Synthesis of the arene complex [{RuCl2(η6-o-MeC6H4CO2Me)}2] and separation of its diastereomeric (–)(S)-1-phenylethylamine adducts

Abstract

The synthesis of [{RuCl₂(η⁶-o-MeC₆H₄CO₂Me)}₂], (o-MeC₆H₄CO₂Me = methyl o-toluate), from RuCl₃·3H₂O and methyl 1,4-dihydro-o-toluate is reported. This is the first example of an arene–ruthenium complex having planar chirality with respect to the face of the co-ordinated arene. Its reactions with tertiary phosphines and primary amines have been examined. Using optically active amines, the complexes [RuCl₂(η⁶-o-MeC₆H₄CO₂Me) L′][L′=(–)(S)-1-phenylethylamine or (+)-dehydroabietylamine], and [RuCl(η⁶-o-MeC₆H₄CO₂Me)(N–N)]PF₆[N–N =(–)(R,R)-1,2-diphenyl-1,2-diaminoethane], have been obtained as diastereomeric mixtures. The diastereomers of [RuCl₂(η⁶-o-MeC₆H₄CO₂Me){(–)(S)-MeCH(Ph)NH₂}] have been partially separated by fractional crystallisation, the less soluble one being obtained with > 90% enrichment. Their circular dichroism spectra have been compared with those of complexes containing achiral arene–ruthenium moieties.