Iridium Models of Rhodium Intermediates in Hydroformylation Catalysis: Isolation and Molecular Structures of Fluxional ae and ee Isomers

We report the synthesis and single-crystal molecular structures of two stereoisomers of trigonal-bipyramidal hydrido dicarbonyl Ir complexes [(L2)­Ir­(H)­(CO)2] with ae (axial–equatorial) and ee (equatorial–equatorial) ligand P coordination and fluxional behavior in solution. L2 is a new chelating bisphosphite with unprecedented high selectivity in Rh-catalyzed bis-hydroformylation of butadiene to adipic aldehyde. These Ir analogues are ideal stabilized structural models for nonseparable ae and ee Rh-hydroformylation resting state isomers [(L2)­Rh­(H)­(CO)2]. With Ir, both stereoisomers with the same ligand could be characterized independently for the first time.