeletal nickel and palladium on carbon as catalysts was studied. As compared to styrene and stilbene, their arene chromium tricarbonyl analogs
Photochemical cis-trans isomerization of cis-(η6-1,2- diphenylethene)Cr(CO)3 and the molecular structure of trans-(η6-1,2-diphenylethene)Cr(CO)3
Coleman, Anthony,Draper, Sylvia M.,Long, Conor,Pryce, Mary T.
, p. 4128 - 4134 (2008/10/09)
Visible irradiation of cis-(η6-1,2-diphenylethene)Cr(CO) 3 results in an efficient conversion to the trans isomer as confirmed by NMR, room-temperature UV-vis spectroscopy, and low-temperature matrix isolation studies. Laser flash photolysis of trans-(η6-1,2- diphenylethene)Cr(CO)3 at 355 nm forms a solvated dicarbonyl species, (η6-1,2-diphenylethene)Cr(CO)2. Matrix isolation studies confirm that cis to trans isomerization occurs under low-energy irradiation (γexc > 400 nm), while photolysis with γexc = 313 nm is required to induce CO loss. Time-dependent density functional theory (TDDFT) calculations predict wavelength-dependent photochemical cis to trans isomerization for low-energy (γexc: > 400 nm) irradiation, while high-energy irradiation (γexc > 300 nm) populates excited states that are labile to CO loss.
Niobium(III)-induced reductive coupling of benchrotrenic aldehydes and ketones
Szymoniak, Jan,Luque, Lionel,Besancon, Jack,Moise, Claude
, p. 89 - 94 (2007/10/02)
The (arene)tricarbonylchromium(benchrotrenic)oxo compounds BctCOR (Bct = Cr(CO)3C6H5; R = H, alkyl or aryl) undergo a reductive coupling reaction with NbCl3(DME), leading to the mono- and bis-metallated alkenes, Bct(R)C=C(R)Ar and Bct(R)C=C(R)Bct, respectively.Such a mixture of mono- and bis-metallated products is obtained when the benchrotrenic ketones are used as substrates.Starting from benchrotrenic aldehyde 4, however, the exclusive formation of the mono-tricarbonylchromium trans-stilbene 5 takes place.This has been shown to occur by a two-step process.The Nb(III)-induced partial Cr(CO)3 decomplexation of the substrate is followed by the reductive coupling, preferentially between the free aldehyde formed and the benchrotrenic aldehyde.The differences in the reactivity observed are explained in terms of the favored ? (in plane) geometry for the Nb(III)-Lewis acid activation of the carbonyl toward metalloxirane nucleophilic attack.Nb(III) reagent / reductive coupling / benchrotrene / stereoselectivity
η6-Chromiumtricarbonyl complexes of stilbene and 4,4'-dimethoxystilbene: slipping off the ligands enables cis-trans isomerization
Todres, Z. V.,Ionina, E. A.
, p. 193 - 195 (2007/10/02)
η6-Chromiumtricarbonyl complexes of stilbene and 4,4'-dimethoxystilbene (both in the cis form as ligands) were prepared.The complexes are stable as dry solids, but disintegrate during exposure at 25 deg C in argon, with liberation of the ligands.They are returned as a mixture of cis-trans isomers.The conversion of cis-trans types observed depends not on the spontaneous isomerization of a ligand in a complex, but on the interaction between the slipping ligand and chromium sesquioxide - the product of the transformation of the Cr(CO)3 fragment.
