Mechanism of light- and heat-induced rearrangements of complexes of ruthenium(II)

Abstract

Comolexes cis-[Ru(CO)₂L₂X₂](L = ligand with phosphorus or arsenic donor atom. X = haloaen) are converted to their all-trans-isomers by u.v. radiation; the process can be reversed by heating. Similar rearrangements occur with complexes [Ru(CO)₂LL′Cl₂] containing Two different phosphorus ligands L and L′. Studies of the thermal rearrangements of complexes all-trans-[Ru(CO)₂(PMe₂Ph)₂X₂] and all-trans-[Ru(CO)₂(PMePh₂)₂X₂] show that they occur by two competing routes, one direct and one by way of a third isomer, the all-cis-isomer. Evidence from these studies and from the stereochemistry of carbonyl-substitution reactions of the various isomers of [Ru(CO)₂(PMe₂Ph)₂Cl₂] is presented to support mechanisms for the photochemical and thermal isomerizations which involve dissociation of a carbonvl liaand as a first step During the isomerizations, partial loss of CO from solution causes the formation of complexes [{Ru(CO)L₂X₂}₂] as by-products.