Functionalized-arene ruthenium half-sandwich compounds as enantioselective hydrogen transfer catalysts. Crystal structures of [RuCl{TsNCH(R)CH(R)NH2}(η6-C6H5OCH2CH2OH)] (R=H or Ph)

In an azetropic mixture of formic acid–triethylamine (5:2) the complexes [RuCl(TsDPEN)(η6-C6H5OCH2CH2OH)] (where TsDPEN=(1R,2R))- or (1S,2S)-N-(p-toluenesulfonyl)-1,2-diphenylethylenediamine) effectively catalyse the asymmetric transfer hydrogenation of ketones with complete conversion and good to excellent enantioselectivities, usually 87–95% ee. In contrast, in basic propan-2-ol this catalyst shows a similar stereoselectivity but a reduced activity. It is proposed that this arises because the functionalized side arm competes effectively with propan-2-ol for the free co-ordination site. The crystal structures of [RuCl{(R,R)-TsDPEN)(η6-C6H5OCH2CH2OH)] and [RuCl(NH2CH2CH2NTs)(η6-C6H5OCH2CH2OH)] are reported.