Cationic half-sandwich quinolinophaneoxazolinebased (η~6-p-cymene)ruthenium(II) complexes exhibiting different chirality types: synthesis and structural determination by complementary spectroscopic methods

摘要

Novel, optically pure 2-{4-methyl[2]paracyclo[2](5,8)quinolinophan-2-yl}-4-aryl/alkyloxazolines (QUIPHANOX) exhibiting both planar and central chirality have been prepared by reacting (R_p)- and (S_p)- 2-cyano-4-methyl[2]paracyclo[2](5,8)quinolinophane with 2-aryl/alkyl-2-aminoethanols. The reaction of each of the above N,N-ligands with [Ru(η~6-p-cymene)Cl_2]2 in methanol, in the presence of either NH_4PF_6 or NaBPh_4, gave the corresponding half-sandwich [(η~6-p-cymene)Ru(QUIPHANOX)Cl]~+Y~-, (Y~- = PF_6~-, BPh_4~-) as stable complex salts exhibiting planar and carbon- and metal-centered chirality. The unknown absolute configuration (AC) at the metal was determined by ~~1H NMR and by theoretical calculations of electronic circular dichroism (ECD) spectra and subsequently confirmed by crystallographic X-ray analysis. (R_p) and (S_p)-ligands afforded (R_(Ru))- and (S_(Ru))-configured complexes, respectively, independent of the AC at the chiral carbon of the oxazoline moiety.