Liquid-phase hydrogenation of 1,5-cyclooctadiene on zeolite-encapsulated noble metal-salen complexes

The preparation of palladium and rhodium complexes of the Schiff base salen (N,N'-bis-(salicylidene)-ethylenediamine) in the intracrystalline cavities of zeolites with the FAU and the EMT framework topology is reported. The host/guest compounds obtained are active catalysts for the selective hydrogenation of 1,5-cyclooctadiene in the liquid phase at 60 degrees C and under a hydrogen pressure of 1.5 MPa. In addition, the immobilization of palladium complexes of the chiral salen-type ligand R,R-N,N'-bis-(3,5-di-tertbutylsalicylide)-1,2-cyclohexanediamine in zeolites FAU and EMT is reported for the first time. These materials too are active catalysts for the selective hydrogenation of 1,5-cyclooctadiene. However, their ability to catalyse enantioselective hydrogenations remains to be demonstrated. (C) 1998 Elsevier Science B.V. All rights reserved.