title: Study of the ligand substitution reactions of cis,cis-[(bpy)(2)(L)RuORu(L')(bpy)(2)](n+) (L, L' = H(2)O, OH(-), NH(3)) using electrospray ionization mass spectrometry and (1)H NMR.
abstract: We have successfully applied electrospray ionization mass spectrometry (ESI-MS) and (1)H NMR analyses to study ligand substitution reactions of mu-oxo ruthenium bipyridine dimers cis,cis-[(bpy)(2)(L)RuORu(L')(bpy)(2)](n+) (bpy = 2,2'-bipyridine; L and L' = NH(3), H(2)O, and HO(-)) with solvent molecules, that is, acetonitrile, methanol, and acetone. The results clearly show that the ammine ligand is very stable and was not substituted by any solvents, while the aqua ligand was rapidly substituted by all the solvents. In acetonitrile and acetone solutions, the substitution reaction of the aqua ligand(s) competed with a deprotonation reaction from the ligand. The hydroxyl ligand was not substituted by acetonitrile or acetone, but it exchanged slowly with CH(3)O(-) in methanol. The substitution reaction of the aqua ligands in [(bpy)(2)(H(2)O)Ru(III)ORu(III)(H(2)O)(bpy)(2)](4+) was more rapid than that of the hydroxyl ligand in [(bpy)(2)(H(2)O)Ru(III)ORu(IV)(OH)(bpy)(2)](4+). In methanol, slow reduction of Ru(III) to Ru(II) was observed in all the mu-oxo dimers, and the Ru-O-Ru bridge was then cleaved to give mononuclear Ru(II) complexes.
authors.affiliation: Department of Applied Chemistry, Kansai University, Suita, Osaka, Japan. arak@ipcku.kansai-u.ac.jp
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Arakawa
authors.forename: Naoko
authors.initials: N
authors.lastname: Kubota
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Fukuo
authors.forename: Osamu
authors.initials: O
authors.lastname: Ishitani
authors.forename: Emiko
authors.initials: E
authors.lastname: Ando