III International Conference

PP-II-137THE FORMATION OF PALLADIUM NANOSCALE HYDROGENATIONCATALYSTS UNDER THE ACTION OF LITHIUM ALUMOHYDRIDETitova Yu.Yu., Belykh LB., Schmidt F.K.Irkutsk State University, Irkutsk, RussiaE-mail: fkschmidt@chem.isu.ruThe nature and properties of palladium nanoscale hydrogenation catalysts based onPd(acac) 2 and LiAlH 4 have been studied. It has been shown that Pd(acac) 2 reduction withLiAlH 4 is accompanied by the side process of decomposition to give palladium aluminides.The reasons for an abrupt increase of the catalyst specific activity and its extreme type ofdependency on the storage duration of LiAlH 4 in THF solution have been found.The catalysts of Ziegler type demonstrate an activity in different processes of organicsynthesis most known of which are as follows: olefin and diene polymerization; isomerization;carbonylation and hydroformylation; oligomerization; coupled diene telomerization as well ashydrogenation of unsaturated compounds including asymmetrical hydrogenation. Along withconventional coreagents of these systems viz organoaluminum compounds, the alumo- andborohydrides of alkaline metals are widely used as reductants as well.In this paper formation and properties of palladium nanoscale hydrogenation catalystsformed in the course of Pd(acac) 2 reduction by lithium alumohydride have been considered. Ithas been shown that along with Pd(acac) 2 reduction by lithium alumohydride a side process ofthe catalytic decomposition of the formed alane occurs that leads to palladium aluminides ofdifferent composition. That fact is probably the main reason for relatively moderate activity ofthe discussed catalytic system in the alkene hydrogenation (30 mol substrate (g-at Pd min) -1compared to earlier studied palladium nanoscale catalysts formed under the action of AlEt 3[1]. An influence of different parameters on the properties of palladium hydrogenationcatalysts has been studied. It has first been found that the properties of Pd(acac) 2 – LiAlH 4catalytic system depend on the duration of LiAlH 4 in THF solution storage under inertatmosphere. An abrupt growth of the catalyst specific activity (more than by a factor of 7) hasbeen observed. By the method of NMR 27 Al spectroscopy it has been established that such aphenomenon is connected with a slow LiAlH 4 partial hydrolysis and oxidation to give“aluminoxanes”. The latter undergo side process of the catalytic decomposition resulting inpalladium aluminide and hydrogen formation to a lesser degree than LiAlH 4. In addition,might arise as stabilizer of palladium nanoparticles.References1. Belykh L.B..,Goremyka T.V, Skripov N.I.,Umanets V.A., Schmidt F.K..// Kinet. Katal. - 2006. Т.47, № 3. С. 773-780.414