BIMETALLIC HYDROFORMYLATION - A ZWITTERIONIC RH-IRHI TETRAPHOSPHINE LIGAND-BASED BIMETALLIC COMPLEX EXHIBITING FACILE CO ADDITION AND PHOSPHINE LIGAND REARRANGEMENT EQUILIBRIUM

The X-ray structure of an unsymmetrical tetraphosphine bridged zwitter ionic (RhRhI)-Rh--I dinuclear tetracarbonyl complex is reported along with the facile CO addition equilibrium to form an Rh-0 tetraphosphine pentacarbonyl bimetallic species; both of these are poor hydroformyla tion catalysts due to the relatively high electron density on the rhod ium centres, in marked contrast to a dicationic bimetallic Rh-II compl ex based on the same tetraphosphine ligand that is a highly active and regioselective hydroformylation catalyst.