Optically active ortho-metalated half-sandwich ruthenium complexes: Solid-state NMR as a convenient tool to analyze mixtures of diastereomers

Bulk solid samples of various ratios of the cyclometalated arene ruthenium diastereomers (S)(Ru)- and (R)(Ru)-[(eta (6)-C6H6)Ru(C6H4-2-(R)-CH(Me)NMe2) PMe2Ph]+PF6- (3a/3b), of which the configurational stability at the metal c enter has been established by classical solution techniques, have been anal yzed by the C-13 cross-polarization magic angle spinning (CP-MAS) and P-31 MAS NMR. The spectra obtained allowed us to detect both isomers and to esti mate their respective proportions by P-31 spectra. This technique was appli ed to a bulk solid sample of the diastereomers (S)(Ru)- and (R)(Ru)-[(eta ( 6)-C6H6)Ru(C6H4-2-(R)-CH(Me)NMe2)NCMe]+PF6- (1a/1b), which were shown to be configurationally labile by classical solution experiments. Detection of i somer la only in the resulting C-13 CP-MAS NMR spectrum demonstrated that t here has been epimerization of 1b to 1a during crystallization. thus confir ming the configurational lability at the metal center.