Substitutional photochemistry of sandwich and half-sandwich complexes of ruthenium(II)

Ruthenium(II) sandwich complexes of the type Ru(eta(6)-arene)(2)(2+) (arene is benzene or 1,3,5-trimethylbenzene) undergo photosubstitution of one arene ring by solvent (S) to yield Ru(eta(6)-arene)(S)(3)(2+). Reaction occurs from the lowest ligand field triplet state of the complex with a quantum efficiency that decreases with increasing methylation of the arene. Half-sandwich complexes of general formula Ru(eta(6)-arene)(L)(3)(2+) (L is CH3CN or NH3) undergo competitive photosubstitution of arene and L by solvent. The relative importance of these pathways depends upon a number of factors, including excitation wavelength, solvent, and the nature of L. Mechanisms for these photoreactions are discussed and comparisons to earlier studies are presented. (C) 1998 Elsevier Science S.A. All rights reserved.