ABSTRACT
Herein, we report the preparation, characterisation and catalytic applications of air-stable Fe(iii)-acetate complexes consisting of salan, salen and salalen ligand frameworks. Owing to the simple synthetic protocol employed, a wide range of complexes have been prepared and structure-activity-relationships investigated. X-ray diffraction confirmed the solid-state structures for eight of the complexes. These represent the first Fe(iii)-acetate complexes applied for the selective coupling of CO2/epoxide and lactide polymerisation. The coupling of CO2 and challenging cyclohexene oxide substrate was performed under mild, solvent-free conditions (80 °C, 10 bar CO2) to selectively form the cis-cyclohexene carbonate as the exclusive product (selectivity >99%) with a metal loading of 0.08 mol%. A reduced aminopiperidine ligand backbone was found as the most active catalyst, and after investigating four co-catalysts, showed high functional group tolerance and robustness when applied to a broad, commercially available, terminal epoxide substrate scope with high conversions observed. The ring-opening polymerisation of rac-lactide was achieved using the Fe(iii)OAc complexes using triethylamine and benzyl alcohol for initiation, interestingly isoselectivity was observed in some cases.
ABSTRACT
Main-group metals are inherently labile, hindering their use in catalysis. We exploit this lability in the synthesis of isocyanurates. For the first time we report a highly active catalyst that trimerizes alkyl, allyl and aryl isocyanates, and di-isocyanates, with low catalyst loadings under mild conditions, using a hemi-labile aluminium-pyridyl-bis(iminophenolate) complex.
