Heterometallic Mg−Ba Hydride Clusters in Hydrogenation Catalysis
Michael Wiesinger, Christian Knüpfer, Holger Elsen, Jonathan Mai, Jens Langer, Sjoerd Harder
Abstract
Abstract Reaction of a MgN“ 2 /BaN” 2 mixture (N“=N(SiMe 3 ) 2 ) with PhSiH 3 gave three unique heterometallic Mg/Ba hydride clusters: Mg 5 Ba 4 H 11 N” 7 ⋅ (benzene) 2 ( 1 ), Mg 4 Ba 7 H 13 N“ 9 ⋅ (toluene) 2 ( 2 ) and Mg 7 Ba 12 H 26 N” 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.