Catalytic hydrogen transfer activity of cationic iridium(I) complexes containing alpha-diimines

Cationic [Ir(COD)(LL)](+) species (LL = alpha-diimines derived from biacetyl or glyoxal) in the presence of KOH are active catalysts in the homogeneous hydrogen transfer from isopropanol to acetophenone to give phenylethanol. The most active species is the cation containing biacetyloximehydrazone. alpha,beta-unsaturated ketones are reduced to saturated ketones and alcohols. Cyclohexen-2-one is first selectively reduced at the olefinic double bond by the cation containing biacetyldianyl to give cyclohexanone that is subsequently hydrogenated to the saturated alcohol. This reaction goes through two intermediates in two parallel and finally concurrent pathways; the differential rate equations have been integrated and the simulation of the process agrees reasonably well with experimental measurements. Alcoholic KOH transforms 1-penten-3-one into the corresponding keto-alcohol, 1-pentanol-3-one, the presence of [Ir(COD)(LL)](+) species leads to the subsequent formation of pentan-3-one or pentan-3-ol.