A BIMETALLIC HYDROFORMYLATION CATALYST - HIGH REGIOSELECTIVITY AND REACTIVITY THROUGH HOMOBIMETALLIC COOPERATIVITY

The racemic and meso diastereomers of an electron-rich binucleating te traphosphine ligand have been used to prepare homobimetallic rhodium n orbornadiene complexes. The racemic bimetallic Rh complex is an excell ent hydroformylation catalyst for 1-alkenes, giving both a high rate o f reaction and high regioselectivity for linear aldehydes, whereas the meso complex is considerably slower and less selective. A mechanism i nvolving bimetallic cooperativity between the two rhodium centers in t he form of an intramolecular hydride transfer is proposed. Mono- and b imetallic model complexes in which the possibility for bimetallic coop erativity has been reduced or eliminated are very poor catalysts.