A Cyclometalated Ruthenium-NHC Precatalyst for the Asymmetric Hydrogenation of (Hetero)arenes and Its Activation Pathway

This study describes the structural
investigation of a highly versatile
ruthenium-NHC (N-heterocyclic carbene) catalyst complex, which has
been established for the asymmetric hydrogenation of various aromatic
compounds. A complex containing an unusual doubly deprotonated NHC
ligand was isolated and identified as the precatalyst to this complex.
When its subsequent reactivity was monitored, two additional precatalysts,
featuring partially hydrogenated naphthyl substituents, were characterized
spectroscopically. Ligand hydrogenation appears to be a key activation
process en route to the active catalyst.