A modular family of phosphine-phosphoramidite ligands and their hydroformylation catalysts : steric tuning impacts upon the coordination geometry of trigonal bipyramidal complexes of type [Rh(H)(CO)2(P^P*)]

Abstract

Four new phosphine-phosphoramidite bidentate ligands have been synthesised and studied in rhodium-catalysed hydroformylation. Variable temperature NMR studies have been used along with HPIR to investigate the coordination mode of the trigonal bipyramidal complexes formed from [Rh(acac)(CO)2], ligand and syngas. It was found that small changes to the ligand structure have a large effect on the geometry of the active catalytic species. The rhodium catalysts of these new ligands were found to give unusually high iso-selectivity in the hydroformylation of propene and 1-octene.