A Specific Route to Enantiomerically Pure Asymmetric (η
6
‐Arene)(η
4
‐1,5‐cyclooctadiene)Ru(0) Complexes
摘要:
AbstractChiral or achiral (arene)(COD)Ru complexes can be made by replacing the η6‐ligands of (η4‐1,5‐COD)(η6‐1,3,5‐cyclooctatriene)Ru (1) or (η4‐1,5‐COD)(η6‐naphthalene)Ru (2) by a suitable arene. This well known reaction has been extended to mono‐ and dibromoarenes and we report a novel route to substituted (arene)(COD)Ru species, utilizing (bromoarene)‐(COD)Ru as starting materials. These facilitate a rapid bromine‐lithium exchange reaction with nBuLi at low temperatures and the lithiated species react readily with alkyl chloroformates as electrophiles. By using chiral electrophiles [alkyl = (‐)‐menthyl] enantiomerically pure or diastereomeric complexes containing CO2R* groups are formed, depending on the symmetry of the original complex. A diastereomeric 1:1 mixture was separated by recrystallization. All (arene)‐(COD)Ru complexes tested so far are useful as catalysts for the hydrogenation of simple alkenes at room temperature.