(Arene)ruthenium Complexes with Bis(oxazolines): Synthesis and Applications as Asymmetric Catalysts for Diels−Alder Reactions

Reaction of the dimers [RuCl2(arene)]2 (arene = benzene, p-cymene, mesitylene) with bis(oxazolines) (N-N = bis(2-oxazoline) (box), 2,2-bis(2-oxazolinyl)propane (bop), 1,2-bis(2-oxazolinyl)benzene (benbox)) in the presence of NaSbF6 gives the complexes [RuCl(N-N)(arene)][SbF6] (1−8), which have been fully characterized. Treatment of these cations with AgSbF6 generates dications which in some cases are enantioselective catalysts for Diels−Alder reaction of methacrolein and cyclopentadiene. Two complexes, [RuCl(iPr-benbox)(p-cymene)][SbF6] (5) and [Ru(OH2)(iPr-bop)(mes)][SbF6]2 (10; mes = mesitylene), have been characterized by X-ray crystallography.