Cationic half-sandwich Ru(II) complexes bearing (S)-2-pyridyl-imino-[2.2]paracyclophane ligands: Synthesis, intramolecular and interionic structure

(S)-2-Pyridyl-imino-[2.2]paracyclophane ligands 1 and 2 were synthesized by a condensation reaction of 2-COR-C5H4N (1: R = H; 2: R = Me) with enantiopure (−)-S-amino-[2.2]-paracyclophane. The reactions of 1 and 2 with [Ru(η6-cymene)Cl(μ-Cl)]2 afforded complexes [Ru(η6-cymene)Cl(N,N)]X (3: N,N = 1; 4: N,N = 2; X-=BPh4-,PF6-,BF4-) that were completely characterized in solution. For 4PF6 the solid state structure was determined by X-ray single-crystal diffractometric studies. Two diastereoisomers [(SRu, SL) and (RRu, SL)] were obtained in solution due to the presence of the planar chirality of paracyclophane (L) and the central chirality on ruthenium. 1H-NOESY NMR experiments were used to determine the chirality of the metal center and, consequently, to identify (SRu, SL) and (RRu, SL) diastereoisomers. The cymene orientation, obtained by intramolecular 1H-NOESY NMR investigations, and the relative anion–cation position, determined by interionic 1H-NOESY or 19F,1H-HOESY NMR studies, depended on the nature of the diastereoisomer.

Graphical abstractCationic arene Ru(II) complexes bearing (S)-2-pyridyl-imino-[2.2]paracyclophane ligands, possessing both planar chirality in the ligand and central chirality at the metal, were synthesized and completely characterized in solution (1H-NOESY and 19F,1H-HOESY NMR) and in the solid state (X-Ray) from both intramolecular and interionic points of view.Figure optionsDownload full-size imageDownload as PowerPoint slide