A SPECIFIC ROUTE TO ENANTIOMERICALLY PURE ASYMMETRIC (ETA(6)-ARENE)(ETA(4)-1,5-CYCLOOCTADIENE)RU(0) COMPLEXES

Chiral or achiral (arene)(COD)Ru complexes can be made by replacing th e eta(6)-ligands of (eta(4)-1,5-COD)(eta(6)-1,3,5-cyclooctatriene)Ru ( 1) or (eta(4)-1,5-COD)(eta(6)-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, uti lizing (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 chloro-formates as electrophiles. By using chiral electrophiles [alkyl = (-)-menthyl] en antiomerically pure or diastereomeric complexes containing CO(2)R gro ups are formed, depending on the symmetry of the original complex. A d iastereomeric 1:1 mixture was separated by recrystallization. All (are ne)-(COD)Ru complexes tested so far are useful as catalysts for the hy drogenation of simple alkenes at room temperature.