279-19-6Relevant articles and documents
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.
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.
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.
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.
