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

Reaction of the dimers [RuCl 2 (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 NaSbF 6 gives the complexes [RuCl(N-N)(arene)][SbF 6 ] ( 1 − 8 ), which have been fully characterized. Treatment of these cations with AgSbF 6 generates dications which in some cases are enantioselective catalysts for Diels−Alder reaction of methacrolein and cyclopentadiene. Two complexes, [RuCl( i Pr-benbox)( p -cymene)][SbF 6 ] ( 5 ) and [Ru(OH 2 )( i Pr-bop)(mes)][SbF 6 ] 2 ( 10; mes = mesitylene), have been characterized by X-ray crystallography.