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

Abstract

( S)-2-Pyridyl-imino-[2.2]paracyclophane ligands 1 and 2 were synthesized by a condensation reaction of 2-COR-C 5H 4N ( 1: R = H; 2: R = Me) with enantiopure (−)- S-amino-[2.2]-paracyclophane. The reactions of 1 and 2 with [Ru(η 6-cymene)Cl(μ-Cl)] 2 afforded complexes [Ru(η 6-cymene)Cl(N,N)]X ( 3: N,N = 1; 4: N,N = 2; X - = BPh 4 - , PF 6 - , BF 4 - ) that were completely characterized in solution. For 4PF 6 the solid state structure was determined by X-ray single-crystal diffractometric studies. Two diastereoisomers [( S Ru, S L) and ( R Ru, S L)] 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 ( S Ru, S L) and ( R Ru, S L) 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.