Different coordination modes of dipyridyl ketimine ligands in cationic arene ruthenium complexes

2,2′-Dipyridyl-N-arylimines L (L1 = 2,4,6-trimethyl(di-2-pyridylmethylene)aniline, L2 = 2,6-diisopropyl(di-2-pyridylmethylene)aniline) react with arene ruthenium dichloride dimer in methanol to give cationic arene ruthenium complexes of the general type [(arene)Ru(η2-N,N-L)Cl]+ (arene = C6H6, p-MeC6H4Pri). Two coordination modes of the chelating ligands N,N-L are observed. In the major isomer, the ketimine nitrogen atom and one of the two pyridine nitrogen atoms are coordinated to ruthenium, while in the minor isomer the two pyridine nitrogen atoms coordinate to the metal center. In the case of L1, the minor isomer of the p-cymene ruthenium chloro complex could be isolated as the tetrafluoroborate salt and characterized by single crystal X-ray analysis. The molecular structure of the major isomer was determined by X-ray crystallography in the case of the tetraphenylborate salt of the benzene ruthenium chloro derivative. In both structures, the ruthenium atom shows the expected pseudo-tetrahedral coordination geometry.