279-19-6Relevant academic research and scientific papers
Simple Access to the Heaviest Alkaline Earth Metal Hydride: A Strongly Reducing Hydrocarbon-Soluble Barium Hydride Cluster
Wiesinger, Michael,Maitland, Brant,F?rber, Christian,Ballmann, Gerd,Fischer, Christian,Elsen, Holger,Harder, Sjoerd
, p. 16654 - 16659 (2017)
Reaction of Ba[N(SiMe3)2]2 with PhSiH3 in toluene gave simple access to the unique Ba hydride cluster Ba7H7[N(SiMe3)2]7 that can be described as a square pyramid spanned by five Ba2+ ions with two flanking BaH[N(SiMe3)2] units. This heptanuclear cluster is well soluble in aromatic solvents, and the hydride 1H NMR signals and coupling pattern suggests that the structure is stable in solution. At 95 °C, no coalescence of hydride signals is observed but the cluster slowly decomposes to undefined barium hydride species. The complex Ba7H7[N(SiMe3)2]7 is a very strong reducing agent that already at room temperature reacts with Me3SiCH=CH2, norbornadiene, and ethylene. The highly reactive alkyl barium intermediates cannot be observed and deprotonate the (Me3Si)2N? ion, as confirmed by the crystal structure of Ba14H12[N(SiMe3)2]12[(Me3Si)(Me2SiCH2)N]4.
195. Carbon Participation in the Solvolysis of 6- and 7-Substituted 2-Norbornyl p-Toluenesulfonates
Flury, Peter,Grob, Cyril A.
, p. 1971 - 1980 (1983)
The solvolysis rates and products of several 7-anti-substituted 2-endo-norbornyl p-toluenesulfonates 11 have been determined and compared with those of the previously reported 6-exo-substituted 2-exo-norbornyl p-toluenesulfonates 1.Although the number of bonds between the substituent and the reaction site is the same in the two series, the inductive effect of the substituents is transmitted far more strongly in the 6-exo-2-exo-series 1 than in the 7-anti-2-exo-series 11; i.e. their inductivities differ widely.It is concluded that through space induction involves graded bridging of the substituent-bearing C-atom to the incipient cationic center at C(2) and that this involves differential bridging strain.The different reactivities of unsubstituted 2-exo- and 2-endo-norbornyl derivatives can then be ascribed to a stereoelectronic effect.
Facile Activation of Dihydrogen by Long-lived Carbonium Ions on Silica-Alumina Catalysts. An Example of a Simple -Type Reaction
Rooney, John J.
, p. 1301 - 1302 (1983)
Silica-alumina catalyses the gas phase hydrogenation of norbornadiene and 1-chloroadamantane at the surprisingly moderate temperature of 90 deg C showing that when the carbonium ion intermediates are long-lived the R+ ...O- - surface species reacts with dihydrogen in a -type reaction, and does so far more readily than the corresponding H+ ...O- - cation-anion pair.
Heterometallic Mg?Ba Hydride Clusters in Hydrogenation Catalysis
Wiesinger, Michael,Knüpfer, Christian,Elsen, Holger,Mai, Jonathan,Langer, Jens,Harder, Sjoerd
, p. 4567 - 4577 (2021/09/09)
Reaction of a MgN“2/BaN”2 mixture (N“=N(SiMe3)2) with PhSiH3 gave three unique heterometallic Mg/Ba hydride clusters: Mg5Ba4H11N”7 ? (benzene)2 (1), Mg4Ba7H13N“9 ? (toluene)2 (2) and Mg7Ba12H26N”12 (3). Product formation is controlled by the Mg/Ba ratio and temperature. Crystal structures are described. While 3 is fully insoluble, clusters 1 and 2 retain their structures in aromatic solvents. DFT calculations and AIM analyses indicate highly ionic bonding with Mg?H and Ba?H bond paths. Also unusual H????H? bond paths are observed. Catalytic hydrogenation with MgN“2, BaN”2 and the mixture MgN“2/BaN”2 has been studied. Whereas MgN“2 is only active in imine hydrogenation, alkene and alkyne hydrogenation needs the presence of Ba. The catalytic activity of the MgN”2/BaN“2 mixture lies in general between that of its individual components and strong cooperative effects are not evident.
Alkene Transfer Hydrogenation with Alkaline-Earth Metal Catalysts
Bauer, Heiko,Thum, Katharina,Alonso, Mercedes,Fischer, Christian,Harder, Sjoerd
supporting information, p. 4248 - 4253 (2019/03/07)
The alkene transfer hydrogenation (TH) of a variety of alkenes has been achieved with simple AeN′′2 catalysts [Ae=Ca, Sr, Ba; N′′=N(SiMe3)2] using 1,4-cyclohexadiene (1,4-CHD) as a H source. Reaction of 1,4-CHD with AeN′′2 gave benzene, N′′H, and the metal hydride species N′′AeH (or aggregates thereof), which is a catalyst for alkene hydrogenation. BaN′′2 is by far the most active catalyst. Hydrogenation of activated C=C bonds (e.g. styrene) proceeded at room temperature without polymer formation. Unactivated (isolated) C=C bonds (e.g. 1-hexene) needed a higher temperature (120 °C) but proceeded without double-bond isomerization. The ligands fully control the course of the catalytic reaction, which can be: 1) alkene TH, 2) 1,4-CHD dehydrogenation, or 3) alkene polymerization. DFT calculations support formation of a metal hydride species by deprotonation of 1,4-CHD followed by H transfer. Convenient access to larger quantities of BaN′′2, its high activity and selectivity, and the many advantages of TH make this a simple but attractive procedure for alkene hydrogenation.
