title: Unprecedented Carbonato Intermediates in Cyclic Carbonate Synthesis Catalysed by Bimetallic Aluminium(Salen) Complexes.
abstract: The mechanism by which [Al(salen)]2 O complexes catalyse the synthesis of cyclic carbonates from epoxides and carbon dioxide in the absence of a halide cocatalyst has been investigated. Density functional theory (DFT) studies, mass spectrometry and (1) H NMR, (13) C NMR and infrared spectroscopies provide evidence for the formation of an unprecedented carbonato bridged bimetallic aluminium complex which is shown to be a key intermediate for the halide-free synthesis of cyclic carbonates from epoxides and carbon dioxide. Deuterated and enantiomerically-pure epoxides were used to study the reaction pathway. Based on the experimental and theoretical results, a catalytic cycle is proposed.
authors.affiliation: Green Chemistry Centre of Excellence, Department of Chemistry, The University of York, York, YO10 5DD, UK.
authors.forename: José A
authors.initials: JA
authors.lastname: Castro-Osma
authors.affiliation: Green Chemistry Centre of Excellence, Department of Chemistry, The University of York, York, YO10 5DD, UK. michael.north@york.ac.uk.
authors.forename: Michael
authors.initials: M
authors.lastname: North
authors.affiliation: CAT Catalytic Center, RWTH Aachen University, Worringerweg 2, D-52074, Aachen, Germany. Willy.Offermans@CatalyticCenter.RWTH-Aachen.de.
authors.forename: Willem K
authors.initials: WK
authors.lastname: Offermans
authors.affiliation: Lehrstuhl für Technische Chemie und Petrolchemie, ITMC, RWTH Aachen University, Worringerweg 1, D-52074, Aachen, Germany.
authors.forename: Walter
authors.initials: W
authors.lastname: Leitner
authors.affiliation: CAT Catalytic Center, RWTH Aachen University, Worringerweg 2, D-52074, Aachen, Germany.
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Müller
mesh_terms: D000535:Aluminum / Q000737:chemistry*; D002254:Carbonates / Q000737:chemistry*; D002384:Catalysis; D056831:Coordination Complexes / Q000737:chemistry; D003500:Cyclization; D004852:Epoxy Compounds / Q000737:chemistry; D005029:Ethylenediamines / Q000737:chemistry*
chemical_list: D002254:Carbonates; D056831:Coordination Complexes; D004852:Epoxy Compounds; D005029:Ethylenediamines; C011452:disalicylaldehyde ethylenediamine; D000535:Aluminum
keywords: aluminum catalyst; carbon dioxide fixation; cyclic carbonate; density functional calculations; reaction pathway