title: (N-salicylidene)aniline derived Schiff base complexes of methyltrioxorhenium(VII): ligand influence and catalytic performance.
abstract: Methyltrioxorhenium(VII) (MTO) readily forms 1:1 adducts with several N-(salicylidene)aniline derived Schiff bases. If the aromatic rings of the N-(salicylidene)aniline ligands display non-donating or electron withdrawing substituent groups, the resulting MTO adducts show good activities in olefin epoxidations. However, steric effects seem to play a major role, leading often to instable o- and m-Schiff base-MTO adducts, while p-substituted Schiff bases usually lead to more stable adducts. In catalysis, electron-withdrawing substituents on the aniline moiety lead to better catalysts than electron donating ones. The gap between good catalysts and instable or non-existing compounds, however, is small. The general tendency, however, that good donors on the Schiff base ligands lead to shorter Re-O(Schiff base) bridges and lower catalytic activity, while the opposite is true with acceptor ligands on the Schiff bases, seems to be quite clear.
authors.affiliation: Molecular Catalysis, Catalysis Research Center, Technische Universität München, Lichtenbergstrasse 4,D-85747 Garching bei München, Germany.
authors.forename: Ming-Dong
authors.initials: MD
authors.lastname: Zhou
authors.forename: Yang
authors.initials: Y
authors.lastname: Yu
authors.forename: Alejandro
authors.initials: A
authors.lastname: Capapé
authors.forename: Kavita R
authors.initials: KR
authors.lastname: Jain
authors.forename: Eberhardt
authors.initials: E
authors.lastname: Herdtweck
authors.forename: Xiao-Rong
authors.initials: XR
authors.lastname: Li
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.forename: Shu-Liang
authors.initials: SL
authors.lastname: Zang
authors.forename: Fritz E
authors.initials: FE
authors.lastname: Kühn