Bimetallic hydroformylation: a zwitterionic Rh–IRhI tetraphosphine ligand-based bimetallic complex exhibiting facile CO addition and phosphine ligand rearrangement equilibrium

Abstract

The X-ray structure of an unsymmetrical tetraphosphine bridged zwitterionic Rh^–IRh^I dinuclear tetracarbonyl complex is reported along with the facile CO addition equilibrium to form an Rh⁰ tetraphosphine pentacarbonyl bimetallic species; both of these are poor hydroformylation catalysts due to the relatively high electron density on the rhodium centres, in marked contast to a dicationic bimetallic Rh^II complex based on the same tetraphosphine ligand that is a highly active and regioselective hydroformylation catalyst.