Pyridyl-decorated self-folding heptaamide cavitands as ligands in the rhodium-catalyzed hydrogenation of norbornadiene
Korom, Sasa,Ballester, Pablo
, p. 4276 - 4282 (2014/07/21)
The different binding geometries exhibited in solution by the Rh I cationic complexes of three regioisomeric self-folding heptaamide cavitands, each decorated with one pyridyl group at the upper rim, are taken into account to explain the diverse distributions of products obtained when these complexes are employed as catalysts for the hydrogenation of norbornadiene. Copyright
Catalytic hydrogenation of norbornadiene by a rhodium complex in a self-folding cavitand
Sarmentero, Maria Angeles,Fernandez-Perez, Hector,Zuidema, Erik,Bo, Caries,Vidal-Ferran, Anton,Ballester, Pablo
supporting information; experimental part, p. 7489 - 7492 (2010/12/20)
It's a wrap! The inclusion of [Rh(nbd)2]BF4 (nbd=norbornadiene) in a deep-cavity cavitand produces a catalytically active species that promotes the hydrogenation of norbornadiene to norbornene (see picture). The structure of the cavitand acts as a second-sphere ligand and modifies the stability, selectivity, and reactivity observed for the free organometallic complex in solution.
The 2-norbornyl cation via the fragmentations of exo- and endo-2-norbornyloxychlorocarbenes: Distinction without much difference
Moss,Zheng,Sauers,Toscano
, p. 8109 - 8116 (2007/10/03)
exo- and endo-2-norbornyloxychlorocarbenes (7) were generated photochemically from the corresponding diazirines (6). Both carbenes fragmented to [2-norbornyl cation (carbon monoxide) chloride] ion pairs in MeCN or 1,2-dichloroethane solutions. Products included exo-norbornyl chloride (8), endo-norbornyl chloride (9), norbornene (10), and nortricyclene (11). Fragmentation activation energies were very low (5 s-1 in MeCN). Due to chloride return within the ion pairs, product distributions from exo- and endo-7 differed, with more endo-chloride formed from the endo-carbene: the 8/9 product ratio in MeCN was ～41 from exo-7, but only 4.6 from endo-7. Norbornene, formed by proton transfer to Cl- within the ion pairs, was a major product in both cases (44% from exo-7 and 62% from endo-7). In MeOH/MeCN, up to 28% of exo-2-norbornyl methyl ether formed at the expense of some of the norbornene, but even in 100% MeOH, the norbornyl chloride products of ion pair return still accounted for 46% and 31% of the exo-7 and endo-7 product mixtures (accompanied by 26-32% of norbornene). Electronic structure calculations on the ground states and fragmentation transition states of exo-7 and endo-7 are presented.
Chemical Consequences of Long-Range Orbital Interactions in Norbornane-1,4-diol Monosulfonate Esters
Bastiaansen, Petrus M. F. M.,Wijnberg, Joannes B. P. A.,Groot, Aede de
, p. 4240 - 4250 (2007/10/02)
Seven monotosylated 1,4-diols with the rigid norbornane skeleton were treated with a strong base in refluxing benzene to find out whether these compounds react by initial heterolysis of the tosylate ester bond induced by long-range orbital interactions.The tosylates 1-7 were designed to investigate the influence of the ?-relay (U-, sickle-, or W-shaped) between the donor and acceptor end of the system, to check whether primary carbocationic ion pairs could act as intermediates, and to study conformational influences on reactivity and product formation.Tosylate 1 with a U-like arrangement of the ?-relay reacted relatively slowly and followed reaction pathways in which no long-range orbital interactions are involved.The reaction outcome of tosylate 2 which possesses a sickle-like arrangement of the ?-relay indicates two competitive processes with and without the involvement of long-range orbital interactions.The secondary tosylates 3, 6, and 7 which all possess a W-like arrangement reacted relatively fast and showed predominantly homofragmentation.Although an ideal W-like arrangement is present in the primary tosylates 4 and 5, no reactions in which long-range orbital interactions are involved were observed.The tosylates 6 and 7 in which the tosylate group is conformationally mobile can give rise to mixtures of products.The ratio in which these products are formed can be rationalized by using the Curtin-Hammett principle.
Reactions of Thianthrene Cation Radical with Acyclic and Cyclic Alcohols
Shine, Henry J.,Yueh, Wang
, p. 3553 - 3559 (2007/10/02)
Thianthrene cation radical perchlorate (Th(.+)*ClO4(-)) reacted readily with cycloalkanols (C5, C7, C8, and C12), alkan-2-ols (C3, C5, C6, and C8), 3-hexanol, neopentyl alcohol, a number of benzyl alcohols, dl- and (S)-1-phenylethanol, cyclopentyl- and cyclohexylmethanols, the exo- and endo-borneols, and norborneols.Reactions were carried out with an excess of the alcohol in acetonitrile solution containing 2,6-di-tert-butyl-4-methylpyridine.Products were alkenes, ethers, and N-substituted acetamides, depending on the structure of the alcohol.Thianthrene (Th) and its 5-oxide (ThO) were formed in equal amounts.The sum of amounts of products from the alcohol was equal to the amount of ThO.All reactions are interpretable on the basis of the ultimate formation and further reactions of a 5-alkoxythianthreniumyl ion (ROTh(+)).The predominant formation of nortricyclene from the norborneols is striking and is discussed.Swern-Moffatt-type oxidations of the alcohols were not observed.