Organometallic clusters with face-capping arene ligands. 4. Tris(cyclopentadienylcobalt) clusters with μ3-alkenyl- and μ3-alkylbenzenes
Wadepohl, Hubert,Büchner, Klaus,Herrmann, Michael,Pritzkow, Hans
, p. 861 - 871 (2008/10/08)
The (CpCo)3(μ3-(1-alkenyl)benzene) clusters 5a,b and 6a,b are prepared from CpCo(C2H4)2 (3) and α-methylstyrene, β-methylstyrene, 1,1-diphenylethylene, and stilbene. From 3 and 4-methoxystilbene a mixture of the coordination isomers of (CpCo)3(μ3-4-methoxystilbene) (7a,b) is obtained. (CpCo)3(μ3-1,1-diphenylpropene) (10) is formed from 1,1-diphenylpropene and CpCo(C6Me6) (4). Styrene and 3 do not give a μ3-styrene cluster, but (CpCo)3(μ3-4-methylstyrene) (8) and (CpCo)3(μ3-4-methoxystyrene) (9) are isolated in good yield from the reaction of 3 and the corresponding substituted styrenes. Allylbenzene, 4-methoxy(allyl)benzene, and 4-phenyl-1-butene are catalytically rearranged by 3 or 4 to the (1-alkenyl)benzene derivatives. By reaction of the further ligands with 3 molar equiv of 3 the (CpCo)3(μ3-(1-alkenyl)arene) complexes 5b, 11, and 12 are formed. The X-ray crystal structures of 5b and 6a have been determined. Crystal data: 5b, monoclinic, P21, a = 8.725 (5) A?, b = 7.542 (5) A?, c = 15.151 (6) A?, β = 103.17 (4)°, Z = 2, R = 0.026, Rw = 0.027 (w = σ-2(F)) with 2893 reflections; 6a·0.5C7H8, triclinic, P1, a = 8.734 (4) A?, b = 11.470 (5) A?, c = 12.791 (6) A?, α = 85.37 (3)°, β = 83.81 (3)°, γ = 83.52 (3)°, Z = 2, R = 0.043, Rw = 0.038 (w = σ-2(F)) with 5795 reflections. The face-capping arene rings in both compounds are coplanar with the (CpCo)3 triangles and adopt a staggered orientation. Bond length alternation within the μ3-η2:η2:η 2-coordinated arene rings is only slight, with a mean difference of 0.03 A? between longer and shorter carbon-carbon bonds. In solution rotation of the arenes on top of the (CpCo)3 triangles takes place, which can be frozen out at low temperature. The chemical reactivity of the title compounds is low. The μ3-arene ligands cannot be displaced by other arenes or by two-electron donors. Bromination, hydrosilylation, and cyclopropanation of the exocyclic alkenyl group of 5b cannot be achieved. However, catalytic hydrogenation of 5b to give (CpCo)3(μ3-n-propylbenzene) (18) proceeds readily. The relationship of the μ3-arene clusters to the metal surface adsorption states of benzene is discussed.
Addition de Carbanions α Benchrotreniques sur Divers Aldehydes non Enolisables; Evolution des Produits Primaires d'Addition par Oxidation d'Oppenauer-Woodward, influence de la Substitution
Senechal-Tocquer, M. C.,Senechal, D.,Bihan, J. Y. Le,Gentric, D.,Caro, B.
, p. 353 - 364 (2007/10/02)
Aromatic hydrocarbons complexed with a Cr(CO)3 unit react with benzaldehydes and furfural in THF and in presence of t-BuOK at the benzylic position to give condensation products in good yields.Formation of ketones by in situ Oppenauer-Woodward oxidation is observed.Influence of ring substituents on this formation is discussed.
FORMATION ET REACTIVITE DES CARBANIONS BENCHROTRENIQUES DANS LE THF. ADDITION D'OXALATE D'ETHYLE ET DE BENZALDEHYDE, EVOLUTION DES PRODUITS D'ADDITION PAR OXYDATION D'OPPENAUER-WOODWARD
Senechal-Tocquer, M.-C.,Senechal, D.,Bihan, J-Y. Le,Gentric, D.,Caro, B.
, p. C5 - C8 (2007/10/02)
Aromatic hydrocarbons complexed by a Cr(CO)3 unit react in THF and in the presence of t-BuOK, at the benzylic position with (COOEt)2 and PhCHO to give good yields of condensation products.With PhCHO formation of ketone via in situ Oppenauer-Woodward oxidation, is observed.
