Photochemistry of (η4-diene)Ru(CO)3Complexes as PrecursorCandidates for Photoassisted Chemical Vapor Deposition

Solution phase photochemical experiments on (eta 4-diene)-Ru(CO)3complexes (diene = butadiene, isoprene, 1,3-cyclohexadiene, orcyclobutadiene) demonstrated loss of both diene and CO, making themattractive precursors for photoassisted chemical vapor deposition ofruthenium. Pathways including loss of one CO ligand, loss of diene, lossof two CO ligands, and loss of CO plus diene were observed. Quantumyields for loss of a single CO or diene ligand as the primary photoprocesswere determined for the (eta 4-diene)Ru(CO)3complexes and were foundto be dependent on the structure of the diene. Subsequent ligand loss wasdetermined to occur from secondary photolysis. Very little luminescencewas observed for the compounds, demonstrating that radiative decay ofthe excited states was not competitive with photochemical ligand loss.Exhaustive photolysis experiments confirmed that all of the dienes, exceptfor cyclobutadiene, were photolytically labile. In the absence of phosphite, the (eta 4-diene)Ru(CO)3complexes showed evidence forformation of colloidal Ru species following irradiation in hydrocarbon solutions.

Automated summary

Solution phase photochemical experiments showed that (eta 4-diene)-Ru(CO)3 complexes can be used as precursors for photoassisted chemical vapor deposition of ruthenium by losing both diene and CO ligands. The quantum yields of ligand loss were found to depend on the structure of the diene, and subsequent ligand loss was determined to occur from secondary photolysis. The compounds exhibited little luminescence, indicating that radiative decay of the excited states was not competitive with photochemical ligand loss. Additionally, the formation of colloidal Ru species was observed after irradiation in hydrocarbon solutions in the absence of phosphite.