Synthesis and Properties of Planar-Chiral (<i>η</i>6-Benzene)(<i>η</i>5-cyclopentadienyl)ruthenium(II) Complexes in an Optically Pure Form

Abstract

Abstract Planar-chiral cyclopentadienylruthenium complexes [Ru(η5-1-CO2R*-2-Me-4-R1C5H2)(η6-C6H6)][X] (4 and 8) (R* = (l)- or (d)-menthyl; R1 = Me, Ph, t-Bu, 2-Naphthyl, or 4-BrC6H4; X = PF6 or BPh4) were synthesized in a diastereomerically pure form. The absolute configuration of 8b and 4c (R1 = Ph, t-Bu) were determined by an X-ray crystallographic analysis and those of the others were assigned on the basis of their optical properties including their CD spectra. Enantiopure complexes (SC1)-[Ru(η5-1-CONHBut-2-Me-4-R1C5H2)(η6-C6H6)][PF6] 9 and -[Ru(η5-1-CONHBut-2-Me-4-R1C5H2)(η6-C6H6)] [BPh4] 10, and (RC1)-9 and -10 were prepared from direct hydrolysis of diastereomeric complexes, followed by the reaction of amines. Replacement reactions of the bromo group in 9e (R1 = 4-BrC6H4) gave alkyl, phenyl, and ethynyl derivatives. Complexes [Ru(η5-1-CO2Et-2-Me-4-R1C5H2)(η6-C6H6)][PF6] 6 were also transformed to planar-chiral [Ru(η5-1-CO2Et-2-Me-4-R1C5H2)(CH3CN)3][X], which underwent ligand exchange reactions to afford carbonyl, phosphine, and π-arene complexes.