Synthesis, spectroscopic and structural characterization and solution stability of ruthenium sandwich complexes containing 1,8-naphthalimide ligands

Abstract

Two different N-substituted naphthalimide ligands 1 (bearing a phenyl on the imide nitrogen) and 2 (bearing a benzyl on the imide nitrogen) have been synthesized and reacted with the cationic organometallic fragment [Cp*Ru(ACN)3]PF6. Ligand 1 brings to the formation of a sandwich complex (3Naph) where Ru is positioned on the naphthalene platform, while the N-imide phenyl substituent is not involved in coordination. This has been proven by single-crystal X-ray diffraction analysis conducted on crystals of 3Naph, revealing the first sandwich complex structurally characterized containing a naphthaleneimide ligand η6-coordinated to a metal. Ligand 2 shows instead a different behavior, leading to the formation of two isomeric complexes (4Naph and 4Bz), where Ru is placed on the naphthalene platform and on the N-imide benzyl substituent, in a rough 1:1 ratio. Complex 3Naph results very labile in coordinating solvents, such as acetonitrile, where it undergoes a fast and quantitative ligand solvolysis, with formation of free 1 and [Cp*Ru(ACN)3]PF6. In the cases of complexes 4, only complex 4Naph undergoes a fast and quantitative ligand solvolysis once dissolved in acetonitrile, whereas complex 4Bz results more stable.