Quantum yields for loss of a single CO ligand in alkane solutions were determined for the (η3-allyl)­Ru­(CO)3X complexes, where X = Cl, Br, I. The three complexes had similar quantum yields at λexc = 254 nm, while the quantum yields obtained at 313 nm followed a trend of ΦBr > ΦCl > ΦI. A wavelength dependence of the quantum yields in the order Φ254 < Φ313 < Φ334 was observed for the iodo complex. Very low levels of luminescence were observed for the compounds, demonstrating that radiative decay of the excited states was not competitive with nonradiative processes, including photochemical reactions. Excited states were assigned as MLCT or LF on the basis of solvatochromism and DFT studies.

Solution phase photochemical experiments on (η4-diene)­Ru­(CO)3 complexes (diene = butadiene, isoprene, 1,3-cyclohexadiene, or cyclobutadiene) demonstrated loss of both diene and CO, making them attractive precursors for photoassisted chemical vapor deposition of ruthenium. Pathways including loss of one CO ligand, loss of diene, loss of two CO ligands, and loss of CO plus diene were observed. Quantum yields for loss of a single CO or diene ligand as the primary photoprocess were determined for the (η4-diene)­Ru­(CO)3 complexes and were found to be dependent on the structure of the diene. Subsequent ligand loss was determined to occur from secondary photolysis. Very little luminescence was observed for the compounds, demonstrating that radiative decay of the excited states was not competitive with photochemical ligand loss. Exhaustive photolysis experiments confirmed that all of the dienes, except for cyclobutadiene, were photolytically labile. In the absence of phosphite, the (η4-diene)­Ru­(CO)3 complexes showed evidence for formation of colloidal Ru species following irradiation in hydrocarbon solutions.